Quantifying Microvascular Structure in Healthy and Infarcted Rat Hearts Using Optical Coherence Tomography Angiography.

Myocardial infarction (MI) is a life-threatening medical emergency resulting in coronary microvascular dysregulation and heart muscle damage. One of the primary characteristics of MI is capillary loss, which plays a significant role in the progression of this cardiovascular condition. In this study, we utilized optical coherence tomography angiography (OCTA) to image coronary microcirculation in fixed rat hearts, aiming to analyze coronary microvascular impairment post-infarction. Various angiographic metrics are presented to quantify vascular features, including the vessel area density, vessel complexity index, vessel tortuosity index, and flow impairment. Pathological differences identified from OCTA analysis are corroborated with histological analysis. The quantitative assessments reveal a significant decrease in microvascular density in the capillary-sized vessels and an enlargement for the arteriole/venule-sized vessels. Further, microvascular tortuosity and complexity exhibit an increase after myocardial infarction. The results underscore the feasibility of using OCTA to offer qualitative microvascular details and quantitative metrics, providing insights into coronary vascular network remodeling during disease progression and response to therapy.

Semi-automated registration and segmentation for gingival tissue volume measurement on 3D OCT images.

The change in gingival tissue volume may be used to indicate changes in gingival inflammation, which may be useful for the clinical assessment of gingival health. Properly quantifying gingival tissue volume requires a robust technique for accurate registration and segmentation of longitudinally captured 3-dimensional (3D) images. In this paper, a semi-automated registration and segmentation method for micrometer resolution measurement of gingival-tissue volume is proposed for 3D optical coherence tomography (OCT) imaging. For quantification, relative changes in gingiva tissue volume are measured based on changes in the gingiva surface height using the tooth surface as a reference. This report conducted repeatability tests on this method drawn from repeated scans in one patient, indicating an error of the point cloud registration method for oral OCT imaging is 63.08 ± 4.52µm (1σ), and the measurement error of the gingival tissue average thickness is -3.40 ± 21.85µm (1σ).

Quantitative shear-wave optical coherence elastography with a programmable phased array ultrasound as the wave source.

The purpose of this study is to implement a beam-steering ultrasound as the wave source for shear-wave optical coherence elastography (SW-OCE) to achieve an extended range of elastic imaging of the tissue sample. We introduce a linear phased array ultrasound transducer (LPAUT) as the remote and programmable wave source and a phase-sensitive optical coherence tomography (OCT) as the sensitive shear-wave detector. The LPAUT is programmed to launch acoustic radiation force impulses (ARFI) focused at desired locations within the range of OCT imaging, upon which the elasticity map of the entire OCT B-scan cross section is recovered by spatial compounding of the elastic maps derived from each launch of AFRIs. We also propose a directional filter to separate the shear-wave propagation at different directions in order to reduce the effect of tissue heterogeneity on the shear-wave propagation within tissue. The feasibility of this proposed approach is then demonstrated by determining the stiffness of tissue-mimicking phantoms with agarose concentrations of 0.5% and 1% and also by imaging the Young's modulus of retinal and choroidal tissues within a porcine eye ball ex vivo. The approach opens up opportunities to combine medical ultrasound imaging and SW-OCE for high-resolution localized quantitative assessment of tissue biomechanical property.