Also known as: Ablatherm device, Sonablate 500 device (SB500)
Summary
High Intensity Focused Ultrasound, HIFU, is a non-invasive therapy that uses focused ultrasound to generate precise areas of intense heat to destroy tumours, while leaving surrounding tissue unaffected. This therapy has been studied for around 50 years, with recent developments allowing use on tumours of the liver, kidney, bone, pancreatic, prostate and other areas. It has minimal or no side effects and can be safely repeated if necessary.
Description
High Intensity Focused Ultrasound or HIFU, uses high energy, high frequency, focused sound waves to destroy precise volumes of tissue within a tumour without damaging surrounding structures. This pulse of high energy ultrasound can be focused onto a single location the size of a grain of rice. When directed at a delivery point, the temperature increases, causing the fats (lipids) in the cell membrane to melt and the proteins to denature, destroying a small volume of tissue. With the treatment of prostate cancer, targeting can be planned in order to preserve the vital structures around the glands that are involved in preservation of continence and erectile function. HIFU treatment can stimulate the immune system which can, on its own, have an effect on tumours that have not been directly targeted. Small tumours can be destroyed in one session, but often large tumours require more sessions. In some cases there are advantages in combining HIFU with other medical treatments. Sessions are followed up with MRI scans to confirm tumour destruction. With HIFU, there has been no evidence of side effects. Occasionally the skin is affected with a mild sunburn effect which clears up after a few days. The use of anaesthetic eliminates any discomfort allowing the patient to keep still during treatment.
History
Ultrasound transducers were first developed by P. Langevin during the 20th century. He used the piezoelectric properties of quartz crystal to construct the first submarine sonar. In the 1940s, the first investigations of HIFU for non-invasive ablation were reported by Lynn et al. During the 1940s and 1960s, important work was performed by William and Francis Fry at Illinois University. This culminated in clinical treatments of neurological disorders such as Parkinson’s disease. Using a set of ultrasound transducers, which were focused on an area to be treated, tiny biological lesions located deep within the cerebral cortex could be reached. Until recently, there have only been a few clinical trials of HIFU for ablation (although significant work in hyperthermia has been performed using ultrasonic heating). This was perhaps due to the complexity of the treatment and the difficulty of targeting the ultrasonic beam non-invasively. Due to recent advances in ultrasound technology and medical imaging, there has been an increase in interest in HIFU ablation of tumours.
