Adaptation of the contrast injection protocol to tube potential for cardiovascular computed tomography

To investigate the adaptation of the contrast injection protocol for lower tube potential at cardiovascular computed tomography (CT) angiography, this study analyzed 83 patients (56 100kV vs. 27 120kV) imaged with a prospectively ECG-triggered axial technique for evaluation of aortic disease on a 256-slice CT scanner from 4/10/12 to 5/23/12. A custom algorithm was used to select tube potential and tube current based on patient size. The same contrast injection protocol (contrast concentration 370 mgI/mL, flow rate = 3.5 mL/s, volume = 90 mL) was applied to both cohorts. A Bae-Heiken-Brink pharmacokinetic model was utilized to simulate attenuation in the aorta for the applied contrast protocol in both cohorts and for 3 reduced volumes in the 100kV cohort (A: 72mL, -20%; B: 60mL, -33%; C: 50mL, -44%). Quantitative analysis revealed that 100kV cohort had significantly higher contrast attenuation and signal-to-noise ratio than the 120kV cohort but similar image noise. Simulation of protocol A and B in the 100kV cohort yielded significantly higher attenuation than that measured from the 120kV cohort (p<0.05); attenuation with protocol C showed no significant difference. Simulation results demonstrated that the amount of contrast material can be reduced by as much as 44% for 100 compared to 120 kV imaging but still yielded similar aortic attenuation. A prospective, randomized study should be conducted to validate the performance of the proposed contrast injection protocol at 100kV.