HIFU – High-Intensity Focused Ultrasound Therapy
For the treatment for cancer and other diseases using high-intensity focused ultrasound (HIFU).
What is HIFU?
HIFU is a cutting-edge treatment that results in necrosis of cancer tissue after applying high-intensity focused ultrasonic (HIFU) energy to a specific area under the impact of thermal energy and cavitation. For a long time, ultrasound has been playing an important role in diagnosis but these days its role has also expanded to include treatment. With the advancement of imaging technology, HIFU is highly effective for the destruction of migrating cancer cells without surgery. Therefore, HIFU can be considered the ultrasonic version of 3-dimensional radiation such as cyber knife or gamma knife.
The HIFU treatment device was first developed for transrectal ultrasound biopsy. Experiments with new treatment have been carried out from outside the body with HIFU. Our clinic applies the ultrasound-guided third-generation FEP-BY02 HIFU Tumor Therapy System. Using the ultrasound imagining part of the HIFU apparatus, it is possible to observe damaged areas in real time. The equipment also facilitates follow-up screening. It is considered a major benefit that damaged areas in abdominal organs which are usually in motion can be screened with ease. The FEP-BY02 HIFU is a fixed-focus device emitting 251 ultrasonic transmission elements at 1.1 MHz lined up on a spherical body of 37 cm in diameter. Many HIFUs are applied only from below whereas the HIFU of our clinic can be applied both from above and below by using two separate devices. For liver cancer and pancreatic cancer, it is actually used 99 % from above which permits high precision. An area targeted only from below takes more time to treat and is also difficult to reach.
Treatment Mechanism
HIFU is a medical procedure which focuses high-intensity ultrasound inside the body which results in necrosis of cancer tissue by way of thermal energy and cavitation.
HIFU destroys cancer cells sized 3 mm x 3 mm x 10 mm with single-dose irradiation on the targeted area generated by thermal energy (Image 1).
The area which is irradiated by a single dose is limited to 3 mm x 3 mm x 10 mm (Image 2).
Repositioning and repeated irradiation is used to cover a larger area to destroy all of the tumor. The cancer cells are destroyed by repeatedly being irradiated (Image 3).
Biological Action
There are two biological actions produced in the patient’s body – thermal effect and non-thermal effect. Thermal Effect When ultrasound is applied to cancer cells at a temperature of over 60 °C (140 °F) for a few seconds, the cancer tissue coagulates and is destroyed. Non-Thermal Effect Ultrasound also generates a non-thermal effect which is called cavitation. Cavitation is the phenomenon by which air bubbles are generated when ultrasound is spotted. The shock wave generated by air bubbles or a micro jet stream is also considered to kill cancer cells.
Safety
Radiation Exposure The energy level of HIFU is about 1000 times that of an ultrasound device for imaging yet when compared to a proton beam, X-ray or a CT, it is extremely low and thus is fairly safe. And there is no worry about radiation exposure. Skin Burn The targeted area by a single irradiation is limited to 3 mm x 3 mm x 10 mm. When there are cancer cells in an internal organ near the skin, it will cause skin burn due to the higher skin temperature. The FEP?BY02 HIFU has a transducer with a large diameter whereby safety is enhanced by increasing the angle of incidence by 80 degrees.
Treatment
In general, it takes about 1 hour and 30 minutes for a single treatment which is performed 1 or 2 times. Anaesthetics are not usually administered. This treatment uses ultrasound energy so there is no limitation as with radiation. HIFU treatment can be used repeatedly because there is no risk of radiation exposure. Depending on the size and location of the cancer, various treatments will be looked at. Generally, hospitalization is not required. Treatment contents, dose and the need for hospitalization, however, vary depending on the patient’s medical condition.
HIFU Treatment Indications
- Uterine fibroids (Myoma)
- Liver cancer
- Metastatic liver tumor
- Breast cancer
- Kidney cancer
- Pancreatic cancer
- Prostate cancer
- Soft-tissue sarcoma
- Bone tumors
- Other indications
Significance of HIFU Treatment for Hepatocellular Carcinoma (HCC)
The use of Gd-EOB-DAPT MRI makes it possible to detect hepatocellular carcinoma (HCC), the most common type of liver cancer and difficult to detect with dynamic CT at an early stage. Thus, prompt treatment measures are required. In the circumstances, HIFU has made it possible to treat a patient with liver cancer sized 1-2 cm for approximately one hour without hospitalization. HIFU is considered one of the leading treatments for HCC in Japan.
