High-intensity focused ultrasound (HIFU or HIFUS) is a cancer treatment which uses sound waves at high frequency. A focused beam of sound waves is directed at cancer cells in order to heat them and destroy them. In the short term, high-intensity focused ultrasound seems to have fewer side effects than other cancer treatments. As it is a relatively recent and experimental method, the long-term effects are unknown. Prostate, kidney and bladder cancer may all be treated using HIFU, and the technique has also been used to treat non-cancerous tumors such as uterine fibroids.
HIFU is most effective for single tumors. In cases where cancers have spread through the body, other treatment methods are usually used. A tumor's location could also make the technique unsuitable. As well as kidney, bladder and prostate cancers, high-intensity focused ultrasound may be used to treat tumors of the pancreas and liver. It is also used, in combination with magnetic resonance imaging (MRI) to remove fibroids from the womb.
In the treatment of fibroids, magnetic resonance-guided focused ultrasound (MR-guided FUS) involves using an MRI scanner to view the tumor location precisely. The patient is awake and lies face down inside the scanner, with a button to alert staff in case any discomfort is felt during the process. MRI scans enable a three-dimensional view of the inside of the body in real time. This allows a beam of sound waves to be focused on a small area of the fibroid.
Pulses of sound energy heat up the tissue until the cells are killed, and this takes place without harming any of the surrounding tissues. Dead tissue, which has been heated and destroyed by the high intensity sound waves, is reabsorbed by the body. Further sound wave pulses are used to destroy all of the tumor, with the MRI images showing which areas have been treated and which have not.
Although MRI-guided FUS is expensive due to the cost of the technology involved, the advantages include reduced side effects and shorter hospital stays. There is also the benefit, when compared with surgery, that a general anesthetic is not required for this type of procedure. While it is known to be effective in treating benign and cancerous tumors, ongoing trials may prove the usefulness of high-intensity focused ultrasound in treating other conditions, such as pain from bone metastases. Bone metastases are cancerous growths which have spread to bone from the original tumor.
