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Distortion-free 3D diffusion imaging of the prostate using a multi-shot diffusion-prepared phase-cycled acquisition and dictionary matching

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Elisa Roccia, Radhouene Neji, Thomas Benkert, Berthold Kiefer, Vicky Goh, Isabel Dregely

King's Authors

Abstract

Purpose: To achieve 3D distortion-free ADC maps for prostate imaging using a multi-shot diffusion-prepared GRE sequence (msDP-GRE) 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 graphs (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 2 and reconstructed using iterative SENSE. 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 against the clinical standard single-shot DW-EPI ADC. Initial in-vivo feasibility is tested in 3 healthy subjects, and geometric distortion is compared against anatomical T2w-TSE. 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<0.05). The in-vivo prostate msDP-GRE scans were free of geometric distortion due to off-resonance susceptibility, and the ADC values in the prostate were in agreement with literature values. Conclusion: Non-distorted 3D ADC maps of the prostate can be achieved using a multi-shot diffusion-prepared sequence and dictionary matching.

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