# A Metal Detector for Clip Location Tracking of Stomach and Colon Cancer during Laparoscopic Surgery
## 4 Experimental Results
### Animal Test and Measurement Results
The designed detector is analyzed to be 0.08 times (for stomach) and 0.12 times (for colon) faster than the detector proposed by [PERSON] et al. [13] in locating the tumor. In the course of animal experiments, using a detector to determine the position of the clip, it was found directly through the surgeon's operation. Before finding the position of the clip, the surgeon used a detector to find the position of the clip without knowing the position of the clip. At this time, the time taken to find the position of the clip using the detector was 2.21 s in the stomach and [PERSON] s in the colon. Therefore, the clip-detector in this study is better than that proposed by [PERSON] et al. [13]. If N clips are used, magnetic coupling interference may occur depending on the spacing between the clips. In other words, if the distance (\(d\)) between clips becomes longer, the magnetic field intensity is attenuated (\(\alpha\): attenuation of magnetic field intensity) by the distance (\(d^{2}\)) as shown in Equation (4), and interference can be reduced. However, if the spacing between the clips becomes narrower, the magnetic field intensity increases by the distance (\(d^{2}\)), which may lead to greater interference [23]. \[\alpha=\frac{\mathrm{FH}}{2\pi d^{2}} \tag{4}\]  
In the course of animal experiments, we attached only one clip when attaching the clip to the stomach or colon as shown in Figure 16. In addition, we use the detector to find one \begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Ref [\#]**} & \multicolumn{2}{c}{**Detection Time of Tumor [s]**} & \multirow{2}{*}{**Methods**} \\ \cline{2-2} \cline{4-4}  & **Stomach** & **Colon** & \\ \hline this work & 2.21 & 3.60 & ferrite and coil \\ [9] & 40.5 & 38.4 & RFID \\ [10] & 25.0 & - & RFID \\ [11] & - & 8.0 & magnet \\ [12] & - & 5.7 & magnet \\ [13] & 24.9 & 18.7 & open–close clip closure method \\ [14] & - & 15 to 90 & magnet \\ \hline \hline \end{tabular} foot note: # symbolizes the reference number.  
\end{table} 
Table 1: Comparison of the detection time of clip location of the designed clip-detector and others reported previously. clip position. So, there was no interference problem. However, the problem of interference between clips seems to have to be tested by increasing the number of clips. Therefore, we plan to test for interference by increasing the number of clips in the future. If there is an interference problem, we plan to solve it through additional research. Additionally, since the detector for detecting the clip is a magnetic field component induced by the coil, it has been confirmed that it does not interfere with the surrounding forceps. Finally, the method of this study is 2.27 V (5.52 mW/2.2 uT) at 11.33 kHz. That is, our method uses a magnetic field with a very weak strength, so it is analyzed that there is no adverse effect on the human body. That is, the voltage, power, and magnetic flux density generated by the detector to detect the last clip are 2.27 V, 5.52 mW, and 2.2 uT (@ 11.33-11.335 kHz), respectively. In the recommendations of ICNIRP, the republic of Korea recommends that the exposure limit of human electromagnetic waves be within the range of 3.0-150 kHz, with a voltage of 87 V or less and 5 A/m (magnetic flux density: 6.25 uT) [23; 24]. Therefore, the proposed detector is analyzed to have no adverse effect on the human body in detecting the clip. In addition, since the medical magnetic field used for human diagnosis and treatment is harmless to the human body, most studies have been conducted for the application of MRI, magnetic field therapy, capillary circulation state examination, and a capsule endoscopy diagnostic kit [25; 26; 27; 28]. Of course, if a high-density, strong pulsed magnetic field (more than 100 uT) is used (even for a short time), it stimulates the nervous system, reduces blood volume, and causes muscle pain due to muscle stiffness [24; 29; 30]. Figure 16: Method of removal and suturing after attaching the clip to the lesion site.