Utilizing Quantitative MRI for Morphological Assessment of Articular Cartilage Thickness in the Tibiofemoral Joint

Post-traumatic osteoarthritis (PTOA) develops following severe knee trauma like anterior cruciate ligament (ACL) injury. PTOA can be identified by measuring morphology (thickness) and matrix composition of articular cartilage. Morphological MRI has been used to measure cartilage thickness, while quantitative magnetic resonance imaging (qMRI) has been used to measure cartilage matrix composition. In hopes of utilizing a single MRI technique to obtain both measurements simultaneously, this study explored whether cartilage thickness measurements from qMRI sequences were comparable to those from a morphological MRI sequence. Healthy participants with atraumatic, normal knees underwent three MRI acquisitions on their left knee: a three-dimensional (3D) morphological MRI sequence (T1-weighted Fast Field Echo [T1FFE]) and two 3D quantitative MRI sequences (T1ρ, T2*). The images were manually segmented to characterize the articular cartilage surface and subchondral bone-cartilage interface. 3D articular cartilage thickness maps were developed for each acquisition for the lateral and medial compartments of the tibia and femur. The qMRI thickness maps were compared to the morphological MRI thickness maps within subjects at fixed anatomical points. T1ρ cartilage thickness maps showed strong agreement with T1FFE maps as evidenced by ICCs exceeding 0.8 for 11 of 12 regions of interest (ROIs). In addition, mean thickness differences smaller than the in-plane pixel size of the reconstructed images, indicated minimal bias. There was inferior agreement between the T2* and T1FFE maps, and statistically significant bias observed for 8 of 12 ROIs. T1ρ qMRI sequences can simultaneously provide quantitative and comparable morphological measurements of knee articular cartilage thickness.