John Hunt

Research Synopsis

Therapeutic Research Linked to Hyperthermia and Chemical Changes Using Intense Ultrasound Beams

Present Research Program Include the Therapeutic Research Linked to Temperature Cooling by Hyperthermia Using Intense Ultrasound Beams, and High Frequency Changes in Diagnostic Ultrasound Used During Therapeutic Treatments.

Dr. John Hunt's programs span radiation dosimetry and chemistry, diagnostic ultrasound, and different basic studies of elevated temperature called hyperthermia that has the goal of controlling malignant tumours. More recent experments are linked to hyperthermia treatments, targeted to temperatures above 42 C for 60 minutes, are now recognized as an effective heating technique for improving local cancer control. Using microwave treatments in recurrent chest wall malignant lesions have shown the effectivity of the treatments (1). A serious limitation is the heterogenous temperature distribution during the treatments related to blood flow cooling. One way of improving temperature distribution during the treatment is to heat the tumour so rapidly that the effects of the blood flow cooling are greatly reduced. Focussed high-powered ultrasound is ideal for generating short treatments and high temperatures that produce lesions which kill the malignant cells with reducing the cooling by major blood vessels (2). In addition, unique acoustic lenses have been developed that produce, not a single focus, but instead up to 18 foci lesions so that a more homogeneous and larger treatment field can be produced (3). Other transducer geometries are being considering to improve the treatment protocols. Our present program seeks to understand the special problems of cooling by blood flow passing in tissues by using pulses of heat that bette understanding the complex relationships between the thermal flow in blood vessels.We have also explored the use of intense ultrasound beams and chemical agents to produce enhanced therapeutic

Recently, we are observing the changes of cells and tissues during therapeutic treatments by using high frequency diagnostic ultrasound techniques. The aim is to rapidly subtle detecting changes during the treaments of patients. It was surprising that cells during chemotherpeutic protocols show very large increases of the image intentities during the treaments. Simulations suggest that the changes may be linked fairly regular cellular separations in the tissues, with small changes of the chromosomes positions in the cells (6).

Recent Publications

• Sherar, M., Liu, F-F., Pintile M., Levin W., Hunt J., Hill R., Hand J., Vernon C., van Rhoon G., van der Ze J., Gonzalez D.G., van Dijk J., Whaley J., and Machin D., 1997. Relationship Between Thermal Dose and Outcome in Thermoradiotherapy Treatments of Superficial Recurrences of Breast Cancer: Data from a Phase III Trial. Int. J. Radiation Oncology Biol. Phys. , 39 : (2)371-380.
• Kolios, M.C. Sherar, M.D. and Hunt, J.W. 1996. Blood Flow Cooling and Ultrasonic Lesion Formation. Medical Physics, 23 : 1287-1298,
• Lalonde, R., Worthington, A., Hunt, J.W. 1993. Field Conjugate Lenses for Ultrasound Hyperthermia l.E.E.E Transactions on Ultrasonics, Ferroelectrics and Frequency Control, 4 : 592-602.
• Kolios, M.C., Worthington, A.E., Sherar, W.D., and Hunt, J.W. 1998. Experimental Evaluation of Two Simple Thermal Models Using Transient Temperature Analysis. In press: Physics in Medicine and Biology.
• Czarnota, G.J., Kolios, M.C., Vaziri, H., Benchimol, S., Otenssmeyer, F.P., Sherar, M.D., and Hunt, J.W. 1997. Ultrasonic Biomicroscopy of Viable, Dead, and Apoptic Cells. Ultrasound in Med. and Biol. , 23 : 961-965.
• Hunt, J.W., Worthington, A.E., Kerr, A.T. 1995. The Subtleties of Ultrasound Images of an Ensemble of Cells: Simulation from Regular and More Random Distributions of Scatterers. Ultrasound in Medicine & Biology , 21 : 329-341.