Detection of air emboli in radiographic contrast media by microwave radiometry.

To evaluate the efficacy of a microwave radiometry system in detecting in-line air emboli in radiographic contrast media, air emboli ranging in volume from 0.1 to 0.005 ml were introduced into ionic (ioxaglate) and nonionic (iohexol) contrast media at 22 or 37 degrees pumped at flow rates of 16.7, 180 or 300 ml/min through polyvinlychloride tubing with an inner diameter of 0.100 inches (2.54 mm) over which was fitted a radiometer antenna connected to a Microwave Medical System F+ radiometer and a computerized data acquisition system. A total of 400 determinations were run, with 10 replicate determinations for each unique set of experimental conditions. The success of air emboli detection was not significantly related to contrast media (p = 0.73) or contrast temperature (p = 0.68). Embolus volume (p < 0.0001) and pump speed (p < 0.0001) were significant factors affecting system performance. The system could reliably detect small (0.005 ml) emboli in both ionic and nonionic low-osmolar contrast media.