Investigation of Regional Influence of Magic-Angle Effect on T2 in Human Articular Cartilage with Osteoarthritis at 3 T

Rationale and Objectives: The objectives of this research study were to determine the magic-angle effect on different subregions of in vivo human femoral cartilage through the quantitative assessment of the effect of static magnetic field orientation (B-0) on transverse (T-2) relaxation time at 3.0 T. Materials and Methods: Healthy volunteers (n = 5; mean age, 36.4 years) and clinical patients (n = 5; mean age, 64 years) with early ostearthritis (OA) were scanned at 3.0-T magnetic resonance using an 8-channel phased-array knee coil (transmit-receive). Results: The T-2 maps revealed significantly greater values in anterior than in posterior regions. When the cartilage regions were oriented at 55 degrees to B-0 (magic angle), the longest T-2 values were detected in comparison with the neighboring regions oriented 90 degrees and 180 degrees (0 degrees) to B-0. The subregions oriented 180 degrees (0 degrees) to B-0 showed the lowest T-2 values. Conclusions: The differences in T-2 values of different subregions suggest that magic-angle effect needs to be considered when interpreting cartilage abnormalities in OA patients.