Analysis of electromagnetic wave interaction with biological tissue using CG-FFT method

Recent developments in electromagnetic (EM) application often require the knowledge of EM interaction with biological tissue. For example, in magnetic resonance imaging (MRI), detailed knowledge of the EM field distribution in the MRI resonator in the presence of a patient is required to further improve the MRI image quality. In the antenna design for wireless communication, knowledge of the EM interaction with the human head plays an important role. First for the safety concern, we need to know the EM field distribution, radiated by the handset, in the human head. Second, for effective transmission and reception, we need to know how the antenna radiation pattern is affected by the presence of the human head. In the past, the finite-difference time-domain (FD-TD) method has been used to investigate the effect of the EM wave on the biological tissue. This method has the ability of modeling the complex objects but requires extensive computational time. We propose to use the conjugate-gradient fast Fourier transform (CG-FFT) method to calculate the EM distribution within biological materials. Compared with the FD-TD method, the CG-FFT method has the advantage of comparable computer memory requirement but less CPU time. Once the EM field distribution within the biological tissue is calculated, other important parameters such as the specific absorbing ratio (SAR) for safety design can also be obtained.