The injection of radiocontrast media into coronary arteries will produce a low incidence of ventricular fibrillation. This study establishes the injection duration (or contact time) required to produce fibrillation during right coronary angiography in dogs using a 370 mg I/ml, meglumine/sodium diatrizoate formulation (Renografin 76, Squibb). The mean contact time required to induce fibrillation was 18.8 +/- 5.8 seconds for 66 injections in 47 dogs. Prolonged ischemia of greater than 170 s did not produce either fibrillation or arrhythmias, therefore fibrillation is caused by properties of the media. The contact time was not significantly influenced by test injections and was not significantly different in repeated experiments. The canine contact time model of contrast media induced ventricular fibrillation is reproducible and will facilitate the study of risk factors that increase the possibility of fibrillation.
Detection of liver metastases by CT scanning depends on both size and difference in attenuation between the metastasis and the surrounding liver parenchyma. VX2 carcinoma cells were injected into the liver parenchyma of rabbits which were subsequently scanned under suspended respiration before, during and after infusion of iothalamate ethyl ester, a particulate contrast agent. The results demonstrate the greater attenuation difference between tumor and parenchyma required for the detection of smaller lesions. Contrast enhancement was most beneficial in the detection of tumors having diameters less than the scan section width.
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