Late tissue effects following radiotherapy and neoadjuvant hormone therapy of the prostate measured with quantitative magnetic resonance imaging

Background and PurposeTo use quantitative MRI to detect changes in the vascular and MR relaxation characteristics of the prostate gland 1 year after external beam radiotherapy.Materials and methodsTwenty-one patients underwent MRI before and after external beam radiotherapy for prostatic adenocarcinoma. Tracer kinetics analysis was applied to data from regions of interest in prostate tumour, normal prostate peripheral zone and muscle to obtain estimates of blood flow, extravascular–extracellular volume, blood volume and capillary permeability surface area product. T1 and T2 were also measured in these regions.ResultsSignificant changes (p < 0.05) after radiotherapy were found in all three tissues examined. Tumour blood flow was 0.34 and 0.14 ml (ml tissue)−1 min−1 before and after treatment, respectively, and T1 increased from 922 to 1070 ms. In normal peripheral zone, extravascular–extracellular volume increased from 0.21 to 0.52 ml (ml tissue)−1, and T2 decreased from 126 to 106 ms. In muscle, both permeability surface area product and T2 rose, from 0.02 to 0.06 ml (ml tissue)−1 min−1 and from 50 to 56 ms, respectively.ConclusionsQuantitative MRI can be used to measure significant changes in both vascular and MR relaxation properties of the prostate and nearby muscle following treatment for prostate cancer using external beam radiotherapy.