Diffusion‐weighted MRI of the prostate without susceptibility artifacts: Undersampled multi‐shot turbo‐STEAM with rotated radial trajectories. (5th March 2019) - Merrem, Andreas
Abstract : The aim of this study was to develop and evaluate a clinically feasible approach to diffusion‐weighted (DW) MRI of the prostate without susceptibility‐induced artifacts. The proposed method relies on an undersampled multi‐shot DW turbo‐STEAM sequence with rotated radial trajectories and a multi‐step inverse reconstruction with denoised multi‐shot phase maps. The total acquisition time was below 6 min for a resolution of 1.4 × 1.4 × 3.5 mm 3 and six directions at b = 600 s mm −2 . Studies of eight healthy subjects and two patients with prostate cancer were performed at 3 T employing an 18‐channel body‐array coil and elements of the spine coil. The method was compared with conventional DW echo‐planar imaging (EPI) of the prostate. The results confirm that DW STEAM MRI avoids geometric distortions and false image intensities, which were present for both single‐shot EPI (ssEPI) and readout‐segmented EPI, particularly near the intestinal wall of the prostate. Quantitative accuracy of the apparent diffusion coefficient (ADC) was validated with use of a numerical phantom providing ground truth. ADC values in the central prostate gland of healthy subjects were consistent with those measured using ssEPI and with literature data. Preliminary results for patients with prostate cancer revealed a correct anatomical localization of lesions with respect to T 2 ‐weighted MRI in both mean DW STEAM images and ADC maps. In summary, DW STEAM MRI of the prostate offers clinically relevant advantages for the diagnosis of prostate cancer compared with state‐of‐the‐art EPI‐based approaches. The method warrants extended clinical trials. Abstract : This work describes a novel approach to diffusion‐weighted MRI of the prostate without susceptibility artifacts. The method relies on a multi‐shot radial turbo‐STEAM sequence and nonlinear inverse reconstruction with denoising of phase maps. The total acquisition time was below 6 min at 1.4 × 1.4 × 3.5 mm 3 resolution and b = 600 s mm −2 . In comparison to diffusion‐weighted echo‐planar imaging, the results for healthy subjects and two patients demonstrate clinically relevant advantages for the diagnosis of prostate cancer.