Ultra-Short Echo Time–MRI T2* Mapping of Articular Cartilage Layers Is Associated with Histological Early Degeneration

Abstract

Objective Ultra-short TE (UTE) sequences on MRI are a technique that improves the visualization of tissues with short T2 relaxation time, such as deep cartilage layers. In addition, T2* relaxation time calculated from the UTE has the potential to evaluate water molecules bound to the cartilage matrix. This study was performed to determine if there is an association between UTE-T2* relaxation time by cartilage layer and histological degeneration in knee osteoarthritis (OA). Design Seven knees that had undergone total knee arthroplasty (TKA) were included in the study, and the lateral tibial cartilage, which had the least degeneration of the resected bones, was used as the sample. The T2* relaxation time of 4 patients with no abnormal findings on MRI was the reference relaxation time. Histological degeneration of TKA samples was assessed by the Mankin score and graded as the early OA group (≤3 points) and the advanced OA group (≥4 points). The association between T2* relaxation time and Mankin grade in each cartilage layer was compared. The effect of angiogenesis to the tidemark on T2* relaxation time was also compared. Results T2* relaxation time of the cartilage layer was significantly longer in early OA than that in the control group. In the deep cartilage layer, the mean T2* relaxation time for angiogenesis (−) was 15.7 ms, whereas it was significantly shorter for angiogenesis (+) at 8.2 ms. Conclusions The UTE-T2* relaxation time was associated with histological cartilage degeneration, suggesting a potential application in monitoring early cartilage degeneration.