## 4 Discussion
In clinical practice, during the treatment of tumors such as breast cancer, an absorber is used to determine the location of the tumor, and its location is tattoed with metal ink, or a metal capsule made of titanium is inserted into the body using a needle [46; 47; 48]. This can be confirmed as a metal artifact on X-ray, CT, MRI, and US images; however, because this is an invasive method, the side effects must be considered [46; 49]. However, if the location is confirmed with a US image obtained using a non-invasively attached PU, radiation exposure can be reduced. Additionally, the PU can identify the attached area in the US image, which can help track the location of the tumor. Therefore, polyurethane is expected to be used for various purposes, including its role as an existing marker in various diagnostic and imaging studies, by controlling the signal intensity. PU can act as an absorptive marker, reducing the signal intensity of the ROI and creating a hypecohica area. This is a different characteristic from metallic absorbers, which display an anechoic signal. This means that the brightness of the area of interest where the PU absorber is attached can be also corrected through parameter adjustment, providing the optimal image for diagnosis without any additional change in US intensity. In particular, when attaching a PU absorber, the muscle signal is greatly reduced compared to the fascia signal, so it is possible to obtain images with the fascia further emphasized through adjusting parameters such as TGC or gain. In addition, diagnosis is often delayed because additional time is required when the original image is post-processed. However, in the case of PU absorbers, it is expected that rapid diagnosis will be possible because it can be confirmed through imaging at the same time as scanning without any additional post-processing. If a method for emphasizing signals in these specific areas is implemented with embedded software and real-time post-processing technology is developed, not only will fast and efficient diagnosis be possible, but various ultrasound technologies can be designed. However, this study had some limitations. First, this study did not provide information on absorbers made from various materials. Second, it was limited to evaluating the fascia and muscles of the abdominal area. Thirdly, this study only checked the B-mode scan; thus, its applicability to other scanning methods could not be evaluated. Finally, this study was conducted only on young men, because men who are less sensitive to abdominal exposure may be of higher interest. Therefore, in future studies, various absorptive materials should be used, and the image quality should be quantitatively evaluated according to the material. In addition, the applicability of the absorber to other genders, age groups, and body parts, as well as the applicability to clinical surgeries such as needle guidance, must be ensured. In conclusion, this study assessed the new role of a PU on the RA during US imaging. The results proved that the absorber may facilitate easy observation of the fascia and muscles. The results of this study may serve as the basis for developing diagnostic methods and absorbers that can help diagnose facial diseases. Conceptualization, Y.-B.L. and C.-K.K. ; methodology, Y.-B.L. and C.-K.K. ; software, S.-J.A. and C.-S.P. ; validation, Y.-B.L. and C.-K.K. ; formal analysis, S.-J.A. and C.-S.P. ; investigation, S.-J.A. and C.-S.P. ; resources, Y.-B.L. and C.-K.K. ; data curation, Y.-B.L. and C.-K.K. ; writing--original draft preparation, S.-J.A. and C.-S.P. ; writing--review and editing, Y.-B.L. and C.-K.K. ; visualization, S.-J.A. and C.-S.P. ; supervision, Y.-B.L. and C.-K.K. ; project administration, Y.-B.L. and C.-K.K. ; funding acquisition, Y.-B.L. and C.-K.K. All authors have read and agreed to the published version of the manuscript. This research was supported by grants from the National Research Foundation of the Republic of Korea (NRF) grant funded by the Korean government (MSIT) (No. 2020R1A2C1004355; No.