Analysis of contrast time–enhancement curves to optimise CT pulmonary angiography

Abstract

Aim To assess enhancement profiles of the pulmonary artery (PA) and determine optimal scan timing in PA computed tomography (CT) angiography. Materials and methods One hundred consecutive patients referred for contrast-enhanced chest CT were prospectively studied. Fifteen low-radiation monitoring images were acquired at 2-second intervals, 5 seconds after the start of an injection of 370 mg iodine/I contrast medium for 1 ml/kg of body weight injected over 20 seconds. Contrast time–enhancement data were measured over the PA. The time and magnitude of peak as well as times to five different enhancement thresholds (50, 100, 150, 200, 250 HU) were calculated. A set of candidate fixed and circulation-adjusted scan delays were analysed and compared in terms of the quality of contrast enhancement over the 4-second diagnostic scan duration. Results The mean degree of peak PA enhancements was 431.4±65.2HU (range, 263.8–575.3HU). The mean time to peak enhancement was 22.4±3.1 seconds (range, 11–27 seconds). From potential fixed delays ranging 11–27 seconds, 19 seconds showed the highest enhancement quality. For the circulation-adjusted delays, the combination of 150 HU bolus-track threshold with diagnostic delay of 10 seconds had the highest enhancement quality. Conclusion Peak enhancement of PA occurred, on average, right after completion of contrast injection for 20 seconds. The fixed scan delay of 19 seconds or circulation-adjusted delay with the bolus-threshold of 150 HU and diagnostic delay of 10 seconds appear optimal.