Ultrasonic Therapy Using Cavitation: Induction and Detection
Date Issued
2004
Date
2004
Author(s)
Lai, Kuan-Yu
DOI
zh-TW
Abstract
Cavitation based ultrasound therapy has received considerable research attention. Due to ultrasound’s focusing capability at depth, noninvasive cancer treatment may be possible. Acoustically driven cavitation can cause tissue necrosis as a result of microbubble destruction. These microbubbles are also known as cavitation nuclei. In this study, we concentrate on the following two topics related to acoustic cavitation: induction and detection. For induction, acoustic cavitation is difficult to control and predict without injection of microbubbles, because concentration of the inherent cavitation nuclei is low and the distribution is not uniform. Ultrasound contrast agent can provide a sufficient concentration of cavitation nuclei and the strong backscattering property can also be used for detection. In this study, liposomal microbubbles and Levovist® were used as the cavitation nuclei. The center frequency was 1 MHz and the maximum rarefactional pressure was 1.6 MPa. Two methods for efficient induction of cavitation were proposed: the cascade method and the superposition method. The cascade method cascades a signal at the bubbles resonance frequency with a signal at a lower frequency for destruction. The superimposition method adds a signal at its resonance frequency with a signal at the subharmonic frequency. For detection, the wide-band signal induced by cavitation was measured and used to detect cavitation. The signal was also correlated with the video intensity in B-mode. A 10 MHz transducer was used to avoid the interference from the harmonics.
An experimental system was built. Simulation tools for cavitation were also developed based Rayleigh-Plesset equations and the Runge-Kutta method were adopted to calculate radius of the microbubbles. Both simulations and experimental results show that cavitation can be more efficiently induced using both the proposed methods. The long-term objective of this research is to develop innovative therapeutic technologies for efficient cancer treatment in combination with liposomal capabilities of targeting and drug delivery.
Subjects
超音波
腫瘤治療
微脂體
微氣泡
穴蝕核
穴蝕效應
ultrasound
microbubbles
cavitation nuclei
cancer therapy
cavitation
liposome
SDGs
Type
thesis
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