HIFU
Meaning of HIFU: Sound focused the way a magnifying glass focuses sunlight, burning a target inside the body without cutting the skin.
Definition of HIFU
HIFU stands for high intensity focused ultrasound, a treatment that aims sound waves through the skin and concentrates them on a small target inside the body. Where the beams cross, tissue heats within seconds and the cells die, while everything the beams pass through on the way is spared. No incision is made and nothing is left behind.
How does focusing destroy tissue?
A curved transducer sends many ultrasound beams inward so they converge on one small point, much as a magnifying glass gathers sunlight. Any single beam is too weak to harm the tissue it passes through. At the focus the combined energy lifts the temperature high enough to kill cells within seconds, leaving a small cigar shaped zone of destruction. Treating a larger area means repeating that step many times over, moving the focus across a grid, which is why sessions take a while. Rapid pressure swings at the focus can also tear cells apart mechanically, an effect used deliberately in some newer systems.
Where is it used?
| Use | What is targeted |
|---|---|
| Prostate cancer | The tumor or one side of the gland, through a probe in the rectum |
| Uterine fibroids | The fibroid itself, guided by magnetic resonance imaging |
| Essential tremor | A small target deep in the brain, through the intact skull |
| Bone metastases | Nerve endings in the outer layer of bone, to relieve pain |
In prostate cancer it is used mainly as focal treatment, aimed at the part of the gland holding the tumor rather than the whole organ, with the aim of limiting effects on continence and erection.
How is it guided?
The operator has to know where the focus sits and how hot it is becoming. Ultrasound imaging shows the anatomy in real time and is built into the treating probe. Magnetic resonance imaging gives better soft tissue detail and can map temperature as treatment proceeds, so the heated zone is watched while it forms. Guidance is also what limits the method. Sound is reflected by bone and scattered by gas, so a target hidden behind lung or bowel cannot be reached.
What are the trade offs?
Nothing is cut, so bleeding and infection are uncommon and recovery is quick. The cost is uncertainty. No specimen is removed for a pathologist to examine, so treatment cannot be confirmed by inspecting margins, and follow up rests on imaging and blood tests. Long term comparisons against surgery and radiation remain limited for several of its uses, which is why it is often delivered within registries or trials.
Also known as
Used in a sentence
Focal HIFU was offered as an alternative to surgery for disease confined to one side of the gland.
Good to know
Because HIFU destroys tissue in place instead of removing it, no specimen reaches a pathologist, so the completeness of treatment is judged from later imaging and blood tests rather than from examined margins.