MRI for prostate cancer: can computed high b-value DWI replace native acquisitions?

ABSTRACT

OBJECTIVE: To compare computed high b-value diffusion-weighted images (c-DWI) derived from low b-value DWI images and acquired high b-value DWI (a-DWI), in overall image quality and prostate cancer detection rate. MATERIALS AND METHODS: A total of 124 consecutive men with suspected prostate cancer (PCa) underwent diagnosis prostate MRI on a 3.0 T MR system using a 32-channel phased-array torso coil. Among them, 63 underwent prostate biopsy. MRI protocol included 3DT2w images, high resolution Fov Optimized and Constrained Undistorted Single-Shot (FOCUS™) DWI images with b-values of 100, 400, 800, and 2000 s/mm2 and dynamic contrast enhanced images. C-DWI images (2000 and 2500 s/mm2) were derived from the three lower acquired b-value DWI images using a mono-exponential diffusion decay. C-DWI and acquired high b-value DWI (a-DWI) (2000 s/mm2) were compared for image quality (background signal suppression, anatomic clarity, ghosting, distortion) and tumor conspicuity by four radiologists. RESULTS: C-DWIs demonstrated higher rating than a-DWIs for overall image quality despite worsened ghosting. In patients with a biopsy, similar detection rate was observed while conspicuity was better with c-DWI (p < 0.001). Non-acquisition of high b-value a-DWI reduced total acquisition time by 220 s per patient. CONCLUSION: C-DWI provides a substantial reduction in acquisition time while maintaining comparable prostate cancer detection rate and improving global image quality. KEY POINTS • Computed DWI improves global quality of prostate MRI. • Computed DWI improves analysis of DWI images with decrease acquisition time. • Computed DWI provides greater background suppression of parenchyma and improves conspicuity of suspicious lesion.