Endoscopic submucosal dissection (ESD) is a technique that allows curative treatment of early gastrointestinal neoplasia with organ preservation. However, it is a technically demanding procedure. Tissue traction plays a vital role in facilitating the visualization of the cutting line and the submucosal vessels, which usually only relies on the hood attached to the tip of the endoscope. However, when dealing with flat or large lesions, the absence of reliable traction in ESD contributes to its technical complexity and prolongs procedure duration. Various traction devices and techniques have been developed to provide tension for the dissection plane and optimal visibility during ESD. Most of these only provide static traction from a fixed angle, thus the effect of traction diminishes when the dissection continues.

In contrast to the aforementioned traction methods, magnetic traction offers the ability to externally manipulate an internal magnetic retractor, simplifying the internal workspace. The proposed magnetic retractor is composed of a detachable clip from an hemoclip is affixed to a magnetic element. By adjusting the position of the external magnetic source, the magnetic retractor automatically couples and aligns with it, enabling simultaneous dynamic directional control during the ongoing ESD operation. A novel robotic magnetic countertraction system was developed (MAG-ESD). The system consists of two sections: an external permanent magnetic source and the disposable magnetic retractor. The external permanent magnetic source is composed by a large external permanent magnet (EPM) which held by robot arm to externally control the locomotion of the magnetic retractor within patient. The disposable magnetic retractor is a consumable surgical instrument that modified from a commercial hemoclip, which has small magnets hangs on the clip legs. The design of the disposable magnetic retractor eliminates the need for endoscope withdrawal which can be inserted through the instrument channel from the handle during ESD operations, like other common instruments. In the current pilot study, the novel MAG-ESD counetrtraction system would be tested in 20 patients who undergo gastric and colonic ESD, with the aim of evaluating the system efficacy and safety.

Gastrointestinal (GI) cancers accounted for 39.5 million new cases worldwide in 2020, representing 14.7% of the total new cases of cancer. These cancers also led to 18.8 million deaths, constituting 19% of the total deaths caused by cancer. Typically, endoscopic resection is recommended for early-stage tumors within the GI tract, with endoscopic submucosal dissection (ESD) often utilized for submucosal resection. Tissue traction plays a vital role in facilitating the visualization of the cutting line and the submucosal vessels. However, when dealing with flat or large lesions, the absence of reliable traction in ESD contributes to its technical complexity and prolongs procedure duration.

Various traction devices and techniques have been developed to provide tension for the dissection plane and optimal visibility during ESD. Examples include the "S-O clip" , "Ring thread", "Multiloop", "Double clip and rubber band" , etc. These methods typically involve the deployment of two or more clips to secure both the lesion site and the organ wall. The clips are constrained by springs or strings, allowing for control of the traction direction by deploying new clips to anchor the device at different locations. There is often a need to introduce a new clip through the instrument channel when adjusting the traction direction after the initial clips are anchored. Additional clips must be deployed to manipulate tissue traction, further complicates the internal working space, and inhibits the camera's peripheral vision. The traction achieved is not dynamic. Another drawback is that the traction force weakens during ongoing resection due to the elastic nature of the materials used, especially when the distance between the anchored clips decreases.

In contrast to the aforementioned traction methods, magnetic traction offers the ability to externally manipulate an internal magnetic retractor, simplifying the internal workspace. The proposed magnetic retractor is composed of a detachable clip from an hemoclip is affixed to a magnetic element. By adjusting the position of the external magnetic source, the magnetic retractor automatically couples and aligns with it, enabling simultaneous dynamic directional control during the ongoing ESD operation. Previous research has explored various designs of the magnetic element and external magnetic source. While many magnetic traction methods require withdrawing the endoscope to prepare the deployment of magnetic retractor.

Hence, a novel robotic magnetic countertraction system was developed (MAG-ESD). The system consists of two sections: an external permanent magnetic source and the disposable magnetic retractor. The external permanent magnetic source is composed by a large external permanent magnet (EPM) which held by robot arm to externally control the locomotion of the magnetic retractor within patient. The disposable magnetic retractor is a consumable surgical instrument that modified from a commercial hemoclip, which has small magnets hangs on the clip legs. The design of the disposable magnetic retractor eliminates the need for endoscope withdrawal which can be inserted through the instrument channel from the handle during ESD operations, like other common instruments. Additionally, a robot-assisted external permanent magnetic source can alleviate the workload of surgeons or assistants on controlling the movement of the EPM for the tissue traction inside patients. Robots assist in translating the heavy EPM with speed and low physical demand. An easily controlled magnetic retractor providing consistent traction force could significantly reduce the procedure time and enhance the process of ESD efficiency. The novel system has potential in reducing the procedure time and reducing the workload of endoscopists. The current pilot study aims to confirm the feasibility and safety of using this robotic magnetic countertraction system for MAG-ESD in patients with gastric and colorectal superficial lesions.

Inclusion Criteria:

• Patient with superficial gastric or colorectal lesions, scheduled for endoscopic submucosal dissection (ESD).

Exclusion Criteria:

1. Patient who refused to participate

2. Other cases deemed by the examining physician as unsuitable for safe treatment

   The robotic magnetic countertraction system consist of a strong permanent magnet which always have a strong magnetic field in its surrounding. Therefore, we follow the MRI precautions for the strict safety measurement:

3. Patient who had a cardiac pacemaker.

4. Patient who had any metallic implant or device, such as drug pump, stent, etc.

5. Patient who has or had any metal fragments in eye or any other part of body, or had ever worked with metal.