Objectives

To assess the relationship between MRI derived parameters (apparent diffusion coefficient (ADC) and T2 relaxation time) and tumor cellularity as determined from whole mounted radical prostatectomy specimens, for both prostatic carcinoma and normal peripheral zone tissue.

Materials and methods

Over a 16-month period, 20 patients (mean age: 61 years, range: 42-70 years) were prospectively recruited. Diffusion and T2 imaging were performed on a 3.0 Tesla scanner to enable subsequent ADC and T2 calculation. After radical retropubic prostatectomy specimens were whole-mounted and regions of interest (ROIs) drawn in areas of prostatic carcinoma and normal peripheral zone. Cell density was then determined using an adaptive histogram thresholding technique. Differences in tissue type were explored using the unpaired t test while the relationship between parameters was assessed using scatter-plots and the Pearson correlation coefficient.

Results

Significant differences (P < 0.0001 in all cases) were noted between peripheral zone tissue and prostatic carcinoma in terms of ADC (1.88 +/- 0.22 vs. 1.43 +/- 0.19 x 10(-3) mm2/s), T2 (142 +/- 24 vs. 109 +/- 20 milliseconds), and cell density (9.4% +/- 3.0% vs. 19.8% +/- 5.3%). A significant negative correlation with cell density was noted for both ADC (R = -0.695, P < 0.0001) and T2 (R = -0.505, P = 0.001). Trends for increased cell density, decreased ADC, and decreased T2 with increasing Gleason score were also noted.

Conclusions

ADC and to a lesser extent T2 are good indicators of cell density. Because of the potential link with Gleason score, MRI derived parameters may have a prognostic role with regard to potential metastatic activity and tumor aggressiveness.