Artificial Polyps Research Articles

A Preclinical Blinded Randomized-Controlled Trial Evaluating the Clinical Relevance of Polyp Size Measurement Using a Virtual Scale Endoscope.

The virtual scale endoscope (VSE) helps endoscopists measure colorectal polyp size more accurately compared to visual assessment (VA). However, previous studies were not adequately powered to evaluate the sizing of polyps at clinically relevant size thresholds and relative accuracy for size subgroups. We created 64 artificial polyps of varied sizes and Paris class morphology, randomly assigned 1:1 to be measured (383 total measurement datapoints with VSE and VA by 6 endoscopists blinded to true size) in a colon model. We added data from two previous trials (480 measurement datapoints). We evaluated for correct classification of polyps into size groups at 3 mm, 5 mm, 10 mm, and 20 mm size thresholds and the relative size measurement accuracy for diminutive polyps (≤5 mm), small polyps (5-9 mm), large polyps at 10-19 mm, and polyps (≥20). VSE had significantly less size group misclassifications at the 5 mm, and 10 mm thresholds (28 percent vs. 45 percent, P = 0.0159 and 26 percent vs. 44 percent, P = 0.0135, respectively). For the 3 mm and 20 mm thresholds, VSE had lower misclassifications; however, this was not statistically significant (36 percent vs. 46 percent, P = 0.3853 and 38 percent vs. 41 percent, P = 0.2705, respectively). The relative size measurement accuracy was significantly higher for VSE compared to VA for all size subgroups (diminutive (P < 0.01), small polyps (P < 0.01), 10-19 mm (P < 0.01), and ≥20 mm (P < 0.01)). VSE outperforms VA in categorizing polyps into size groups at the clinically relevant size thresholds of 5 mm and 10 mm. Using VSE resulted in significantly higher relative measurement accuracy for all size subgroups.

Endoscopic measurement of the size of gastrointestinal polyps using an electromagnetic tracking system and computer vision-based algorithm

PurposePolyp size is an important factor that may influence diagnosis and clinical management decision, but estimation by visual inspection during endoscopy is often difficult and subject to error. The purpose of this study is to develop a quantitative approach that enables an accurate and objective measurement of polyp size and to study the feasibility of the method.MethodsWe attempted to estimate polyp size and location relative to the gastro-oesophageal junction by integrating data from an electromagnetic tracking sensor and endoscopic images. This method is based on estimation of the three-dimensional coordinates of the borders of the polyp by combining the endoscope camera position and the corresponding points along the polyp border in endoscopic images using a computer vision-based algorithm. We evaluated the proposed method using a simulated upper gastrointestinal endoscopy model.ResultsThe difference between the mean of ten measurements of one artificial polyp and its actual size (10 mm in diameter) was 0.86 mm. Similarly, the difference between the mean of ten measurements of the polyp distance from the gastroesophageal junction and its actual distance (~ 22 cm) was 1.28 mm. Our results show that the changes in camera positions in which the images were taken and the quality of the polyp segmentation have the most impact on the accuracy of polyp size estimation.ConclusionThis study demonstrated an innovative approach to endoscopic measurements using motion tracking technologies and computer vision and demonstrated its accuracy in determining the size and location of the polyp. The observed magnitude of error is clinically acceptable, and the measurements are available immediately after the images captured. To enhance accuracy, it is recommended to avoid identical images and instead utilise control wheels on the endoscope for capturing different views. Future work should further evaluate this innovative method during clinical endoscopic procedures.

Two-Endoscope Technique of Endoscopic Mucosal Resection for the Treatment of Gastric Intestinal Metaplasia

Background and Aim: Gastric intestinal metaplasia (GIM) is precancerous with a worldwide prevalence of 25%. Eradicating Helicobacter pylori prevented about half of gastric cancers; failure to prevent the rest was attributed to GIM. GIM is irreversible and often extensive. There is no treatment. Existing endoscopic mucosal resection (EMR) is designed to treat early gastric cancer of usually &lt;2 cm. A two‐endoscope technique of EMR for extensive GIM had been designed and successfully applied. Our aim is to describe the technique in detail. Two-endoscope technique of endoscopic mucosal resection: Patients with histologically confirmed moderate to severe GIM (operative link on GIM [OLGIM] classification) received the treatment in a daycare center. Chromoendoscopy with methylene blue was first performed to disclose and mark the GIM. Submucosal saline injections were used to lift the stained mucosa to form multiple safety cushions, which were then transformed into artificial polyps by suction and ligation, using a cap for ligation of esophageal varices. EMRs were then achieved by snare polypectomy. By rotating two gastroscopes, one designated to perform lift and snare and the other to perform suction and ligation, cycles of lift–ligate–snare were carried out until all stained mucosa was removed. Assessment chromoendoscopy with ≥seven biopsies was performed at 6 months. Results: A total of 227 EMRs were performed in 40 patients, with a median of 3.5 per patient. Bleeding was uncommon and minimal. Gastric perforation ascribable to loss of a safety cushion occurred in one patient. Chromoendoscopy at 6 months in 36 willing patients showed no recurrence of GIM. Conclusion: The two‐endoscope technique of EMR for GIM was essentially safe and effective, with no recurrence at 6 months. It could be performed by endoscopists with standard skills.

Heat sink effect of underwater polypectomy in a porcine colon model

BackgroundUnderwater polypectomy without the need for submucosal injection has been reported. A heat-sink effect by immersing the polyp in water was proposed but no such experiment has been performed to support the claim. We compared the temperature rise on the serosal side during polypectomy between air- and water-filled colon.MethodFreshly harvested porcine colons were placed in a metal tray with cautery electrode pad attached to its bottom. An upper endoscope was used with a cap and a rubber band mounted to the distal end. A mucosal site was randomly selected and identified on its serosal surface with a marker while suction was applied. Suction was applied again and a ligation band was applied to create a polyp. A cautery snare grasped the artificial polyp just below the band. An assistant placed the tip of a thermometer at the marked site on the serosal surface to record the baseline temperature before cautery and the highest temperature during polypectomy. Seven polypectomies in air and underwater were performed.ResultsMean (standard deviation) baseline temperature were 23.3 (0.6) °C and 23.4 (0.6) °C in the air and water groups, respectively. The maximum rise in temperature during polypectomy was 6.1 (4.5) °C and 1.4 (1.0) °C in the air and water groups, respectively (P = 0.004).ConclusionsThe maximum temperature rise during polypectomy was significantly less when polypectomy was performed underwater, supporting the hypothesis that a heat-sink effect does exist during underwater polypectomy.

An artificial aquatic polyp that wirelessly attracts, grasps, and releases objects

The development of light-responsive materials has captured scientific attention and advanced the development of wirelessly driven terrestrial soft robots. Marine organisms trigger inspiration to expand the paradigm of untethered soft robotics into aqueous environments. However, this expansion toward aquatic soft robots is hampered by the slow response of most light-driven polymers to low light intensities and by the lack of controlled multishape deformations. Herein, we present a surface-anchored artificial aquatic coral polyp composed of a magnetically driven stem and a light-driven gripper. Through magnetically driven motion, the polyp induces stirring and attracts suspended targets. The light-responsive gripper is sensitive to low light intensities and has programmable states and rapid and highly controlled actuation, allowing the polyp to capture or release targets on demand. The artificial polyp demonstrates that assemblies of stimuli-responsive materials in water utilizing coordinated motion can perform tasks not possible for single-component devices.

Novel treatment for gastric intestinal metaplasia, a precursor to cancer.

Background and AimGastric intestinal metaplasia (GIM) is precancerous with a worldwide prevalence of 25%. Eradicating Helicobacter pylori prevented about half of gastric cancers; failure to prevent the rest was attributed to GIM. GIM is irreversible and often extensive. There is no treatment. Existing endoscopic mucosal resection (EMR) is designed to treat early gastric cancer of usually <2 cm. We designed a two‐endoscope technique of EMR for extensive lesions such as GIM.MethodsForty patients with histologically confirmed moderate to severe GIM (operative link on GIM [OLGIM] classification) received the treatment in a daycare center. Chromoendoscopy with methylene blue was first performed to indicate the GIM. Submucosal saline injections were used to lift the stained mucosa to form multiple safety cushions, which were transformed into artificial polyps by suction and ligation, using a cap familiar to gastroenterologists for ligation of esophageal varices. EMRs were then achieved by snare polypectomy. By rotating two gastroscopes, one was designated to perform lift and snare and the other to perform suction and ligation; cycles of lift–ligate–snare were performed until all stained mucosa was removed. Assessment chromoendoscopy with ≥seven biopsies was performed at 6 months.ResultsA total of 227 EMRs were performed, with a median of 3.5 per patient. Bleeding was uncommon and minimal. Gastric perforation ascribable to loss of a safety cushion occurred in one patient. Chromoendoscopy at 6 months in 36 willing patients showed no recurrence of GIM.ConclusionThe two‐endoscope technique of EMR for GIM was essentially safe and effective, with no recurrence at 6 months. It could be performed by endoscopists with standard skills.

Use of a novel polyp “ruler snare” improves estimation of colon polyp size

Prior studies have demonstrated that endoscopists' estimates of polyp size are imprecise. The aim of this study was to determine whether a modified polypectomy "ruler snare" improves the accuracy of assessment of polyp size in real time without the use of additional devices. Ten artificial polyps of predetermined sizes (4 to 25 mm) were affixed to the inside of a colon model. A standard polypectomy snare was modified by adding 5-mm graduated markings to the distal end of the plastic sheath. Study participants estimated the sizes of the artificial polyps during simulated colonoscopies, first using a standard snare and then with the modified ruler snare. Thirty-four private practice and academic gastroenterologists participated in the study. Endoscopists' ability to accurately classify polyps by size (diminutive, small, or large) improved from 48.5% to 60.3% with the ruler snare (P = .002). The greatest improvement in precision was seen among the large polyps, where accuracy increased from 35.9% to 58.2% with use of the ruler snare (P < .0001). Participants underestimated polyp size by a mean of 3.6 mm (interquartile range, -5 to -2 mm) with the standard snare and 1.8 mm (interquartile range, -3 to 0 mm) with the ruler snare, which corresponded to a 44.2% improvement in accuracy with the ruler snare (P < .05). The modified ruler snare improved polyp size assessment compared with a standard snare, particularly with large polyps. Overall, although size estimation continues to be imprecise, the addition of calibrated markings to a polypectomy snare is a simple and likely low-cost means to improve neoplasia surveillance recommendations.

Impact of different window settings on colon polyp measurements with CT virtual colonoscopy: a phantom study

The aim of this study was to evaluate the impact of window settings on measurement of colon polyps with CT virtual colonoscopy with experiment. Twenty-four artificial polyps' diameter were measured and scanned 10 times with identical scan parameters using a 64-multidetector computed tomographic scanner. The diameter of each polyp was measured using lung window and abdominal soft tissue window settings and compared with the actual diameter. The lung window setting offers accurate measurement of colon polyps.

Training gastroenterology fellows to perform gastric polypectomy using a novelex vivomodel

To evaluate the effect of hands-on training of gastroenterology fellows in gastric polypectomy using an ex vivo simulator. Eight gastroenterology fellows at Mackay Memorial Hospital, Taipei were evaluated in gastric polypectomy techniques using a pig stomach with artificial polyps created by a rubber band ligation device. The performance of four second year (year-2) fellows who had undergone one year of clinical training was compared with that of four first year (year-1) fellows both before and after a 4-h workshop using the ex vivo simulator. The workshop allowed for hands-on training in the removal of multiple artificial polyps and the placement of hemoclips at the excision site. Evaluation included observation of technical skills, procedure time, and the fellows' confidence scale. One week after the workshop, the year-1 fellows were re-evaluated and had significantly improved mean performance scores (from 17.9 ± 1.8 to 22.5 ± 0.7), confidence scale (from 4.5 ± 1.0 to 7.8 ± 0.5) and procedure time (from 615.0 ± 57.4 s to 357.5 ± 85.0 s) compared with their baseline performance. After 4 h of training using the ex vivo simulator, the skills of the year-1 fellows were statistically similar to those of the year-2 fellows. Use of this ex vivo simulator significantly improved the endoscopic gastric polypectomy skills of gastroenterology fellows who had not had previous clinical training in gastric polypectomy.

The impact of experience on polyp detection and sizing accuracy at capsule endoscopy: implications for training from an animal model study

Indications for capsule endoscopy include polyp surveillance in Peutz-Jeghers syndrome and potentially colorectal examination and bowel cancer screening. The ability to detect and accurately size polyps associated with these conditions is critical when deciding which patients require further investigation or therapy. Inexperience may affect the ability of capsule endoscopists to perform these skills resulting in sub-optimal patient care. We assessed the performance of volunteers with different levels of endoscopy and capsule endoscopy experience using an animal-based polyp model. Thirty-six artificial polyps were sewn onto the luminal surface of porcine small bowel through which a capsule was propelled. Video images generated by the capsule were then shown to five expert capsule endoscopists, seven consultant gastroenterologists, seven trainee gastroenterologists, six endoscopy nurses, six gastrointestinal radiologists, and six nonmedical participants. Polyp detection rates and sizing accuracy were calculated according to each group and compared. Expert capsule endoscopists had the highest polyp detection rate (91%) but only noncapsule endoscopy experience was independently correlated with improved polyp detection and sizing accuracy (OR missing polyp--endoscopy experience 1.0, no experience 1.96 [95% CI 1.29 - 2.97], P = 0.002; ratio of estimated to actual size--endoscopy experience 1.0, no experience 1.43 [95% CI 1.22 - 1.66], P < 0.001). Both expert capsule endoscopists and experienced endoscopists tended to underestimate polyp size more than novices, particularly for large polyps (OR capsule expert to non-expert: 2.39 vs. 1.0 [95% CI 1.73 - 3.29], P < 0.001). Polyp detection rates and sizing accuracy during capsule endoscopy improve with endoscopic experience. However large polyps, which are the most clinically relevant, are least-accurately sized, and capsule endoscopy experts and experienced endoscopists are the most likely to underestimate the size of these polyps. Training to improve performance in these measures for capsule endoscopy novices as well as experts is required.

Polyp Detection with MDCT: A Phantom-Based Evaluation of the Impact of Dose and Spatial Resolution

The objective of our study was to evaluate the impact of dose and spatial resolution on the detection of colonic polyps using a 4-MDCT scanner. Twenty-four latex phantoms that simulate the large bowel and contain artificial polyps of different sizes and shapes were constructed. The polyps were divided into three size groups (diameter, 0-2, 2-5, and 5-10 mm) and were classified into four shape groups: pedunculated; broad-based; ulcerated or depressed; and sessile or flat. The colon phantoms were submerged in a water tank and scanned on a 4-MDCT scanner using 12 protocols with various settings of slice thickness, pitch, and tube current. The images were independently evaluated by three radiologists using axial 2D multiplanar reconstruction images and a 3D surface-rendering technique (fly-through). At a constant dose (i.e., dose-length product [DLP]), the polyp detection rate increased with increasing axial spatial resolution. For the standard protocol (2.50-mm slice thickness, 1.5 pitch), the detection rate for all polyp sizes decreased from approximately 70% at 100 mA to 55% at 40 mA. Between a 60- and 100-mA tube current, the detection rate for the largest polyps (> 5 mm) was almost constant, close to 90%. The detection of polyps in the large bowel using a standard protocol can be improved without dose penalty by increasing the axial spatial resolution of the image acquisition and adjusting the tube current setting. If the analysis can be restricted to polyps larger than 5 mm, the dose can be substantially reduced without compromising the detection rate.

Endoscopic mucosal resection

Endoscopic mucosal resection is a novel technique that allows the endoscopist to diagnose and initiate appropriate therapy for superficial gastrointestinal cancers. The technique improves diagnosis by reliably removing tissue to the depth of the submucosa, which is not usually achieved by standard endoscopic biopsy. The depth of resection permits the diagnosis of submucosal tumors or dysplasia-associated lesions or mass lesions that have been difficult to diagnose. The technique also removes greater quantities of tissue that allows histologic assessment of the completeness of mucosal resection. Areas of tissue as large as 1 to 4 cm in diameter have been removed using this technique, which allows the endoscopist to completely excise small tumors with an intention to cure the patient. There have been several publications that indicate that this technique may be used to treat early cancers of the esophagus, stomach, and colon with 60% to 85% “cure” rates. The technique can be applied by 3 different methods. The first is a “strip biopsy” technique that combines a forcep and snare placed through a dual-channel therapeutic endoscope. The forcep is used to draw the tissue into the snare for tissue excision. A “suck” technique can also be used by which tissue is suctioned into a cap fitted onto the endoscope. A snare has been fitted around the outside of the cap before application of the suction. The snare can then be closed around the tissue that has been suctioned into the cup. This “suck” technique can be further modified with a variceal ligating device to create an artificial polyp that can subsequently removed with a snare. Finally, the tissue can be cut with an insulated diathermic knife to initially circumscribe the lesion, which is then easy to remove. Any of these techniques can be used for tissue removal safely with equipment that is available to most endoscopists.

Are endoscopic measurements of colonic polyps reliable?

Many clinical studies of colorectal adenomatous polyps rely on endoscopic estimation of polyp size. To examine the reliability of such measurements, we conducted a study using artificial polyps in an endoscopy teaching model. Eight experienced endoscopists estimated the size of 13 polyps in two separate sessions 2 wk apart. Endoscopic estimates of polyp size tended to be significantly lower than the true polyp size for all polyps and all endoscopists at both sessions. We also found a statistically significant difference in the magnitude of the underestimation between the first and second session (p < 0.0001). At the first session, polyps tended to be estimated at 64% of their true size, and at the second session, the estimates tended to be at 77% of the actual polyp size. We estimate the magnitude of the variation in polyp measurements due to individual polyps, endoscopist, and examination session, and discuss the impact these sources of variation have in planning of clinical trials.