Background and purpose: To 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 methods: Twenty-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. T(1) and T(2) were also measured in these regions.
Results: Significant 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 T(1) increased from 922 to 1,070 ms. In normal peripheral zone, extravascular-extracellular volume increased from 0.21 to 0.52 ml (ml tissue)(-1), and T(2) decreased from 126 to 106 ms. In muscle, both permeability surface area product and T(2) rose, from 0.02 to 0.06 ml (ml tissue)(-1) min(-1) and from 50 to 56 ms, respectively.
Conclusions: Quantitative 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.