Optimization of quantitative time-resolved 3D (4D) digital subtraction angiography in a porcine liver model.

Background: Time-resolved three-dimensional digital subtraction angiography (4D-DSA) can be used to quantify blood velocity. Contrast pulsatility, a major discriminant on 4D-DSA, is yet to be optimized. We investigated the effects of different imaging and injection parameters on sideband ratio (SBR), a measure of contrast pulsatile strength, within the hepatic vasculature of an in vivo porcine model.

Methods: Fifty-nine hepatic 4D-DSA procedures were performed in three female domestic swine (mean weight 54 kg). Contrast injections were performed in the common hepatic artery with different combinations of imaging duration (6 s or 12 s), injection rates (from 1.0 to 2.5 mL/s), contrast concentration (50% or 100%), and catheter size (4 Fr or 5 Fr). Reflux was recorded. SBR and vessel cross-sectional areas were calculated in 289 arterial segments. Multiple linear mixed-effects models were estimated to determine the effects of parameters on SBR and cross-sectional vessel area.

Results: Twelve-second acquisitions yielded a SBR higher than 6 s (p < 0.001). No significant differences in SBR were seen between different catheter sizes (p = 0.063) or contrast concentration (p = 0.907). For higher injection rates (2.5 mL/s), SBR was lower (p = 0.007) and cross-sectional area was higher (p < 0.001). Reflux of contrast does not significantly affect SBR (p = 0.087).

Conclusions: The strength of contrast pulsatility used for flow quantitation with 4D-DSA can be increased by adjusting injection rates and using longer acquisition times. Reduction of contrast concentration to 50% is feasible and reflux of contrast does not significantly hinder contrast pulsatility.