MRI Characterization of Peripheral Arterial Disease for Planning Percutaneous Vascular Interventions

摘要

Peripheral arterial disease (PAD) is a common, chronic problem with significant morbidity and mortality. When PAD is severe, it is called "critical limb ischemia" and in this subset of patients up to 40% require a major amputation within just one year of diagnosis. Current treatment options involve revascularizing the leg through either bypass surgery or percutaneous vascular intervention (PVI). PVI offers a less invasive approach with improved morbidity and shorter length of hospital stay compared to surgery. However, PVI has high immediate technical failure rates (20%) and high re-intervention rates (~30%). The most common mode of immediate technical failure is the inability to enter or cross the target lesion due to the mechanical properties of the lesion. With current imaging, it is impossible to predict which lesions will be soft enough to cross with a wire to make PVI possible.;This thesis addresses gaps in knowledge about how to appropriately select patients for PVI using novel imaging techniques. We have developed an MRI method using ultrashort echo time and steady state free precession flow-independent imaging that characterizes hard versus soft peripheral arterial lesion components and related those characteristics to ease of crossing during PVI.;We performed ex-vivo studies using high-resolution MRI to define the signal behavior of individual lesion components and demonstrated high diagnostic accuracy by comparing images with microCT and histology. Further, we demonstrated that MRI signal behaviour could differentiate lesions that required high guidewire puncture forces from lesions that are easy to puncture. We translated this technique to a clinical protocol and validated images of amputated limbs with ex-vivo high-resolution MRI, microCT and histology. Finally, we imaged patients with the clinical protocol prior to their PVI, and demonstrated that MRI could identify lesions that took significantly longer to cross with a guidewire and required stenting more often. This thesis presents an original contribution to knowledge with the development and validation of a new MRI diagnostic test that can determine which peripheral arterial lesions are more difficult to cross with a guidewire. Future work will determine if MRI lesion characterization can predict long-term endovascular outcomes to aid procedure planning.