Datasets and analysis methods used in this study.
| Image Dataset | Dataset | Segmentation of Cartilage Surfaces | Calculation of Cartilage Thickness | Used For |
|---|---|---|---|---|
| Training | 379 segmentations of femur and tibial cartilage at a single timepoint, on fat-saturated 3-D MR images (range of radiographic OA structural severity, including medial compartment | Manual segmentation using EndPoint (Imorphics), supervised by experienced segmenter1 | ACRAC | Training set for supervised machine learning step in AQ-CART |
| Kellgren-Lawrence grades 0–4, lateral compartment OA, plus young healthy knees) | Thickness is measured at multiple points along normals from the bone surface (Figure 1B2 | Correlation and agreement of mean cartilage thickness in cMF and cMT regions, automated or manual segmentations, miss-25%-out models | ||
| Repeatability | 19 test-retest images of knees with and without radiographic OA (pilot study for the OAI)3 | NA | ACRAC | Repeatability of automated segmentation |
| Biomarkers | 582 segmentations of femur and tibial cartilage at baseline, 1, and 2 yrs (JSN Only Progressors, n = 102; JSN and Pain Progressors, n = 183; Pain Only Progressors, n = 101; No JSN or Pain Progression, n = 196)* | Manual segmentation by Chondrometrics, supervised by experienced segmenter4,5 | Volume of cartilage divided by region of bone5 | Cross-sectional agreement of mean cartilage thickness in cMF and cMT regions, using automated or manual segmentation, baseline images only |
| Longitudinal agreement of change in mean cartilage thickness from baseline in the same regions, using automated or manual segmentation | ||||
| Responsiveness of automated and manual segmentation in the same regions using pairwise Student t test and SRM |
↵* Key to 4 subgroups: JSN progressors (“JSN Only Progressors”), both JSN and pain progressors (“JSN and Pain Progressors”), pain progressors (“Pain Only Progressors”), and nonprogressors (“No JSN or Pain Progressors”). JSN: joint space narrowing; MR: magnetic resonance; OA: osteoarthritis; (AQ)-CART: automatic quantification of cartilage; cMF: central medial femur; cMT: central medial tibia; OAI: OA Initiative; ACRAC: Anatomically Corresponded Regional Analysis of Cartilage; SRM: standardized response means; NA: not applicable.