4 research outputs found
Intravascular Polarimetry: Clinical Translation and Future Applications of Catheter-Based Polarization Sensitive Optical Frequency Domain Imaging
Optical coherence tomography (OCT) and optical frequency domain imaging (OFDI)
visualize the coronary artery wall and plaque morphology in great detail. The advent of
these high-resolution intracoronary imaging modalities has propelled our understanding
of coronary atherosclerosis and provided enhanced guidance for percutaneous coronary
intervention. Yet, the lack of contrast between distinct tissue types and plaque
compositions impedes further elucidation of the complex mechanisms that contribute
to acute coronary syndrome (ACS) and hinders the prospective identification of
plaques susceptible to rupture. Intravascular polarimetry with polarization-sensitive
OFDI measures polarization properties of the coronary arterial wall using conventional
intravascular imaging catheters. The quantitative polarization metrics display notable
image contrast between several relevant coronary plaque microstructures that are difficult
to identify with conventional OCT and OFDI. Tissues rich in collagen and smooth
muscle cells exhibit birefringence, while lipid and macrophages cause depolarization.
In this review, we describe the basic principles of intravascular polarimetry, discuss the
interpretation of the polarization signatures, and outline promising avenues for future
research and clinical implications
Neoatherosclerosis development following bioresorbable vascular scaffold implantation in diabetic and non-diabetic swine
Background: DM remains a risk factor for poor outcome after stent-implantation, but little is known if and how DM affects the vascular response to BVS. Aim: The aim of our study was to examine coronary responses to bioresorbable vascular scaffolds (BVS) in swine with and without diabetes mellitus fed a ‘fast-food’ diet (FF-DM and FF-NDM, respectively) by sequential optical coherence tomography (OCT)-imaging and histology. Methods: Fifteen male swine were evaluated. Eight received streptozotocin-injection to induce DM. After 9 months (M), 32 single BVS were implanted in epicardial arteries with a stent to artery (S/A)-ratio of 1.1:1 under quantitative coronary angiography (QCA) and OCT guidance. Lumen, scaffold, neointimal coverage and composition were assessed by QCA, OCT and near-infrared spectroscopy (NIRS) pre- and/or post-procedure, at 3M and 6M. Additionally, polarization-sensitive (PS)-OCT was performed in 7 swine at 6M. After sacrifice at 3M and 6M, histology and polymer degradation analysis were performed. Results: Late lumen loss was high (~60%) within the first 3M after BVS-implantation (P0.20). Neointimal coverage was highly heterogeneous in all swine (DM vs. NDM P>0.05), with focal lipid accumulation, irregular collagen distribution and neointimal calcification. Likewise, polymer mass loss was low (~2% at 3M, ~5% at 6M;P>0.20) and not associated with DM or inflammation. Conclusion: Scaffold coverage showed signs of neo-atherosclerosis in all FF-DM and FF-NDM swine, scaffold polymer was preserved and the vascular response to BVS was not influenced by diabetes
Coronary Plaque Microstructure and Composition Modify Optical Polarization
Objectives: This study aimed to evaluate whether polarimetry, performed using a modified optical frequency domain imaging (OFDI) system, can improve the assessment of histological features relevant to characterizing human coronary atherosclerosis.
Background: The microscopic structure and organization of the arterial wall influence the polarization of the infrared light used by OFDI. Modification of the OFDI apparatus, along with recently developed image reconstruction methods, permits polarimetric measurements simultaneously with conventional OFDI cross-sectional imaging through standard intravascular imaging catheters.
Methods: The main coronary arteries of 5 cadaveric human hearts were imaged with an OFDI system capable of providing polarimetric assessment. Cross-sectional views of tissue birefringence, measured in refractive index units, and depolarization, expressed as the ratio of depolarized signal to total intensity, were reconstructed, together with conventional OFDI images. Following imaging, the vessels underwent histological evaluation to enable interpretation of the observed polarization features of individual tissue components.
Results: Birefringence in fibrous tissue was significantly higher than in intimal tissue with minimal abnormality (0.44 × 10-3 vs. 0.33 × 10-3; p < 0.0001). Birefringence was highest in the tunica media (p < 0.0001), consistent with its high smooth muscle cell content, cells known to associate with birefringence. In fibrous areas, birefringence showed fine spatial features and close correspondence with the histological appearance of collagen. In contrast, necrotic cores and regions rich in lipid elicited significant depolarization (p < 0.0001). Depolarization was also evident in locations of cholesterol crystals and macrophages.
Conclusions: Intravascular measurements of birefringence and depolarization can be obtained using conventional OFDI catheters in conjunction with a modified console and signal processing algorithms. Polarimetric measurements enhance conventional OFDI by providing additional information related to the tissue composition and offer quantitative metrics enabling characterization of plaque features