Quantitative Computed Tomography Evaluation of the Abdominopelvic Vasculature in the Domestic Sheep Model

Presenter: Faysal Amin, University of Minnesota – ESS

Introduction:
Vascular diseases such as aneurysms, dissections, stenosis affects over 230 million people worldwide annually. A typical treatment approach includes non-invasive endovascular procedures, which require a thorough understanding of vessel anatomy and dimensions to appropriately target affected areas. Computed Tomography (CT) is considered the gold standard imaging modality for both preoperative planning and intraoperative guidance in endovascular procedures. Preclinical evaluation of novel endovascular devices is essential to assess their safety and efficacy, and the sheep model is widely regarded as a suitable large-animal model for such studies. However, there is limited literature detailing the vascular anatomy of the sheep, particularly in the pelvic region. This study aims to map the pelvic arterial and venous vasculature of the adult domestic sheep and establish a reference range for vessel dimensions.

Methods:
Twenty-four adult domestic sheep, aged 10 to 50 months, underwent multimodal sedation with ketamine (10 mg/kg, IM) and propofol (4 mg/kg, IV), followed by intubation and maintenance on inhaled isoflurane (3%) via mechanical ventilation. Each animal was positioned in dorsal recumbency and placed on an intravenous 0.9% saline intravenous drip. Early arterial-phase CT imaging was performed following intravenous injection of a contrast-saline mixture. DICOM images were reviewed using RadiAnt DICOM Viewer, and multiplanar reconstructions of major pelvic arteries and veins were created. Vessel measurements—including x and y diameters, circumference, and cross-sectional area—were recorded at multiple points along each vessel.

Results:
All 24 animals tolerated the procedure and recovered without complication. Multiplanar reconstructions enabled comprehensive analysis of the pelvic vasculature. No statistically significant differences were found between left and right vessels. Weak positive correlations were observed between body weight and both cross-sectional area and circumference across vessels. On average, venous vessels exhibited a 27% larger cross-sectional area compared to arterial vessels.

Conclusion:
This study establishes one of the first detailed reference ranges for pelvic vasculature in the ovine model. By utilizing clinical-grade CT imaging to characterize sheep vascular anatomy, we enhance the ability to evaluate novel endovascular devices and improve the translational relevance of preclinical testing.