Breast imaging with ultra-low field MRI

Breast imaging with ultra-low field MRI | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Article Breast imaging with ultra-low field MRI Sheng Shen, Neha Koonjoo, Friderike K. Longarino, Leslie R. Lamb, and 8 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6882799/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 19 Feb, 2026 Read the published version in Scientific Reports → Version 1 posted 10 You are reading this latest preprint version Abstract Breast cancer screening is essential for reducing mortality, yet current modalities face significant barriers, including high costs, limited accessibly, and reliance on ionizing radiation, which leads many women to forego regular screenings. Magnetic resonance imaging (MRI) offers a radiation-free alternative, but its adoption for screening is constrained by cost, availability, and the need for IV contrast administration. In this study, we demonstrate the feasibility of ultra-low field (ULF) unilateral breast MRI for screening applications. ULF MRI was performed on 11 healthy women in a prone position. Three breast radiologists could reliably delineate breast outlines and distinguish fibroglandular tissue (FGT) from adipose tissue. Tissue patterns (fatty, scattered, heterogeneous, and extreme FGT) were consistently identified. In two patients with prior breast cancer, ULF MRI effectively eliminated magnetic susceptibility artifacts from surgical biopsy clips and in one of these patients revealed post-surgical changes following lumpectomy. Additionally, a benign mass was detected in another patient. These findings highlight ULF breast MRI as a potential low-cost, accessible, and contrast-free alternative for breast cancer screening, with the promise of expanding early detection to underserved populations globally. Physical sciences/Engineering/Biomedical engineering Health sciences/Health care/Medical imaging/Magnetic resonance imaging Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Introduction In 2021, over two billion women worldwide were over the age of 40 1,2 , and each of them face the risk of developing breast cancer. This disease will affect approximately one in eight women during their lifetime 3 , with 85% of cases occurring in those without any family history of the disease 4 . Additionally, early-onset breast cancer tends to be more aggressive and has a poorer prognosis 5 . However, current screening guidelines are insufficient in this population 6 , 7 , highlighting the need for continued advancements in early detection strategies. Currently, mammography is the most widely used imaging tool for breast cancer screening due to its accessibility and cost-effectiveness. However, it has notable limitations: it involves ionizing radiation, causes discomfort due to breast compression, has a false positive rate ranging from 10.2–14.4% 8–10 , and misses 1–35% of breast cancers 11 – 17 . Consequently, in the United States as of 2015, only 65.3% of women over 40 had a screening mammogram in the previous two years 18 . Given that more than half of the global population should undergo breast cancer screening multiple times in their lives 19 , there is an urgent need for a more accurate and patient-friendly screening tool. Currently available MRI-based methods overcome some of these limitations 20 , particularly in high-risk groups 21 – 23 . This is because differences in soft tissues can be visualized without obfuscations from dense tissue, and MRI screening has low false-negative rates 24 , 25 . MRI can detect invasive carcinomas, distinguishing between malignant and benign lesions using T1 and T2-weighted imaging with injected contrast agent enhancement 26 . Additionally, apparent diffusion coefficient (ADC) can be used to differentiate lesions 27 and assess response to treatment 28 . However, clinical breast screening exams on traditional MRI scanners require the patient to endure a constricted setting in addition to receiving IV contrast administration. MRI as a screening modality is currently underutilized in high-risk women (defined as a lifetime risk > 20%) 29 . While fast MRI protocols enable screening in less than 10 minutes 30 , the high cost and limited number of scanners (< 38 scanners per million people in the US) prohibit their use as a primary screening tool for breast cancer. Compared to clinical MRI systems operating at 1.5 T or 3 T, low- (< 100 mT) and ultra-low field (ULF, < 10 mT) MRI systems offer a significantly lower cost and accessible alternative with far less strict installation requirements. This accessibility opens the door to broader use, particularly in settings where traditional MRI systems are unavailable and impractical including in low- and middle-income countries globally 31 . Additionally low and ultra-low field MRI systems do not require IV contrast administration. Low-field MRI neuroimaging systems operating at 64 mT have already been successfully implemented in clinical settings for stroke detection at the patient’s bedside 32 – 34 . These systems are portable, safe, and simple to operate, and do not require an MRI technician or special magnetic- or RF-shielded room 35 , 36 . Although operation at lower magnetic field typically yields images with reduced signal-to-noise ratio (SNR), the clinical efficacy of low-field MRI for neuroimaging has been clearly demonstrated 32 , 34 , 37 . Moreover, laboratory developments have shown the potential for low-field MRI in extremity 38 and whole-body imaging 39 , though applications to breast imaging have yet to be realized. Given the recent clinical successes of low field MRI for neuroimaging, we propose that ULF MRI could potentially achieve sufficient SNR for effective breast imaging. Historically, Nuclear Magnetic Resonance (NMR)-based methods have shown promise in breast cancer assessment. From 1975–1982, T1 and T2 relaxation times of breast tissues were measured at 0.71 T 40 yielding encouraging results. Subsequent studies measured the T1 of mastectomy samples at 0.09 T and 0.35 T 41 , 42 , and in vivo whole-breast imaging was attempted at 45 mT. Although these early efforts were hampered by excessively long exam times, they supported the fundamental findings of the NMR studies 43 . Additional research using NMR dispersion (NMRD) measurements revealed that the T1 relaxation times of cancerous ex vivo breast tissues differ significantly from those of healthy fibroglandular and adipose tissues in the low- and ultra-low field regimes 40 , 44 , 45 . These differences in T1 relaxation times form the basis of our current research. If we can achieve sufficient SNR within a reasonable exam duration, ULF breast MRI could emerge as a cost-effective alternative for breast imaging, offering the advantages of contrast-free, multi-slice soft tissue visualization over the X-ray projection-based method used in mammography. In this study, we present our preliminary evaluation of breast imaging using ULF MRI, showcasing its potential as a transformative tool in breast cancer screening. Utilizing a laboratory-based ULF MRI system operating at 6.5 mT with a unilateral conical RF coil, we imaged the left breasts of 11 healthy women, one right and one left breast of two patients with a history of breast cancer, and the left breast of one patient with a known benign mass. In healthy participants, the ULF MR images of the whole breast revealed essential breast features, including type of fibroglandular tissue, breast outline, nipple areolar complex, and chest wall. Additionally, for three healthy participants the 3D ULF MRI scans are compared to their X-ray mammogram. For both patients with a history of breast cancer, the artifacts typically generated by surgical clips and post-surgical changes were evaluated. And lastly, the feasibility of detecting a benign mass at ULF was also investigated. Results Imaging system Imaging was performed on a custom-built electromagnet-based MRI scanner shown in Fig. 1 and modified for breast imaging from its previously described configuration for neuroimaging 46 . Figure 1 shows the imaging bed and dedicated RF coil designed to image a single breast. The breast and breast RF coil are placed at the isocenter of the scanner (Fig. 1D). A close-fitting conical breast coil was designed, the RF magnetic field generated by this coil simulated, and the resultant field map is shown in Fig. 1E. The field homogeneity within the breast RF coil was quantified, revealing an inhomogeneity of ±60% over the breast volume region, and a magnetic field fall-off 3 cm inside the chest wall of 30%. To evaluate the sensitivity of the coil, a homogeneous flexible phantom filled with deionized water was positioned inside the breast RF coil and scanned (Fig. 1F). The phantom imaging result (Fig. 1G) reflects the sensitivity distribution across the RF coil, demonstrating high sensitivity within the coil and a marked decrease in sensitivity towards the opening of the RF coil. Participant characteristics and imaging protocol ULF MRI was used to image the left breast of 11 healthy women (mean age, 35 years ± 13 years). Additionally, three patients participated: a 51-year-old patient with a history of invasive ductal carcinoma (grade 1) and papillary carcinoma (grade 1), a 58-year-old patient with a history of invasive lobular carcinoma (grade 3), and a 48-year-old patient with a known benign mass. All women completed the study. A 3D balanced SSFP (bSSFP) sequence was used with a constant voxel size of 3 mm × 3 mm × 8 mm, and the resulting total scan time was 21 minutes 36 seconds for all the healthy participants. For the three cases with known pathology, a higher spatial resolution was used depending on the breast size. For larger breast size (n=1), a 30-minute scan with a voxel size of 2 mm × 2 mm × 6 mm was used, and for smaller breast size (n=2), a 45-minute scan with a voxel size of 2 mm × 2 mm × 4 mm was used. No data-driven Artificial Intelligence (AI) or other machine learning-based methods were used in the image acquisition or reconstruction. The MR sequence and positioning were well tolerated. None of the images were degraded by patient motion. It is noteworthy that none of the participants experienced discomfort during the exam, and the breast fit naturally in the conical-shaped RF coil without compression. ULF MRI breast imaging findings Image sets of the entire left breast for three representative subjects with different breast tissue patterns are shown in Fig. 2 – 4. For these three representative subjects, the following features were labeled by a breast radiologist: visibility of the breast outline or skin, NAC, FGT, and chest wall. The bSSFP pulse sequence has a mixed contrast that depends on the ratio of T2/T1, such that fat tissue appears bright and fibroglandular tissue appears dark. Breast images from all 11 participants were evaluated by three independent board-certified breast radiologists for the purpose of categorizing breast density and assessing the visibility of essential breast tissues, which include the type of fibroglandular tissue, the breast outline, the nipple areolar complex, and the chest wall. Individual image scores are reported in Table 1. Breast tissue pattern was assessed using fatty, scattered FGT, heterogeneous FGT, and extreme FGT. Inter-reader reliability of breast tissue pattern was determined using Fleiss' kappa, which resulted in a kappa value of 0.73 (95% confidence interval: 0.72 to 0.74, p<0.001), indicating substantial agreement among the readers. Visibility of the following features in the breast was scored using a 5-point Likert scale (1 – not at all visible to 5 – clearly visible and very sharp): breast outline, fibroglandular tissue (FGT) compared to intramammary adipose tissue, demarcation of the nipple areolar complex (NAC), and the chest wall, defined as visualization of the pectoralis muscle. The limited data set from this pilot study did not allow for proper training of the readers, and given the novelty of the images, the readers were not well “calibrated” to each other. For example, when evaluating the visibility of the breast outline, we find the readers were internally consistent: each reader scores all images with the same visibility (with the exception of a single case for reader 1 that received a higher score). However, each reader has assigned a different visibility score from the other readers. As a result, a binary rating system was adopted from the 5-point scale with a score of 1 remaining not at all visible and scores 2-5 as visible. Fleiss’ kappa was also used to measure the agreement regarding the visibility of essential breast tissues which included the type of fibroglandular tissue, the breast outline, nipple areolar complex (NAC), and the chest wall. In this binary framework, consensus on the visibility of the breast outline and fibroglandular (FGT) tissue was consistent (kappa = 1), whereas the NAC and chest wall exhibited kappa values of 0.54 (95% confidence interval: 0.58 to 0.60, p<0.001) and 0.27 (95% confidence interval: 0.26 to 0.28, p<0.2), respectively. ULF MRI acquisition and X-ray mammography of healthy participants Three of the 11 healthy participants had a bilateral screening mammogram within 8 months of their participation in the ULF MRI study. These mammograms were labelled by a breast radiologist with 13 years of experience. All three participants have scattered fibroglandular tissue, and Fig 5 shows a representative case with the different breast features identified on both the ULF MRI and the mammogram. The other two cases are reported in Figs S1 and S2 in the supplemental material. Comparison to mammography confirms that the ULF MRI reliably shows the fibroglandular tissue. Patient scanning at ULF MRI Imaging was also performed in three patients with a history of breast disease: two with a history of breast cancer and one with a palpable, known cystic mass. For these studies, the spatial resolution was increased in all three dimensions, and to maintain SNR, signal averaging was increased resulting in a longer scan time. Figure 6 shows the images of a patient with a history of invasive ductal carcinoma (grade 1) and papillary carcinoma (grade 1) in the subareolar region of the right breast diagnosed two years prior to this study. The patient received a localized lumpectomy prior to tamoxifen treatment. The ULF MRI showed all breast features including NAC, skin, FGT, retromammary fat, and chest wall. ULF MRI also showed the post-surgical changes at the site of the lumpectomy with no susceptibility artifacts from the surgical clips. The X-ray mammogram and the 1.5 T clinical breast MRI also showed the different breast features. The mammogram clearly showed the surgical clips, and the susceptibility artifacts from the surgical clips are visible on the 1.5 T MRI scan. Figure 7 shows representative slices of a patient with a history of invasive lobular carcinoma (grade 3) in the left breast. The patient received a lumpectomy three years prior to this study. The surgical clips were not visible on ULF images due to their small size (length 4 mm) and due to the absence of susceptibility artifacts at lower magnetic field strengths. The surgical clips are visible on X-ray mammogram, and at 1.5 T MRI, the susceptibility artifacts indirectly show the location of the surgical clips. Figure 8 shows images from a patient with a palpable mass that was imaged with ULF MRI; the patient had a known cystic mass on X-ray mammogram and on the targeted ultrasound exam. On ULF MRI, the cystic mass is clearly visible on five slices at approximately 1 cm above the nipple on the medial side of the left breast. The location of the mass was confirmed by a breast radiologist. Using ULF MRI, the size of the mass was evaluated as 33 mm ´ 20 mm ´ 18 mm, which agrees with the reported values assessed on the ultrasound exam of 35 mm ´ 26 mm ´ 16 mm. The volume of the mass estimated using the 3D ULF MRI was 8.16 cm 3 . Discussion In this preliminary study, we successfully performed in vivo MR breast imaging at 6.5 mT on healthy participants and on patients with either a history of breast cancer or a benign mass. Essential breast features were identified such as breast outline or skin, FGT, NAC, and chest wall. We included 11 participants with a range of breast sizes, and images were acquired using a single bSSFP sequence with an imaging duration of approximately 21 minutes. The three clinical case studies included two patients with a history of breast cancer who have both undergone lumpectomy and one patient with a benign mass. All of the ULF MRI scans were acquired at 6.5 mT without the use of exogeneous IV contrast agents or the use of machine learning for image acquisition and reconstruction. These promising results motivate us to further develop ULF MRI for breast imaging. Globally, one-eighth of the population, or 2.2 billion women over age 40, are recommended to undergo regular breast cancer screenings 47 . This translates to approximately 500 million screening exams needed every year, vastly surpassing the combined total of head injuries, strokes and brain tumors, which are estimated as 85 million annually 48 – 51 . The potential impact of ULF MRI technology on breast cancer screening is enormous, offering a revolutionary, cost-effective solution for early detection and improved healthcare access worldwide. MRI at low- and ultra-low magnetic fields is challenging due to inherently low Boltzmann polarization and consequently low signal. Two additional consequences of MRI physics at ultra-low magnetic field are relevant to this work. First, as magnetic field decreases, tissue T1 relaxation times generally decrease, while T2 relaxation times are generally constant across fields 44 , 52 . Second, the magnetic susceptibility artifacts are significantly reduced at ULF. We leverage both of these aspects to our advantage at 6.5 mT, where the efficiency of bSSFP in this regime is maximal 46 and enables banding-free imaging over large fields of view. In this study, the image SNR was sufficient to visualize key breast tissues. The three expert readers had substantial agreement in their evaluations of breast tissue patterns and key breast tissues. However, there were notable discrepancies: Reader 2’s scores were, on average, 33% lower than those of Reader 1 (paired t-test, p < 0.001) and 28% lower than Reader 3 (paired t-test, p < 0.001). Additionally, Reader 3’s scores were 7.01% higher than those of Reader 1 (paired t-test, p < 0.03). There was also some disagreement regarding the visibility of the NAC and chest wall. These discrepancies can be attributed to two main factors: lack of training and experience with ULF MRI. The limited dataset prevented proper training, as the evaluation criteria were only discussed rather than practiced. Furthermore, the readers had no prior experience with ULF MRI images, leading to a lack of calibration across the readers. In contrast, when evaluating clinical breast MRI scans, the readers are implicitly calibrated, having each examined numerous scans over extensive periods (13 years, 3 years and 9 years, respectively). This experience gap underscores the need for dedicated training and calibration when introducing new imaging technologies like ULF MRI to ensure accurate and consistent evaluations. The visibility of the NAC and chest wall was inconsistent across scans. The absence of the NAC in certain images may be attributed to slice thickness, breast positioning, or natural anatomical variations such as flat or inverted nipples. The chest wall was not always visible, primarily in participants with a larger breast. This is a limitation of the RF coil design: with an imaging depth of approximately 3 cm from the coil’s end plate, the chest wall was not fully captured in individuals with larger breast sizes. This design constraint highlights a significant area for improvement in coil development to enhance imaging coverage for diverse breast sizes. For three of the healthy participants, recent mammograms were available. The comparison between ULF MRI scan and its corresponding mammogram shows that ULF MRI can determine fibroglandular tissue pattern and all four essential breast features. In the future, ULF MRI should be compared with mammography of participants with different breast tissue pattern (e.g., dense fibroglandular tissue). Post-surgical changes were observable on ULF MRI scans for the patient diagnosed two years prior to this study with invasive ductal carcinoma (grade 1) and papillary carcinoma (grade 1) in the subareolar region of the right breast, and unlike at 1.5 T or 3 T, these changes were not obscured by susceptibility artifacts from surgical clips. In contrast, the location of surgical clips were not observed for the patient diagnosed three years prior to this study with invasive lobular carcinoma (grade 3). Typically, surgical clips are placed during biopsy or surgical procedures to serve as localization markers. On high-field breast MRI (1.5 T or 3 T), these clips generate susceptibility artifacts visible as dark patterns larger than the clips, which aid in locating the clips but also obscure the surrounding breast tissue. In ULF MRI, susceptibility artifacts from surgical clips are absent, allowing for unobstructed imaging of breast tissue. However, this lack of artifacts also makes it more challenging to locate the surgical clips themselves. To date, the scientific evidence on whether these susceptibility-related image artifacts in breast MRI may lead to misinterpretations or the inability to detect the respective lesion is very limited 53 , 54 . However, if low field breast MRI becomes a screening technique, the absence or reduced susceptibility artifacts caused by metallic marking clips will be crucial for early cancer detection for a group of patients who have retained tissue marker clips or foreign bodies within the breast tissue. At ULF, the cystic mass that was already proven on ultrasound was easily detected on multiple slices of the MR image. The bright MRI signal on the bSSFP scan and the dark signal on ultrasound indicate that the benign mass is fluid-filled. In contrast, X-ray mammography cannot differentiate between tissue types and is limited to detecting density variations. In ultra-low magnetic field imaging, a bSSFP sequence produces bright signals for both fatty tissues and fluids, which is a limitation of the current approach. This overlap prevents distinction between fat and fluid without additional imaging techniques. Our current methods face several limitations. Eight out of eleven healthy subjects did not have a mammogram or clinical breast MRI for comparison. This is because those participants belonged to a younger age group who have not yet undergone breast screening. Hence, to facilitate evaluation, our three breast radiologists leveraged their expertise in interpreting clinical breast MRI scans. Nevertheless, this exploratory phase provided valuable insights into the potential of ULF imaging, paving the way for future refinement and standardization. Besides the issue of incomplete visualization of the chest wall, our preliminary study did not image the axilla, a crucial area for detecting breast cancers and nodal disease. Furthermore, a lower spatial resolution of 3 mm × 3 mm × 8 mm was applied to the 11 healthy participants to demonstrate the potential of ultra-low field breast MRI to clinicians while ensuring a reasonable scan time. The image resolution used for scanning the 11 healthy participants does not meet clinical standards for breast cancer screening, which require a spatial resolution of approximately 2 mm × 2 mm × 5 mm to effectively detect small tumors. Although higher spatial resolution was performed in three patients, this came at the cost of longer scan times. Notably, the 3D ULF MRI images allowed precise measurement of the cyst volume in the left breast of the patient with a benign mass. Ideally, both breasts and axilla should be imaged simultaneously at this target resolution within a ten-minute scan. To address these issues, developing RF coils capable of imaging both breasts simultaneously and including the axilla and chest wall in the field of view is essential. Our cost-effective coil design, which can be tailored to various sizes, aims to enhance the filling factor and thereby improve the SNR for each subject 55 . This approach could significantly reduce total exam time and bring us closer to meeting the clinical resolution requirements. The work presented here was acquired on our 6.5 mT ULF MRI system which is a configurable test bed system developed in our laboratory to perform preliminary research and optimization of breast cancer imaging techniques. For clinical applicability, enhancing the SNR is crucial, as it can be used to attain higher resolution, shorter scan time, or both. While our current results are based on a 6.5 mT system, operating at even moderately higher magnetic fields (B 0 ) would significantly improve performance. For instance, increasing the magnetic field to a nominal 20 mT would boost the SNR by a factor of 5, given that the SNR is proportional to B 3/2 56 . This enhancement could allow us to obtain images 25 times faster while maintaining the same SNR. Moreover, increasing the magnetic field to approximately 65 mT – 10× higher than our current setup – would still keep the system cost-effective. This increase in field strength would provide a substantial boost in SNR, leading to dramatic reductions in imaging time and improvements in spatial resolution. Such advancements would bring us closer to achieving clinical standards for breast cancer imaging. At 1.5 T and 3 T, chemical-shift fat suppression is a necessary part of breast imaging. We note that the absolute chemical shift between fat and water decreases with decreasing field strength, making conventional fat suppression techniques more challenging. Previous work using NMR and NMR dispersion techniques observe that the T1 relaxation time of adipose tissue in the breast does not change with field strength, while the T1 relaxation time of fibroglandular tissues do change with field strength 44 , 45 . Thus, it may be possible to make a fat suppression technique that takes advantage of the T1 relaxation time differences with field strength (i.e., T1 dispersion). Exogenous injected contrast agents are typically used to increase the contrast between a tissue of interest and the surrounding tissue, and clinical breast MRI requires the use of contrast agents to identify breast tumors 57 – 59 . However, there is concern about the long-term effects of repeated administration of MRI contrast agents such as gadolinium 60 . At low magnetic fields, however, gadolinium-based contrast agents do not improve the contrast of the image, in part because gadolinium is not magnetically saturated at low magnetic fields and thus does not increase the brightness of the image. Recent work highlights the possibilities of iron-oxide nanoparticles and superparamagnetic iron oxide nanoparticles (SPIONs) for use at low magnetic fields 61 , 62 . A possible benefit of iron-oxide based agents is their biocompatibility, and preliminary in vivo studies used ferumoxytol, an FDA-approved SPION-based treatment of iron deficiency anemia 63 , 64 . Contrast agents were not used in this preliminary study. With this perspective on low-field MRI physics, our initial results open up a range of exciting possibilities for non-contrast, ULF, breast MRI. A specially designed ULF MRI system could be adapted for various imaging orientations – beyond the current prone position to include supine, sitting, or standing positions. Innovative magnet designs could further enhance portability, reduce costs, and enable integration into surgical suites or other settings where traditional high-field MRI systems (1.5 T and 3 T) are impractical or unsafe. ULF MRI systems have the potential to dramatically increase access to breast cancer screening. The absence of gadolinium-based contrast agents, elimination of compression, and the elimination of confined spaces could make screening more accessible and acceptable. Additionally, a radiation-free, easily accessible system would facilitate frequent imaging, allowing for close monitoring of disease progression or stability. This approach would enable us to identify which tumors are progressing and make informed decisions about treatment. In summary, our demonstration of ULF magnetic resonance breast imaging – without the need for contrast agents or compression—paves the way for a new, accessible option in breast cancer screening. This approach could become a valuable tool for approximately one eighth of the global population, potentially transforming the landscape of breast cancer detection and management. Methods Study Design This prospective pilot study was performed to observe the capabilities of breast imaging at 6.5 mT. The observational study was granted institutional review board approval from the Office for Human Research Studies (protocol 21–579) at the Dana-Farber/Harvard Cancer Center. All methods were performed in accordance with the relevant guidelines and regulations. Written informed consent was obtained from each participant. 11 healthy female participants (mean age, 35 years ± 13 years), two patients with a history of breast cancer (ages 51 and 58 years, respectively), and one 48-year-old patient with a benign mass were enrolled. Exclusion criteria were: pregnancy, breastfeeding, or inability to undergo MRI due to presence of an implanted or external MRI unsafe device or MR conditional device not meeting the conditions required for the scan. Participants had to be older than 20 and younger than 80 years old. The study also excluded individuals directly supervised by study investigators. Imaging System Imaging was performed on a custom-built electromagnetic MRI scanner, shown in Fig. 1 A and previously described 46 . The scanner operates at a main field strength of 6.5 mT (Larmor frequency of 276.18 kHz). The magnetic field inhomogeneity measured over a 20 cm spherical region at isocenter is less than 10 Hz. Imaging gradients are produced by a biplanar gradient set capable of producing linear gradients of up to 1 mT/m in all three axes. For this study, the imaging bed was modified from its previous configuration for neuroimaging 46 to a breast imaging setup where the breast and breast RF coil are located at the isocenter of the scanner. Figure 1 B-D illustrates the imaging bed and dedicated RF coil designed to image a single breast. In order to achieve a good filling factor and thus a high SNR 55 , a close-fitting conical breast RF coil was designed. To evaluate RF coil homogeneity, the magnetic field was calculated using the Finite-Element-Method simulation (Ansys Maxwell, 2021, Ansys, Canonsburg, PA, USA). The simulated magnetic field was used to assess the field homogeneity within the breast volume and to determine the magnetic field fall-off beyond the physical end of the coil (Fig. 1 E). The uniformity of the breast imaging region was also assessed using a homogeneous flexible phantom consisting of a latex balloon filled with deionized water. This MR phantom was placed inside the breast RF coil, and as seen in Fig. 1 F, it occupied the entire imaging region-of-interest. The imaging protocol used to scan the MR phantom was the same as that of participant scanning protocol. The RF coil design was determined based on several factors. The conical coil shape was based on promising study results at higher field strengths 65 and adapted in size to enable imaging of larger breasts, based on the reported common female breast sizes in the US 66 . The coil height is 10 cm; its diameter at the base is 19 cm; and its diameter at the peak is 4 cm 67 – 69 . The RF coil is uniformly wound on a conical supporting structure. This coil design is capable of imaging the whole breast and the chest wall to a depth of approximately 3 cm. Using this breast coil, one breast of all participants was imaged with participants in the prone position, as illustrated in Fig. 1 C. MRI acquisition An axial 3D balanced steady-state free precession (bSSFP) sequence was used in this study with a flip angle of 70 degrees, TE (echo time)/TR (repetition time) of 13 ms/26 ms, a matrix size of 64 × 72 × 21 and 50 averages. To accelerate the imaging process, an under-sampling factor of 70% was used. Depending on the evaluation criteria, for all healthy participants, the left breast was scanned with a voxel size of 3 mm × 3 mm × 8 mm, and total scan time was 21 minutes 36 seconds. For the three patients with either breast cancer history or benign mass, the spatial resolution was adjusted depending on the size of the breast. The patient with a history of invasive ductal carcinoma and papillary carcinoma in the subareolar region of the right breast was scanned for 30 minutes with a spatial resolution of 2 mm × 2 mm × 6 mm. The patient with a history of invasive lobular carcinoma and the patient with a cystic mass in their left breasts were scanned for 45 minutes with a spatial resolution of 2 mm × 2 mm × 4 mm. Given the scan duration, the study was limited to imaging one breast. No contrast agents were used. Images were reconstructed in MATLAB (Natick, MA, USA) using inverse fast Fourier transform (IFFT) with the under-sampled region zero-filled in k-space. Images were converted into DICOM format using the MATLAB function dicomwrite. No data-driven Artificial Intelligence (AI) or other machine learning-based methods were used in the image acquisition or reconstruction. The images of all 11 healthy participants were reviewed by three board-certified breast radiologists (M.A.S., L.R.L., and J.C.V.C.) with 13, 9, and 3 years of experience reading breast MRI. The readers reviewed the evaluation criteria; however, due to the limited data of this pilot study, no additional images were used to train the readers. Images were viewed in DICOM format using 3D Slicer 70 . The visibility of the following features in the breast was assessed: visibility of the breast outline, visibility of the fibroglandular tissue (FGT) compared to intramammary adipose tissue, demarcation of the nipple areolar complex (NAC), and visualization of the pectoralis muscle (chest wall). Visibility of these features was assessed using a 5-point Likert scale (1 – not at all visible, 2 – barely visible, 3 – clearly visible but blurred, 4 – clearly visible and sharp, 5 – clearly visible and very sharp). Breast tissue pattern (density) was assessed using four categories: fatty, scattered FGT, heterogeneous FGT, and extreme FGT. Images were also evaluated for motion artifacts. Three of the 11 healthy participants had screening mammograms available for comparison to the ULF MRI. The screening mammograms were reviewed by one board-certified radiologist (M.A.S.) with 13 years of experience with breast MRI. The radiologist noted the breast tissue pattern and visibility of key breast features on the ULF MRI and the x-ray mammogram. For the three patients with either breast cancer history or benign mass, the ULF MRI and any clinical imaging were reviewed by one board-certified radiologist (M.A.S.) with 13 years of experience with breast MRI. The radiologist noted the breast tissue pattern, visibility of key breast features, and any clinical findings across all images. Statistical Analysis Inter-reader agreement was assessed by computing Fleiss’ kappa among three readers’ feature visibility assessments. Due to the novelty of these images, i.e., they were new to all readers, and the limited data set, which did not allow for proper training of the readers, the readers were not “calibrated” to each other, as they are when reading clinical MRI. As a result, the 5-point scale was revised to a binary scale to assess whether or not a feature was visible (1 – not at all visible, 2 or greater – visible). All statistical analyses were performed using IBM SPSS Statistics for Windows, version 26.0. (IBM Corp., Armonk, NY, USA). Declarations Acknowledgments The authors would like to thank Darrah Bowden for her invaluable assistance and perspective on the breast imaging configuration. MSR dedicates this work to the memory of Christina Pfeifer Mattig. Funding: National Institutes of Health grant 1R21CA267315 (KEK, MSR) Kiyomi and Ed Baird MGH Research Scholar award (MSR) German-American Fulbright Commission (FKL) National Institute of Standards and Technology (KEK, SEO) NIST-PREP 70NANB18H006 from U.S. Department of Commerce (SEO) Author contributions: Conceptualization: KEK, MSR Methodology: SS, NK, FKL, MAS, TPPH, SEO Investigation: SS, NK, FKL, MAS, LRL, JVCV, TPPH, MSR Visualization: SS, NK, MAS, JVCV, SEO, KEK, MSR Supervision: SY, TRB, KEK, MAS, MSR Writing—original draft: SS, NK, KEK, MSR Writing—review & editing: SS, NK, FKL, MAS, LRL, JVCV, TPPH, SEO, SY, TRB, KEK, MSR Competing interests: MSR is a founder and equity holder of Hyperfine, Inc. MSR is a consultant and equity holder in DeepSpin GmbH. All other authors declare no conflicts. Data and materials availability: All data generated or analyzed during the study are available in the main text. 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Eng. 72 , 1750–1765 (2025). Fedorov, A. et al. 3D Slicer as an image computing platform for the Quantitative Imaging Network. Magn. Reson. Imaging . 30 , 1323–1341 (2012). Tables Table 1 is available in the Supplementary Files section. Additional Declarations No competing interests reported. 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We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-6882799","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":489606825,"identity":"8c49239f-ac3d-428c-b580-2224363a55d8","order_by":0,"name":"Sheng Shen","email":"","orcid":"","institution":"Athinoula A. 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The three axes of the gradient set are shown as Gx (in blue), Gy (in green) and Gz (in magenta), and the biplanar coils of the resistive electromagnet are shown in brown (two per side, four total). The participant lays on the patient table in the prone position with the head turned to the side. The breast is placed in the RF coil located at the scanner isocenter. (\u003cstrong\u003eB\u003c/strong\u003e) CAD model of RF coil designed for breast imaging at 276 kHz. \u003cstrong\u003eIn vivoexperimental setup\u003c/strong\u003e – (\u003cstrong\u003eC\u003c/strong\u003e) The top and side view of the subject lying in the prone position on the subject table with the breast placed into the RF coil. (\u003cstrong\u003eD\u003c/strong\u003e) A view of the subject table with red arrow indicating the location of the 3D printed breast RF coil fixed. \u003cstrong\u003eAssessment of the imaging volume of the conical-shaped breast RF coil. \u003c/strong\u003e(\u003cstrong\u003eE\u003c/strong\u003e) The magnetic field calculation of the breast RF coil where the color bar indicates the B1 field distribution (in µT/A) across the breast volume. (\u003cstrong\u003eF)\u003c/strong\u003e A homogeneous phantom was imaged with a latex balloon (blue) filled with deionized water placed inside the breast RF coil. (\u003cstrong\u003eG\u003c/strong\u003e) Central slice of a 21-slice 3D-bSSFP acquisition of the balloon phantom. The scan shows the signal uniformity of the RF coil. The red line indicates the end of the plate of the RF coil.\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-6882799/v1/f1aeb8bc94bdbcdf3ae68a2d.png"},{"id":87554369,"identity":"fa171737-03c9-46cf-bbec-3457d2853e17","added_by":"auto","created_at":"2025-07-25 06:41:17","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":596924,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003e3D ultra-low field breast MRI obtained at 6.5 mT from a 34-year-old healthy woman with heterogeneous fibroglandular tissue (FGT).\u003c/strong\u003e \u003cstrong\u003e(A) \u003c/strong\u003e18 out of 21 sequential axial bSSFP-weighted slices of the left breast are shown, and no contrast agent was administered. Data was acquired in approximately 21 minutes with a spatial resolution of 3 mm ´ 3 mm ´ 8 mm. Vertical and horizontal scale bars in white are 3 cm each and are shown in slice 3. \u003cstrong\u003e(B)\u003c/strong\u003e A representative axial slice is shown, where all features are visualized in this study: breast outline, FGT, nipple areolar complex, and chest wall.\u003c/p\u003e","description":"","filename":"floatimage1.png","url":"https://assets-eu.researchsquare.com/files/rs-6882799/v1/0dcda22ca31588c2974082d1.png"},{"id":87554378,"identity":"8db65eb9-c652-411b-b21d-c865471a4fd8","added_by":"auto","created_at":"2025-07-25 06:41:17","extension":"jpeg","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":800200,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003e3D ultra-low field breast MRI obtained at 6.5 mT from a 31-year-old healthy woman with scattered fibroglandular tissue (FGT).\u003c/strong\u003e 17 out of 21 representative sequential axial bSSFP-weighted slices of the left breast are shown, and no contrast agent was administered. Data was acquired in approximately 21 minutes with a spatial resolution of 3 mm ´ 3 mm ´ 8 mm. Vertical and horizontal scale bars in white are 3 cm each and are shown in slice 1. \u003cstrong\u003e(B) \u003c/strong\u003eThe nipple areolar complex and chest wall were not well visualized in this study. In the representative slice 8 shown, the breast outline and FGT were visualized and annotated by a breast radiologist.\u003c/p\u003e","description":"","filename":"floatimage2.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-6882799/v1/bded23bd31cc5c4d7efb324b.jpeg"},{"id":87554381,"identity":"0a8bc54d-7b1d-490a-a5c1-d7ef423f4290","added_by":"auto","created_at":"2025-07-25 06:41:17","extension":"jpeg","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":840603,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003e3D ultra-low field breast MRI obtained at 6.5 mT from a 31-year-old healthy woman with extreme fibroglandular tissue (FGT).\u003c/strong\u003e 18 out of 21 representative sequential axial bSSFP-weighted images of the left breast are represented. No contrast agent was administered. Data was acquired in approximately 21 minutes with a spatial resolution of 3 mm ´ 3 mm ´ 8 mm. Vertical and horizontal scale bars in white are 3 cm each and are shown in slice 1.\u003cstrong\u003e (B)\u003c/strong\u003e A representative slice was labelled by a breast radiologist, and all features are visualized in this study: breast outline, FGT, nipple areolar complex, and chest wall.\u003c/p\u003e","description":"","filename":"floatimage3.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-6882799/v1/e37ab1d0775a273fb0306eb2.jpeg"},{"id":87554364,"identity":"30bc8a32-c4fe-43de-b08a-7155485890d3","added_by":"auto","created_at":"2025-07-25 06:41:17","extension":"jpeg","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":550247,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003e3D ultra-low field breast MRI obtained at 6.5 mT and X-ray mammogram of a 48-year-old healthy woman with scattered fibroglandular tissue (FGT).\u003c/strong\u003e 9 out of 21 representative sequential axial bSSFP-weighted images of the left breast are shown. No contrast agent was administered. Data was acquired in approximately 21 minutes with a spatial resolution of 3 mm ´ 3 mm ´ 8 mm. Vertical and horizontal scale bars in white are 3 cm each and are shown in slice 7.\u003cstrong\u003e (B)\u003c/strong\u003e Slice 10 is a representative slice of the ULF scan, labelled by a breast radiologist, where skin, fibroglandular tissue, retromammary fat, and chest wall were visualized. The craniocaudal view of the X-ray mammogram is shown alongside the breast radiologist’s labels. The same four breast features were also identified on the mammogram. Vertical and horizontal scale bars in white are 3 cm each. Images were reconstructed without the use of AI or ML-based approaches.\u003c/p\u003e","description":"","filename":"floatimage4.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-6882799/v1/f0435480349ab2a29fa6f648.jpeg"},{"id":87554365,"identity":"41664c29-d0e3-4170-b21f-6709554aecdd","added_by":"auto","created_at":"2025-07-25 06:41:17","extension":"jpeg","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":996151,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eObservation of post-surgical changes on a 3D ultra-low field breast MRI scan of the right breast of a 51-year-old woman diagnosed 2 years prior to this study with invasive ductal carcinoma (grade 1) and papillary carcinoma (grade 1) in the subareolar region of the right breast. \u003c/strong\u003ePatient received a localized lumpectomy prior to tamoxifen treatment. \u003cstrong\u003e(A) \u003c/strong\u003e12 out of 21 representative sequential axial bSSFP-weighted images of the right breast are shown. No contrast agent was administered. Data was acquired in approximately 30 minutes with a spatial resolution of 2 mm ´ 2 mm ´ 6 mm. \u003cstrong\u003e(B)\u003c/strong\u003e A representative slice, slice 12 of the 3D ULF scan, the craniocaudal view of the mammogram of the right breast and the corresponding slice of the 1.5 T MRI scan of the right breast were labelled by a breast radiologist. The radiologist labelled the breast tissue pattern as scattered fibroglandular tissue (FGT), and the features visualized in this study were: skin, nipple areolar complex, FGT, retromammary fat, and chest wall. The post-surgical change was detected on the ULF scan; no susceptibility artifacts from the surgical clips were observed. The surgical clips were all visible on the mammogram. On the high field MRI scan, the susceptibility artifacts from the surgical clips were visible. Horizontal scale bars in white are 3 cm.\u003c/p\u003e","description":"","filename":"floatimage5.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-6882799/v1/4f075788dd2b50b3f7a17288.jpeg"},{"id":87554715,"identity":"d7c29f44-bc27-4588-9b93-379ae4e3b32e","added_by":"auto","created_at":"2025-07-25 06:49:17","extension":"jpeg","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":926662,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eExample of reduction of susceptibility artifacts from surgical clips on a 3D ultra-low field breast MRI scan of the left breast of a 58-year-old woman diagnosed 3 years prior to this study with invasive lobular carcinoma (grade 3). \u003c/strong\u003ePatient received a left breast lumpectomy. \u003cstrong\u003e(A)\u003c/strong\u003e 12 out of 21 representative sequential axial bSSFP-weighted images of the left breast are shown. No susceptibility artifacts were seen on the ULF MRI. No contrast agent was administered. Data was acquired in approximately 45 minutes with a spatial resolution of 2 mm ´ 2 mm ´ 4 mm. \u003cstrong\u003e(B)\u003c/strong\u003e A representative slice, slice 14, was labelled by a breast radiologist, where the following features were visualized: nipple areolar complex, skin, FGT, and chest wall. The breast tissue is heterogeneously dense. The craniocaudal view of the mammogram showed the nipple areolar complex, the skin, the fibroglandular tissue, and the surgical clips. The 3 T bilateral breast MRI image showed the skin, the fibroglandular tissue, the chest tissue, and the susceptibility artifact from the surgical clip at the site of the lumpectomy. Horizontal scale bars in white are 3 cm.\u003c/p\u003e","description":"","filename":"floatimage6.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-6882799/v1/f49ec6aa5c2b332da7c02edc.jpeg"},{"id":87554716,"identity":"2cc5b633-bc72-4c71-a839-11ba44fea0be","added_by":"auto","created_at":"2025-07-25 06:49:17","extension":"jpeg","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":901155,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eObservation of a known mass on a 3D ultra-low field breast MRI scan of a 48-year-old woman in the subareolar region of the left breast near the nipple. Patient received an X-ray mammogram and a targeted breast ultrasound, which confirmed a benign cystic mass. (A) \u003c/strong\u003e9 out of 21 representative sequential axial bSSFP-weighted images of the left breast are shown. No contrast agent was administered. The cystic mass was detected on the ULF scan on several slices. The breast radiologist confirmed its location. Data was acquired in approximately 45 minutes with a spatial resolution of 2 mm ´ 2 mm ´ 4 mm. \u003cstrong\u003e(B)\u003c/strong\u003e A representative slice, slice 14 was labelled by a breast radiologist, where the features visualized in this study were: skin, FGT, nipple areolar complex, chest wall, and the oval mass. The breast tissue is extremely dense. The craniocaudal view of the mammogram showed skin, FGT, nipple areolar complex, and the oval mass. The targeted ultrasound exam of the left breast revealed a bilobular anechoic mass with the reported dimensions of 35 mm ´ 26 mm ´ 16 mm. The cystic mass was segmented on the ULF scan, and the dimensions of the mass was determined to be 33 mm ´ 20 mm ´ 18 mm (volume = 8160 mm\u003csup\u003e3\u003c/sup\u003e). Horizontal scale bars in white are 3 cm.\u003c/p\u003e","description":"","filename":"floatimage7.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-6882799/v1/e656100dba20db0f85822bba.jpeg"},{"id":103251272,"identity":"48998213-03ba-4340-aa18-7166b5f14dfb","added_by":"auto","created_at":"2026-02-23 16:07:52","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":7635407,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6882799/v1/6fe17e98-7749-47f1-9b5e-fb7ab9547f41.pdf"},{"id":87554382,"identity":"dac310e3-efb7-4075-9903-8e6ef8e080f9","added_by":"auto","created_at":"2025-07-25 06:41:17","extension":"docx","order_by":0,"title":"","display":"","copyAsset":false,"role":"supplement","size":865114,"visible":true,"origin":"","legend":"","description":"","filename":"supplementarymaterials.docx","url":"https://assets-eu.researchsquare.com/files/rs-6882799/v1/e70e79f223b7af637d678cfb.docx"},{"id":87554372,"identity":"6f889053-0fe0-4d18-ab34-4a5aef521f58","added_by":"auto","created_at":"2025-07-25 06:41:17","extension":"docx","order_by":2,"title":"","display":"","copyAsset":false,"role":"supplement","size":21716,"visible":true,"origin":"","legend":"","description":"","filename":"Table1.docx","url":"https://assets-eu.researchsquare.com/files/rs-6882799/v1/59208fd70d0ca303e51ffb21.docx"}],"financialInterests":"No competing interests reported.","formattedTitle":"Breast imaging with ultra-low field MRI","fulltext":[{"header":"Introduction","content":"\u003cp\u003eIn 2021, over two billion women worldwide were over the age of 40 \u003csup\u003e1,2\u003c/sup\u003e, and each of them face the risk of developing breast cancer. This disease will affect approximately one in eight women during their lifetime \u003csup\u003e\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e\u003c/sup\u003e, with 85% of cases occurring in those without any family history of the disease \u003csup\u003e\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e\u003c/sup\u003e. Additionally, early-onset breast cancer tends to be more aggressive and has a poorer prognosis \u003csup\u003e\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e\u003c/sup\u003e. However, current screening guidelines are insufficient in this population \u003csup\u003e\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e,\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e\u003c/sup\u003e, highlighting the need for continued advancements in early detection strategies. Currently, mammography is the most widely used imaging tool for breast cancer screening due to its accessibility and cost-effectiveness. However, it has notable limitations: it involves ionizing radiation, causes discomfort due to breast compression, has a false positive rate ranging from 10.2\u0026ndash;14.4% \u003csup\u003e8\u0026ndash;10\u003c/sup\u003e, and misses 1\u0026ndash;35% of breast cancers \u003csup\u003e\u003cspan additionalcitationids=\"CR12 CR13 CR14 CR15 CR16\" citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e\u003c/sup\u003e. Consequently, in the United States as of 2015, only 65.3% of women over 40 had a screening mammogram in the previous two years \u003csup\u003e\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e\u003c/sup\u003e. Given that more than half of the global population should undergo breast cancer screening multiple times in their lives \u003csup\u003e\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e\u003c/sup\u003e, there is an urgent need for a more accurate and patient-friendly screening tool.\u003c/p\u003e\u003cp\u003eCurrently available MRI-based methods overcome some of these limitations \u003csup\u003e\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e\u003c/sup\u003e, particularly in high-risk groups \u003csup\u003e\u003cspan additionalcitationids=\"CR22\" citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e\u003c/sup\u003e. This is because differences in soft tissues can be visualized without obfuscations from dense tissue, and MRI screening has low false-negative rates \u003csup\u003e\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e,\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e\u003c/sup\u003e. MRI can detect invasive carcinomas, distinguishing between malignant and benign lesions using T1 and T2-weighted imaging with injected contrast agent enhancement \u003csup\u003e\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e\u003c/sup\u003e. Additionally, apparent diffusion coefficient (ADC) can be used to differentiate lesions \u003csup\u003e\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e\u003c/sup\u003e and assess response to treatment \u003csup\u003e\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e\u003c/sup\u003e. However, clinical breast screening exams on traditional MRI scanners require the patient to endure a constricted setting in addition to receiving IV contrast administration. MRI as a screening modality is currently underutilized in high-risk women (defined as a lifetime risk\u0026thinsp;\u0026gt;\u0026thinsp;20%) \u003csup\u003e\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e\u003c/sup\u003e. While fast MRI protocols enable screening in less than 10 minutes \u003csup\u003e\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e\u003c/sup\u003e, the high cost and limited number of scanners (\u0026lt;\u0026thinsp;38 scanners per million people in the US) prohibit their use as a primary screening tool for breast cancer.\u003c/p\u003e\u003cp\u003eCompared to clinical MRI systems operating at 1.5 T or 3 T, low- (\u0026lt;\u0026thinsp;100 mT) and ultra-low field (ULF, \u0026lt;\u0026thinsp;10 mT) MRI systems offer a significantly lower cost and accessible alternative with far less strict installation requirements. This accessibility opens the door to broader use, particularly in settings where traditional MRI systems are unavailable and impractical including in low- and middle-income countries globally \u003csup\u003e\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e\u003c/sup\u003e. Additionally low and ultra-low field MRI systems do not require IV contrast administration. Low-field MRI neuroimaging systems operating at 64 mT have already been successfully implemented in clinical settings for stroke detection at the patient\u0026rsquo;s bedside \u003csup\u003e\u003cspan additionalcitationids=\"CR33\" citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e\u003c/sup\u003e. These systems are portable, safe, and simple to operate, and do not require an MRI technician or special magnetic- or RF-shielded room \u003csup\u003e\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e,\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e\u003cp\u003eAlthough operation at lower magnetic field typically yields images with reduced signal-to-noise ratio (SNR), the clinical efficacy of low-field MRI for neuroimaging has been clearly demonstrated \u003csup\u003e\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e,\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e,\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e\u003c/sup\u003e. Moreover, laboratory developments have shown the potential for low-field MRI in extremity \u003csup\u003e\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e\u003c/sup\u003e and whole-body imaging \u003csup\u003e\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e\u003c/sup\u003e, though applications to breast imaging have yet to be realized.\u003c/p\u003e\u003cp\u003eGiven the recent clinical successes of low field MRI for neuroimaging, we propose that ULF MRI could potentially achieve sufficient SNR for effective breast imaging. Historically, Nuclear Magnetic Resonance (NMR)-based methods have shown promise in breast cancer assessment. From 1975\u0026ndash;1982, T1 and T2 relaxation times of breast tissues were measured at 0.71 T \u003csup\u003e\u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e\u003c/sup\u003e yielding encouraging results. Subsequent studies measured the T1 of mastectomy samples at 0.09 T and 0.35 T \u003csup\u003e\u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e,\u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e42\u003c/span\u003e\u003c/sup\u003e, and \u003cem\u003ein vivo\u003c/em\u003e whole-breast imaging was attempted at 45 mT. Although these early efforts were hampered by excessively long exam times, they supported the fundamental findings of the NMR studies \u003csup\u003e\u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e43\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e\u003cp\u003eAdditional research using NMR dispersion (NMRD) measurements revealed that the T1 relaxation times of cancerous \u003cem\u003eex vivo\u003c/em\u003e breast tissues differ significantly from those of healthy fibroglandular and adipose tissues in the low- and ultra-low field regimes \u003csup\u003e\u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e,\u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e44\u003c/span\u003e,\u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e45\u003c/span\u003e\u003c/sup\u003e. These differences in T1 relaxation times form the basis of our current research. If we can achieve sufficient SNR within a reasonable exam duration, ULF breast MRI could emerge as a cost-effective alternative for breast imaging, offering the advantages of contrast-free, multi-slice soft tissue visualization over the X-ray projection-based method used in mammography.\u003c/p\u003e\u003cp\u003eIn this study, we present our preliminary evaluation of breast imaging using ULF MRI, showcasing its potential as a transformative tool in breast cancer screening. Utilizing a laboratory-based ULF MRI system operating at 6.5 mT with a unilateral conical RF coil, we imaged the left breasts of 11 healthy women, one right and one left breast of two patients with a history of breast cancer, and the left breast of one patient with a known benign mass. In healthy participants, the ULF MR images of the whole breast revealed essential breast features, including type of fibroglandular tissue, breast outline, nipple areolar complex, and chest wall. Additionally, for three healthy participants the 3D ULF MRI scans are compared to their X-ray mammogram. For both patients with a history of breast cancer, the artifacts typically generated by surgical clips and post-surgical changes were evaluated. And lastly, the feasibility of detecting a benign mass at ULF was also investigated.\u003c/p\u003e"},{"header":"Results","content":"\u003cp\u003e\u003cstrong\u003eImaging system\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eImaging was performed on a custom-built electromagnet-based MRI scanner shown in Fig. 1 and modified for breast imaging from its previously described configuration for neuroimaging\u0026nbsp;\u003csup\u003e46\u003c/sup\u003e. Figure 1 shows the imaging bed and dedicated RF coil designed to image a single breast. The breast and breast RF coil are placed at the isocenter of the scanner (Fig. 1D).\u003c/p\u003e\n\u003cp\u003eA close-fitting conical breast coil was designed, the RF magnetic field generated by this coil simulated, and the resultant field map is shown in Fig. 1E. The field homogeneity within the breast RF coil was quantified, revealing an inhomogeneity of \u0026plusmn;60% over the breast volume region, and a magnetic field fall-off 3 cm inside the chest wall of 30%. To evaluate the sensitivity of the coil, a homogeneous flexible phantom filled with deionized water was positioned inside the breast RF coil and scanned (Fig. 1F). The phantom imaging result (Fig. 1G) reflects the sensitivity distribution across the RF coil, demonstrating high sensitivity within the coil and a marked decrease in sensitivity towards the opening of the RF coil.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eParticipant characteristics and imaging protocol\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eULF MRI was used to image the left breast of 11 healthy women (mean age, 35 years \u0026plusmn; 13 years). Additionally, three patients participated: a 51-year-old patient with a history of invasive ductal carcinoma (grade 1) and papillary carcinoma (grade 1), a 58-year-old patient with a history of invasive lobular carcinoma (grade 3), and a 48-year-old patient with a known benign mass. All women completed the study.\u003c/p\u003e\n\u003cp\u003eA 3D balanced SSFP (bSSFP) sequence was used with a constant voxel size of 3 mm \u0026times; 3 mm \u0026times; 8 mm, and the resulting total scan time was 21 minutes 36 seconds for all the healthy participants. For the three cases with known pathology, a higher spatial resolution was used depending on the breast size. For larger breast size (n=1), a 30-minute scan with a voxel size of 2 mm \u0026times; 2 mm \u0026times; 6 mm was used, and for smaller breast size (n=2), a 45-minute scan with a voxel size of 2 mm \u0026times; 2 mm \u0026times; 4 mm was used. No data-driven Artificial Intelligence (AI) or other machine learning-based methods were used in the image acquisition or reconstruction.\u003c/p\u003e\n\u003cp\u003eThe MR sequence and positioning were well tolerated. None of the images were degraded by patient motion. It is noteworthy that none of the participants experienced discomfort during the exam, and the breast fit naturally in the conical-shaped RF coil without compression.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eULF MRI breast imaging findings\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eImage sets of the entire left breast for three representative subjects with different breast tissue patterns are shown in Fig. 2 \u0026ndash; 4. For these three representative subjects, the following features were labeled by a breast radiologist: visibility of the breast outline or skin, NAC, FGT, and chest wall. The bSSFP pulse sequence has a mixed contrast that depends on the ratio of T2/T1, such that fat tissue appears bright and fibroglandular tissue appears dark.\u003c/p\u003e\n\u003cp\u003eBreast images from all 11 participants were evaluated by three independent board-certified breast radiologists for the purpose of categorizing breast density and assessing the visibility of essential breast tissues, which include the type of fibroglandular tissue, the breast outline, the nipple areolar complex, and the chest wall. Individual image scores are reported in Table 1. Breast tissue pattern was assessed using fatty, scattered FGT, heterogeneous FGT, and extreme FGT. Inter-reader reliability of breast tissue pattern was determined using Fleiss\u0026apos; kappa, which resulted in a kappa value of 0.73 (95% confidence interval: 0.72 to 0.74, p\u0026lt;0.001), indicating substantial agreement among the readers.\u003c/p\u003e\n\u003cp\u003eVisibility of the following features in the breast was scored using a 5-point Likert scale (1 \u0026ndash; not at all visible to 5 \u0026ndash; clearly visible and very sharp): breast outline, fibroglandular tissue (FGT) compared to intramammary adipose tissue, demarcation of the nipple areolar complex (NAC), and the chest wall, defined as visualization of the pectoralis muscle. The limited data set from this pilot study did not allow for proper training of the readers, and given the novelty of the images, the readers were not well \u0026ldquo;calibrated\u0026rdquo; to each other. For example, when evaluating the visibility of the breast outline, we find the readers were internally consistent: each reader scores all images with the same visibility (with the exception of a single case for reader 1 that received a higher score). However, each reader has assigned a different visibility score from the other readers. As a result, a binary rating system was adopted from the 5-point scale with a score of 1 remaining not at all visible and scores 2-5 as visible. Fleiss\u0026rsquo; kappa was also used to measure the agreement regarding the visibility of essential breast tissues which included the type of fibroglandular tissue, the breast outline, nipple areolar complex (NAC), and the chest wall. In this binary framework, consensus on the visibility of the breast outline and fibroglandular (FGT) tissue was consistent (kappa = 1), whereas the NAC and chest wall exhibited kappa values of 0.54 (95% confidence interval: 0.58 to 0.60, p\u0026lt;0.001) and 0.27 (95% confidence interval: 0.26 to 0.28, p\u0026lt;0.2), respectively. \u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eULF MRI acquisition and X-ray mammography of healthy participants\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThree of the 11 healthy participants had a bilateral screening mammogram within 8 months of their participation in the ULF MRI study. These mammograms were labelled by a breast radiologist with 13 years of experience. All three participants have scattered fibroglandular tissue, and Fig 5 shows a representative case with the different breast features identified on both the ULF MRI and the mammogram. The other two cases are reported in Figs S1 and S2 in the supplemental material. Comparison to mammography confirms that the ULF MRI reliably shows the fibroglandular tissue.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003ePatient scanning at ULF MRI\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eImaging was also performed in three patients with a history of breast disease: two with a history of breast cancer and one with a palpable, known cystic mass. For these studies, the spatial resolution was increased in all three dimensions, and to maintain SNR, signal averaging was increased resulting in a longer scan time.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eFigure 6 shows the images of a patient with a history of invasive ductal carcinoma (grade 1) and papillary carcinoma (grade 1) in the subareolar region of the right breast diagnosed two years prior to this study. The patient received a localized lumpectomy prior to tamoxifen treatment. The ULF MRI showed all breast features including NAC, skin, FGT, retromammary fat, and chest wall. ULF MRI also showed the post-surgical changes at the site of the lumpectomy with no susceptibility artifacts from the surgical clips. The X-ray mammogram and the 1.5 T clinical breast MRI also showed the different breast features. The mammogram clearly showed the surgical clips, and the susceptibility artifacts from the surgical clips are visible on the 1.5 T MRI scan.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eFigure 7 shows representative slices of a patient with a history of invasive lobular carcinoma (grade 3) in the left breast. The patient received a lumpectomy three years prior to this study. The surgical clips were not visible on ULF images due to their small size (length 4 mm) and due to the absence of susceptibility artifacts at lower magnetic field strengths. The surgical clips are visible on X-ray mammogram, and at 1.5 T MRI, the susceptibility artifacts indirectly show the location of the surgical clips.\u003c/p\u003e\n\u003cp\u003eFigure 8 shows images from a patient with a palpable mass that was imaged with ULF MRI; the patient had a known cystic mass on X-ray mammogram and on the targeted ultrasound exam. On ULF MRI, the cystic mass is clearly visible on five slices at approximately 1 cm above the nipple on the medial side of the left breast. The location of the mass was confirmed by a breast radiologist. Using ULF MRI, the size of the mass was evaluated as 33 mm\u0026nbsp;\u0026acute;\u0026nbsp;20 mm\u0026nbsp;\u0026acute;\u0026nbsp;18 mm, which agrees with the reported values assessed on the ultrasound exam of 35 mm\u0026nbsp;\u0026acute;\u0026nbsp;26 mm\u0026nbsp;\u0026acute;\u0026nbsp;16 mm. The volume of the mass estimated using the 3D ULF MRI was 8.16 cm\u003csup\u003e3\u003c/sup\u003e.\u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eIn this preliminary study, we successfully performed \u003cem\u003ein vivo\u003c/em\u003e MR breast imaging at 6.5 mT on healthy participants and on patients with either a history of breast cancer or a benign mass. Essential breast features were identified such as breast outline or skin, FGT, NAC, and chest wall. We included 11 participants with a range of breast sizes, and images were acquired using a single bSSFP sequence with an imaging duration of approximately 21 minutes. The three clinical case studies included two patients with a history of breast cancer who have both undergone lumpectomy and one patient with a benign mass. All of the ULF MRI scans were acquired at 6.5 mT without the use of exogeneous IV contrast agents or the use of machine learning for image acquisition and reconstruction. These promising results motivate us to further develop ULF MRI for breast imaging.\u003c/p\u003e\u003cp\u003eGlobally, one-eighth of the population, or 2.2\u0026nbsp;billion women over age 40, are recommended to undergo regular breast cancer screenings \u003csup\u003e\u003cspan citationid=\"CR47\" class=\"CitationRef\"\u003e47\u003c/span\u003e\u003c/sup\u003e. This translates to approximately 500\u0026nbsp;million screening exams needed every year, vastly surpassing the combined total of head injuries, strokes and brain tumors, which are estimated as 85\u0026nbsp;million annually \u003csup\u003e\u003cspan additionalcitationids=\"CR49 CR50\" citationid=\"CR48\" class=\"CitationRef\"\u003e48\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR51\" class=\"CitationRef\"\u003e51\u003c/span\u003e\u003c/sup\u003e. The potential impact of ULF MRI technology on breast cancer screening is enormous, offering a revolutionary, cost-effective solution for early detection and improved healthcare access worldwide.\u003c/p\u003e\u003cp\u003eMRI at low- and ultra-low magnetic fields is challenging due to inherently low Boltzmann polarization and consequently low signal. Two additional consequences of MRI physics at ultra-low magnetic field are relevant to this work. First, as magnetic field decreases, tissue T1 relaxation times generally decrease, while T2 relaxation times are generally constant across fields \u003csup\u003e\u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e44\u003c/span\u003e,\u003cspan citationid=\"CR52\" class=\"CitationRef\"\u003e52\u003c/span\u003e\u003c/sup\u003e. Second, the magnetic susceptibility artifacts are significantly reduced at ULF. We leverage both of these aspects to our advantage at 6.5 mT, where the efficiency of bSSFP in this regime is maximal \u003csup\u003e\u003cspan citationid=\"CR46\" class=\"CitationRef\"\u003e46\u003c/span\u003e\u003c/sup\u003e and enables banding-free imaging over large fields of view. In this study, the image SNR was sufficient to visualize key breast tissues.\u003c/p\u003e\u003cp\u003eThe three expert readers had substantial agreement in their evaluations of breast tissue patterns and key breast tissues. However, there were notable discrepancies: Reader 2\u0026rsquo;s scores were, on average, 33% lower than those of Reader 1 (paired t-test, p\u0026thinsp;\u0026lt;\u0026thinsp;0.001) and 28% lower than Reader 3 (paired t-test, p\u0026thinsp;\u0026lt;\u0026thinsp;0.001). Additionally, Reader 3\u0026rsquo;s scores were 7.01% higher than those of Reader 1 (paired t-test, p\u0026thinsp;\u0026lt;\u0026thinsp;0.03). There was also some disagreement regarding the visibility of the NAC and chest wall.\u003c/p\u003e\u003cp\u003eThese discrepancies can be attributed to two main factors: lack of training and experience with ULF MRI. The limited dataset prevented proper training, as the evaluation criteria were only discussed rather than practiced. Furthermore, the readers had no prior experience with ULF MRI images, leading to a lack of calibration across the readers. In contrast, when evaluating clinical breast MRI scans, the readers are implicitly calibrated, having each examined numerous scans over extensive periods (13 years, 3 years and 9 years, respectively). This experience gap underscores the need for dedicated training and calibration when introducing new imaging technologies like ULF MRI to ensure accurate and consistent evaluations.\u003c/p\u003e\u003cp\u003eThe visibility of the NAC and chest wall was inconsistent across scans. The absence of the NAC in certain images may be attributed to slice thickness, breast positioning, or natural anatomical variations such as flat or inverted nipples. The chest wall was not always visible, primarily in participants with a larger breast. This is a limitation of the RF coil design: with an imaging depth of approximately 3 cm from the coil\u0026rsquo;s end plate, the chest wall was not fully captured in individuals with larger breast sizes. This design constraint highlights a significant area for improvement in coil development to enhance imaging coverage for diverse breast sizes.\u003c/p\u003e\u003cp\u003eFor three of the healthy participants, recent mammograms were available. The comparison between ULF MRI scan and its corresponding mammogram shows that ULF MRI can determine fibroglandular tissue pattern and all four essential breast features. In the future, ULF MRI should be compared with mammography of participants with different breast tissue pattern (e.g., dense fibroglandular tissue).\u003c/p\u003e\u003cp\u003ePost-surgical changes were observable on ULF MRI scans for the patient diagnosed two years prior to this study with invasive ductal carcinoma (grade 1) and papillary carcinoma (grade 1) in the subareolar region of the right breast, and unlike at 1.5 T or 3 T, these changes were not obscured by susceptibility artifacts from surgical clips. In contrast, the location of surgical clips were not observed for the patient diagnosed three years prior to this study with invasive lobular carcinoma (grade 3). Typically, surgical clips are placed during biopsy or surgical procedures to serve as localization markers. On high-field breast MRI (1.5 T or 3 T), these clips generate susceptibility artifacts visible as dark patterns larger than the clips, which aid in locating the clips but also obscure the surrounding breast tissue. In ULF MRI, susceptibility artifacts from surgical clips are absent, allowing for unobstructed imaging of breast tissue. However, this lack of artifacts also makes it more challenging to locate the surgical clips themselves. To date, the scientific evidence on whether these susceptibility-related image artifacts in breast MRI may lead to misinterpretations or the inability to detect the respective lesion is very limited \u003csup\u003e\u003cspan citationid=\"CR53\" class=\"CitationRef\"\u003e53\u003c/span\u003e,\u003cspan citationid=\"CR54\" class=\"CitationRef\"\u003e54\u003c/span\u003e\u003c/sup\u003e. However, if low field breast MRI becomes a screening technique, the absence or reduced susceptibility artifacts caused by metallic marking clips will be crucial for early cancer detection for a group of patients who have retained tissue marker clips or foreign bodies within the breast tissue.\u003c/p\u003e\u003cp\u003eAt ULF, the cystic mass that was already proven on ultrasound was easily detected on multiple slices of the MR image. The bright MRI signal on the bSSFP scan and the dark signal on ultrasound indicate that the benign mass is fluid-filled. In contrast, X-ray mammography cannot differentiate between tissue types and is limited to detecting density variations. In ultra-low magnetic field imaging, a bSSFP sequence produces bright signals for both fatty tissues and fluids, which is a limitation of the current approach. This overlap prevents distinction between fat and fluid without additional imaging techniques.\u003c/p\u003e\u003cp\u003eOur current methods face several limitations. Eight out of eleven healthy subjects did not have a mammogram or clinical breast MRI for comparison. This is because those participants belonged to a younger age group who have not yet undergone breast screening. Hence, to facilitate evaluation, our three breast radiologists leveraged their expertise in interpreting clinical breast MRI scans. Nevertheless, this exploratory phase provided valuable insights into the potential of ULF imaging, paving the way for future refinement and standardization. Besides the issue of incomplete visualization of the chest wall, our preliminary study did not image the axilla, a crucial area for detecting breast cancers and nodal disease. Furthermore, a lower spatial resolution of 3 mm \u0026times; 3 mm \u0026times; 8 mm was applied to the 11 healthy participants to demonstrate the potential of ultra-low field breast MRI to clinicians while ensuring a reasonable scan time. The image resolution used for scanning the 11 healthy participants does not meet clinical standards for breast cancer screening, which require a spatial resolution of approximately 2 mm \u0026times; 2 mm \u0026times; 5 mm to effectively detect small tumors. Although higher spatial resolution was performed in three patients, this came at the cost of longer scan times. Notably, the 3D ULF MRI images allowed precise measurement of the cyst volume in the left breast of the patient with a benign mass. Ideally, both breasts and axilla should be imaged simultaneously at this target resolution within a ten-minute scan.\u003c/p\u003e\u003cp\u003eTo address these issues, developing RF coils capable of imaging both breasts simultaneously and including the axilla and chest wall in the field of view is essential. Our cost-effective coil design, which can be tailored to various sizes, aims to enhance the filling factor and thereby improve the SNR for each subject \u003csup\u003e\u003cspan citationid=\"CR55\" class=\"CitationRef\"\u003e55\u003c/span\u003e\u003c/sup\u003e. This approach could significantly reduce total exam time and bring us closer to meeting the clinical resolution requirements.\u003c/p\u003e\u003cp\u003eThe work presented here was acquired on our 6.5 mT ULF MRI system which is a configurable test bed system developed in our laboratory to perform preliminary research and optimization of breast cancer imaging techniques. For clinical applicability, enhancing the SNR is crucial, as it can be used to attain higher resolution, shorter scan time, or both. While our current results are based on a 6.5 mT system, operating at even moderately higher magnetic fields (B\u003csub\u003e0\u003c/sub\u003e) would significantly improve performance. For instance, increasing the magnetic field to a nominal 20 mT would boost the SNR by a factor of 5, given that the SNR is proportional to B\u003csup\u003e3/2 56\u003c/sup\u003e. This enhancement could allow us to obtain images 25 times faster while maintaining the same SNR.\u003c/p\u003e\u003cp\u003eMoreover, increasing the magnetic field to approximately 65 mT \u0026ndash; 10\u0026times; higher than our current setup \u0026ndash; would still keep the system cost-effective. This increase in field strength would provide a substantial boost in SNR, leading to dramatic reductions in imaging time and improvements in spatial resolution. Such advancements would bring us closer to achieving clinical standards for breast cancer imaging.\u003c/p\u003e\u003cp\u003eAt 1.5 T and 3 T, chemical-shift fat suppression is a necessary part of breast imaging. We note that the absolute chemical shift between fat and water decreases with decreasing field strength, making conventional fat suppression techniques more challenging. Previous work using NMR and NMR dispersion techniques observe that the T1 relaxation time of adipose tissue in the breast does not change with field strength, while the T1 relaxation time of fibroglandular tissues do change with field strength \u003csup\u003e\u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e44\u003c/span\u003e,\u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e45\u003c/span\u003e\u003c/sup\u003e. Thus, it may be possible to make a fat suppression technique that takes advantage of the T1 relaxation time differences with field strength (i.e., T1 dispersion).\u003c/p\u003e\u003cp\u003eExogenous injected contrast agents are typically used to increase the contrast between a tissue of interest and the surrounding tissue, and clinical breast MRI requires the use of contrast agents to identify breast tumors \u003csup\u003e\u003cspan additionalcitationids=\"CR58\" citationid=\"CR57\" class=\"CitationRef\"\u003e57\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR59\" class=\"CitationRef\"\u003e59\u003c/span\u003e\u003c/sup\u003e. However, there is concern about the long-term effects of repeated administration of MRI contrast agents such as gadolinium \u003csup\u003e\u003cspan citationid=\"CR60\" class=\"CitationRef\"\u003e60\u003c/span\u003e\u003c/sup\u003e. At low magnetic fields, however, gadolinium-based contrast agents do not improve the contrast of the image, in part because gadolinium is not magnetically saturated at low magnetic fields and thus does not increase the brightness of the image. Recent work highlights the possibilities of iron-oxide nanoparticles and superparamagnetic iron oxide nanoparticles (SPIONs) for use at low magnetic fields \u003csup\u003e\u003cspan citationid=\"CR61\" class=\"CitationRef\"\u003e61\u003c/span\u003e,\u003cspan citationid=\"CR62\" class=\"CitationRef\"\u003e62\u003c/span\u003e\u003c/sup\u003e. A possible benefit of iron-oxide based agents is their biocompatibility, and preliminary in vivo studies used ferumoxytol, an FDA-approved SPION-based treatment of iron deficiency anemia \u003csup\u003e\u003cspan citationid=\"CR63\" class=\"CitationRef\"\u003e63\u003c/span\u003e,\u003cspan citationid=\"CR64\" class=\"CitationRef\"\u003e64\u003c/span\u003e\u003c/sup\u003e. Contrast agents were not used in this preliminary study.\u003c/p\u003e\u003cp\u003eWith this perspective on low-field MRI physics, our initial results open up a range of exciting possibilities for non-contrast, ULF, breast MRI. A specially designed ULF MRI system could be adapted for various imaging orientations \u0026ndash; beyond the current prone position to include supine, sitting, or standing positions. Innovative magnet designs could further enhance portability, reduce costs, and enable integration into surgical suites or other settings where traditional high-field MRI systems (1.5 T and 3 T) are impractical or unsafe.\u003c/p\u003e\u003cp\u003eULF MRI systems have the potential to dramatically increase access to breast cancer screening. The absence of gadolinium-based contrast agents, elimination of compression, and the elimination of confined spaces could make screening more accessible and acceptable. Additionally, a radiation-free, easily accessible system would facilitate frequent imaging, allowing for close monitoring of disease progression or stability. This approach would enable us to identify which tumors are progressing and make informed decisions about treatment.\u003c/p\u003e\u003cp\u003eIn summary, our demonstration of ULF magnetic resonance breast imaging \u0026ndash; without the need for contrast agents or compression\u0026mdash;paves the way for a new, accessible option in breast cancer screening. This approach could become a valuable tool for approximately one eighth of the global population, potentially transforming the landscape of breast cancer detection and management.\u003c/p\u003e"},{"header":"Methods","content":"\u003cdiv id=\"Sec10\" class=\"Section2\"\u003e\u003ch2\u003eStudy Design\u003c/h2\u003e\u003cp\u003eThis prospective pilot study was performed to observe the capabilities of breast imaging at 6.5 mT. The observational study was granted institutional review board approval from the Office for Human Research Studies (protocol 21\u0026ndash;579) at the Dana-Farber/Harvard Cancer Center. All methods were performed in accordance with the relevant guidelines and regulations. Written informed consent was obtained from each participant.\u003c/p\u003e\u003cp\u003e11 healthy female participants (mean age, 35 years\u0026thinsp;\u0026plusmn;\u0026thinsp;13 years), two patients with a history of breast cancer (ages 51 and 58 years, respectively), and one 48-year-old patient with a benign mass were enrolled. Exclusion criteria were: pregnancy, breastfeeding, or inability to undergo MRI due to presence of an implanted or external MRI unsafe device or MR conditional device not meeting the conditions required for the scan. Participants had to be older than 20 and younger than 80 years old. The study also excluded individuals directly supervised by study investigators.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec11\" class=\"Section2\"\u003e\u003ch2\u003eImaging System\u003c/h2\u003e\u003cp\u003eImaging was performed on a custom-built electromagnetic MRI scanner, shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eA and previously described \u003csup\u003e\u003cspan citationid=\"CR46\" class=\"CitationRef\"\u003e46\u003c/span\u003e\u003c/sup\u003e. The scanner operates at a main field strength of 6.5 mT (Larmor frequency of 276.18 kHz). The magnetic field inhomogeneity measured over a 20 cm spherical region at isocenter is less than 10 Hz. Imaging gradients are produced by a biplanar gradient set capable of producing linear gradients of up to 1 mT/m in all three axes.\u003c/p\u003e\u003cp\u003eFor this study, the imaging bed was modified from its previous configuration for neuroimaging \u003csup\u003e\u003cspan citationid=\"CR46\" class=\"CitationRef\"\u003e46\u003c/span\u003e\u003c/sup\u003e to a breast imaging setup where the breast and breast RF coil are located at the isocenter of the scanner. Figure\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eB-D illustrates the imaging bed and dedicated RF coil designed to image a single breast. In order to achieve a good filling factor and thus a high SNR \u003csup\u003e\u003cspan citationid=\"CR55\" class=\"CitationRef\"\u003e55\u003c/span\u003e\u003c/sup\u003e, a close-fitting conical breast RF coil was designed. To evaluate RF coil homogeneity, the magnetic field was calculated using the Finite-Element-Method simulation (Ansys Maxwell, 2021, Ansys, Canonsburg, PA, USA). The simulated magnetic field was used to assess the field homogeneity within the breast volume and to determine the magnetic field fall-off beyond the physical end of the coil (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eE). The uniformity of the breast imaging region was also assessed using a homogeneous flexible phantom consisting of a latex balloon filled with deionized water. This MR phantom was placed inside the breast RF coil, and as seen in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eF, it occupied the entire imaging region-of-interest. The imaging protocol used to scan the MR phantom was the same as that of participant scanning protocol.\u003c/p\u003e\u003cp\u003eThe RF coil design was determined based on several factors. The conical coil shape was based on promising study results at higher field strengths \u003csup\u003e\u003cspan citationid=\"CR65\" class=\"CitationRef\"\u003e65\u003c/span\u003e\u003c/sup\u003e and adapted in size to enable imaging of larger breasts, based on the reported common female breast sizes in the US \u003csup\u003e\u003cspan citationid=\"CR66\" class=\"CitationRef\"\u003e66\u003c/span\u003e\u003c/sup\u003e. The coil height is 10 cm; its diameter at the base is 19 cm; and its diameter at the peak is 4 cm \u003csup\u003e\u003cspan additionalcitationids=\"CR68\" citationid=\"CR67\" class=\"CitationRef\"\u003e67\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR69\" class=\"CitationRef\"\u003e69\u003c/span\u003e\u003c/sup\u003e. The RF coil is uniformly wound on a conical supporting structure. This coil design is capable of imaging the whole breast and the chest wall to a depth of approximately 3 cm. Using this breast coil, one breast of all participants was imaged with participants in the prone position, as illustrated in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eC.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec12\" class=\"Section2\"\u003e\u003ch2\u003eMRI acquisition\u003c/h2\u003e\u003cp\u003eAn axial 3D balanced steady-state free precession (bSSFP) sequence was used in this study with a flip angle of 70 degrees, TE (echo time)/TR (repetition time) of 13 ms/26 ms, a matrix size of 64 \u0026times; 72 \u0026times; 21 and 50 averages. To accelerate the imaging process, an under-sampling factor of 70% was used. Depending on the evaluation criteria, for all healthy participants, the left breast was scanned with a voxel size of 3 mm \u0026times; 3 mm \u0026times; 8 mm, and total scan time was 21 minutes 36 seconds. For the three patients with either breast cancer history or benign mass, the spatial resolution was adjusted depending on the size of the breast. The patient with a history of invasive ductal carcinoma and papillary carcinoma in the subareolar region of the right breast was scanned for 30 minutes with a spatial resolution of 2 mm \u0026times; 2 mm \u0026times; 6 mm. The patient with a history of invasive lobular carcinoma and the patient with a cystic mass in their left breasts were scanned for 45 minutes with a spatial resolution of 2 mm \u0026times; 2 mm \u0026times; 4 mm. Given the scan duration, the study was limited to imaging one breast. No contrast agents were used.\u003c/p\u003e\u003cp\u003eImages were reconstructed in MATLAB (Natick, MA, USA) using inverse fast Fourier transform (IFFT) with the under-sampled region zero-filled in k-space. Images were converted into DICOM format using the MATLAB function dicomwrite. No data-driven Artificial Intelligence (AI) or other machine learning-based methods were used in the image acquisition or reconstruction.\u003c/p\u003e\u003cp\u003eThe images of all 11 healthy participants were reviewed by three board-certified breast radiologists (M.A.S., L.R.L., and J.C.V.C.) with 13, 9, and 3 years of experience reading breast MRI. The readers reviewed the evaluation criteria; however, due to the limited data of this pilot study, no additional images were used to train the readers. Images were viewed in DICOM format using 3D Slicer \u003csup\u003e\u003cspan citationid=\"CR70\" class=\"CitationRef\"\u003e70\u003c/span\u003e\u003c/sup\u003e. The visibility of the following features in the breast was assessed: visibility of the breast outline, visibility of the fibroglandular tissue (FGT) compared to intramammary adipose tissue, demarcation of the nipple areolar complex (NAC), and visualization of the pectoralis muscle (chest wall). Visibility of these features was assessed using a 5-point Likert scale (1 \u0026ndash; not at all visible, 2 \u0026ndash; barely visible, 3 \u0026ndash; clearly visible but blurred, 4 \u0026ndash; clearly visible and sharp, 5 \u0026ndash; clearly visible and very sharp). Breast tissue pattern (density) was assessed using four categories: fatty, scattered FGT, heterogeneous FGT, and extreme FGT. Images were also evaluated for motion artifacts.\u003c/p\u003e\u003cp\u003eThree of the 11 healthy participants had screening mammograms available for comparison to the ULF MRI. The screening mammograms were reviewed by one board-certified radiologist (M.A.S.) with 13 years of experience with breast MRI. The radiologist noted the breast tissue pattern and visibility of key breast features on the ULF MRI and the x-ray mammogram.\u003c/p\u003e\u003cp\u003eFor the three patients with either breast cancer history or benign mass, the ULF MRI and any clinical imaging were reviewed by one board-certified radiologist (M.A.S.) with 13 years of experience with breast MRI. The radiologist noted the breast tissue pattern, visibility of key breast features, and any clinical findings across all images.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec13\" class=\"Section2\"\u003e\u003ch2\u003eStatistical Analysis\u003c/h2\u003e\u003cp\u003eInter-reader agreement was assessed by computing Fleiss\u0026rsquo; kappa among three readers\u0026rsquo; feature visibility assessments. Due to the novelty of these images, i.e., they were new to all readers, and the limited data set, which did not allow for proper training of the readers, the readers were not \u0026ldquo;calibrated\u0026rdquo; to each other, as they are when reading clinical MRI. As a result, the 5-point scale was revised to a binary scale to assess whether or not a feature was visible (1 \u0026ndash; not at all visible, 2 or greater \u0026ndash; visible). All statistical analyses were performed using IBM SPSS Statistics for Windows, version 26.0. (IBM Corp., Armonk, NY, USA).\u003c/p\u003e\u003c/div\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAcknowledgments\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors would like to thank Darrah Bowden for her invaluable assistance and perspective on the breast imaging configuration. MSR dedicates this work to the memory of Christina Pfeifer Mattig.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNational Institutes of Health grant 1R21CA267315 (KEK, MSR)\u003c/p\u003e\n\u003cp\u003eKiyomi and Ed Baird MGH Research Scholar award (MSR)\u003c/p\u003e\n\u003cp\u003eGerman-American\u0026nbsp;Fulbright Commission (FKL)\u003c/p\u003e\n\u003cp\u003eNational Institute of Standards and Technology (KEK, SEO)\u003c/p\u003e\n\u003cp\u003eNIST-PREP 70NANB18H006 from U.S. Department of Commerce (SEO)\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor contributions:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eConceptualization: KEK, MSR\u003c/p\u003e\n\u003cp\u003eMethodology: SS, NK, FKL, MAS, TPPH, SEO\u003c/p\u003e\n\u003cp\u003eInvestigation: SS, NK, FKL, MAS, LRL, JVCV, TPPH, MSR\u003c/p\u003e\n\u003cp\u003eVisualization: SS, NK, MAS, JVCV, SEO, KEK, MSR\u003c/p\u003e\n\u003cp\u003eSupervision: SY, TRB, KEK, MAS, MSR\u003c/p\u003e\n\u003cp\u003eWriting\u0026mdash;original draft: SS, NK, KEK, MSR\u003c/p\u003e\n\u003cp\u003eWriting\u0026mdash;review \u0026amp; editing: SS, NK, FKL, MAS, LRL, JVCV, TPPH, SEO, SY, TRB, KEK, MSR\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interests:\u003c/strong\u003e MSR is a founder and equity holder of Hyperfine, Inc. MSR is a consultant and equity holder in DeepSpin GmbH. All other authors declare no conflicts.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eData and materials availability:\u003c/strong\u003e All data generated or analyzed during the study are available in the main text.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eNIST Disclaimer:\u003c/strong\u003e Certain commercial equipment, instruments, or materials are identified in this paper in order to specify the experimental procedure adequately. \u0026nbsp;Such identification is not intended to imply recommendation or endorsement by NIST, nor is it intended to imply that the materials or equipment identified are necessarily the best available for the purpose.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eUnited Nations Department of Economic \u0026amp; Social Affairs Population Division. World Population Prospects 2024, Online Edition. 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Imaging\u003c/em\u003e. \u003cb\u003e30\u003c/b\u003e, 1323\u0026ndash;1341 (2012).\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"},{"header":"Tables","content":"\u003cp\u003eTable 1 is available in the Supplementary Files section.\u003c/p\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"scientific-reports","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"scirep","sideBox":"Learn more about [Scientific Reports](http://www.nature.com/srep/)","snPcode":"","submissionUrl":"","title":"Scientific Reports","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Scientific Reports","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"","lastPublishedDoi":"10.21203/rs.3.rs-6882799/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-6882799/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eBreast cancer screening is essential for reducing mortality, yet current modalities face significant barriers, including high costs, limited accessibly, and reliance on ionizing radiation, which leads many women to forego regular screenings. Magnetic resonance imaging (MRI) offers a radiation-free alternative, but its adoption for screening is constrained by cost, availability, and the need for IV contrast administration. In this study, we demonstrate the feasibility of ultra-low field (ULF) unilateral breast MRI for screening applications. ULF MRI was performed on 11 healthy women in a prone position. Three breast radiologists could reliably delineate breast outlines and distinguish fibroglandular tissue (FGT) from adipose tissue. Tissue patterns (fatty, scattered, heterogeneous, and extreme FGT) were consistently identified. In two patients with prior breast cancer, ULF MRI effectively eliminated magnetic susceptibility artifacts from surgical biopsy clips and in one of these patients revealed post-surgical changes following lumpectomy. Additionally, a benign mass was detected in another patient. These findings highlight ULF breast MRI as a potential low-cost, accessible, and contrast-free alternative for breast cancer screening, with the promise of expanding early detection to underserved populations globally.\u003c/p\u003e","manuscriptTitle":"Breast imaging with ultra-low field MRI","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-07-25 06:41:12","doi":"10.21203/rs.3.rs-6882799/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2025-09-04T14:44:18+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-09-04T08:38:29+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"231532705285027400096554509916015415841","date":"2025-08-15T12:59:48+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-08-04T20:04:04+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"133336720053917838435872912428406642140","date":"2025-07-25T10:26:16+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-07-22T16:16:40+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-07-22T12:44:58+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"","date":"2025-07-16T17:52:16+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-06-18T17:17:31+00:00","index":"","fulltext":""},{"type":"submitted","content":"Scientific Reports","date":"2025-06-18T17:14:06+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"scientific-reports","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"scirep","sideBox":"Learn more about [Scientific Reports](http://www.nature.com/srep/)","snPcode":"","submissionUrl":"","title":"Scientific Reports","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Scientific Reports","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"42303003-38bf-4393-a06f-eda84518041f","owner":[],"postedDate":"July 25th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[{"id":51979136,"name":"Physical sciences/Engineering/Biomedical engineering"},{"id":51979137,"name":"Health sciences/Health care/Medical imaging/Magnetic resonance imaging"}],"tags":[],"updatedAt":"2026-02-23T16:04:43+00:00","versionOfRecord":{"articleIdentity":"rs-6882799","link":"https://doi.org/10.1038/s41598-026-37130-9","journal":{"identity":"scientific-reports","isVorOnly":false,"title":"Scientific Reports"},"publishedOn":"2026-02-19 15:57:10","publishedOnDateReadable":"February 19th, 2026"},"versionCreatedAt":"2025-07-25 06:41:12","video":"","vorDoi":"10.1038/s41598-026-37130-9","vorDoiUrl":"https://doi.org/10.1038/s41598-026-37130-9","workflowStages":[]},"version":"v1","identity":"rs-6882799","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-6882799","identity":"rs-6882799","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}