Biological / EM Effects
XFdtd® for calculation of biological effects of electromagnetic fields
- Developed to provide accurate prediction of the interaction of electromagnetic fields with biological tissues.
- Includes important Bio-EM calculation capabilities such as saving of all steady state conduction currents, electric fields, and magnetic fields.
- Includes automatic calculation of Specific Absorption Rate (SAR) including whole body, 1 gram, and 10 gram averages.
These special features are in addition to XFdtd standard features. XFdtd Bio-Pro provides for automatic stepping through the geometry of false color displays of the field and SAR intensities. Surface currents, on the surface of a cell phone for example, are automatically calculated and displayed.
"I use Remcom's XFdtd electromagnetic simulation software for my MRI safety studies because it has demonstrated the ability to provide outstanding accuracy in simulation of MRI. XFdtd is used by all three of the leading producers of MRI equipment and its results are considered something of a standard in this type of simulation."
The FDTD method is recognized as the best approach for making these calculations. Here is an excerpt from "Evaluating Compliance with FCC Guidelines for Human Exposure to Radio-frequency Electromagnetic Fields-Additional Information for Evaluating Compliance of Mobile and Portable Devices with FCC Limits for Human Exposure to Radio-frequency Emissions--Supplement C (Edition 97-01) to OET Bulletin 65 (Edition 97-01), December 1997," written by Kwok Chan, Robert F. Cleveland, Jr., and David L. Means, Office of Engineering and Technology, Federal Communications Commission, Washington, D.C. 20554:
"Currently, the finite-difference time-domain (FDTD) algorithm is the most widely accepted computational method for SAR modeling.... This method adapts very well to the tissue models which are usually derived from MRI or CT scans...such as those available from the visible man project.. FDTD offers great flexibility in modeling the inhomogeneous structures of anatomical tissues and organs. The FDTD method has been used in many far-field electromagnetic applications during the last three decades. With recent advances in computing technology, it has become possible to apply this method to near-field applications for evaluating handsets."
XFdtd has been extensively validated for Bio-EM calculations including prediction of SAR levels. For example, Ericsson Radio Systems has used XFdtd for calculations of input impedance, electric fields, and SAR levels for a spherical test geometry. They obtained excellent agreement with measured results as reported in "Measurements and FDTD Computations of the IEEE SCC 34 Spherical Bowl and Dipole Antenna" by Martin Siegbahn and Christer Törnevik.
More recently a new test structure of a flat phantom has been defined for validating SAR. The flat phantom is described in its entirety in the report IEEE P1528 “Recommended Practice for Determining the Peak Spatial-Average Specific Absorption Rate (SAR) in the Human Head from Wireless Communications Devices: Measurement Techniques.” A table of validation results from XFdtd for the flat phantom is given in the flat phantom example.
The Flat Phantom calibration geometry is generated with XFdtd's built-in geometry modeler. For cell phones the SAM head is often used, and XFdtd quickly meshes this geometry from CAD files that are provided free of charge. But for some applications a more accurate FDTD body mesh is required. For these situations Remcom provides human body meshes. These meshes are obtained from the Visible Human Project data in collaboration with the Hershey Medical Center.