Objective
To define thresholds of safe local temperature increases for MR equipment that exposes patients to radiofrequency fields of high intensities for long duration. These MR systems induce heterogeneous energy absorption patterns inside the body and can create localised hotspots with a risk of overheating.
Methods
The MRI + EUREKA research consortium organised a “Thermal Workshop on RF Hotspots”. The available literature on thresholds for thermal damage and the validity of the thermal dose (TD) model were discussed.
Results/Conclusions
The following global TD threshold guidelines for safe use of MR are proposed:
All persons: maximum local temperature of any tissue limited to 39 °CPersons with compromised thermoregulation AND
Uncontrolled conditions: maximum local temperature limited to 39 °CControlled conditions: TD<2 CEM43°CPersons with uncompromised thermoregulation AND
Uncontrolled conditions: TD<2 CEM43°CControlled conditions: TD<9 CEM43°C
The following definitions are applied:
Controlled conditions
A medical doctor or a dedicated trained person can respond instantly to heat-induced physiological stress
Compromised thermoregulation
All persons with impaired systemic or reduced local thermoregulation
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