Spatial resolution of numerical models of man and calculated specific absorption rate using the FDTD method: a study at 64 MHz in a magnetic resonance imaging coil.
OBJECTIVE
To examine how fine a model resolution is necessary for calculation of specific energy absorption rate (SAR) for the human head in regions as small as 1 g.


METHODS
Here we perform a simple study comparing the maximum SAR averaged over any 1 cm(3) and SAR averaged over the entire head for several models of the same human head within the same radiofrequency coil, but with spatial resolutions varying from 8-100 Yee cells per cm(3).


RESULTS
Over the range of model resolutions from 8-100 Yee cells per cm(3), there is only a 16% variation in maximum SAR in any 1 cm(3) of tissue in the head, and only a 7% variation in SAR averaged over the entire head.


CONCLUSIONS
While it is always desirable to perform SAR calculations with the greatest possible accuracy, in calculations of the maximum SAR levels in any 1 cm(3) of tissue, spatial resolutions greater than 5 mm may not yield notably different results than those with a spatial resolution of 5 mm.
Collins
Christopher M
CM
Center for NMR Research, Department of Radiology, The Pennsylvania State University College of Medicine, Hershey, Pennsylvania 17033, USA. cmcollins@psu.edu
Smith
Michael B
MB
D006257:Head / Q000033:anatomy & histology*; D006801:Humans; D008279:Magnetic Resonance Imaging; D008962:Models, Theoretical