CEM43A°C thermal dose thresholds: a potential guide for magnetic resonance radiofrequency exposure levels?

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. 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. The following global TD threshold guidelines for safe use of MR are proposed: 1. All persons: maximum local temperature of any tissue limited to 39 A degrees C Persons with compromised thermoregulation AND (a) Uncontrolled conditions: maximum local temperature limited to 39 A degrees C Controlled conditions: TD < 2 CEM43A degrees C Persons with uncompromised thermoregulation AND (a) Uncontrolled conditions: TD < 2 CEM43A degrees C Controlled conditions: TD < 9 CEM43A degrees C The following definitions are applied: Controlled conditions A medical doctor or a dedicated trained person can respond instantly to heat-induced physiological stress All persons with impaired systemic or reduced local thermoregulation aEuro cent Standard MRI can cause local heating by radiofrequency absorption. aEuro cent Monitoring thermal dose (in units of CEM43A degrees C) can control risk during MRI. aEuro cent 9 CEM43A degrees C seems an acceptable thermal dose threshold for most patients. aEuro cent For skin, muscle, fat and bone,16 CEM43A degrees C is likely acceptable.