Increasing exposure of humans to man-made electromagnetic fields from power-line to microwave frequencies has necessitated obtaining dosimetric information for use in the evaluation of possible biohazards. The thrust of our project has been to develop high-resolution anatomically based electromagnetic models that can be used for calculation of absorbed energy and induced currents and their distributions for near-field or far- field,partial-body or whole-body exposure conditions. In addition to providing information on some relevant occupational situations such as exposure to RF sealers and induction heaters, work done during the current project period has provided useful information on distributions of absorbed energy for several important biomedical applications such as radiofrequency (RF) fields of magnetic resonance imagers (MRI), and several types of hyperthermia applicators such as capacitive plates, RF needles, and annular-phased arrays of aperture antennas and dipoles. Using the MRI data, we propose to create a new electromagnetic (EM) model of the human body with resolution on the order of a few millimeters and use it to extend the dosimetric information for human exposure to higher frequencies on the order of Gigahertz. With the recent relaxation of the safety guideline from 5 to 10 mW/cm2 for frequencies of 3 GHz or more, it is important to check if there are any regions of unacceptably high EM depositions such as the eyes, etc. For this application we will use the newly developed expanding grid method to model the important surface region with a higher degree of precision than the regions in depth. Other applications of the expanding grid method proposed to be investigated are: EM hyperthermia where the tumor shape and size will be modeled more precisely than the surrounding tissues, and RF sealers in industrially relevant settings such as screen rooms. We also propose to use the new high-resolution, anatomically based model to calculate internal E-fields and induced currents for exposure to EM fields associated with 50/60-Hz power lines. This task is proposed because of the increasing concern of health effects of EM fields at power-line frequencies and the relative inadequacy of dosimetric data in regards to the induced current densities for the tissues.
|Gandhi, O P; Wu, D; Chen, J Y et al. (1997) Induced current and SAR distributions for a worker model exposed to an RF dielectric heater under simulated workplace conditions. Health Phys 72:236-42|
|Gandhi, O P; Gao, B Q; Chen, J Y (1992) A frequency-dependent finite-difference time-domain formulation for induced current calculations in human beings. Bioelectromagnetics 13:543-55|
|Chen, J Y; Gandhi, O P (1992) Numerical simulation of annular-phased arrays of dipoles for hyperthermia of deep-seated tumors. IEEE Trans Biomed Eng 39:209-16|
|Chen, J Y; Gandhi, O P (1989) RF currents induced in an anatomically-based model of a human for plane-wave exposures (20-100 MHz). Health Phys 57:89-98|
|Orcutt, N; Gandhi, O P (1988) A 3-D impedance method to calculate power deposition in biological bodies subjected to time varying magnetic fields. IEEE Trans Biomed Eng 35:577-83|
|Zhu, X L; Gandhi, O P (1988) Design of RF needle applicators for optimum SAR distributions in irregularly shaped tumors. IEEE Trans Biomed Eng 35:382-8|
|Gandhi, O P; Chen, J Y; Riazi, A (1986) Currents induced in a human being for plane-wave exposure conditions 0-50 MHz and for RF sealers. IEEE Trans Biomed Eng 33:757-67|