Variable flip angle-based fast three-dimensionalT1mapping for delayed gadolinium-enhanced MRI of cartilage of the knee: Need forB1correction

Delayed gadolinium-enhanced MRI of cartilage is a technique, which involves T(1) mapping to identify changes in the structural integrity of cartilage associated with osteoarthritis. Currently, the gold standard is 2D inversion recovery turbo spin echo, which suffers from long acquisition times and limited coverage. Three-dimensional variable flip angle (VFA) is an alternate technique, which has been shown to be accurate when an estimate of T(1) is available a priori. This study validates the variable flip angle method for delayed gadolinium-enhanced MRI of cartilage of the femoro-tibial knee cartilage. When amplitude of (excitation) radiofrequency field inhomogeneities were minimized using nonselective pulses and amplitude of (excitation) radiofrequency field correction using an additional acquisition of a amplitude of (excitation) radiofrequency field map, the accuracy of T(1) measurements were improved, and slice-to-slice variations over the 3D volume were minimized. In conclusion, fast 3D T(1) mapping using the variable flip angle method with amplitude of (excitation) radiofrequency field correction appears to be an efficient and accurate method for delayed gadolinium-enhanced MRI of cartilage of the knee.