Author: Mohammed Alzaabi, Owen Thomas Dillon, Julia Johnson, Andrew Kanawati, Tess Reynolds, Ann Yan 👨🔬
Affiliation: Westmead Hospital, Image X Institute, Faculty of Medicine and Health, The University of Sydney, Khalifa University 🌍
Purpose: To develop a physiological carotid artery phantom and Bayesian geometric calibration method to examine the feasibility of extended field-of-view interventional CBCT artery imaging using a multi-turn reverse helical acquisition.
Methods: A 58 cm physical carotid artery phantom was built, comprising of a commercial pulsatile pump, simplified carotid arterial system (7 arteries) from silicone and latex tubes, 3D-printed torso/head shell and vertebrae geometric calibration phantom, and phytagel. An iodine/water solution was circulated in a closed-loop system with a flow rate of 2 litres/minute and heart rate of 60 BPM. The phantom was imaged with both a series of conventional circular acquisitions and a multi-turn reverse helical (MTRH) acquisition. A Bayesian geometric calibration method was developed to provide online calibration of geometric parameters from metallic markers within the 2D X-ray projections of the MTRH acquisition. The amount of cardiac pulsing motion observed in the phantom was quantified via examining linear pixel profiles across the various tubes and comparing to the manufactured specifications with no motion. The differences in the geometric parameters with/without online calibration for the MTRH acquisition was quantified via change in fit residual
Results: The conventional acquisitions had a field-of-view of 17 cm, requiring 4 acquisitions to be stitched together in post-processing using external software to capture the phantom in a single volume. Comparatively, a single MTRH acquisition provide a 60 cm field-of-view. With the pulsatile pump running, the silicone and latex arteries averaged an absolute change in diameter of 0.4±0.4 mm and 0.7±0.3 mm, respectively. The fit residual between the system and online calibrated geometry for the MTRH acquisition was reduced by 36.5%.
Conclusion: Extended field-of-view interventional CBCT artery imaging using a multi-turn reverse helical acquisition is feasible, providing a pathway to visualize entire arterial structures in a single 3D volume in the operating room.