Strain Ultrasound Elastography of Aneurysm Sac Content after Randomized Endoleak Embolization with Sclerosing vs. Non-sclerosing Chitosan-based Hydrogels in a Canine Model

Abstract

PurposeTo compare the mechanical properties of aneurysm content after endoleak embolization with a chitosan hydrogel (CH) with that with a chitosan hydrogel with sodium tetradecyl sulfate (CH-STS) using strain ultrasound elastography (SUE). Materials and MethodsBilateral common iliac artery type Ia endoleaks were created in 9 dogs. Per animal, 1 endoleak was randomized to blinded embolization with CH, and the other, with CH-STS. Brightness-mode ultrasound, Doppler ultrasound, SUE radiofrequency ultrasound, and computed tomography were performed for up to 6 months until sacrifice. Radiologic and histopathologic studies were coregistered to identify 3 regions of interest: the embolic agent, intraluminal thrombus (ILT), and aneurysm sac. SUE segmentations were performed by 2 blinded independent observers. The maximum axial strain (MAS) was the primary outcome. Statistical analysis was performed using the Fisher exact test, multivariable linear mixed-effects models, and intraclass correlation coefficients (ICCs). ResultsResidual endoleaks were identified in 7 of 9 (78%) and 4 of 9 (44%) aneurysms embolized with CH and CH-STS, respectively (P = .3348). CH-STS had a 66% lower MAS (P < .001) than CH. The ILT had a 37% lower MAS (P = .01) than CH and a 77% greater MAS (P = .079) than CH-STS. There was no significant difference in ILT between treatments. The aneurysm sacs embolized with CH-STS had a 29% lower MAS (P < .001) than those embolized with CH. Residual endoleak was associated with a 53% greater MAS (P < .001). The ICC for MAS was 0.807 (95% confidence interval: 0.754–0.849) between segmentations. ConclusionsCH-STS confers stiffer intraluminal properties to embolized aneurysms. Persistent endoleaks are associated with increased sac strain, an observation that may help guide management.