Electromagnetic and thermal modeling of SAR and temperature fields in tissue due to an RF decoupling coil

Hand, J.W.; Lau, R W M; Lagendijk, J J W; Ling, Junxiao; Burl, Mike; Young, I. R.

doi:10.1002/(sici)1522-2594(199907)42:1<183::aid-mrm24>3.0.co;2-i

Cited by 52 publications

(45 citation statements)

References 32 publications

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“…(16,22,23). Furthermore, similar predictions to those reported here are described by Nelson and Nunnenly (24) who used a hemispherical tissue layered numerical model of the human head/brain.…”

supporting

confidence: 85%

Numerical Modeling of Temperature Distributions within the Neonatal Head

Hand²,

et al. 2000

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Introduction of hypothermia therapy as a neuroprotection therapy after hypoxia-ischemia in newborn infants requires appraisal of cooling methods. In this numerical study thermal simulations were performed to test the hypothesis that cooling of the surface of the cranium by the application of a cooling bonnet significantly reduces deep brain temperature and produces a temperature differential between the deep brain and the body core. A realistic threedimensional (3-D) computer model of infant head anatomy was used, derived from magnetic resonance data from a newborn infant. Temperature distributions were calculated using the Pennes heatsink model. The cooling bonnet was at a constant temperature of 10°C. When modeling head cooling only, a constant body core temperature of 37°C was imposed. The computed result showed no significant cooling of the deep brain regions, only the very superficial regions of the brain are cooled to temperatures of 33-34°C. Poor

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confidence: 85%

Numerical Modeling of Temperature Distributions within the Neonatal Head

Hand²,

et al. 2000

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“…where the different values for (material density), c (heat capacity), k (thermal conductivity), w (perfusion by blood), and Q m (heat generated by metabolism) for several different tissues were acquired from the literature (13)(14)(15)(16)(17). The values used in these calculations are given in Table 1, unless otherwise specified.…”

Section: Calculation Of Temperaturementioning

confidence: 99%

Temperature and SAR calculations for a human head within volume and surface coils at 64 and 300 MHz

Collins¹,

Liu²,

Wang³

et al. 2004

Magnetic Resonance Imaging

259

242

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Purpose: To examine relationships between specific energy absorption rate (SAR) and temperature distributions in the human head during radio frequency energy deposition in MRI. Materials and Methods:A multi-tissue numerical model of the head was developed that considered thermal conductivity, heat capacity, perfusion, heat of metabolism, electrical properties, and density. Calculations of SAR and the resulting temperature increase were performed for different coils at different frequencies.Results: Because of tissue-dependant perfusion rates and thermal conduction, there is not a good overall spatial correlation between SAR and temperature increase. When a volume coil is driven to induce a head average SAR level of either 3.0 or 3.2 W/kg, it is unlikely that a significant temperature increase in the brain will occur due to its high rate of perfusion, although limits on SAR in any 1 g of tissue in the head may be exceeded. Conclusion:Attempts to ensure RF safety in MRI often rely on assumptions about local temperature from local SAR levels. The relationship between local SAR and local temperature is not, however, straightforward. In cases where high SAR levels are required due to pulse sequence demands, calculations of temperature may be preferable to calculations of SAR because of the more direct relationship between temperature and safety.

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“…In response to these needs, several authors have reported calculations of the spatial dependence of the B 1 field and/or the specific absorption rate (SAR) in anatomically realistic models (7)(8)(9)(10)(11)(12)(13)(14) associated with a variety of coils. In ref.…”

mentioning

confidence: 99%

SAR and Temperature Changes in the Leg Due to an RF Decoupling Coil at Frequencies Between 64 and 213 MHz

Hand

Lagendijk

Hajnal

et al. 2000

J. Magn. Reson. Imaging

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Specific absorption rate (SAR) due to a butterfly surface coil in a realistic model of the leg was calculated for frequencies 64 < < 213 MHz. The resulting temperature distribution and temperature changes (⌬T) were found using the bioheat transfer equation. To compare results at different frequencies, the minimum B-field within the coil's footprint in the plane parallel to the coil but displaced 50 mm from it was kept constant. To achieve the same minimum B-field as that associated with operation at 64 MHz that was compliant with safety guidelines (peak SAR in 1 cm 3 of tissue of 2.3 W/kg), it was predicted that SAR would exceed recommended levels when > 149 MHz.

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Electromagnetic and thermal modeling of SAR and temperature fields in tissue due to an RF decoupling coil

Cited by 52 publications

References 32 publications

Numerical Modeling of Temperature Distributions within the Neonatal Head

Numerical Modeling of Temperature Distributions within the Neonatal Head

Temperature and SAR calculations for a human head within volume and surface coils at 64 and 300 MHz

SAR and Temperature Changes in the Leg Due to an RF Decoupling Coil at Frequencies Between 64 and 213 MHz

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