X-ray
mammography, MRI, and ultrasound are some
of the common techniques used for breast cancer detection. In spite of EN1 X-ray, mammography is the standard modality
clinically used for breast imaging, mammography sensitivity decreases when
imaging dense breast tissue, which is prevalent among young women. Clinical
studies demonstrate that ultrasound can find more and smaller cancers in dense
breast women, where mammography might miss them 1-2. Therefore, many
researchers are working on automated whole-breast ultrasound scanning systems. Ultrasound
computed Tomography (UCT) is a potentially useful technique that has been
explored for decades in the context of medical imaging. UCT can provide
quantitative images of acoustical parameters such as speed of sound,
attenuation, and density from measurements of pressure fields 3.

There are
three modes of acoustic imaging; transmission, reflection,
and diffraction. Transmission imaging encompasses speed of sound (SOS) wave
imaging and the attenuation of those waves. Transmission imaging of the breast
has been actively studied for enhanced tumor detection and characterization
4-8. Many types of reconstruction methods have been applied to the ultrasound
medical imaging that diffraction tomography 9, transmission tomography
10-12 and reflection tomography 13-15 are most common. In this paper
transmission mode UCT is selected in
order to reconstruct SOS map. There are a number of approaches to reconstruct
images from sets of projections. The iterative and back projection techniques
16 are the two common methods, which back projection technique is most simpler
in use and needs a shorter processing time compared to the iterative method, so
this method selected as the preferred method of reconstruction in this work.
The filtered back projection technique is based on considering a straight path
for ray propagation through the material. One assumption that considered in the
reconstruction was that the ultrasound wave propagated along a straight line
and was received by the corresponding receiver element on the opposite side.
The UCT geometry affects the image quality parameters too, so the different
prototype systems have been established 17, 18 and researchers are investigating
the more appropriate transducer shape array to have high-quality images 19.

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In this study, we
have investigated the tow transducer shape arrays, ring, and parallel shape, and have compared the image quality
parameters. At first, the models of ring-shaped and parallel-shaped systems are
established, then the propagation of ultrasound wave in simulated systems and
interaction between waves and object are numerically simulated by COMSOL
Multiphysics software (Version 5.2). After that, the set of projections is
reconstructed through filter fan beam back projection by applying different
reconstruction filters. Ultimately, image quality parameters were calculated
and the effect of filters was
investigated.