page_title: High-intensity focused ultrasound
section_title: Mechanism
hierarchical_section_title: High-intensity focused ultrasound / Mechanism
caption_attribution_description: English: HIFU (high intensity focused ultrasound) transducers are used for heating tissue noninvasively with ultrasound. This is useful for treating a number of diseases including cancer. The transducers (or probes) differ from those that most people are familiar with for imaging, so this comparison picture has been made. On the left are two HIFU transducers with focused lenses to achieve high intensity inside the body. On the right is an imaging probe for using ultrasound to image the heart.
context_page_description: High-intensity focused ultrasound is a non-invasive therapeutic technique that uses non-ionizing ultrasonic waves to heat tissue. HIFU can be used to increase the flow of blood or lymph, or to destroy tissue, such as tumors, through a number of mechanisms. The technology can be used to treat a range of disorders and as of 2015 is at various stages of development and commercialization.
  The technology is similar to ultrasonic imaging, although lower frequencies and continuous, rather than pulsed waves are used to achieve the necessary thermal doses. However, pulsed waves may also be used if mechanical rather than thermal damage is desired. Acoustic lenses are often used to achieve the necessary intensity at the target tissue without damaging the surrounding tissue. An analogy is using a magnifying glass to focus sunlight; only the focal point of the magnifying glass has high intensity. Although lenses have traditionally been used, phased arrays are increasingly common as they allow the focal position to be easily changed.
  HIFU may be combined with other imaging techniques such as medical ultrasound or MRI to enable guidance of the treatment and monitoring.
context_section_description: HIFU beams are precisely focused on a small region of diseased tissue to locally deposit high levels of energy.
  The focusing effect of the transducer allows high sound pressures to be delivered to a focal point without causing unwanted damage to other tissue. This increase in pressure can cause a number of effects including heating and cavitation.
  Ultrasound sources may be used to generate regional heating and mechanical changes in biological tissue, e.g. in  and cancer treatment.
  Focused ultrasound may be used to generate highly localized heating to treat cysts and tumors (benign or malignant). This is known as Magnetic Resonance guided Focused Ultrasound (MRgFUS) or High Intensity Focused Ultrasound (HIFU). These procedures generally use lower frequencies than medical diagnostic ultrasound (from 0.250 to 2 MHz), but significantly higher energies. HIFU treatment is often guided by MRI.
  Focused ultrasound may be used to break up kidney stones by lithotripsy.
  Ultrasound may be used for cataract treatment by phacoemulsification.
  In 2015 the FDA authorized two HIFU devices for the ablation of prostate tissue.
caption: The transducers differ from ultrasonic imaging probes which many people are familiar with. In this picture, two examples of HIFU transducers are shown on the left. They both have acoustic bowl-shaped lenses focus the sound inside the body. For comparison, on the right is an ultrasound imaging probe that might be used for cardiac imaging.
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