Reducing Dielectric Artifacts in 3T MRI: A Comprehensive Review

This report delves into the phenomenon of dielectric artifacts in Magnetic Resonance Imaging (MRI), particularly focusing on their occurrence in 3T scanners. It defines dielectric artifacts, which compromise image quality and can be mistaken for pathologies, and explores their causes, including radiofrequency shortening. The report highlights the prominence of these artifacts around metal objects and implants and discusses the impact of field strength. It examines reduction methods such as using dielectric pads, spin echo sequences, and shorter echo times. The report reviews primary research findings on dielectric artifacts and their impact on MRI image quality. The study concludes that while dielectric artifacts can improve image quality, healthcare professionals should be aware of the potential for image degradation, especially in the presence of metal implants. The report emphasizes the importance of following established guidelines for safe and secure use of MRI scanners.

MAGNETIC
RESONANCE
IMAGING

Contents
INTRODUCTION...........................................................................................................................3
QUESTION 2..................................................................................................................................3
What is Dielectric artifact and how it can be reduced in routine examination............................3
Causes of Dielectric electric artifact............................................................................................4
Is it most prominent at 3T?..........................................................................................................5
Any primary research that has demonstrated this?......................................................................5
Findings of study.........................................................................................................................5
Reduction methods......................................................................................................................5
CONCLUSION................................................................................................................................5
REFERENCES................................................................................................................................6

INTRODUCTION
Magnetic resonance imaging is the type of method through which help to study the internal
process of the body by scanning the images depicting the internal body movement in order to
diagnose any disease and also check whether any individual is healthy or not. MRI Scanners are
used in the hospitals as an equipment to understand all the process of any living organism. The
machine uses the very strong magnetic field which help to produce the images of the internal
body. Due to the increase in the number of cases from the diagnosis from traditional x-ray
machine it was found that the UV rays damage the cells of the body and can also disturb the
body functions and create some diseases in the body. The MRI used the nuclear waves
technology to encounter the after effects like X-rays. The machine was also very effective in
diagnosing all the critical parts of the body, like brain, heart, lungs, and all other parts in the
body.
QUESTION 2
What is Dielectric artifact and how it can be reduced in routine examination
Dielectric effect artifact is can be defined as an MRI artifact which can be seen on the body
of 3T MRI machines. It has also been analysed that some artifacts also affects the quality of
images which is being produced by MRI while other do not affect the diagnostic quality but may
be confused with pathology. Dielectric effects are produced when matter interacts with
components that are electric and these components are of RF- field. When there is an increase in
field strength of an MRI unit, radiofrequency wavelength which can be seen in tissue it decreases
(Espy, 2015). It can be considered as a limitation of higher field system of MRI. In order to
improve the effect of Dielectric artifact, it has been advised to health care professional to bring
down service user to a lower field system. dielectric effects and associated artifacts are
progressively important as field strength increases, although a simplistic model of dielectric-
induced standing waves may only explain a small part of the phenomenon. To reduce the effect
of Dielectric artifacts in 3T scanners, health care unit can make use of Dielectric pads. They are
small pouches who have high charged conductive materials, this equipment is kept between
service user and receiver coil so that it reduces effect of dielectric artifact. The Dielectric pads
contains small amount of metal that is Barium and Calcium which is kept in water that is
protonated. These pads do not make use of RF which is dual transmit at 3T so that it reduces
effect of Dielectric artifacts significantly. Also it has been analyzed in a recent report that

flexible dielectric pads has been used in various health care units from past so many years. It has
also been interpreted that the effect of Dielectric artifact is tremendous at 3T than 1.5T. Also to
reduce effect of Dielectric artifact during routine examination an MRI unit which have lower
filed strength can be utilized by various health care units. To excite hydrogen at 1.5T it has been
analyzed that 42.6MHz frequency is being used while at 3T 63.9MHz frequency is used to excite
hydrogen.
Causes of Dielectric electric artifact
Dielectric artifacts are being caused by radio frequency shortening. These have huge impact
on higher field in comparison to lower field. The Dielectric effect can be on the area which has
low signal intensity on image that has been produced by MRI scanners. The effect of artifact can
be seen at all field strength but it has been analysed that higher effect can be seen at higher field
strength (Sun and et.al., 2017). The only improvement which can be done to reduce effect of
Dielectric artifact is that the image must be switch to a frequency less than <3.0 T system. Also
Dielectric heaters can be used and utilized for in enhancing sensitivity and reducing effect of
sample heating. Also these artifacts can lay impact on health conditions of service users as image
produced during routine examination can be of low quality that can hamper individual’s health.
MRI has become one of the most important tool that has been used in various clinical settings. In
order to provide and generate higher quality image there might be chances that clinical settings
make use of Dielectric artifacts which can hamper the health conditions of service users
(Kharrat, Halima and Ayed, 2015). To reduce effect of Dielectric artifacts flexible dielectric pads
are being used in recent times, these pads which are being used can also be fabricated. It can be
used efficiently in 3T scanners. These pads have improved image quality which is being
produced by MR. These Dielectric artifacts are not immune to High field MRI. Strength of MRI
is being measured in fields and these are not being immune to artifacts. It has also been analysed
that High field MRI is being used as it produces clear image in which every small part of body
can be seen. So acute diagnosis can be done with the help of high field MRI.
Artifacts can also be related to metal that can be reduced to by using techniques that are less
dependent on high magnetic field uniformity. Spin echo or fast spin echo techniques and
methods can be used. Quality can be reduced by susceptibility artifacts. Passive Dielectrically
materials can also be used by clinical setting to improve quality of image which is being

produced by 3T scanners. It also affects distribution of radio frequency electromagnetic fields.
The use of this has been increased by High filed MRI scanners and specially 3T scanners.
Is it most prominent at 3T?
Dielectric artifacts are prominent around metal objects and implants. It has been analysed
that susceptibility artifacts have more worsening effect at higher fields. In health care unit, health
care professional must make sure that scanning of service user using these artifacts must be
avoided by them, as this can hamper their health aspects. Also patients with metal implants must
not be diagnosed with susceptibility artifacts at 3.0T (Lønning and et.al., 2019). Dielectric
artifacts can be changed in shape but should not be cut out by changing direction of frequency
and phase encoding. Shorter TE values can be used to minimised the effects that is being
produced by Dielectric artifacts. These artifacts can also be reduced by increasing the strength of
gradient for a given field of view and also the use of narrow bandwidth techniques must not be
used. Thinner slices can also be used; it can also assist like parallel imaging techniques does. It is
prominent in and around metal objects.
Any primary research that has demonstrated this?
Yes, primary research has been made related to dielectric effect artifacts. The study which
happened was related to reason and cause of these artifacts and also to find out solutions to these
causes (Hanna and et.al., 2019). The study in this includes patients who have been referred to
MRI examination for any particular disease. This study was performed by trained MRI
technologist under nay expertise radiologist. MR images which were being acquired in study was
taken so that reason and causes of these artifacts can be known. Deep research related to this
topic was being done (Artifacts in Magnetic Resonance Imaging, 2015).
Findings of study
A total of 209 services users in which 95 females and 114 males was being referred to the
department of MRI. Most common artifact which being shown was Dielectric artifact. Remedial
measures need to be taken so that MRI imaging can be improved. Also optimization of MRI
imaging is being done in the study (Lønning and et.al., 2018).
Reduction methods
The best reduction method that can be used to reduce effect of dielectric artifact that is
being caused by metallic body which are foreignic is to make use of spin echo sequences with a

short echo sign. Excessive artifacts make it very difficult, and sometimes impossible, to
recognize an important intracerebral pathology
CONCLUSION
From the above study, it has been summarized that dielectric artifacts at 3T scanner must not
be used as it produces high amount of frequency that can hamper individual’s health. But by
using these artifacts it has been analyzed that image quality of MR scanner is being improved.
Even small parts in body can be seen by these artifacts. Die electric artifacts are being prominent
around metal. These can produce worsening effect to body at high field strength. various national
and international guidelines have been published on safe and secure use of MRI scanners. It has
also been analysed in report that general public must be restricted to area MR environment so
that they can maintain quality of MRI scanners. Report has also analyzed that Phantom protocols
have been used to maintain image quality of MRI scanners. Euro spin were being used to analyze
performance characteristics of MRI scanners.

REFERENCES
Books and Journals
Espy, M., 2015. Portable MRI developed at Los Alamos. LANL (Los Alamos National
Laboratory (LANL), Los Alamos, NM (United Stat
Hanna, K.F. and et.al., 2019, October. 368. Incidental Findings on Brain MRI in People Living
with HIV. In Open Forum Infectious Diseases (Vol. 6).
Kharrat, A., Halima, M.B. and Ayed, M.B., 2015, December. MRI brain tumor classification
using support vector machines and meta-heuristic method. In 2015 15th International
Conference on Intelligent Systems Design and Applications (ISDA) (pp. 446-451). IEEE.
Lønning, K. and et.al., 2018. Recurrent inference machines for accelerated mri reconstruction.
Lønning, K. and et.al., 2019. Recurrent inference machines for reconstructing heterogeneous
MRI data. Medical image analysis.53. pp.64-78.
Sun, Y. and et.al., 2017. Predicting prostate tumour location from multiparametric MRI using
Gaussian kernel support vector machines: a preliminary study. Australasian physical &
engineering sciences in medicine.40(1). pp.39-49.
Online
Artifacts in Magnetic Resonance Imaging. 2015. [online] Available through : <
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4340093/>

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