## 3 Results  
In this study, MRI scans were performed in order to prove the validity of the fabricated phantom and to confirm that the fat content was properly distributed (Figure 2). T1-weighted images (Figure 2b) become brighter as fat content increases. By contrast, T1-weighted images with fat-suppression (Figure 2c) become darker with increasing fat content. Figure 3: Experimental setup for the ultrasound imaging of the emulsion gel phantom using a modular frame. (**a**) LEGO-compatible modular frame. (**b**) It consists of an open frame so that it is easy to insert a phantom and scan images from multiple directions. (**c**) In order to increase reproducibility, an ultrasound image was obtained by fixing the transducer with a LEGO block. (**d**) The phantom was rotated clockwise and scanned. By combining fat-mimicking material into a LEGO-compatible module frame, the phantom was built with an open frame, allowing for scans from all directions, and for multiple perspectives (Figure 3). Figure 4 shows the images obtained by arranging the verified phantoms side-by-side on the module frame and then scanning them with ultrasound. The black dotted line shows the direction in which the ultrasound beam is transmitted (Figure 4a). Brightness increased when the fat content was 40% and 80% than when the fat content was 0% (Figure 4b). Additionally, in the plot profile analysis, it can be seen that the gradient of the straight line becomes steeper as fat content increases, and attenuation occurs more often. The yellow dotted line is the line profile, which was set laterally to avoid posterior acoustic enhancement artifacts in the center. Figure 5 explains the attenuation. When the ultrasonic beam transmitted a high fat content of 80% (Figure 5d), the beam attenuation was increased more than in the lower fat content or the 0% fat content (Figure 5b). Therefore, the visibility of the rectangular part decreased more in Figure 5d than in Figure 5b. Figure 4: Intensity attenuation by fat content. (**a**) The gel phantom was inserted into the module, and the ultrasound beam was transmitted in the direction of the black dotted line. (**b**) The corresponding ultrasound image. (**c**) Line profiles in each phantom with the yellow dotted line showing the line profile. The line profile is set to the lateral side to avoid the central region artifact (acoustic enhancement). Figure 6 shows that the characteristics shown in the image are significantly different depending on which materials were injected into the round, square, and triangular shapes. In Figure 6, the white arrows indicate posterior acoustic enhancement. Figure 6a was injected with water. It showed relatively lower attenuation than the surrounding materials, and posterior acoustic enhancement characteristics were visible. On the other hand, oil exhibited relatively higher attenuation than the surrounding materials due to its absorbing properties of sound waves, as shown in Figure 6b. Since this difference in acoustic impedance increases reflection and decreases transmission, the beam barely reaches the back of the structure. This characteristic is known as the posterior acoustic shadow and can be seen in the oil below. Figure 7 compared the echo characteristics by injecting water, oil, and the emulsified substance, which is a mixture of water and oil, into a circular shape part. Water and oil showed no echo [21], but the emulsified substances appeared hyperechoic since the water and oil mixed in emulsified substances increase the internal interface [22]. The hyperechoic signal is received by the transducer because more scattering is generated compared with the surrounding tissue. This shows that emulsions, as diffuse reflectors, cause the ultrasound waves to scatter. Figure 5: Image degradation by fat content. The black box shows the region of interest on the image. Ultrasound images (**b**,**d**) are the images corresponding to phantoms (**a**,**c**).