Medical applications of radio frequency (RF) energy, in the form of

electromagnetic wave In physics, electromagnetic radiation (EMR) consists of waves of the electromagnetic (EM) field, which propagate through space and carry momentum and electromagnetic radiant energy. It includes radio waves, microwaves, infrared, (visib ...

s (

radio wave Radio waves are a type of electromagnetic radiation with the longest wavelengths in the electromagnetic spectrum, typically with frequencies of 300 gigahertz (GHz) and below. At 300 GHz, the corresponding wavelength is 1 mm (short ...

s) or electrical currents, have existed for over 125 years, and now include

diathermy Diathermy is electrically induced heat or the use of high-frequency electromagnetic currents as a form of physical therapy and in surgical procedures. The earliest observations on the reactions of high-frequency electromagnetic currents upon the ...

hyperthermy Hyperthermia, also known simply as overheating, is a condition in which an individual's body temperature is elevated beyond normal due to failed thermoregulation. The person's body produces or absorbs more heat than it dissipates. When extreme ...

treatment of cancer,

electrosurgery Electrosurgery is the application of a high-frequency (radio frequency) alternating polarity, electrical current to biological tissue as a means to cut, coagulate, desiccate, or fulgurate tissue.Hainer BL, "Fundamentals of electrosurgery", ''Jou ...

scalpels used to cut and cauterize in operations, and

radiofrequency ablation Radiofrequency ablation (RFA), also called fulguration, is a medical procedure in which part of the electrical conduction system of the heart, tumor or other dysfunctional tissue is ablated using the heat generated from medium frequency alternat ...

Magnetic resonance imaging Magnetic resonance imaging (MRI) is a medical imaging technique used in radiology to form pictures of the anatomy and the physiological processes of the body. MRI scanners use strong magnetic fields, magnetic field gradients, and radio wave ...

(MRI) uses radio frequency waves to generate images of the human body. Radio frequencies at non-ablation energy levels are commonly used as a part of aesthetic treatments that can tighten skin, reduce fat by

lipolysis Lipolysis is the metabolic pathway through which lipid triglycerides are hydrolyzed into a glycerol and free fatty acids. It is used to mobilize stored energy during fasting or exercise, and usually occurs in fat adipocytes. The most important ...

and also

apoptosis Apoptosis (from grc, ἀπόπτωσις, apóptōsis, 'falling off') is a form of programmed cell death that occurs in multicellular organisms. Biochemical events lead to characteristic cell changes (morphology) and death. These changes incl ...

, or promote healing. RF diathermy is a medical treatment that uses RF induced heat as a form of

physical therapy Physical therapy (PT), also known as physiotherapy, is one of the allied health professions. It is provided by physical therapists who promote, maintain, or restore health through physical examination, diagnosis, management, prognosis, patient ...

and in surgical procedures. It is commonly used for muscle relaxation. It is also a method of heating tissue electromagnetically for therapeutic purposes in medicine. Diathermy is used in physical therapy to deliver moderate heat directly to pathologic lesions in the deeper tissues of the body. Surgically, the extreme heat that can be produced by diathermy may be used to destroy

neoplasms A neoplasm () is a type of abnormal and excessive growth of tissue. The process that occurs to form or produce a neoplasm is called neoplasia. The growth of a neoplasm is uncoordinated with that of the normal surrounding tissue, and persists ...

warts Warts are typically small, rough, hard growths that are similar in color to the rest of the skin. They typically do not result in other symptoms, except when on the bottom of the feet, where they may be painful. While they usually occur on the ...

, and infected tissues, and to

cauterize Cauterization (or cauterisation, or cautery) is a medical practice or technique of burning a part of a body to remove or close off a part of it. It destroys some tissue in an attempt to mitigate bleeding and damage, remove an undesired growth, o ...

blood vessels The blood vessels are the components of the circulatory system that transport blood throughout the human body. These vessels transport blood cells, nutrients, and oxygen to the tissues of the body. They also take waste and carbon dioxide away f ...

to prevent excessive bleeding. The technique is particularly valuable in

neurosurgery Neurosurgery or neurological surgery, known in common parlance as brain surgery, is the medical specialty concerned with the surgical treatment of disorders which affect any portion of the nervous system including the brain, spinal cord and peri ...

and surgery of the eye. Diathermy equipment typically operates in the short-wave radio frequency (range 1–100 MHz) or microwave energy (range 434–915 MHz).

Pulsed electromagnetic field therapy Pulsed electromagnetic field therapy (PEMFT, or PEMF therapy), also known as low field magnetic stimulation (LFMS) uses electromagnetic fields in an attempt to heal non-union fractures and depression. By 2007 the FDA had cleared several such sti ...

(PEMF) is a medical treatment that purportedly helps to heal bone tissue reported in a recent NASA study. This method usually employs electromagnetic radiation of different frequencies – ranging from static magnetic fields, through extremely low frequencies (ELF) to higher radio frequencies (RF) administered in pulses.

History

The idea that high-frequency electromagnetic currents could have therapeutic effects was explored independently around the same time (1890–91) by French physician and biophysicist

Jacques Arsene d'Arsonval Ancient and noble French family names, Jacques, Jacq, or James are believed to originate from the Middle Ages in the historic northwest Brittany region in France, and have since spread around the world over the centuries. To date, there are over ...

and Serbian American engineer

Nikola Tesla Nikola Tesla ( ; ,"Tesla"
''

J. W. Hand,"Biophysics and Technology of Electromagnetic Hyperthermia" in d'Arsonval had been studying medical applications for electricity in the 1880s and performed the first systematic studies in 1890 of the effect of alternating current on the body, and discovered that frequencies above 10 kHz did not cause the physiological reaction of

electric shock Electrical injury is a physiological reaction caused by electric current passing through the body. The injury depends on the density of the current, tissue resistance and duration of contact. Very small currents may be imperceptible or produce ...

, but warming., translated by J. H. Kellogg He also developed the three methods that have been used to apply high-frequency current to the body: contact electrodes, capacitive plates, and inductive coils.

Nikola Tesla Nikola Tesla ( ; ,"Tesla"
''

By 1900 application of high-frequency current to the body was used experimentally to treat a wide variety of medical conditions in the quack medical field of ''

electrotherapy Electrotherapy is the use of electrical energy as a medical treatment. In medicine, the term ''electrotherapy'' can apply to a variety of treatments, including the use of electrical devices such as deep brain stimulators for neurological dise ...

''. In 1899 Austrian chemist von Zaynek determined the rate of heat production in tissue as a function of frequency and current density, and first proposed using high-frequency currents for deep heating therapy. In 1908 German physician Karl Franz Nagelschmidt coined the term ''diathermy'', and performed the first extensive experiments on patients. Until the 1920s noisy spark-discharge

Tesla coil A Tesla coil is an electrical resonant transformer circuit designed by inventor Nikola Tesla in 1891. It is used to produce high-voltage, low-current, high-frequency alternating-current electricity. Tesla experimented with a number of different ...

and

Oudin coil An Oudin coil, also called an Oudin oscillator or Oudin resonator, is a resonant transformer circuit that generates very high tension, high frequency alternating current (AC) electricity at low current levels, used in the obsolete forms of elec ...

machines were used. These were limited to frequencies of 0.1 – 2 MHz, called "longwave" diathermy. The current was applied directly to the body with contact electrodes, which could cause skin burns. In the 1920s the development of

vacuum tube A vacuum tube, electron tube, valve (British usage), or tube (North America), is a device that controls electric current flow in a high vacuum between electrodes to which an electric voltage, potential difference has been applied. The type kn ...

machines allowed frequencies to be increased to 10 – 300 MHz, called "shortwave" diathermy. The energy was applied to the body with inductive coils of wire or capacitive plates insulated from the body, which reduced the risk of burns. By the 1940s

microwave Microwave is a form of electromagnetic radiation with wavelengths ranging from about one meter to one millimeter corresponding to frequencies between 300 MHz and 300 GHz respectively. Different sources define different frequency ran ...

s were being used experimentally. In 1926

William T. Bovie William T. Bovie (September 11, 1882 – January 1, 1958) was an American scientist and inventor. He is credited with conceptualizing the field of biophysics and with inventing a modern medical device known as the Bovie electrosurgical generator. ...

discovered that RF currents applied to a scalpel could cut and cauterize tissue in medical operations, and

generators or "Bovies" have been used in surgery ever since.

References

{{reflist Medical physics Radio technology

History

See also

References