High-frequency optical coherence tomography predictors of aneurysm occlusion following flow diverter treatment in a preclinical model

Abstract

BackgroundHigh-frequency optical coherence tomography (HF-OCT) is an intravascular imaging method that allows for volumetric imaging of flow diverters in vivo.ObjectiveTo examine the hypothesis that a threshold for both volume and area of communicating malapposition can be predictive of early aneurysm occlusion.MethodsFifty-two rabbits underwent elastase aneurysm formation, followed by treatment with a flow diverter. At the time of implant, HF-OCT was acquired to study the rate and degree of communicating malapposition. Treated aneurysms were allowed to heal for either 90 or 180 days and euthanized following catheter angiography. Healing was dichotomized into aneurysm remnant or neck remnant/complete occlusion. Communicating malapposition was measured by HF-OCT using a semi-automatic algorithm able to detect any points where the flow diverter was more than 50 µm from the vessel wall. This was then summed across image slices to either a volume or area. Finally, a subsampled population was used to train a statistical classifier for the larger dataset.ResultsNo difference in occlusion rate was found between device type or follow-up time (p=0.28 and p=0.67, respectively). Both volume and area of malapposition were significantly lower in aneurysms with a good outcome (p<0.001, both). From the statistical model, a volume of less than 0.56 mm3 or a normalized area less than 0.69 as quantified by HF-OCT was predictive of occlusion (p<0.001, each).ConclusionsHF-OCT allows for measurements of both volume and area of malapposition and, from these measurements, an accurate prediction for early aneurysm occlusion can be made.

Role of optical coherence tomography in pipeline embolization device for the treatment of vertebral–basilar artery dissecting aneurysms

“…Compared with imaging modalities such as DSA, high frequency OCT volume microscopy has obvious advantages in quantifying intraluminal clots and evaluating the interaction between neurovascular devices and arterial walls 21. High frequency OCT could also accurately predict early aneurysm occlusion based on quantification of measurement of both volume and area of malapposition 22. As OCT technology continues to improve, we believe that current limitations could be better overcome and that this new technology will be widely, safely, and effectively used in the neurovascular field.…”

Evaluation of the apposition in unruptured aneurysms treated with flow diverters by optical coherence tomography: Preliminary clinical experience

“…To our knowledge, the concept of the length of CM was first proposed by us, and evaluating and defining the severity of CM and classifying it by quantitative means may facilitate to analyze and establish an effective model for predicting aneurysm occlusion by OCT method for FD treatment of intracranial aneurysms, and also deepen the understanding of aneurysm occlusion and parent artery remodeling ( 10 ). A recent study suggests that early aneurysm occlusion can be accurately predicted by calculating the area and volume of malapposition in the OCT images ( 7 ). However, most of the available OCT devices do not allow immediate intraoperative calculation of area or volume indexes, which is not favorable for rapid intraoperative evaluation of the relationship between the degree of malapposition and prognosis and determination of whether malapposition needs to be improved by additional surgical strategies (balloon dilation, remedial stent placement, etc.).…”

“…Currently, no standardized thresholds have been established for the definition of poor FD apposition. Some have defined an FD-to-wall distance of >50 μm (approximately 1.5 times strut thickness) as malapposition ( 7 ), but the relationship between this threshold and clinical outcomes is not well understood. Threshold values that are too low may have more false-positive results in identifying malapposition.…”

“…All patients completed imaging collection such as DSA, Vaso CT, and OCT immediately after the FD fully and smoothly inserted, and the degree of stent apposition was evaluated based on the above various imaging techniques, of which communicating malapposition (CM) was defined as poor apposition (distance between FD and vessel wall >200 µm) (7) to clinical experience and the results of OCT imaging evaluation and taking into consideration the safety of the procedure, the surgeon decides whether to continue or end the operation. The patient's baseline features (age and sex), aneurysm features (location, type, neck width, maximum height, maximum diameter, proximal and distal reference diameter of the parent artery), surgical details (type, size, and number of FDs used, and whether coil embolization is applied), and OCT image features during the perioperative period were collected for further comparative analysis (Table 1).…”

“…All patients completed imaging collection such as DSA, Vaso CT, and OCT immediately after the FD fully and smoothly inserted, and the degree of stent apposition was evaluated based on the above various imaging techniques, of which communicating malapposition (CM) was defined as poor apposition (distance between FD and vessel wall >200 μm) ( 7 ) that continues to the aneurysm neck. According to clinical experience and the results of OCT imaging evaluation and taking into consideration the safety of the procedure, the surgeon decides whether to continue or end the operation.…”