Cardiac optical coherence tomography

Acute coronary syndromes (ACS) are a major cause of morbidity and mortality in the developed world. The risk of future acute coronary events appears to be largely dependent on the presence of morphologically distinct, atherosclerotic plaques,1 rather than the presence of severely stenotic lesions as assessed by angiography.2 Angiography, however, cannot provide details of the vascular wall and identify these so-called “vulnerable plaques”. To identify, study and potentially treat these lesions many invasive and non-invasive imaging modalities are undergoing evaluation. While techniques such as intravascular ultrasound (IVUS), especially combined with radiofrequency analysis, have been significant developments providing valuable information in this quest, all have the fundamental drawback of inadequate spatial resolution to image important lesion characteristics. With the development of optical coherence tomography (OCT) and the demonstration of its feasibility for intravascular imaging, a technique with micron-scale resolution became a reality, potentially enabling the ability to capture in vivo what was previously seen only through a pathologist’s microscope. Further, with the widespread adaptation of percutaneous coronary intervention (PCI) for the treatment of coronary disease, OCT is also emerging as a promising technology both to image the acute results of PCI and to monitor the response of the vessel wall to stent deployment. With ongoing development of this modality, OCT has the potential to be an important clinical imaging modality, complementary to angiography and IVUS. OCT is the optical analogue of pulse-echo IVUS, where electromagnetic waves using a light source as opposed to acoustic (sound) waves are used to create the image.3 A light source is emitted towards the sample. Information from the echo time delay (time for the light to be reflected back) and the intensity of backscatter of light from internal microstructures with varying optical properties within the sample is used to create the image. The …