# A Metal Detector for Clip Location Tracking of Stomach and Colon Cancer during Laparoscopic Surgery
## 4 Experimental Results
### Animal Test and Measurement Results  
To test the performance of the designed clip-detector, we conducted animal experiments. The animal was tested at the experimental animal center of KNOTUS (Songdo Research Center, Incheon, Republic of Korea). We obtained institutional review board (IRB) permission from the animal ethics commission (KNOTUS-IACUC-20-KE617). In the animal test, a male farm mini pig (1 ea) weighing 40 kg was used. For animal experiments, the clip-detector installed four clips in the visceral: middle circular muscle layer of the stomach; and eccentric: sigmoid colon using an endoscope or a colonoscope, as shown in Figure 13.  
As shown in Figure 14, we checked whether the clip was installed correctly by the endoscope on an external monitor and prepared for laparoscopic surgery. Figure 12: Simulation result of the metal (clip) detected using pulse signal. Figure 13: Process of clip installation in mucosa in stomach and colon using endoscope and colonoscope, respectively. After installing the clip by endoscopy, we tested the detection performance of the clip in laparoscopic surgery, as shown in Figure 15a. The detector was inserted into the abdominal cavity through the trocar, and the detector started to detect the clip in the cavity as shown in Figure 15b. When the clip existing in the stomach (visceral) and the colon (circular folds) was detected, the detector generated an amplitude of 2.27 V (@ 11.33 kHz, output power of 5.52 mW), as shown in Figure 15c, and an alarm was generated from the speaker. Upon encountering the clip, the detector is coupled to the clip; the detection time was 1.12 s and 1.20 s (investigation time of 2.21 s and 3.6 s). Here, 1.12 s and 1.20 s are the detection times when the detector is coupled with the clip in the stomach and colon, and 2.21 s and 3.6 s are the time consumed to determine the clip position of the stomach and colon in the cavity. It can be confirmed that there is no time delay and that the response time for detecting a tumor is exceedingly short. Figure 14: Clip set installed in the mucosa of colon and stomach using colonoscope and endoscope, respectively. Figure 15: Animal test of the developed clip-detector: (**a**) laparoscope surgery (**b**) clip detection (**c**) clip detected signal. The thickness of the gastric mucosa between the clip and the detector is mostly 2 cm, and the colon is 1 cm. The detector was separated by a distance of 0.5 cm from the parietal peritoneum above. Furthermore, in the colon, the detector was approximately 0.5 cm away from the ecum. Therefore, the distance at which the detector detects the clip is at the level of 2.5 cm (top) and 1.5 cm (colon). After the designed detector is docked to the trocar and inserted into the cavity, the time it takes for the clip-detector to determine the tumor location of the stomach and colon is recorded as 2.21 s and 3.6 s, respectively. In addition, the module for detecting the tumor location is inserted into the clip as shown in [9; 10; 13], and is designed to be integrated. Connection of the detection module to the clip without using a wire is advantageous[PERSON] Therefore, the error in the determination of the clip position is minimized. Following the same logic, there will be an error equivalent to the wire length in the position of the clip with wire [11; 12; 14]. However, because the designed clip can be directly connected, the error in the clip position determination can be reduced. In addition, the proposed clip-detector has the ability of determining the tumor location for both the stomach and colon, as in [9; 13]. In the studies conducted by [PERSON] et al. and [PERSON] et al. [9; 13], the clip positions were determined for both the stomach and colon simultaneously. Nonetheless, it is highly important that the clip-detector be capable of locating the tumor accurately and speedily. Table 1 compares the tumor detection capability of the previously studied detector and the designed detector, and the time it consumes to locate the tumor.