# Computational Modeling of Ultrasound C-Scan Imaging Using Transmitted Signal Peak Density
## 4 Discussion  
In this study, the feasibility of the magnitude variation of the transmitted ultrasound signal in the frequency domain was analyzed for C-scan imaging. The magnitude variation was expressed in terms of peak density and MPVD. In a previous experimental study by [PERSON] et al., peak density was found as a promising nonconventional parameter for C-scan imaging [22]. The study documented some inefficiencies for peak density to detect the boundary of the structure in the case of high-frequency analysis. Therefore, in this study, first, the experimental result from [PERSON] et al. was imitated in the computational C-scan imaging model, which had a similar issue of boundary detection [22]. From the result, it was observed that peak density successfully generated a C-scan image of a thin pepper flake. Although peak density could not conclusively detect the flake's boundary in the pixel areas with a tiny amount of pepper flake, the issue could be avoided by proper pixel area selection. Furthermore, if a smaller pixel size can be achieved for the imaging through a smaller transducer step size, most of the pepper flakes will be automatically placed fully inside the pixel area, resulting in a better image. Even after that, there is a chance of the flake being positioned partially. However, it would be a negligible amount, and thus the boundary detection would be much better. The smaller pixel can also be achieved  
Figure 11: MPVD value at all flake positions in (**a**) Sectors 2 and (**b**) 3. Figure 10: Frequency spectrum in Sector 3 for flake positioned at (**a**) \(-\) 2 mm, (**b**) \(-\)1.5 mm, (**c**) \(-\)1 mm, (**d**) \(-\)0.5 mm, (**e**) 0 mm, (**f**) 0.5 mm, (**g**) 1 mm, (**h**) 1.5 mm, and (**i**) 2 mm. experimentally by decreasing the ultrasound beam width. We already know that a smaller beam width is better for the lateral resolution for the conventional ultrasound parameter in C-scan imaging. Therefore, it is evident that with an unconventional parameter like peak density, a smaller beam width would increase the resolution of the image. In C-scan imaging, minimal information can be gathered about the structure position along with the depth of the sample. Therefore, studies were conducted by utilizing the magnitude variation to see the feasibility of achieving any information about the structure location. The cylindrical pepper flake was moved along the depth of the phantom for this study, and magnitude variation was evaluated in terms of peak density for all locations. It was observed that peak density was not able to capture the change in the spectrum properly, as peaks and valleys were changing their magnitude level, resulting in similar peak densities for different positions. Thus, peak density could not establish any relationship with structure position. Therefore, the MPVD parameter was used to express the magnitude variation. MPVD perfectly captured the magnitude change of peaks and valleys. With gradually positioning the flake from the middle to the bottom of the phantom as well as to the transducer, the MPVD value showed a strong increasing trend. Therefore, the MPVD value can give us information about the structure location while creating C-scan images. To have more accurate information, only the significant peak and valley magnitude can be observed. It is expected that with different shapes of the structures, significant peaks and valleys will be created at different frequency steps. It can also create a different pattern of the signal. Thus, by analyzing the signal pattern more information can be gathered regarding the shape of the structure without imaging the sample. In the medical sector, this C-scan imaging technique can be used to image tissue heterogeneity. To detect cancerous margins during breast-conserving therapy (BCT), it can be used to identify positive/negative margins instantly. The main challenge of using high-frequency ultrasound in C-scan imaging would be its increasing attenuation rate, which limits this application to a low thickness level.