A. Taube, E. Siores, R. Avakian, S. Vesnin
Industrial Research Institute Swinburne, Swinburne University of Technology
PO Box 218, Hawthorn, Melbourne, 3122, Victoria , Australia

Abstract: This paper discusses developments in the medical users of microwave energy, particularly in relation to the detection and treatment of cancer. Despite the fact that microwave energy has been in public use for many years, the media usually regard microwaves as a health risk. There are some “superstitious” and dire warnings about mobile phones, and even microwave kitchen ovens. In recent years, however, microwave energy has started to play a more positive role in the health field, serving doctors as diagnostic tools as well as part of medical treatment. Medical uses for microwave energy are numerous, application of microwaves against cancer being just one.

The microwave biomedical applications group in Industrial Research Institute Swinburne University, Melbourne, Australia is involved in three different research projects to develop microwave equipment, which will provide doctors with powerful tools against cancer. They are: apparatus for Microwave Hyperthermia, Microwave Resonance Therapy and Microwave Radiometry.

Microwave Radiometry is a new direction in the field of diagnosis of diseases by measuring small changes of internal tissue temperature. The detection and diagnosis is conducted by measuring of the intensity of natural electromagnetic radiation of patients’ internal tissues at microwave frequencies. The intensity of radiation is proportional to the temperature of the tissues. Cancerous tumours have a significantly different index of refraction and the internal tissue temperature often changes due to inflammation changes in the blood supply or with increased metabolism of cells during oncological transformation of tissues. Thus microwave radiometry measure the integral internal temperature and display it on the monitor.

The main difference between well known infrared thermography and microwave radiometry is that the former allows to read and display the skin temperature, when the latter indicates the integral internal temperature as well.

Microwave Radiometry can be applicable everywhere where the disease causes local Hyperthermia on tissues, for example: Mammology, Urology, Gynaecology and Neuropathology. Microwave Radiometry is a passive and non-invasive measurements and therefore harmless to the patients. It can be used to objectively control the effect of medicines treatments.

The distinctive feature of Microwave Radiometry is an extremely low signal strength entering input of the antenna from the biological tissues. This signal strength is approximately 10ˉ¹³ Watt. While conducting the measurement it is necessary to distinguish temperatures differing on a tenth part of degree, which corresponds to signal strength to be 10ˉ¹³ Watt. Therefore the special circuits are applied for receipt, amplification and treatment of signals. Microwave Radiometry provides measuring intensity of natural electromagnetic radiation of patients’ internal tissues accuracy to 0.06 %.

Computer data processing helps the doctor to determine the diagnosis. The results of the radiometric investigation may be displayed on PC monitor or printed in a form of a table, a thermogram or a temperature field on a projection of the organ investigation.

The application of Microwave Radiometry has, for the most part, been directed at the early detection and diagnosis of breast cancer. Present detection techniques other than radiometry require that the tumour have mass and contrast with respect to the surrounding tissue (i.e., palpation physical examination, mammography, ultrasonography and diaphonography). Results in approximately 85 percent of all determinations of breast disease result in extensive surgical procedures. Early detection could lead to a more conservative treatment and a positive attitude toward detection. The diagnosis of breast cancer at a smaller size or earlier stage will allow a woman more choice in selecting among various treatment options.

Radiometric techniques represent a passive, non-invasive, non-ionizing procedure determining thermal activity rather than mass that, when used in conjunction with one or of the other methods, could provide early detection. The determination of thermal activity is a measurement of tumour activity, or growth rate, providing data beyond the physical parameters (i.e., size and depth determined by mammography). Suspicious results found by screening using microwave radiometry could then refer to mammography.

Each mammary gland is measured on nine areas: 0 - central; 1 - upper quadrant; 3 - inner quadrant; 5 - lower quadrant; 7 - outer quadrant; and on four areas between quadrants (2, 4, 6, 8). The values are analysed by computer, which presents the results of examination in the form of three different diagrams:

Temperature field: The temperature of each MG is shown in colours with isotherms of 0.1 °C. Higher or lower local temperatures (manifestation of disease) are easily detected.
Radiometric techniques represent a passive, non-invasive, non-ionizing procedure determining thermal activity rather than mass that, when used in conjunction with one or of the other methods, could provide early detection. The determination of thermal activity is a measurement of tumour activity, or growth rate, providing date beyond the physical parameters (i.e., size and depth determined by mammography):

•	Medical radiometry has a number of positive characteristics as follows:
•	Early diagnosis of diseases;
•	Possibility of non-invasive detection of disease in internal organs before the appearance of structural changes that can be detected by X rays or ultrasonography;
•	Absolute harmless for the patients of all age and with any diseases as well as for medical staff;
•	Possibility to conduct the investigation repeatedly (control of treatment):
•	Depth of anomaly detection is from 3 to 7 cm;
•	Accuracy of measuring the internal averaged temperature ± 0.2 C
•	Simplicity of the device handing, the procedure may be conducted by the secondary medical staff.
•	Time measuring of one point: 5 – 15 sec.

Advantages of Microwave Radiometry

1. Non-hazardous

Microwave Radiometry is non-hazardous both to the patients and to the personnel taking the thermograms, as during the examination the intensity of natural electromagnetic radiation from the patient's tissue is measured.

2. Non-invasive

Temperature is measured non-invasively.

3. Earlier detection of diseases

Thermal changes precede to the anatomical changes that can be detected by traditional methods such as ultrasound, mammography and palpation. Thus microwave radiometry is a very promising method for the breast cancer detection at an earlier stage.

4. Detection of fast growing tumours

The specific heat generation in the tumour is proportional to the grow rate of the tumour. So fast growing tumours are "hotter" and they are more contrast in thermograms. Thus microwave radiometry is an unique method that allows to detect first of all fast growing tumours. Using microwave radiometry in conjunction with other tradition methods allows to select patients with fast growing tumours.

5. Ability to detect patients with increased proliferative activity of cells

The important feature of the microwave radiometry is that it can distinguish proliferative mastopathy and fibroadenoma from non-proliferative mastopathy and fibroadenoma. So the method allows to select patients who risk to have breast cancer.

6. Ability to monitor treatment

Microwave Radiometry is non-hazardous both to the patients and to the personnel taking the thermograms, so it can be effectively used for the monitoring of the treatment.