MRI before and after external beam intensity-modulated radiotherapy of patients with prostate cancer: The feasibility of monitoring of radiation-induced tissue changes using a dynamic contrast-enhanced inversion-prepared dual-contrast gradient echo sequence
Received 8 August 2008; received in revised form 31 July 2009; accepted 11 August 2009. published online 14 September 2009.
Abstract
Purpose
To identify and quantify suitable pharmacokinetic MRI parameters for monitoring tissue changes after external beam intensity-modulated radiotherapy of prostate cancer.
Material and methods
Six patients with biopsy-proven prostate cancer (initial PSA, 6.0–81.4ng/ml) underwent MRI at 1.5T using a combined endorectal/body phased-array coil and a dynamic contrast-enhanced inversion-prepared dual-contrast gradient echo sequence (T1/T2∗w; 1.65s temporal resolution). MRI was performed before and immediately after radiotherapy, at 3months and at 1year. Perfusion, blood volume, mean transit time, delay, dispersion, interstitial volume, and extraction coefficient were calculated in prostate cancer and normal prostate for all four time points using a sequential 3-compartment model.
Results
Prostate cancer and normal prostate tissue showed a statistically significant decrease in perfusion (p=0.006, p=0.001) and increase in extraction coefficient (p=0.004, p<0.001). For prostate cancer, there was also a decrease in vascular volume (p=0.034). The other parameters investigated showed no statistically significant changes. Statistically significant differences between prostate cancer and normal prostate tissue were only observed before radiotherapy, when prostate cancer showed significantly higher perfusion (1.84 vs. 0.12ml/cm3min, p=0.028) and a smaller extraction coefficient (0.42 vs. 0.64, p=0.028).
Conclusions
Two pharmacokinetic parameters, perfusion and extraction coefficient, appear to be suitable candidates for monitoring the response to percutaneous intensity-modulated radiotherapy of prostate cancer.
ABSTRACT