Assessing changes in tumour vascular function using dynamic contrast-enhanced magnetic resonance imaging.

Dynamic contrast-enhanced MRI (DCE-MRI) is widely used in the diagnosis and staging of cancer and is emerging as a promising method for monitoring tumour response to treatment. However, DCE-MR imaging techniques are still evolving and methods of image analysis remain variable and non-standard, and range from relative changes in the pattern of enhancement to pharmacokinetic modelling of contrast agent uptake. The combination of results from different institutions is therefore difficult and the sensitivities of different methods have not been compared. The purpose of this study is to investigate correlations between qualitative and quantitative methods of analysis for DCE-MR images from breast cancer patients undergoing neo-adjuvant chemotherapy. Fifteen patients underwent DCE-MRI examinations before and after one course of chemotherapy. Changes in the temporal pattern of signal enhancement, the rate and amplitude of enhancement and the volume transfer constant of contrast agent between the blood plasma and the extravascular extracellular space (EES), K(trans), and the EES fractional volume, nu(e), were determined. In addition, whole tumour region-of-interest analysis was compared with histogram analysis to investigate the extent of tumour heterogeneity. It was found that changes in the rate of enhancement correlated strongly with changes in K(trans) values (Kendall's tau = 0.68, P < 0.001). Furthermore, it was found that the shape of the signal enhancement curve only changed when the K(trans) values changed by 50% or more. Median K(trans) values determined following histogram analysis of pixel maps of K(trans) were approximately equal to those determined by whole tumour region-of-interest analysis. The absolute change in the K(trans) values correlated negatively with the pre-treatment values, particularly for responding patients. Thus, for higher pre-treatment K(trans) values, a greater decrease was observed. Greater changes were observed in the upper extremes of the K(trans) histogram than in the median values after one course of treatment.