DocumentCode :
813844
Title :
Enhanced heat deposition using ultrasound contrast agent - modeling and experimental observations
Author :
Razansky, Daniel ; Einziger, Pinchas D. ; Adam, Dan R.
Author_Institution :
Dept. of Biomedical Eng., Technion-Israel Inst. of Technol., Haifa, Israel
Volume :
53
Issue :
1
fYear :
2006
Firstpage :
137
Lastpage :
147
Abstract :
Ultrasound contrast agents (UCA), created originally for visualization and diagnostic purposes, recently have been suggested as efficient enhancers of ultrasonic power deposition in tissue. The ultrasonic energy absorption by the contrast agents, considered as problematic in diagnostic imaging, might have beneficial impact in therapeutic applications such as targeted hyperthermia-based or ablation treatments. Introduction of gas microbubbles into the tissue to be treated can improve the effectiveness of current treatments by limiting the temperature rise to the treated site and minimising the damage to the surrounding healthy tissues. To this end, proper assessment of the governing parameters of energy absorption by ultrasonically induced stabilized bubbles is important for both diagnostic and therapeutic ultrasound applications. The current study was designed to predict theoretically and measure experimentally the dissipation and heating effects of encapsulated UCA in a well-controlled and calibrated environment. The ultrasonic effects of the microbubble concentration, transmitted intensity, and frequency on power dissipation and stability of the UCA have been studied. The maximal temperature elevation obtained during 300 s experiments was 21°C, in a 10 ml volume target containing UCA, insonified by unfocused 3.2 MHz continuous wave (CW) at spatial average intensity of 1.1 W/cm2 (182 kPa). The results also suggest that higher frequencies are more efficiently absorbed by commonly used UCA. In particular, for spatial average intensity of 1.1 W/cm2 and concentration of 5·106 microspheres/cm3, no significant reduction of UCA absorption was noticed during the first 150 s for insonation at 3.2 MHz and the first 100 s for insonation at 1 MHz. In addition, when lower average intensity of 0.5 W/cm2 (160 kPa) at 3.2 MHz was used, the UCA absorptivity sustained for almost 200 s. Thus, when properly activated, UCA may be suitable for localized hyperthermic therapies.
Keywords :
biological tissues; biomedical ultrasonics; bubbles; hyperthermia; 1 MHz; 160 kPa; 182 kPa; 3.2 MHz; 300 s; ablation treatments; diagnostic imaging; enhanced heat deposition; gas microbubbles; heating effects; insonation; power dissipation; targeted hyperthermia; therapeutic applications; tissue; ultrasonic energy absorption; ultrasonic power deposition; ultrasound contrast agent; Absorption; Current measurement; Frequency; Heating; Hyperthermia; Power dissipation; Temperature; Ultrasonic imaging; Ultrasonic variables measurement; Visualization; Albumins; Computer Simulation; Contrast Media; Fluorocarbons; Heat; Models, Chemical; Ultrasonic Therapy; Ultrasonography;
fLanguage :
English
Journal_Title :
Ultrasonics, Ferroelectrics, and Frequency Control, IEEE Transactions on
Publisher :
ieee
ISSN :
0885-3010
Type :
jour
DOI :
10.1109/TUFFC.2006.1588399
Filename :
1588399
Link To Document :
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