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Electromagnetic Fields in Biological Systems
4.5.1.2 Coupling with Realistically Shaped Models
Dimbylow (1987) presented a three-dimensional finite-difference calculation of induced
current densities and short-circuit currents in a grounded, homogeneous, realistically
shaped human phantom in reference to applied ELF electric fields. He compared the
result with Kaune and Forsythes’s (1985) published experimental outcomes associated
with current density distributions at 60 Hz in a mannequin with two arms on its sides.
Hirata et al. (2001) calculated the induced electric fields and current densities in
a 5-year-old child’s body exposed to vertical 60 Hz, 1 kV/m electric fields in both
grounded and isolated conditions and compared them with those related to an adult’s
body, phantom of the University of Victoria, UVic phantom. They calculated induced
electric fields in the adult model using a hybrid method, and in the child, using a quasistatic FDTD method. In this case, the American male and corresponding American
child model were used in the calculation. They found that the induced electric fields
were lower in the child head than in the adult head. Hirata and Fujiwara (2007) computed the induced current densities in the human models based on Japanese male and
female models named TARO and HANAKO, respectively, developed by Nagaoka et al.
(2002, 2004). The resolution of the model was 2-mm 3 voxels and was segmented into
51 anatomic regions. Using a quasistatic FDTD method, Hirata and Fujiwara (2007)
computed the induced current densities in TARO and HANAKO when exposed to
vertical 60 Hz, 1 kV/m. Computational results showed that the difference in induced
current densities between TARO and HANAKO was less than 20% depending on the
tissues/organs. They pointed out that this difference was reasonable because there was
a difference of equal magnitude between NORMAN and NAOMI (Dimbylow 2005).
Additionally, they pointed out that the effect of gender and/or race on induced current
densities was comparable to or smaller than that caused in the process of computational modeling.
Dawson, Moerloose, and Stuchly (1997a) presented a hybrid ELF electric induction
modeling method by combining a quasistatic FDTD method with a frequency-domain
SPFD method. Dawson, Caputa, and Stuchly (1998a) used this hybrid numerical
method to compute the induced fields in an anatomical, high-resolution human body
model exposed to uniform ELF electric fields. This hybrid method was capable of
accurately computing the induced fields in a full-body human model that consisted
of 1, 736, 872 cubic voxels with 3.6-mm edges. A low-resolution model with FDTD
was used to calculate the surface charge density on the body. Later, the SPFD code
generated the surface charge distribution induced by the external electric field at high
resolution. They measured the exposure to 60 Hz fields, which can be scaled linearly to
frequencies up to 100 kHz in consideration of the frequency dependence of tissue conductivity. Dawson et al. (2001a) calculated electric fields in the human body resulting
from 60 Hz contact currents, and they compared electric fields induced in humans and
rodents (Dawson et al. 2003). The contact current occurs when a person touches conductive bodies at different potentials, creating a current flow through the body. They
used adult and child models for the calculation of contact currents. In order to estimate
the electric fields and current densities, they applied the SPFD method. Three paths of
contact current were modeled: hand to opposite hand and both feet, hand to hand only,