title: Thermal tissue damage model analyzed for different whole-body SAR and scan durations for standard MR body coils.
abstract: OBJECTIVE
  This article investigates the safety of radiofrequency induced local thermal hotspots within a 1.5T body coil by assessing the transient local peak temperatures as a function of exposure level and local thermoregulation in four anatomical human models in different Z-positions.
  
  
  METHODS
  To quantize the effective thermal stress of the tissues, the thermal dose model cumulative equivalent minutes at 43°C was employed, allowing the prediction of thermal tissue damage risk and the identification of potentially hazardous MR scan-scenarios. The numerical results were validated by B1 (+) - and skin temperature measurements.
  
  
  RESULTS
  At continuous 4 W/kg whole-body exposure, peak tissue temperatures of up to 42.8°C were computed for the thermoregulated model (60°C in nonregulated case). When applying cumulative equivalent minutes at 43°C damage thresholds of 15 min (muscle, skin, fat, and bone) and 2 min (other), possible tissue damage cannot be excluded after 25 min for the thermoregulated model (4 min in nonregulated).
  
  
  CONCLUSIONS
  The results are found to be consistent with the history of safe use in MR scanning, but not with current safety guidelines. For future safety concepts, we suggest to use thermal dose models instead of temperatures or SAR. Special safety concerns for patients with impaired thermoregulation (e.g., the elderly, diabetics) should be addressed.
authors: IT'IS Foundation, Zurich, Switzerland; Institute for Biomedical Engineering, University and ETH Zurich, Zurich, Switzerland.
authors: Manuel
authors: M
authors: Murbach
authors: Esra
authors: E
authors: Neufeld
authors: Myles
authors: M
authors: Capstick
authors: Wolfgang
authors: W
authors: Kainz
authors: David O
authors: DO
authors: Brunner
authors: Theodoros
authors: T
authors: Samaras
authors: Klaas P
authors: KP
authors: Pruessmann
authors: Niels
authors: N
authors: Kuster
mesh_terms: D001822:Body Burden; D001833:Body Temperature Regulation / Q000528:radiation effects*; D002058:Burns, Electric / Q000209:etiology* / Q000503:physiopathology*; D003198:Computer Simulation; D004867:Equipment Design; D019544:Equipment Failure Analysis; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000009:adverse effects* / Q000295:instrumentation* / Q000592:standards; D008954:Models, Biological; D011829:Radiation Dosage; D011874:Radiometry / Q000379:methods; D012016:Reference Values; D013557:Switzerland; D014916:Whole-Body Irradiation / Q000009:adverse effects* / Q000295:instrumentation*
keywords: CEM43; SAR; local field enhancement; safety; thermal dose