Estimation of Multiple Tissue Parameters Using the DESS Sequence
(a) T2 estimates obtained with DESS show high correlation with T2 estimates obtained with standard methods. (b) DESS also gives good agreement with standard methods for ADC measurements.
The Double-Echo Steady-State (DESS) sequence, which produces undistorted, SNR-efficient 3D scans, can provide estimates of multiple tissue parameters. The MRI parameters T2 and apparent diffusion coefficient (ADC) have been shown to correlate with cartilage tissue breakdown in diseases such as Osteoarthritis. Obtaining quantitative estimates of these parameters could help with monitoring disease progression and ultimately result in better treatments. The DESS sequence produces two signals with each acquisition, each with a complicated contrast that depends on the scan parameters as well as the tissue parameters T1, T2, and ADC. By running the sequence twice, with different scan parameters, four unique signals are therefore obtained. By comparing the acquired signals, T1, T2, and ADC can be estimated.
Staroswiecki E, Granlund KL, Alley MT, Gold GE, Hargreaves BA. Simultaneous Estimation of T2 and Apparent Diffusion Coefficient in Human Articular Cartilage In Vivo with a Modified Three-Dimensional Double Echo Steady State (DESS) Sequence at 3 T. Magn Reson Med. 2012 Apr;67(4):1086-96.
(a) The two DESS echoes from a scan with low diffusion weighting, combined in a sum-of-squares image. (b) A similar sum-of-squares image with high diffusion weighting. (c) T2 map obtained with DESS. (d) T2 map obtained with a standard scan. (e) ADC map obtained with DESS. (f) ADC map obtained with a standard scan.
Ernesto Staroswiecki and Kristin Granlund are alumni of the BMR group