Individualized Delay for Abdominal Computed Tomography Angiography Bolus-Tracking Based on Sequential Monitoring: Increased Aortic Contrast Permits Decreased Injection Rate and Lower Iodine Dose

Objective: The aim of this study was to determine if computed tomography (CT) angiography using an individualized transition delay (CTA-ID) would facilitate reductions in injection rate and iodine dose. Methods: The CTA-ID was performed in 20 patients with routine injection rate and iodine dose; 20 patients with injection rate lowered by 1 mL/s; and 40 patients with injection rate lowered by 1 mL/s with 29% less iodine. Routine CTAs in the same or size-matched patients served as controls. Diagnostic image quality and intra-arterial CT numbers were assessed. Results: The median transition delay between aortic threshold and CTA-ID image acquisition was significantly longer than with conventional bolus tracking (mean increase, 13.3 seconds; P < 0.0001), with image quality being the same or better. Intra-arterial CT numbers were 200 Hounsfield units or greater for 80 of 80 CTA-ID, but not for 6 of 49 (12%) internal control or for 11 of 80 (14%) size-matched control patients. Conclusion: The CTA-ID bolus-tracking software alters transition delays to permit diagnostic CTA examinations despite slower injection rate and less iodine.