The source of ultrasound contrast effect

Abstract

Evidence that microbubbles are the main sources of ultrasound contrast in injected solutions has been largely indirect. To investigate this directly, we examined freshly agitated indocyanine green, freshly agitated water, commercially prepared precision microbubbles (diameter 75 +/- 25 mu) in gelatin, carbonated water, "degassed" indocyanine green solution, and "degassed" water in one or more of four different assay systems. Only fluids with microbubbles produced ultrasound contrast. Injected contrast material rose in a water bath at a rate that identified it as being caused by microbubbles. Indocyanine green and gelatin surface tensions were measured and found to be low (43 dynes/cm2), thus explaining their tendency to stabilize the microbubbles that cause ultrasound contrast effect when injected and to hold foam after agitation. The force of hand injections (force similar to that used clinically through catheters and 19-gauge or 23-gauge needles) was below the force needed to cause cavitation or ultrasound contrast effect. Microbubble content could be quantified by the decrease in amplitude of the echo from a structure distant to the microbubbles. We conclude that that the ultrasound contrast effect seen in peripherally injected fluids is caused by microbubbles present in the injectant. The contrast is not due to cavitation at needle tips, and it can be quantified over a limited range. Improved design for a peripheral contrast agent is suggest.

Quantitative Evaluation of Contrast Enhanced Transcranial Doppler Signal using Galactose Based Echo-Contrast Agent in Dogs

“…Dissimilar acoustic impedance values lead to a high degree of reflection [22]. Different substances such as hand-shaken solution, hydrogen peroxide, angiographic contrast media, albumin, and different types of saccharides are used as echo-contrast agent.…”

Visualization of subendocardial myocardial ischemia with myocardial contrast echocardiography in humans.

“…First, enhancement of gray level is affected by several factors, such as the gain setting, angle of incidence, axial and lateral resolution, the ultrasound attenuation, regional gray level variation, and the injection volume of contrast agent. [16][17][18]20,21,27,33 Thus, we did not refer to the values of gray level in the endocardial and epicardial halves, respectively, but measured the endo:epi gray level ratio because effects of aforementioned factors are thought to be reduced by taking the ratio.…”

Detection of Intracardiac and Intrapulmonary Shunts at Rest and During Exercise Using Saline Contrast Echocardiography

“…Echocardiography used as a technique for the detection of right-to-left shunts assumes that intravenously-infused saline contrast bubbles are filtered out by the pulmonary capillaries or collapse before reaching the left side of the heart (Yang, 1971;Yang et al, 1971a, b et al, 1980a;Meltzer et al, 1980b;Meltzer et al, 1981;Bommer et al, 1984;Woods & Patel, 2006). Thus, large diameter bubbles do not reach the left side of the heart unless they travel through large diameter pathways such as pulmonary arteriovenous malformations (PAVMs) or a PFO.…”