hyperthermia is the technique that neglects the use of chemicals or harmful radiations. The elevated body temperature can damage the cancerous cells.
Magnetic field itself does not carry heat! It creates heat after interaction with certain particles inside the body.
The heat produced as a result of such interaction damage both cancer cell/tissues and normal cells/tissues. Cancer cells are more vulnerable to heat than normal cells, so the cancer cells are damaged more.
And also be noted that it is not easy to control the temperature because of many factors, so in practice the damage is usually collateral.
Sajjad Ur Rehman is right. Magnetic field itself does not produce heat! It creates heat after interaction with the magnetic materials in the tumor site.
You can control the target for drugs, preventing the collateral damage to normal cells.
The situation is slightly more complicated than stated in the two preceding answers. First of all heat is produced not by the magnetic field, but by ac magnetic field usually in the rf range.
Even the body tissue itself is heated via eddy currents - the soft tissues consist mostly of electrically conducting liquids. In order to increase the heating effect of the rf field magnetic particles are used, transported to the needed position by e.g. the gradient magnetic field (now a dc field). The magnetic particles usually of nanosizes produce heat by the magnetic losses, mostly the hysteretic ones.
As correctly stated by Sajjad Ur Rehman, there's a difference in the vulnerability of the healthy and tumourous cell to temperature and for the human body cells the critical temperature lies somewhere around 42 centigrades. Another serious condition that has to be fulfilled for successful use of this difference consists in the fact, that total destruction (necrosis) of the tumour cells will lead to the poisoning of the the blood and generally sepsis of the organism and thus the cells should be only brought to the state of controlled destruction (apoptosis) where the immune response of the body is able to deal with the debris of the destroyed cells.
And the process of keeping the temperature at a given place at the required value is complicate in a living organism by its thermoregulating properties.
There's plenty of literature on the subject, e.g. explanatory
https://www.diffen.com/difference/Apoptosis_vs_Necrosis
For hyperthermia treatment of cancer see e.g.
Article Hyperthermia: Role and Risk Factor for Cancer Treatment
There are different ways to deliver magnetic field and magnetic fluid mediated cancer hyperthermia. In some optimized conditions, it is less likely the adjacent tissues get damaged. Whereas, under the non-optimized conditions, MFH probably does damage to healthy tissues. There is much more to this; I would suggest you read the following article.
"Kozissnik, B., Bohorquez, A.C., Dobson, J. and Rinaldi, C., 2013. Magnetic fluid hyperthermia: advances, challenges, and opportunity. International Journal of Hyperthermia, 29(8), pp.706-714."
As mentioned above, electromagnetic fields carry energy that can excite the surrounding tissue and result in tissue damage from eddy currents.
The amount bearable is generally expressed by the product of the magnetic field ampliude H0 and the magnetic field frequency f: Limit
The answers provided by Dr. Engelmann and Dr. Karel are correct and essentially summarizes the situation.
I would like to add the following points.
1) Oscillating magnetic field (at RF) will generate eddy current heating in tissue materials. The amount of heating and the related temperature elevation depends on several factors. But the major external factors are field amplitude, frequency and tissue size (over which integration is performed to calculate volumetric heating). There is a physiological limit on the product of field amplitude and frequency, which is known as Brezovich's limit (see the details provided by Dr. Engelmann). Depending on actual condition, like tissue size, exposure time, the product of field amplitude and frequency can be optimized to reduce undesired tissue heating.
2) However, this heating is common to healthy and cancer tissue (without considering depth variation) and administration of magnetic nanoparticles in tumor location will cause additional heating due to relaxation and/ or hysteresis losses, which is called magnetic fluid hyperthermia. Details of this process is a separate research topic and there are large no. of literature available.
3) In general, a heating in the range of 42 deg. C is considered to be adequate for causing metabolic damage in cancerous cells. However, the actual temperature and the duration over which temperature needs to be maintained over 42 deg. C varies with size, shape, location and type of tumor (and also on chemical aspects, ph range, leaky vasculature around tumor and oxygen availability, etc.).
4) The damage to healthy cells will definitely occur, if they are exposed to higher temperature for a considerable duration and designing target specific magnetic nanoparticles capable of delivering high localized heating is an open research problem.
5) However, it must be noted that cancerous cells are reported to be more susceptible to temperature increase. In this aspect necrosis and apoptosis needs to be understood.
Also the treatment efficiency of chemo or radio-therapy has been reported to enhance, when the cancerous cells are exposed to higher temperature (42 deg. C).
In summary: Yes RF magnetic field heats up healthy tissues. But the temperature rise can be controlled by varying field amplitude and frequency. Use of magnetic nano particle in cancer locations is for generating heat at a much higher rate than the eddy current heating of the tissues. Minimizing thermal dose to healthy tissues is a question of research.
And hyperthermia does not avoid chemo or radio-therapy. There are several studies on multi-modal hyperthermia (hyperthermia + photo dynamic or hyperthermia + chemo therapy), hyperthermia + drug delivery and hyperthermia + brachytherapy or radiotherapy as concomitant treatment protocol.
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