Reliability and reproducibility of sciatic nerve magnetization transfer imaging and T2 relaxometry

Abstract

Objectives To assess the interreader and test-retest reliability of magnetization transfer imaging (MTI) and T2 relaxometry in sciatic nerve MR neurography (MRN). Materials and methods In this prospective study, 21 healthy volunteers were examined three times on separate days by a standardized MRN protocol at 3 Tesla, consisting of an MTI sequence, a multi-echo T2 relaxometry sequence, and a high-resolution T2-weighted sequence. Magnetization transfer ratio (MTR), T2 relaxation time, and proton spin density (PSD) of the sciatic nerve were assessed by two independent observers, and both interreader and test-retest reliability for all readout parameters were reported by intraclass correlation coefficients (ICCs) and standard error of measurement (SEM). Results For the sciatic nerve, overall mean ± standard deviation MTR was 26.75 ± 3.5%, T2 was 64.54 ± 8.2 ms, and PSD was 340.93 ± 78.8. ICCs ranged between 0.81 (MTR) and 0.94 (PSD) for interreader reliability and between 0.75 (MTR) and 0.94 (PSD) for test-retest reliability. SEM for interreader reliability was 1.7% for MTR, 2.67 ms for T2, and 21.3 for PSD. SEM for test-retest reliability was 1.7% for MTR, 2.66 ms for T2, and 20.1 for PSD. Conclusions MTI and T2 relaxometry of the sciatic nerve are reliable and reproducible. The values of measurement imprecision reported here may serve as a guide for correct interpretation of quantitative MRN biomarkers in future studies. Key Points • Magnetization transfer imaging (MTI) and T2 relaxometry of the sciatic nerve are reliable and reproducible. • The imprecision that is unavoidably associated with different scans or different readers can be estimated by the here presented SEM values for the biomarkers T2, PSD, and MTR. • These values may serve as a guide for correct interpretation of quantitative MRN biomarkers in future studies and possible clinical applications.

Quantitative MR-Neurography at 3.0T: Inter-Scanner Reproducibility

“…Furthermore, we calculate a measurement error for T2 of SEM = 4.1 ms when using different MR scanners. This value may be compared to a previously reported SEM of 2.7 ms for repeated measurements on the exact same MR scanner (Preisner et al, 2021). This observation becomes even more relevant when calculating the minimum detectable difference (MDD, equals 2.8 × SEM), which can help to decide whether an observed difference may likely be attributed measurement error, or whether it really indicates a change in the true value (Popovic and Thomas, 2017).…”

“…The SEM estimates measurement precision independently of the sample variance and is expressed in the same physical unit as the measured quantity, thereby providing a more useful framework for decision making in clinical practice (Popovic and Thomas, 2017). The expected measurement error, which is associated with different readers (interreader) and repeated scans (test-retest) without switching between different MR scanners, has been estimated in recent studies and corresponding SEM values have been calculated for various quantitative MRN parameters (Preisner et al, 2019(Preisner et al, , 2021. The SEM values observed in our study, which accounts for the use of different MR scanners, demonstrate a slightly higher measurement error compared to interreader and test-retest observations with one particular MR scanner.…”

“…Subsequently, region-of-interest (ROI) based manual nerve segmentation was performed for seven centrally located slices of the image slab using the high-resolution T2-weighted images in which the borders of the nerve were clearly identifiable. Similar approaches have been used in various studies of systemic neuropathies (Kronlage et al, 2017b;Simon et al, 2017;Lichtenstein et al, 2018) and healthy volunteers (Preisner et al, 2019(Preisner et al, , 2021. To avoid the inclusion of perineurial fat, nerve segmentation was restricted to the tibial portion of the sciatic nerve.…”

“…While many of them have been proposed to produce valuable MR-biomarkers, they still have not been implemented in clinical routine yet, since it is essential to prove their reliability and reproducibility upon application. Preferably, the measurement error that is expected in different situations should be quantified in order to obtain orientation values regarding the precision of quantitative MRN techniques since the use of different hardware, software and/or readers are known to influence quantitative parameters (Guggenberger et al, 2012(Guggenberger et al, , 2013Preisner et al, 2019Preisner et al, , 2021. Furthermore, normative data is dependent on imaging parameters, demographic variables and post-processing algorithms (Chen et al, 2019;Hofstadler et al, 2019;Kronlage et al, 2019b).…”

“…Furthermore, normative data is dependent on imaging parameters, demographic variables and post-processing algorithms (Chen et al, 2019;Hofstadler et al, 2019;Kronlage et al, 2019b). Recent studies have shown that DTI and T2 relaxometry of peripheral nerves provide reliable results when considering different readers or repetitive scans (Andreisek et al, 2010;Tagliafico et al, 2011;Ho et al, 2017;Preisner et al, 2019Preisner et al, , 2021. However, those studies were conducted on identical MR scanners.…”