Blood Velocity Calculated From Volumetric Dynamic Computed Tomography Angiography

Abstract

Though functional intravascular parameters such as blood velocity and direction of blood flow are available via imaging modalities such as Doppler ultrasound and phase contrast magnetic resonance imaging, such quantitative information is not yet supported by computed tomography (CT). In this study, we examined a method to calculate intra-arterial blood velocity from contrast-enhanced dynamic CT angiography (4D CTA) using the unique advantages of a volumetric 320 detector row scanner. Contrast boluses were injected into a flow phantom under volumetric 4D CTA examination. Two pipe diameters were tested, each diameter with 4 various flow velocities, creating 8 independent flow conditions. The internal carotid arteries of 5 patients (10 arteries in total) were subjected to a similar dynamic CTA examination and reconstructed with a 1-second temporal resolution through the arterial phase. Intraluminal velocities were calculated using distance between 2 regions of interest placed proximally and distally over the vessel, divided by delay in time to peak of contrast arrival in each region of interest. Results were compared with flow velocities attained by quantitative magnetic resonance angiography in vivo. Phantom experiments demonstrate reasonable agreement between calculated and measured intraluminal velocity (P = 0.05). Similarly, in vivo blood velocity calculations in all internal carotid arteries show agreement with results attained by quantitative magnetic resonance angiography. Intraluminal blood velocity may be estimated from first-pass contrast bolus profiles acquired via volumetric 4D CTA examinations.