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Medical Devices and Systems Exposure and Dosimetry
6.4 Electromagnetic Compatibility
6.4.1 Sources
Medical devices may emit EMFs in an unintended manner either as fringe fields or stray
fields of intended EMF emission (e.g., magnetic therapy devices, diathermy devices,
and MRI) or as an unintended side effect of their intended function (e.g., RF surgery
devices) or just as a side effect of electric energy consumption or transformation of voltages (e.g., transformer).
Another source of interference is from the integration of wireless technology into the
infrastructure of hospitals (smart building concepts) for (bedside) monitoring, recordkeeping, and intercommunication (of equipment and personnel purposes), as well as
RF-based identification (RFID), control, and tracking.
These emissions may have the following consequences:
• Unintended exposure of sensitive regions of the patient outside the treatment
zone (e.g., diathermy and hyperthermia)
• Exposure of tissues along the communication pathway during data transmission
from or to implanted devices
• Unintended exposure of internal organs by incorporated EMF sources (e.g., magnets of capsule endoscopes and ferromagnetic nanoparticles)
• Exposure of medical staff (e.g., surgeons during RF surgery, medical assistants
during diathermy, or when moving the patient in or out of MRI devices)
• Exposure of accompanying persons, for example, during open MRI examinations
of children
• Exposure of the general public, for example, in waiting areas or aisles due to outreaching fields from field sources like MRI
• Exposure of workers, service personnel, or room cleaning service (e.g., around
MRI scanners or around beam guiding magnets of ultra-high energy ion therapy
devices)
• EMI with implanted electronic devices of patients (which may, for example,
inhibit cardiac pacemaker pulse delivery, change the dose rate of implanted drug
delivery devices, and induce noise in electronic hearing aids) (Gustrau et al. 2002)
• EMI with other medical electronic devices. This may have severe consequences in the case of patient monitors (e.g., ECG monitor) or life-supporting
devices (e.g., infusion pumps). EMI can cause critical care medical devices to malfunction with severe consequences such as inappropriate therapy, patient injury,
and mortality (COMAR 1998).
• Degradation of biosignals (e.g., electrocardiogram and electroencephalogram)
during patient monitoring
6.4.1.1 RF Surgery
During RF surgery, in the worst case, a surgeon’s hands are exposed to a continuous
and pulsed RF wave whose magnetic field strength is 0.75 A/m (electric field strength
400 V/m). Occasionally, stray radiation may exceed ICNIRP’s occupational exposure guidelines, especially close to the patient return plate. Of particular concern is