Comparison of Supine and Prone Positions for Dental MRI with a Microscopy Coil: Image Quality and Patient Burden in Healthy Volunteers

Comparison of Supine and Prone Positions for Dental MRI with a Microscopy Coil: Image Quality and Patient Burden in Healthy Volunteers | 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 Research Article Comparison of Supine and Prone Positions for Dental MRI with a Microscopy Coil: Image Quality and Patient Burden in Healthy Volunteers Toshiyuki Zaike, Shinya Kotaki, Hitomi Nakama, Yoshiko Ariji, and 1 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8596112/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Objectives This study aimed to evaluate the clinical feasibility of dental magnetic resonance imaging (MRI) using a microscopy coil by comparing imaging positions in healthy volunteers. Methods Twenty-six healthy volunteers underwent dental MRI in supine and prone positions using a 47 mm microscopy coil on a 3.0T system. T1-weighted (T1W), T2-weighted (T2W), and proton density-weighted (PDW) sequences were acquired. Participant-reported burden was assessed using a 10-point scale. Image quality was evaluated using a 4-point scale for sharpness, artifact, perceived signal-to-noise ratio (SNR), and overall quality. SNR and contrast-to-noise ratio (CNR) were calculated from 1 mm 2 regions of interest in dental pulp, inferior alveolar neurovascular bundle, and bone marrow. Statistical analyses included the Wilcoxon signed-rank test, Fisher's exact test, and paired t-test. Results Participant-reported burden was lower in the supine position (1.7 ± 1.1) than in the prone (4.7 ± 2.1). Visual assessments demonstrated superior image quality in supine across all sequences. The proportion of non-diagnostic images was higher in the prone position: T1W (50% vs. 19%), T2W (46% vs. 4%), and PDW (38% vs. 8%). SNR and CNR showed no differences between positions. Image quality degraded with prolonged examination time regardless of position. Conclusions The supine position demonstrated lower subjective burden, better visual image quality, and a lower rate of non-diagnostic images compared with the prone position. Image quality was optimal when MRI was performed early in the examination sequence. Therefore, the supine position is more appropriate for dental MRI using a microscopy coil. Magnetic Resonance Imaging Dental Pulp Diagnostic Imaging Signal-To-Noise Ratio Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 1. Introduction In dental imaging, intraoral radiography, panoramic radiography, and dental cone-beam computed tomography (CBCT) are routinely employed for clinical diagnosis. However, these conventional modalities have inherent limitations in soft tissue visualization due to their reliance on X-ray attenuation, and CT-based techniques involve concerns regarding radiation exposure [ 1 ]. Dental magnetic resonance imaging (dental MRI) has recently emerged as a promising alternative modality, offering superior soft tissue contrast for visualizing the periodontal structures, the dental pulp and the periodontal ligament, without the use of ionizing radiation [ 2 , 3 ]. Nevertheless, the clinical implementation of dental MRI faces technical challenges, particularly in achieving the high spatial resolution (< 1 mm) required for detailed evaluation of dental structures [ 4 ]. Several approaches have been investigated to enhance the spatial resolution of dental MRI, which is essential for the detailed evaluation of dental structures. These include the use of high-field-strength systems and the development of dedicated receiver coils with improved signal-to-noise ratio (SNR) [ 5 – 12 ]. Among these strategies, coil optimization has emerged as a particularly promising approach, as dedicated surface coils and intraoral coils have demonstrated superior SNR and spatial resolution compared to standard head and neck coils [ 6 – 12 ]. Microscopy coils, which have been successfully employed in other medical imaging applications, represent a notable candidate for dental MRI [ 13 ]. The anatomical positioning of teeth and periodontal tissues directly beneath the buccinator muscle places them within the optimal imaging range of microscopy coils, potentially enabling high-resolution visualization of dental structures [ 14 ]. These previous studies, although promising, did not comprehensively evaluate the degree of patient burden associated with imaging positions such as supine and prone positions and did not consider oral radiologist image quality assessments. Therefore, this study aimed to evaluate the burden related to imaging positions (subjective evaluation of participant burden), visibility of the teeth and periodontal tissues (visual image quality assessment by an oral radiologist and an endodontist), and SNR and contrast-to-noise ratio (CNR) (physical image evaluation) by imaging the teeth and periodontal tissues of healthy volunteers using a microscopy coil and a 3.0T MRI system with T1-weighted (T1W), T2-weighted (T2W), and proton density-weighted (PDW) sequences, thereby determining the more appropriate subject positioning for dental MRI using a microscopy coil. 2. Materials and Methods 2 − 1. Equipment Used A 3.0T MRI system, Ingenia Elition (Release ver5.7; Philips Medical Systems, Best Netherlands) and a 47 mm microscopy coil (Philips Medical Systems, Best Netherlands) were used. Imaging was performed using a MRI system. Statistical testing was performed using EZR (ver1.54; Saitama Medical Center, Jichi Medical University, Saitama, Japan) and Microsoft Excel 2016 (ver. 2504; Microsoft Way, Redmond, WA). This study was approved by our Medical Ethics Committee (approval number: 11238). 2–2. Volunteer Participants and Imaging Conditions The volunteer participants were 26 healthy volunteers (1 male, 25 females, aged 20–25 years, mean age 20.8 years) who underwent dental MR in both the supine and prone positions between September 2024 and January 2025 (Fig. 1 a-d). The microscopy coil was placed on the skin surface corresponding to the root apex of the left mandibular first molar and fixed with surgical tape. Imaging was performed in the supine position facing upward and in the prone position with the head turned to the right so that the left mandible contacted the floor surface. The order of the positions was alternated between participants, with some imaged from supine to prone and others from prone to supine. The imaging conditions used the same protocol for both the supine and prone positions, considering parameters from previous studies, and acquiring T1W, T2W, and PDW images [ 14 ] (Table 1). For all volunteers, the imaging sequence began with PDW, which excels at visualizing anatomical structures, followed by T1W and T2W in that order. The imaging sequences were selected based on the comparative tissue contrast between T1W and T2W, which excel at visualizing inferior alveolar neurovascular bundle (IAN) and dental pulp, respectively, and considering comparisons with previous studies. PDW was chosen for each region due to PDW's superior ability to depict anatomical structures. 2–3. Subjective Evaluation of Imaging Positions Volunteer participants who completed imaging evaluated the burden of each position (supine and prone) using a 10-point scale ranging from 1 (no discomfort) to 10 (maximum discomfort) [ 15 ]. Mean scores and standard deviations were calculated for both positions, and statistical significance was assessed using the Wilcoxon signed-rank test with a significance level of p < 0.05. 2–4. Visual Evaluation by Observers 2-4-1. Visual Image Quality Assessment by Observers Visual evaluation was performed by two observers, an oral radiologist with 13 years of clinical experience (Observer A) and an endodontist with 12 years of clinical experience (Observer B), on T1W, T2W, and PDW images obtained from volunteer participants in the supine and prone positions. Four evaluation items were established for each image series: "Sharpness," "Artifacts," " Perceived SNR," and "Image quality," evaluated on a scale of 1 = non-diagnostic, 2 = limited but interpretable, 3 = diagnostic with some limitations, 4 = fully diagnostic. Visual evaluation was performed twice, with the first and second evaluations separated by at least 1 week. The images were presented in random order, and each was evaluated independently. The mean scores and standard deviations for the supine and prone positions were calculated for each evaluation item, and statistical significance was assessed using the Wilcoxon signed-rank test (statistical significance set at p < 0.05). 2-4-2. Effect of Image Order on Image Quality To evaluate the effect of the imaging sequence order, comparisons were made between groups imaged from supine to prone and groups imaged from prone to supine, mean scores and standard deviations were calculated, and statistical significance was determined. The Wilcoxon signed-rank test was used, with statistical significance set at p < 0.05. 2-4-3. Observer Agreement and Proportion of Non-Diagnostic Images Weighted κ values were calculated to assess intra-observer agreement (between the first and second evaluations of each observer) and inter-observer agreement. κ values were interpreted according to the following criteria: poor (< 0.00), slight (0.00-0.20), fair (0.21–0.40), moderate (0.41–0.60), substantial (0.61–0.80), and almost perfect (0.81-1.00) [ 16 ]. Additionally, to evaluate the feasibility of obtaining diagnostic-quality images in each position, the proportion of cases rated as non-diagnostic (score 1 by both observers for all four evaluation criteria: sharpness, artifacts, perceived SNR, and image quality) was compared between supine and prone positions for each sequence (T1W, T2W, PDW). Fisher's exact test was used for statistical comparison, with significance set at p < 0.05. 2–5. SNR and CNR Evaluation Based on the visual evaluation results, volunteer data with an average score of 1 (non-diagnostic) in all four evaluation items were excluded, and the SNR of the dental pulp, the IAN, the bone marrow, and CNR relatives to dentin were calculated (11 cases for T1W, 14 cases for T2W, and 15 cases for PDW). Regions of interest (ROI) of 1 mm² were set on the dental pulp, IAN, bone marrow, and dentin in the obtained image data to acquire the mean signal values and standard deviations for SNR and CNR calculations [ 17 ]. $$\:{SNR}_{DP}=\frac{{Average\:Mean}_{DP}}{{SD}_{DP}}$$ $$\:{SNR}_{IAN}=\frac{{Average\:Mean}_{IAN}}{{SD}_{IAN}}$$ $$\:{SNR}_{BM}=\frac{{Average\:Mean}_{BM}}{{SD}_{BM}}$$ Where SNR DP , SNR IAN , and SNR BM are the SNRs of dental pulp, IAN, and bone marrow, respectively. Average Mean DP , Mean IAN , and Average Mean BM are the mean signal values of the dental pulp, IAN, and bone marrow, respectively. where SD DP , SD IAN , and SD BM are the standard deviations of the dental pulp, IAN, and bone marrow, respectively [ 17 ]. $$\:{CNR}_{DP}=\:\frac{{Average\:Mean}_{DP}-\:{Average\:Mean}_{DT}}{{SD}_{DP}}$$ $$\:{CNR}_{IAN}=\:\frac{{Average\:Mean}_{IAN}-\:{Average\:Mean}_{DT}}{{SD}_{IAN}}$$ $$\:{CNR}_{BM}=\:\frac{{Average\:Mean}_{BM}-\:{Average\:Mean}_{DT}}{{SD}_{BM}}$$ Where CNR DP , CNR IAN , and CNR BM are the CNRs of dental pulp, IAN, and bone marrow, respectively. The Average Mean DT is the mean signal value of the dentin. The statistical significance between the supine and prone positions was determined for each anatomical site and sequence. The Kolmogorov–Smirnov test was performed to confirm normality, and the F-test was used to confirm equal variance. For data following a normal distribution, paired t-tests were used, with statistical significance set at p < 0.05. For data that did not follow a normal distribution, the Wilcoxon signed-rank test was used, with statistical significance set at p < 0.05. 3. Results 3 − 1. Volunteer Participant-Reported Subjective Evaluation of Imaging Positions Figure 2 shows the results of the participant-reported evaluation scores for burden according to imaging position differences. The mean values and standard deviations of participant-reported evaluation scores for supine and prone positions were 1.7 (SD ± 1.1) and 4.7 (SD ± 2.1), respectively. There was a significant difference between the supine and prone positions (p < 0.01). 3 − 2. Visual Evaluation by Observers 3-2-1. Visual Image Quality Assessment by Observers Figure 3 a-c shows the results of the visual evaluation. For T1W, the mean scores and standard deviations for supine position in sharpness, artifacts, perceived SNR, and image quality were 2.4 (SD ± 1.0), 2.3 (SD ± 1.1), 2.3 (SD ± 1.1), and 2.4 (SD ± 1.0), respectively, while for prone position they were 1.8 (SD ± 1.0), 1.6 (SD ± 1.0), 1.6 (SD ± 0.9), and 1.8 (SD ± 1.0), respectively (Fig. 3 a). For T2W, the mean scores and standard deviations for supine position in sharpness, artifacts, perceived SNR, and image quality were 2.7 (SD ± 1.0), 2.6 (SD ± 1.1), 2.6 (SD ± 1.1), and 2.8 (SD ± 1.0), respectively, while for prone position they were 1.8 (SD ± 0.9), 1.6 (SD ± 0.9), 1.7 (SD ± 0.9), and 1.7 (SD ± 0.9), respectively (Fig. 3 b). For PDW, the mean scores and standard deviations for supine position in sharpness, artifacts, perceived SNR, and image quality were 2.9 (SD ± 1.1), 2.6 (SD ± 1.1), 2.7 (SD ± 1.1), and 2.9 (SD ± 1.1), respectively, while for prone position they were 2.0 (SD ± 1.1), 1.8 (SD ± 1.0), 1.8 (SD ± 1.0), and 1.9 (SD ± 1.0), respectively (Fig. 3 c). All evaluation items showed p < 0.01, indicating significant differences between the supine and prone positions. 3-2-2. Effect of Imaging Order on Image Quality Figure 4 a-f shows the visual evaluation score results considering the order of the imaging positions. For T1W in the group imaged from supine to prone, the mean scores and standard deviations for supine position in sharpness, artifacts, perceived SNR, and image quality were 2.8 (SD ± 0.8), 2.7 (SD ± 0.9), 2.7 (SD ± 0.9), and 2.8 (SD ± 0.8), respectively, while for prone position they were 1.5 (SD ± 0.8), 1.5 (SD ± 0.9), 1.5 (SD ± 0.7), and 1.6 (SD ± 0.8), respectively (Fig. 4 a). All evaluation items showed p < 0.01, indicating significant differences between the supine and prone positions. For T1W in the group imaged from prone to supine, the mean scores and standard deviations for supine position in sharpness, artifacts, perceived SNR, and image quality were 2.0 (SD ± 1.0), 1.9 (SD ± 1.0), 1.9 (SD ± 0.9), and 2.0 (SD ± 1.0), respectively, while for prone position they were 2.0 (SD ± 1.0), 1.8 (SD ± 0.9), 1.8 (SD ± 0.9), and 2.0 (SD ± 1.1), respectively (Fig. 4 b). No statistically significant differences were observed between the supine and prone positions for any of the evaluation items. For T2W in the group imaged from supine to prone, the mean scores and standard deviations for supine position in sharpness, artifacts, perceived SNR, and image quality were 3.0 (SD ± 0.8), 2.9 (SD ± 1.0), 2.9 (SD ± 0.9), and 3.1 (SD ± 0.9), respectively, while for prone position they were 1.6 (SD ± 0.9), 1.5 (SD ± 0.9), 1.5 (SD ± 0.7), and 1.6 (SD ± 0.9), respectively (Fig. 4 c). All evaluation items showed p < 0.01, indicating significant differences between the supine and prone positions. For T2W in the group imaged from prone to supine, the mean scores and standard deviations for supine position in sharpness, artifacts, perceived SNR, and image quality were 2.5 (SD ± 0.9), 2.3 (SD ± 1.0), 2.4 (SD ± 1.0), and 2.5 (SD ± 0.9), respectively, while for prone position they were 1.9 (SD ± 0.7), 1.7 (SD ± 0.7), 1.8 (SD ± 0.8), and 1.9 (SD ± 0.7), respectively (Fig. 4 d). All evaluation parameters showed p < 0.05, indicating statistically significant differences between the supine and prone positions. For PDW in the group imaged from supine to prone, the mean scores and standard deviations for supine position in sharpness, artifacts, perceived SNR, and image quality were 3.4 (SD ± 0.8), 3.1 (SD ± 1.0), 3.1 (SD ± 1.0), and 3.4 (SD ± 0.8), respectively, while for prone position they were 1.7 (SD ± 1.0), 1.6 (SD ± 0.9), 1.6 (SD ± 0.9), and 1.6 (SD ± 0.8), respectively (Fig. 4 e). All evaluation items showed p < 0.01, indicating significant differences between the supine and prone positions. For PDW in the group imaged from prone to supine, the mean scores and standard deviations for supine position in sharpness, artifacts, perceived SNR, and image quality were 2.5 (SD ± 0.9), 2.2 (SD ± 1.0), 2.3 (SD ± 0.9), and 2.4 (SD ± 1.0), respectively, while for prone position they were 2.4 (SD ± 1.0), 2.0 (SD ± 0.9), 2.1 (SD ± 0.9), and 2.3 (SD ± 0.9), respectively (Fig. 4 f). No statistically significant differences were observed between the supine and prone positions for any of the evaluation items. 3-2-3. Observer Agreement Observer A's agreement between first and second evaluations was moderate to substantial (κ value of 0.44–0.65), and Observer B's agreement between first and second evaluations was moderate to substantial (κ value of 0.54–0.75). Agreement between Observer A and B was fair to moderate (κ value of 0.30–0.48). 3-2-4. Proportion of Non-Diagnostic Images The number of cases with a score of 1 assigned by both observers for all evaluation items was significantly higher in the prone position than in the supine position across all sequences: T1W (13/26 vs. 5/26, p = 0.04), T2W (12/26 vs. 1/26, p < 0.001), and PDW (10/26 vs. 2/26, p = 0.019) (Table 2). This substantial difference in the proportion of non-diagnostic images indicates that the prone position presented greater challenges for obtaining diagnostic-quality images compared with the supine position. 3–3. SNR and CNR Evaluation 3-3-1. SNR Measurements For T1W, the mean scores and standard deviations of SNR for the dental pulp, the IAN, and the bone marrow in supine position were 8.6 (SD ± 3.2), 8.0 (SD ± 2.8), and 25.3 (SD ± 6.6), respectively, while for prone position they were 8.8 (SD ± 2.5), 7.0 (SD ± 2.3), and 23.8 (SD ± 6.1), respectively. For T2W, the mean scores and standard deviations of SNR for the dental pulp, the IAN, and the bone marrow in supine position were 9.5 (SD ± 3.4), 12.3 (SD ± 4.7), and 24.1 (SD ± 9.4), respectively, while for prone position they were 10.1 (SD ± 4.4), 11.1 (SD ± 4.2), and 24.9 (SD ± 12.1), respectively. For PDW, the mean scores and standard deviations of SNR for the dental pulp, the IAN, and the bone marrow in supine position were 10.4 (SD ± 5.4), 9.7 (SD ± 3.7), and 19.8 (SD ± 5.5), respectively, while for prone position they were 9.4 (SD ± 3.7), 8.3 (SD ± 2.9), and 17.3 (SD ± 5.1), respectively. No statistically significant differences were found between the supine and prone positions for any of the sequences or evaluation items. 3-3-2. CNR Measurements For T1W, the mean scores and standard deviations of CNR for the dental pulp, the IAN, and the bone marrow in supine position were 6.9 (SD ± 2.7), 6.8 (SD ± 2.7), and 22.7 (SD ± 5.9), respectively, while for prone position they were 7.1 (SD ± 2.2), 5.6 (SD ± 2.0), and 22.5 (SD ± 5.8), respectively. For T2W, the mean scores and standard deviations of CNR for the dental pulp, the IAN, and the bone marrow in supine position were 8.8 (SD ± 3.4), 11.2 (SD ± 4.4), and 23.2 (SD ± 9.2), respectively, while for prone position they were 9.3 (SD ± 4.2), 9.4 (SD ± 3.9), and 23.7 (SD ± 11.7), respectively. For PDW, the mean scores and standard deviations of CNR for the dental pulp, the IAN, and the bone marrow in supine position were 9.4 (SD ± 5.0), 8.4 (SD ± 3.3), and 18.8 (SD ± 5.2), respectively, while for prone position they were 8.6 (SD ± 3.5), 6.8 (SD ± 2.5), and 16.3 (SD ± 4.8), respectively. No statistically significant differences were found between the supine and prone positions for any of the sequences or evaluation items. 4. Discussion In this study, using a Microscopy Coil and a 3.0T MRI system, we acquired T1W, T2W, and PDW images of the teeth and the periodontal tissues of healthy volunteers. We evaluated the participant-reported subjective burden ratings in the supine and prone positions, along with visual image quality assessments by an oral radiologist and an endodontist, including SNR and CNR. Prone imaging of the mandible using flex coils have been previously reported, demonstrating improved facial motion suppression and spatial resolution through better coil adherence in the prone position [ 18 ]. However, those studies did not comprehensively assess case numbers, patient burden, or overall image quality. This study obtained data on participant-reported subjective burden levels during dental MRI in the supine and prone positions, presenting foundational data for the clinical application. Regarding patient burden, it has been reported that factors such as claustrophobia, patient medical history, and examination equipment influence the experience [ 19 , 20 ]. In volunteer participant-reported subjective evaluation of imaging position burden, the supine position showed significantly less subjective burden compared to the prone position (p < 0.01). This suggests that the supine position is prioritized for imaging in dental MRI. While the prone position is recommended for breast and lung imaging to reduce respiratory motion effects for imaging sites not directly affected by respiration, high tolerance of the supine position has been reported [ 21 , 22 ]. Flex coils are made of soft materials, unlike the hard materials used in microscopy coils, which may cause varying levels of discomfort when placed on the facial region. The supine position, by contrast, generally allows for easier breathing and better position maintenance. In visual evaluations by an oral radiologist and an endodontist, supine images scored significantly higher than prone images across all sequences (T1W, T2W, PDW) and evaluation items (sharpness, artifacts, perceived SNR, image quality) (p < 0.01). This aligns with the burden evaluation findings, suggesting that motion artifacts due to difficulty in maintaining position contribute to reduced image quality. PDW images scored higher than other sequences, likely due to PDW’s higher SNR compared with other sequences, resulting in superior visual assessments [ 14 ]. When imaging was performed from supine to prone, the supine position was significantly superior to the prone position across all sequences and evaluation items. Conversely, when imaging was performed from prone to supine, no significant differences were observed between the two positions for T1W and PDW. This suggests that with longer imaging times, positional maintenance becomes challenging even in the supine position, diminishing the quality differences between supine and prone images due to motion artifacts. These findings indicate that dental MR imaging would benefit from being performed early in the examination. For example, when both overall jawbone assessment (using head and neck coils) and localized dental imaging are required, performing dental MRI first may yield higher-quality images. When imaging was performed first in the supine position and then in the prone position, all quality metrics demonstrated significant superiority of the supine position (p < 0.01). However, when the order was reversed (first prone and then supine), no significant differences were observed for T1W and PDW sequences (Fig. 4 b, f). This pattern suggests that patient fatigue and difficulty maintaining position increase with examination duration, regardless of the specific position adopted. The later-acquired images showed degraded quality in both positions, indicating that the timing of acquisition is as important as the choice of position itself. Physical evaluations of SNR and CNR revealed no significant differences between the supine and prone positions for any sequence in images of sufficient diagnostic quality. However, the proportion of non-diagnostic images (all evaluation items scored 1 by both observers) was significantly higher in the prone position across all sequences: T1W (13/26 vs. 5/26, p = 0.04), T2W (12/26 vs. 1/26, p < 0.001), and PDW (10/26 vs. 2/26, p = 0.02). This substantial difference represents a critical practical disadvantage of the prone position, as approximately half of prone acquisitions failed to produce diagnostic-quality images compared with less than 20% in the supine position. The absence of significant SNR/CNR differences among the remaining diagnostic-quality images suggests that intrinsic signal intensity changes due to imaging position are minimal when motion artifacts are controlled. The fundamental difference between positions lies in the feasibility of maintaining sufficient positional stability to acquire diagnostic images. Therefore, the image quality differences observed in visual assessments are primarily attributable to motion artifacts and difficulty maintaining position rather than inherent differences in coil-tissue coupling or signal characteristics [ 23 , 24 ]. This suggests that intrinsic signal intensity changes due to imaging position are minimal, and that the image quality differences observed in visual assessments are primarily attributable to motion artifacts. In the supine position, the tongue moves toward the pharynx under gravity, increasing the distance from the dentition and reducing motion effects. Conversely, in the prone position, the tongue is closer to the dentition, potentially increasing motion-related artifacts. Therefore, position selection should prioritize positional maintenance, stability, and patient comfort over physical signal intensity. T1W had more non-diagnostic cases, possibly because the echo spacing—set to match other sequences—minimized motion artifact effects from this parameter. T1W generally yields lower visual evaluation scores due to reduced pulp signal compared with T2W and PDW. Collectively, these findings suggest that the supine position is preferable for dental MR imaging. The relatively low interobserver agreement rate of 0.30–0.48 can be attributed to two main factors. First, endodontists assigned substantially lower scores (score 1) compared with oral radiologists, which likely reflects their different levels of familiarity with dental MRI. While oral radiologists routinely interpret MRI studies, endodontists primarily rely on conventional intraoral radiographs and dental CBCT for clinical decision-making, which limits their exposure to characteristics of MRI images [ 25 ]. Improving inter-observer agreement will require a multifaceted approach: assessments from a larger pool of evaluators with comparable experience levels. A standardized interpretation protocol must be developed before dental MRI can be reliably implemented in clinical practice. This study has several limitations that warrant consideration. The volunteer cohort consisted exclusively of individuals in their 20s, which limits the generalizability of the findings of our burden assessments. Older patients and those with facial disorders often experience greater difficulty maintaining stable positions during prolonged examinations, and their inclusion would likely reveal more pronounced tolerance issues and potentially higher rates of motion artifacts. Additionally, the non-randomized sequence order may have introduced systematic differences in motion artifact patterns between early and late acquisitions, as evidenced by our finding that image quality degraded regardless of position when imaging was performed later in the examination. Finally, our SNR and CNR measurements were derived from images containing mild motion artifacts (visual scores of 2 or 3), which may not accurately reflect the theoretical physical image quality achievable under ideal conditions (Fig. 5 a-f). While eliminating motion artifacts in volunteer studies remains challenging, future technical developments should prioritize reducing acquisition times to minimize their impact. 5. Conclusion This study evaluated imaging positions for dental MRI using a microscopy coil and a 3.0T MRI system by assessing participant burden, image quality, and SNR/CNR in healthy volunteers. The supine position demonstrated significant advantages over the prone position in subjective burden and visual image quality, with a lower rate of non-diagnostic images. Image quality was optimal when dental MRI was performed early in the examination sequence. These findings demonstrate that the supine position is the more appropriate imaging position for dental MRI using a microscopy coil. Declarations Ethical Approval All procedures involving human participants in this study were performed in accordance with the ethical standards of the responsible committee on human experimentation (institutional and national levels) and the Declaration of Helsinki of 1975, as revised in 2024. Consent to Participate Informed consent was obtained from all individual participants included in the study. Funding and Competing Interests The authors did not receive support from any organization for the submitted work. The authors have no relevant financial or non-financial interests to disclose. Author Contribution T. Z. conceived and designed the study, performed experiments, analyzed data, created figures and tables, and wrote the original draft.S. K. conceived and designed the study, evaluated images, and wrote the original draft.H. N. evaluated image.Y. A. provided device administrator and edited the manuscript.S. S. revised the figures and edited the manuscript. 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Reproduction of motion artifacts for performance analysis of prospective motion correction in MRI. Magn Reson Med. 2014;71:182–90. https://doi.org/10.1002/mrm.24645 . Nixdorf DR, Greiser A, Hayes C, Gaalaas L, Groenke BR, Fuglsig JMDCES et al. Comparison of a 0.55 T dental-dedicated magnetic resonance imaging system with a 1.5 T system in evaluation of the temporomandibular joint regarding subjective image quality assessment and rater agreement. Oral Surgery, Oral Medicine, Oral Pathology and Oral Radiology. 2025;140:113–24. https://doi.org/10.1016/j.oooo.2025.02.011 Additional Declarations No competing interests reported. Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. 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09:44:54","extension":"xml","order_by":35,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":86747,"visible":true,"origin":"","legend":"","description":"","filename":"d2735af9612f45d79195851cfb6d83441structuring.xml","url":"https://assets-eu.researchsquare.com/files/rs-8596112/v1/2c8cee812c52b66a4dcf8975.xml"},{"id":101205851,"identity":"f1c84991-9ffd-4130-8281-26aadda047e9","added_by":"auto","created_at":"2026-01-27 09:50:25","extension":"html","order_by":36,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":98325,"visible":true,"origin":"","legend":"","description":"","filename":"earlyproof.html","url":"https://assets-eu.researchsquare.com/files/rs-8596112/v1/f0b123ef5927a230d71d3017.html"},{"id":101205652,"identity":"ed7a0317-1f96-412f-8acb-60aa19b56896","added_by":"auto","created_at":"2026-01-27 09:50:02","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":16872983,"visible":true,"origin":"","legend":"\u003cp\u003eSupine (a) and prone (b) imaging positions with a microscopy coil placed in the left mandibular molar region. The example of proton density-weighted (PDW) (c, d) image taken of a volunteer participant in this study using dental MRI are shown below\u003c/p\u003e","description":"","filename":"Fig.1.png","url":"https://assets-eu.researchsquare.com/files/rs-8596112/v1/ac24bbab97b12553610b7e6d.png"},{"id":101100134,"identity":"de75be4e-4025-43b0-98cf-57c213ee92ae","added_by":"auto","created_at":"2026-01-26 01:24:38","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":209367,"visible":true,"origin":"","legend":"\u003cp\u003eResult of volunteer participant’s subjective evaluation of imaging positions\u003c/p\u003e","description":"","filename":"Fig.2.png","url":"https://assets-eu.researchsquare.com/files/rs-8596112/v1/782c4e1dac5c4f5b962f246f.png"},{"id":101205045,"identity":"1011abad-efa9-448a-ab44-f35633318585","added_by":"auto","created_at":"2026-01-27 09:45:47","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":495587,"visible":true,"origin":"","legend":"\u003cp\u003eResults of visual evaluation of T1-weighted (T1W) (a), T2-weighted (T2W) (b), and PDW (c) images by interpretation\u003c/p\u003e","description":"","filename":"Fig.3.png","url":"https://assets-eu.researchsquare.com/files/rs-8596112/v1/d785a1e1c95f3e06822c8a00.png"},{"id":101100114,"identity":"3170b5f2-d6e0-472f-b700-c70ea2699578","added_by":"auto","created_at":"2026-01-26 01:24:37","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":2604011,"visible":true,"origin":"","legend":"\u003cp\u003eVisual assessment results for T1W (a, b), T2W (c, d), and PDW (e, f) considering the order of imaging positions\u003c/p\u003e","description":"","filename":"Fig.41.png","url":"https://assets-eu.researchsquare.com/files/rs-8596112/v1/7acb274b5bf18234d1183a70.png"},{"id":101100124,"identity":"2958a1bf-1da9-4052-9d80-aeae23d98b5c","added_by":"auto","created_at":"2026-01-26 01:24:37","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":2220634,"visible":true,"origin":"","legend":"\u003cp\u003eExamples of volunteer images used in visual evaluation by observers. T1W (a), T2W (b), and PDW (c) images in the supine position with an average visual quality score of approximately 3, and T1W (d), T2W (e), and PDW (f) images in the prone position with an average score of approximately 2 are shown (4-point scale: 1=non-diagnostic to 4=fully diagnostic). These images illustrate the typical quality achieved in each position\u003c/p\u003e","description":"","filename":"Fig.5.png","url":"https://assets-eu.researchsquare.com/files/rs-8596112/v1/d71cecd353b6566afefe6526.png"},{"id":102294804,"identity":"98feb48e-8af4-4e5e-b366-21c7dce1984f","added_by":"auto","created_at":"2026-02-10 09:58:54","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":23816088,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-8596112/v1/bd6a10db-2c2f-460e-b9e6-713900a6d7be.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Comparison of Supine and Prone Positions for Dental MRI with a Microscopy Coil: Image Quality and Patient Burden in Healthy Volunteers","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eIn dental imaging, intraoral radiography, panoramic radiography, and dental cone-beam computed tomography (CBCT) are routinely employed for clinical diagnosis. However, these conventional modalities have inherent limitations in soft tissue visualization due to their reliance on X-ray attenuation, and CT-based techniques involve concerns regarding radiation exposure [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. Dental magnetic resonance imaging (dental MRI) has recently emerged as a promising alternative modality, offering superior soft tissue contrast for visualizing the periodontal structures, the dental pulp and the periodontal ligament, without the use of ionizing radiation [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e, \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]. Nevertheless, the clinical implementation of dental MRI faces technical challenges, particularly in achieving the high spatial resolution (\u0026lt;\u0026thinsp;1 mm) required for detailed evaluation of dental structures [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eSeveral approaches have been investigated to enhance the spatial resolution of dental MRI, which is essential for the detailed evaluation of dental structures. These include the use of high-field-strength systems and the development of dedicated receiver coils with improved signal-to-noise ratio (SNR) [\u003cspan additionalcitationids=\"CR6 CR7 CR8 CR9 CR10 CR11\" citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]. Among these strategies, coil optimization has emerged as a particularly promising approach, as dedicated surface coils and intraoral coils have demonstrated superior SNR and spatial resolution compared to standard head and neck coils [\u003cspan additionalcitationids=\"CR7 CR8 CR9 CR10 CR11\" citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eMicroscopy coils, which have been successfully employed in other medical imaging applications, represent a notable candidate for dental MRI [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e]. The anatomical positioning of teeth and periodontal tissues directly beneath the buccinator muscle places them within the optimal imaging range of microscopy coils, potentially enabling high-resolution visualization of dental structures [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e]. These previous studies, although promising, did not comprehensively evaluate the degree of patient burden associated with imaging positions such as supine and prone positions and did not consider oral radiologist image quality assessments. Therefore, this study aimed to evaluate the burden related to imaging positions (subjective evaluation of participant burden), visibility of the teeth and periodontal tissues (visual image quality assessment by an oral radiologist and an endodontist), and SNR and contrast-to-noise ratio (CNR) (physical image evaluation) by imaging the teeth and periodontal tissues of healthy volunteers using a microscopy coil and a 3.0T MRI system with T1-weighted (T1W), T2-weighted (T2W), and proton density-weighted (PDW) sequences, thereby determining the more appropriate subject positioning for dental MRI using a microscopy coil.\u003c/p\u003e"},{"header":"2. Materials and Methods","content":"\u003cp\u003e \u003cb\u003e2\u0026thinsp;\u0026minus;\u0026thinsp;1. Equipment Used\u003c/b\u003e \u003c/p\u003e \u003cp\u003eA 3.0T MRI system, Ingenia Elition (Release ver5.7; Philips Medical Systems, Best Netherlands) and a 47 mm microscopy coil (Philips Medical Systems, Best Netherlands) were used. Imaging was performed using a MRI system. Statistical testing was performed using EZR (ver1.54; Saitama Medical Center, Jichi Medical University, Saitama, Japan) and Microsoft Excel 2016 (ver. 2504; Microsoft Way, Redmond, WA). This study was approved by our Medical Ethics Committee (approval number: 11238).\u003c/p\u003e\n\u003ch3\u003e2–2. Volunteer Participants and Imaging Conditions\u003c/h3\u003e\n\u003cp\u003eThe volunteer participants were 26 healthy volunteers (1 male, 25 females, aged 20\u0026ndash;25 years, mean age 20.8 years) who underwent dental MR in both the supine and prone positions between September 2024 and January 2025 (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ea-d). The microscopy coil was placed on the skin surface corresponding to the root apex of the left mandibular first molar and fixed with surgical tape. Imaging was performed in the supine position facing upward and in the prone position with the head turned to the right so that the left mandible contacted the floor surface. The order of the positions was alternated between participants, with some imaged from supine to prone and others from prone to supine. The imaging conditions used the same protocol for both the supine and prone positions, considering parameters from previous studies, and acquiring T1W, T2W, and PDW images [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e] (Table\u0026nbsp;1). For all volunteers, the imaging sequence began with PDW, which excels at visualizing anatomical structures, followed by T1W and T2W in that order. The imaging sequences were selected based on the comparative tissue contrast between T1W and T2W, which excel at visualizing inferior alveolar neurovascular bundle (IAN) and dental pulp, respectively, and considering comparisons with previous studies. PDW was chosen for each region due to PDW's superior ability to depict anatomical structures.\u003c/p\u003e\n\u003ch3\u003e2–3. Subjective Evaluation of Imaging Positions\u003c/h3\u003e\n\u003cp\u003eVolunteer participants who completed imaging evaluated the burden of each position (supine and prone) using a 10-point scale ranging from 1 (no discomfort) to 10 (maximum discomfort) [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]. Mean scores and standard deviations were calculated for both positions, and statistical significance was assessed using the Wilcoxon signed-rank test with a significance level of p\u0026thinsp;\u0026lt;\u0026thinsp;0.05.\u003c/p\u003e\n\u003ch3\u003e2–4. Visual Evaluation by Observers\u003c/h3\u003e\n\n\u003ch3\u003e2-4-1. Visual Image Quality Assessment by Observers\u003c/h3\u003e\n\u003cp\u003eVisual evaluation was performed by two observers, an oral radiologist with 13 years of clinical experience (Observer A) and an endodontist with 12 years of clinical experience (Observer B), on T1W, T2W, and PDW images obtained from volunteer participants in the supine and prone positions. Four evaluation items were established for each image series: \"Sharpness,\" \"Artifacts,\" \" Perceived SNR,\" and \"Image quality,\" evaluated on a scale of 1\u0026thinsp;=\u0026thinsp;non-diagnostic, 2\u0026thinsp;=\u0026thinsp;limited but interpretable, 3\u0026thinsp;=\u0026thinsp;diagnostic with some limitations, 4\u0026thinsp;=\u0026thinsp;fully diagnostic. Visual evaluation was performed twice, with the first and second evaluations separated by at least 1 week. The images were presented in random order, and each was evaluated independently. The mean scores and standard deviations for the supine and prone positions were calculated for each evaluation item, and statistical significance was assessed using the Wilcoxon signed-rank test (statistical significance set at p\u0026thinsp;\u0026lt;\u0026thinsp;0.05).\u003c/p\u003e\n\u003ch3\u003e2-4-2. Effect of Image Order on Image Quality\u003c/h3\u003e\n\u003cp\u003eTo evaluate the effect of the imaging sequence order, comparisons were made between groups imaged from supine to prone and groups imaged from prone to supine, mean scores and standard deviations were calculated, and statistical significance was determined. The Wilcoxon signed-rank test was used, with statistical significance set at p\u0026thinsp;\u0026lt;\u0026thinsp;0.05.\u003c/p\u003e\n\u003ch3\u003e2-4-3. Observer Agreement and Proportion of Non-Diagnostic Images\u003c/h3\u003e\n\u003cp\u003eWeighted κ values were calculated to assess intra-observer agreement (between the first and second evaluations of each observer) and inter-observer agreement. κ values were interpreted according to the following criteria: poor (\u0026lt;\u0026thinsp;0.00), slight (0.00-0.20), fair (0.21\u0026ndash;0.40), moderate (0.41\u0026ndash;0.60), substantial (0.61\u0026ndash;0.80), and almost perfect (0.81-1.00) [\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]. Additionally, to evaluate the feasibility of obtaining diagnostic-quality images in each position, the proportion of cases rated as non-diagnostic (score 1 by both observers for all four evaluation criteria: sharpness, artifacts, perceived SNR, and image quality) was compared between supine and prone positions for each sequence (T1W, T2W, PDW). Fisher's exact test was used for statistical comparison, with significance set at p\u0026thinsp;\u0026lt;\u0026thinsp;0.05.\u003c/p\u003e\n\u003ch3\u003e2–5. SNR and CNR Evaluation\u003c/h3\u003e\n\u003cp\u003eBased on the visual evaluation results, volunteer data with an average score of 1 (non-diagnostic) in all four evaluation items were excluded, and the SNR of the dental pulp, the IAN, the bone marrow, and CNR relatives to dentin were calculated (11 cases for T1W, 14 cases for T2W, and 15 cases for PDW). Regions of interest (ROI) of 1 mm\u0026sup2; were set on the dental pulp, IAN, bone marrow, and dentin in the obtained image data to acquire the mean signal values and standard deviations for SNR and CNR calculations [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e].\u003cdiv id=\"Equa\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equa\" name=\"EquationSource\"\u003e\n$$\\:{SNR}_{DP}=\\frac{{Average\\:Mean}_{DP}}{{SD}_{DP}}$$\u003c/div\u003e\u003c/div\u003e\u003cdiv id=\"Equb\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equb\" name=\"EquationSource\"\u003e\n$$\\:{SNR}_{IAN}=\\frac{{Average\\:Mean}_{IAN}}{{SD}_{IAN}}$$\u003c/div\u003e\u003c/div\u003e\u003cdiv id=\"Equc\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equc\" name=\"EquationSource\"\u003e\n$$\\:{SNR}_{BM}=\\frac{{Average\\:Mean}_{BM}}{{SD}_{BM}}$$\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e \u003cp\u003eWhere SNR\u003csub\u003eDP\u003c/sub\u003e, SNR\u003csub\u003eIAN\u003c/sub\u003e, and SNR\u003csub\u003eBM\u003c/sub\u003e are the SNRs of dental pulp, IAN, and bone marrow, respectively. Average Mean\u003csub\u003eDP\u003c/sub\u003e, Mean\u003csub\u003eIAN\u003c/sub\u003e, and Average Mean\u003csub\u003eBM\u003c/sub\u003e are the mean signal values of the dental pulp, IAN, and bone marrow, respectively. where SD\u003csub\u003eDP\u003c/sub\u003e, SD\u003csub\u003eIAN\u003c/sub\u003e, and SD\u003csub\u003eBM\u003c/sub\u003e are the standard deviations of the dental pulp, IAN, and bone marrow, respectively [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e].\u003cdiv id=\"Equd\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equd\" name=\"EquationSource\"\u003e\n$$\\:{CNR}_{DP}=\\:\\frac{{Average\\:Mean}_{DP}-\\:{Average\\:Mean}_{DT}}{{SD}_{DP}}$$\u003c/div\u003e\u003c/div\u003e\u003cdiv id=\"Eque\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Eque\" name=\"EquationSource\"\u003e\n$$\\:{CNR}_{IAN}=\\:\\frac{{Average\\:Mean}_{IAN}-\\:{Average\\:Mean}_{DT}}{{SD}_{IAN}}$$\u003c/div\u003e\u003c/div\u003e\u003cdiv id=\"Equf\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equf\" name=\"EquationSource\"\u003e\n$$\\:{CNR}_{BM}=\\:\\frac{{Average\\:Mean}_{BM}-\\:{Average\\:Mean}_{DT}}{{SD}_{BM}}$$\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e \u003cp\u003eWhere CNR\u003csub\u003eDP\u003c/sub\u003e, CNR\u003csub\u003eIAN\u003c/sub\u003e, and CNR\u003csub\u003eBM\u003c/sub\u003e are the CNRs of dental pulp, IAN, and bone marrow, respectively. The Average Mean\u003csub\u003eDT\u003c/sub\u003e is the mean signal value of the dentin. The statistical significance between the supine and prone positions was determined for each anatomical site and sequence. The Kolmogorov\u0026ndash;Smirnov test was performed to confirm normality, and the F-test was used to confirm equal variance. For data following a normal distribution, paired t-tests were used, with statistical significance set at p\u0026thinsp;\u0026lt;\u0026thinsp;0.05. For data that did not follow a normal distribution, the Wilcoxon signed-rank test was used, with statistical significance set at p\u0026thinsp;\u0026lt;\u0026thinsp;0.05.\u003c/p\u003e"},{"header":"3. Results","content":"\u003cp\u003e \u003cb\u003e3\u0026thinsp;\u0026minus;\u0026thinsp;1. Volunteer Participant-Reported Subjective Evaluation of Imaging Positions\u003c/b\u003e \u003c/p\u003e \u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e shows the results of the participant-reported evaluation scores for burden according to imaging position differences. The mean values and standard deviations of participant-reported evaluation scores for supine and prone positions were 1.7 (SD\u0026thinsp;\u0026plusmn;\u0026thinsp;1.1) and 4.7 (SD\u0026thinsp;\u0026plusmn;\u0026thinsp;2.1), respectively. There was a significant difference between the supine and prone positions (p\u0026thinsp;\u0026lt;\u0026thinsp;0.01).\u003c/p\u003e\n\u003ch3\u003e3 − 2. Visual Evaluation by Observers\u003c/h3\u003e\n\n\u003ch3\u003e3-2-1. Visual Image Quality Assessment by Observers\u003c/h3\u003e\n\u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ea-c shows the results of the visual evaluation. For T1W, the mean scores and standard deviations for supine position in sharpness, artifacts, perceived SNR, and image quality were 2.4 (SD\u0026thinsp;\u0026plusmn;\u0026thinsp;1.0), 2.3 (SD\u0026thinsp;\u0026plusmn;\u0026thinsp;1.1), 2.3 (SD\u0026thinsp;\u0026plusmn;\u0026thinsp;1.1), and 2.4 (SD\u0026thinsp;\u0026plusmn;\u0026thinsp;1.0), respectively, while for prone position they were 1.8 (SD\u0026thinsp;\u0026plusmn;\u0026thinsp;1.0), 1.6 (SD\u0026thinsp;\u0026plusmn;\u0026thinsp;1.0), 1.6 (SD\u0026thinsp;\u0026plusmn;\u0026thinsp;0.9), and 1.8 (SD\u0026thinsp;\u0026plusmn;\u0026thinsp;1.0), respectively (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ea).\u003c/p\u003e \u003cp\u003eFor T2W, the mean scores and standard deviations for supine position in sharpness, artifacts, perceived SNR, and image quality were 2.7 (SD\u0026thinsp;\u0026plusmn;\u0026thinsp;1.0), 2.6 (SD\u0026thinsp;\u0026plusmn;\u0026thinsp;1.1), 2.6 (SD\u0026thinsp;\u0026plusmn;\u0026thinsp;1.1), and 2.8 (SD\u0026thinsp;\u0026plusmn;\u0026thinsp;1.0), respectively, while for prone position they were 1.8 (SD\u0026thinsp;\u0026plusmn;\u0026thinsp;0.9), 1.6 (SD\u0026thinsp;\u0026plusmn;\u0026thinsp;0.9), 1.7 (SD\u0026thinsp;\u0026plusmn;\u0026thinsp;0.9), and 1.7 (SD\u0026thinsp;\u0026plusmn;\u0026thinsp;0.9), respectively (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eb).\u003c/p\u003e \u003cp\u003eFor PDW, the mean scores and standard deviations for supine position in sharpness, artifacts, perceived SNR, and image quality were 2.9 (SD\u0026thinsp;\u0026plusmn;\u0026thinsp;1.1), 2.6 (SD\u0026thinsp;\u0026plusmn;\u0026thinsp;1.1), 2.7 (SD\u0026thinsp;\u0026plusmn;\u0026thinsp;1.1), and 2.9 (SD\u0026thinsp;\u0026plusmn;\u0026thinsp;1.1), respectively, while for prone position they were 2.0 (SD\u0026thinsp;\u0026plusmn;\u0026thinsp;1.1), 1.8 (SD\u0026thinsp;\u0026plusmn;\u0026thinsp;1.0), 1.8 (SD\u0026thinsp;\u0026plusmn;\u0026thinsp;1.0), and 1.9 (SD\u0026thinsp;\u0026plusmn;\u0026thinsp;1.0), respectively (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ec). All evaluation items showed p\u0026thinsp;\u0026lt;\u0026thinsp;0.01, indicating significant differences between the supine and prone positions.\u003c/p\u003e\n\u003ch3\u003e3-2-2. Effect of Imaging Order on Image Quality\u003c/h3\u003e\n\u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ea-f shows the visual evaluation score results considering the order of the imaging positions. For T1W in the group imaged from supine to prone, the mean scores and standard deviations for supine position in sharpness, artifacts, perceived SNR, and image quality were 2.8 (SD\u0026thinsp;\u0026plusmn;\u0026thinsp;0.8), 2.7 (SD\u0026thinsp;\u0026plusmn;\u0026thinsp;0.9), 2.7 (SD\u0026thinsp;\u0026plusmn;\u0026thinsp;0.9), and 2.8 (SD\u0026thinsp;\u0026plusmn;\u0026thinsp;0.8), respectively, while for prone position they were 1.5 (SD\u0026thinsp;\u0026plusmn;\u0026thinsp;0.8), 1.5 (SD\u0026thinsp;\u0026plusmn;\u0026thinsp;0.9), 1.5 (SD\u0026thinsp;\u0026plusmn;\u0026thinsp;0.7), and 1.6 (SD\u0026thinsp;\u0026plusmn;\u0026thinsp;0.8), respectively (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ea). All evaluation items showed p\u0026thinsp;\u0026lt;\u0026thinsp;0.01, indicating significant differences between the supine and prone positions. For T1W in the group imaged from prone to supine, the mean scores and standard deviations for supine position in sharpness, artifacts, perceived SNR, and image quality were 2.0 (SD\u0026thinsp;\u0026plusmn;\u0026thinsp;1.0), 1.9 (SD\u0026thinsp;\u0026plusmn;\u0026thinsp;1.0), 1.9 (SD\u0026thinsp;\u0026plusmn;\u0026thinsp;0.9), and 2.0 (SD\u0026thinsp;\u0026plusmn;\u0026thinsp;1.0), respectively, while for prone position they were 2.0 (SD\u0026thinsp;\u0026plusmn;\u0026thinsp;1.0), 1.8 (SD\u0026thinsp;\u0026plusmn;\u0026thinsp;0.9), 1.8 (SD\u0026thinsp;\u0026plusmn;\u0026thinsp;0.9), and 2.0 (SD\u0026thinsp;\u0026plusmn;\u0026thinsp;1.1), respectively (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eb). No statistically significant differences were observed between the supine and prone positions for any of the evaluation items.\u003c/p\u003e \u003cp\u003eFor T2W in the group imaged from supine to prone, the mean scores and standard deviations for supine position in sharpness, artifacts, perceived SNR, and image quality were 3.0 (SD\u0026thinsp;\u0026plusmn;\u0026thinsp;0.8), 2.9 (SD\u0026thinsp;\u0026plusmn;\u0026thinsp;1.0), 2.9 (SD\u0026thinsp;\u0026plusmn;\u0026thinsp;0.9), and 3.1 (SD\u0026thinsp;\u0026plusmn;\u0026thinsp;0.9), respectively, while for prone position they were 1.6 (SD\u0026thinsp;\u0026plusmn;\u0026thinsp;0.9), 1.5 (SD\u0026thinsp;\u0026plusmn;\u0026thinsp;0.9), 1.5 (SD\u0026thinsp;\u0026plusmn;\u0026thinsp;0.7), and 1.6 (SD\u0026thinsp;\u0026plusmn;\u0026thinsp;0.9), respectively (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ec). All evaluation items showed p\u0026thinsp;\u0026lt;\u0026thinsp;0.01, indicating significant differences between the supine and prone positions. For T2W in the group imaged from prone to supine, the mean scores and standard deviations for supine position in sharpness, artifacts, perceived SNR, and image quality were 2.5 (SD\u0026thinsp;\u0026plusmn;\u0026thinsp;0.9), 2.3 (SD\u0026thinsp;\u0026plusmn;\u0026thinsp;1.0), 2.4 (SD\u0026thinsp;\u0026plusmn;\u0026thinsp;1.0), and 2.5 (SD\u0026thinsp;\u0026plusmn;\u0026thinsp;0.9), respectively, while for prone position they were 1.9 (SD\u0026thinsp;\u0026plusmn;\u0026thinsp;0.7), 1.7 (SD\u0026thinsp;\u0026plusmn;\u0026thinsp;0.7), 1.8 (SD\u0026thinsp;\u0026plusmn;\u0026thinsp;0.8), and 1.9 (SD\u0026thinsp;\u0026plusmn;\u0026thinsp;0.7), respectively (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ed). All evaluation parameters showed p\u0026thinsp;\u0026lt;\u0026thinsp;0.05, indicating statistically significant differences between the supine and prone positions.\u003c/p\u003e \u003cp\u003eFor PDW in the group imaged from supine to prone, the mean scores and standard deviations for supine position in sharpness, artifacts, perceived SNR, and image quality were 3.4 (SD\u0026thinsp;\u0026plusmn;\u0026thinsp;0.8), 3.1 (SD\u0026thinsp;\u0026plusmn;\u0026thinsp;1.0), 3.1 (SD\u0026thinsp;\u0026plusmn;\u0026thinsp;1.0), and 3.4 (SD\u0026thinsp;\u0026plusmn;\u0026thinsp;0.8), respectively, while for prone position they were 1.7 (SD\u0026thinsp;\u0026plusmn;\u0026thinsp;1.0), 1.6 (SD\u0026thinsp;\u0026plusmn;\u0026thinsp;0.9), 1.6 (SD\u0026thinsp;\u0026plusmn;\u0026thinsp;0.9), and 1.6 (SD\u0026thinsp;\u0026plusmn;\u0026thinsp;0.8), respectively (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ee). All evaluation items showed p\u0026thinsp;\u0026lt;\u0026thinsp;0.01, indicating significant differences between the supine and prone positions. For PDW in the group imaged from prone to supine, the mean scores and standard deviations for supine position in sharpness, artifacts, perceived SNR, and image quality were 2.5 (SD\u0026thinsp;\u0026plusmn;\u0026thinsp;0.9), 2.2 (SD\u0026thinsp;\u0026plusmn;\u0026thinsp;1.0), 2.3 (SD\u0026thinsp;\u0026plusmn;\u0026thinsp;0.9), and 2.4 (SD\u0026thinsp;\u0026plusmn;\u0026thinsp;1.0), respectively, while for prone position they were 2.4 (SD\u0026thinsp;\u0026plusmn;\u0026thinsp;1.0), 2.0 (SD\u0026thinsp;\u0026plusmn;\u0026thinsp;0.9), 2.1 (SD\u0026thinsp;\u0026plusmn;\u0026thinsp;0.9), and 2.3 (SD\u0026thinsp;\u0026plusmn;\u0026thinsp;0.9), respectively (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ef). No statistically significant differences were observed between the supine and prone positions for any of the evaluation items.\u003c/p\u003e\n\u003ch3\u003e3-2-3. Observer Agreement\u003c/h3\u003e\n\u003cp\u003e Observer A's agreement between first and second evaluations was moderate to substantial (κ value of 0.44\u0026ndash;0.65), and Observer B's agreement between first and second evaluations was moderate to substantial (κ value of 0.54\u0026ndash;0.75). Agreement between Observer A and B was fair to moderate (κ value of 0.30\u0026ndash;0.48).\u003c/p\u003e\n\u003ch3\u003e3-2-4. Proportion of Non-Diagnostic Images\u003c/h3\u003e\n\u003cp\u003eThe number of cases with a score of 1 assigned by both observers for all evaluation items was significantly higher in the prone position than in the supine position across all sequences: T1W (13/26 vs. 5/26, p\u0026thinsp;=\u0026thinsp;0.04), T2W (12/26 vs. 1/26, p\u0026thinsp;\u0026lt;\u0026thinsp;0.001), and PDW (10/26 vs. 2/26, p\u0026thinsp;=\u0026thinsp;0.019) (Table\u0026nbsp;2). This substantial difference in the proportion of non-diagnostic images indicates that the prone position presented greater challenges for obtaining diagnostic-quality images compared with the supine position.\u003c/p\u003e\n\u003ch3\u003e3–3. SNR and CNR Evaluation\u003c/h3\u003e\n\n\u003ch3\u003e3-3-1. SNR Measurements\u003c/h3\u003e\n\u003cp\u003eFor T1W, the mean scores and standard deviations of SNR for the dental pulp, the IAN, and the bone marrow in supine position were 8.6 (SD\u0026thinsp;\u0026plusmn;\u0026thinsp;3.2), 8.0 (SD\u0026thinsp;\u0026plusmn;\u0026thinsp;2.8), and 25.3 (SD\u0026thinsp;\u0026plusmn;\u0026thinsp;6.6), respectively, while for prone position they were 8.8 (SD\u0026thinsp;\u0026plusmn;\u0026thinsp;2.5), 7.0 (SD\u0026thinsp;\u0026plusmn;\u0026thinsp;2.3), and 23.8 (SD\u0026thinsp;\u0026plusmn;\u0026thinsp;6.1), respectively.\u003c/p\u003e \u003cp\u003eFor T2W, the mean scores and standard deviations of SNR for the dental pulp, the IAN, and the bone marrow in supine position were 9.5 (SD\u0026thinsp;\u0026plusmn;\u0026thinsp;3.4), 12.3 (SD\u0026thinsp;\u0026plusmn;\u0026thinsp;4.7), and 24.1 (SD\u0026thinsp;\u0026plusmn;\u0026thinsp;9.4), respectively, while for prone position they were 10.1 (SD\u0026thinsp;\u0026plusmn;\u0026thinsp;4.4), 11.1 (SD\u0026thinsp;\u0026plusmn;\u0026thinsp;4.2), and 24.9 (SD\u0026thinsp;\u0026plusmn;\u0026thinsp;12.1), respectively.\u003c/p\u003e \u003cp\u003eFor PDW, the mean scores and standard deviations of SNR for the dental pulp, the IAN, and the bone marrow in supine position were 10.4 (SD\u0026thinsp;\u0026plusmn;\u0026thinsp;5.4), 9.7 (SD\u0026thinsp;\u0026plusmn;\u0026thinsp;3.7), and 19.8 (SD\u0026thinsp;\u0026plusmn;\u0026thinsp;5.5), respectively, while for prone position they were 9.4 (SD\u0026thinsp;\u0026plusmn;\u0026thinsp;3.7), 8.3 (SD\u0026thinsp;\u0026plusmn;\u0026thinsp;2.9), and 17.3 (SD\u0026thinsp;\u0026plusmn;\u0026thinsp;5.1), respectively. No statistically significant differences were found between the supine and prone positions for any of the sequences or evaluation items.\u003c/p\u003e\n\u003ch3\u003e3-3-2. CNR Measurements\u003c/h3\u003e\n\u003cp\u003eFor T1W, the mean scores and standard deviations of CNR for the dental pulp, the IAN, and the bone marrow in supine position were 6.9 (SD\u0026thinsp;\u0026plusmn;\u0026thinsp;2.7), 6.8 (SD\u0026thinsp;\u0026plusmn;\u0026thinsp;2.7), and 22.7 (SD\u0026thinsp;\u0026plusmn;\u0026thinsp;5.9), respectively, while for prone position they were 7.1 (SD\u0026thinsp;\u0026plusmn;\u0026thinsp;2.2), 5.6 (SD\u0026thinsp;\u0026plusmn;\u0026thinsp;2.0), and 22.5 (SD\u0026thinsp;\u0026plusmn;\u0026thinsp;5.8), respectively.\u003c/p\u003e \u003cp\u003eFor T2W, the mean scores and standard deviations of CNR for the dental pulp, the IAN, and the bone marrow in supine position were 8.8 (SD\u0026thinsp;\u0026plusmn;\u0026thinsp;3.4), 11.2 (SD\u0026thinsp;\u0026plusmn;\u0026thinsp;4.4), and 23.2 (SD\u0026thinsp;\u0026plusmn;\u0026thinsp;9.2), respectively, while for prone position they were 9.3 (SD\u0026thinsp;\u0026plusmn;\u0026thinsp;4.2), 9.4 (SD\u0026thinsp;\u0026plusmn;\u0026thinsp;3.9), and 23.7 (SD\u0026thinsp;\u0026plusmn;\u0026thinsp;11.7), respectively.\u003c/p\u003e \u003cp\u003eFor PDW, the mean scores and standard deviations of CNR for the dental pulp, the IAN, and the bone marrow in supine position were 9.4 (SD\u0026thinsp;\u0026plusmn;\u0026thinsp;5.0), 8.4 (SD\u0026thinsp;\u0026plusmn;\u0026thinsp;3.3), and 18.8 (SD\u0026thinsp;\u0026plusmn;\u0026thinsp;5.2), respectively, while for prone position they were 8.6 (SD\u0026thinsp;\u0026plusmn;\u0026thinsp;3.5), 6.8 (SD\u0026thinsp;\u0026plusmn;\u0026thinsp;2.5), and 16.3 (SD\u0026thinsp;\u0026plusmn;\u0026thinsp;4.8), respectively. No statistically significant differences were found between the supine and prone positions for any of the sequences or evaluation items.\u003c/p\u003e"},{"header":"4. Discussion","content":"\u003cp\u003eIn this study, using a Microscopy Coil and a 3.0T MRI system, we acquired T1W, T2W, and PDW images of the teeth and the periodontal tissues of healthy volunteers. We evaluated the participant-reported subjective burden ratings in the supine and prone positions, along with visual image quality assessments by an oral radiologist and an endodontist, including SNR and CNR. Prone imaging of the mandible using flex coils have been previously reported, demonstrating improved facial motion suppression and spatial resolution through better coil adherence in the prone position [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e]. However, those studies did not comprehensively assess case numbers, patient burden, or overall image quality. This study obtained data on participant-reported subjective burden levels during dental MRI in the supine and prone positions, presenting foundational data for the clinical application.\u003c/p\u003e \u003cp\u003eRegarding patient burden, it has been reported that factors such as claustrophobia, patient medical history, and examination equipment influence the experience [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e, \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e]. In volunteer participant-reported subjective evaluation of imaging position burden, the supine position showed significantly less subjective burden compared to the prone position (p\u0026thinsp;\u0026lt;\u0026thinsp;0.01). This suggests that the supine position is prioritized for imaging in dental MRI. While the prone position is recommended for breast and lung imaging to reduce respiratory motion effects for imaging sites not directly affected by respiration, high tolerance of the supine position has been reported [\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e, \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e]. Flex coils are made of soft materials, unlike the hard materials used in microscopy coils, which may cause varying levels of discomfort when placed on the facial region. The supine position, by contrast, generally allows for easier breathing and better position maintenance.\u003c/p\u003e \u003cp\u003eIn visual evaluations by an oral radiologist and an endodontist, supine images scored significantly higher than prone images across all sequences (T1W, T2W, PDW) and evaluation items (sharpness, artifacts, perceived SNR, image quality) (p\u0026thinsp;\u0026lt;\u0026thinsp;0.01). This aligns with the burden evaluation findings, suggesting that motion artifacts due to difficulty in maintaining position contribute to reduced image quality. PDW images scored higher than other sequences, likely due to PDW\u0026rsquo;s higher SNR compared with other sequences, resulting in superior visual assessments [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e]. When imaging was performed from supine to prone, the supine position was significantly superior to the prone position across all sequences and evaluation items. Conversely, when imaging was performed from prone to supine, no significant differences were observed between the two positions for T1W and PDW. This suggests that with longer imaging times, positional maintenance becomes challenging even in the supine position, diminishing the quality differences between supine and prone images due to motion artifacts. These findings indicate that dental MR imaging would benefit from being performed early in the examination. For example, when both overall jawbone assessment (using head and neck coils) and localized dental imaging are required, performing dental MRI first may yield higher-quality images. When imaging was performed first in the supine position and then in the prone position, all quality metrics demonstrated significant superiority of the supine position (p\u0026thinsp;\u0026lt;\u0026thinsp;0.01). However, when the order was reversed (first prone and then supine), no significant differences were observed for T1W and PDW sequences (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eb, f). This pattern suggests that patient fatigue and difficulty maintaining position increase with examination duration, regardless of the specific position adopted. The later-acquired images showed degraded quality in both positions, indicating that the timing of acquisition is as important as the choice of position itself.\u003c/p\u003e \u003cp\u003ePhysical evaluations of SNR and CNR revealed no significant differences between the supine and prone positions for any sequence in images of sufficient diagnostic quality. However, the proportion of non-diagnostic images (all evaluation items scored 1 by both observers) was significantly higher in the prone position across all sequences: T1W (13/26 vs. 5/26, p\u0026thinsp;=\u0026thinsp;0.04), T2W (12/26 vs. 1/26, p\u0026thinsp;\u0026lt;\u0026thinsp;0.001), and PDW (10/26 vs. 2/26, p\u0026thinsp;=\u0026thinsp;0.02). This substantial difference represents a critical practical disadvantage of the prone position, as approximately half of prone acquisitions failed to produce diagnostic-quality images compared with less than 20% in the supine position. The absence of significant SNR/CNR differences among the remaining diagnostic-quality images suggests that intrinsic signal intensity changes due to imaging position are minimal when motion artifacts are controlled. The fundamental difference between positions lies in the feasibility of maintaining sufficient positional stability to acquire diagnostic images. Therefore, the image quality differences observed in visual assessments are primarily attributable to motion artifacts and difficulty maintaining position rather than inherent differences in coil-tissue coupling or signal characteristics [\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e, \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e]. This suggests that intrinsic signal intensity changes due to imaging position are minimal, and that the image quality differences observed in visual assessments are primarily attributable to motion artifacts.\u003c/p\u003e \u003cp\u003eIn the supine position, the tongue moves toward the pharynx under gravity, increasing the distance from the dentition and reducing motion effects. Conversely, in the prone position, the tongue is closer to the dentition, potentially increasing motion-related artifacts. Therefore, position selection should prioritize positional maintenance, stability, and patient comfort over physical signal intensity. T1W had more non-diagnostic cases, possibly because the echo spacing\u0026mdash;set to match other sequences\u0026mdash;minimized motion artifact effects from this parameter. T1W generally yields lower visual evaluation scores due to reduced pulp signal compared with T2W and PDW. Collectively, these findings suggest that the supine position is preferable for dental MR imaging.\u003c/p\u003e \u003cp\u003eThe relatively low interobserver agreement rate of 0.30\u0026ndash;0.48 can be attributed to two main factors. First, endodontists assigned substantially lower scores (score 1) compared with oral radiologists, which likely reflects their different levels of familiarity with dental MRI. While oral radiologists routinely interpret MRI studies, endodontists primarily rely on conventional intraoral radiographs and dental CBCT for clinical decision-making, which limits their exposure to characteristics of MRI images [\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e]. Improving inter-observer agreement will require a multifaceted approach: assessments from a larger pool of evaluators with comparable experience levels. A standardized interpretation protocol must be developed before dental MRI can be reliably implemented in clinical practice.\u003c/p\u003e \u003cp\u003eThis study has several limitations that warrant consideration. The volunteer cohort consisted exclusively of individuals in their 20s, which limits the generalizability of the findings of our burden assessments. Older patients and those with facial disorders often experience greater difficulty maintaining stable positions during prolonged examinations, and their inclusion would likely reveal more pronounced tolerance issues and potentially higher rates of motion artifacts. Additionally, the non-randomized sequence order may have introduced systematic differences in motion artifact patterns between early and late acquisitions, as evidenced by our finding that image quality degraded regardless of position when imaging was performed later in the examination. Finally, our SNR and CNR measurements were derived from images containing mild motion artifacts (visual scores of 2 or 3), which may not accurately reflect the theoretical physical image quality achievable under ideal conditions (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ea-f). While eliminating motion artifacts in volunteer studies remains challenging, future technical developments should prioritize reducing acquisition times to minimize their impact.\u003c/p\u003e"},{"header":"5. Conclusion","content":"\u003cp\u003eThis study evaluated imaging positions for dental MRI using a microscopy coil and a 3.0T MRI system by assessing participant burden, image quality, and SNR/CNR in healthy volunteers. The supine position demonstrated significant advantages over the prone position in subjective burden and visual image quality, with a lower rate of non-diagnostic images. Image quality was optimal when dental MRI was performed early in the examination sequence. These findings demonstrate that the supine position is the more appropriate imaging position for dental MRI using a microscopy coil.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e \u003ch2\u003eEthical Approval\u003c/h2\u003e \u003cp\u003e All procedures involving human participants in this study were performed in accordance with the ethical standards of the responsible committee on human experimentation (institutional and national levels) and the Declaration of Helsinki of 1975, as revised in 2024.\u003c/p\u003e \u003c/p\u003e \u003cp\u003e \u003cstrong\u003eConsent to Participate\u003c/strong\u003e \u003cp\u003e Informed consent was obtained from all individual participants included in the study.\u003c/p\u003e \u003c/p\u003e\u003ch2\u003eFunding\u003c/h2\u003e \u003cp\u003eand Competing Interests\u003c/p\u003e \u003cp\u003eThe authors did not receive support from any organization for the submitted work. The authors have no relevant financial or non-financial interests to disclose.\u003c/p\u003e\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eT. Z. conceived and designed the study, performed experiments, analyzed data, created figures and tables, and wrote the original draft.S. K. conceived and designed the study, evaluated images, and wrote the original draft.H. N. evaluated image.Y. A. provided device administrator and edited the manuscript.S. S. revised the figures and edited the manuscript.\u003c/p\u003e\u003ch2\u003eData Availability\u003c/h2\u003e\u003cp\u003eThe data supporting the findings of this study are not openly available for sensitivity reasons but are available from the corresponding author upon reasonable request. Data were stored in controlled-access data at the Central Imaging Center, Osaka Dental University Hospital.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eStratis A, Zhang G, Jacobs R, Bogaerts R, Bosmans H. The growing concern of radiation dose in paediatric dental and maxillofacial CBCT: an easy guide for daily practice. Eur Radiol. 2019;29:7009\u0026ndash;18. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1007/s00330-019-06287-5\u003c/span\u003e\u003cspan address=\"10.1007/s00330-019-06287-5\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eAl-Haj Husain A, Zollinger M, Stadlinger B, \u0026Ouml;zcan M, Winklhofer S, Al-Haj Husain N, et al. Magnetic resonance imaging in dental implant surgery: a systematic review. 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Oral Surgery, Oral Medicine, Oral Pathology and Oral Radiology. 2025;140:113\u0026ndash;24. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/j.oooo.2025.02.011\u003c/span\u003e\u003cspan address=\"10.1016/j.oooo.2025.02.011\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"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":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Magnetic Resonance Imaging, Dental Pulp, Diagnostic Imaging, Signal-To-Noise Ratio","lastPublishedDoi":"10.21203/rs.3.rs-8596112/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-8596112/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003ch2\u003eObjectives\u003c/h2\u003e \u003cp\u003eThis study aimed to evaluate the clinical feasibility of dental magnetic resonance imaging (MRI) using a microscopy coil by comparing imaging positions in healthy volunteers.\u003c/p\u003e\u003ch2\u003eMethods\u003c/h2\u003e \u003cp\u003eTwenty-six healthy volunteers underwent dental MRI in supine and prone positions using a 47 mm microscopy coil on a 3.0T system. T1-weighted (T1W), T2-weighted (T2W), and proton density-weighted (PDW) sequences were acquired. Participant-reported burden was assessed using a 10-point scale. Image quality was evaluated using a 4-point scale for sharpness, artifact, perceived signal-to-noise ratio (SNR), and overall quality. SNR and contrast-to-noise ratio (CNR) were calculated from 1 mm\u003csup\u003e2\u003c/sup\u003e regions of interest in dental pulp, inferior alveolar neurovascular bundle, and bone marrow. Statistical analyses included the Wilcoxon signed-rank test, Fisher's exact test, and paired t-test.\u003c/p\u003e\u003ch2\u003eResults\u003c/h2\u003e \u003cp\u003eParticipant-reported burden was lower in the supine position (1.7\u0026thinsp;\u0026plusmn;\u0026thinsp;1.1) than in the prone (4.7\u0026thinsp;\u0026plusmn;\u0026thinsp;2.1). Visual assessments demonstrated superior image quality in supine across all sequences. The proportion of non-diagnostic images was higher in the prone position: T1W (50% vs. 19%), T2W (46% vs. 4%), and PDW (38% vs. 8%). SNR and CNR showed no differences between positions. Image quality degraded with prolonged examination time regardless of position.\u003c/p\u003e\u003ch2\u003eConclusions\u003c/h2\u003e \u003cp\u003eThe supine position demonstrated lower subjective burden, better visual image quality, and a lower rate of non-diagnostic images compared with the prone position. Image quality was optimal when MRI was performed early in the examination sequence. Therefore, the supine position is more appropriate for dental MRI using a microscopy coil.\u003c/p\u003e","manuscriptTitle":"Comparison of Supine and Prone Positions for Dental MRI with a Microscopy Coil: Image Quality and Patient Burden in Healthy Volunteers","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-01-26 01:24:15","doi":"10.21203/rs.3.rs-8596112/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"df75c8cd-1951-424f-952b-e06e4dfa0c89","owner":[],"postedDate":"January 26th, 2026","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2026-04-27T12:10:15+00:00","versionOfRecord":[],"versionCreatedAt":"2026-01-26 01:24:15","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-8596112","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-8596112","identity":"rs-8596112","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}