The impact of MRI slice thickness on the detection of spinal syndesmophytes in axial spondyloarthritis

The impact of MRI slice thickness on the detection of spinal syndesmophytes in axial spondyloarthritis | 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 The impact of MRI slice thickness on the detection of spinal syndesmophytes in axial spondyloarthritis Kalliopi Klavdianou, Daniel Benjamin Abrar, Alexander Dieter Mewes, and 3 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6629954/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 14 Nov, 2025 Read the published version in Arthritis Research & Therapy → Version 1 posted 7 You are reading this latest preprint version Abstract Background Conventional radiographs (CR) are the gold standard for detecting syndesmophytes in radiographic axial Spondyloarthritis (r-axSpA), while the ability of magnetic resonance imaging (MRI) to detect such bony structures is questionable due to its slicing technique. We aimed to assess the ability and performance for detection of syndesmophytes on MRI using different slice thicknesses and compare them with CR in r-axSpA. Methods MRI (T1-weighted (T1W) sequences) with slice thicknesses of 1-6mm of the lower thoracic and lumbar spine were prospectively performed in patients with available CR. Each vertebral corner (VC) (anterior and posterior) from thoracic (Th11) to lumbar (L5) was assessed for presence/absence of syndesmophytes and/or fat lesions (FL, MRI only) by two experienced readers in independent MRI and CR sessions and agreement was then reached in consensus. Results A total of 1.204 VCs were assessed from 43 r-axSpA patients. Syndesmophytes were recorded in 19.3% VCs on CR and in 38.3%, 37.5%, 34.8%, 33.7%, 31.4%, 28.7% VCs on MRI slice thicknesses of 1-6mm, respectively (all p ≤ 0.001 vs. CR). Although more syndesmophytes were recorded on MRI than CR, MRI also missed 21%-31.3% syndesmophytes detected in CR. Agreement with CR was found in 72.6%, 73.8%, 75.9%, 76%, 77.3% and 78.5% on MRI slice thicknesses of 1-6mm, respectively. FL were detected in 38.2%-39.2% in slice thicknesses 1-6mm. Occurrence of FL was associated with better agreement between MRI and CR findings. Conclusion The thinner the MRI slices, the more syndesmophytes were detected compared to CR, but the best agreement with CR was found in the thicker slices. The presence of fat lesions on MRI was associated with better agreement with CR for syndesmophyte detection. Syndesmophytes MRI slice thickness conventional radiographs axial spondyloarthritis (axSpA) Figures Figure 1 Figure 2 Introduction Axial spondyloarthritis (axSpA) is a chronic inflammatory rheumatic disease affecting the axial skeleton and comprises of two stages, radiographic (r-) and non-radiographic (nr-axSpA) 1 . AxSpA is characterized by inflammatory, osteodestructive and osteoproliferative changes in the sacroiliac joints (SIJ) and spine. 2 Syndesmophytes and ankylosis of the vertebral column are relevant structural changes indicating new bone formation in r-axSpA. 3 Syndesmophytes are thin bony outgrowths from the spinal ligaments attaching to adjacent vertebral bodies. Such bone proliferation starts at the vertebral rim and grows in the direction of the anulus fibrosus, parallel to the vertebral axis 3 . The modified Stoke Ankylosing Spondylitis Spine Score (mSASSS) 4 , the most frequently used radiologic scoring method for r-axSpA 5 , is heavily weighted by syndesmophytes and is used in clinical studies for assessment of radiographic progression in relation to treatment. Inflammatory activity as depicted by magnetic resonance imaging (MRI) is predictive to structural changes seen subsequently on conventional radiographs 6 . However, the exact sequence of this process is incompletely understood. The main hypothesis is that resolving inflammation associates with fat deposition. 7 – 9 Such fat lesions (FL), can be depicted by the T1-weighted (T1W) MRI sequences in vertebral bodies but also in the SIJs when present, and represent the strongest predictor for radiographic progression in axSpA. However, not all syndesmophytes develop at sites with preexisting fat or inflammation. 7 – 10 The ‘gold standard’ for assessment of syndesmophytes in r-axSpA are conventional radiographs (CR). While the lower part of the thoracic spine has been reported to be the most sensitive to change for assessment of syndesmophyte formation over time 11 , the evaluation of the spine by CR is mainly reported by inclusion of the cervical and lumbar spine only, due to the overlying soft tissues in the thoracic spine. Computed tomography (CT) has superior sensitivity and specificity compared to CR, however, it is partly associated with higher radiation exposure, while both methods fail to detect bone marrow edema (BME) as a sign of inflammatory activity. In contrast, MRI is the best way to assess BME but the possibility for MRI to depict chronic changes such as syndesmophytes has not been yet determined. This study aimed to assess the ability and performance of detection of syndesmophytes using different slice thicknesses on MRI and compare them with syndesmophytes depicted on CR. Methods Lower spine MRI and CR were performed in patients with an established diagnosis of r-axSpA upon clinical indication for imaging due to low back pain, independent of treatment. The examinations were performed in a 1.5 Tesla MRI (Siemens Magnetom Prisma) system under the same protocol and included the TSE T1 and STIR sagittal sequences. All sequences were acquired with all slice thicknesses 1–6 mm at the same imaging session. CR were available from the same patients in a sagittal position based on the protocol used in daily routine practice. Each VC (anterior superior and inferior and posterior superior and inferior) from the low thoracic (Th11) to the lumbar (L5) vertebral body was assessed for the presence/absence of syndesmophytes and presence/absence of FL in all MRI slice thicknesses and in CR (syndesmophytes only) by two experienced readers (one radiologist and one rheumatologist), independently. MRIs and CRs were assessed in different reading campaigns, this means without the knowledge of the results of other imaging technique, respectively. Disagreements in findings for syndesmophytes and FL were finally solved in consensus and the findings with agreement were taken into account for the final analysis. Clinical information The collected clinical information was age, sex, Bath Ankylosing Spondylitis Functional Index (BASFI) 12 , disease duration and treatment at the timepoint of imaging. Statistical analysis Descriptive measures (mean, median) are shown with SD, minimum and maximum or interquartile range (IQR). Frequencies and percentages are provided for categorical data (n). Comparison of medians of sums of affected lesions between different slice thicknesses and for each slice thickness versus CR was performed using Wilcoxon signed rank test. Missing values, such as not evaluable VCs due to previous surgeries or missing clinical information, were not imputed. Results are always presented based on the available data for each parameter. All statistical tests were two-sided and a p < 0.05 was considered statistically significant. Results Patient’s characteristics A total of 43 r-axSpA patients (81.4% males, mean age of 50 ± 15.4 years, median disease duration of 7.3 (IQR:15.5) years) were included. Table 1 shows the relevant clinical characteristics of the patients. Overall, a total of 1.204 VCs was assessed from all patients in both CR and MRI. The VCs were assessed in all MRI slice thicknesses (1-6mm). Table 1 Clinical and demographic characteristics of the participants Patient characteristics All (n = 43) males n,(%) 35(81.4) Age at MRI, years, mean ± SD median (IQR) 50 ± 15.4 51.8(13.1) Disease duration at MRI, years median (IQR) 7.3 (15.5) BASFI, median (IQR) 6 (2.9) Current Treatment n (%) bDMARD TNFi IL17i NSAIDs 35(81.4) 30 (69.8) 5 (11.6) 8 (18.6) bDMARD, biologic Disease-modifying antirheumatic drug; IL17i, interleukin 17 inhibitor; MRI, Magnetic resonance imaging; NSAIDs, Non-steroidal anti-inflammatory drugs; TNFi, Tumour necrosis factor (TNF)-alpha inhibitor Agreement in imaging evaluation between readers Any discrepancies between readers were seen in 977 (9.5%) of the scored VCs. In detail, discrepancies were seen in 874 (9.7%) of the assessed VCs in the MRI and in 103 (8.6%) of assessed VCs in CR. Most discrepant cases on MRI syndesmophytes were found in thinner slices (n = 180 discrepant findings in slice thickness of 1mm). Overall comparison of syndermophytes on MRI and CR Syndesmophytes in both the thoracic and lumbar spine were detected in 38.3%, 37.5%, 34.8%, 33.7%, 31.4%, 28.7% VCs for MRI slice thicknesses of 1mm, 2mm, 3mm, 4mm, 5mm and 6mm respectively (Fig. 1 ) and in 19.3% of the VCs in CR, p < 0.05 for all MRI slice thicknesses comparisons, with exception the comparison between MRI slices of 1-2mm (p = 0.251) and 3-4mm (p = 0.062). The anterior superior corners of Th12 and L1 were the overall most frequently affected site in both MRI and CR (Suppl. Table 1). Upon consensus, CR could detect 233 syndesmophytes, (Suppl. Table 1 ) . MRI at any slice thickness could not detect 49/233 (21%) – 73/233 (31.3%) (all slice thicknesses) of the CR syndesmophytes, while 186 (53.8%) – 279 (60.5%) of the syndesmophytes seen on MRI were not seen on CR ( Table 2 ) . The anterior inferior corner of Th11, the posterior superior corner of L1 and the anterior inferior corner of L4 were the sites with the most syndesmophytes missed by MRI, as compared to CR (data not shown). Overall, best agreement (either detected or missed in both MRI and CR) between imaging modalities was found in the thicker slices ( Fig. 1 , Table 2 ) . However, when assessing with CR as a gold standard, more CR detected syndesmophytes were missed on MRI slice thickness of 5mm and 6mm as compared to 1mm slice thickness (missing syndesmophytes in MRI 64 vs 51, p = 0. 035 and 73 vs 51, p = 0.001, respectively). The same result was found for 4mm, 5mm and 6mm slice thickness compared to 2mm (missing syndesmophytes 58 vs 49, p = 0. 039 and 64 vs 49, p = 0.007, 73 vs 49, p = 0.001, respectively). Additionally, with slice thickness of 3mm less CR detected syndesmophytes compared to 5mm (52 vs 64, p = 0.011) and with a 3mm and 4mm slice thickness less than with 6mm (52 vs 73, p = 0.005 and 58 vs 73, p = 0.005, respectively) were missed ( Table 2 ) . In addition, more discrepant cases between MRI and CR were found in MRI-detected syndesmophytes without concomitant FL (197–147, 59.7% − 56.8% of all MRI detected syndesmophytes) as compared with those with concomitant FL (133 − 112, 40.3% − 43.2% of all MRI detected syndesmophytes) for MRI slice thickness 1-6mm, respectively. Table 2 Agreement of CR and MRI for syndesmophyte detection per MRI slice thickness CR Agreement CR/MRI False positive MR based on CR as gold standard MRI yes no 1mm yes 182 279 72,6% 60.5% no 51 692 2mm yes 184 267 73,8% 59.2% no 49 704 3mm yes 181 238 75,9% 56.8% no 52 733 4mm yes 175 231 76,0% 56.9% no 58 740 5mm yes 169 209 77,3% 55.3% no 64 762 6mm yes 160 186 78,5% 53.8% no 73 785 Exam and scoring duration of spine MRI for each slice thickness Taking into account that thinner MRI slices could detect more syndesmophytes than the thicker ones and CR, we assessed if performing a thinner slice MRI is also more time consuming. The time needed for this MRI protocol including every slice thickness was about 45minutes (mins) (8–10 mins and about 4mins for each one of the thinner and thicker slices, respectively) The time for evaluation of the MR images for the presence of syndesmophytes and fat was 4’12’’, 4’11’’,3’33’’, 2’27’’, 2’27’’ for 1mm, 2mm, 3mm, 4mm, 5mm, and 6mm slices, respectively, suggesting that a six times thinner slice does not increase the time to score fat and syndesmophytes by six times. The influence of fat lesions in the detection of syndesmophytes on MRI in comparison to CR Fat lesions were detected in 38.2%, 38.9%, 39.2%, 39.2%, 38.9%, 38.9% of vertebrae (lumbar or thoracic) with MRI slice thicknesses of 1–6 mm, respectively. MRI slice thickness had no relation to the frequency of detecting of fat lesions both in the thoracic and lumbar vertebrae. Fat lesions at the same VC with syndesmophytes were detected at 43.8%, 45.7%,46.3%, 45.1%, 46.6% and 50.6% of the VCs affected with syndesmophytes for slice thicknesses of 1-6mm respectively. The percentages of the VCs affected with syndesmophytes in MRI, with concurrent fat lesions presence, also having a syndesmophyte at the same vertebral corner in CR were 39.6%, 41.7%, 43.3%, 43.7%, 44.9% and 44.6% for slice thicknesses of 1-6mm respectively. When trying to evaluate if presence of fat in MRI at the same VC with a CR detected syndesmophyte could facilitate the detection of this syndesmophyte in MRI, we found that the concurrent presence of fat and MRI syndesmophytes in the same vertebral corner and same MRI slice thickness with CR detected syndesmophytes was found in 78.4%, 73.5%, 73.1%, 70.7%, 68.8% and 69.9% in slice thicknesses of 1-6mm, respectively. Hence, about 66%-80% could be depicted in the presence of fat, suggesting that concurrent presence of fat lesions at the same corner could possibly facilitate the identification of a syndesmophyte at the same corner. Typical examples of syndesmophytes detected both on MRI and CR at absence or presence of fat are shown in Fig. 2 . Discussion In this study, which aimed to analyze for the first time the sensitivity and specificity of spinal MR images for detection syndesmophytes using different thickness of slices, we report that MRI at any slice thickness detected more syndesmophytes than those detected in CR. Overall, the thinner the slice thickness was, the more syndesmophytes were detected on MRI. However, in comparison to CR as the ‘gold standard’ for detecting syndesmophytes, ‘false-positive’ results with MRI in our study seemed to increase parallel to decrease of slice thickness. MRI cannot easily differentiate tissues with low proton density such as cortical bone and paravertebral ligaments since they have low or no signal intensity in almost all MRI sequences. 13 On the other hand one could think that CR has lower sensitivity than MRI to detect such structural changes in their ‘earlier’ development phases and it’s rather the syndesmophytes detected in MRI that represent the ‘true picture’ of new bone formation. Performing a spine CT could provide answers regarding this hypothesis. Although not included as a first-line imaging method in any set of recommendations due to the high degree of radiation and higher costs, CT is a more precise method than CR at detecting structural progress of the spine. Actually, the limitations of CR regarding detection of radiographic progression within a short time of follow-up, led to the development of low-dose CT as a technique for detection of progression of bone formation. Additionally, fat lesions in MRI have been positively corelated with CT detected syndesmophytes development. 14 In our cohort the anterior superior corner of L1 and T12 were the most frequently affected sites with syndesmophytes in MRI. These data are in line with CR 11 and CT 15 data that showed that the thoracolumbar area is the most frequently affected area in patients with r-axSpA and also the area that is most sensitive to depict radiographic progression over time. 15 Fat lesions in the bone marrow of patients with axSpA could represent tissue repair after inflammation, leading to development of new syndesmophytes. 16 Contrary to its role in syndesmophytes detection, MRI slice thickness had no influence on detecting fat lesions. Our data suggest that there is no optimal thickness for fat lesions detection. However, the presence of fat lesions was associated with a more accurate detection of syndesmophytes in comparison to CR. This was not surprising, since the presence of the high signal intensity due to the fat lesion which is frequently extending into the newly formed syndesmophyte makes this bone structure much easier to depict. Our findings suggest that although detecting more syndesmophytes than CR, MRI still fails to detect up to one third of the syndesmophytes detected on the CR as a gold-standard. Thinner MRI slices could detect numerically more syndesmophytes that were found to be present in MRI slice thicknesses of 3-4mm, as suggested by international recommendations, seem to miss one fifth to one fourth of CR-detected syndesmophytes. 17 In a real clinical setting, time is important for the evaluation of imaging examinations. Performing an MRI of thinner slices did not increase the time of evaluation of structural changes dramatically. A limitation of the study is the absence of CT examinations for comparison to the used modalities. The higher sensitivity and specificity of CT vs. CR for detection of syndesmophytes in patients with axSpA has been shown in previous studies. 15 It is therefore unknown, whether higher concordance or discordance with the MRI findings would have resulted if CT examinations of the same patients would have been performed. Nevertheless, since still CR is considered to be the gold standard examination for assessment of syndesmophytes in patients with axSpA, we believe that the data presented here are of value for the understanding of such spinal structures in daily practice and when both CR but also MRI examinations are evaluated. In conclusion, our data suggest that MRI slice thickness plays a role in detecting syndesmophytes, with thinner slice thicknesses detecting more syndesmophytes compared to the thicker ones, although overall MRI may still be considered as depicting rather unclear findings due to the missing correlation to CR as the gold standard. Slice thickness does not seem to affect the detection of fat lesions, while caution should be paid in syndesmophytes that are depicted in the absence of fat lesions due to the uncertainty of these syndesmophytes in comparison to the more accurately detected ones when fat is present. Prospective studies in combination with CT to confirm these results are warranted to make any recommendation for daily practice. Abbreviations BASFI Bath Ankylosing Spondylitis Functional Index BME Bone marrow edema CR:Conventional radiographs CT Computed tomography FL Fat lesions IQR Interquartile range L:lumbar mm Millimeter MRI Magnetic resonance imaging mSASSS modified Stoke Ankylosing Spondylitis Spine Score nr-axSpA Non-radiographic axial Spondyloarthritis r-axSpA Radiographic axial Spondyloarthritis SD Standard deviation SIJ Sacroiliac joints STIR Short tau inversion recovery Th Thoracic TSE Turbo spin echo T1W T1-weighted VC Vertebral corner Declarations Ethics approval and consent to participate Written informed consent was acquired from all participants before the initiation of the study. The study was approved by the local ethical committee (Ethical Committee, Medical Faculty, University of Düsseldorf, Germany, study number 5087R). Consent for publication All patient data was anonymous. Patient’s consent for usage of data was received from all patients. Competing interests The authors declare no competing interests. Funding No funding was received. Acknowledgements Not applicable Authors' information 1 Rheumazentrum Ruhrgebiet Herne, Ruhr-University Bochum, Claudiusstr. 45, 44649, Herne, Germany 2 Department of Rheumatology, "Asklepieion" General Hospital, 16673, Voula, Athens, Greece 3 University Dusseldorf, Medical Faculty, Department of Diagnostic and Interventional Radiology, D-40225 Dusseldorf, Germany. 4 Radiology Munich, Burgstraße 7, 80331, Munich, Germany References Rudwaleit M, van der Heijde D, Landewé R, et al. The development of Assessment of SpondyloArthritis international Society classification criteria for axial spondyloarthritis (part II): validation and final selection. Ann Rheum Dis. 2009;68(6):777–83. 10.1136/ard.2009.108233 . Sieper J, Poddubnyy D. Axial spondyloarthritis. Lancet (London England). 2017;390(10089):73–84. 10.1016/S0140-6736(16)31591-4 . Baraliakos X, Listing J, Rudwaleit M, et al. 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MRI inflammation at the vertebral unit only marginally predicts new syndesmophyte formation: a multilevel analysis in patients with ankylosing spondylitis. Ann Rheum Dis. 2012;71(3):369–73. 10.1136/annrheumdis-2011-200208 . Baraliakos X, Heldmann F, Callhoff J, et al. Which spinal lesions are associated with new bone formation in patients with ankylosing spondylitis treated with anti-TNF agents? A long-term observational study using MRI and conventional radiography. Ann Rheum Dis. 2014;73(10):1819–25. 10.1136/annrheumdis-2013-203425 . Machado PM, Baraliakos X, van der Heijde D, Braun J, Landewé R. MRI vertebral corner inflammation followed by fat deposition is the strongest contributor to the development of new bone at the same vertebral corner: a multilevel longitudinal analysis in patients with ankylosing spondylitis. Ann Rheum Dis. 2016;75(8):1486–93. 10.1136/annrheumdis-2015-208011 . Stal R, Ramiro S, van der Heijde D, et al. 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Supplementary Files SupplementaryTable1.docx Cite Share Download PDF Status: Published Journal Publication published 14 Nov, 2025 Read the published version in Arthritis Research & Therapy → Version 1 posted Editorial decision: Revision requested 17 Jul, 2025 Reviews received at journal 14 Jul, 2025 Reviewers agreed at journal 11 Jul, 2025 Reviewers invited by journal 10 Jul, 2025 Editor assigned by journal 13 May, 2025 Submission checks completed at journal 13 May, 2025 First submitted to journal 09 May, 2025 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. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. 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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-6629954","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":484742837,"identity":"087e3a9d-ad74-4170-8dbd-05a1ce1c9a0f","order_by":0,"name":"Kalliopi Klavdianou","email":"","orcid":"","institution":"Rheumazentrum Ruhrgebiet Herne, Ruhr-University Bochum","correspondingAuthor":false,"prefix":"","firstName":"Kalliopi","middleName":"","lastName":"Klavdianou","suffix":""},{"id":484742838,"identity":"69efcc11-27ce-442c-b31a-dbcf3802bef3","order_by":1,"name":"Daniel Benjamin Abrar","email":"","orcid":"","institution":"University Dusseldorf, Medical Faculty","correspondingAuthor":false,"prefix":"","firstName":"Daniel","middleName":"Benjamin","lastName":"Abrar","suffix":""},{"id":484742839,"identity":"88090467-0395-43d5-81ec-4e79284157d0","order_by":2,"name":"Alexander Dieter Mewes","email":"","orcid":"","institution":"University Dusseldorf, Medical Faculty","correspondingAuthor":false,"prefix":"","firstName":"Alexander","middleName":"Dieter","lastName":"Mewes","suffix":""},{"id":484742840,"identity":"5d5f9340-49a0-4129-86a6-4d194f4e9986","order_by":3,"name":"Styliani Tsiami","email":"","orcid":"","institution":"Rheumazentrum Ruhrgebiet Herne, Ruhr-University Bochum","correspondingAuthor":false,"prefix":"","firstName":"Styliani","middleName":"","lastName":"Tsiami","suffix":""},{"id":484742841,"identity":"15ade1fa-7c73-427d-bcf1-10672a68f4d9","order_by":4,"name":"Philipp Sewerin","email":"","orcid":"","institution":"Rheumazentrum Ruhrgebiet Herne, Ruhr-University Bochum","correspondingAuthor":false,"prefix":"","firstName":"Philipp","middleName":"","lastName":"Sewerin","suffix":""},{"id":484742842,"identity":"af5be442-979e-4f1a-9fc5-05d9855d6fe6","order_by":5,"name":"Xenofon Baraliakos","email":"data:image/png;base64,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","orcid":"","institution":"Rheumazentrum Ruhrgebiet Herne, Ruhr-University Bochum","correspondingAuthor":true,"prefix":"","firstName":"Xenofon","middleName":"","lastName":"Baraliakos","suffix":""}],"badges":[],"createdAt":"2025-05-09 15:23:26","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-6629954/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-6629954/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1186/s13075-025-03665-x","type":"published","date":"2025-11-14T15:57:12+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":86672719,"identity":"599869bd-17f9-4333-8a67-8fd2329df9f6","added_by":"auto","created_at":"2025-07-14 11:41:19","extension":"jpg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":312684,"visible":true,"origin":"","legend":"\u003cp\u003eDistribution of VCs affected with syndesmophytes in different slice thicknesses of MRI. CR bar charts show the number of MRI detected syndesmophytes also seen in CR.\u003c/p\u003e\n\u003cp\u003eMRI, Magnetic Resonance Imaging; CR, Conventional Radiograph; VC: Vertebral Corner\u003c/p\u003e","description":"","filename":"Figure1.jpg","url":"https://assets-eu.researchsquare.com/files/rs-6629954/v1/fadfcbddaedb4c31a788a82a.jpg"},{"id":86672720,"identity":"89873d77-51f7-40f8-bd36-ef864b30e34c","added_by":"auto","created_at":"2025-07-14 11:41:19","extension":"jpg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":425658,"visible":true,"origin":"","legend":"\u003cp\u003eA) Syndesmophyte at the anterior superior corner of L4 detected on both each MRI slice thickness and CR (thin arrow). No concurrent presence of fat at the same corner. B) Syndesmophyte at the anterior superior corner of T12 detected on both each MRI slice thickness and CR (thick arrow). Concurrent presence of fat at the same corner in MRI (asterisk).\u003c/p\u003e","description":"","filename":"Figure2.jpg","url":"https://assets-eu.researchsquare.com/files/rs-6629954/v1/c3050759f5fe13f489e145fa.jpg"},{"id":96104971,"identity":"3faeb4eb-cc06-4251-9c4a-1df0154866f6","added_by":"auto","created_at":"2025-11-17 16:05:26","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1404753,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6629954/v1/a7f1d555-0854-4df1-954b-4524ca06084b.pdf"},{"id":86672730,"identity":"c691f9f8-b9a1-4ce8-831a-ab95205965c0","added_by":"auto","created_at":"2025-07-14 11:41:19","extension":"docx","order_by":0,"title":"","display":"","copyAsset":false,"role":"supplement","size":21429,"visible":true,"origin":"","legend":"","description":"","filename":"SupplementaryTable1.docx","url":"https://assets-eu.researchsquare.com/files/rs-6629954/v1/0d3e7db4e33c1c283481bc09.docx"}],"financialInterests":"No competing interests reported.","formattedTitle":"The impact of MRI slice thickness on the detection of spinal syndesmophytes in axial spondyloarthritis","fulltext":[{"header":"Introduction","content":"\u003cp\u003eAxial spondyloarthritis (axSpA) is a chronic inflammatory rheumatic disease affecting the axial skeleton and comprises of two stages, radiographic (r-) and non-radiographic (nr-axSpA)\u003csup\u003e\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u003c/sup\u003e. AxSpA is characterized by inflammatory, osteodestructive and osteoproliferative changes in the sacroiliac joints (SIJ) and spine.\u003csup\u003e\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e\u003c/sup\u003e Syndesmophytes and ankylosis of the vertebral column are relevant structural changes indicating new bone formation in r-axSpA.\u003csup\u003e\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e\u003c/sup\u003e Syndesmophytes are thin bony outgrowths from the spinal ligaments attaching to adjacent vertebral bodies. Such bone proliferation starts at the vertebral rim and grows in the direction of the anulus fibrosus, parallel to the vertebral axis\u003csup\u003e\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e\u003cp\u003eThe modified Stoke Ankylosing Spondylitis Spine Score (mSASSS)\u003csup\u003e\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e\u003c/sup\u003e, the most frequently used radiologic scoring method for r-axSpA\u003csup\u003e\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e\u003c/sup\u003e, is heavily weighted by syndesmophytes and is used in clinical studies for assessment of radiographic progression in relation to treatment.\u003c/p\u003e\u003cp\u003eInflammatory activity as depicted by magnetic resonance imaging (MRI) is predictive to structural changes seen subsequently on conventional radiographs\u003csup\u003e\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e\u003c/sup\u003e. However, the exact sequence of this process is incompletely understood. The main hypothesis is that resolving inflammation associates with fat deposition.\u003csup\u003e\u003cspan additionalcitationids=\"CR8\" citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e\u003c/sup\u003eSuch fat lesions (FL), can be depicted by the T1-weighted (T1W) MRI sequences in vertebral bodies but also in the SIJs when present, and represent the strongest predictor for radiographic progression in axSpA. However, not all syndesmophytes develop at sites with preexisting fat or inflammation.\u003csup\u003e\u003cspan additionalcitationids=\"CR8 CR9\" citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e\u003c/sup\u003e\u003c/p\u003e\u003cp\u003eThe \u0026lsquo;gold standard\u0026rsquo; for assessment of syndesmophytes in r-axSpA are conventional radiographs (CR). While the lower part of the thoracic spine has been reported to be the most sensitive to change for assessment of syndesmophyte formation over time\u003csup\u003e\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e\u003c/sup\u003e, the evaluation of the spine by CR is mainly reported by inclusion of the cervical and lumbar spine only, due to the overlying soft tissues in the thoracic spine. Computed tomography (CT) has superior sensitivity and specificity compared to CR, however, it is partly associated with higher radiation exposure, while both methods fail to detect bone marrow edema (BME) as a sign of inflammatory activity. In contrast, MRI is the best way to assess BME but the possibility for MRI to depict chronic changes such as syndesmophytes has not been yet determined.\u003c/p\u003e\u003cp\u003eThis study aimed to assess the ability and performance of detection of syndesmophytes using different slice thicknesses on MRI and compare them with syndesmophytes depicted on CR.\u003c/p\u003e"},{"header":"Methods","content":"\u003cp\u003eLower spine MRI and CR were performed in patients with an established diagnosis of r-axSpA upon clinical indication for imaging due to low back pain, independent of treatment. The examinations were performed in a 1.5 Tesla MRI (Siemens Magnetom Prisma) system under the same protocol and included the TSE T1 and STIR sagittal sequences. All sequences were acquired with all slice thicknesses 1\u0026ndash;6 mm at the same imaging session. CR were available from the same patients in a sagittal position based on the protocol used in daily routine practice. Each VC (anterior superior and inferior and posterior superior and inferior) from the low thoracic (Th11) to the lumbar (L5) vertebral body was assessed for the presence/absence of syndesmophytes and presence/absence of FL in all MRI slice thicknesses and in CR (syndesmophytes only) by two experienced readers (one radiologist and one rheumatologist), independently. MRIs and CRs were assessed in different reading campaigns, this means without the knowledge of the results of other imaging technique, respectively. Disagreements in findings for syndesmophytes and FL were finally solved in consensus and the findings with agreement were taken into account for the final analysis.\u003c/p\u003e\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\u003ch2\u003eClinical information\u003c/h2\u003e\u003cp\u003eThe collected clinical information was age, sex, Bath Ankylosing Spondylitis Functional Index (BASFI)\u003csup\u003e\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e\u003c/sup\u003e, disease duration and treatment at the timepoint of imaging.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec4\" class=\"Section2\"\u003e\u003ch2\u003eStatistical analysis\u003c/h2\u003e\u003cp\u003eDescriptive measures (mean, median) are shown with SD, minimum and maximum or interquartile range (IQR). Frequencies and percentages are provided for categorical data (n). Comparison of medians of sums of affected lesions between different slice thicknesses and for each slice thickness versus CR was performed using Wilcoxon signed rank test. Missing values, such as not evaluable VCs due to previous surgeries or missing clinical information, were not imputed. Results are always presented based on the available data for each parameter. All statistical tests were two-sided and a p\u0026thinsp;\u0026lt;\u0026thinsp;0.05 was considered statistically significant.\u003c/p\u003e\u003c/div\u003e"},{"header":"Results","content":"\u003cdiv id=\"Sec6\" class=\"Section2\"\u003e\u003ch2\u003ePatient\u0026rsquo;s characteristics\u003c/h2\u003e\u003cp\u003eA total of 43 r-axSpA patients (81.4% males, mean age of 50\u0026thinsp;\u0026plusmn;\u0026thinsp;15.4 years, median disease duration of 7.3 (IQR:15.5) years) were included. Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e shows the relevant clinical characteristics of the patients. Overall, a total of 1.204 VCs was assessed from all patients in both CR and MRI. The VCs were assessed in all MRI slice thicknesses (1-6mm).\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eClinical and demographic characteristics of the participants\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"2\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePatient characteristics\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eAll (n\u0026thinsp;=\u0026thinsp;43)\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003emales n,(%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e35(81.4)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eAge at MRI, years, mean\u0026thinsp;\u0026plusmn;\u0026thinsp;SD\u003c/p\u003e\u003cp\u003emedian (IQR)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e50\u0026thinsp;\u0026plusmn;\u0026thinsp;15.4\u003c/p\u003e\u003cp\u003e51.8(13.1)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eDisease duration at MRI, years median (IQR)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e7.3 (15.5)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eBASFI, median (IQR)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e6 (2.9)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eCurrent Treatment n (%)\u003c/p\u003e\u003cp\u003ebDMARD\u003c/p\u003e\u003cp\u003eTNFi\u003c/p\u003e\u003cp\u003eIL17i\u003c/p\u003e\u003cp\u003eNSAIDs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cbr\u003e35(81.4)\u003c/p\u003e\u003cp\u003e30 (69.8)\u003c/p\u003e\u003cp\u003e5 (11.6)\u003c/p\u003e\u003cp\u003e8 (18.6)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c2\" namest=\"c1\"\u003e\u003cp\u003ebDMARD, biologic Disease-modifying antirheumatic drug; IL17i,\u0026nbsp;interleukin 17 inhibitor; MRI, Magnetic resonance imaging; NSAIDs, Non-steroidal anti-inflammatory drugs; TNFi, Tumour necrosis factor\u0026nbsp;(TNF)-alpha inhibitor\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003c/div\u003e\n\u003ch3\u003eAgreement in imaging evaluation between readers\u003c/h3\u003e\n\u003cp\u003eAny discrepancies between readers were seen in 977 (9.5%) of the scored VCs. In detail, discrepancies were seen in 874 (9.7%) of the assessed VCs in the MRI and in 103 (8.6%) of assessed VCs in CR. Most discrepant cases on MRI syndesmophytes were found in thinner slices (n\u0026thinsp;=\u0026thinsp;180 discrepant findings in slice thickness of 1mm).\u003c/p\u003e\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e\u003ch2\u003eOverall comparison of syndermophytes on MRI and CR\u003c/h2\u003e\u003cp\u003eSyndesmophytes in both the thoracic and lumbar spine were detected in 38.3%, 37.5%, 34.8%, 33.7%, 31.4%, 28.7% VCs for MRI slice thicknesses of 1mm, 2mm, 3mm, 4mm, 5mm and 6mm respectively (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e) and in 19.3% of the VCs in CR, p\u0026thinsp;\u0026lt;\u0026thinsp;0.05 for all MRI slice thicknesses comparisons, with exception the comparison between MRI slices of 1-2mm (p\u0026thinsp;=\u0026thinsp;0.251) and 3-4mm (p\u0026thinsp;=\u0026thinsp;0.062). The anterior superior corners of Th12 and L1 were the overall most frequently affected site in both MRI and CR (Suppl. Table\u0026nbsp;1). Upon consensus, CR could detect 233 syndesmophytes, \u003cb\u003e(Suppl.\u003c/b\u003eTable\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e\u003cb\u003e)\u003c/b\u003e. MRI at any slice thickness could not detect 49/233 (21%) \u0026ndash; 73/233 (31.3%) (all slice thicknesses) of the CR syndesmophytes, while 186 (53.8%) \u0026ndash; 279 (60.5%) of the syndesmophytes seen on MRI were not seen on CR \u003cb\u003e(\u003c/b\u003eTable\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e\u003cb\u003e)\u003c/b\u003e. The anterior inferior corner of Th11, the posterior superior corner of L1 and the anterior inferior corner of L4 were the sites with the most syndesmophytes missed by MRI, as compared to CR (data not shown). Overall, best agreement (either detected or missed in both MRI and CR) between imaging modalities was found in the thicker slices \u003cb\u003e(\u003c/b\u003eFig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e, Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e\u003cb\u003e)\u003c/b\u003e. However, when assessing with CR as a gold standard, more CR detected syndesmophytes were missed on MRI slice thickness of 5mm and 6mm as compared to 1mm slice thickness (missing syndesmophytes in MRI 64 vs 51, p\u0026thinsp;=\u0026thinsp;0. 035 and 73 vs 51, p\u0026thinsp;=\u0026thinsp;0.001, respectively). The same result was found for 4mm, 5mm and 6mm slice thickness compared to 2mm (missing syndesmophytes 58 vs 49, p\u0026thinsp;=\u0026thinsp;0. 039 and 64 vs 49, p\u0026thinsp;=\u0026thinsp;0.007, 73 vs 49, p\u0026thinsp;=\u0026thinsp;0.001, respectively). Additionally, with slice thickness of 3mm less CR detected syndesmophytes compared to 5mm (52 vs 64, p\u0026thinsp;=\u0026thinsp;0.011) and with a 3mm and 4mm slice thickness less than with 6mm (52 vs 73, p\u0026thinsp;=\u0026thinsp;0.005 and 58 vs 73, p\u0026thinsp;=\u0026thinsp;0.005, respectively) were missed \u003cb\u003e(\u003c/b\u003eTable\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e\u003cb\u003e)\u003c/b\u003e. In addition, more discrepant cases between MRI and CR were found in MRI-detected syndesmophytes without concomitant FL (197\u0026ndash;147, 59.7% \u0026minus;\u0026thinsp;56.8% of all MRI detected syndesmophytes) as compared with those with concomitant FL (133\u0026thinsp;\u0026minus;\u0026thinsp;112, 40.3% \u0026minus;\u0026thinsp;43.2% of all MRI detected syndesmophytes) for MRI slice thickness 1-6mm, respectively.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eAgreement of CR and MRI for syndesmophyte detection per MRI slice thickness\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"6\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/th\u003e\u003cth align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e\u003cp\u003eCR\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e\u003cp\u003eAgreement CR/MRI\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c6\"\u003e\u003cp\u003eFalse positive MR based on CR as gold standard\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c2\" namest=\"c1\"\u003e\u003cp\u003e\u003cb\u003eMRI\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eyes\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eno\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e\u003cp\u003e\u003cb\u003e1mm\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eyes\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e182\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e279\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\" morerows=\"1\" rowspan=\"2\"\u003e\u003cp\u003e72,6%\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\" morerows=\"1\" rowspan=\"2\"\u003e\u003cp\u003e60.5%\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eno\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e51\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e692\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e\u003cp\u003e\u003cb\u003e2mm\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eyes\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e184\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e267\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\" morerows=\"1\" rowspan=\"2\"\u003e\u003cp\u003e73,8%\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\" morerows=\"1\" rowspan=\"2\"\u003e\u003cp\u003e59.2%\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eno\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e49\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e704\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e\u003cp\u003e\u003cb\u003e3mm\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eyes\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e181\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e238\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\" morerows=\"1\" rowspan=\"2\"\u003e\u003cp\u003e75,9%\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\" morerows=\"1\" rowspan=\"2\"\u003e\u003cp\u003e56.8%\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eno\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e52\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e733\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e\u003cp\u003e\u003cb\u003e4mm\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eyes\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e175\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e231\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\" morerows=\"1\" rowspan=\"2\"\u003e\u003cp\u003e76,0%\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\" morerows=\"1\" rowspan=\"2\"\u003e\u003cp\u003e56.9%\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eno\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e58\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e740\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e\u003cp\u003e\u003cb\u003e5mm\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eyes\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e169\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e209\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\" morerows=\"1\" rowspan=\"2\"\u003e\u003cp\u003e77,3%\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\" morerows=\"1\" rowspan=\"2\"\u003e\u003cp\u003e55.3%\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eno\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e64\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e762\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e\u003cp\u003e\u003cb\u003e6mm\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eyes\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e160\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e186\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\" morerows=\"1\" rowspan=\"2\"\u003e\u003cp\u003e78,5%\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\" morerows=\"1\" rowspan=\"2\"\u003e\u003cp\u003e53.8%\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eno\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e73\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e785\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003c/div\u003e\n\u003ch3\u003eExam and scoring duration of spine MRI for each slice thickness\u003c/h3\u003e\n\u003cp\u003eTaking into account that thinner MRI slices could detect more syndesmophytes than the thicker ones and CR, we assessed if performing a thinner slice MRI is also more time consuming. The time needed for this MRI protocol including every slice thickness was about 45minutes (mins) (8\u0026ndash;10 mins and about 4mins for each one of the thinner and thicker slices, respectively)\u003c/p\u003e\u003cp\u003eThe time for evaluation of the MR images for the presence of syndesmophytes and fat was 4\u0026rsquo;12\u0026rsquo;\u0026rsquo;, 4\u0026rsquo;11\u0026rsquo;\u0026rsquo;,3\u0026rsquo;33\u0026rsquo;\u0026rsquo;, 2\u0026rsquo;27\u0026rsquo;\u0026rsquo;, 2\u0026rsquo;27\u0026rsquo;\u0026rsquo; for 1mm, 2mm, 3mm, 4mm, 5mm, and 6mm slices, respectively, suggesting that a six times thinner slice does not increase the time to score fat and syndesmophytes by six times.\u003c/p\u003e\n\u003ch3\u003eThe influence of fat lesions\u003c/h3\u003e\n\u003cdiv id=\"Sec11\" class=\"Section2\"\u003e\u003ch2\u003ein the detection of syndesmophytes on MRI in comparison to CR\u003c/h2\u003e\u003cp\u003eFat lesions were detected in 38.2%, 38.9%, 39.2%, 39.2%, 38.9%, 38.9% of vertebrae (lumbar or thoracic) with MRI slice thicknesses of 1\u0026ndash;6 mm, respectively. MRI slice thickness had no relation to the frequency of detecting of fat lesions both in the thoracic and lumbar vertebrae. Fat lesions at the same VC with syndesmophytes were detected at 43.8%, 45.7%,46.3%, 45.1%, 46.6% and 50.6% of the VCs affected with syndesmophytes for slice thicknesses of 1-6mm respectively. The percentages of the VCs affected with syndesmophytes in MRI, with concurrent fat lesions presence, also having a syndesmophyte at the same vertebral corner in CR were 39.6%, 41.7%, 43.3%, 43.7%, 44.9% and 44.6% for slice thicknesses of 1-6mm respectively. When trying to evaluate if presence of fat in MRI at the same VC with a CR detected syndesmophyte could facilitate the detection of this syndesmophyte in MRI, we found that the concurrent presence of fat and MRI syndesmophytes in the same vertebral corner and same MRI slice thickness with CR detected syndesmophytes was found in 78.4%, 73.5%, 73.1%, 70.7%, 68.8% and 69.9% in slice thicknesses of 1-6mm, respectively. Hence, about 66%-80% could be depicted in the presence of fat, suggesting that concurrent presence of fat lesions at the same corner could possibly facilitate the identification of a syndesmophyte at the same corner. Typical examples of syndesmophytes detected both on MRI and CR at absence or presence of fat are shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e"},{"header":"Discussion","content":"\u003cp\u003eIn this study, which aimed to analyze for the first time the sensitivity and specificity of spinal MR images for detection syndesmophytes using different thickness of slices, we report that MRI at any slice thickness detected more syndesmophytes than those detected in CR. Overall, the thinner the slice thickness was, the more syndesmophytes were detected on MRI. However, in comparison to CR as the \u0026lsquo;gold standard\u0026rsquo; for detecting syndesmophytes, \u0026lsquo;false-positive\u0026rsquo; results with MRI in our study seemed to increase parallel to decrease of slice thickness.\u003c/p\u003e\u003cp\u003eMRI cannot easily differentiate tissues with low proton density such as cortical bone and paravertebral ligaments since they have low or no signal intensity in almost all MRI sequences.\u003csup\u003e\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e\u003c/sup\u003e On the other hand one could think that CR has lower sensitivity than MRI to detect such structural changes in their \u0026lsquo;earlier\u0026rsquo; development phases and it\u0026rsquo;s rather the syndesmophytes detected in MRI that represent the \u0026lsquo;true picture\u0026rsquo; of new bone formation. Performing a spine CT could provide answers regarding this hypothesis. Although not included as a first-line imaging method in any set of recommendations due to the high degree of radiation and higher costs, CT is a more precise method than CR at detecting structural progress of the spine. Actually, the limitations of CR regarding detection of radiographic progression within a short time of follow-up, led to the development of low-dose CT as a technique for detection of progression of bone formation. Additionally, fat lesions in MRI have been positively corelated with CT detected syndesmophytes development.\u003csup\u003e\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e\u003c/sup\u003e\u003c/p\u003e\u003cp\u003eIn our cohort the anterior superior corner of L1 and T12 were the most frequently affected sites with syndesmophytes in MRI. These data are in line with CR\u003csup\u003e\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e\u003c/sup\u003e and CT\u003csup\u003e\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e\u003c/sup\u003e data that showed that the thoracolumbar area is the most frequently affected area in patients with r-axSpA and also the area that is most sensitive to depict radiographic progression over time.\u003csup\u003e\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e\u003c/sup\u003e\u003c/p\u003e\u003cp\u003eFat lesions in the bone marrow of patients with axSpA could represent tissue repair after inflammation, leading to development of new syndesmophytes.\u003csup\u003e\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e\u003c/sup\u003e Contrary to its role in syndesmophytes detection, MRI slice thickness had no influence on detecting fat lesions. Our data suggest that there is no optimal thickness for fat lesions detection. However, the presence of fat lesions was associated with a more accurate detection of syndesmophytes in comparison to CR. This was not surprising, since the presence of the high signal intensity due to the fat lesion which is frequently extending into the newly formed syndesmophyte makes this bone structure much easier to depict.\u003c/p\u003e\u003cp\u003eOur findings suggest that although detecting more syndesmophytes than CR, MRI still fails to detect up to one third of the syndesmophytes detected on the CR as a gold-standard. Thinner MRI slices could detect numerically more syndesmophytes that were found to be present in MRI slice thicknesses of 3-4mm, as suggested by international recommendations, seem to miss one fifth to one fourth of CR-detected syndesmophytes.\u003csup\u003e\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e\u003c/sup\u003e\u003c/p\u003e\u003cp\u003eIn a real clinical setting, time is important for the evaluation of imaging examinations. Performing an MRI of thinner slices did not increase the time of evaluation of structural changes dramatically.\u003c/p\u003e\u003cp\u003eA limitation of the study is the absence of CT examinations for comparison to the used modalities. The higher sensitivity and specificity of CT vs. CR for detection of syndesmophytes in patients with axSpA has been shown in previous studies.\u003csup\u003e\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e\u003c/sup\u003e It is therefore unknown, whether higher concordance or discordance with the MRI findings would have resulted if CT examinations of the same patients would have been performed. Nevertheless, since still CR is considered to be the gold standard examination for assessment of syndesmophytes in patients with axSpA, we believe that the data presented here are of value for the understanding of such spinal structures in daily practice and when both CR but also MRI examinations are evaluated.\u003c/p\u003e\u003cp\u003eIn conclusion, our data suggest that MRI slice thickness plays a role in detecting syndesmophytes, with thinner slice thicknesses detecting more syndesmophytes compared to the thicker ones, although overall MRI may still be considered as depicting rather unclear findings due to the missing correlation to CR as the gold standard. Slice thickness does not seem to affect the detection of fat lesions, while caution should be paid in syndesmophytes that are depicted in the absence of fat lesions due to the uncertainty of these syndesmophytes in comparison to the more accurately detected ones when fat is present. Prospective studies in combination with CT to confirm these results are warranted to make any recommendation for daily practice.\u003c/p\u003e"},{"header":"Abbreviations","content":"\u003cdiv class=\"DefinitionList\"\u003e\u003cdiv class=\"DefinitionListEntry\"\u003e\u003cdiv class=\"Term\"\u003eBASFI\u003c/div\u003e\u003cdiv class=\"Description\"\u003e\u003cp\u003eBath Ankylosing Spondylitis Functional Index\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\u003cdiv class=\"DefinitionListEntry\"\u003e\u003cdiv class=\"Term\"\u003eBME\u003c/div\u003e\u003cdiv class=\"Description\"\u003e\u003cp\u003eBone marrow edema CR:Conventional radiographs\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\u003cdiv class=\"DefinitionListEntry\"\u003e\u003cdiv class=\"Term\"\u003eCT\u003c/div\u003e\u003cdiv class=\"Description\"\u003e\u003cp\u003eComputed tomography\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\u003cdiv class=\"DefinitionListEntry\"\u003e\u003cdiv class=\"Term\"\u003eFL\u003c/div\u003e\u003cdiv class=\"Description\"\u003e\u003cp\u003eFat lesions\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\u003cdiv class=\"DefinitionListEntry\"\u003e\u003cdiv class=\"Term\"\u003eIQR\u003c/div\u003e\u003cdiv class=\"Description\"\u003e\u003cp\u003eInterquartile range L:lumbar\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\u003cdiv class=\"DefinitionListEntry\"\u003e\u003cdiv class=\"Term\"\u003emm\u003c/div\u003e\u003cdiv class=\"Description\"\u003e\u003cp\u003eMillimeter\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\u003cdiv class=\"DefinitionListEntry\"\u003e\u003cdiv class=\"Term\"\u003eMRI\u003c/div\u003e\u003cdiv class=\"Description\"\u003e\u003cp\u003eMagnetic resonance imaging\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\u003cdiv class=\"DefinitionListEntry\"\u003e\u003cdiv class=\"Term\"\u003emSASSS\u003c/div\u003e\u003cdiv class=\"Description\"\u003e\u003cp\u003emodified Stoke Ankylosing Spondylitis Spine Score\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\u003cdiv class=\"DefinitionListEntry\"\u003e\u003cdiv class=\"Term\"\u003enr-axSpA\u003c/div\u003e\u003cdiv class=\"Description\"\u003e\u003cp\u003eNon-radiographic axial Spondyloarthritis\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\u003cdiv class=\"DefinitionListEntry\"\u003e\u003cdiv class=\"Term\"\u003er-axSpA\u003c/div\u003e\u003cdiv class=\"Description\"\u003e\u003cp\u003eRadiographic axial Spondyloarthritis\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\u003cdiv class=\"DefinitionListEntry\"\u003e\u003cdiv class=\"Term\"\u003eSD\u003c/div\u003e\u003cdiv class=\"Description\"\u003e\u003cp\u003eStandard deviation\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\u003cdiv class=\"DefinitionListEntry\"\u003e\u003cdiv class=\"Term\"\u003eSIJ\u003c/div\u003e\u003cdiv class=\"Description\"\u003e\u003cp\u003eSacroiliac joints\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\u003cdiv class=\"DefinitionListEntry\"\u003e\u003cdiv class=\"Term\"\u003eSTIR\u003c/div\u003e\u003cdiv class=\"Description\"\u003e\u003cp\u003eShort tau inversion recovery\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\u003cdiv class=\"DefinitionListEntry\"\u003e\u003cdiv class=\"Term\"\u003eTh\u003c/div\u003e\u003cdiv class=\"Description\"\u003e\u003cp\u003eThoracic\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\u003cdiv class=\"DefinitionListEntry\"\u003e\u003cdiv class=\"Term\"\u003eTSE\u003c/div\u003e\u003cdiv class=\"Description\"\u003e\u003cp\u003eTurbo spin echo\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\u003cdiv class=\"DefinitionListEntry\"\u003e\u003cdiv class=\"Term\"\u003eT1W\u003c/div\u003e\u003cdiv class=\"Description\"\u003e\u003cp\u003eT1-weighted\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\u003cdiv class=\"DefinitionListEntry\"\u003e\u003cdiv class=\"Term\"\u003eVC\u003c/div\u003e\u003cdiv class=\"Description\"\u003e\u003cp\u003eVertebral corner\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\u003c/div\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eEthics approval and consent to participate\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eWritten informed consent was acquired from all participants before the initiation of the study. The study was approved by the local ethical committee (Ethical Committee, Medical Faculty, University of D\u0026uuml;sseldorf, Germany, study number 5087R).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent for publication\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAll patient data was anonymous. Patient\u0026rsquo;s consent for usage of data was received from all patients.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interests\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare no competing interests.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNo funding was received.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgements\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthors\u0026apos; information\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e1 Rheumazentrum Ruhrgebiet Herne, Ruhr-University Bochum, Claudiusstr. 45, 44649, Herne, Germany\u003c/p\u003e\n\u003cp\u003e2 Department of Rheumatology, \u0026quot;Asklepieion\u0026quot; General Hospital, 16673, Voula, Athens, Greece\u003c/p\u003e\n\u003cp\u003e3 University Dusseldorf, Medical Faculty, Department of Diagnostic and Interventional Radiology, D-40225 Dusseldorf, Germany.\u003c/p\u003e\n\u003cp\u003e4 Radiology Munich, Burgstra\u0026szlig;e 7, 80331, Munich, Germany\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eRudwaleit M, van der Heijde D, Landew\u0026eacute; R, et al. 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Ann Rheum Dis. 2012;71(8):1278\u0026ndash;88. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1136/ard.2011.150680\u003c/span\u003e\u003cspan address=\"10.1136/ard.2011.150680\" 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":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":"arthritis-research-and-therapy","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"arrt","sideBox":"Learn more about [Arthritis Research \u0026 Therapy](http://arthritis-research.biomedcentral.com/)","snPcode":"13075","submissionUrl":"https://submission.nature.com/new-submission/13075/3","title":"Arthritis Research \u0026 Therapy","twitterHandle":"@ArthritisRes","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"BMC/SO AJ","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"Syndesmophytes, MRI slice thickness, conventional radiographs, axial spondyloarthritis (axSpA)","lastPublishedDoi":"10.21203/rs.3.rs-6629954/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-6629954/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003ch2\u003eBackground\u003c/h2\u003e\u003cp\u003eConventional radiographs (CR) are the gold standard for detecting syndesmophytes in radiographic axial Spondyloarthritis (r-axSpA), while the ability of magnetic resonance imaging (MRI) to detect such bony structures is questionable due to its slicing technique. We aimed to assess the ability and performance for detection of syndesmophytes on MRI using different slice thicknesses and compare them with CR in r-axSpA.\u003c/p\u003e\u003ch2\u003eMethods\u003c/h2\u003e\u003cp\u003eMRI (T1-weighted (T1W) sequences) with slice thicknesses of 1-6mm of the lower thoracic and lumbar spine were prospectively performed in patients with available CR. Each vertebral corner (VC) (anterior and posterior) from thoracic (Th11) to lumbar (L5) was assessed for presence/absence of syndesmophytes and/or fat lesions (FL, MRI only) by two experienced readers in independent MRI and CR sessions and agreement was then reached in consensus.\u003c/p\u003e\u003ch2\u003eResults\u003c/h2\u003e\u003cp\u003eA total of 1.204 VCs were assessed from 43 r-axSpA patients. Syndesmophytes were recorded in 19.3% VCs on CR and in 38.3%, 37.5%, 34.8%, 33.7%, 31.4%, 28.7% VCs on MRI slice thicknesses of 1-6mm, respectively (all p\u0026thinsp;\u0026le;\u0026thinsp;0.001 vs. CR). Although more syndesmophytes were recorded on MRI than CR, MRI also missed 21%-31.3% syndesmophytes detected in CR. Agreement with CR was found in 72.6%, 73.8%, 75.9%, 76%, 77.3% and 78.5% on MRI slice thicknesses of 1-6mm, respectively. FL were detected in 38.2%-39.2% in slice thicknesses 1-6mm. Occurrence of FL was associated with better agreement between MRI and CR findings.\u003c/p\u003e\u003ch2\u003eConclusion\u003c/h2\u003e\u003cp\u003eThe thinner the MRI slices, the more syndesmophytes were detected compared to CR, but the best agreement with CR was found in the thicker slices. The presence of fat lesions on MRI was associated with better agreement with CR for syndesmophyte detection.\u003c/p\u003e","manuscriptTitle":"The impact of MRI slice thickness on the detection of spinal syndesmophytes in axial spondyloarthritis","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-07-14 11:41:15","doi":"10.21203/rs.3.rs-6629954/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2025-07-17T11:52:41+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-07-14T12:08:25+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"293746092862206933768764503506809552191","date":"2025-07-11T05:13:36+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-07-10T18:31:46+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-05-13T13:21:25+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-05-13T11:49:47+00:00","index":"","fulltext":""},{"type":"submitted","content":"Arthritis Research \u0026 Therapy","date":"2025-05-09T15:12:52+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"arthritis-research-and-therapy","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"arrt","sideBox":"Learn more about [Arthritis Research \u0026 Therapy](http://arthritis-research.biomedcentral.com/)","snPcode":"13075","submissionUrl":"https://submission.nature.com/new-submission/13075/3","title":"Arthritis Research \u0026 Therapy","twitterHandle":"@ArthritisRes","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"BMC/SO AJ","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"86546b20-d4f0-4ef6-9e87-d6831b3bcc28","owner":[],"postedDate":"July 14th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2025-11-17T15:59:52+00:00","versionOfRecord":{"articleIdentity":"rs-6629954","link":"https://doi.org/10.1186/s13075-025-03665-x","journal":{"identity":"arthritis-research-and-therapy","isVorOnly":false,"title":"Arthritis Research \u0026 Therapy"},"publishedOn":"2025-11-14 15:57:12","publishedOnDateReadable":"November 14th, 2025"},"versionCreatedAt":"2025-07-14 11:41:15","video":"","vorDoi":"10.1186/s13075-025-03665-x","vorDoiUrl":"https://doi.org/10.1186/s13075-025-03665-x","workflowStages":[]},"version":"v1","identity":"rs-6629954","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-6629954","identity":"rs-6629954","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}