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

Small Intestinal Polyp Burden in Pediatric Peutz-Jeghers Syndrome Assessed through Capsule Endoscopy: A Longitudinal Study

The management of pediatric Peutz-Jeghers Syndrome (PJS) focuses on the prevention of intussusception complicating small intestinal (SI) polyposis. This hinges on the accurate appraisal of the polyp burden to tailor therapeutic interventions. Video Capsule Endoscopy (VCE) is an established tool to study SI polyps in children, but an in-depth characterization of polyp burden in this population is lacking. Methods: We performed a retrospective longitudinal cross-sectional analysis of VCE studies in pediatric PJS patients at our institution (CMKC) from 2010 to 2020. Demographic, clinical, and VCE findings reported by three reviewers in tandem were accrued. Polyp burden variables were modeled as functions of patient and study characteristics using linear mixed models adjusted for clustering. Results: The cohort included 15 patients. The total small bowel polyp count and largest polyp size clustered under 30 polyps and <20 mm in size. Luminal occlusion correlated closely with the estimated polyp size. Polyp distribution favored proximal (77%) over distal (66%) small bowel involvement. The adjusted largest polyp size was greater in males. Double Balloon Enteroscopy was associated with a decreased polyp burden. Conclusions: The polyp burden in pediatric PJS patients favors the proximal third of the small intestine, with relatively small numbers and a polyp size amenable to resection through enteroscopy. Male gender and older age were related to an increased polyp burden.

Detection and Classification of Colorectal Polyp Using Deep Learning

Colorectal Cancer (CRC) is the third most dangerous cancer in the world and also increasing day by day. So, timely and accurate diagnosis is required to save the life of patients. Cancer grows from polyps which can be either cancerous or noncancerous. So, if the cancerous polyps are detected accurately and removed on time, then the dangerous consequences of cancer can be reduced to a large extent. The colonoscopy is used to detect the presence of colorectal polyps. However, manual examinations performed by experts are prone to various errors. Therefore, some researchers have utilized machine and deep learning-based models to automate the diagnosis process. However, existing models suffer from overfitting and gradient vanishing problems. To overcome these problems, a convolutional neural network- (CNN-) based deep learning model is proposed. Initially, guided image filter and dynamic histogram equalization approaches are used to filter and enhance the colonoscopy images. Thereafter, Single Shot MultiBox Detector (SSD) is used to efficiently detect and classify colorectal polyps from colonoscopy images. Finally, fully connected layers with dropouts are used to classify the polyp classes. Extensive experimental results on benchmark dataset show that the proposed model achieves significantly better results than the competitive models. The proposed model can detect and classify colorectal polyps from the colonoscopy images with 92% accuracy.

Feasibility, complications, and quality of visualization using video capsule endoscopy in 40 dogs with overt or questionable gastrointestinal bleeding

Background

Prospective studies describing video capsule endoscopy (VCE), its feasibility, and complications in dogs are limited.

Objective

To assess VCE, quality of visualization, complications, and risk factors for incomplete studies in dogs with overt or questionable gastrointestinal bleeding (GIB).

Animals

Forty dogs with overt or questionable GIB.

Methods

Prospective, multicenter, interventional study. From August 2017 to March 2020, dogs were examined by VCE (ALICAM) because of overt or questionable GIB. Reported outcomes included diagnostic results of VCE study, quality of visualization, and complications. Risk factors for incomplete studies were evaluated using logistic regression.

Results

In total, 40 dogs (13 overt, 27 questionable GIB) were included. The capsules were administered PO in 29 and endoscopically in 11 dogs (6 duodenum, 5 stomach). One capsule was not retrieved. In 24 of 39 recordings, bleeding lesions were identified (10 overt GIB, 14 questionable GIB). Overall, the quality of visualization was poor to limited in the stomach and colon, and adequate to good in the small intestine. The most common complication was an incomplete study in 15/39 studies, particularly after oral administration (13/28). Risk factors for incomplete study after oral administration included administration of simethicone or opioids, chronic enteropathy, and capsule gastric transit time >6 hours.

Conclusions and Clinical Importance

Video capsule endoscopy can be used to diagnose a variety of lesions causing bleeding in the gastrointestinal tract of dogs with questionable GIB. Incomplete studies are the most common complications in dogs after oral administration of capsules.

Capsule endoscopy - Recent developments and future directions

INTRODUCTION

Capsule endoscopy (CE) is an established modality in the diagnostic algorithm of small bowel (SB) pathology. Its use has expanded for investigation of upper and lower gastrointestinal diseases with similar prototypes.

AREAS COVERED

This review covers the role and recent advances of CE, as a non-invasive investigative tool.

EXPERT OPINION

The use of upper gastrointestinal CE is useful in patients who require surveillance for varices particularly in the current era of the COVID-19 pandemic. It has also shown high accuracy in the detection of upper gastrointestinal hemorrhage in patients presenting with a suspicion of hemorrhage. Findings on CE help to guide further management by device-assisted enteroscopy. The data on colon CE suggest comparable diagnostic accuracy to colonoscopy for polyp detection; however, more evidence is required in the high-risk group. Crohn's CE has become an integral part of the management of patients with Crohn's disease offering a comparative assessment tool post escalation of therapy. Artificial intelligence within CE has demonstrated similar if not better diagnostic yield compared to the human with a significantly shorter reading time. Artificial intelligence is likely to be in-built within CE reading platforms over the next few years minimizing reporting time and human error.

Automated endoscopic detection and classification of colorectal polyps using convolutional neural networks

BACKGROUND

Recently the American Society for Gastrointestinal Endoscopy addressed the 'resect and discard' strategy, determining that accurate in vivo differentiation of colorectal polyps (CP) is necessary. Previous studies have suggested a promising application of artificial intelligence (AI), using deep learning in object recognition. Therefore, we aimed to construct an AI system that can accurately detect and classify CP using stored still images during colonoscopy.

METHODS

We used a deep convolutional neural network (CNN) architecture called Single Shot MultiBox Detector. We trained the CNN using 16,418 images from 4752 CPs and 4013 images of normal colorectums, and subsequently validated the performance of the trained CNN in 7077 colonoscopy images, including 1172 CP images from 309 various types of CP. Diagnostic speed and yields for the detection and classification of CP were evaluated as a measure of performance of the trained CNN.

RESULTS

The processing time of the CNN was 20 ms per frame. The trained CNN detected 1246 CP with a sensitivity of 92% and a positive predictive value (PPV) of 86%. The sensitivity and PPV were 90% and 83%, respectively, for the white light images, and 97% and 98% for the narrow band images. Among the correctly detected polyps, 83% of the CP were accurately classified through images. Furthermore, 97% of adenomas were precisely identified under the white light imaging.

CONCLUSIONS

Our CNN showed promise in being able to detect and classify CP through endoscopic images, highlighting its high potential for future application as an AI-based CP diagnosis support system for colonoscopy.

Training in video capsule endoscopy: Current status and unmet needs

Since its introduction to clinical practice nearly 20 years ago, wireless capsule endoscopy has revolutionized the landscape in the diagnosis and management of small bowel diseases. Over the past 10 years, capsule endoscopy has evolved beyond the small intestine and a range of capsules are now available to examine the esophagus, stomach and colon. Because of its ease of use, tolerability, paucity of complications and ability to visualize the entire gastrointestinal tract, capsule endoscopy has entered the mainstream of clinical practice. This review of the literature summarizes the current state of capsule training and highlights the limited data available to assess reader competence and standards expected of an independent practitioner. There are neither standardized teaching strategies nor national or international metrics for accreditation of physicians and non-physicians interested in mastering this examination. Summating the few publications, there appears to be consensus that diagnostic expertise improves with experience, and that trainees should be fully supervised for at least 20 full case studies. Formative and summative assessment is advisable and the number of taught cases should not be the sole determinant of competence. The review also highlights differences in recommendations from major national gastroenterology societies. Finally, the authors discuss areas of unmet needs in teaching and learning for capsule endoscopy.

International core curriculum for capsule endoscopy training courses

Capsule endoscopy (CE) has become a first-line noninvasive tool for visualisation of the small bowel (SB) and is being increasingly used for investigation of the colon. The European Society of Gastrointestinal Endoscopy (ESGE) guidelines have specified requirements for the clinical applications of CE. However, there are no standardized recommendations yet for CE training courses in Europe. The following suggestions in this curriculum are based on the experience of European CE training courses directors. It is suggested that 12 hours be dedicated for either a small bowel capsule endoscopy (SBCE) or a colon capsule endoscopy (CCE) course with 4 hours for an introductory CCE course delivered in conjunction with SBCE courses. SBCE courses should include state-of-the-art lectures on indications, contraindications, complications, patient management and hardware and software use. Procedural issues require approximately 2 hours. For CCE courses 2.5 hours for theoretical lessons and 3.5 hours for procedural issued are considered appropriate. Hands-on training on reading and interpretation of CE cases using a personal computer (PC) for 1 or 2 delegates is recommended for both SBCE and CCE courses. A total of 6 hours hands-on session- time should be allocated. Cases in a SBCE course should cover SB bleeding, inflammatory bowel diseases (IBD), tumors and variants of normal and cases with various types of polyps covered in CCE courses. Standardization of the description of findings and generation of high-quality reports should be essential parts of the training. Courses should be followed by an assessment of trainees' skills in order to certify readers' competency.

A Simple Evaluation Tool (ET-CET) Indicates Increase of Diagnostic Skills From Small Bowel Capsule Endoscopy Training Courses: A Prospective Observational European Multicenter Study

Small bowel capsule endoscopy (SBCE) has become a first line diagnostic tool. Several training courses with a similar format have been established in Europe; however, data on learning curve and training in SBCE remain sparse.Between 2008 and 2011, different basic SBCE training courses were organized internationally in UK (n = 2), Italy (n = 2), Germany (n = 2), Finland (n = 1), and nationally in Germany (n = 10), applying similar 8-hour curricula with 50% lectures and 50% hands-on training. The Given PillCam System was used in 12 courses, the Olympus EndoCapsule system in 5, respectively. A simple evaluation tool for capsule endoscopy training (ET-CET) was developed using 10 short SBCE videos including relevant lesions and normal or irrelevant findings. For each video, delegates were required to record a diagnosis (achievable total score from 0 to 10) and the clinical relevance (achievable total score 0 to 10). ET-CET was performed at baseline before the course and repeated, with videos in altered order, after the course.Two hundred ninety-four delegates (79.3% physicians, 16.3% nurses, 4.4% others) were included for baseline analysis, 268 completed the final evaluation. Forty percent had no previous experience in SBCE, 33% had performed 10 or less procedures. Median scores for correct diagnosis improved from 4.0 (IQR 3) to 7.0 (IQR 3) during the courses (P < 0.001, Wilcoxon), and for correct classification of relevance of the lesions from 5.0 (IQR 3) to 7.0 (IQR 3) (P < 0.001), respectively. Improvement was not dependent on experience, profession, SBCE system, or course setting. Previous experience in SBCE was associated with higher baseline scores for correct diagnosis (P < 0.001; Kruskal-Wallis). Additionally, independent nonparametric partial correlation with experience in gastroscopy (rho 0.33) and colonoscopy (rho 0.27) was observed (P < 0.001).A simple ET-CET demonstrated significant improvement of diagnostic skills on completion of formal basic SBCE courses with hands-on training, regardless of preexisting experience, profession, and course setting. Baseline scores for correct diagnoses show a plateau after interpretation of 25 SBCE before courses, supporting this number as a compromise for credentialing. Experience in flexible endoscopy may be useful before attending an SBCE course.

Quantitative measurements in capsule endoscopy

This review summarizes several approaches for quantitative measurement in capsule endoscopy. Video capsule endoscopy (VCE) typically provides wireless imaging of small bowel. Currently, a variety of quantitative measurements are implemented in commercially available hardware/software. The majority is proprietary and hence undisclosed algorithms. Measurement of amount of luminal contamination allows calculating scores from whole VCE studies. Other scores express the severity of small bowel lesions in Crohn׳s disease or the degree of villous atrophy in celiac disease. Image processing with numerous algorithms of textural and color feature extraction is further in the research focuses for automated image analysis. These tools aim to select single images with relevant lesions as blood, ulcers, polyps and tumors or to omit images showing only luminal contamination. Analysis of motility pattern, size measurement and determination of capsule localization are additional topics. Non-visual wireless capsules transmitting data acquired with specific sensors from the gastrointestinal (GI) tract are available for clinical routine. This includes pH measurement in the esophagus for the diagnosis of acid gastro-esophageal reflux. A wireless motility capsule provides GI motility analysis on the basis of pH, pressure, and temperature measurement. Electromagnetically tracking of another motility capsule allows visualization of motility. However, measurement of substances by GI capsules is of great interest but still at an early stage of development.

A critical analysis of the effect of view mode and frame rate on reading time and lesion detection during capsule endoscopy

BACKGROUND AND AIM

Factors influencing reading time and detection of lesions include the view mode (VM) and frame rate (FR) applied during reading of small bowel capsule endoscopy images. The aims of this study were to examine the impact of VM and FR on reading time and lesion detection using a standardized, single-type lesion model.

METHODS

A selected video clip containing a known number of positive images (n = 60) of small bowel angioectasias was read using nine different combinations of VM and FR (VM1, VM2, and VM4 × FR10, FR15, and FR25) in randomized order by six capsule endoscopists. Readers were asked to count all positive images of angioectasias (maximum number of positive images, MPIs) seen during reading. The main outcome measurements were effect of VM and FR on reading time and lesion detection.

RESULTS

Mean MPIs for all VM2 and VM4 were 36 (60 %) and 38 (64 %). They were significantly higher than VM1 of 24 (40 %) (P = 0.011, 0.008). A statistical difference was found when the total MPIs at FR10 were compared to FR15 (P = 0.008) and to FR25 (P < 0.001).

CONCLUSIONS

Both VM and FR significantly influence lesion detection during capsule endoscopy reading.

Optimizing lesion detection in small-bowel capsule endoscopy: from present problems to future solutions

This review presents issues pertaining to lesion detection in small-bowel capsule endoscopy (SBCE). The use of prokinetics, chromoendoscopy, diagnostic yield indicators, localization issues and the use of 3D reconstruction are presented. The authors also review the current status (and future expectations) in automatic lesion detection software development. Automatic lesion detection and reporting, and development of an accurate lesion localization system are the main software challenges of our time. The 'smart', selective and judicious use (before as well as during SBCE) of prokinetics in combination with other modalities (such as real time and/or purge) improves the completion rate of SBCE. The tracking of the capsule within the body is important for the localization of abnormal findings and planning of further therapeutic interventions. Currently, localization is based on transit time. Recently proposed software and hardware solutions are proposed herein. Moreover, the feasibility of software-based 3D representation (attempt for 3D reconstruction) is examined.

Small bowel endoscopy in familial adenomatous polyposis and Lynch syndrome

Patients with familial adenomatous polyposis (FAP) and patients with Lynch syndrome have an increased risk of developing small intestinal neoplasia. In both conditions, the lifetime risk to develop small bowel cancer is estimated to be around 5%. In FAP, this risk is associated with the degree of duodenal polyposis, classically assessed by the Spigelman classification. For this reason, gastroduodenal surveillance with forward-viewing and side-viewing endoscopy is generally recommended. Studies using video capsule endoscopy and balloon-assisted enteroscopy in FAP patients have revealed that jejunal and ileal polyps occur frequently in FAP, especially in those with extensive duodenal polyposis. Nevertheless, the clinical relevance of small bowel polyps beyond the duodenum appears to be limited. Compared to FAP, little is known about the prevalence and natural history of small bowel neoplasia in Lynch syndrome. Surveillance of the small bowel is not recommended in Lynch syndrome, although recent data using capsule endoscopy provided promising results.

Training in Capsule Endoscopy: Are We Lagging behind? Gastroenterol Res Pract. 2012;2012:175248. [PMID: 22566997 PMCID: PMC3332190 DOI: 10.1155/2012/175248]

Capsule endoscopy (CE) is a new modality to investigate the small bowel. Since it was invented in 1999, CE has been adopted in the algorithm of small bowel investigations worldwide. Reporting a CE video requires identification of landmarks and interpretation of pathology to formulate a management plan. There is established training infrastructure in place for most endoscopic procedures in Europe; however despite its wide use, there is a lack of structured training for CE. This paper focuses on the current available evidence and makes recommendations to standardise training in CE.

Comparison between Capsule Endoscopy and Magnetic Resonance Enterography for the Detection of Polyps of the Small Intestine in Patients with Familial Adenomatous Polyposis. Gastroenterol Res Pract. 2012;2012:215028. [PMID: 22518115 PMCID: PMC3296287 DOI: 10.1155/2012/215028]

Objective. The objective of this study was to assess the utility of magnetic resonance enterography (MRE) compared with capsule endoscopy (CE) for the detection of small-bowel polyps in patients with familial adenomatous polyposis (FAP). Methods. Patients underwent MRE and CE. The polyps were classified according to size of polyp: <5 mm (small size), 5-10 mm (medium size), or >10 mm (large size). The location (jejunum or ileum) and the number of polyps (1-5, 6-20, >20) detected by CE were also assessed. MRE findings were compared with the results of CE. Results. Small-bowel polyps, were detected by CE in 4 of the 6 (66%) patients. Three patients had small-sized polyps and one patient had medium-sized polyps. CE detected polyps in four patients that, were not shown on MRE. Desmoid tumors were detected on anterior abdominal wall by MRE. Conclusion. In patients with FAP, CE can detect small-sized polyps in the small intestine not seen with MRE whereas MRE yields additional extraintestinal information.

A prospective study of MR enterography versus capsule endoscopy for the surveillance of adult patients with Peutz-Jeghers syndrome. AJR Am J Roentgenol. 2010;195:108-116. [PMID: 20566803 DOI: 10.2214/ajr.09.3174]

OBJECTIVE

The objective of our study was to assess the utility of MR enterography compared with capsule endoscopy for the detection of small-bowel polyps in patients with Peutz-Jeghers syndrome (PJS).

SUBJECTS AND METHODS

Adult patients with PJS scheduled for surveillance capsule endoscopy were prospectively recruited and underwent MR enterography and capsule endoscopy. Polyps > 10 mm were regarded as clinically relevant. When appropriate, large polyps (> 15 mm) were removed at enteroscopy, enabling correlation with MR enterography and capsule endoscopy findings. Interobserver agreement for MR enterography and capsule endoscopy was calculated. Patient comfort, convenience, and test preference were assessed.

RESULTS

Nineteen patients (median age, 39.6 years) underwent both procedures. There was no significant difference between techniques for the detection of polyps > 10 mm (18 vs 23 polyps at capsule endoscopy and MR enterography, respectively; p = 0.35) or in the number of patients in whom > 10 mm polyps were detected (eight vs 11 patients at capsule endoscopy and MR enterography, respectively; p = 0.38). However, in three patients, large polyps (> 15 mm) detected on MR enterography were not detected on capsule endoscopy; large polyps were seen in six patients at capsule endoscopy and in nine patients at MR enterography (p = 0.25). Interobserver agreement was high for MR enterography but was only fair for capsule endoscopy (kappa = 0.81 and 0.27, respectively). Size assessments of large polyps (> 15 mm) appeared more reproducible with MR enterography than with capsule endoscopy. Patients rated capsule endoscopy as more comfortable than MR enterography. There was no significant difference between the techniques with regard to patient convenience or preference.

CONCLUSION

MR enterography is a promising alternative to capsule endoscopy for small-bowel surveillance in adults with PJS. Although our results suggest that capsule endoscopy is more comfortable for the patient, MR enterography may be less prone to missing large polyps and may be more reliable in their size assessment.

Feasibility of video capsule endoscopy in the management of children with Peutz-Jeghers syndrome: a blinded comparison with barium enterography for the detection of small bowel polyps

OBJECTIVES

Peutz-Jeghers syndrome (PJS) in children may present with anaemia, intussusception, or obstruction from an early age and surgery is common. Prophylactic polypectomy may reduce subsequent complications. Traditional barium enterography (BE) has poor sensitivity and requires significant radiation. We compared the performance of capsule endoscopy (CE) with BE in children with PJS.

MATERIALS AND METHODS

Children with PJS (ages 6.0-16.5 years) were prospectively recruited and underwent BE followed by CE, each reported by expert reviewers blinded to the alternate modality. Number of "significant" (>10 mm) and total number of polyps were recorded. Child preference was assessed using a visual analogue questionnaire. Definitive findings were assessed at laparotomy or enteroscopy, when performed.

RESULTS

There was no significant difference for >10 mm polyp detection. Six polyps were found in 3 children by both modalities: 3 polyps in 2 children at CE, 3 polyps in 1 child at BE (P=0.50). Re-review of 1 CE identified 3 polyps that were missed in 1 child at initial reading. Significantly more <10 mm polyps were identified by CE than BE: 61 vs 6 (P=0.02). CE was significantly more comfortable than BE (median score CE 76 [interquartile range 69-87] vs BE 37 [interquartile range 31-68], P=0.03) and was the preferred investigation in 90% (P=0.02).

CONCLUSIONS

CE is a feasible, safe, and sensitive test for small bowel polyp surveillance in children with PJS. It is significantly more comfortable than BE and is the preferred test of most children for future surveillance. There is a learning curve for reporting CE studies in PJS and appropriate training is essential.

Computer-aided learning in capsule endoscopy leads to improvement in lesion recognition ability

BACKGROUND

The rapid expansion in use of capsule endoscopy (CE) has led to discussion about training needs and provision. The lesion recognition skills required for CE are ideally suited to computer-based training.

OBJECTIVE

The aim of this study was to prospectively evaluate the educational effectiveness of a computer-based CE training and testing module on trainees with varying experience.

DESIGN

This was a prospective educational evaluation study.

SETTING

Academic endoscopy unit.

PATIENTS

This study involved 28 trainees of varying CE experience (medical students, gastroenterology trainees) and 4 CE experts.

INTERVENTION

Trainees (medical students and gastroenterology trainees) without CE experience completed a 60-question, computer-based test module consisting of 30-second video clips and multiple-choice questions. Without feedback, trainees then completed a comprehensive, menu-driven, computer-based CE training module. The test module was then completed a second time and feedback was given. Expert performance on the test module was benchmarked by 4 CE experts.

MAIN OUTCOME MEASUREMENTS

The first measure was the difference in baseline performance on the test module between trainees and experts (to determine construct validity). The second measure was a change in performance on the test module after training (to determine content validity of the training module).

RESULTS

A significant difference was noted in baseline performance (P < .001) among CE experts (mean 73.8% +/- 8.0%), gastroenterology trainees (49.5% +/- 10.9%), and medical students (29.5% +/- 3.3%). Performance improved significantly (P < .001) in both trainee groups after training (gastroenterology trainees' posttraining score 62.1% +/- 7.7%; medical students' 46.7% +/- 6.8%).

CONCLUSION

Computer-based learning has a potentially significant role in the development of a training syllabus for CE and in CE accreditation.

Significant small-bowel lesions detected by alternative diagnostic modalities after negative capsule endoscopy

BACKGROUND

Capsule endoscopy (CE) is considered a first-line investigation for obscure GI bleeding (OGIB) and small-bowel polyp or tumor detection. The reliability of a negative CE in excluding gross small-bowel pathology remains unclear. New imaging modalities, such as double-balloon enteroscopy (DBE), CT enterography (CTE) or magnetic resonance enterography (MRE) now provide complementary roles to CE for these indications.

OBJECTIVE

We describe our experience of significant small-bowel pathology missed at CE in 5 patients. The lesions were subsequently detected by DBE, CTE, or MRE.

DESIGN

A retrospective case series.

SETTING

Single-center academic endoscopy unit in a tertiary-referral hospital.

PATIENTS

Five patients were evaluated: 4 with a history of OGIB (transfusion dependent in 2) and 1 patient with Peutz-Jeghers syndrome (PJS) under small-bowel surveillance.

INTERVENTIONS

CE was performed in all patients. Further evaluation via DBE, CTE, or MRE was performed. Definitive treatment was carried out by enteroscopic polypectomy (1 patient), surgical resection (2 patients), and transjugular intrahepatic portosystemic shunt procedure and embolization (1 patient).

MAIN OUTCOME MEASUREMENTS

Detection of significant small-bowel pathology by using DBE, CT, or MRE after a negative capsule study.

RESULTS

Significant small-bowel pathology was missed at CE but was detected by alternative modalities in 5 patients. In 4 patients, the lesions were in the proximal small bowel (adenocarcinoma, malignant melanoma, varices, and stromal tumor). The fifth patient had a large PJS polyp in the proximal ileum.

LIMITATIONS

Retrospective case series with small numbers.

CONCLUSIONS

Gross pathology may be missed at CE, especially in the proximal small bowel, and a negative CE study does not exclude significant disease. Alternative imaging modalities, such as DBE, CTE, or MRE, should be considered when clinical suspicion persists.