Virtual scale function of gastrointestinal endoscopy for accurate polyp size estimation in real-time: a preliminary study

Usefulness of virtual scale endoscope for early gastrointestinal lesions

Objectives

For early gastrointestinal lesions, size is an important factor in the selection of treatment. Virtual scale endoscope (VSE) is a newly developed endoscope that can measure size more accurately than visual measurement. This study aimed to investigate whether VSE measurement is accurate for early gastrointestinal lesions of various sizes and morphologies.

Methods

This study prospectively enrolled patients with early gastrointestinal lesions ≤20 mm in size visually. Lesion sizes were measured in the gastrointestinal tract visually, on endoscopic resection specimens with VSE, and finally on endoscopic resection specimens using a ruler. The primary endpoint was the normalized difference (ND) of VSE measurement. The secondary endpoints were the ND of visual measurement and the variation between NDs of VSE and visual measurements. ND was calculated as (100 × [measured size - true size] / true size) (%). True size was defined as size measured using a ruler.

Results

This study included 60 lesions from April 2022 to December 2022, with 20 each in the esophagus, stomach, and colon. The lesion size was 14.0 ± 6.3 mm (mean ± standard deviation). Morphologies were protruded, slightly elevated, and flat or slightly depressed type in 8, 24, and 28 lesions, respectively. The primary endpoint was 0.3 ± 8.8%. In the secondary endpoints, the ND of visual measurement was -1.7 ± 29.3%, and the variability was significantly smaller in the ND of VSE measurement than in that of visual measurement (p < 0.001, F-test).

Conclusions

VSE measurement is accurate for early gastrointestinal lesions of various sizes and morphologies.

Taking the Guess Work Out of Endoscopic Polyp Measurement: From Traditional Methods to AI

Colonoscopy is a crucial tool for evaluating lower gastrointestinal disease, monitoring high-risk patients for colorectal neoplasia, and screening for colorectal cancer. In the United States, over 14 million colonoscopies are performed annually, with a significant portion dedicated to post-polypectomy follow-up. Accurate measurement of colorectal polyp size during colonoscopy is essential, as it influences patient management, including the determination of surveillance intervals, resection strategies, and the assessment of malignancy risk. Despite its importance, many endoscopists typically rely on visual estimation alone, which is often imprecise due to technological and human biases, frequently leading to overestimations of polyp size and unnecessarily shortened surveillance intervals. To address these challenges, multiple tools and technologies have been developed to enhance the accuracy of polyp size estimation. The review examines the evolution of polyp measurement techniques, ranging from through-the-scope tools to computer-based and artificial intelligence-assisted technologies.

Polyp size measurement during colonoscopy using a virtual scale: variability and systematic differences

BACKGROUND : Accurate polyp size measurement is important for polyp risk stratification and decision-making regarding polypectomy and surveillance. Recently, a virtual scale (VS) function has been developed that allows polyp size measurement through projection of an adaptive VS onto colorectal polyps during real-time endoscopy. We aimed to evaluate the VS in terms of variability and systematic differences. METHODS : We conducted a video-based study with 120 colorectal polyps, measured by eight dedicated colorectal gastroenterologists (experts) and nine gastroenterology residents following endoscopy training (trainees). Three endoscopic measurement methods were compared: (1) visual, (2) snare and (3) VS measurement. We evaluated the method-specific variance (as measure of variability) in polyp size measurements and systematic differences between these methods. RESULTS : Variance in polyp size measurements was significantly lower for VS measurements compared to visual and snare measurements for both experts (0.52 vs. 1.59 and 1.96, p < 0.001) and trainees (0.59 vs. 2.21 and 2.53, p < 0.001). VS measurement resulted in a higher percentage of polyps assigned to the same size category by all endoscopists compared to visual and snare measurements (experts: 69 % vs. 55 % and 59 %; trainees: 67 % vs. 51 % and 47 %) and reduced the maximum difference between individual endoscopists regarding the percentage of polyps assigned to the ≥ 10 mm size category (experts: 1.7 % vs. 10.0 % and 5.0 %; trainees: 2.5 % vs. 6.7 % and 11.7 %). Systematic differences between methods were < 0.5 mm. CONCLUSIONS : Use of the VS leads to lower polyp size measurement variability and more uniform polyp sizing by individual endoscopists compared to visual and snare measurements.

Virtual scale endoscope versus snares for accuracy of size measurement of smaller colorectal polyps: a randomized controlled trial

Accurate measurement of polyp size during colonoscopy is crucial for informing clinical decisions such as resection technique and surveillance scheduling. This study aimed to compare the accuracy of polyp size measurement when using a virtual scale endoscope (VSE) or snare-based polyp size measurement.This randomized controlled trial enrolled 221 patients undergoing screening, surveillance, or diagnostic outpatient colonoscopies. Study subjects were randomized to have polyps detected during the colonoscopy measured for size either using the VSE or a snare of known size to estimate the size of each polyp. All polyps were measured for reference size directly after their removal from the colon using a digital caliper and before formalin fixation.93 polyps were included in the VSE group and 102 in the snare group. The VSE demonstrated significantly higher relative accuracy (80.0% [95%CI 77.0%-82.9%]) compared with snare-based size estimation (66.4% [95%CI 62.4%-70.5%]; P < 0.001). Misclassification rates were lower with the VSE for polyps >2 mm (13.1% vs. 39.3%) and >3 mm (22.6% vs. 55.4%). For diminutive polyps, the VSE better prevented misclassification of >5 mm polyps as 1-5 mm (21.4% vs. 73.0%). The VSE also outperformed snare-based estimation in measuring within 10% of the reference standard size (30.1% vs. 18.6%) and had lower rates of size underestimation (36.5% vs. 65.7%).Using the VSE improves the accuracy of polyp size measurement during colonoscopy in comparison with snare-based size estimation. In clinical scenarios, the VSE reduced misclassifications at clinically relevant size thresholds 2, 3, and 5 mm, which is relevant for the correct choice of polypectomy technique or when implementing resect-and-discard strategies.

Endoscopic size measurement of colorectal polyps: a systematic review of techniques

Accurate size measurement of colorectal polyps is critical for clinical decision making and patient management. This systematic review aimed to evaluate the current techniques used for colonic polyp measurement to improve the reliability of size estimations in routine practice.A comprehensive literature search was conducted across PubMed, EMBASE, and MEDLINE to identify studies relevant to size measurement techniques published between 1980 and March 2024. The primary outcome was the accuracy of polyp sizing techniques used during colonoscopy.61 studies were included with 34 focusing on unassisted and assisted endoscopic visual estimation and 27 on computer-based tools. There was significant variability in visual size estimation among endoscopists. The most accurate techniques identified were computer-based systems, such as virtual scale endoscopes (VSE) and artificial intelligence (AI)-based systems. The least accurate techniques were visual or snare-based polyp size estimation. VSE assists endoscopists by providing an adaptive scale for real-time, direct, in vivo polyp measurements, while AI systems offer size measurements independent of the endoscopist's subjective judgment.This review highlights the need for standardized, accurate, and accessible techniques to optimize sizing accuracy during endoscopic procedures. There is no consensus on a gold standard for measuring polyps during colonoscopy. While biopsy forceps, snare, and graduated devices can improve the accuracy of visual size estimation, their clinical implementation is limited by practical, time, and cost challenges. Computer-based techniques will likely offer improved accuracy of polyp sizing in the near future.

Short- and longer-term learning effects from virtual scale endoscopy videos: a useful tool for colorectal lesion size estimation (with videos)

BACKGROUND AND AIMS

Accurate assessment of colorectal polyp size is crucial for determining treatment and surveillance policies. However, visual estimation of lesion diameter is often inaccurate, making simple and effective educational tools essential. We aimed to evaluate the learning effects of virtual scale endoscopy (VSE).

METHODS

Thirty-three endoscopists first watched prelearning videos for SET1. They then estimated the diameters of 20 lesions and referred to instructional videos with VSE for self-study. Subsequently, they watched the postlearning videos for SET2 and estimated the lesion diameters. The error between the estimated and correct lesion sizes of both sets was compared. To evaluate longer-term learning effects, participants answered SET3 and SET4, which consisted of the same questions as SET2 and SET1, respectively, but 2 to 3 months later without watching the instructional video for SET2.

RESULTS

The error in the participants' estimation of the correct lesion diameter improved from SET1 to SET2 (34.7 ± 6.6 mm vs 30.7 ± 7.7 mm, P = .048), with a significant learning effect and error improvement specifically among nonexperts (35.2 ± 5.3 mm vs 30 ± 6.8 mm, P = .028). In SET3 and SET4, participants' errors indicated that the learning effect was well maintained (SET2 vs SET3: 30.7 ± 7.7 mm vs 28.6 ± 7.2 mm [P = .1]; SET1 vs SET4: 34.7 ± 6.6 mm vs 31.7 ± 7.1 mm [P = .025]).

CONCLUSIONS

VSE videos are a valuable learning tool for estimating lesion diameter, particularly for novice endoscopists, both in the short and longer term.

Enhancing endoscopic measurement: validating a quantitative method for polyp size and location estimation in upper gastrointestinal endoscopy

BACKGROUND

Accurate measurement of polyps size is crucial in predicting malignancy, planning relevant intervention strategies and surveillance schedules. Endoscopists' visual estimations can lack precision. This study builds on our prior research, with the aim to evaluate a recently developed quantitative method to measure the polyp size and location accurately during a simulated endoscopy session.

METHODS

The quantitative method merges information about endoscopic positions obtained from an electromagnetic tracking sensor, with corresponding points on the images of the segmented polyp border. This yields real-scale 3D coordinates of the border of the polyp. By utilising the sensor, positions of any anatomical landmarks are attainable, enabling the estimation of a polyp's location relative to them. To verify the method's reliability and accuracy, simulated endoscopies were conducted in pig stomachs, where polyps were artificially created and assessed in a test-retest manner. The polyp measurements were subsequently compared against clipper measurements.

RESULTS

The average size of the fifteen polyps evaluated was approximately 12 ± 4.3 mm, ranging from 5 to 20 mm. The test-retest reliability, measured by the Intraclass Correlation Coefficient (ICC) for polyp size estimation, demonstrated an absolute agreement of 0.991 (95% CI 0.973-0.997, p < 0.05). Bland & Altman analysis revealed a mean estimation difference of - 0.17 mm (- 2.03%) for polyp size and, a mean difference of - 0.4 mm (- 0.21%) for polyp location. Both differences were statistically non-significant (p > 0.05). When comparing the proposed method with calliper measurements, the Bland & Altman plots showed 95% of size estimation differences between - 1.4 and 1.8 mm (- 13 to 17.4%) which was not significant (p > 0.05).

CONCLUSIONS

The proposed method of measurements of polyp size and location was found to be highly accurate, offering great potential for clinical implementation to improve polyp assessment. This level of performance represents a notable improvement over visual estimation technique used in clinical practice.

Expert endoscopist assessment of colorectal polyp size using virtual scale endoscopy, visual or snare-based estimation: a prospective video-based study

BACKGROUND AND AIMS

Accurate polyp size estimation during colonoscopy has an impact on clinical decision-making. A laser-based virtual scale endoscope (VSE) is available to allow measuring polyp size using a virtual adaptive scale. This study evaluates video-based polyp size measurement accuracy among expert endoscopists using either VSE or visual assessment (VA) with either snare as reference size or without any reference size information.

METHODS

A prospective, video-based study was conducted with 10 expert endoscopists. Video sequences from 90 polyps with known reference size (fresh specimen measured using calipers) were distributed on three different slide sets so that each slide set showed the same polyp only once with either VSE, VA or snare-based information. A slide set was randomly assigned to each endoscopist. Endoscopists were asked to provide size estimation based on video review.

RESULTS

Relative accuracies for VSE, VA, and snare-based estimation were 75.1% (95% CI [71.6-78.5]), 65.0% (95% CI [59.5-70.4]) and 62.0% (95% CI [54.8-69.0]), respectively. VSE yielded significantly higher relative accuracy compared to VA (p = 0.002) and to snare (p = 0.001). A significantly lower percentage of polyps 1-5 mm were misclassified as >5 mm using VSE versus VA and snare (6.52% vs. 19.6% and 17.5%, p = 0.004) and a significantly lower percentage of polyps >5 mm were misclassified as 1-5 mm using VSE versus VA and snare (11.4% vs. 31.9% and 14.9%, p = 0.038).

CONCLUSIONS

Endoscopists estimate polyp size with the highest accuracy when virtual adaptive scale information is displayed. Using a snare to assist sizing did not improve measurement accuracy compared to displaying visual information alone.

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

PURPOSE

Polyp 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.

METHODS

We 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.

RESULTS

The 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.

CONCLUSION

This 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.

Standardizing Scoring Conventions for Crohn's Disease Endoscopy: An International RAND/UCLA Appropriateness Study

BACKGROUND AND AIMS

Endoscopic assessment of disease activity is integral for evaluating treatment response in patients with Crohn's disease (CD). We aimed to define appropriate items for evaluating endoscopic activity and conventions for consistent endoscopic scoring rules in CD.

METHODS

A 2-round modified RAND/University of California at Los Angeles Appropriateness Method study was conducted. A panel of 15 gastroenterologists used a 9-point Likert scale to rate the appropriateness of statements pertaining to the Simple Endoscopic Score for CD, Crohn's Disease Endoscopic Index of Severity, and additional items relevant to endoscopy scoring in CD. Each statement was voted as appropriate, uncertain, or inappropriate based on the median panel rating and presence of disagreement.

RESULTS

Panelists voted that it is appropriate for all ulcers to contribute to endoscopic scoring in CD, including aphthous ulcers, ulcerations at a surgical anastomosis, and anal canal ulcers (scored in the rectum). Endoscopic healing should reflect an absence of ulcers. Narrowing should be defined as a clear decrease in luminal diameter; stenosis should be defined by an impassable narrowing, and if occurring at the junction of 2 segments, scored in the distal segment. Scarring and inflammatory polyps were considered inappropriate for including in the affected area score. The optimal method for defining ulcer depth remains uncertain.

CONCLUSIONS

We outlined scoring conventions for the Simple Endoscopic Score for CD and Crohn's Disease Endoscopic Index of Severity, noting that both scores have limitations. Therefore, we identified priorities for future research and steps for developing and validating a more representative endoscopic index in CD.

Usefulness and Educational Benefit of a Virtual Scale Endoscope in Measuring Colorectal Polyp Size

INTRODUCTION

The virtual scale endoscope (VSE) is a newly introduced endoscope that helps endoscopists in measuring colorectal polyp size (CPS) during colonoscopy by displaying a virtual scale. This study aimed to determine the usefulness of the VSE for CPS measurement and the educational benefit of using VSE images to improve CPS estimation accuracy.

METHODS

This study included 42 colorectal polyps in 26 patients treated at Hiroshima University Hospital. In study 1, CPS measured using a VSE before endoscopic mucosal resection was compared with CPS measured on resected specimens, and the agreement between the two measurement methods was evaluated via Bland-Altman analysis. In study 2, 14 endoscopists (5 beginners, 5 intermediates, and 4 experts) took a pre-test to determine the size of 42 polyps. After the pre-test, a lecture on CPS measurement using VSE images was given. One month later, the endoscopists took a post-test to compare CPS accuracy before and after the lecture.

RESULTS

In study 1, Bland-Altman analysis revealed no fixed or proportional errors. The mean bias ±95% limits of agreement (±1.96 standard deviations) of the measurement error was -0.05 ± 0.21 mm, indicating that the agreement between two measurement methods was sufficient. In study 2, the accuracy of CPS measurement was significantly higher among beginners (59.5% vs. 26.7%, p < 0.01) and intermediates (65.2% vs. 44.3%, p < 0.05) in the post-test than in the pre-test.

CONCLUSION

The VSE accurately measures CPS before resection, and its images are useful teaching tools for beginner and intermediate endoscopists.

Comparing size measurements of simulated colorectal polyp size and morphology groups when using a virtual scale endoscope or visual size estimation: Blinded randomized controlled trial

OBJECTIVES

The virtual scale endoscope (VSE) allows projection of a virtual scale onto colorectal polyps allowing real-time size measurements. We studied the relative accuracy of VSE compared to visual assessment (VA) for the measuring simulated polyps of different size and morphology groups.

METHODS

We conducted a blinded randomized controlled trial using simulated polyps within a colon model. Sixty simulated polyps were evenly distributed across four size groups (1-5, >5-9.9, 10-19.9, and ≥20 mm) and three Paris morphology groups (flat, sessile, and pedunculated). Six endoscopists performed polyp size measurements using random allocation of either VA or VSE.

RESULTS

A total of 359 measurements were completed. The relative accuracy of VSE was significantly higher when compared to VA for all size groups >5 mm (P = 0.004, P < 0.001, P < 0.001). For polyps ≤5 mm, the relative accuracy of VSE compared to VA was not significantly higher (P = 0.186). The relative accuracy of VSE was significantly higher when compared to VA for all morphology groups. VSE misclassified a lower percentage of >5 mm polyps as ≤5 mm (2.9%), ≥10 mm polyps as <10 mm (5.5%), and ≥20 mm polyps as <20 mm (21.7%) compared to VA (11.2%, 24.7%, and 52.3% respectively; P = 0.008, P < 0.001, and P = 0.003).

CONCLUSION

Virtual scale endoscope had significantly higher relative accuracies for every polyp size group or morphology type aside from diminutive. VSE enables the endoscopist to better classify polyps into correct size categories at clinically relevant size thresholds of 5, 10, and 20 mm.

Estimating colorectal polyp size with a virtual scale endoscope and visual estimation during colonoscopy: Prospective, preliminary comparison of accuracy

The virtual scale endoscope (VSE) is a new endoscope that helps estimate the size of neoplasms in the gastrointestinal tract. We compared the accuracy of polyp size estimation by VSE with that of visual estimation. A dual center prospective study was conducted in two Japanese academic endoscopy units. Ten endoscopists (five trainees and five experts) estimated the size of 20 simulated polyps in four colon phantoms during colonoscopy by two methods: conventional visual estimation and estimation by VSE. The primary endpoint was the relative accuracy in relation to true polyp size according to visual estimation and VSE estimation during colonoscopy. The secondary endpoint was the required time (the time needed to measure in each procedure). The mean values of the primary end-point were 62.5% for visual estimation and 84.0% for VSE estimation; hence the result differed significantly (95% confidence interval 18.3-24.7; P < 0.001). The mean of required times was significantly longer for estimation by VSE (6.4 min) than that by visual estimation (2.9 min; P < 0.001). The accuracy of colorectal polyp size estimation was superior with VSE than with visual estimation during colonoscopy. In the future, VSE should be evaluated in actual clinical settings, including the time required for size estimation.