Gregor Jost

Contrast timing in computed tomography: Effect of different contrast media concentrations on bolus geometry

OBJECTIVE To assess the effect of low-osmolar, monomeric contrast media with different iodine concentrations on bolus shape in aortic CT angiography. MATERIALS AND METHODS Repeated sequential computed tomography scanning of the descending aorta of eight beagle dogs (5 male, 12.7±3.1kg) was performed without table movement with a standardized CT scan protocol. Iopromide 300 (300mgI/mL), iopromide 370 (370mgI/mL) and iomeprol 400 (400mgI/mL) were administered via a foreleg vein with an identical iodine delivery rate of 1.2gI/s and a total iodine dose of 300mgI/kg body weight. Time-enhancement curves were computed and analyzed. RESULTS Iopromide 300 showed the highest peak enhancement (445.2±89.1 HU), steepest up-slope (104.2±17.5 HU/s) and smallest full width at half maximum (FWHM; 5.8±1.0s). Peak enhancement, duration of FWHM, enhancement at FWHM and up-slope differed significantly between iopromide 300 and iomeprol 400 (p<0.05). Except for enhancement at FWHM there were no significant differences between iopromide 300 and iopromide 370 and iopromide 370 and iomeprol 400 (p>0.05). CONCLUSIONS Low viscous iopromide 300 results in a better defined bolus with a significantly higher peak enhancement, steeper up-slope and smaller FWHM when compared to iomeprol 400. These characteristics potentially affect contrast timing.

New Tungsten Cluster Based Contrast Agents for X-ray Computed Tomography

In recognition of the seminal contributions of F. A. Cotton and A. Bino to the field of aqueous chemistry of organometallic, trinuclear cluster compounds of tungsten, we describe their modifications and use as contrast agents for X-ray computed tomography. To enable their fundamental work for an advantageous diagnostic application in medicine a new generation of polydentate W3O2 complexes with improved hydrolytical stability has been synthesized and characterized. The applicability as new metal based contrast agent has been demonstrated in a computed tomography angiography animal study with increased signal intensity. Especially the bis tridentate W3O2 complexes with their reduced stereochemical complexity represent a promising new class in the field of X-ray contrast agents.

Experimental studies on artifacts and tumor enhancement on gadoxetic acid-enhanced arterial phase liver MRI in a rabbit VX2 tumor model

Background Rapid injection of gadoxetic acid is reported to produce more frequent artifacts and lower vascular enhancement on arterial phase liver magnetic resonance imaging (MRI). However, its effect on tumor enhancement and the mechanism of the artifacts remain unclear. Purpose To evaluate the effect of rapid injection of gadoxetic acid on artifacts and tumor enhancement during arterial phase liver MRI, and on arterial blood gases (ABGs) which may explain the cause of the artifacts. Material and Methods ABG analysis was performed in 13 free-breathing rabbits after rapid injection (1 mL/s; injection time = 0.6–0.8 s) of gadoxetic acid (0.025 mmol/kg). Dynamic liver MRI was performed in six anesthetized rabbits with VX2 tumors under a ventilation stoppage after rapid and slow injection (0.25 mL/s; injection time = 2.4–3.2 s) of gadoxetic acid. Artifacts and signal enhancement on arterial phase imaging were compared with those obtained after rapid injection of gadopentetic acid (Gd-DTPA, 0.1 mmol/kg) using a Friedman test or Kruskal–Wallis test. Results ABG analysis did not find any significant changes. Artifacts were not related to injection protocols (P = 0.95). Aortic enhancement with slow injection of gadoxetic acid was significantly higher than that with rapid injection (P < 0.05), and was comparable to that with Gd-DTPA injection. Tumor enhancement obtained with gadoxetic acid was not significantly different between rapid and slow injection, and was significantly lower than that with Gd-DTPA injection (P < 0.05). Conclusion Rapid injection of gadoxetic acid did not affect ABGs and may not be the cause of the artifacts. It lowered vascular enhancement but not arterial tumor enhancement.