Computed diffusion-weighted imaging of the prostate at 3 T: Impact on image quality and tumour detection

Objectives: To investigate the impact of prostate computed diffusion-weighted imaging (DWI) on image quality and tumour detection. Methods: Forty-nine patients underwent 3-T magnetic resonance imaging using a pelvic phased-array coil before prostatectomy, including DWI with b values of 50 and 1,000 s/mm². Computed DW images with b value 1,500 s/mm² were generated from the lower b-value images. Directly acquired b-1,500 DW images were obtained in 39 patients. Two radiologists independently assessed DWI for image quality measures and location of the dominant lesion. A third radiologist measured tumour-to-peripheral-zone (PZ) contrast. Pathological findings from prostatectomy served as the reference standard. Results: Direct and computed b-1,500 DWI showed better suppression of benign prostate tissue than direct b-1,000 DWI for both readers (P ≤ 0.024). However, computed b-1,500 DWI showed less distortion and ghosting than direct b-1,000 and direct b-1,500 DWI for both readers (P ≤ 0.067). Direct and computed b-1,500 images showed better sensitivity and positive predictive value (PPV) for tumour detection than direct b-1,000 images for both readers (P ≤ 0.062), with no difference in sensitivity or PPV between direct and computed b-1,500 images (P ≥ 0.180). Tumour-to-PZ contrast was greater on computed b-1,500 than on either direct DWI set (P < 0.001). Conclusion: Computed DWI of the prostate using b value ≥1,000 s/mm² improves image quality and tumour detection compared with acquired standard b-value images.