A lot many reports have emerged in the recent past investigating non-invasive RF hyperthermia using nanoparticles for cancer treatment. What are the presumed advantages of capacitive RF hyperthermia over inductive RF hyperthermia or vice versa? Since capacitive RF hyperthermia can cause heating up of ions, would its use on the body produce undesirable heating effects unlike inductive hyperthermia?
Dear Sajid Fazal,
The biggest difference is whether the technology requires invasive procedures yes or no.
In general non-invasive RF electromagnetic heating can be delivered using:
RF-capacitive coupling: two electrodes are placed on either side of the body and RF-current is flowing between both electrodes. The advantages are relative simple technology (so cheap systems). Disadvantages in most clinical applications is that the E-field is directed perpendicular on tissue transitions, more specifically those between fatty and muscle tissue. In this situation flux is constant resulting in preferential fat heating over muscle heating. Skin cooling with cold water is used to prevent over heating of fatty tissue. This works for patients with fat layers of less than 2 cm thickness. Western patients have in general fat thicknesses of more than 2 cm RF. A second disadvantage is that RF-capacitive heating does not provide a mean for focusing of RF-energy to the treatment volume. Frequencies used in clinical practice vary from 8 to 27 MHz.
RF-inductive coupling: RF-energy is transferred using inductive fields. The applicator consists often of an helical coil or pancake coil. In the early days of hyperthermia large single and multiple turn helical coils have been placed around the patient. RF-currents will be induced in the peripheral layers of the body causing heating. Deep heating is poor as in the center of the coil no currents flow. Advantages: energy coupling through air, avoiding direct contact of the heating system with the patient. Disadvantage: poor deep heating and no ability to focus heating at the target volume. Frequencies used in clinical practice vary from 8 to 27 MHz.
RF-radiative coupling: multiple radiative antennas are used to couple energy to the patient. Water is used as a coupling medium between the antenna and the human body to preferentially transfer the energy to the patient. Further the water provides also a possibility to cool the superficial tissue, reduces the antenna size (high relative permittivity) and reduce reflection of RF-energy from the skin (in comparison a tissue contrast of air-skin has 60% reflections versus nearly zero for water-skin).
The main advantage of RF-radiative energy transfer is the ability to focus RF-energy at the target volume by optimizing the phase and amplitude settings per antenna. Using hyperthermia treatment planning phase and amplitude settings can be optimized based on the feedback of measured temperatures and patient information.
All the above is explained and demonstrated in the attached papers.
Besides the non-invasive technologies one can use more invasive procedures.
The most recent technology with promising potential for selective tumor heating is nano-particle inductive heating. Multiple papers have been published on this topic. A special issue of the Int. J. of Hyperthermia was devoted to this technology. Please check this literature.
Although the ultimate idea is to coat the nano-particles with proteins that connect to receptors at the tumors cell, the current practice is that the nano-particles still must be injected directly into the tumor in order to obtain a sufficient high concentration of nano-particles to allow sufficient energy delivery to increase tumor temperature to 43°C.
Regards,
Gerard van Rhoon
Dear Sajid Fazal,
The biggest difference is whether the technology requires invasive procedures yes or no.
In general non-invasive RF electromagnetic heating can be delivered using:
RF-capacitive coupling: two electrodes are placed on either side of the body and RF-current is flowing between both electrodes. The advantages are relative simple technology (so cheap systems). Disadvantages in most clinical applications is that the E-field is directed perpendicular on tissue transitions, more specifically those between fatty and muscle tissue. In this situation flux is constant resulting in preferential fat heating over muscle heating. Skin cooling with cold water is used to prevent over heating of fatty tissue. This works for patients with fat layers of less than 2 cm thickness. Western patients have in general fat thicknesses of more than 2 cm RF. A second disadvantage is that RF-capacitive heating does not provide a mean for focusing of RF-energy to the treatment volume. Frequencies used in clinical practice vary from 8 to 27 MHz.
RF-inductive coupling: RF-energy is transferred using inductive fields. The applicator consists often of an helical coil or pancake coil. In the early days of hyperthermia large single and multiple turn helical coils have been placed around the patient. RF-currents will be induced in the peripheral layers of the body causing heating. Deep heating is poor as in the center of the coil no currents flow. Advantages: energy coupling through air, avoiding direct contact of the heating system with the patient. Disadvantage: poor deep heating and no ability to focus heating at the target volume. Frequencies used in clinical practice vary from 8 to 27 MHz.
RF-radiative coupling: multiple radiative antennas are used to couple energy to the patient. Water is used as a coupling medium between the antenna and the human body to preferentially transfer the energy to the patient. Further the water provides also a possibility to cool the superficial tissue, reduces the antenna size (high relative permittivity) and reduce reflection of RF-energy from the skin (in comparison a tissue contrast of air-skin has 60% reflections versus nearly zero for water-skin).
The main advantage of RF-radiative energy transfer is the ability to focus RF-energy at the target volume by optimizing the phase and amplitude settings per antenna. Using hyperthermia treatment planning phase and amplitude settings can be optimized based on the feedback of measured temperatures and patient information.
All the above is explained and demonstrated in the attached papers.
Besides the non-invasive technologies one can use more invasive procedures.
The most recent technology with promising potential for selective tumor heating is nano-particle inductive heating. Multiple papers have been published on this topic. A special issue of the Int. J. of Hyperthermia was devoted to this technology. Please check this literature.
Although the ultimate idea is to coat the nano-particles with proteins that connect to receptors at the tumors cell, the current practice is that the nano-particles still must be injected directly into the tumor in order to obtain a sufficient high concentration of nano-particles to allow sufficient energy delivery to increase tumor temperature to 43°C.
Regards,
Gerard van Rhoon
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