Description of magnetic resonance imaging-derived enhancement variables in pathologically confirmed prostate cancer and normal peripheral zone regions.

OBJECTIVE: To assess the use of a semiquantitative analysis of dynamic contrast-enhanced (DCE) magnetic resonance imaging (MRI) to produce indices for enhancement curves that might enable differentiation between malignant prostatic lesions and normal peripheral zone (PZ). PATIENTS AND METHODS: Fifty-two patients scheduled for radical prostatectomy underwent DCE-MRI before surgery using a 3 T scanner. The DCE images were used to generate variables from changes in signal intensity for pathologically confirmed malignant areas and the normal PZ, using whole-mounted pathology specimens as a reference to delineate regions of interest (ROI). These variables included maximum enhancement index (MaxEI), time to MaxEI at 30 s, the initial and final slopes of signal intensity change, and the area under curve. A threshold value for each DCE variable was identified, and the sensitivity and specificity were obtained.
RESULTS: Malignant lesions had a 56% higher MaxEI than normal PZ and took half the time to reach MaxEI (P<0.001). Hence, at 30 s, cancer lesions have double the mean (sd) EI than normal PZ, of 2.22 (1.04) vs 1.04 (0.51), respectively. Tumours showed significant washout of contrast medium, which was reflected in the final slope of the curve being negative, as opposed to positive for normal PZ. The combined data of DCE variables, using a logistic regression test, gave a mean (95% confidence interval) sensitivity and specificity of 89 (81-96)% and 90 (83-97)%, respectively.
CONCLUSION: This technique provides good discrimination of malignant lesions that might enable accurate localisation of the lesion. It is a simple, semiquantitive, noninvasive method that reflects the unusual vascular characteristics of newly formed microvessels and the changes in the interstitium that occur in prostate cancer.