In Vivo Differentiation of Complementary Contrast Media at Dual-Energy CT

Abstract

Purpose:To evaluate the feasibility of using a commercially available clinical dual-energy computed tomographic (CT) scanner to differentiate the in vivo enhancement due to two simultaneously administered contrast media with complementary x-ray attenuation ratios. Materials and Methods:Approval from the institutional animal care and use committee was obtained, and National Institutes of Health guidelines for the care and use of laboratory animals were observed. Dual-energy CT was performed in a set of iodine and tungsten solution phantoms and in a rabbit in which iodinated intravenous and bismuth subsalicylate oral contrast media were administered. In addition, a second rabbit was studied after intravenous administration of iodinated and tungsten cluster contrast media. Images were processed to produce virtual monochromatic images that simulated the appearance of conventional single-energy scans, as well as material decomposition images that separate the attenuation due to each contrast medium. Results:Clear separation of each of the contrast media pairs was seen in the phantom and in both in vivo animal models. Separation of bowel lumen from vascular contrast medium allowed visualization of bowel wall enhancement that was obscured by intraluminal bowel contrast medium on conventional CT scans. Separation of two vascular contrast media in different vascular phases enabled acquisition of a perfectly coregistered CT angiogram and venous phaseenhanced CT scan simultaneously in a single examination. Conclusion:Commercially available clinical dual-energy CT scanners can help differentiate the enhancement of selected pairs of complementary contrast media in vivo.

Extravasated Contrast Material in Penetrating Abdominopelvic Trauma: Dual-Contrast Dual-Energy CT for Improved Diagnosis—Preliminary Results in an Animal Model

“…Further development of complementary contrast materials for human use can bring these benefits to clinical imaging. work builds on the findings of our recent in vivo study, which showed that appropriately selected pairs of vascular or vascular and enteric contrast material can be distinguished and digitally separated by means of DE CT (9). The dual-contrast DE CT technique has many potential benefits, including reduced radiation dose in multiphase studies and improved evaluation of bowel wall enhancement in positive enteric contrast material-enhanced imaging.…”

“…To distinguish an enteric contrast medium from iodinated vascular contrast medium optimally, the enteric contrast medium must contain heavy atoms that both attenuate x-rays well and have attenuation ratios substantially different from the attenuation ratio of iodine. Such atoms include bismuth, tungsten, tantalum, and gold (8,9).…”

“…Because there are no enteric contrast media with attenuation ratios different from that of iodine that are approved for clinical use at the doses required for imaging, we used a rabbit trauma model in this study. Bismuth subsalicylate was selected as the enteric contrast medium because it is readily available and has been shown to be an effective enteric contrast medium in phantoms (10) and in vivo (9). We investigated the diagnostic performance of X -ray computed tomography (CT) has become the cornerstone in the evaluation of the hemodynamically stable patient with penetrating trauma to the abdomen or pelvis (1-3).…”

Complementary contrast media for metal artifact reduction in dual-energy computed tomography

“…22,24 Although the biological properties of tungsten are less well understood, tungsten agents have also been identified as potential CT contrast agents and were used in preclinical DECT imaging. 23,32 Other high-Z elements with potential as possible CT contrast agents include gold, 33,34 ytterbium, 35 and gadolinium. 36 In the interest of simplicity, these elements were not considered in the current study; but based on our consistent findings for the high-Z elements we tested and the increased image contrast compared to iodine at higher energies for other high-Z elements, 19 one would expect that they, too, would exhibit the characteristic of contrast retention at high-keV levels compared to iodine in VMS images at higher energy levels.…”

“…The aim of this study was to evaluate a representative selection (Table 1) of conventional and novel CT contrast elements either in development [22][23][24][25] or in routine clinical use. The nearthreefold difference in k edge energy between different elements was anticipated to result in widely varying attenuation profiles over the 40 to 140 keV range.…”