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

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: 1. All persons: maximum local temperature of any tissue limited to 39 °C. 2. : a. Uncontrolled conditions: maximum local temperature limited to 39 °C. b. Controlled conditions: TD<2 CEM43°C. 3. : a. Uncontrolled conditions: TD<2 CEM43°C. b. Controlled conditions: TD<9 CEM43°C. The following definitions are applied: [Table: see text

Thresholds for thermal damage to normal tissues: an update

The purpose of this review is to summarise a literature survey on thermal thresholds for tissue damage. This review covers published literature for the consecutive years from 2002–2009. The first review on this subject was published in 2003. It included an extensive discussion of how to use thermal dosimetric principles to normalise all time-temperature data histories to a common format. This review utilises those same principles to address sensitivity of a variety of tissues, but with particular emphasis on brain and testis. The review includes new data on tissues that were not included in the original review. Several important observations have come from this review. First, a large proportion of the papers examined for this review were discarded because time–temperature history at the site of thermal damage assessment was not recorded. It is strongly recommended that future research on this subject include such data. Second, very little data is available examining chronic consequences of thermal exposure. On a related point, the time of assessment of damage after exposure is critically important for assessing whether damage is transient or permanent. Additionally, virtually no data are available for repeated thermal exposures which may occur in certain recreational or occupational activities. For purposes of regulatory guidelines, both acute and lasting effects of thermal damage should be considered