|University of Illinois at Urbana-Champaign | Department of Electrical and Computer Engineering | Department of Bioengineering
Department of Statistics | Coordinated Science Laboratory | Beckman Institute | Food Science and Human Nutrition | Division of Nutritional Sciences | College of Engineering
|Sunday, February 25th, 2018|
Quantification of Ultrasound Contrast Agents
By Darryl Ma, Graduate Student
It is well known that Ultrasound Contrast Agents (UCA), because of their scattering properties, enhance the diagnostic capabilities of ultrasonic imaging by increasing the image contrast between a selected location and the background. However the relationship between intensity and quantity of UCAs remains poorly defined. The goal of this project is, therefore, to quantify UCAs in vivo and in vitro by analyzing its ultrasound backscatter response.
In the equation, C is equal to (π4/36c4) where c is the speed of sound in the medium, f is frequency, D is the diameter of the scatterer, represents the scatterers per unit volume, represents the mean-squared variation in acoustic impedance between scatterer and surrounding medium, and is the form factor, which is a function of frequency and scatterer diameter.
Equation (1) indicates that the backscatter response should be linearly proportional to the concentration of UCAs. That is, if the concentration of UCAs is increased by a factor of four, the power of the backscattered signal should also be increased by a factor of four. Early experiments have confirmed this supposition (refer to Table 1). Additionally, experiments have suggested that the backscatter response is heavily dependent on the size of the scatterers. In fact, equation (1) suggests that the power of the backscatter response, if the scatterers are assumed to be spherical, will be proportional to the volume of the scatterers squared. Early experiments have also confirmed that the power of the backscatter response is heavily dependent on the size of microbubbles.
Table 4 - Comparing mean diameter of UCAs obtained from two Matlab programs for two different samples
At the moment, all experiments have only been conducted within a 250mL beaker. Future work will involve quantifying UCAs in vitro within a perfusion phantom and in vivo within a rabbit ear.
|Bioacoustics Research Lab.|