Researchers at The Institute of Cancer Research (ICR) are investigating a new technique that would destroy cancer cells without the need for surgery.
The technique makes use of High Intensity Focused Ultrasound (HIFU), a medical procedure using a machine that gives off high frequency sound waves that can heat and kill diseased tissue. Just as a magnifying glass can be used to focus the sun’s rays and set fire to a dry leaf, the energy from HIFU can be focused and used to selectively target tumour tissue. The ultrasound transducer, which produces waves 10,000 times stronger than that used for diagnostic ultrasound, is positioned outside the body and the energy then passes through skin and other tissue. The cells at the target site are killed by heating, with temperatures reaching over 60oC in less than a second.
The treatment can therefore destroy tumours deep inside the body but leave surrounding normal tissues unharmed. The therapy is promising because serious complications rarely occur and patients are usually discharged from hospital within 24 hours. However, one issue hindering the widespread use of HIFU therapy is that it can take several hours to complete and is consequently impractical for doctors and patients.
Researchers are therefore looking into the possibility of harnessing another phenomenon in tissue heated by HIFU, called acoustic cavitation or microbubble formation, which could potentially make the treatment more effective.
Presently, however, microbubble formation is generally avoided in the clinic as it can damage tissue in an unpredictable way. Scientists at the ICR and The Royal Marsden NHS Foundation Trust’s Joint Department of Physics have therefore devised a novel monitoring and detection system that can measure this microbubble formation to better understand it.
Study leader Dr Gail ter Haar says: “HIFU is a promising technique that avoids surgery but we wanted to see if we could enhance its effects by understanding what happens when these microbubbles occur. This new study will help us understand how to optimise this novel non-surgical treatment leading to an increase in cancer killing effects and a reduction in treatment times. The bubbles that are formed are microscopic - about the same size as a single cell - so the action of acoustic cavitation is extremely localised. If we can control this phenomenon we have the potential to deliver therapy very precisely – right down to the cancer cells themselves.”
Scientists at the ICR are using a series of sensors that measure specific but interacting parts of the procedure, including the output from the ultrasound transducer, reflections from the acoustic wave created as the ultrasound passes through the tissue, the oscillation of the microbubbles and even the ‘noise’ as the bubbles pop. The study, published recently inUltrasound in Medicine and Biology in collaboration with Professor Tim Leighton at the Institute of Sound and Vibration Research at the University of Southampton and supported by a grant from the Engineering and Physical Sciences Research Council, has provided scientists with a method of measuring in real-time the effects of HIFU induced bubble activity. This new information will be used to improve this novel and promising non-surgical treatment.
Dr ter Haar comments: “HIFU is still in its infancy and our initial aim was to develop this technique for tumours in the abdomen such as kidney and liver cancers, but the procedure is also showing promise for treating prostate, breast and brain tumours. By understanding how microbubbles occur and damage tissues we hope to use this phenomenon to improve this novel non-surgical treatment.”