Optimization of intra-voxel incoherent motion imaging at 3.0 Tesla for fast liver examination

Background Optimization of multi b-values MR protocol for fast intra-voxel incoherent motion imaging of the liver at 3.0 Tesla. Methods A comparison of four different acquisition protocols were carried out based on estimated IVIM (D_Slow, D_Fast, and f) and ADC-parameters in 25 healthy volunteers. The effects of respiratory gating compared with free breathing acquisition then diffusion gradient scheme (simultaneous or sequential) and finally use of weighted averaging for different b-values were assessed. An optimization study based on Cramer-Rao lower bound theory was then performed to minimize the number of b-values required for a suitable quantification. The duration-optimized protocol was evaluated on 12 patients with chronic liver diseases Results No significant differences of IVIM parameters were observed between the assessed protocols. Only four b-values (0, 12, 82, and 1310 s.mm^-2) were found mandatory to perform a suitable quantification of IVIM parameters. D_Slow and D_Fast significantly decreased between nonadvanced and advanced fibrosis (P<0.05 and P<0.01) whereas perfusion fraction and ADC variations were not found to be significant. Conclusion Results showed that IVIM could be performed in free breathing, with a weighted-averaging procedure, a simultaneous diffusion gradient scheme and only four optimized b-values (0, 10, 80, and 800) reducing scan duration by a factor of nine compared with a nonoptimized protocol. Preliminary results have shown that parameters such as D_Slow and D_Fast based on optimized IVIM protocol can be relevant biomarkers to distinguish between nonadvanced and advanced fibrosis. J. Magn. Reson. Imaging 2014.