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

Abstract

Magnetic resonance imaging (MRI) T(2) 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 T(2) quantifications, these segmentations need to be superimposed on T(2) maps. However, given that these procedures are time consuming and require manual alignment, using them for analysis of T(2) maps in large clinical trials like the Osteoarthritis Initiative (OAI) is challenging. A novel direct segmentation technique (DST) for T(2) maps was therefore developed. Using the DST, T(2) 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 T(2) measurements of one knee required on average 63±3min with DST (vs 302±13min for volume and T(2) 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 T(2) (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 T(2) (1.57%) and laminar analysis (up to 2.17%). Due to these results, the novel DST can be recommended for T(2) measurements in large clinical trials like the OAI.

Relationship of unilateral total hip arthroplasty (THA) to contralateral and ipsilateral knee joint degeneration – a longitudinal 3T MRI study from the Osteoarthritis Initiative (OAI)

“…T 2 relaxation time detects early degenerative changes of the biochemical composition of cartilage, mainly collagen disruption and increase of the water content [14, 39, 40]. Therefore is able to detect cartilage changes independently of morphological substance loss [8, 9].…”

“…T 2 mapping MSME spin echo sequences, available for all right knees were analyzed on a remote workstation (SPARC; Sun Microsystems, Mountain View, CA) using an in-house software implemented in MATLAB (The Mathworks Inc., Natick, MA) [14–16]. Semi-automated spline-based segmentation was performed by two radiologists (P.M.J.…”

Imaging research results from the Osteoarthritis Initiative (OAI): a review and lessons learned 10 years after start of enrolment

“…A novel cartilage segmentation technique was proposed for simplifying T2 measurements from the MESE sequence 53. Additionally, segmentation software was developed and validated to register DESS to T2 mapping sequences 76…”

Medial femur T2 Z‐scores predict the probability of knee structural worsening over 4–8 years: Data from the osteoarthritis initiative

“…This outcome was defined on a region-level and on a knee level (positive for worsening if an increase occurred in at least one region). The WORMS reproducibility results have been described previously[20, 21]. The inter-observer reproducibility (weighted Kappa) for WORMS scoring for (10 cases, 2 readers) was 0.91 for the patella, 0.91 for the medial femur, 0.86 for the lateral femur, 1.00 for the medial femur, and 0.85 for the lateral tibia.…”

“…T2 quantification was performed at the baseline timepoint. The cartilage T2 reproducibility results have been described previously[20, 21]. The mean T2 values had root mean square (RMS) coefficients of variation (CV) ranging from 0.83% in the medial femur to 3.21% in the patella (intra-reader reproducibility).…”