# Cycle Consistent Generative Motion Artifact Correction in Coronary Computed Tomography Angiography
## 4 Results
### Clinical Data
#### 4.2.4 Qualitative Evaluation
These range from significant, where image quality substantially improves from completely unreadable to no motion, to more moderate improvements, such as reductions in apparent motion. Notably, pix2 pix and CycleGAN both significantly enhance the clarity and visibility of the coronary arteries, yet CycleGAN often outperforms pix2 pix, particularly in maintaining the integrity of the arterial structure. In Figure 9, instances where pix2 pix and CycleGAN are directly contrasted are presented. Section (a) of the figure illustrates cases where pix2 pix inadvertently enhances areas outside the targeted coronary region, as indicated by yellow arrows. Conversely, section (b) shows the samples where pix2 pix fails to rectify motion artifacts, whereas CycleGAN successfully mitigates these issues. These comparative examples underline the superior capability of CycleGAN in addressing complex motion artifacts. Figure 10 illustrates the efficacy of our proposed motion correction algorithm, especially highlighting the seamless integration of 2D-patch-based corrections back into the 3D CT volume. The upper row of the figure displays original slices from the CT volume that were previously affected by motion artifacts. Notably, these slices include the right coronary artery (RCA), a region typically susceptible to motion-induced distortions. \begin{table}
\begin{tabular}{l c c c c} \hline \hline  & **Original** & **[PERSON] et al. (2014)** & **pix2 pix** & **Proposed (CycleGAN)** & _p-Value_ \\ \hline Likert scale & & & & \textless{}0.001 \\
1 = Completely unreadable & 66.5\% & 2.5\% & 0.5\% & 0.5\% \\
2 = Significant motion & 26\% & 2.5\% & 3.5\% & 3.1\% \\
3 = Apparent motion & 6\% & 30\% & 32.1\% & 30.6\% \\
4 = Minor motion & 1.5\% & 41.5\% & 41.1\% & 39.8\% \\
5 = No motion & 0\% & 23.5\% & 22.7\% & 25.9\% \\ Score & & & & \textless{}0.001 \\ Mean & 1.43 & 3.80 & 3.82 & 3.88 \\ Standard deviation & \(\pm\)0.66 & \(\pm\)0.87 & \(\pm\)0.84 & \(\pm\)0.85 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Motion artifact before and after applying proposed method Following the application of our motion correction algorithm on these 2D patches, we reinserted them into the original 3D volume. The lower row of the figure showcases these post-correction slices. It is particularly remarkable to observe how the reinserted patches blend seamlessly with the surrounding areas, with no discernible artifacts or discontinuities. This seamless integration is further enhanced by the volumetric interpolation technique we employed, ensuring that the corrected patches maintain spatial and anatomical consistency with the adjacent uncorrected regions. The RCA region, highlighted with green boxes in both rows, serves as a clear point of comparison. In the corrected slices, one can observe a marked reduction in motion artifacts, resulting in clearer and more defined images of the coronary artery. This comparison not only validates the effectiveness of our motion correction approach but also demonstrates  
Figure 8: Qualitative examples of the original patch containing the mid-RCA, alongside the results obtained from applying pix2 pix and the proposed method, CycleGAN. These samples showcase a range of improvements, with expert evaluations based on a 5-point Likert scale (1 = completely unreadable, 2 = significant motion, 3 = apparent motion, 4 = minor motion, 5 = no motion). Additionally, source information such as case number and phase \(\phi\) in 4D CT is displayed to the left of each sample. (**a**) represents instances where the scores remained consistent between pix2 pix and the proposed method, CycleGAN, while (**b**) highlights cases where the application of the proposed method, CycleGAN, resulted in improved scores compared to pix2 pix. Figure 9: Comparative Analysis of pix2 pix and CycleGAN in coronary motion correction. (**a**) Illustrates a case where pix2 pix erroneously enhances regions outside the area of interest in the coronary artery, marked with yellow arrows to highlight the misenhanced areas.