How much force is required to perforate a colon during colonoscopy? An experimental study

A multi-modal training environment for colonoscopy with pressure feedback

BACKGROUND

Colonoscopy is a complex procedure with a 3-5% failure rate even for experts. Mastering endoscopy skills and reducing complication rates extend well beyond the initial training phase for most endoscopists, and continues into their clinical experience. Thus, continuing efforts should focus on optimizing training methods to make them individualized with clear objective learning goals for trainees.

METHODS

A hybrid (physical and computer) colonoscopy training simulator was developed using a novel pressure-sensing sleeve covering the full length of a colonoscope, and a physical colon simulator (Kyoto Kagaku) along with custom-designed training software to visualize the color-mapped 3D pressure profile of the colonoscope during the simulated procedure and provide a visual and quantitative evaluation of the endoscopist's skills post-procedure. A system usability questionnaire and objective evaluation metrics were used to determine the model's effectiveness as a training tool.

RESULTS

Thirty-three participants were enrolled in the study, among which 8 were experts and 25 trainees. The interactive maximum and average pressures applied by the trainees were generally higher than those applied by experts, however, this difference was only statistically significant in the recto-sigmoid region. The mean average pressure applied in the rectum and the rectosigmoid region was 6.5 kPa for the experts compared to 13.7 kPa for the trainees, with a p-value of 0.011. Both groups agreed that the system is easy to understand and use, and would be helpful as a learning aid in training programs for colonoscopy skills.

CONCLUSIONS

The proposed system is expected to enhance the quality of colonoscopy procedures by enabling endoscopists to adopt safer and more efficient navigational skills. The evaluation metrics discussed in this research offer useful insights into the performance of endoscopists, and the ability of trainees to compare their performance against expert benchmarks will enable them to establish personalized objective training goals.

Exerting Forces and Wall Load during Duodenoscopy for ERCP: An Experimental Measurement in an Artificial Model

BACKGROUND

Endoscopic retrograde cholangiopancreatography (ERCP) is crucial to the treatment of biliopancreatic diseases with iatrogenic perforation as a potential complication. As of yet, the wall load during ERCP is unknown, as it is not directly measurable during an ERCP in patients.

METHODS

In a life-like, animal-free model, a sensor system consisting of five load cells was attached to the artificial intestines (sensors 1 + 2: pyloric canal-pyloric antrum, sensor 3: duodenal bulb, sensor 4: descending part of the duodenum, sensor 5: distal to the papilla). Measurements were made with five duodenoscopes (n = 4 reusable and n = 1 single use).

RESULTS

Fifteen standardized duodenoscopies were performed. Peak stresses were found at the antrum during the gastrointestinal transit (sensor 1 max. 8.95 N, sensor 2 max. 2.79 N). The load reduced from the proximal to the distal duodenum and the greatest load in the duodenum was discovered at the level of the papilla in 80.0% (sensor 3 max. 2.06 N).

CONCLUSIONS

For the first time, intraprocedural load measurements and exerting forces obtained during a duodenoscopy for ERCP in an artificial model were recorded. None of the tested duodenoscopes were classified as dangerous for patient safety.

GCA-Net: global context attention network for intestinal wall vascular segmentation

PURPOSE

Precise segmentation of intestinal wall vessels is vital to colonic perforation prevention. However, there are interferences such as gastric juice in the vessel image of the intestinal wall, especially vessels and the mucosal folds are difficult to distinguish, which easily lead to mis-segmentation. In addition, the insufficient feature extraction of intricate vessel structures may leave out information of tiny vessels that result in rupture. To overcome these challenges, an effective network is proposed for segmentation of intestinal wall vessels.

METHODS

A global context attention network (GCA-Net) that employs a multi-scale fusion attention (MFA) module is proposed to adaptively integrate local and global context information to improve the distinguishability of mucosal folds and vessels, more importantly, the ability to capture tiny vessels. Also, a parallel decoder is used to introduce a contour loss function to solve the blurry and noisy blood vessel boundaries.

RESULTS

Extensive experimental results demonstrate the superiority of the GCA-Net, with accuracy of 94.84%, specificity of 97.89%, F1-score of 73.80%, AUC of 96.30%, and MeanIOU of 76.46% in fivefold cross-validation, exceeding the comparison methods. In addition, the public dataset DRIVE is used to verify the potential of GCA-Net in retinal vessel image segmentation.

CONCLUSION

A novel network for segmentation of intestinal wall vessels is developed, which can suppress interferences in intestinal wall vessel images, improve the discernibility of blood vessels and mucosal folds, enhance vessel boundaries, and capture tiny vessels. Comprehensive experiments prove that the proposed GCA-Net can accurately segment the intestinal wall vessels.

Endoluminal Motion Recognition of a Magnetically-Guided Capsule Endoscope Based on Capsule-Tissue Interaction Force

A magnetically-guided capsule endoscope, embedding flexible force sensors, is designed to measure the capsule-tissue interaction force. The flexible force sensor is composed of eight force-sensitive elements surrounding the internal permanent magnet (IPM). The control of interaction force acting on the intestinal wall can reduce patient's discomfort and maintain the magnetic coupling between the external permanent magnet (EPM) and the IPM during capsule navigation. A flexible force sensor can achieve this control. In particular, by analyzing the signals of the force sensitive elements, we propose a method to recognize the status of the motion of the magnetic capsule, and provide corresponding formulas to evaluate whether the magnetic capsule follows the motion of the external driving magnet. Accuracy of the motion recognition in Ex Vivo tests reached 94% when the EPM was translated along the longitudinal axis. In addition, a method is proposed to realign the EPM and the IPM before the loss of their magnetic coupling. Its translational error, rotational error, and runtime are 7.04 ± 0.71 mm, 3.13 ± 0.47∘, and 11.4 ± 0.39 s, respectively. Finally, a control strategy is proposed to prevent the magnetic capsule endoscope from losing control during the magnetically-guided capsule colonoscopy.

EXPERIMENTAL ASSESSMENT OF INTACT COLON DEFORMATION UNDER LOCAL FORCES APPLIED BY MAGNETIC CAPSULE ENDOSCOPES

Magnetically guided capsule endoscopy is a promising technology for clinical application. A platform that simulates the magnetic capsule endoscope system is built to study the deformation process of the colon when its lumen suffers local forces. Force-displacement curves of the porcine large intestine under various experiment conditions, including different loading positions (haustra or taeniae coli), loading directions, colon inner pressures and specimen lengths, were measured to analyze the mechanical behavior of the intact large intestine during interactions with magnetic capsule endoscopes. In the practical application of the magnetic capsule endoscope, these data are imperative to optimize the control scheme and reduce operation risks. Based on our experiments, the taeniae coli of the intact large intestine show higher linear stiffness than the haustra, and inflation reduces the linear stiffness of the colon. Magnetic capsule with small edge radii can more easily damage or even perforate the colon. Based on our test results, we suggest that the force applied to the colon should be limited to below 17[Formula: see text]N when the capsule is actuated forward along the colon and limited to below 10[Formula: see text]N when the capsule is vertical to the colon during lesion screening.