A Fast Method to Estimate the SAR Distribution From Temperature Increased Maps

Objectives: Estimation of Specific energy Absorption Rate (SAR) is critical to assess RF safety for devices that rely on the transmission of electromagnetic energy, such as cellphones or MRI coils. SAR generates local heat which can damage human tissues and it is usually estimated through numerical simulations. We describe a method to estimate the SAR distribution in phantoms that is fast and not computationally demanding, based on the evaluation of temperature increase maps. Technology or Method: The presented method relies on the inversion of a previously published method to quickly estimate the temperature increase with the knowledge of the SAR distribution and thermal properties. By reversing the process, we can estimate the SAR from temperature increase maps and material thermal properties. To demonstrate the method, we utilize temperature maps measured with MRI-based thermography and compare the estimated SAR maps with those obtained through electromagnetic simulations. We have performed these comparisons with two datasets, one 2D and one 3D, and we have considered the impact of potential sources of errors such as the acquisition time and discontinuities at the interface air/sample. Results: The method can estimate SAR distribution from experimental temperature increase maps within few seconds, and produces SAR distributions similar to those from simulation of the experimental situation. Clinical or Biological Impact : The method we present can quickly estimate SAR distribution to assess RF safety of radiofrequency devices.