Diffusion‐weighted MRI of the prostate without susceptibility artifacts: Undersampled multi‐shot turbo‐STEAM with rotated radial trajectories

Abstract

Funding informationDeutsche Krebshilfe e.V.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 readoutsegmented 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-theart EPI-based approaches. The method warrants extended clinical trials.

Diffusion-weighted magnetic resonance imaging (MRI) without susceptibility artifacts: single-shot stimulated echo acquisition mode (STEAM) MRI with iterative reconstruction and spatial regularization

“…The measurement time was 4 min and 30 s when averaging 9 non-DW images and 6 DW images per direction (see 1. which were exclusively designed for studies of the brain (9) or prostate (16).…”

“…Moreover, the present work does not offer any quantitative comparisons, for example to DW EPI. On the other hand, there is previous information about the different performance of STEAM and EPI, e.g., see (8,16), while clinically meaningful comparisons are beyond the scope of this work and will be the subject of forthcoming studies. A final limitation is the focus on healthy volunteers which nevertheless serves the qualitative purpose outlined above.…”