title: Whole-body and local RF absorption in human models as a function of anatomy and position within 1.5T MR body coil.
abstract: OBJECTIVE
  Radiofrequency energy deposition in magnetic resonance imaging must be limited to prevent excessive heating of the patient. Correlations of radiofrequency absorption with large-scale anatomical features (e.g., height) are investigated in this article.
  
  
  METHODS
  The specific absorption rate (SAR), as the pivotal parameter for quantifying absorbed radiofrequency, increases with the radial dimension of the patient and therefore with the large-scale anatomical properties. The absorbed energy in six human models has been modeled in different Z-positions (head to knees) within a 1.5T bodycoil.
  
  
  RESULTS
  For a fixed B1+ incident field, the whole-body SAR can be up to 2.5 times higher (local SAR up to seven times) in obese adult models compared to children. If the exposure is normalized to 4 W/kg whole-body SAR, the local SAR can well-exceed the limits for local transmit coils and shows intersubject variations of up to a factor of three.
  
  
  CONCLUSIONS
  The correlations between anatomy and induced local SAR are weak for normalized exposure, but strong for a fixed B1+ field, suggesting that anatomical properties could be used for fast SAR predictions. This study demonstrates that a representative virtual human population is indispensable for the investigation of local SAR levels.
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: Wolfgang
authors: W
authors: Kainz
authors: Klaas P
authors: KP
authors: Pruessmann
authors: Niels
authors: N
authors: Kuster
mesh_terms: D065638:Absorption, Radiation; D000293:Adolescent; D000328:Adult; D001822:Body Burden; D049628:Body Size / Q000502:physiology*; D002648:Child; D002675:Child, Preschool; D003198:Computer Simulation; D005260:Female; D006801:Humans; D008297:Male; D008953:Models, Anatomic; D008954:Models, Biological; D056888:Patient Positioning / Q000379:methods*; D011874:Radiometry / Q000379:methods*; D051598:Whole Body Imaging / Q000379:methods*; D055815:Young Adult