IMPROVED MYOCARDIAL CONTRAST WITH 2ND-HARMONIC TRANSIENT ULTRASOUND RESPONSE IMAGING IN HUMANS USING INTRAVENOUS PERFLUOROCARBON-EXPOSED SONICATED DEXTROSE ALBUMIN

Objectives. The objectives of this study were to determine whether a n ew method of ultrasound imaging (transient response imaging) could imp rove the myocardial contrast after intravenous injections of perfluoro carbon exposed sonicated dextrose albumin microbubble contrast medium in humans. Background. We have shown in animals that very low doses of intravenous contrast medium can produce transient but significantly b etter myocardial contrast when diagnostic ultrasound pulses are interr upted (delivered only once per cardiac cycle) instead of conventional 25 to 30-Hz frame rate imaging. Methods. In 14 patients with normal re st wall motion, the peak myocardial contrast produced by transient res ponse imaging was compared with that produced by conventional harmonic ultrasound imaging after injections of low doses (0.0025 to 0.01 ml/k g) of intravenous contrast medium, All studies were performed with sec ond harmonic imaging (2.0 to 2.5 MHz-transmitted frequency). Blood pre ssure, oxygen saturation, respiratory rate and pulse were monitored be fore and after each injection. Results. The intravenous contrast mediu m in the doses given produced no hemodynamic changes and no significan t side effects in any patients. Overall, the mean (+/-SD) anterior and posterior myocardial contrast produced was significantly greater with transient response imaging than with conventional harmonic ultrasound imaging (anterior: 37 +/- 20 U transient response imaging vs. 18 +/- 14 U conventional harmonic imaging; posterior: 17 +/- 14 U transient r esponse imaging vs. 5 +/- 5 U conventional; p < 0.01), With the sample size of 14 patients, the study had 80% power to detect a true differe nce of 18 U for anterior myocardial contrast and 90% power to detect a difference of 12 U for posterior contrast, Visually evident anterior or apical myocardial contrast was observed in 14 of 15 patients with t ransient response imaging but in only 7 patients with conventional har monic imaging. Posterior or basal myocardial contrast was evident in 1 0 patients with tran sient response imaging but in only 1 patient with conventional harmonic imaging. Conclusions. Transient response imagin g produces significantly better myocardial contrast than conventional harmonic imaging in humans and can be produced safely with minute quan tities of intravenous perfluorocarbon.