Siemens MAGNETOM Avanto Operator's Manual page 118

5 MR system operation
Noticeable effects on the
SAR limits
118
Before starting the examination, the following maximum core
temperatures of the patient apply:
◾ If the patient is allowed to be examined only in the Normal
Operating Mode, the maximum core temperature of the patient
(before starting the examination) is 38.5 °C.
◾ If the patient is allowed to be examined in the First Level
Controlled Operating Mode, the maximum core temperature of the
patient (before starting the examination) is 39.0 °C.
If the patient is allowed to be examined in the First Level
Controlled Operating Mode but the examination is performed only
within the SAR limits of the Normal Operating Mode, the
maximum core temperature of the patient is 39.5 °C.
◾ If the core temperature of the patient (before starting the
examination) is higher than 39.5 °C, the patient must not be
examined.
During the MR measurement, patients may experience heat
patient sensations on the skin and, as a consequence of the RF energy
absorption, patients may begin to perspire during the course of the
MR examination. Their pulse rate may increase as well. The individual
effects vary from patient to patient. The intensity of these effects
depends on the measurement program selected. As compared to the
Normal Operating Mode, measurement programs with considerably
higher intensities may be used in the First Level Controlled Operating
Mode. Following the examination, the body will cool off. The pulse
rate will return to normal.
Temperature control inside the examination
sensor, located near the air intake for the tunnel ventilation, monitors
the room temperature. If the room temperature exceeds 25°C, the
SAR limits are regulated and lowered by 0.25 W/kg per °C exceeding
25°C. As a result, the parameters of certain MR measurement
sequences may need to be adjusted.

Considering all possible tolerances, the SAR values (quantities)
are always calculated based on the worst-case assumption. This
ensures that the specific SAR limit is maintained.
room: A temperature
MR System | Operator Manual
Print No. MR-01501G.621.02.02.02