Bio-SCOPE: fast biexponential T1ρ mapping of the brain using signal-compensated low-rank plus sparse matrix decomposition

Purpose To develop and evaluate a fast imaging method based on signal-compensated low-rank plus sparse matrix decomposition to accelerate data acquisition for biexponential brain T-1 rho mapping (Bio-SCOPE). Methods Two novel strategies were proposed to improve reconstruction performance. A variable-rate undersampling scheme was used with a varied acceleration factor for each k-space along the spin-lock time direction, and a modified nonlinear thresholding scheme combined with a feature descriptor was used for Bio-SCOPE reconstruction. In vivo brain T-1 rho mappings were acquired from 4 volunteers. The fully sampled k-space data acquired from 3 volunteers were retrospectively undersampled by net acceleration rates (R) of 4.6 and 6.1. Reference values were obtained from the fully sampled data. The agreement between the accelerated T-1 rho measurements and reference values was assessed with Bland-Altman analyses. Prospectively undersampled data with R = 4.6 and R = 6.1 were acquired from 1 volunteer. Results T-1 rho-weighted images were successfully reconstructed using Bio-SCOPE for R = 4.6 and 6.1 with signal-to-noise ratio variations rho measurements were in good agreement for R = 4.6 (T-1 rho(s): 18.6651 +/- 1.7786 ms; T-1 rho(l): 88.9603 +/- 1.7331 ms) and R = 6.1 (T-1 rho(s): 17.8403 +/- 3.3302 ms; T-1 rho(l): 88.0275 +/- 4.9606 ms) in the Bland-Altman analyses. T-1 rho parameter maps from prospectively undersampled data also show reasonable image quality using the Bio-SCOPE method. Conclusion Bio-SCOPE achieves a high net acceleration rate for biexponential T-1 rho mapping and improves reconstruction quality by using a variable-rate undersampling data acquisition scheme and a modified soft-thresholding algorithm in image reconstruction.