X-raymammography, MRI, and ultrasound are someof the common techniques used for breast cancer detection. In spite of EN1 X-ray, mammography is the standard modalityclinically used for breast imaging, mammography sensitivity decreases whenimaging dense breast tissue, which is prevalent among young women. Clinicalstudies demonstrate that ultrasound can find more and smaller cancers in densebreast women, where mammography might miss them 1-2. Therefore, manyresearchers are working on automated whole-breast ultrasound scanning systems. Ultrasoundcomputed Tomography (UCT) is a potentially useful technique that has beenexplored for decades in the context of medical imaging. UCT can providequantitative images of acoustical parameters such as speed of sound,attenuation, and density from measurements of pressure fields 3.There arethree modes of acoustic imaging; transmission, reflection,and diffraction.
Transmission imaging encompasses speed of sound (SOS) waveimaging and the attenuation of those waves. Transmission imaging of the breasthas been actively studied for enhanced tumor detection and characterization4-8. Many types of reconstruction methods have been applied to the ultrasoundmedical imaging that diffraction tomography 9, transmission tomography10-12 and reflection tomography 13-15 are most common. In this papertransmission mode UCT is selected inorder to reconstruct SOS map. There are a number of approaches to reconstructimages from sets of projections. The iterative and back projection techniques16 are the two common methods, which back projection technique is most simplerin use and needs a shorter processing time compared to the iterative method, sothis method selected as the preferred method of reconstruction in this work.The filtered back projection technique is based on considering a straight pathfor ray propagation through the material.
One assumption that considered in thereconstruction was that the ultrasound wave propagated along a straight lineand was received by the corresponding receiver element on the opposite side.The UCT geometry affects the image quality parameters too, so the differentprototype systems have been established 17, 18 and researchers are investigatingthe more appropriate transducer shape array to have high-quality images 19. In this study, wehave investigated the tow transducer shape arrays, ring, and parallel shape, and have compared the image qualityparameters. At first, the models of ring-shaped and parallel-shaped systems areestablished, then the propagation of ultrasound wave in simulated systems andinteraction between waves and object are numerically simulated by COMSOLMultiphysics software (Version 5.2). After that, the set of projections isreconstructed through filter fan beam back projection by applying differentreconstruction filters.
Ultimately, image quality parameters were calculatedand the effect of filters wasinvestigated.
