Development of a novel endoscopic hemostasis-assisted navigation AI system in the standardization of post-ESD coagulation.

Background and study aims While gastric endoscopic submucosal dissection (ESD) has become a treatment with fewer complications, delayed bleeding remains a challenge. Post-ESD coagulation (PEC) is performed to prevent delayed bleeding. Therefore, we developed an artificial intelligence (AI) to detect vessels that require PEC in real time. Materials and methods Training data were extracted from 153 gastric ESD videos with sufficient images taken with a second-look endoscopy (SLE) and annotated as follows: (1) vessels that showed bleeding during SLE without PEC; (2) vessels that did not bleed during SLE with PEC; and (3) vessels that did not bleed even without PEC. The training model was created using Google Cloud Vertex AI and a program was created to display the vessels requiring PEC in real time using a bounding box. The evaluation of this AI was verified with 12 unlearned test videos, including four cases that required additional coagulation during SLE. Results The results of the test video validation indicated that 109 vessels on the ulcer required cauterization. Of these, 80 vessels (73.4%) were correctly determined as not requiring additional treatment. However, 25 vessels (22.9%), which did not require PEC, were overestimated. In the four videos that required additional coagulation in SLE, AI was able to detect all bleeding vessels. Conclusions The effectiveness and safety of this endoscopic treatment-assisted AI system that identifies visible vessels requiring PEC should be confirmed in future studies.

Concurrent IgG4-related hypophysitis and clinically nonfunctioning gonadotroph pituitary neuroendocrine tumor.

BACKGROUND: Some patients develop immunoglobulin G4 (IgG4)-related hypophysitis associated with systemic diseases. More than 30 cases of IgG4-related hypophysitis have been reported. However, biopsy has rarely been performed in these patients, and none have had an associated pituitary neuroendocrine tumor (PitNET). We present a case of concurrent IgG4-related hypophysitis and PitNET. CASE PRESENTATION: A 56-year-old Japanese man arrived at the hospital with visual impairment, bitemporal hemianopia, and right abducens nerve palsy. Magnetic resonance imaging revealed pituitary body and stalk swelling as well as a small poorly enhanced right anterior lobe mass. Laboratory and loading test results suggested hypopituitarism. Because IgG4 level was elevated, a systemic examination was performed; multiple nodules were found in both lung fields. The diagnosis was based on an endoscopic transnasal biopsy of the pituitary gland. A histopathological examination revealed a marked infiltration of plasma cells into the pituitary gland, which was strongly positive for IgG4. The histological features of the resected tumor were consistent with those of gonadotroph PitNET, which was immunohistochemically positive for follicle-stimulating hormone-ß and steroidogenic factor-1, and no plasma cell infiltration was observed. Based on the histopathological examination results, steroid therapy was initiated, which reduced pituitary gland size and serum IgG4 levels. DISCUSSION AND CONCLUSIONS: This is the first reported case of IgG4-related hypophysitis with PitNET. Although no pathological findings indicating a relationship between the two conditions were found, we were able to preoperatively differentiate multiple lesions via detailed diagnostic imaging.

Artificial intelligence model for analyzing colonic endoscopy images to detect changes associated with irritable bowel syndrome.

IBS is not considered to be an organic disease and usually shows no abnormality on lower gastrointestinal endoscopy, although biofilm formation, dysbiosis, and histological microinflammation have recently been reported in patients with IBS. In this study, we investigated whether an artificial intelligence (AI) colorectal image model can identify minute endoscopic changes, which cannot typically be detected by human investigators, that are associated with IBS. Study subjects were identified based on electronic medical records and categorized as IBS (Group I; n = 11), IBS with predominant constipation (IBS-C; Group C; n = 12), and IBS with predominant diarrhea (IBS-D; Group D; n = 12). The study subjects had no other diseases. Colonoscopy images from IBS patients and from asymptomatic healthy subjects (Group N; n = 88) were obtained. Google Cloud Platform AutoML Vision (single-label classification) was used to construct AI image models to calculate sensitivity, specificity, predictive value, and AUC. A total of 2479, 382, 538, and 484 images were randomly selected for Groups N, I, C and D, respectively. The AUC of the model discriminating between Group N and I was 0.95. Sensitivity, specificity, positive predictive value, and negative predictive value of Group I detection were 30.8%, 97.6%, 66.7%, and 90.2%, respectively. The overall AUC of the model discriminating between Groups N, C, and D was 0.83; sensitivity, specificity, and positive predictive value of Group N were 87.5%, 46.2%, and 79.9%, respectively. Using the image AI model, colonoscopy images of IBS could be discriminated from healthy subjects at AUC 0.95. Prospective studies are needed to further validate whether this externally validated model has similar diagnostic capabilities at other facilities and whether it can be used to determine treatment efficacy.

A Multicenter Prospective Validation Study on Selective Endoscopic Resection of Sessile Serrated Lesions Using Magnifying Colonoscopy in Clinical Practice.

INTRODUCTION: Sessile serrated lesions (SSLs) have malignant potential for colorectal cancer in the serrated pathway. Selective endoscopic resection of SSLs would reduce medical costs and procedure-related accidents, but the accurate endoscopic differentiation of SSLs from hyperplastic polyps (HPs) is challenging. To explore the differential diagnostic performance of magnifying colonoscopy in distinguishing SSLs from HPs, we conducted a multicenter prospective validation study in clinical practice. METHODS: Considering the rarity of diminutive SSLs, all lesions ≥6 mm that were detected during colonoscopy and diagnosed as type 1 based on the Japan narrow-band imaging expert team (JNET) classification were included in this study. Twenty expert endoscopists were asked to differentiate between SSLs and HPs with high or low confidence level after conventional and magnifying NBI observation. To examine the validity of selective endoscopic resection of SSLs using magnifying colonoscopy in clinical practice, we calculated the sensitivity of endoscopic diagnosis of SSLs with histopathological findings as comparable reference. RESULTS: A total of 217 JNET type 1 lesions from 162 patients were analyzed, and 114 lesions were diagnosed with high confidence. The sensitivity of magnifying colonoscopy in detecting SSLs was 79.8% (95% confidence interval [CI]: 74.7-84.4%) overall, and 82.4% (95% CI: 76.1-87.7%) in the high-confidence group. These results showed that the sensitivity of this study was not high enough, even limited in the high-confidence group. CONCLUSIONS: Accurate differential diagnosis of SSLs and HPs using magnifying colonoscopy was challenging even for experts. JNET type 1 lesions ≥6 mm are recommended to be resected because selective endoscopic resection has a disadvantage of leaving approximately 20% of SSLs on site.

Pathology of Crooke Cells in the Human Pituitaries: A Timely Review.

Crooke cell change was first found in the regressed and suppressed corticotroph (adrenocorticotropic hormone-producing) cells, and now is known to occur in pituitary tumors. The tumor cells of this type can be recognized by morphology with immunohistochemistry, and are well known to predict aggressive behavior such as invasion and rare metastases. This is one of the representative neuroendocrine tumors in the pituitary which is now considered to have malignant potential as proposed in the pancreas and gastrointestinal tracts. It is important to emphasize the pituitary tumor pathology such as Crooke cell change for prognostication and appropriate therapies. This review article describes the evolution from the Crooke cells to Crooke cell tumors which is timely along with the Fifth WHO classification 2022 published online.

Factors, Including Clinical Trial Eligibility, Associated with Induction of Third-Line Treatment for Advanced Gastric Cancer.

INTRODUCTION: Third-line chemotherapy has been suggested to improve survival in patients with gastric cancer. This study aimed to identify factors associated with the induction of third-line chemotherapy for advanced gastric cancer, focusing on patient eligibility for clinical trial. METHODS: We retrospectively analyzed 335 patients treated for unresectable or recurrent gastric cancer between April 2009 and May 2020. The patients were grouped into those that met the key eligibility criteria for clinical trial (136 patients, 40.6%) and those that did not (199 patients, 59.4%) before receiving first-line chemotherapy. RESULTS: The overall survival (OS) was 16.8 months (95% CI: 14.0-19.6) and 9.3 months (95% CI: 7.8-11.0) in the eligible and ineligible group, respectively. Multivariate analyses to identify the risk factors associated with the induction of third-line chemotherapy revealed ineligibility of clinical trial (OR 1.95; 95% CI: 1.15-3.31), number of metastatic sites (OR 1.99; 95% CI: 1.23-3.22), low albumin concentration (OR 2.24; 95% CI: 1.14-4.38), and a lack of complete or partial response to first-line treatment (OR 1.85; 95% CI: 1.05-3.26). Indeed, in responders to first-line treatment for ineligible patients, the median OS was 17.7 months (95% CI: 10.6-27.9), respectively. CONCLUSIONS: Treatment outcomes were different for those eligible for clinical trials and those who were not. However, this study suggested that patients who responded to first-line treatment have more favorable prognosis when treated with salvage chemotherapy, even if they were deemed ineligible for clinical trials.

Updates in narrow-band imaging for colorectal polyps: Narrow-band imaging generations, detection, diagnosis, and artificial intelligence.

Narrow-band imaging (NBI) is an optical digital enhancement method that allows the observation of vascular and surface structures of colorectal lesions. Its usefulness in the detection and diagnosis of colorectal polyps has been demonstrated in several clinical trials and the diagnostic algorithms have been simplified after the establishment of endoscopic classifications such as the Japan NBI Expert Team classification. However, there were issues including lack of brightness in the earlier models, poor visibility under insufficient bowel preparation, and the incompatibility of magnifying endoscopes in certain endoscopic platforms, which had impeded NBI from becoming standardized globally. Nonetheless, NBI continued its evolution and the newest endoscopic platform launched in 2020 offers significantly brighter and detailed images. Enhanced visualization is expected to improve the detection of polyps while universal compatibility across all scopes including magnifying endoscopy will promote the global standardization of magnifying diagnosis. Therefore, knowledge related to magnifying colonoscopy will become essential as magnification becomes standardly equipped in future models, although the advent of computer-aided diagnosis and detection may greatly assist endoscopists to ensure quality of practice. Given that most endoscopic departments will be using both old and new models, it is important to understand how each generation of endoscopic platforms differ from each other. We reviewed the advances in the endoscopic platforms, artificial intelligence, and evidence related to NBI essential for the next generation of endoscopic practice.

Double pituitary neuroendocrine tumors in a patient with normal growth hormone level acromegaly: A case report and review of the literature.

Background: Acromegaly is a rare disease caused by growth hormone (GH) hypersecretion caused by a pituitary neuroendocrine tumor (PitNET). However, some acromegaly patients show normal GH levels, and they can be a pitfall in clinical diagnosis. Moreover, rarely, synchronous true double or multiple PitNETs are encountered. Moreover, these PitNETs increase the risk of a left lesion during surgical exploration. Case Description: The patient, who was a 73-year-old female, was referred to our hospital with a chief complaint of headache. Assessment of basal anterior pituitary function revealed a slightly high level of insulin-like growth factor-1 (IGF-1) (standard deviation, 2.4), and her physical findings exhibited mild acromegalic features. The endocrine evaluation confirmed acromegaly and magnetic resonance imaging (MRI) showed a macro PitNET with suprasellar extension. Endoscopic endonasal surgery (EES) was performed to remove the macro PitNET. Although postoperative MRI showed complete removal of the macro PitNET, endocrinological testing indicated no improvement in GH or IGF-1 excess. Pathological examination of the surgical specimen revealed a gonadotropic PitNET. Therefore, we repeated the MRI scan and found a micro PitNET in the thin left normal pituitary gland. A second EES was successfully performed to remove the micro PitNET completely, and both endocrinological and pathological examinations confirmed that the disease was cured. Conclusion: Diagnosing acromegaly with low GH levels requires close monitoring. Double PitNETs are relatively rare and can cause incomplete remission of functional PitNETs.

Efficacy of Combination Therapy with Epinephrine Local Injection and Hemostatic Clips on Active Diverticular Bleeding.

Epinephrine local injection is a hemostatic procedure used in active diverticular bleeding that elicits vasoconstriction and tamponade effects. We compared the additional benefit of combination therapy with HSE-C (hypertonic saline epinephrine injection with clipping) to clipping monotherapy. Retrospective data on diverticular bleeding between 2011 and 2016 was reviewed. Those with an active bleeding source confirmed by colonoscopy (excluding non-bleeding vessels and adherent clots) who received either HSE-C or clipping were evaluated. Endpoints were rates of successful primary hemostasis, recurrent bleeding, and surgical intervention during hospitalization. A total of 320 patients with diverticular bleeding were evaluated, on which either HSE-C (n = 35) or clipping monotherapy (n = 18) was performed. Rates of successful primary hemostasis (91.4% vs. 66.7%, p = 0.048) and direct placement of endoclips (60.0% vs. 16.7%, p = 0.004) were significantly higher in the HSE-C group. Although not statistically significant, the HSE-C group had a higher rate of early rebleeding (18.8% vs. 8.3%, p = 0.653), while no difference was seen in the number of patients requiring surgery (11.4% vs. 5.5%, p = 0.651). HSE-C is associated with a higher rate of successful primary hemostasis for severe active diverticular bleeding but has no significant difference in reducing early recurrent bleeding or the number of patients requiring surgery, suggesting that hemostatic effects may be temporary.

Ultrasonic cleaning is effective in removing carbonized clots and tissue from the insulation-tipped diathermic knife-2.

Objectives: Since carbonized clots and tissue (debris) tend to adhere firmly to the tip of the endoscopic submucosal dissection (ESD) knife as the procedure proceeds, manual removing the firm debris is often challenging and time-consuming. Recently, effective ultrasonic cleaning for other medical devices has been reported. The aim of the present study was to clarify whether ultrasonic cleaning is effective in removing the debris on the insulation-tipped diathermic (IT) knife-2. Methods: This study was an ex-vivo experimental randomized study. A total of 40 IT knife-2 knives with debris on their tip surfaces were prepared and randomly assigned to two groups (Group A and Group B). The knives in Group A were cleaned using the conventional scrubbing method for 30 s (conventional cleaning method), while those in Group B were cleaned using a combined method of scrubbing for 20 s and ultrasonic cleaning for 10 s (combined ultrasonic cleaning method). The tip electrode of the knife after cleaning was photographed under a microscope (40x). The 40 images of the knives were evaluated by independent three endoscopists and two clinical engineers using the five-step evaluation criteria ranging from cleaning score 1 (dirty) to 5 (clean). Results: The mean cleaning score of 3.78 (range: 2.33-4.67) in Group B was significantly higher than that of 1.68 (range: 1.00-2.83) in Group A. Conclusions: The combined ultrasonic cleaning method could remove debris adhering to the IT knife-2 more effectively than the conventional cleaning method. Ultrasonic cleaning may be applied for real-world ESD.

Bilateral Serous Retinal Detachment Associated with a Mitogen-activated Protein KinaseKinase Inhibitor in a Patient with BRAF-mutant Colorectal Cancer.

We herein report a 73-year-old woman with BRAF V600E-mutated colon cancer treated with encorafenib plus cetuximab with binimetinib as standard salvage therapy for patients with advanced colorectal cancer. She developed bilateral serous retinal detachment the next day, and the regimen was discontinued, resulting in complete resolution by the third day. Doublet therapy without binimetinib was initiated along with a weekly ophthalmologic examination for 10 weeks without recurrence of retinal detachment. Thus, binimetinib was presumed to have been the cause of the retinal detachment. This clinical course suggests the need for close monitoring of patients for vision impairment and close collaboration with ophthalmologists.

Performance of perioperative antibiotics against post-endoscopic submucosal dissection coagulation syndrome: a multicenter randomized controlled trial.

BACKGROUND AND AIMS: This study aimed to evaluate the efficacy of perioperative antibiotics against post-endoscopic submucosal dissection (ESD) coagulation syndrome (PECS) in patients undergoing colorectal ESD. METHODS: A prospective, multicenter, randomized controlled, parallel, superiority trial was conducted at 21 Japanese tertiary institutions. Patients with superficial colorectal lesions ≥20 mm and those undergoing ESD management for a single lesion were eligible. Patients with perforation during and after ESD were withdrawn. Before the ESD procedure, participants were randomly assigned (1:1) to either undergo conventional treatment (nonantibiotic group) or investigational treatment (antibiotic group). In the antibiotic group, 3 g of ampicillin-sulbactam was administered just before, 8 hours after, and the morning after ESD. The primary endpoint was the incidence of PECS. The onset of PECS was defined as localized abdominal pain (both spontaneous pain and tenderness) and fever (≥37.6°C) or inflammatory response (leukocytosis [≥10,000 cells/µL] or elevated C-reactive protein level [≥.5 mg/dL]). RESULTS: From February 5, 2019 to September 7, 2020, 432 patients were enrolled and assigned to the antibiotic group (n = 216) or nonantibiotic group (n = 216). After withdrawal of 52 patients, 192 in the antibiotic group and 188 in the nonantibiotic group were analyzed. PECS occurred in 9 of 192 patients (4.7%) in the antibiotic group and 14 of 188 patients (7.5%) in the nonantibiotic group, with an odds ratio of .61 (95% confidence interval, .23-1.56; P = .29). CONCLUSIONS: Perioperative use of antibiotics was not effective in reducing the incidence of PECS in patients undergoing colorectal ESD. (Clinical trial registration number: UMIN000035178.).

Linear Hydrocarbon Chain Growth from a Molecular Diruthenium Carbide Platform.

The formation of linear hydrocarbon chains by sequential coupling of C1 units on the metal surface is the central part of the Fischer-Tropsch (F-T) synthesis. Organometallic complexes have provided numerous models of relevant individual C-C coupling events but have failed to reproduce the complete chain lengthening sequence that transforms a linear Cn hydrocarbon chain into its Cn+1 homologue in an iterative fashion. In this work, we demonstrate stepwise growth of linear Cn hydrocarbon chains and their conversion to their Cn+1 homologues via consecutive addition of CH2 units on a molecular diruthenium carbide platform. The chain growth sequence is initiated by the formation of a µ-η1:η1-C═CH2 ligand from a C + CH2 coupling between the µ-carbido complex [(Cp*Ru)2(η-NPh)(µ-C)] (1; Cp* = η5-C5Me5) and Ph2SCH2. Then, the chain propagates via a general C═CHR + CH2 coupling and subsequent hydrogen-assisted isomerization of the resulting allene ligand µ-η1:η3-H2C═C═CHR to a higher vinylidene homologue µ-η1:η1-C═CH(CH2)R. By repeating this reaction sequence, up to C6 chains have been synthesized in a stepwise fashion. The key step of this chain homologation sequence is the selective hydrogenation of the µ-η1:η3-allene unit to the corresponding µ-alkylidene ligand. Isotope labeling and computational studies indicate that this transformation proceeds via the hydrogenation of the allene ligand to a terminal alkene form and its isomerization to the µ-alkylidene ligand facilitated by the coordinatively unsaturated diruthenium platform.

Molecular, functional, and histopathological classification of the pituitary neuroendocrine neoplasms.

In 2017, WHO published an updated classification of the pituitary adenomas according to the lineages defined by the transcription factors, PIT1, SF1 and TPIT. Nomenclature of the pituitary tumors follows the mature cell types such as somatotroph (GH), lactotroph (LH), thyrotroph, corticotroph, and gonadotroph (FSH, LH). Null cell adenomas are defined by the absence of expression of any hormones and transcription factors. Not infrequently, the pituitary adenomas are invasive to the adjacent structures and are designated as aggressive adenomas. Knosp grading is often used to define the aggressiveness of the tumor. Sparsely granulated somatotroph adenomas and Crooke cell corticotroph adenomas are representative aggressive adenomas. Recently, genomics regarding various adenomas have been clarified, such as GNAS for somatotrophs and USP8 for corticotrophs. Familial pituitary adenomas are another aspect which has been clarified such as MEN1, Carney's complex, familial isolated pituitary adenoma and McCune-Albright syndrome. The pituitary adenomas often produce GH or PRL, hormones of PIT1 transcription factor. It has been agreed that the pituitary adenomas share the characteristics of neuroendocrine neoplasms. The terminology of pituitary neuroendocrine tumor has been discussed. This review article covers various aspects of pituitary adenomas.

Factors associated with inaccurate size estimation of colorectal polyps: A multicenter cross-sectional study.

BACKGROUND AND AIM: Accurate polyp size estimation is essential in deciding the therapeutic strategy of colorectal polyps and endoscopic surveillance intervals. However, many endoscopists frequently make incorrect size estimations without being aware of their errors. This cross-sectional study aimed to clarify the characteristics of endoscopists associated with inaccurate estimation. METHODS: We previously conducted a web trial involving 261 endoscopists in 51 institutions in Japan to assess their ability to estimate polyp size. Participants answered questions about polyp size using visual estimates in a test involving images of 30 polyps. Here, we investigated the relationships between inaccurate size estimation and the backgrounds of participants. The rates of overestimation and underestimation of polyp size were also compared to clarify any trends in the answers of participants with low accuracy (< 50%). RESULTS: Multivariable logistic regression analysis revealed that the number of colonoscopic procedures in the past year was the only factor associated with a low accuracy of polyp size estimation (odds ratio 0.750, 95% confidence interval 0.609-0.925; P = 0.007). Endoscopists with low accuracy had a greater tendency to overestimate polyp size (42.3% overestimation and 21.2% underestimation, P < 0.001) compared with other endoscopists (16.6% overestimation and 17.9% underestimation, P = 0.951). CONCLUSIONS: Endoscopists with limited experience of colonoscopy in the past year were more likely to make frequent errors in size estimation. Furthermore, endoscopists making inaccurate size estimations had a propensity to overestimate polyp size.

Effectiveness of S-O Clip-Assisted Colorectal Endoscopic Submucosal Dissection.

This study aimed to assess the utility of the S-O clip during colorectal endoscopic submucosal dissection (ESD). We conducted a retrospective study on 185 patients who underwent colorectal ESD from January 2015 to January 2020. The patients were divided into two groups: before and after the introduction of the S-O clip. Forty-two patients underwent conventional ESD (CO group) and 29 patients underwent ESD using the S-O clip (SO group). We compared the surgery duration, dissection speed, en bloc resection rate, and complication rate between both groups. Compared with the CO group, the SO group had a significantly shorter surgery duration (70.7 ± 37.9 min vs. 51.2 ± 18.6 min; p = 0.017), a significantly higher dissection speed (15.1 ± 9.0 min vs. 26.3 ± 13.8 min; p < 0.001), a significantly higher en bloc resection rate (80.9% vs. 98.8%; p ≤ 0.001), and a significantly lower perforation rate (4.3% vs. 1.3%). In the right colon, the surgery duration was significantly shorter and the dissection speed was significantly higher in the SO group than in the CO group. Moreover, the rate of en bloc resection improved significantly in the right colon. S-O clip-assisted ESD reduces the procedure time and improves the treatment effects, especially in the right colon.

Serrated polyps of the colon and rectum: Remove or not?

In recent years, the serrated neoplasia pathway where serrated polyps arise as a colorectal cancer has gained considerable attention as a new carcinogenic pathway. Colorectal serrated polyps are histopathologically classified into hyperplastic polyps (HPs), sessile serrated lesions, and traditional serrated adenomas; in the serrated neoplasia pathway, the latter two are considered to be premalignant. In western countries, all colorectal polyps, including serrated polyps, apart from diminutive rectosigmoid HPs are removed. However, in Asian countries, the treatment strategy for colorectal serrated polyps has remained unestablished. Therefore, in this review, we described the clinicopathological features of colorectal serrated polyps and proposed to remove HPs and sessile serrated lesions ≥ 6 mm in size, and traditional serrated adenomas of any size.

Short educational video to improve the accuracy of colorectal polyp size estimation: Multicenter prospective study.

BACKGROUND AND AIM: Accurate polyp size estimation is necessary for appropriate management of colorectal polyps. Polyp size is often determined by subjective visual estimation in clinical situations; however, it is inaccurate, especially for beginner endoscopists. We aimed to clarify the usefulness of our short training video, available on the Internet, for accurate polyp size estimation. METHODS: We conducted a multicenter prospective controlled study in Japan. After completing a pretest composed of near and far images of 30 polyps, participants received the educational video lecture (<10 min long). The educational content included the knowledge of strategies based on polyp size and criteria for size estimation including the endoscopic equipment size and videos of polyps in vivo. After one month, the participants undertook a posttest. The primary outcome was a change in the accuracy of polyp size visual estimation between the pretest and posttest in beginners. RESULTS: Participants including 111 beginners, 52 intermediates, and 97 experts from 51 institutions completed both tests. Accuracy of polyp size estimation in the beginners showed a significant increase after the video lecture [54.1% (51.3-57.0%) to 59.0% (56.5-61.5%), P = 0.003]. Multivariable logistic regression analysis showed that the category of beginners and a low score on pretest (P = 0.020 and <0.001, respectively) were the factors that contributed to an increase of ≥10% in the accuracy. CONCLUSION: Our educational video led to an improvement in polyp size estimation in beginners. Furthermore, this video may be useful for non-beginners with insufficient polyp size estimation accuracy.