Range gated Doppler ultrasound detection of contrast echographic microbubbles for cardiac and great vessel blood flow patterns

Ultrasonic contrast techniques allow tracking of blood flow in patients with cardiac malformations. One problem often encountered in M-mode contrast is inability to generate adequate microbubbles for recording. Theoretically, echo Doppler should be more sensitive for detection of microbubbles. To test this hypothesis, results of 75 saline injections were studied at catheterization in 16 patients by simultaneously recording contrast M-mode and echo Doppler studies. For this part of the investigation, an ATL 500 system was utilized. The M-mode of this system was found to provide identical information to that of a SmithKline. Records were evaluated without identification of the patient. In all instances (n = 20) in which microbubbles were not expected on the basis of flow pattems, none were detected by Doppler. One error occurred for M-mode. Contrast in the direction of flow was visualized in 50 of 55 injections by echo Doppler. In these, a frequency dispersion was present, but even more striking was a marked rise in the time interval histographic input signal strength indicator. Only 40 of 55 simultaneous M-mode echoes showed a contrast effect (p < 0.05). Doppler microbubble detection was usually represented by a much stronger signal than was M-mode contrast. This investigation demonstrates that range gated Doppler is an effective method for microbubble detection.