Optimizing Contrast Medium Injection for Coronary CT Angiography Using Myocardial CT Perfusion Data

Abstract

To derive and validate a formula to predict the optimal amount of contrast medium for coronary CT angiography (CTA) from CT perfusion (CTP) data during comprehensive cardiac CT. Materials and Methods: The derivation and validation group consisted of 196 and 41 patients, respectively. Dynamic CTP was performed under adenosine triphosphate stress of 0.14 mg/kg/min, followed by rest coronary CTA. Time to peak (TTP) and peak enhancement (PE) in the left ventricle during CTP was recorded. The amount of contrast medium during CTA was 0.8×body weight (kg) in the derivation group. A formula to determine the amount of contrast medium needed to achieve an enhancement of 370 Hounsfield unit (HU) in CTA was derived using TTP, PE, body weight, and heart rate. The amount of contrast medium required during CTA in the validation group was determined by this formula. Results: The mean amount of contrast medium during CTA did not differ between the derivation and validation groups (49.3±8.0 mL vs. 47.9±12.9 mL, p=0.39). The mean coronary artery enhancement was slightly lower in the validation group (400±55 HU vs. 380±46 HU, p=0.03) with smaller interpatient variability (p=0.02) than in the derivation group. The proportion of patients with an optimal enhancement of 320 HU to 420 HU significantly increased from 54% to 75% (p=0.01) when the formula was used. Conclusion: Adjusting the amount of contrast medium using dynamic CTP data could reduce the interpatient variability of coronary enhancement during comprehensive cardiac CT.