Local hyperthermia using radio waves

Local hyperthermia using radio waves involves local heating by means of radio waves emitted at specific frequencies. It is divided into surface, interstitial and deep.

The BSD-500 Hyperthermia System delivers therapeutic heat to certain surface or interstitial malignant tumors (i.e., melanoma, squamous- or basal-cell carcinoma, adenocarcinoma, or sarcoma) by the external or interstitial application of electro-magnetic energy, and monitors the temperature of target and surrounding tissues by means of invasive temperature probes. In response to an operatordesignated control probe, the BSD-500 Hyperthermia System automatically adjusts power to maintain the operator-set therapeutic temperature, which typically is 42-44°C. The BSD- 500 Hyperthermia System also automatically limits power to prevent any detected temperature from exceeding the operator-set maximum.

Tissue absorption of electromagnetic energy causes heating by molecular excitation. Living tissue dissipates accumulated
thermal energy principally through transport by blood perfusing the tissue. Solid malignant tumors of significant size have less blood perfusion than surrounding normal tissue. For a given absorbed thermal dose, the reduced ability to dissipate heat causes tumor tissue to reach higher temperatures than normal tissue. Therefore, absorbed electromagnetic radiation will preferentially heat tumors
present in normal tissue and cause them to reach higher temperatures than the normal surrounding tissue. Tumors heated repeatedly to higher temperatures (hyperthermia) for times approaching an hour sometimes exhibit regression and necrosis.

Local deep hyperthermia is used when the tumor area lies deeper in the body (eg. Pancreatic cancer, cervical cancer, etc.). In this type of hyperthermia antennas are arranged in a ring. This means that the body of the patient is placed in a ring equipped with 8 or 24 antennas. These antennas can be modulated both in frequency waves emitted, the power and phase, which allows to determine exact contour of heated area. To solve the problem of temperature measurement during treatment, the latest version of the BSD-2000 MR is designed for use with magnetic resonance imaging. The aplicator is small enough to fit into a ring of MRI system, so temperature monitoring is thus non-invasive and very precise. The BSD-2000 products operates using a modulated frequency in range of 75 to 140 MHz.