In this study, the investigators used the optical flow method to measure the colonoscopy withdrawal speed, and doctors were selected from multiple hospitals to collect prospective colonoscopy screening videos, and the percentage of colonoscopy withdrawal overspeed was calculated to explore the relationship between it based on optical flow method and the adenoma detection rate.

Study showed that adequate withdrawal time is an important prerequisite for full mucosal inspection. In a large population-based analysis, a 1-min increase in withdrawal time led to a 3.6% increase in the ADR. Protocols or expert consensus recommend a standard withdrawal time of 6 min or longer. However, Findings of studies showed that a number of colonoscopies had a withdrawal time less than 6 min, which greatly reduces the ADR.

Investigator's preliminary experiments have shown that deep learning can monitor the colonoscopy withdrawal time in real-time and improve the adenoma detection rate. Based on the above rich foundation of preliminary work and the massive demand for improving the colonoscopy withdrawal assessment system.

The investigators improved EndoAngel to use optical flow method to monitor the colonoscopy withdrawal speed. The performance of the EndoAngel system was verified in colonoscopy videos. The investigators then aimed to evaluate whether the EndoAngel system could improve polyp detection rate after restricting the colonoscopy withdrawal speed.

Inclusion Criteria:

1. Male or female ≥18 years old;
2. Able to read, understand and sign an informed consent;
3. The investigator believes that the subjects can understand the process of the clinical study, are willing and able to complete all study procedures and follow-up visits, and cooperate with the study procedures;
4. Patients requiring screening colonoscopy.

Exclusion Criteria:

1. Have drug or alcohol abuse or mental disorder in the last 5 years;
2. Pregnant or lactating women;
3. Patients with known multiple polyp syndrome;
4. patients with known inflammatory bowel disease;
5. known intestinal stenosis or space-occupying tumor;
6. known colon obstruction or perforation;
7. patients with a history of colorectal surgery;
8. Patients with a previous history of allergy to pre-used spasmolysis;
9. Unable to perform biopsy and polyp removal due to coagulation disorders or oral anticoagulants;
10. High-risk diseases or other special conditions that the investigator considers the subject unsuitable for participation in the clinical trial.

In this study, endoscopists who completed at least 140 colonoscopies were selected as the research objects, and patients who met the criteria were included in the experiment.