An Approach to Rapid Calculation of Temperature Change in Tissue Using Spatial Filters to Approximate Effects of Thermal Conduction
Giuseppe Carluccio, Danilo Erricolo, Sukhoon Oh and Christopher M. Collins
Volume:60 , Issue:6, Page(s): 1735 – 1741
For assuring safety when radio and microwave frequency electromagnetic fields are applied to the human body, it is important to be able to predict the temperature increase. Due to the effects of tissue perfusion by blood and thermal conduction of heat, the pattern for actual temperature increase is often very different from that for tissue heating or Specific Energy Absorption Rate (SAR). Calculations of the temperature change throughout complex three-dimensional objects, such as the human body, however, take a long time because of the need to consider how heat is conducted through the tissue. Here we present a method to greatly increase the speed of such calculations by approximating the effects of thermal conduction with a low-pass spatial filter designed to have an effect of “blurring” the temperature distribution in a manner similar to the effect of thermal conduction. The method was applied to a few different cases relevant to magnetic resonance imaging, and results were compared to those from a rigorous finite difference (FD) implementation of the Pennes Bioheat equation. In comparison with the FD method, the proposed method is seen to decrease calculation times by well over an order of magnitude while introducing only moderate maximum errors (on the order of %15). While there are some minor differences between the results produced with the fast spatial filter approximation and those from the FD approach, it is clear that the temperature estimation results provide information much different and more directly relevant to safety and potential tissue damage than the commonly-used 10 g averaged SAR does. Therefore, since the proposed method is faster to compute than 10 g SAR averages and more directly related to safety, our approach provides one additional argument in favor of using temperature for the development of future safety regulations.