MR DIGITAL SUBTRACTION ANGIOGRAPHY OF LOWER EXTREMITY

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The broad objective of this research is to develop and evaluate contrast enhanced magnetic resonance digital subtraction angiography (MRDSA) for rapid, noninvasive and accurate imaging of arterial diseases in the lower extremity. Accurate and non-invasive MRDSA would be a cost-effective alternative for evaluating peripheral vascular disease. The specific aims are 1) develop integrated 3D and 2D MRDSA techniques, 2) develop strategies for imaging the spectrum of peripheral arterial pathology, 3) evaluate the clinical feasibility of MRDSA in patients with peripheral vascular disease. Both 3D and 2D acquisitions of MRDSA have advantages and limitations for imaging peripheral vascular disease. We plan to overcome their limitations and combine their advantages. Interleaved spiral 3D techniques will be developed to optimize signal-to-noise ratio (SNR), spatial resolution and scan time. 2D sequences will be refined with hadamard encoding, multiple projections, ultra high in-plane resolution, magnetization preparation, and digital filtering. Both 3D and 2D pulses will be integrated into one sequence to provide fast high-resolution arterial imaging without venous contamination. Pathophysiology determines the circulation of the contrast bolus and the imaging needs for therapy. Accordingly, data acquisition of MRDSA will be tailored to pathophysiologic conditions. Patients' disease patterns will be estimated with a timing scan. A bolus chase MRDSA technique and corresponding contrast injection rate will be identified for optimal SNR and spatial resolution and minimal venous contamination. A comprehensive imaging strategy consisting of multi-station bolus chase acquisition and individual station high-resolution acquisition will be developed for imaging a wide range of peripheral vascular disease. The clinical feasibility of MRDSA will be evaluated by comparing it with x-ray angiography in a group of patients with peripheral vascular disease. Successful development of this research will establish MRDSA as an accurate, economic and non-invasive clinical tool for assessing peripheral vascular diseases.