A COMPARISON BETWEEN IEEC, A NEW BIODEGRADABLE PARTICULATE CONTRAST-MEDIUM, AND IOHEXOL IN A TUMOR-MODEL OF COMPUTED-TOMOGRAPHY IMAGING OF THE LIVER

RATIONALE AND OBJECTIVES. Higher contrast between normal and pathologi c tissues in the liver may enable detection of smaller lesions in comp uted tomography (CT). This can be obtained using a liver-specific cont rast medium. The authors evaluate a new agent, IEEC thyl-acetylamino-2 ,4,6-triiodobenzenecarboxylate), in an animal model, as a potential co ntrast agent for CT scanning of the liver. The IEEC particulate contra st medium used is based on a prodrug ester design of metrizoic acid an d accumulates rapidly in the liver. The particles are quickly degraded into well-known metabolites and excreted from the body. METHODS. Two groups of rabbits were inoculated with VX2-carcinoma directly into the liver by laparotomy. Computed tomography imaging studies were carried out 9 and 11 days after the inoculation. The investigation was design ed as a crossover study. The first group was imaged both as controls ( without contrast medium) and with the particulate contrast medium on t he 9th day and with iohexol on the 11th day. The second group was imag ed with iohexol on the 9th day and as controls, and with the particula te contrast medium on the Ilth day. The contrast medium was administer ed in a dose of 100 mgI/kg. Iohexol was administered in a dose of 570 mgI/kg according to a standard clinical scheme in use at a radiology d epartment for dynamic CT. Changes in normal liver/lesion contrast and the conspicuity of tumors were assessed. On completion of imaging stud ies on day 11, all animals were killed. The liver was removed and eval uated for the presence of tumors. RESULTS. At macroscopic inspection, all rabbits were found to have tumors ranging from 2 to 14 mm in diame ter. The size and location of the tumors corresponded well with the CT images. In the images where the particulate contrast medium was used, the attenuation in the normal liver parenchyma and the contrast betwe en normal liver and lesion was significantly higher compared with the images where iohexol was used or the controls. For all tumor sizes, th e lesion detection capability with the particulate contrast medium was significantly higher compared with iohexol (P < .005) and controls (P < .05). CONCLUSIONS. VX2-carcinoma in rabbit liver is a useful model for studying the efficacy of contrast media in CT imaging. The particu late contrast medium IEEC improved visualization of liver tumors.