Regional variations in MR relaxation of hip joint cartilage in subjects with and without femoralacetabular impingement

The objective of this study was to analyze regional variations of magnetic resonance (MR) relaxation times (T-1 rho and T-2) in hip joint cartilage of healthy volunteers and subjects with femoral acetabular impingement (FAI). Morphological and quantitative images of the hip joints of 12 healthy volunteers and 9 FAI patients were obtained using a 3 T MR scanner. Both femoral and acetabular cartilage layers in each joint were semi-automatically segmented on sagittal 3D high-resolution spoiled gradient echo (SPGR) images. These segmented regions of interest (ROls) were automatically divided radially into twelve equal sub-regions (300 intervals) based on the fitted center of the femur head. The mean value of T-1 rho/T-2 was calculated in each sub-region after superimposing the divided cartilage contours on the MR relaxation (T-5 rho/T-2) maps to quantify the relaxation times. Tip and T-2 relaxation times of the femoral cartilage were significantly higher in FAI subjects compared to healthy controls (39.9 +/- 3.3 msec in FAI vs. 35.4 +/- 2.3 msec in controls for Tip (P=0.0020); 33.9 +/- 3.1 msec in FA! vs. 31.1 +/- 1.7 msec in controls for T2 (P = 0.0160)). Sub-regional analysis showed significantly different T-1 rho and T-2 relaxation times in the anterior-superior region (R9) of the hip joint cartilage between subjects with FAI and healthy subjects, suggesting possible regional differences in cartilage matrix composition between these two groups. Receiver operating characteristic (ROC) analysis showed that sub-regional analysis in femoral cartilage was more sensitive in discriminating FAI joint cartilage from that of healthy joints than global analysis of the whole region (T-1 rho: area under the curve (AUC)= 0.981, P = 0.0001 for T-2 sub-region; AUC= 0.901, P=0.002 for whole region; Ty: AUC= 0.976, P = 0.0005 for R9 sub-region; AUC = 0.808, P= 0.0124 for whole region). The results of this study demonstrated regional variations in hip cartilage composition using MR relaxation times (T-1 rho and T-2) and suggested that analysis based on local regions was more sensitive than global measures in subjects with and without FAI. (C) 2013 Elsevier Inc. All rights reserved.