Introduction
Magnetic resonance (MR) imaging is non-ionizing radiation, which is considered to be a safe diagnostic and does not cause any damage to the cell. However, there are number of studies that have been published showing that magnetic resonance imaging (MRI) cause burns. Generally, the cause of the burns in MR is a result of radiofrequency power undergoing MR examination then transformed into heat within the patient body. Electronically activated, external accessories and objects made from conductive materials also cause burns in patient tissues for example, leads and guide wires. Implants when heated can also cause burns (Haik, Daniel, Tessone, Orenstein & Winkler 2009). Excessive heating was found in patients in United States who were undergoing different procedures of MR even though they were not related to internal implants or equipment problems. These could indicate first, second, and third degree burns in the patient tissues. This will therefore show that some parts of the patient body had touched transmit RF coils. To avoid RF burns you must first know how RF occurs and then be aware of the causes and prevention. This paper point out the causes and prevention of RF burns.
How is the RF burns happened
To be able to generate MRI signal, MRI systems will need to utilize radiofrequency pulses. In MR machine there is a free space between RF coil and patient body. However, if there are conducting materials like monitors, electronic devices which are located within the RF filed, the generated electrical current will be enough to cause heating and harm in patient tissue (Schaefer, Bourland & Nyenhuis 2000). Electromagnetic fields with evaluated rates ease energy transmission through an open ground and also in the insulators. This therefore means that materials whose present lanes deliberately planned can be used without any fear of destruction throughout MR procedures. Insulation of conductive materials such as lead and wire is not enough to prevent the patient from excessive heating which will result into burns. Besides, there are particular shapes that display the incident of resonance which normally increased their tendency to contemplate RF currents (Eising, Hughes, Nolte, Jentzen & Bockisch 2010). Loops should be avoided since any existed of small gaps divided by insulation has the potential to conduct current. This can cause heating which eventually result into burn. RF currents can only be limited by the use of techniques that are of high impedance.
Causes of RF burns
There are many causes of RF burns since there are many types of burns. They include: a patient can be injured when radio frequency monitors, coils, electronic devices or any other material which is conductive is use. This will result in tissue burns and heating. More problems will be caused if materials that are conductive have extended shapes like guide wires, leads and catheters. Generally, the cause of the burns in MR is a result of radiofrequency power undergoing MR examination then transformed into heat within the patient body. Electronically activated, external accessories and objects made from conductive materials also cause burns in patient tissues for example, leads and guide wires (McJury & Shellock 2000). Implants when heated can also cause burns. Excessive heating was found in patients in United States who were undergoing different procedures of MR
Devices and implants especially those that have drawn out configuration or those that have formed loops that are conductive always cause excessive burns and heat. Patients with this conduction should not be taken through MRI procedure until experts have assessed and determined that there are no more risks in using.
Inclusion of RF power by the tissue can be illustrated as Specific Absorption Rate (SAR).This situation occurs when inductance and capacitance are equal and opposite a state which can be sustained by a conducting wire within the magnetic fields of an active MR session (Eising, Hughes, Nolte, Jentzen & Bockisch 2010). It is further speculated that several wires bundled together in a linear arrangement are also capable of thermal damage through a similar mechanism.
When a person comes in contact with RF radiator, then it means that he/she will get RF burn or shock. RF radiators are antenna which triggers current to move through its modules which is metallic in nature after which it exudes into the space (Kangarlu & Robitallie 2000). If a person gets into contact with the antenna, he/she will absorb the energy which will get into the body and move to the ground. This is the same thing which will happen if a person gets in contact with RF radiators. If a person’s skin come in direct contact with RF radiators.
RF burns can also be caused if the patient is left without insulating materials to prevent his/her skin from coming into contact with transmit RF coil during MR procedure. If transmit RF coil used during MR procedure is not well padded, it can also cause RF burns on patients (Eising, Hughes, Nolte, Jentzen & Bockisch 2010). If materials used to conduct MR procedure are not thoroughly tested, especially devices that conduct electricity such as electrodes and ECG leads then the patient will be at high risk of getting burns. If implants are carelessly used without following MR safety recommendations and criteria then the patient is likely to get burns.
If MR system has a material that conducts electricity then the patient is more likely to get burns because his/her skin will be in contact with the materials. Cables, monitoring leads, RF coils, and wires if not insulated properly can cause burns if it comes in contact with the skin (Shellock & Crues, 2004). Burns can also be caused when human tissue create conductive loop of S-shape, U-Shape or circular. If materials that conduct electricity are not positioned in the right way such that they meet at the cross-points which is the area where a cable connect with another cable, cable loops connect itself, cable is in contact with either the patient or parts of transmit RF coil then there are high chances that the patient or anyone who comes into contact with the materials will get burns.
Prevention of RF burns
The following procedure can be used to avoid burns and too much heating when MR procedures is carried out on a patient: One way in which a patient can be made ready for MR procedure is by checking that the patient’s skin is free from any kind of metallic objects such as jewelry, key chains, necklaces or bracelets. Insulated stuff for example wadding should be used to avoid the skin from touching each other and also closed loops should not be allowed to be in contact with any part of the patient’s body.
Make sure that the padding material is broad enough before inserting it amid transmit RF coil and the skin of the patient during the MR procedure. The other alternative is to ensure that the transmit RF coil is well padded (Kangarlu & Robitallie 2000). The patient should be kept away RF body coil during the MR procedure. Placing the arm of the patient over his/her head is the only way to avoid the skin from being in contact with the transmit RF body coil.
Check all materials carefully before using them in MR procedures especially devices that conduct electricity. MR safety guidelines and methods should be adhered to the latter especially when using implants that are prepared with resources that conduct electricity such as cardiac pacemakers, bone fusion stimulators, cochlear implants and neurostimulation systems. The veracity of all insulation should be well checked especially when using electric equipment. Components such as cables, monitoring leads, RF coils and wires should be well housed. Make sure that preventive maintenance is conducted regularly. Also ensure that MR System is clear of materials that conduct electricity unnecessarily. MR system should be free from wires, ECG leads, cables, EEG leads and surface RF coils that have not been used (Eising, Hughes, Nolte, Jentzen & Bockisch 2010). Those materials left inside the MR system yet are good conductors of electricity should kept away from the patient. Electrical or thermal padding should be positioned amid the patient and the material which is conductive.
Materials that conduct electricity yet still are contained inside the transmit RF coil can make the MR system repellant to conductive derailing the opportunity of creation of loops. It also important to be aware that human tissue is conductive hence may create conductive loop of either S-shape, U-shape or be circular. Materials that conduct electricity should be positioned in the right way to avoid cross-points which is where a cable is joined with another cable, cable loops connect itself, cable is in contact with either the patient or parts of transmit RF coil. Make sure that materials that are conductive are not any close to each other since transmit RF coils and cables have the potential to capacitively-couple when they are place together or near each other (Haik, Daniel, Tessone, Orenstein & Winkler 2009). Materials that conduct electricity should be positioned at the center of the MR system but facing down. They should not be placed besides MR system and they should be far away from transmit RF body coil. Materials that conduct electricity should not also be placed on top of metallic prosthesis. It is advisable that only trained individuals or those with enough experience are the ones who should operate and monitor the equipment or the device in MR environment.
All the guidelines expressed by the producer on how to safeguard and use the electronic equipments should be adhered to especially throughout the MR procedures. This will make the procedure easy and facilitate good results. Electronic devices which are not functioning properly should not be used on any patient during the MR procedure.
The patient should be regularly checked throughout when MR procedure is carried out. This will help in monitoring the patients health details such that in case he/she experience strange feeling of overheating then the MR procedure will be withdrawn immediately. After that the patient and the situation should be assessed thoroughly to identify where the problem was. If exterior part of RF coil has become futile to decouple, then there is a possibility that it will force the heights of RF deposition to go highest. The person who is in charge or who is responsible for MR system should be able to identify the problem to have been caused by a group of concentric semicircles that are present inside tissue and linked to MR image (Eising, Hughes, Nolte, Jentzen & Bockisch 2010). This can also be viewed as an unusual value of non-uniformity image that is related to transmit RF coil position.
All in all, if the instructions are efficiently adopted, then the patient will be able to remain safe all the time particularly because devices that have been activated with electricity are linked to MR procedures.
In conclusion, generally, the cause of the burns in MR is a result of radiofrequency power undergoing MR examination then transformed into heat within the patient body. Electronically activated, external accessories and objects made from conductive materials also cause burns in patient tissues for example, leads and guide wires. Implants when heated can also cause burns. Some of the ways in which burns can be prevented include: insulating material that conduct electricity, closely monitoring the patient throughout the MR procedure, avoid cross-points where cables that conduct electricity join each other and test all materials thoroughly before using them in MR procedures, adhering to MR safety guidelines and methods especially when using implants and materials that conduct electricity should be positioned at the center of the MR system but facing down.
List of References
Eising E, Hughes J, Nolte F, Jentzen, W & Bockisch, A 2010. Burn injury by nuclear magnetic resonance imaging, Clin Imaging, vol. 34 no. 4, pp. 293
Haik, J, Daniel, S, Tessone, A, Orenstein, A & Winkler, E 2009, MRI induced fourth degree burn in an extremity, leading to amputation, Journal of Health, vol.35 no. 2, pp. 294 – 297
Kangarlu, A & Robitallie, P 2000, Biological effects and health implications in magnetic resonance imaging, Journal of Concepts in Magnetic Resonance, vol.12 no. 5, pp. 321 – 359.
McJury, M & Shellock, F 2000, Auditory noise associated with MR procedures: A Review, Journal of Magn Reson Imaging, vol.12 no. 1, pp.30
Schaefer, D, Bourland, J & Nyenhuis, J 2000, Review of patient safety in time varying gradient fields, Journal of Magn Res Imaging. Vol.12 no.1, pp. 20 – 29.
Shellock, F & Crues, J 2004. MR procedures: Biologic effects, safety and patient care, Journal of Radiology, vol. 9, no. 232, pp.635 – 652.