The Use of Signal Phase in Dynamic Contrast-Enhanced Magnetic Resonance Imaging.

摘要

Tissue perfusion describes nutrient delivery to a capillary bed within a given time frame. An understanding of the perfusion characteristics of a tissue can provide useful physiological information about the state of that tissue, particularly in oncology, where rapidly growing tumours tend to be surrounded by a large number of highly permeable capillaries, which leads to measurable changes in the parameters describing tissue perfusion. These parameters can be measured non-invasively using dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI). This exam involves imaging the patient as a bolus of contrast agent passes through the tissue. To obtain these parameters, information about the concentration of this contrast agent as a function of time in an input artery, called an arterial input function (AIF) is required. Current methods use the magnitude of the MR signal to make this measurement, but these methods are susceptible to significant inaccuracies. The phase of the MR signal can also be used to measure the required input, but, despite several advantages over the MR signal magnitude method, its application has received little attention in the literature.;In conclusion, the use of the MR signal phase for the calculation of the arterial input function in dynamic contrast-enhanced magnetic resonance imaging was shown to be feasible and to provide superior results to conventional approaches.;The purpose of this work was to explore the feasibility of measuring the AIF, using MR signal phase in DCE-MRI exams of tissue perfusion. Initially, issues relating to the implementation of this technique were addressed. Phantom experiments were performed to validate the technique for different clinically relevant set-ups. The geometry of the vessel is an important consideration for accurate measurements using phase. Two methods for incorporating the geometry of the vessel were validated through simulation and phantom studies. The phase technique was then validated in two clinical studies; a brain tumour study and a prostate tumour study. The results showed that more reasonable AIFs could be obtained by using the phase method versus the magnitude method.