Percutaneous coronary revascularization of chronic total occlusions (CTOs) is difficult due to the presence of a hard proximal fibrous cap and lack of image guidance. The use of x-ray fluoroscopy alone makes it difficult to identify vessel boundaries and occlusive constituents which would aid the process of revascularization. It also can be difficult to keep a guidewire intraluminal without puncturing the vessel wall. Although several imaging modalities are being developed, a technique for measuring the stiffness of occlusions would facilitate revascularization by helping the process of guidewire selection and placement. In this study, a technique known as static magnetic resonance elastography is explored as a method of determining the compliance of CTOs. A finite element simulation was used to determine the response of an artery to deformation, and displacement images were obtained from an artery phantom using a stimulated echo MR imaging pulse sequence and a pneumatic compression system.

Percutaneous coronary revascularization of chronic total occlusions (CTOs) is difficult due to the presence of a hard proximal fibrous cap and lack of image guidance. The use of x-ray fluoroscopy alone makes it difficult to identify vessel boundaries and occlusive constituents which would aid the process of revascularization. It also can be difficult to keep a guidewire intraluminal without puncturing the vessel wall. Although several imaging modalities are being developed, a technique for measuring the stiffness of occlusions would facilitate revascularization by helping the process of guidewire selection and placement. In this study, a technique known as static magnetic resonance elastography is explored as a method of determining the compliance of CTOs. A finite element simulation was used to determine the response of an artery to deformation, and displacement images were obtained from an artery phantom using a stimulated echo MR imaging pulse sequence and a pneumatic compression system.

This thesis presents the first work, to our knowledge, to evaluate the potential of Optical Coherence Tomography (OCT) as an intravascular imaging modality to characterize and guide interventions on chronic total occlusions (CTOs) in arteries. An ex vivo imaging study using OCT is presented that characterizes various pathologies associated with peripheral CTOs and illustrates the ability to differentiate between the vessel wall and the occluded lumen. We also found that, while OCT could image approximately 1mm through tissue, it was effective for imaging deeper through clarified microchannels seen within the occluded lumen. While others had reported observing such microchannels within the lumen before, little was known about the global architecture of these channels. This motivated a study of the global morphology of microchannels in occlusions using micro computed tomography (microCT). In this microCT study, we found that microchannels within the occluded lumen of the artery appeared to be continuous over several millimeters. However, these channels also exited the artery frequently, suggesting the need for some form of imaging guidance. As a potential intravascular imaging set-up, a forward-viewing OCT catheter was built. This catheter uses a novel scanning mechanism that combines high voltage and a dissipative polymer to achieve fast compact actuation. Doppler OCT results are presented using this catheter to image flow in the forward direction. Doppler OCT imaging of microchannels in vivo is also shown in a surgically exposed occluded artery in situ.

This thesis presents the first work, to our knowledge, to evaluate the potential of Optical Coherence Tomography (OCT) as an intravascular imaging modality to characterize and guide interventions on chronic total occlusions (CTOs) in arteries. An ex vivo imaging study using OCT is presented that characterizes various pathologies associated with peripheral CTOs and illustrates the ability to differentiate between the vessel wall and the occluded lumen. We also found that, while OCT could image approximately 1mm through tissue, it was effective for imaging deeper through clarified microchannels seen within the occluded lumen. While others had reported observing such microchannels within the lumen before, little was known about the global architecture of these channels. This motivated a study of the global morphology of microchannels in occlusions using micro computed tomography (microCT). In this microCT study, we found that microchannels within the occluded lumen of the artery appeared to be continuous over several millimeters. However, these channels also exited the artery frequently, suggesting the need for some form of imaging guidance. As a potential intravascular imaging set-up, a forward-viewing OCT catheter was built. This catheter uses a novel scanning mechanism that combines high voltage and a dissipative polymer to achieve fast compact actuation. Doppler OCT results are presented using this catheter to image flow in the forward direction. Doppler OCT imaging of microchannels in vivo is also shown in a surgically exposed occluded artery in situ.