**3.9. Radiofrequency electromagnetic fields effects**

The MRI system has electromagnetic coils in a transmitter within it that delivers the radio‐ frequency (RF) pulses during imaging. When tissues absorb the RF energy, tissue heating can occur, mostly in patients with poor thermoregulatory control (Dempsey *et al.,* 2002). The rate at which RF energy is deposited in tissue is known as the specific absorption rate (SAR), measured in units of watts per kilogram (w/kg) (Centre for Devices and Radiological Health, 1997). The maximum allowed SAR is 3W/kg which is averaged over ten minutes for head imaging and 4W/kg for whole body imaging, averaged over fifteen minutes (Centre for Devices and Radiological Health, 2003).

Radiofrequency fields can cause skin burns if monitor cables or wires are permitted to form conductive loops with themselves or with other body parts (Kanal *et al.,* 2002). Temporary metallic intra cardiac pacing wires will behave like antennae and conduct electromagnetic waves, also resulting in thermal tissue injury (Dempsey *et al.,* 2002). Ra‐ diofrequency signals emitted during the MR examination can affect non- MR-compatible programmed infusion pumps, resulting in erratic performance. Affected pumps could de‐ liver higher or lower than desired volumes of pressor agent, analgesics, sedative or dex‐ trose and electrolytic solutions, all of which cause serious physiological consequences particularly, infants (Cornette*et al.,* 2002).
