Adaptive high-frequency generators used in biomedical engineering

Abstract

High-frequency (HF) generators of electromagnetic field are used in medicine and biology for treatment and prophylaxis of various diseases by warming tissues. They are also used as energy sources in sterilizers, ozonizers, and medical gas-discharge lasers. Recently developed planar and microstrip high technologies and modern semiconductor elements allow the performance (including cost, weight, dimensions, and ergonomic characteristics) of currently used high-frequency electromagnetic generators to be considerably improved.Biomedical HF generators of the new generation should provide: 1) safety of patients and medical personnel; 2) generation of HF signals providing necessary effect on biological objects;3) matching the output resistance of the generator to the impedance of the object subjected to HF treatment.Consider the possibility of implementation of HF generators meeting these requirements. High-Frequency Generator Operation SafetyRequirements for HF generator operation safety can be divided into two groups: 1) requirements for electrical safety; 2) requirements for the safety of HF irradiation of personnel. Use of planar technology and transistor microelements allows both the electrical and irradiation safety of HF generators to be increased.Transistorized equipment does not require a highvoltage power supply. Thus, use of a low-voltage power supply provides the electrical safety of transistorized equipment. Besides, this allows the transistorized equipment to be energized from electric generators and accumulator batteries used in cars, planes, or ships; thus, mobile medical equipment based on transistors can be developed.The irradiation safety of transistorized equipment is also higher than in previous models of HF generators.Shielding metal cases and metal braiding of wires remain the main means of irradiation protection of personnel. However, the possibility of spurious HF irradiation is significantly decreased by the use of planar technologies. Point-to-point wiring causes considerable irradiation, because HF currents induced in the structural components produce secondary electromagnetic fields. Thus, radiation capacity of HF devices based on point-to-point wiring is several orders of magnitude higher than that of HF devices based on planar technologies.Because HF-radiation in planar-technology devices is mainly concentrated inside the circuit, electromagnetic safety of these devices is sufficiently rather high. The intrinsic antenna effect of these devices accounts for 10-9-10 6 their nominal power. Therefore, planartechnology HF devices provide significantly higher personnel safety.