High-b-value diffusion-weighted MRI for the detection of prostate cancer at 3 T

To compare tumour visibility on diffusion-weighted (DW) images and the diagnostic performance of the apparent diffusion coefficient (ADC) maps obtained using b-values of 1000, 1500, and 2000 s/mm(2).

Forty patients with biopsy-proven prostate cancer were retrospectively included in the study. DWI was examined under different pairs of b-values (b = 0, 1000 s/mm(2); 0, 1500 s/mm(2); and 0, 2000 s/mm(2)) and apparent diffusion coefficient (ADC) maps were generated with a mono-exponential fitting. The tumour-to-normal tissue [in the peripheral gland and transitional gland, peripheral zone (PZ) and central gland] contrast ratio (CR) and prostate tumour signal-to-noise ratio (SNR) were compared between different b-value DWI images. ADC was measured and areas under the receiver operating characteristic curve (Az) were calculated.

The CR of the tumour-to-PZ/central gland was significantly higher in the b = 1500 s/mm(2) images than in images created using other b-values (both p < 0.01). The tumour SNR was statistically significantly higher in b = 1500 s/mm(2) images than in the other b-value images (p < 0.01), and was significantly higher in b = 1000 s/mm(2) images than in images created at b = 2000 s/mm(2) (p = 0.035). The Az for b = 1500 s/mm(2) was significantly higher than the Az for b = 2000 s/mm(2) in the PZ (p = 0.016) and central gland (p = 0.037), and higher than the Az for b = 1000 s/mm(2), but not reach statistical significance in the PZ (p = 0.16) and in the central gland (p = 0.23).

At 3 T MRI, DWI images and ADC maps using b = 1500 s/mm(2) should be considered more effective than those at b = 2000 s/mm(2) or b = 1000 s/mm(2) for detecting prostate cancer.