Increased signal intensity of prostate lesions on high b-value diffusion-weighted images as a predictive sign of malignancy.

OBJECTIVES: The evaluation of lesions detected in prostate magnetic resonance imaging (MRI) with increased signal intensity (SI) on high b-value diffusion-weighted images as a sign of malignancy.
METHODS: One hundred and three consecutive patients with prostate MRI examination and MRI-guided in-bore biopsy were retrospectively included in the study. MRI-guided in-bore biopsy histologically confirmed prostate cancer in 50 patients (n = 92 lesions). The other 53 patients (n = 122 lesions) had negative bioptical results.
RESULTS: In patients with histologically confirmed prostate cancer, 46 of the 92 lesions had visually increased SI on the high b-value images compared with the peripheral zone (SI = +27 ± 16%) or the central gland (SI = +37 ± 19%, P < 0.001 respectively). In patients with a negative biopsy, ten of the 122 lesions had visually increased SI (compared with the peripheral zone, SI = +29 ± 18%, and with the central gland, SI = +41 ± 15%, P < 0.001 respectively). Neither the apparent diffusion coefficient (ADC) values nor the Gleason Score of lesions with increased SI were significantly different from lesions without increased SI.
CONCLUSIONS: Visually increased SI on the high b-value images of diffusion-weighted imaging using standard b-values is a sign of malignancy but can occasionally also be a feature of benign lesions. However, it does not indicate more aggressive tumours. KEY POINTS: • Diffusion weighted magnetic resonance imaging is increasingly used to diagnose prostatic cancer • Reduced signal intensity (SI) on apparent diffusion coefficient (ADC) mapping is characteristic • Prostatic tumours usually exhibit increased SI on high b-value images • But benign lesions can also yield increased SI on high b-value images.