2008 Volume 20 Issue 2-3 Pages 82-88
The use of ultrasound in clinical practice is no longer limited to diagnostic imaging. Ultrasound technology now allows for the use of focused ultrasound energy for therapeutic purposes by delivering high-intensity focused ultrasound (HIFU) for applications such as tissue ablation, throrabolysis, enhanced drug delivery and hemostasis. HIFU is being promoted as a noninvasive method to treat certain primary solid tumors, metastatic disease. enhance drug delivery through the blood-brain barrier. and to promote thrombolysis in stroke victims. The field of medicine is evolving towards increasing use of noninvasive and minimally invasive therapies such as HIFU. The major effect of very high acoustic intensities in tissue is heat generation due to absorption of a portion of the acoustic energy. Focusing results in high intensities at a specific location and over only a small volume. This focusing minimizes the potential for thermal damage to tissue located between the transducer and the focal point as the intensities are much lower outside the focal region. There are also mechanical phenomena in addition to thermal effects that are associated with high acoustic intensities that are not present at lower intensities. Mechanical phenomena include cavitation, microstreaming, and radiation forces. This article provides an overview of HIFU including its mechanisms of action. current clinical applications, and future requirements to expand the clinical applications of this technique.
