## 3 Results and Discussion
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Position** & **Evaluation Parameter** & **Group 1** & **Group 2** & **Group 3** & **Group 4** \\ \hline \multirow{4}{*}{Aortic arch} & CNR & 56.49 & 64.86 & 13.79 & 56.25 \\  & ERD & 2.77 & 2.71 & 2.61 & 2.53 \\  & BRISQUE & 36.87 & 38.58 & 32.45 & 35.10 \\  & CNR & 28.58 & 32.34 & 8.57 & 49.33 \\  & ERD & 1.28 & 1.20 & 0.11 & 0.10 \\  & BRISQUE & 35.59 & 37.93 & 31.73 & 35.58 \\  & CNR & 24.85 & 28.40 & 6.45 & 28.94 \\ End of heart & ERD & 2.02 & 1.95 & 0.11 & 0.95 \\  & BRISQUE & 37.81 & 39.91 & 33.79 & 35.01 \\  & CNR & 36.64 & 41.87 & 9.60 & 44.84 \\ Average & ERD & 2.02 & 1.96 & 0.94 & 1.19 \\  & BRISQUE & 36.76 & 38.80 & 32.66 & 35.23 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Quantitative evaluation results as function of Group. The results of the BRISQUE evaluation are shown in Figure 6. In the aortic arch, values of 36.87 Group 1, 38.58 Group 2, 32.45 Group 3, and 35.10, Group 4 were derived in groups 1, 2, and 3, with group 3 showing the best value. Among the four chambers, Group 3 showed the most improved value at approximately 31.73, while Group 2 showed the highest value at approximately 37.93. At the end of the heart, improved results were obtained in the following order: Groups 3, 4, 1, and 2. Similar to Group 3, Group 4 showed improved results of approximately 35.23. As a result of the BRISQUE evaluation, there was variation depending on the slice; the best value was obtained in Group 3, based on ADMIRE strength A2 and kernel B59, with an average of approximately 32.66. Recently, various studies have been conducted to reduce excessive radiation doses generated during the acquisition of computed tomography (CT) images. Among these, the application of additional filters is considered a hardware method. The additional filter reduces the radiation dose by removing unnecessary X-ray wavelengths reaching  
Figure 5: Results of edge rise distance (ERD) for reconstructed CT images of aortic arch, 4 chamber, and end of heart areas. Figure 6: Results of blind/referenceless image spatial quality evaluator (BRISQUE) for reconstructed CT images of aortic arch, 4 chamber, and end of heart areas. the patient. Tin filters have the advantage of being able to further reduce noise compared to other additional filters, such as aluminum or copper filters that were previously used. However, tin filters cannot completely solve the noise problem because the process of removing scattered rays involves a decrease in the number of photons [9]. To solve this problem, additional technologies, including annotation filters, must be applied. For this purpose, a software approach using image-processing techniques can be considered. Among the image-processing techniques, ADMIRE is one of the techniques applied clinically; it can improve the signal-to-noise ratio (SNR) by repeatedly processing data during low-dose CT imaging. As a feature of ADMIRE, noise removal performance improves when the intensity is increased. However, because reconstruction takes a long time, an appropriate intensity must be set according to the purpose of the CT examination. In addition, the higher the kernel, another CT parameter, is set, the lower is the smoothing strength; this reduces the degree of noise removal but has the advantage of minimizing damage to the boundary information. However, to remove a large amount of generated noise, the kernel value must be set to a low value. A low kernel value increases smoothing strength and damages boundary information. Therefore, the application of additional software that can effectively remove noise while preserving boundary information is required. The NLM algorithm is a CT image post-processing technique that removes noise by reflecting the distance-weighted similarity of the image. When applying existing algorithms, the problems of low noise removal efficiency and low sharpness of the boundary area can be solved [13; 14].