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Physiological effects
Due to the presence of alternating electromagnetic fields, patients
may experience various physiological effects during MR
measurements:
◾
Peripheral nerve stimulation through low-frequency fields of the
gradient coils (
Page 110 Exposure to low frequency
◾
Warming of body tissue through RF fields of the RF transmitter coil
(
Page 112 Exposure to RF electromagnetic fields)
These physiological effects can be evaluated by the technical
quantities dB/dt (stimulations) and SAR (warming) respectively.
It is generally accepted that no published evidence supporting the
occurrence of cumulative and/or long-term effects after exposure to
EMF emitted by the MR equipment exists.
Operating modes
To prevent health risks during MR measurements, several
international organizations (for example, IEC) and various national
health organizations have published guidelines and limit values. In
compliance with country-specific approval guidelines, they are the
basis for the monitoring functions integrated in the MR system with
respect to stimulation and warming effects. The limits against too
intense stimulation and warming effects (for example, dB/dt limits
and SAR limits) are based on current scientific literature related to
safety.
Two different operating modes are available depending on the
patient’s tolerance. With respect to stimulation and warming effects,
the operating modes are defined independently of each other and
can be selected separately.
The Normal Operating Mode can be used safely for all patients. This is
the standard mode. Routine patient monitoring is required.
(
Scanning of pregnant patients with the Body coil must be limited to
the Normal Operating Mode with respect to the SAR level.
5.5
5.5.1
Normal Operating Mode
5
MR system operation
108
MR System | Operator Manual
Print No. M6-04401.621.02.02.02