Utilization of Intra-arterial Contrast for Abdominal Computed Tomography in a Swine Model

Abstract

Intraoperative computed tomography (CT) imaging with endovascular catheter delivery of intra-arterial (IA) contrast could potentially provide higher signal attenuation in directed anatomic locations with lower contrast volumes. We compared image quality and attenuation timing of IA vs intravenous (IV) contrast protocols for abdominal imaging. Five anesthetized swine had internal jugular access and ascending aortic pigtails placed percutaneously via the brachial artery. The IV contrast protocol utilized 100 mL of iodinated contrast at 5 mL/sec over 20/sec. The IA protocol delivered 50 mL at 5 mL/sec over 10/sec. A 16-slice CT scanner with a 10 mm detector acquired static serial images at 1 image/sec for 45 seconds. Region-of-interest markers were used to select the aorta and portal vein to capture the arterial and portal venous phases of contrast administration via Hounsfield Units (HU) per second. Attenuation curves were plotted against time and assessed using a Pearson correlation. Adequate attenuation was defined as >100 HU a priori, and image quality was assessed using contrast-to-noise ratio (CNR). Both contrast protocols achieved adequate image attenuation with an aortic peak of 665 ± 226 (Mean HU ± standard deviation) for IA and 414 ± 141 for IV. IA contrast achieved faster peak aortic attenuation compared with IV contrast (8 vs 20 seconds; P < .001] (Figure 1). Portal values (attenuation and time to peak) were similar for IA vs IV (146 ± 46 vs 169 ± 39; 34 vs 42 seconds; P < .05) (Figure 2). IA administration achieved a superior CNR in less time compared with IV (10 vs 23 seconds; P < .001). All curves were modeled using non-linear least squares regression and achieved an R2 >0.94; P < .001. IA contrast achieves adequate opacification and a superior CNR compared with IV contrast, while using a smaller volume for organ directed imaging. It is likely that the contrast volume can be reduced further without impacting image quality. Although further work is required to optimize IA contrast CT and abdominal imaging, the incorporation of intraoperative CT with IA contrast could radically change imaging protocols in a variety of clinical settings.Fig 2Averaged Hounsfield units (HUs) over 45 seconds comparing intra-arterial (IA) vs intravenous (IV) contrast attenuation of the portal vein.View Large Image Figure ViewerDownload Hi-res image Download (PPT)