Identification of vessel wall degradation in ascending thoracic aortic aneurysms with OCT

Abstract

Degradation of the wall of human ascending thoracic aorta has been assessed through Optical Coherence Tomography (OCT). OCT images of the media layer of the aortic wall exhibit micro-structure degradation in case of diseased aortas from aneurysmal vessels. The OCT indicator of degradation depends on the dimension of areas of the media layer where backscattered reflectivity becomes smaller due to a disorder on the morphology of elastin, collagen and smooth muscle cells (SMCs). Efficient pre-processing of the OCT images is required to accurately extract the dimension of degraded areas after an optimized thresholding procedure. OCT results have been validated against conventional histological analysis. The OCT qualitative assessment has achieved a pair sensitivity-specificity of 100%-91.6% in low-high degradation discrimination when a threshold of 4965.88µm 2 is selected. This threshold suggests to have physiological meaning. The OCT quantitative evaluation of degradation achieves a correlation of 0.736 between the OCT indicator and the histological score. This in-vitro study can be transferred to the clinical scenario to provide an intraoperative assessment tool to guide cardiovascular surgeons in open repair interventions.

Enhanced delineation of degradation in aortic walls through OCT

“…Aortic samples can be classified into two different risk categories according to their artery real degradation: low degraded and severe degraded samples. After the segmentation of the images and noise reduction, diagnosis can be performed through a simple computation of the areas of the detected anomalies as a final step after the proposed filtering and thresholding application [5]. Fig.2 shows the analysis with different σ values of two different aortic samples: a heathy aorta from a heart donor (first column) and a pathological aorta with severe degradation (second column).…”

“…2d). This can be associated with cystic change and elastic fragmentation in the wall [3,5]. Anomalies comprehending wide areas (Fig.…”

“…However, the delineation of degraded areas on the B-scan image from OCT is sometimes difficult due to presence of speckle noise, variable SNR conditions on the measurement process, etc. Degraded areas could be outlined by basic thresholding techniques taking advantage of disorders evidences in B-scan images, but this delineation is not always optimum and requires complex additional processing stages [5].…”

Hessian analysis for the delineation of amorphous anomalies in optical coherence tomography images of the aortic wall

“…Five different stains and procedures were applied to each sample: Hematoxylin and Eosin, Verhoeff's Van Gieson, Alcian Blue at pH 2.5 and Alpha-smooth muscle actin [2]. The dimensions and severity of degradation in the aorta wall were measured by expert pathologists, providing the degradation state of the affected regions, quantified with a degradation histology score [1,15], grading from null degradation (score 0) to severe degradation (score 15).…”

“…Resulting OCT images from tissue are equivalent to those obtained with common histology techniques, with the advantages of continuous and fast acquisition, easy incorporation into the surgical procedure but at fairly less resolution. Previous work [2] shows how the OCT approach correlates with the information provided by common histological techniques. Therefore, OCT could provide real-time guidance information about the vessel state under intraoperative conditions if an accurate and automated delineation of degradation is developed.…”