Therapeutic Applications of E.M. Waves and Ultrasound

Our laboratory is interested in hyperthermia for the treatment of cancer. This involves the use of microwaves, ultrasound and lasers to raise the temperature of tumour tissue in a controlled manner resulting in tumour destruction whilst sparing healthy normal tissues. To develop these new treatments a wide variety of physics and biophysics studies are in progress. First, the interaction of electromagnetic waves, ultrasound and light with tissue, which results in heating, is being imulated using numerical methods.

Also the design of applicators such as microwave waveguides and antennas that will allow accurate and specific heating of tumours is an important part of our work. This involves computer modelling, design and the manufacture of applicators. Others in the laboratory are working on the mathematics and biophysics of heat dissipation in tissue. Of particular importance, in this regard, is the effect of blood flow whose complex effect on heating patterns must be well-understood to design effective treatments. Many of the fundamental developments are taken into the clinic for experimental treatments in patients. An example is a clinical trial recently completed at the OCI evaluating hyperthermia plus radiation versus radiation alone in the treatment of breast cancer recurrences which demonstrated a significant positive effect with the addition of hyperthermia. A second example in the development stage is the use of Magnetic Resonance Imaging (MRI) to monitor high temperature minimally invasive thermal surgery in the brain. Here, surgeons will use fine microwave antennas or laser probes to destroy previously unresectable tumours in the brain using MRI guidance which allows one to measure temperatures non-invasively during treatment.

In summary, projects are available from fundamental mathematics and physics of heat deposition and flow cooling in tissues, through applicator development to clinical projects involving experimental treatments in animals and patients.

For more information, please visit our lab homepage at http://www.uhnres.utoronto.ca/sherar

Graduate Students:

Selected References:

• Kolios, M.C., Sherar, M.D., and Hunt, J.W. 1995. Large blood vessel cooling in heated tissues: a numerical study. Phys. Med. Biol. 40:477-494.

• Sherar, M.D., Clark, H., Cooper, B., Kumaradas, J. and Liu, F.-.F. 1995. A variable microwave array attenuator for use with single-element waveguide applicators. Int. J. Hyperthermia. (5) 10: 723-31.

• Levin, W., Sherar, M.D., Cooper, B., Hill, R.P., Hunt, J.W. and Liu, F-.F. 1994. Effect of vascular occlusion on tumour temperatures during superficial hyperthermia. Int. J. Hyperthermia, (4) 10: 495-505.