Testoni PA, Notaristefano C, Vailati C, Leo MD, Viale E. High-definition colonoscopy with i-Scan: Better diagnosis for small polyps and flat adenomas. World J Gastroenterol 2012; 18(37): 5231-5239 [PMID: 23066318 DOI: 10.3748/wjg.v18.i37.5231]
Corresponding Author of This Article
Pier Alberto Testoni, MD, Division of Gastroenterology and Gastrointestinal Endoscopy, Vita-Salute San Raffaele University, Scientific Institute San Raffaele, Via Olgettina 60, 20132 Milan, Italy. testoni.pieralberto@hsr.it
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Brief Article
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Pier Alberto Testoni, Chiara Notaristefano, Cristian Vailati, Milena Di Leo, Edi Viale, Division of Gastroenterology and Gastrointestinal Endoscopy, Vita-Salute San Raffaele University, Scientific Institute San Raffaele, 20132 Milan, Italy
ORCID number: $[AuthorORCIDs]
Author contributions: Testoni PA was responsible for the conception and design; Notaristefano C, Di Leo M and Vailati C contributed to the analysis and interpretation of the data; Testoni PA and Notaristefano C drafted the article; Testoni PA and Viale E contributed to critical revision of the article for important intellectual content; Testoni PA and Viale E contributed to final approval of the article.
Correspondence to: Pier Alberto Testoni, MD, Division of Gastroenterology and Gastrointestinal Endoscopy, Vita-Salute San Raffaele University, Scientific Institute San Raffaele, Via Olgettina 60, 20132 Milan, Italy. testoni.pieralberto@hsr.it
Telephone: +39-2-26432756 Fax: +39-2-26435609
Received: February 27, 2012 Revised: May 2, 2012 Accepted: May 5, 2012 Published online: October 7, 2012
Abstract
AIM: To investigate if high-definition (HD) colonoscope with i-Scan gave a higher detection rate of mucosal lesions vs standard white-light instruments.
METHODS: Data were collected from the computerized database of the endoscopy unit of our tertiary referral center. We retrospectively analyzed 1101 consecutive colonoscopies that were performed over 1 year with standard white-light (n = 849) or HD+ with i-Scan (n = 252) instruments by four endoscopists, in an outpatient setting. Colonoscopy records included patients’ main details and family history for colorectal cancer, indication for colonoscopy (screening, diagnostic or surveillance), type of instrument used (standard white-light or HD+ plus i-Scan), name of endoscopist and bowel preparation. Records for each procedure included whether the cecum was reached or not and the reason for failure, complications during or immediately after the procedure, and number, size, location and characteristics of the lesions. Polyps or protruding lesions were defined as sessile or pedunculated, and nonprotruding lesions were defined according to Paris classification. For each lesion, histological diagnosis was recorded.
RESULTS: Eight hundred and forty-nine colonoscopies were carried with the standard white-light video colonoscope and 252 with the HD+ plus i-Scan video colonoscope. The four endoscopists did 264, 300, 276 and 261 procedures, respectively; 21.6%, 24.0%, 21.7% and 24.1% of them with the HD+ plus i-Scan technique. There were no significant differences between the four endoscopists in either the number of procedures done or the proportions of each imaging technique used. Both techniques detected one or more mucosal lesions in 522/1101 procedures (47.4%). The overall number of lesions recognized was 1266; 645 in the right colon and 621 in the left. A significantly higher number of colonoscopies recognized lesions in the HD+ plus i-Scan mode (171/252 = 67.9%) than with the standard white-light technique (408/849 = 48.1%) (P < 0.0001). HD+ with i-Scan colonoscopies identified more lesions than standard white-light imaging (459/252 and 807/849, P < 0.0001), in the right or left colon (mean ± SD, 1.62 ± 1.36 vs 1.33 ± 0.73, P < 0.003 and 1.55 ± 0.98 vs 1.17 ± 0.93, P = 0.033), more lesions < 10 mm (P < 0.0001) or nonprotruding (P < 0.022), and flat polyps (P = 0.04). The cumulative mean number of lesions per procedure detected by the four endoscopists was significantly higher with HD+ with i-Scan than with standard white-light imaging (1.82 ± 2.89 vs 0.95 ± 1.35, P < 0.0001).
CONCLUSION: HD imaging with i-Scan during the withdrawal phase of colonoscopy significantly increased the detection of colonic mucosal lesions, particularly small and nonprotruding polyps.
Citation: Testoni PA, Notaristefano C, Vailati C, Leo MD, Viale E. High-definition colonoscopy with i-Scan: Better diagnosis for small polyps and flat adenomas. World J Gastroenterol 2012; 18(37): 5231-5239
Screening colonoscopy is widely considered the gold standard for detection of colonic neoplasia and adenomatous lesions[1]; however, there are several reports of failure to detect small and flat neoplastic lesions[1-10], meaning that in these cases, colonoscopy does not provide adequate protection against colorectal cancer. This inadequacy results in up to 6% of new or missed cancer 3 years after colonoscopy[11,12]. In a recent study, colonoscopy in the preceding 10 years was associated with an overall 77% lower risk for colorectal cancer and approximately 50% lower risk for right-sided cancer[13].
Major factors affecting this polyp miss rate are the presence of blind segments in the colon, poor colon cleaning, and the fact that standard white light may be unable to recognize some small or flat lesions, which are particularly frequent in the right colon. The operator’s experience and a longer withdrawal time, permitting closer observation, can only partly overcome these limitations. Even experienced endoscopists may miss up to 6% of adenomas larger than 1 cm and 30% of all adenomas[2,14,15].
Endoscopes have now been designed to improve mucosal visualization, with a wide angle of view and high-resolution, high-definition imaging. Despite these technical improvements, however, there is still debate about the value of high-definition colonoscopy in clinical practice. Out of 11 studies published so far evaluating the capacity of high-definition imaging to improve the lesion detection rate during colonoscopy, five have concluded that it gave no significant advantage over standard white-light colonoscopy[16-26]. A recent meta-analysis evaluating five studies involving 4422 patients and comparing high-definition vs standard white-light colonoscopy showed that there were marginal differences between the two imaging technologies for detection of colonic polyps and no advantages of high-definition in the detection of high-risk adenomas[27]. The introduction of instantaneous non-white-light imaging that mimics chromoendoscopy (Narrow-band, Olympus Ltd. and FICE, Fujinon Ltd.) makes it possible to enhance contrast and potentially to improve the detection of mucosal lesions; these filter techniques significantly raised the polyp detection rate in all but three of 13 studies to date[16,28-39]. However, two meta-analyses gave conflicting results[38,40].
A newly developed post-processing filter technology, the i-Scan (Pentax Ltd., Tokyo, Japan), combined and integrated into a high-definition processor (EPKi) that generates images above the high-definition television standard (HD+ resolution), highlights the mucosal surface and architecture by surface enhancement (SE), contrast enhancement (CE), and tone enhancement (TE) modes. So far, in all reports but one, retrospective, it permitted significantly better recognition and characterization of the mucosal lesions during colonoscopy[41-45]. In one recent study, narrow-band imaging and i-Scan significantly improved the polyp detection rate and showed similar efficacy[46].
However, most of the studies using these new post-processing filter techniques are based on prospective, controlled clinical trials in a limited number of patients, in which endoscopists are likely to do the colonoscopy more diligently than in routine practice, with adequate bowel preparation, so it is not clear whether the better polyp detection rates reported can be maintained in routine practice.
The aim of the present study was therefore to determine whether the routine use of colonoscopes equipped with high-definition combined with i-Scan technology (HD+ plus i-Scan) gave a higher rate of detection of overall mucosal lesions, particularly of flat adenomas, than standard white-light video colonoscopes, in a consecutive series of patients undergoing screening, diagnostic or surveillance colonoscopy by different endoscopists with similar expertise, in an outpatient clinical practice setting.
MATERIALS AND METHODS
Data for the study were collected from the computerized database of the endoscopy unit of our tertiary referral center. Colonoscopy records included patients’ main details and family history for colorectal cancer, indication for colonoscopy (screening, diagnostic or surveillance), type of instrument used (standard white-light or HD+ plus i-Scan), name of endoscopist, and bowel preparation, defined on the basis of a modified Ottawa scale[47].
Records for each procedure included whether the cecum was reached or not and the reason for failure (inadequate cleaning, strictures, and pain during the procedure), complications during or immediately after the procedure, and number, location and characteristics of the lesions. Polyps or protruding lesions were defined as sessile (Is) or pedunculated (Ip), and nonprotruding lesions as elevated (IIa), flat (IIb), and depressed (IIc), according to Paris classification[48]. For each lesion, histological diagnosis was recorded. Size and location of the lesions were classified as follows: 0-5 mm, 6-10 mm, 11-15 mm, 16-20 mm, 21-30 mm, > 30 mm; right and left colon. Withdrawal time was recorded for all screening colonoscopies, being these procedures the object of other studies. Images of each lesion were stored in the database. For each patient, pO2, heart rate, and blood pressure were measured and recorded before, during and at the end of the procedure.
Data collection
Over a 1-year period, all consecutive screening, diagnostic and surveillance colonoscopies in outpatients done by four expert endoscopists, each of whom had done 200-400 colonoscopies/year for at least 15 years and at least 50 procedures with HD+ plus i-Scan definition equipped instruments were evaluated. The four endoscopists used the two endoscopy techniques in a random fashion, depending of the availability of the instruments. Colonoscopies in subjects younger than 18 years, with genetic-associated colon cancer risk conditions, acute gastrointestinal bleeding, or inflammatory bowel disease were excluded. Procedures with insufficient bowel cleansing, patients in whom residual stool could not be removed by endoluminal washing and suctioning, and patients in whom the cecum was not reached were also excluded.
All patients gave informed consent for the procedures, diagnostic or therapeutic, and for data management for scientific purposes. The retrospective, observational study was approved by the institutional ethics committee.
Examination technique
The bowel was prepared in all cases with polyethylene glycol: 4 L SELG (Promefarm S.r.l, Milan, Italy) or 3 L Moviprep (Norgine GmbH, Marburg, Germany), divided into two parts, were taken the day before the procedure. All patients received conscious sedation with midazolam (Ipnovel, Roche SPA, Basel, Switzerland) and fentanyl (Fentanest, Pfizer, New York, United States) or deep sedation with propofol (Diprivan, AstraZeneca, Zug, Switzerland); 20 mg Butylscopolamin (Buscopan, Boehringer Ingelheim Pharma GmbH, Ingelheim, Germany) were administered if necessary, unless contraindicated.
Standard white-light video colonoscopy was carried out with Pentax colonoscopes EC-3870FZK, EC 3885F, EC 3885L (Pentax Ltd., Tokyo, Japan) and an EPM 3500 or EPK 1000 processor. The colon was inspected during withdrawal of the instrument and lesions were identified and characterized with light imaging only. Magnification was not possible with these endoscopes.
HD+ plus i-Scan video colonoscopy was carried out with Pentax colonoscopes EC-3890FI and EC 3870FZK, using the EPKi processor. The i-Scan technology is a digital contrast method using a light filter that uses different software algorithms with real-time image mapping embedded in the EPKi processor. It enhances mucosal imaging by activating three distinct functions-one for SE mode, the second for CE mode, and the third for TE mode. For SE and CE, there are three enhancement levels (low, medium and high); TE mode can be specifically tailored for the esophagus, stomach, or colon. SE mode enhances the structure through recognition of the edges; compared to normal images, SE images do not differ in brightness and differ little in color, but allow easier recognition of minute glandular structures, which makes it simpler to check changes on the basis of structural differences. With CE mode, areas with lower luminance intensity than surrounding pixels are identified on the basis of pixel-wise luminance intensity data. Processing images with CE does not change the image brightness but enhances minute irregularities and depressed areas of the mucosal surface with a slight bluish-white stain. With TE mode, the RGB components of an ordinary endoscope image are broken down into their parts, and each one is then converted independently along the tone curve, followed by resynthesis of the three components to yield a reconstructed image[43].
The three modes are arranged in series, so two or more can be applied at one time. The modes of enhancement and their levels can be switched on a real-time basis, permitting efficient endoscopic observation.
In all cases, colonoscopy was done using the SE (low) + CE (low) modes; the TE mode for the colon was routinely activated during withdrawal of the instrument once the cecum had been reached, so the whole retrieval phase of the procedure was done using the i-Scan technique with TE mode set for the colon.
Statistical analysis
Data were analyzed using SPSS version 17.0 software (Chicago, IL, United States). Continuous data were described by mean and standard deviation or compared with the Mann-Whitney test. Statistical differences in categorical variables were analyzed using two-sided Fisher’s exact tests or χ2 tests, as appropriate. All differences were considered significant at two-sided P value < 0.05.
RESULTS
A total of 1101 colonoscopy records with images obtained by the four endoscopists were eligible for the study: 849 with the standard white-light video colonoscope and 252 with the HD+ plus i-Scan video colonoscope. The four endoscopists did 264, 300, 276 and 261 procedures, respectively; 21.6%, 24.0%, 21.7% and 24.1% of them with the HD+ plus i-Scan technique. The number of colonoscopies carried out for screening, diagnosis, and surveillance with standard white-light and HD+ plus i-Scan technology by the four endoscopists are reported in Table 1. There were no significant differences between the four endoscopists in either the number of procedures done or the proportions of each imaging technique used.
Table 1 Colonoscopies carried out for screening, diagnosis and surveillance n (%).
Indications
HD+ with i-Scan
Standard white light
Total
Screening
69 (23.9)
219 (76.1)
288
Diagnosis
156 (22.1)
552 (77.9)
708
Follow-up
27 (25.7)
78 (74.3)
105
Total
252
849
1101
Both techniques detected one or more mucosal lesions in 522/1101 procedures (47.4%). The overall number of lesions recognized was 1266: 645 in the right colon and 621 in the left. A significantly higher number of colonoscopies recognized lesions in the HD+ plus i-Scan mode (171/252 = 67.9%) than with the standard white-light technique (408/849 = 48.1%) (P < 0.0001). The number of mucosal lesions recognized by the two imaging techniques and the mean numbers detected by each procedure were significantly higher for HD+ plus i-Scan than with standard white light, for screening, diagnostic, and surveillance colonoscopies (Table 2). In both the right and left colon, HD+ plus i-Scan colonscopy recognized a larger mean number of lesions than standard white light (mean ± SD 1.62 ± 1.36 vs 1.33 ± 0.73, P < 0.003 and 1.55 ± 0.98 vs 1.17 ± 0.93, P = 0.033).
Table 2 High-definition+ with i-Scan and standard white-light colonoscopy detection rates of mucosal lesions.
Overall, 154 nonprotruding lesions were identified and removed: 70 with the HD+ plus i-Scan mode (27.8%) and 84 with the standard white-light technique (9.9%). The HD+ plus i-Scan mode recognized a significantly higher number of nonprotruding lesions than the standard white-light technique (P = 0.04) (Figures 1 and 2).
Figure 1 Flat lesion IIb + IIa on left colon examinated by high-definition-white light and visualized with i-Scan.
A: Flat lesion IIb + IIa of 25 mm × 25 mm on left colon examinated by high-definition white light; B: Same lesion visualized with i-Scan.
Figure 2 Flat lesion 0-IIa visualized with high-definition white light and surface enhancement and visualized with i-Scan and digital chromoendoscopy.
A: Flat lesion 0-IIa visualized with high-definition white light and surface enhancement; B: Same lesion visualized with i-Scan and digital chromoendoscopy.
The overall number and size of the lesions, protruding or nonprotruding, found with HD+ plus i-Scan and standard white light are shown in Table 3. The HD+ plus i-Scan technique identified a significantly larger number of lesions smaller than 10 mm, either protruding or nonprotruding, than standard white light (P < 0.0001); the difference was not significant for lesions measuring 11-20 mm, 21-30 mm, and > 30 mm. Colonoscopies performed with HD+ with i-Scan technique also identified a significantly larger number of overall lesions and nonprotruding lesions smaller than 10 mm than did standard white light (P < 0.0001 and P < 0.022, respectively), while the difference was not different for larger lesions, either protruding or nonprotruding. The differences were not significant considering screening, diagnostic, and surveillance colonoscopies.
Table 3 Number and size of protruding and nonprotruding lesions found with high-definition+ with i-Scan and standard white-light colonoscopy.
HD+ with i-Scan
Standard white light
Total
P value
0-10 mm
< 0.0001
Protruding
341
636
977
Nonprotruding
43
31
74
11-20 mm
0.83
Protruding
30
67
97
Nonprotruding
12
23
35
21-30 mm
0.36
Protruding
9
8
17
Nonprotruding
12
21
33
> 30 mm
Protruding
9
12
21
0.46
Nonprotruding
3
9
12
Among the 154 nonprotruding lesions, histological report was available for 133 lesions, because in 21 cases, resected specimens were missed during colonoscopy (Table 4). Adenoma detection rate was significantly higher with HD+ plus i-Scan mode than with standard white light only for lesions smaller than 10 mm (32/35 vs 19/27, P = 0.05), while the difference was not significant for larger adenomas.
Table 4 Histological report of nonprotruding lesions.
0-10 mm
11-20 mm
21-30 mm
> 30 mm
Total
HD+with i-Scan
Standard white light
HD+with i-Scan
Standard white light
HD+with i-Scan
Standard white light
HD+with i-Scan
Standard white light
Missing
8
4
0
3
0
3
0
3
21
Hyperplastic
3
8
3
2
3
0
0
0
19
Serrated
29
16
6
18
9
18
0
0
96
LGIN
3
3
0
0
0
0
3
6
15
Adenocarcinoma
0
0
3
0
0
0
0
0
3
Total
43
31
12
23
12
21
3
9
154
The number of procedures managed by the four endoscopists and the distribution of HD+ plus i-Scan and standard white-light colonoscopies, with the mean numbers of lesions found by each one. The lesion detection rates were very similar for all four. The cumulative mean number of lesions per procedure detected with the two techniques was significantly higher with the HD+ plus i-Scan than with standard white-light imaging (mean ± SD, 1.82 ± 2.89 vs 0.95 ± 1.35, P < 0.0001). In fact, each of the four endoscopists identified twice as many lesions with the HD+ plus i-Scan as with standard white-light imaging.
The overall withdrawal time, reported only for screening colonoscopies, did not significantly differ between procedures performed with the HD+ plus i-Scan and standard white light (8.4 ± 1.2 min vs 8.3 ± 1.4 min, respectively) (Table 5).
Table 5 Procedures performed by the four endoscopists using the two techniques.
Operator
Procedures
HD+ with i-Scan
Standard white light
Lesions
No. of lesions (mean number of lesions/procedure)
P value
HD+ with i-Scan
Standard white light
1
264
57
207
330
117 (2.05)
213 (1.02)
< 0.0001
2
300
72
228
375
132 (1.83)
243 (1.07)
0.089
3
276
60
216
294
114 (1.9)
180 (0.83)
< 0.0001
4
261
63
198
267
96 (1.52)
171 (0.86)
0.71
Total
1101
252
849
1266
459 (1.82)
807 (0.95)
< 0.0001
DISCUSSION
To date, only one study has evaluated the impact of the routine use of i-Scan with TE mode and HD+ imaging in the detection of mucosal lesion during the withdrawal phase of colonoscopy, compared to standard white-light imaging, in a large series of patients in clinical practice[45]. The study was retrospective and did not improve adenoma detection rate in a population with mixed risk for colorectal cancer.
In our retrospective study, with the HD+ plus i-Scan imaging routinely activated during the withdrawal phase of colonoscopy, once the cecum had been reached, a significantly larger number of examinations identified some mucosal lesion and adenomas, either protruding or flat, and there were also significant improvements in the overall detection rate of lesions and the mean number of lesions recognized for each colonoscopy, compared with standard white-light imaging. The rate was most markedly higher for lesions not bigger than 10 mm and nonprotruding ones. Although the rates of detection of lesions larger than 10 mm did not differ with the two imaging techniques, protruding and nonprotruding lesions smaller than 10 mm were recognized significantly more frequently using the HD+ plus i-Scan technology. In particular, HD+ plus i-Scan technology identified flat polyps smaller than 10 mm three times more than the white-light technique.
The cumulative mean number of lesions per colonoscopy recognized by the four colonoscopists was significantly higher with HD+ plus i-Scan than with standard white-light imaging, while the withdrawal time, when recorded, did not differ between the two techniques.
Only two studies published so far have assessed the combined use of HD+ plus i-Scan for colonoscopy; they have reported similar results in favor of this technique but they were obtained in a prospective trial setting and in a smaller number of selected patients[42,44].
Identifying more polyps by colonoscopy in clinical practice, including small (< 10 mm) and flat ones, may have an important impact for colorectal cancer prevention. The polyp miss rate is probably the main factor accounting for a persistent risk of colorectal cancer reported in 10%-24% of cases after screening colonoscopy[49].
A systematic review of six tandem colonoscopy studies using standard white-light imaging showed an overall polyp miss rate of 22%. The rate rose with smaller lesions, ranging from 2.1% for lesions bigger than 10 mm, to 13% for those between 5 and 10 mm, and up to 26% for those smaller than 5 mm[8]. A prospective multicenter study of back-to-back colonoscopies with white-light imaging reported 9% and 27% miss rates for adenomas > 5 mm and < 5 mm, respectively, and 11% for advanced adenomas[9]. This means that small and flat mucosal lesions, mostly in the right colon, are the ones that may frequently be missed during colonoscopy.
A limited number of studies have compared the efficacy of HD+ colonoscopy with standard white-light colonoscopy, and the findings are far from clear: four of the nine studies concluded that high-definition imaging gave no benefit compared to standard resolution[17,18,21,24]. The addition of electronic filters, such NBI and FICE, to the high-definition imaging did improve the polyp detection rate for small/flat lesions but some results were still disappointing for this end-point[16,30].
Even though there is a general belief that detecting and removing small lesions (1-5 mm) in the colon may not have any significant clinical impact, a number of studies have found that small lesions, mainly flat ones, may have unfavorable histology. One reported that small depressed colorectal lesions had up to a 40% chance of submucosal invasion[49]; two found that 3.9% and 16% of adenomas between 6 and 10 mm had high-grade dysplasia[50,51], and 0.5% of adenomas measuring 6-9 mm were actually cancer[51]. These data might explain the reported occurrence of colorectal cancer after negative screening colonoscopy and support the need for detecting and removing all protruding lesions of the colon, regardless of the size, and selecting the most appropriate techniques to ensure maximum recognition of lesions at colonoscopy.
HD+ plus i-Scan can also differentiate diminutive adenomas and hyperplastic polyps[52], and a recent study using a Markov simulation model suggested that a resect and discard strategy for very small polyps might improve the cost-effectiveness of colorectal cancer screening[53].
A potential limitation of the present study was its retrospective nature. However, data used for analysis, including the adequacy of bowel preparation, were detailed and were collected prospectively for each procedure and stored in a database. Only procedures that included all the data required for the study were considered. As with all nonrandomized trials, potential confounding variables cannot be entirely excluded; however, we examined a large number of colonoscopies and statistical analysis found highly significant differences. Although colonoscopies carried out for different purposes (screening, diagnostic and surveillance) may represent different settings, the differences reported from overall results were also confirmed in the three settings. On the other hand, the retrospective design has the advantage of providing information on the true yield of HD+ plus i-Scan imaging for detecting polyps during colonoscopy in current clinical practice. Prospective trials evaluating new imaging systems could allow the endoscopist to be more attentive during the procedures outside routine practice and very likely give greater accuracy for polyp detection, especially for flat and small lesions, but the good results are not necessarily directly transferable into routine clinical practice.
The lack of documentation of withdrawal time for all colonoscopies is another potential limitation of a retrospective study, compared with prospective ones, because withdrawal time plays an important role in adenoma detection, although here too data are conflicting. In this retrospective evaluation, we were able to assess reliably the withdrawal times only for screening colonoscopies without therapeutic interventions: withdrawal time was comparable by using the two imaging techniques. Besides the imaging technology, probably the endoscopist’s technique and experience is perhaps more important than other factors, including withdrawal time, in detecting polyps by colonoscopy[54-56]. The endoscopists in this study were experts, with many colonoscopies behind them and on their current schedules, and adequate experience with HD+ plus i-Scan imaging in the year leading up to the study. In addition, we compared the numbers of colonic lesions recognized by the same endoscopist using the two techniques, thus applying similar expertise and technique, in a similar clinical setting, and found that the four endoscopists using HD+ plus i-Scan imaging detected cumulatively more lesions. Only one other study comparing the diagnostic yield for colonic polyps using standard white-light and HD+ colonoscopy followed a retrospective design, with an adequate number of unselected patients undergoing colonoscopy in routine practice. The findings confirmed the greater accuracy for detecting polyps of HD imaging compared with white light (42.2% vs 37.8%)[20]. In our hands, 67.8% and 27.8% of colonoscopies with HD+ plus i-Scan recognized some mucosal lesions and flat small polyps (< 10 mm), respectively, compared to 48.1% and 9.9% for standard white-light imaging. HD+ plus i-Scan thus gave an approximately 30% higher diagnostic yield for mucosal lesions of the colon and increased by three times the diagnostic accuracy for flat polyps smaller than 10 mm.
In conclusion, this retrospective study on a large series of consecutive outpatients undergoing colonoscopy in different settings by four expert endoscopists showed that the routine addition of i-Scan to HD imaging during the entire withdrawal phase of colonoscopy, once the cecum had been reached, significantly increased the diagnostic yield for detection of mucosal lesions of the colon, particularly small and nonprotruding ones, without affecting the withdrawal time. In colon cancer screening, the routine use of HD+ plus i-Scan can recognize more mucosal lesions without the need to prolong the withdrawal time to allow for closer inspection, as suggested in other studies, and could probably enable less-skilled endoscopists to achieve performances comparable to those of experienced ones in detecting colonic polyps.
COMMENTS
Background
Screening colonoscopy is widely considered the gold standard for detection of colonic neoplasia and adenomatous lesions, however, there are several reports of failure to detect small and flat neoplastic lesions, meaning that in these cases, colonoscopy does not provide adequate protection against colorectal cancer. Besides the operator’s experience, withdrawal time, quality of colon cleansing, presence of blind segments in the colon, and quality of imaging provided by endoscopes play an important role in lesion detection. Standard white-light imaging may be unable to recognize some small or flat lesions, which are particularly frequent in the right colon, and it may affect the polyp miss rate during routine colonoscopy. High-definition (HD) imaging and filter technologies have been applied to colonoscopies to improve detection of lesions, but results are conflicting.
Research frontiers
Endoscopes have now been designed to improve mucosal visualization, with a wide angle of view, filter-aided techniques that can enhance characterization of mucosal morphology and surface architecture, and high-resolution/high-definition imaging that can improve endoscopic recognition of mucosal lesions. In this study, the authors demonstrated that the routine use of HD+ plus i-Scan recognized more mucosal lesions without the need to prolong the withdrawal time to allow closer inspection.
Innovations and breakthroughs
Recent studies have analyzed the capacity of high-definition imaging to improve the lesion detection rate during colonoscopy with conflicting results. The value of high-definition colonoscopy in clinical practice is still debated. In this study, the authors showed that the routine addition of i-Scan to HD+ imaging during the entire withdrawal phase of the colonoscopy significantly increased the diagnostic yield for detection of mucosal lesions of the colon, particularly small and nonprotruding ones, without affecting the withdrawal time, and could probably enable less-skilled endoscopists to achieve performances comparable to those of experienced ones in detecting mucosal lesions.
Applications
This study may encourage the utilization of advanced imaging technologies to reduce polyp miss rate and improve colonoscopy performance in the prevention of colorectal cancer.
Terminology
The i-Scan technology is a digital contrast method employing a light filter that uses different software algorithms with real-time image mapping embedded in the Pentax EPKi processor. i-Scan enhances mucosal imaging by activating three distinct functions: one for surface enhancement (SE), the second for contrast enhancement (CE), and the third for tone enhancement (TE), allowing a better recognition and characterization of the mucosal lesions during colonoscopy. SE mode enhances the structure through recognition of the edges, compared to normal images, and allows easier recognition of minute glandular structures which makes it simpler to identify changes on the basis of structural differences. CE mode enhances minute irregularities and depressed areas of the mucosal surface with a slight bluish-white stain. In TE mode, the RGB components of an ordinary endoscope image are broken down into their parts, and each one is then converted independently along the tone curve, followed by resynthesis of the three components to yield a reconstructed image.
Peer review
The authors examined the role of HD+ i-Scan vs white-light colonoscopy on polyp detection rates. The research is a significant addition to the literature on the use of contrast technology in improving the quality of colonoscopy in detecting polyps. The results of the study will encourage those regularly involved in performing colonoscopy to consider a lower threshold in utilizing these techniques to improve polyp detection rates. The research novelty is in the fact that the study was conducted in a real clinical practice environment and could be considered to have greater clinical applicability.
Footnotes
Peer reviewer: Dr. Jeff Butterworth, MB, FRCP, Department of Gastroenterology, Shrewsbury and Telford Hospitals NHS Trust, 102 The Mount, Shrewsbury SY3 8PH, United Kingdom
S- Editor Gou SX L- Editor Kerr C E- Editor Xiong L
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