Optimizing contrast protocol for bone-subtraction CT angiography of intracranial arteries in normal dogs using 160-slice CT.

Abstract

Bone-subtraction computed tomography angiography (CTA) (BSCTA) is a new technique designed to overcome the limitation of three-dimensional CTA, where the vessels surrounded by bone and calcification can be obscured. An optimal contrast CT protocol for intracranial artery visualization with BSCTA has yet to be established in dogs. The purpose of this study was to determine the optimal contrast protocol of CTA for visualizing intracranial artery using an automatic bone-subtraction technique in dogs. Brain CTA was performed four times for each of nine healthy beagle dogs to cover all the contrast protocols: two different contrast iodine concentrations (300 and 370mgI/mL) and two different contrast media injection rates (2 and 4mL/s). Bone removal post-processing was performed automatically by subtracting the non-enhanced CT data from the contrast CT data using a dedicated workstation. The bone-subtracted intracranial vessels were analysed for quantitative and qualitative evaluation. Quantitative evaluation showed significantly higher CT attenuation values for the group with a 370mgI/mL iodine content at a rate of 4mL/s than the two groups with a 300mgI/mL iodine content at the rates of 2 and 4mL/s (p<0.001). Qualitative assessment revealed significantly higher mean scores for the 370mgI/mL groups than the 300mgI/mL groups and significantly higher mean scores for the 4mL/s groups than the 2mL/s groups (p<0.05). The optimal contrast protocol for BSCTA suggests that high iodine material concentration and high injection rate should be used for strong arterial attenuation and great visualization of the intracranial arterial structure in dogs.