MRI Guided Revascularization of Occlusive Peripheral Arterial Disease
Abstract： MRI is capable of quantitatively measuring the blood flow in the legs with superior visualization of PAD lesions compared with x-ray fluoroscopy, making it an ideal modality for the PAD population.
Occlusive peripheral arterial disease (PAD) is one of the most common cardiovascular diseases with significant morbidity and mortality . Lack of blood flow to the leg causes exertional pain and is associated with poor quality of life and disability [1,2]. When peripheral arterial disease is severe, it is called “critical limb ischemia”. In this subset of patients, major amputation is required within 1 year in up to 40% of patients . Vascular disease in the legs is often indicative of vascular disease in the heart and other areas of the body. This is why up to 20% of these patients die within 6 months from cardiovascular complications .
Current treatment options for PAD involve reestablishing blood flow to the leg through either bypass surgery or percutaneous vascular intervention (PVI). PVI is a less invasive approach with improved mortality, morbidity and shorter length of hospital stay compared to surgery . PVI is guided using x-ray fluoroscopy, which offers very limited visualization of diseased arteries in the leg. Many PAD patients have renal insufficiency  and therefore cannot undergo x-ray fluoroscopy because it requires nephrotoxic contrast. Due to the challenges of PVI, it is currently only recommended for a small proportion of PAD patients, indicating a large under-served population that go on to have morbid bypass surgeries or require amputations.
MRI is capable of producing high quality maps of the blood flow in the legs with superior visualization of PAD lesions compared with x-ray fluoroscopy. MRI has the advantages of not requiring any nephrotoxic contrast or radiation, making it an ideal modality for the PAD population. MRI can significantly advance the field by facilitating PVI to treat more patients with PAD in a minimally invasive way, with the potential of improving amputation rates, disability outcomes and quality of life in this growing patient population.
The current challenges of using MRI for PVI include: 1) poor characterization of calcific PAD plaque components, 2) long acquisition times that are not acceptable to patients and 3) the difficult ergonomic workflow for physicians performing MR guided interventions. Members of our lab are currently addressing these issues by 1) developing ultrashort echo time sequences to effectively characterize calcium, 2) using compressed sensing and parallel imaging techniques for faster acquisition and 3) developing a robust MR-to X-ray registration technique. This will allow physicians to perform PVI using fluoroscopy registered to a previously acquired MR roadmap for improved visualization and the ability to perform the entire procedure without any contrast.
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*Trisha Roy *
Dr. Trisha Roy received her bachelor of engineering and doctor of medicine degrees from the University of Toronto, where she is currently a 3rd year resident specializing in vascular surgery as well as a PhD student under the supervision of Dr. Graham Wright and Dr. Andrew Dueck. She seeks to use MR imaging to treat peripheral arterial disease patients with minimally invasive, non-contrast and radiation-free techniques, and concentrates her research at the Sunnybrook Research Institute. She is on the Board of Directors for the Professional Association of Residents in Ontario and sits on the Ontario Medical Association board.