A novel fast knee cartilage segmentation technique for T2 measurements at MR imaging – data from the Osteoarthritis Initiative

SummaryMagnetic resonance imaging (MRI) T2 relaxation time assesses non-invasively cartilage composition and can be used as early biomarker for knee osteoarthritis. Most knee cartilage segmentation techniques were primarily developed for volume measurements in DESS or SPGR sequences. For T2 quantifications, these segmentations need to be superimposed on T2 maps. However, given that these procedures are time consuming and require manual alignment, using them for analysis of T2 maps in large clinical trials like the Osteoarthritis Initiative (OAI) is challenging.A novel direct segmentation technique (DST) for T2 maps was therefore developed. Using the DST, T2 measurements were performed and compared with those determined with an established segmentation superimposition technique (SST). MR images of five OAI participants were analysed with both techniques three times by one reader and five different images sets additionally with DST three times by two readers.Segmentations and T2 measurements of one knee required on average 63±3min with DST (vs 302±13min for volume and T2 measurements with SST). Bland–Altman plots indicated good agreement between the two segmentation techniques, respectively the two readers. Reproducibility errors of both techniques (DST vs SST) were similar (P>0.05) for whole knee cartilage mean T2 (1.46% vs 2.18%), laminar (up to 2.53% vs 3.19%) and texture analysis (up to 8.34% vs 9.45%). Inter-reader reproducibility errors of DST were higher for texture analysis (up to 15.59%) than for mean T2 (1.57%) and laminar analysis (up to 2.17%). Due to these results, the novel DST can be recommended for T2 measurements in large clinical trials like the OAI