HIFU

High-intensity focused ultrasound
Intervention
Synonyms	Magnetic resonance guided focused ultrasound (MRgFUS)
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High intensity focused ultrasound (HIFU) is an early stage medical technology that is in various stages of development worldwide to treat a range of disorders.

The mechanism is similar to using a magnifying glass to focus sunlight. Focused ultrasound uses an acoustic lens to concentrate multiple intersecting beams of ultrasound on a target. Each individual beam passes through tissue with little effect but at the focal point where the beams converge, the energy can have useful thermal or mechanical effects. HIFU is typically performed with real-time imaging via ultrasound or MRI to enable treatment targeting and monitoring (including thermal tracking with MRI).

Therapeutic applications use ultrasound to deliver heat or agitation into the body; much higher energies are used than in diagnostic ultrasound. In many cases the frequencies used are different. Specific therapeutic applications of ultrasound include this non-exhaustive list:

HIFU is being studied in men with prostate cancer.

In 2015 the FDA authorized two HIFU devices for the ablation of prostate tissue.

The treatment is administered through a transrectal probe and uses heat generated by focusing ultrasound waves to kill cancerous cells in the prostate. These treatments are performed under ultrasound imaging guidance, which allows for treatment planning and some minimal indication of the energy deposition. This is an outpatient procedure that usually lasts 1–3 hours.

There is a system in clinical trials using a transurethral probe to ablate the prostate tissue from the inside-out.

Treatment for symptomatic uterine fibroids became the first approved application of HIFU by the US Food and Drug Administration (FDA) in October 2004. Studies have shown that HIFU is safe and effective, and that patients have sustained symptomatic relief is sustained for at least two years without the risk of complications involved in surgery or other more invasive approaches. Up to 16-20% of patients will require additional treatment.

An ultrasound system is approved in Israel, Europe, Korea and Russia to treat essential tremor,neuropathic pain, and Parkinsonian tremor. This approach enables treatment of the brain without incisions and without radiation. In 2016, the US Food and Drug Administration (FDA) approved Insightec’s Exablate Neuro system to treat essential tremor. The system is also being researched for treating depression and obsessive-compulsive disorder.

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