Effects of tissues and geometric shapes of phantoms on the specific
energy absorption rate
Biomedical Engineering Department,
College of Engineering, Imam
Abdulrahman Bin Faisal University, P.O.
Box 1982, Dammam, Saudi Arabia
Gameel Saleh, Biomedical Engineering
Department, College of Engineering,
Imam Abdulrahman Bin Faisal
University, P.O. Box 1982, Dammam,
Deanship of Scientific Research at Imam
Abdulrahman Bin Faisal University,
Grant/Award Number: 2017-268-Eng
In this article, the effects of tissues and geometric shape complexity of human body
and head phantoms on the performance of radio frequency (RF) antennas/coils are
investigated. The magnetic field, H, electric field, E, and the specific energy absorp-
tion rate SARðÞof a meander dipole RF coil are calculated. The coil has been
designed and fabricated at the University laboratory to resonate at the operating fre-
quency of 7 T magnetic resonance imaging machines. Three phantoms of different
geometries, homogeneous and inhomogeneous, are used in this work. It was noticed
that the homogeneous spherical human head phantom exhibited higher peak SAR
value (by an amount of 30%) than a homogeneous simple rectangular body model.
Similarly, the geometric shape complexity of the homogeneous SAM head phantom
played the dominant role in the accuracy of SAR results. The coil with the homoge-
neous SAM head model exhibited higher peak SAR value (by an amount of 84%)
than the homogeneous spherical head model. In contrary, the inhomogeneous multi-
layered spherical head phantom exhibited SAR value less than the single-layered
homogenous one (by 40%). The complexity of tissues, in particular, the adult skull
bone thickness, reduces the intensity of power coupled to the brain.
complexity of tissues and geometric shapes, homogeneous and inhomogeneous phantoms, magnetic reso-
nance imaging, RF coils, specific energy absorption rate
Human body and head phantoms
Computer phantoms can be simple or complex depending on
the simulator power. Homogenous phantoms consist of one
material with a specific permittivity and conductivity. Inho-
mogeneous phantoms, on the other hand, have complex tis-
sues (multilayers). Furthermore, phantoms can be modelled
with simple or complex geometric shapes.
In MRI, before doing real experiments with the human
tissues, the performance of the RF coil should be first simu-
lated and measured with homogeneous liquid phantoms.
Then, the deviation between the measured and simulated
results can be used as a measure to the uncertainty results of
the simulated voxel models. Homogeneous phantoms can be
of simple geometric shapes, such as the rectangular phantom
that emulates the body tissue and used by many research-
They can also be of complex geometric shapes, such
as the CST SAM (Specific Anthropomorphic Mannequin)
On the other hand, inhomogeneous phantoms can be
modelled as a simple geometric shape of different layers of
tissues, such as the spherical human head phantom.
can also be complex in both geometric shapes and tissues,
such as the human voxel models which emulate the human
tissues and measure SAR very accurately, but require more
resources and time during simulation.
This article discusses
how to choose a phantom that requires fewer resources and
provides an accurate performance to the RF coil. The
Int J RF Microw Comput Aided Eng. 2018;28:e21252.
2018 Wiley Periodicals, Inc.
Received: 30 October 2017
Revised: 22 January 2018
Accepted: 22 January 2018