MRI scanners can produce heat in rare circumstances.
Magnetic resonance (MR) imaging is considered to be a relatively safe diagnostic modality. However, damaged radiofrequency coils, physiologic monitors, electronically-activated devices, and external accessories or objects made from conductive materials have caused excessive heating, resulting in burn injuries to patients undergoing MR procedures. Heating of implants and similar devices may also occur, but this tends to be problematic primarily for objects made from conductive materials that have elongated shapes or that form loops of a certain diameter. For example, excessive MRI-related heating has been reported for leads, guidewires, certain types of catheters (e.g., catheters with thermistors or other conducting components), and certain external fixation or cervical fixation devices.
skin-to-skin contact points were suspected to be responsible for these injuries, however, the exact mechanism responsible for these incidents is unknown.
In 2004, more than 22,000 magnetic resonance imaging (MRI) scanners performed some 65 million studies worldwide, with about half done in the United States. Magnetic resonance imaging has a stellar safety record and is not considered a significant risk. However, it is not hazard free. The worst danger is probably the projectile risk of magnetic objects being sucked into the main magnet, which is dealt with by diligent screening and control of access. Less dramatically, perhaps, is radiofrequency (RF) power deposition and heating in the body due to the MRI excitation field. Power deposition is measured by the specific absorption rate (SAR) in watts per kilogram or by direct thermometry. A third hazard, related to both of these, is the effect of an MRI scanner on devices and leads that are implanted in patients.
Some tattoo ink contains traces of metal, but most tattoos are safe in an MRI scanner. Tell the radiographer immediately if you feel any discomfort or heat to your tattoo.
The essence of these reports seems to be that MRI scans do not normally produce heating in the vast majority of scans performed but that in very rare cases heating can occur either because of conductive implants or due to skin to skin contact or perhaps other circumstances.
Yes, in rare circumstances, MRI scans can produce uncomfortable heating or even burns.
No, "exciting protons in the body" occurs during every MRI scan, "a sensation of extreme heat" does not and is rare.