Simultaneous Estimation of T2 and ADC in Human Articular Cartilage In Vivo with a Modified 3D DESS Sequence at 3 T

摘要

T2-mapping and diffusion-weighted imaging complement morphological imaging for assessing cartilage disease and injury. The double echo steady state (DESS) sequence has been used for morphological imaging and generates two echoes with markedly different T2 and diffusion weighting. Modifying the spoiler gradient area and flip angle in DESS allows greater control of the diffusion weighting of both echoes. Data from two acquisitions with different spoiler gradient areas and flip angles are used to simultaneously estimate the T2 and apparent diffusion coefficient (ADC) of each pixel. This method is verified in phantoms and validated in vivo in the knee; estimates from different regions of interest in the phantoms and cartilage are compared to those obtained using standard spin-echo (SE) methods. The Pearson correlations were 0.984 for T2 (~2% relative difference between SE and DESS estimates) and 0.997 for ADC (~1% relative difference between SE and DESS estimates) for the phantom study and 0.989 for T2 and 0.987 for ADC in regions of interest in the human knee in vivo. High accuracy for simultaneous 3D T2 and ADC measurements are demonstrated, while also providing morphologic 3D images without blurring or distortion in reasonable scan times.