• Wieke Haakma, Jeroen Hendrikse, Lars Uhrenholt, Alexander Leemans, Lene Warner Thorup Boel, Michael Pedersen, and Martijn Froeling.
• Department of Radiology, University Medical Center Utrecht, Utrecht University, Utrecht, the Netherlands.
• J Magn Reson Imaging. 2018 Oct 1; 48 (4): 951-963.

BackgroundDiffusion tensor imaging (DTI) has been applied in the lumbar and sacral nerves in vivo, but information about the reproducibility of this method is needed before DTI can be used reliably in clinical practice across centers.PurposeIn this multicenter study the reproducibility of DTI of the lumbosacral nerves in healthy volunteers was investigated.Study TypeProspective control series.SubjectsTwenty healthy subjects.Field Strength/Sequence3T MRI. 3D turbo spin echo, and 3.0 mm isotropic DTI scan.AssessmentThe DTI scan was performed three times (twice in the same session, intrascan reproducibility, and once after an hour, interscan reproducibility). At site 2, 1 week later, the protocol was repeated (interweek reproducibility). Fiber tractography (FT) of the lumbar and sacral nerves (L3-S2) was performed to obtain values for fractional anisotropy, mean, axial, and radial diffusivity.Statistical TestsReproducibility was determined using the intraclass correlation coefficient (ICC), and power calculations were performed.ResultsFT was successful and reproducible in all datasets. ICCs for all diffusion parameters were high for intrascan (ranging from 0.70-0.85), intermediate for interscan (ranging from 0.61-0.73), and interweek reliability (ranging from 0.58-0.62). There were small but significant differences between the interweek diffusivity values (P < 0.0005). Depending on the effect size, nerve location, and parameter of interest, power calculations showed that sample sizes between 10 and 232 subjects are needed for cross-sectional studies.Data ConclusionWe found that DTI and FT of the lumbosacral nerves have intermediate to high reproducibility within and between scans. Based on these results, 10-58 subjects are needed to find a 10% change in parameters in cross-sectional studies of the lumbar and sacral nerves. The small significant differences of the interweek comparison suggest that results from longitudinal studies need to be interpreted carefully, since small differences may also be caused by factors other than disease progression or therapeutic effects.Level Of Evidence1 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2018;48:951-963.© 2018 The Authors Journal of Magnetic Resonance Imaging published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine.

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