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2. Safety > 2.3. Heat and Specific Absorption Rate (SAR)
WARNING
Because the patient may have to lie immobile for several hours during the treatment,
identify the patients with a high risk or a history of deep vein thrombosis or a similar
condition potentially affected by the long immobilization and evaluate the risks and benefits
before the treatment.
NOTICE
If the physician's evaluation indicates that the patient is in the risk group, the risk and benefits
should be explained to the patient.
2.3. Heat and Specific Absorption Rate (SAR)
WARNING
Make sure that sufficient cooling is provided during the treatment and monitor patients with
insufficient cardiac functions.
Failure to do so may result in excessive heating and hyperthermia.
NOTICE
If the physician's evaluation indicates that the patient is in the elevated risk group, the rationale for
cooling should be explained to the patient.
WARNING
When the ultrasound transducer is sonicating (emitting acoustic energy), there is a blue
sonication indicator light in the liquid container. Never put body parts into the ultrasound
field as internal tissue heating and damage may occur in seconds.
2.3.1. Specific Absorption Rate (SAR)
Both the MR system and the Sonalleve MR-HIFU system produce thermal energy, which is
absorbed by the patient during treatment. The International/European standard IEC/EN 60601-2-33
Particular Requirements for the Safety of Magnetic Resonance Equipment for Medical Diagnosis
defines limits for the acceptable tissue and body temperature rise caused by the Specific
Absorption Rate (Definition of SAR see: IEEE C.95.1-1999) of radio frequency power per unit mass
of an object. The standard sets limits for the maximum allowed rise of the patient's core
temperature. The MR scanner achieves compliance with these requirements by controlling the
SAR of the MR protocols.
The SAR limits of the MR scanner are defined for conditions with a specific room temperature
24 °C (75.2 °F) and humidity 60% and minimal air flow. In addition, the patient is assumed to be
lightly clothed. The standard uses 6 minutes as the averaging period for determining the SAR for
all tissues. For a detailed description of the SAR operating modes and temperature and humidity
levels, see the MR scanner's Instructions for Use and the standard IEC/EN 60601-2-33.
Instructions
for
Use
109745C2 / 02-2022
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