Distortion‐free 3D diffusion imaging of the prostate using a multishot diffusion‐prepared phase‐cycled acquisition and dictionary matching
Elisa Roccia, Radhouene Neji, Thomas Benkert, Berthold Kiefer, Vicky Goh, Isabel Dregely
Abstract
Purpose
To achieve three‐dimensional (3D) distortion‐free apparent diffusion coefficient (ADC) maps for prostate imaging using a multishot diffusion prepared‐gradient echo (msDP‐GRE) sequence and ADC dictionary matching.
Methods
The msDP‐GRE sequence is combined with a 3D Cartesian, centric k‐space trajectory with center oversampling. Oversampled k‐space center averaging and phase cycling are used to address motion‐ and eddy current–induced magnitude corruption. Extended‐phase‐graph (EPG) simulations and ADC dictionary matching are used to compensate for T1 effects. To shorten the acquisition time, each volume is undersampled by a factor of two and reconstructed using iterative sensitivity encoding. The proposed approach is characterized using simulations and validated in a kiwifruit phantom, comparing the msDP‐GRE ADC maps obtained using both standard monoexponential fitting and dictionary matching with the clinical standard single‐shot diffusion weighted‐echo planar imaging (ssDW‐EPI) ADC. Initial in vivo feasibility is tested in three healthy subjects, and geometric distortion is compared with anatomical T2‐weighted‐turbo spin echo.
Results
In the kiwifruit phantom experiment, the signal magnitude could be recovered using k‐space center averaging and phase cycling. No statistically significant difference was observed in the ADC values estimated using msDP‐GRE with dictionary matching and clinical standard DW‐EPI (P < .05). The in vivo prostate msDP‐GRE scans were free of geometric distortion caused by off‐resonance susceptibility, and the ADC values in the prostate were in agreement with values found in the published literature.
Conclusion
Nondistorted 3D ADC maps of the prostate can be achieved using a msDP sequence and dictionary matching.