Medtronic DBS Mode D'emploi page 24

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Appendix A: Electromagnetic interference (EMI) and
mechanical interference
Electromagnetic interference (EMI) is a field (electrical, magnetic, or a combination of
both) that is generated by various types of equipment or environmental devices found in
medical, work, and home environments. These EMI sources may generate enough
interference to change the parameters of a neurostimulator, turn a neurostimulator off and
on, or cause a neurostimulator to surge, shock, or jolt the patient.
In addition, it is possible for the extension, lead, or both to "pick up" electromagnetic
interference and deliver excess voltage, which can in turn deliver an excessive amount of
heat to the brain (or other tissues in contact with the lead or extension).
Refer to the sections that follow for guidelines on the interaction of electromagnetic
interference and an implanted brain stimulation system.
Types of electromagnetic interference (EMI)
Electromagnetic interference generated by medical equipment and devices found in
everyday environments (eg, home, work, or public places) can be categorized into three
types of EMI. See Table 1 for a description of these three types of EMI.
EMI type
Conductive current—Conducted current
flow is introduced by the EMI source or
medical equipment touching the body.
Induced/coupled current—Current flow
introduced by a magnetic or electrical field,
where the energy travels through the air (no
physical contact). Induced or coupled current
may be generated from other medical
equipment or EMI source.
Radiated energy—Electromagnetic (EM)
radiation is energy traveling through air,
named after the manner it is produced: x-
rays—produced by tungsten x-ray tubes,
gamma rays—produced by radioactive
nuclei, etc.
All three types of EMI can occur alone or in combination and may generate enough
interference to:
▪
change/reprogram the neurostimulator parameters.
▪
turn the neurostimulator on or off.
20 English Information for prescribers 2017-05-01
Table 1. Types of EMI and examples
Example
For example, conductive current flow in
body tissue that is produced between an
electrocautery tool and grounding plate.
For example, inductive current flow could
be induced in an implanted lead system by
the strong magnetic field of an MRI scan.
For example, a high energy x-ray beam
directed at the electrical circuitry of the
implanted neurostimulator can potentially
disrupt the neurostimulator output.