Analysis of contrast time-enhancement curves to optimise CT pulmonary angiography.

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.