The ultrasonic power absorbed by a microbubble in its continuous wave response is estimated through numerically solving a version of the Rayleigh-Plesset equation. At an ultrasonic frequency of 3 MHz, a resonant microbubble, approximately 1.1 μm in radius, showed an absorption cross section of about 0.005 mm 2 in its low power response. This estimation predicts that the tissue ultrasonic absorption will be doubled when such microbubbles are delivered to the tissue at a concentration of about eight bubbles/mm 3 in tissue. An exteriorized murine kidney was exposed to focused ultrasound at 3.2 MHz in degassed saline, and the tissue temperature change was measured. With an intravenous bolus administration of a microbubble agent, the ultrasonically induced temperature elevation was multiplied by up to five times. The enhancement in temperature elevation gradually decreased as the microbubble agent was eliminated from the body. The experimental results agreed with the prediction in the order of magnitude. This effect may have a potential use to enhance the throughput as well as the selectivity of focused ultrasound treatment.
|Number of pages||9|
|Journal||IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control|
|Publication status||Published - 2005 Oct|
ASJC Scopus subject areas
- Acoustics and Ultrasonics
- Electrical and Electronic Engineering