Abstract
Degradation of human ascending thoracic aorta has been visualized with Optical Coherence Tomography (OCT). OCT images of the vessel wall exhibit structural degradation in the media layer of the artery, being this disorder the final trigger of the pathology. The degeneration in the vessel wall appears as low-reflectivity areas due to different optical properties of acidic polysaccharides and mucopolysaccharides in contrast with typical ordered structure of smooth muscle cells, elastin and collagen fibers. An OCT dimension indicator of wall degradation can be generated upon the spatial quantification of the extension of degraded areas in a similar way as conventional histopathology. This proposed OCT marker can offer in the future a real-time clinical perception of the vessel status to help cardiovascular surgeons in vessel repair interventions. However, the delineation of degraded areas on the B-scan image from OCT is sometimes difficult due to presence of speckle noise, variable signal to noise ratio (SNR) conditions on the measurement process, etc. Degraded areas can be delimited by basic thresholding techniques taking advantage of disorders evidences in B-scan images, but this delineation is not optimum in the aorta samples and requires complex additional processing stages. This work proposes an optimized delineation of degraded areas within the aorta wall, robust to noisy environments, based on the iterative application of Otsu’s thresholding method. Results improve the delineation of wall anomalies compared with the simple application of the algorithm. Achievements could be also transferred to other clinical scenarios: carotid arteries, aorto-iliac or ilio-femoral sections, intracranial, etc.
Highlights
Surgical repair of ascending thoracic aneurysms usually involves the substitution of the diseased portion of the aorta by a graft, which has to be sewn onto both cut ends to replace the degraded vessel section that is removed [1]
The degradation of the media aortic layer has been documented as the main cause for the formation of an aneurysm [3], which can lead to death if it suffers from a dissection
Anomalous tissue regions produce different backscattering intensity profiles when imaged with Optical Coherence Tomography (OCT) due to the invasive appearance of acidic polysaccharides and mucopolysaccharides within a typical ordered microstructure of parallel lamellae of smooth muscle cell, elastin and collagen fibers
Summary
Surgical repair of ascending thoracic aneurysms usually involves the substitution of the diseased portion of the aorta by a graft, which has to be sewn onto both cut ends to replace the degraded vessel section that is removed [1]. The media layer provides strength and elasticity to the wall mainly due to Smooth Muscle Cells (SMC) and an organized matrix of collagen and elastin fibers. The degradation of the media aortic layer has been documented as the main cause for the formation of an aneurysm [3], which can lead to death if it suffers from a dissection. Anomalous tissue regions produce different backscattering intensity profiles when imaged with OCT due to the invasive appearance of acidic polysaccharides and mucopolysaccharides within a typical ordered microstructure of parallel lamellae of smooth muscle cell, elastin and collagen fibers
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