Introduction: capsule robot is a promising endoscopic method for gastrointestinal diagnosis because it can greatly reduce patient discomfort. Most capsule robots are only used to obtain image information and lack the ability to collect samples. In the latest study, a research team from Tianjin University developed a biopsy capsule robot with a novel sampling strategy. The size of the sample collected meets clinical requirements. It may be used to replace colonoscopy for in the future!
At present, colorectal cancer has become the third most common malignant tumor and the second most deadly cancer in the world. In 2020, the number of colorectal cancer cases reached 1.9 million, resulting in 900,000 deaths. The survival rate of stage I colorectal cancer reaches 90%, while the survival rate of stage V colorectal cancer is only 10%. Therefore, early diagnosis can significantly reduce the mortality rate. Moreover, colorectal cancer is largely preventable by adjusting alterable risk factors and detecting and removing precancerous lesions , and long-term screening can significantly reduce the incidence and death of colorectal cancer. In this way, efficient and accurate screening tools are urgently needed. Compared with colonoscopy, capsule robot (Capsulerobot, CR) can reduce patient discomfort and achieve efficient examination results, which is the best diagnosis method.
The diagnosis of colorectal cancer mainly relies on flexible and slender endoscopes with image acquisition system to perform endoscopy examination of the colon, but patients need to endure discomfort and bear certain risks. In recent years, CR has become a replacement for traditional endoscopes, greatly reducing the pain and mental stress of patients. Recently, a research team from Tianjin University developed a new biopsy capsule robot (BCRs) based on high-speed cutting tissue, which can achieve effective and reliable sampling of . The study was published on Cyborg and Bionic Systems as "A Novel Biopsy Capsule Robot Based on High-Speed Cutting Tissue".
Figure 1 Research results (Photo source: [1]) The movement of typical CRs in
is passive, which means it depends entirely on the peristalsis of the colon. Because of this, the lesions may be missed. To this end, some scientific researchers have developed an active locomotive CR, whose trajectory can be modulated through an external magnetic field or an internal actuator to achieve a more thorough exploration of colon . The position and attitude of the CR of the active locomotive can be well controlled by the external magnetic field, and the image can be transmitted from the CR to the external receiver for real-time monitoring through the radio frequency transmitting circuit. However, imaging is not enough to diagnose, and a suspected lesions require biopsy , while CR cannot perform biopsy. This is where BCR comes in.
During the design process of the new BCR, researchers proposed a new sampling strategy in which sharp blades rotate at high speed to cut suspicious areas of the colon while using a compressed coil spring to power the blades, and a Bowden cable mechanism was used to monitor tension in the cable in real time. Accordingly, a BCR system was designed to implement these functions.
Figure 2 Structural diagram of BCR (Source: [1])
To verify the feasibility of this scheme, the researchers designed and produced a BCR prototype. The influence of tool speed on cutting torque, the torque required to cut soft tissue on the tool axis cannot be ignored. Through experiments, the researchers obtained the relationship between cutting torque and tool speed, and finally found that the faster the motor speed, the smaller the cutting torque. Therefore, the high-speed cutting method adopted in this study can effectively reduce the cutting torque .
In addition, the researchers also conducted an experiment to fix the motor speed to 9.81 rad/s and adjust the contact force between the capsule and soft tissue. The greater the force between the capsule and soft tissue, the greater the required cutting torque. The maximum cutting torque of 20.45 N·mm corresponds to the highest contact force tested, as more tissue is squeezed into the cutting area, which means that larger tissue samples can be obtained. That is to say, determined the effect of speed on cutting torque through these experiments, and the results showed that high-speed cutting can effectively perform biopsy of low cutting torque .
Figure 3 BCR prototype designed and produced by researchers (Figure source: [1])
Next, through high-speed cutting performance experiments, confirmed that this design can effectively use high-speed cutting to achieve tissue sampling, further proving the feasibility of the high-speed soft tissue cutting scheme in this study . In the design of this BCR, the self-reset trigger and coil spring facilitate multiple biopsies. In order to test this, the researchers used the high-speed camera to record the rotation speed of the spring and found that BCR can achieve 3 consecutive biopsies of .
In addition, during the sampling process, BCR is required to remove soft tissue while avoiding tissue tearing. For this reason, the researchers set different cutter speeds to study soft tissue tearing on the basis of high-speed cutting experimental research. As the tool speed changes, researchers found that when the cutting speed of the tool is 1.05 rad/ms, soft tissue can be effectively sampled to achieve biopsy .
Finally, to verify the biopsy performance of the designed BCR, the researchers used pig large intestine for in vitro tests, and finally confirmed that this cutting method can collect enough suspicious tissue to meet the requirements of clinical biopsy.
In summary, the sampling strategy proposed in this study is effective, and the sample size collected through this method is sufficient to meet clinical requirements. I believe that with the further development of technology, this biopsy capsule robot can effectively replace the current colonoscopy, which will greatly reduce the discomfort and mental stress of patients during colonoscopy.
Written by | Muzijiu
Typeline | Wensheng
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Reference materials:
[1]Zhibin Song, Wenjie Zhang, Wenhui Zhang, et al. A Novel Biopsy Capsule Robot Based on High-Speed Cutting Tissue. Cyborg and Bionic Systems, vol. 2022, Article ID 9783517, 11 pages, 2022. https://doi.org/10.34133/2022/9783517
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