144 COMPARISON OF THE SENSITIVITY OF M-MODE CONTRAST AND DOPPLER CONTRAST

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 micro-bubbles for recording. To test if echo Doppler is more sensitive than M-mode for detection of microbubbles, results of 63 saline injections were studied at catheterization in 12 patients by simultaneously recording contrast M-mode and echo Doppler studies. Seven other injections were studied with a prototype (PROTO) two-dimensional echo Doppler system (Honeywell). Records were evaluated without identification of the patient. Contrast in the direction of flow was visualized in 61 of 63 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 36/61 simultaneous M-mode echoes showed a contrast effect (p<.05). In 24 of the disagreements, the M-mode showed no contrast effect whereas the Doppler correctly demonstrated the presence of microbubbles. The PROTO system used Fourier analysis and displayed microbubbles as a low level signal with marked frequency dispersion over the flow pattern. An important difference between M-mode and echo Doppler contrast is that M-mode evaluates contrast at any level along the beam but echo Doppler evaluates only on the range gate. This investigation demonstrated that echo Doppler contrast is more sensitive for detection of microbubbles than M-mode.