Physical Co-registration of Magnetic Resonance Imaging and Ultrasound in vivo

The use of complementary non-invasive imaging modalities has been proposed to track disease progression, particularly cancer, while simultaneously evaluating therapeutic efficacy. A major obstacle is a limited ability to compare parameters obtained from different modalities, especially those from exogenous contrast agents or tracers. We hypothesize that combining Magnetic Resonance Imaging (MRI) and Ultrasound (US) will improve characterization of the tumour microenvironment. In this study, we describe a co-registration apparatus that facilitates the acquisition of a priori co-registered MR and US images in vivo. This apparatus was validated using phantom data and it was found that the US slices can be selected to an accuracy of +/- 100µm translationally and +/- 2 degrees rotationally. Additionally, it was shown that MRI and US may provide complimentary information about the tumour microenvironment, but more work needs to be done to assess repeatability of dynamic contrast enhanced MRI and US.MAS