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

Abstract

Purpose: 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. Materials and Methods: Here we perform a simple study comparing the maximum SAR averaged over any 1 cm3 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 cm3. Results: Over the range of model resolutions from 8-100 Yee cells per cm3, there is only a 16% variation in maximum SAR in any 1 cm3 of tissue in the head, and only a 7% variation in SAR averaged over the entire head. Conclusion: While it is always desirable to perform SAR calculations with the greatest possible accuracy, in calculations of the maximum SAR levels in any 1 cm3 of tissue, spatial resolutions greater than 5 mm may not yield notably different results than those with a spatial resolution of 5 mm. © 2003 Wiley-Liss, Inc.