Abstract
This paper presents the modeling of hemoglobin at optical frequency (250 nm – 1000 nm) using the unconditionally stable fundamental alternating-direction-implicit finite-difference time-domain (FADI-FDTD) method. An accurate model based on complex conjugate pole-residue pairs is proposed to model the complex permittivity of hemoglobin at optical frequency. Two hemoglobin concentrations at 15 g/dL and 33 g/dL are considered. The model is then incorporated into the FADI-FDTD method for solving electromagnetic problems involving interaction of light with hemoglobin. The computation of transmission and reflection coefficients of a half space hemoglobin medium using the FADI-FDTD validates the accuracy of our model and method. The specific absorption rate (SAR) distribution of human capillary at optical frequency is also shown. While maintaining accuracy, the unconditionally stable FADI-FDTD method exhibits high efficiency in modeling hemoglobin.
Highlights
The information on optical properties of human blood is crucial for many medical applications
The finite-difference timedomain (FDTD) method [11, 12] has been widely used for solving electromagnetic problems and modeling electromagnetic wave propagation in various media
Since we have successfully modeled human blood across a range of optical frequency based on complex conjugate pole-residue pairs along with its implementation using the FADI-FDTD method, the power loss density formula in Eq (30) can be modified to better suit our scenario
Summary
The information on optical properties of human blood is crucial for many medical applications. The conventional alternating-direction-implicit finite-difference time-domain (ADI-FDTD) method [14, 15], on the other hand, has unconditional stability feature where the time step is no longer restricted by the CFL stability criterion This has circumvented the above limitation in its own right. Are there tridiagonal systems that need to be solved, the right-hand-side (RHS) of each equations involve many update coefficients and field variables, which calls for considerable arithmetic operations and memory indexing These overheads has been overcome by the introduction of the fundamental alternating-direction-implicit finite-difference time-domain (FADI-FDTD) method [16,17]. While the evolution of computational electromagnetic in time domain from explicit FDTD method to FADI-FDTD has been encouraging, there is still a lack of appropriate complex permittivity models for biological media (in this case, hemoglobin) at optical frequency. Some numerical examples are provided to validate the proposed method and to demonstrate some electromagnetic wave interactions with human blood at optical frequency
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