Download this article in .PDF format
This file type includes high resolution graphics and schematics.

High-frequency engineers have long known about the different properties of RF/microwave signals for detecting objects (such as in radar systems) or for heating (as in microwave ovens). In recent years, however, more and more crossover has occurred between the RF/microwave and medical electronics industries, resulting in a growing use of RF/microwave components and systems for medical applications. These applications range from analysis to treatments, typically using signals in the industrial-scientific-medical (ISM) frequency bands set aside for medical use.

The frequencies available within the RF/microwave range offer a great deal of flexibility for medical applications, with signals at 915 MHz and 2.45 GHz ideal for heating and ablation. Higher-frequency signals are better suited for the treatment of skin and liver cancer, as well as ablation of the heart to treat arrhythmia. Higher frequencies result in shallower penetration of energy, in addition to better matches for surface-based treatments and precise ablation.

For RF/microwave companies seeking to support medical markets, many of these applications require precise generation and amplification of RF/microwave signals. A company with a long track record in the medical area—although perhaps not as well known as many RF/microwave manufacturers—is Cosman Medical, with products designed for neurosurgery and pain management. The firm’s model G4 four-electrode RF generator (Fig. 1), for example, is designed for heating and killing tumor cells and works with RF thermocouple electrodes also manufactured by the company. The signal generator, with a 12-in. touchscreen for ease of control, includes four independent RF sources for treatment of four lesions at one time. It can operate with proprietary algorithms in a continuous-wave (CW) mode for heating of different sites, or else use pulsed RF energy to control the heating rate of different sites in a patient’s body.

1. This sophisticated RF/microwave signal source is designed for heating and killing tumors in a patient’s body. (Photo courtesy of Cosman Medical.)

The company also makes the model RFG-1A universal RF generator, with both thermal (CW) and pulsed RF outputs. It features simplified controls and presets for both neurosurgical and pain management RF procedures, including pallidotomy, thalamotomy, cingulotomy, cordotomy, trigeminal, intradiscal, medial branch, dorsal root ganglion (DRG), and peripheral nerve RF treatments. Pulse widths can be controlled from 0.1 to 3.0 ms for both peripheral and intracranial targets. Also, the firm’s model RFG-1B RF generator has been equipped with simplified controls for podiatry applications; it can be used to treat intractable pain from plantar fasciitis and Morton’s neuroma. 

The RFG-1B radiofrequency generator has simplified controls that are ideally suited for podiatry. It automatically controls the temperature of radiofrequency heat lesions to block pain signals in nerves, such as the inferior calcaneal nerve. Its integrated stimulator produces a 50 Hz signal to localize the sensory fibers innervating a painful area, and a 2 Hz signal to ensure that nearby motor fibers are spared.  The RFG-1B generator is versatile and very easy to use.