Reproducibility of Quantitative Double‐Echo Steady‐State T₂ Mapping of Knee Cartilage

BackgroundCartilage T2 can detect joints at risk of developing osteoarthritis. The quantitative double‐echo steady state (qDESS) sequence is attractive for knee cartilage T2 mapping because of its acquisition time of under 5 minutes. Understanding the reproducibility errors associated with qDESS T2 is essential to profiling the technical performance of this biomarker.PurposeTo examine the combined acquisition and segmentation reproducibility of knee cartilage qDESS T2 using two different regional analysis schemes: 1) manual segmentation of subregions loaded during common activities and 2) automatic subregional segmentation.Study TypeProspective.Subjects11 uninjured participants (age: 28 ± 3 years; 8 (73%) female).Field Strength/Sequence3‐T, qDESS.AssessmentTest–retest T2 maps were acquired twice on the same day and with a 1‐week interval between scans. For each acquisition, average cartilage T2 was calculated in four manually segmented regions encompassing tibiofemoral contact areas during common activities and 12 automatically segmented regions from the deep‐learning open‐source framework for musculoskeletal MRI analysis (DOSMA) encompassing medial and lateral anterior, central, and posterior tibiofemoral regions. Test–retest T2 values from matching regions were used to evaluate reproducibility.Statistical TestsCoefficients of variation (%CV), root‐mean‐square‐average‐CV (%RMSA‐CV), and intraclass correlation coefficients (ICCs) assessed test–retest T2 reproducibility. The median of test–retest standard deviations was used for T2 precision. Bland–Altman (BA) analyses examined test–retest biases. The smallest detectable difference (SDD) was defined as the BA limit of agreement of largest magnitude. Significance was accepted for P < 0.05.ResultsAll cartilage regions across both segmentation schemes demonstrated intraday and interday qDESS T2 CVs and RMSA‐CVs of ≤5%. T2 ICC values >0.75 were observed in the majority of regions but were more variable in interday tibial comparisons. Test–retest T2 precision was <1.3 msec. The T2 SDD was 3.8 msec.Data ConclusionExcellent CV and RMSA‐CV reproducibility may suggest that qDESS T2 increases or decreases >5% (3.8 msec) could represent changes to cartilage composition.Level of Evidence2.Technical EfficacyStage 2.