Four-Dimensional (4D) Volume-Based Bolus-Tracking Monitoring for Post-endovascular Aneurysm Repair CT: Feasibility of...

Purpose The purpose of this study was to evaluate the feasibility of a four-dimensional (4D) bolus tracking (BT) workflow for post-endovascular aortic repair (EVAR) aortic CT that combines volume-based 4D monitoring with high-resolution CT angiography (CTA) in a single examination. Methods We retrospectively analyzed 35 patients who underwent EVAR and 4D-BT-guided aortic CTA. The 160-mm dynamic volume monitoring acquisition was initiated 15 seconds after contrast injection, and the main helical CTA was triggered when the descending aortic regions of interest (ROI) exceeded 400 Hounsfield Units (HU) (switching time, 7-8 seconds). We assessed arterial CT attenuation at six sites, cardiac chamber attenuation for timing assessment, and radiation dose (CT dose index (CTDIvol)/dose length product (DLP)). Results The mean aortic attenuation exceeded 350 HU at all six measurement sites in all cases, with no significant differences among the locations. Cardiac chamber attenuation increased from the right atrium (175 HU) to the pulmonary artery (220 HU) and left atrium (305 HU), supporting consistent arterial phase timing. The mean CTDIvol/DLP was 3.32 mGy/53.2 mGy·cm for volume-based 4D monitoring and 3.2 mGy/255 mGy·cm for CTA; the time-enhancement curve (TEC) peak attenuation exceeded 800 HU in two cases. Conclusion In this feasibility study, the 4D-BT workflow provided reproducible arterial enhancement and consistent trigger-based timing while acquiring both 4D-CTA and CTA datasets in a single session. The diagnostic performance for endoleak detection and the net benefit of contrast load and radiation dose require confirmation in comparative prospective studies.