Temporal resolution of dynamic angiography using flat panel volume CT: in vivo evaluation of time-dependent vascular pathologies.

BACKGROUND AND PURPOSE Recently introduced fpVCT scanners can capture volumetric (4D) time-varying projections enabling whole-organ dynamic CTA imaging. The main objective of this study was to assess the temporal resolution of dynamic CTA in discriminating various phases of rapid and slow time-dependent neurovascular pathologies in animal models. MATERIALS AND METHODS Animal models were created to assess phasic blood flow, subclavian steal phenomena, saccular aneurysms, and neuroperfusion under protocols approved by the SRAC. Animals with progressively increasing heart rate-Macaca sylvanus (~100 bpm), Oryctolagus cuniculus (NZW rabbit) (~150 bpm), Rattus norvegicus (~300 bpm), Mus musculus (~500 bpm)-were imaged to challenge the temporal resolution of the system. FpVCT, a research prototype with a 25 × 25 × 18 cm coverage, was used for dynamic imaging with the gantry rotation time varying from 3 to 5 seconds. Volumetric datasets with 50% temporal overlap were reconstructed; 4D datasets were analyzed by using the Leonardo workstation. RESULTS Dynamic imaging by using fpVCT was capable of demonstrating the following phenomena: 1) subclavian steal in rabbits (ΔT ≅ 3-4 seconds); 2) arterial, parenchymal, and venous phases of blood flow in mice (ΔT ≅ 2 seconds), rabbits (ΔT ≅ 3-4 seconds), and Macaca sylvanus (ΔT ≅ 3-4 seconds); 3) sequential enhancement of the right and left side of the heart in Macaca sylvanus and white rabbits (ΔT ≅ 2 seconds); and 4) different times of the peak opacification of cervical and intracranial arteries, venous sinuses, and the jugular veins in these animals (smallest, ΔT ≅ 1.5-2 seconds). The perfusion imaging in all animals tested was limited due to the fast transit time through the brain and the low contrast resolution of fpVCT. CONCLUSIONS Dynamic imaging by using fpVCT can distinguish temporal processes separated by >1.5 seconds. Neurovascular pathologies with a time constant >1.5 seconds can be evaluated noninvasively by using fpVCT.