Autofluorescence Imaging Images Research Articles

Efficacy of Quantitated Autofluorescence Imaging Endoscopy in Patients With Ulcerative Colitis: A Multicenter Study

BACKGROUND: The evaluation of mucosal inflammation by endoscopy is crucial to determine the therapeutic strategy in patients with ulcerative colitis. The Mayo endoscopic score (Mayo-ES) or Matts endoscopic score (Matts-ES) and the Ulcerative Colitis Endoscopic Index of Severity (UCEIS) have generally been used for endoscopic assessments. Image-enhanced endoscopy, including autofluorescence imaging (AFI), is also applied clinically. It is crucial to understand the characteristics of each endoscopic assessment. The aim of this study was to evaluate these endoscopic assessments in UC patients. METHODS: One hundred and thirty-three patients diagnosed with UC who underwent white light endoscopy (WLE) and AFI at Asahikawa Medical University Hospital between 2007 and 2015 were enrolled in this study. A total of 300 endoscopic images were assessed using the Mayo-ES, Matts-ES, UCEIS and quantified AFI by 5 experts (ex-group) and 5 residents (non-ex-group) in 3 different hospitals. A lesion was categorized as endoscopically active when the Mayo-ES or Matts-ES was 2 or more. AFI images were quantified using an image-analysis software program. The ratio of the reverse gamma value of green (fluorescence) divided by that of red (reflex) was defined as the fluorescence index (F-index). Biopsy specimens were obtained from all lesions corresponding to the images and evaluated according to Matts pathological criteria. We retrospectively investigated 1) the cut-off value of F-index using a receiver operating curve (ROC) analysis, 2) the diagnostic accuracy for mucosal inflammation and the kappa value for the inter-observer agreement of each endoscopic assessment in ex-group and non-ex-group and 3) the additional efficacy of the F-index for improving the Mayo-ES. RESULTS: 1) The ROC analysis showed that the optimum cut-off value for the F-index for active inflammation was 1.00. 2) The accuracy/kappa value of the Mayo-ES, Matts-ES, UCEIS and F-index for active inflammation were 73.5%/0.62, 78.1%/0.78, 80.9%/0.85 and 75.5%/0.96 in the ex-group, respectively, and 71.1%/0.52, 77.4%/0.66, 76.0%/0.71 and 75.8%/0.99 in the non-ex-group, respectively. The UCEIS showed a significantly high accuracy in ex-group in comparison to other assessments, but no significant difference in the non-ex-group in comparison to other assessments. The F-index showed an excellent kappa value in both group. 3) The average accuracy of each Mayo-ES score in the ex-group versus the non-ex-group was as follows: 0, 88.5% vs. 77.7%; 1, 39.2% vs. 48.2%; 2, 92.0% vs. 81.0%; and 3, 97.1% vs. 89.1%, respectively. The F-index significantly increased the diagnostic accuracy in lesions classified into Mayo-ES 1 from 39.2% to 67.8% in the ex-group and 48.2% to 65.4% in the non-ex-group. CONCLUSION(S): The diagnostic accuracy of UCEIS for inflammation activity was significantly higher among experienced endoscopists than non-experienced endoscopists. The quantified AFI (F-index) showed an excellent kappa value with sufficient diagnostic accuracy, regardless of the endoscopic experience, and was thus considered useful for estimating the UC activity, especially for non-experienced endoscopists.

Autofluorescence imaging of macular pigment: influence and correction of ocular media opacities.

The healthy adult human retina contains in its macular region a high concentration of blue-light absorbing carotenoid compounds, known as macular pigment (MP). Consisting of the carotenoids lutein, zeaxanthin, and meso-zeaxanthin, the MP is thought to shield the vulnerable tissue layers in the retina from lightinduced damage through its function as an optical attenuator and to protect the tissue cells within its immediate vicinity through its function as a potent antioxidant. Autofluorescence imaging (AFI) is emerging as a viable optical method for MP screening of large subject populations, for tracking of MP changes over time, and for monitoring MP uptake in response to dietary supplementation. To investigate the influence of ocular media opacities on AFI-based MP measurements, in particular, the influence of lens cataracts, we conducted a clinical trial with a large subject population (93 subjects) measured before and after cataract surgery. General AFI image contrast, retinal blood vessel contrast, and presurgery lens opacity scores [Lens Opacities Classification System III (LOCS III)] were investigated as potential predictors for image degradation. These clinical results show that lens cataracts can severely degrade the achievable pixel contrasts in the AFI images, which results in nominal MP optical density levels that are artifactually reduced. While LOCS III scores and blood vessel contrast are found to be only a weak predictor for this effect, a strong correlation exists between the reduction factor and the image contrast, which can be quantified via pixel intensity histogram parameters. Choosing the base width of the histogram, the presence or absence of ocular media opacities can be determined and, if needed, the nominal MP levels can be corrected with factors depending on the strength of the opacity.

P-153 Autofluorescence Imaging Is Useful to Assess the Severity of Ulcerative Colitis

Autofluorescence imaging (AFI) is a novel technology which can capture the fluorescence emitted from intestinal tissues. While AFI is useful for diagnosing colorectal neoplasms, it is unclear whether AFI can assess the severity of ulcerative colitis (UC). The aim of this prospective study was to evaluate the efficacy of AFI and its quantification in patients with UC. Sixteen patients diagnosed with UC who underwent an AFI examination at Asahikawa Medical University Hospital between 2007 and 2010 were enrolled in this prospective study. Fifty photographs of the lesions in the enrolled patients were randomly selected. Twelve endoscopists separately evaluated the images obtained by white light endoscopy (WLE) and AFI (vAFI), and quantified the intensities of fluorescence. Biopsy specimens were evaluated according to Matt’s criteria. Active inflammation was defined when Matt’s grade was 2 or more. 1) A WLE image which corresponded to Mayo endoscopic subscore 0 or 1 was categorized as inactive. AFI images were visually categorized into 2 groups, green dominant (G) and magenta dominant (M). 2) AFI images were quantified using an image-analysis software program. The ratio of the reverse gamma value of green (fluorescence) divided by that of red (reflex) was defined as the fluorescence index (F index). These endoscopic assessments and F indexes were compared with the histological findings. A cutoff value of the F index for active inflammation was determined using a ROC analysis. 3) The inter-observer consistency of the WLE, vAFI and quantified AFI by twelve endoscopists was calculated. 4) A multivariate analysis was performed to determine which histological findings, including the presence of a crypt abscess, mucin depletion, crypt distortion, neutrophil infiltration, lymphocyte infiltration and an irregular surface, were related to the F index. 1) The average diagnostic accuracy of WLE and vAFI for the histological activity was 69.8% and 67.2%, respectively. No significant difference was observed between these modalities. 2) The correlation coefficient between the F index and histological findings was closely associated with the inflammatory grade (r = −0.641, P < 0.0001). The ROC analysis showed that the optimized range of the F index corresponding to active inflammation was less than 1.3. The average diagnostic accuracy of the F index (87.8%) for histologically active lesions was significantly higher than that of the WLE and vAFI (P < 0.0001, P < 0.0001). 3) The kappa value for the interobserver agreement of the WLE, vAFI and quantified AFI were 0.60, 0.68 and 0.97, respectively. 4) The multivariate analysis showed that lymphocyte infiltration was the only histological finding affecting the F index. The quantified AFI is considered to be a useful and objective measure to assess the activity of ulcerative colitis, and can predict the degree of histological lymphocyte infiltration.

Visualization of colorectal neoplasia by a second-generation autofluorescence imaging system

Objective. Autofluorescence imaging (AFI) systems may allow better visualization of colorectal neoplasia than conventional methods. However, this is difficult to demonstrate objectively. Recently, a second-generation AFI system with a noise-reduction algorithm was developed. We aimed to objectively evaluate the visualization of colorectal neoplasia by using a second-generation AFI system and software to calculate the color-contrast index. Material and methods. We retrospectively reviewed 53 consecutive colorectal neoplasias examined using the second-generation AFI system. Color-contrast indices between the colorectal lesions and the surrounding normal mucosa in the WLI, AFI and NBI images were calculated. The WLI, AFI, NBI and CE images were also evaluated by endoscopists using questionnaire-based visualization scores. Results. The color-contrast index seen in the AFI images (33.74 ± 9.20) was significantly higher than that in either the WLI (11.14 ± 6.14) or NBI images (11.72 ± 7.12). There was no significant difference between the color-contrast indices of the WLI and NBI images. The mean AFI image visualization score (6.7 ± 1.8) was significantly higher than that of WLI (6.0 ± 1.7), and tended to be higher than that of the NBI images (6.1 ± 1.6) when assessed by less-experienced endoscopists. Conclusions. This study objectively demonstrates that compared to WLI and NBI, the second-generation AFI system enables superior visualization of colorectal neoplasms. The visualization scores were higher for the AFI images when evaluated by less-experienced endoscopists. These results indicate that the second-generation AFI system may aid less-experienced endoscopists in the detection of colorectal neoplasia.

Efficacy of a novel auto-fluorescence imaging system with computer-assisted color analysis for assessment of colorectal lesions

To evaluate the efficacy of computer-assisted color analysis of colorectal lesions using a novel auto-fluorescence imaging (AFI) system to distinguish neoplastic lesions from non-neoplastic lesions and to predict the depth of invasion. From January 2013 to April 2013, consecutive patients with known polyps greater than 5 mm in size who were scheduled to undergo endoscopic treatment at The Jikei University Hospital were prospectively recruited for this study. All lesions were evaluated using a novel AFI system, and color-tone sampling was performed in a region of interest determined from narrow band imaging or from chromoendoscopy findings without magnification. The green/red (G/R) ratio for each lesion on the AFI images was calculated automatically using a computer-assisted color analysis system that permits real-time color analysis during endoscopic procedures. A total of 88 patients with 163 lesions were enrolled in this study. There were significant differences in the G/R ratios of hyperplastic polyps (non-neoplastic lesions), adenoma/intramucosal cancer/submucosal (SM) superficial cancer, and SM deep cancer (P < 0.0001). The mean ± SD G/R ratios were 0.984 ± 0.118 in hyperplastic polyps and 0.827 ± 0.081 in neoplastic lesions. The G/R ratios of hyperplastic polyps were significantly higher than those of neoplastic lesions (P < 0.001). When a G/R ratio cut-off value of > 0.89 was applied to determine non-neoplastic lesions, the sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and accuracy were 83.9%, 82.6%, 53.1%, 95.6% and 82.8%, respectively. For neoplastic lesions, the mean G/R ratio was 0.834 ± 0.080 in adenoma/intramucosal cancer/SM superficial cancer and 0.746 ± 0.045 in SM deep cancer. The G/R ratio of adenoma/intramucosal cancer/SM superficial cancer was significantly higher than that of SM deep cancer (P < 0.01). When a G/R ratio cut-off value of < 0.77 was applied to distinguish SM deep cancers, the sensitivity, specificity, PPV, NPV, and accuracy were 80.0%, 84.4%, 29.6%, 98.1% and 84.1%, respectively. The novel AFI system with color analysis was effective in distinguishing non-neoplastic lesions from neoplastic lesions and might allow determination of the depth of invasion.

What is the accuracy of autofluorescence imaging in identifying non‐polypoid colorectal neoplastic lesions when reviewed by trainees? A pilot study

Non-polypoid colorectal neoplasms are difficult to identify using conventional white light (WL) colonoscopy. The aim of the present pilot study was to compare an autofluorescence imaging (AFI) system with conventional WL colonoscopy for the identification of non-polypoid neoplasms by trainees in a colonoscopic observational situation. We selected clear images with both AFI and WL in the same field taken by experts at the National Cancer Center Hospital, Tokyo, from December 2009 to November 2010. One hundred and eighty sets of images (137 non-polypoid neoplasms and 43 without neoplasm) were selected. The images were reviewed by two trainees without AFI experience. After attending a short educational lecture on the AFI system, the reviewers determined the presence of lesions in the randomly arranged images. The accuracy of AFI and WL for identifying non-polypoid neoplasms by trainees was assessed. The sensitivity and specificity for identifying non-polypoid neoplasms by trainees was not significantly different between AFI and WL. However, the specificity tended to be lower in AFI images than in WL images. False-positive results tended to be more frequent for the AFI images than for the WL images. Further improvements in the technology and resolution are necessary for the AFI system to be useful for the detection of colorectal neoplasms. At present, clinical application of the AFI system may require more extensive structured training to improve its accuracy in the identification of non-polypoid colorectal neoplasms.

Comparison of narrowband imaging with autofluorescence imaging for endoscopic visualization of superficial squamous cell carcinoma lesions of the esophagus.

Aim. To compare narrowband imaging (NBI) and autofluorescence imaging (AFI) endoscopic visualization for identifying superficial esophageal squamous cell carcinoma (SCC). Methods. Twenty-four patients with superficial esophageal carcinomas diagnosed at previous hospitals were enrolled in this study. Lesions were initially detected using white-light endoscopy and then observed with both NBI and AFI. Endoscopic images documented each method, and three endoscopists experienced in esophageal imaging retrospectively reviewed respective images of histologically confirmed esophageal SCCs. Images were assessed for quality in identifying superficial SCCs and rated as excellent, fair, or poor by the three reviewers with interobserver agreement calculated using kappa (κ) statistics. Results. Thirty-one lesions histologically confirmed as superficial esophageal SCCs were detected in 24 patients. NBI images of 27 lesions (87%) were rated as excellent, three as fair, and one as poor compared to AFI images of 19 lesions (61%) rated as excellent, 10 as fair and two as poor (P < 0.05). Moderate interobserver agreement (κ = 0.42, 95% CI 0.24–0.60) resulted in NBI while fair agreement (κ = 0.35, 95% CI 0.18–0.51) was achieved using AFI. Conclusion. NBI may be more effective than AFI for visualization of esophageal SCC.

An Inter-Observer Agreement Study of Autofluorescence Endoscopy in Barrett’s Esophagus Among Expert and Non-Expert Endoscopists

Autofluorescence imaging (AFI), which is a "red flag" technique during Barrett's surveillance, is associated with significant false positive results. The aim of this study was to assess the inter-observer agreement (IOA) in identifying AFI-positive lesions and to assess the overall accuracy of AFI. Anonymized AFI and high resolution white light (HRE) images were prospectively collected. The AFI images were presented in random order, followed by corresponding AFI + HRE images. Three AFI experts and 3 AFI non-experts scored images after a training presentation. The IOA was calculated using kappa and accuracy was calculated with histology as gold standard. Seventy-four sets of images were prospectively collected from 63 patients (48 males, mean age 69 years). The IOA for number of AF positive lesions was fair when AFI images were presented. This improved to moderate with corresponding AFI and HRE images [experts 0.57 (0.44-0.70), non-experts 0.47 (0.35-0.62)]. The IOA for the site of AF lesion was moderate for experts and fair for non-experts using AF images, which improved to substantial for experts [κ = 0.62 (0.50-0.72)] but remained at fair for non-experts [κ = 0.28 (0.18-0.37)] with AFI + HRE. Among experts, the accuracy of identifying dysplasia was 0.76 (0.7-0.81) using AFI images and 0.85 (0.79-0.89) using AFI + HRE images. The accuracy was 0.69 (0.62-0.74) with AFI images alone and 0.75 (0.70-0.80) using AFI + HRE among non-experts. The IOA for AF positive lesions is fair to moderate using AFI images which improved with addition of HRE. The overall accuracy of identifying dysplasia was modest, and was better when AFI and HRE images were combined.

Autofluorescence imaging and the quantitative intensity of fluorescence for evaluating the dysplastic grade of colonic neoplasms

Autofluorescence imaging (AFI) is a novel technology which can capture fluorescence emitted from intestinal tissues. While AFI is useful for detecting colorectal neoplasms, it is unclear whether AFI can facilitate the diagnosis by differentiating the extent of dysplasia of colorectal neoplasms. This study investigated the efficacy of AFI in discriminating high-grade from low-grade adenoma. Sixty-seven patients who underwent colonoscopy with AFI were enrolled in this study. The AFI images obtained from 158 lesions in these patients were visually classified into four categories, namely, green (G), green with magenta spots (GM), magenta with green spots (MG), and magenta (M), according to their color intensities, immediately after the examination. The AFI images of the lesions were quantified using an image-analytical software program (F index). Either the F index or the visual assessment was prospectively compared with the dysplastic grade. The F index of the high-grade adenomas was significantly lower than that of the low-grade adenomas, hyperplasia, and normal mucosa (p < 0.05). The incidence of the lesions classified into the M classification for high-grade adenomas (55.6%) was significantly higher than that of either low-grade adenomas (20.8%) or hyperplasia (0%). No correlation was observed between the F index or the visual classification and the tumor shape. The F index was not influenced by the size of the lesion, while the size was significantly associated with the visual classification of AFI. AFI, particularly the F index, is considered to be a useful procedure for estimating the dysplastic grade of colonic adenomas.

The diagnostic accuracy of high-resolution endoscopy, autofluorescence imaging and narrow-band imaging for differentially diagnosing colon adenoma

Conventional colonoscopy can result in unnecessary biopsy or endoscopic resection due to its inability to distinguish adenomas from hyperplastic polyps. This study therefore evaluated the efficacy of high-resolution endoscopy (HRE), autofluorescence imaging (AFI), and narrow-band imaging (NBI) in discriminating colon adenoma from hyperplastic polyps. This was a prospective multicenter study in patients undergoing AFI and NBI examinations. HRE, AFI, and NBI images were classified into two groups based on morphological characteristics, the predominant color intensities, and the visibility of meshed capillary vessels, respectively. Each of the endoscopic photographs were independently evaluated by a single endoscopist. The images were then assessed by three specialists and three residents, the latter having performed < 500 colonoscopies and < 30 NBI and AFI examinations. Diagnostic test statistics were calculated to compare the accuracy in differentiating colon adenoma from hyperplastic polyps for each method. A total of 183 patients were enrolled in the study and 339 adenomas and 85 hyperplastic polyps were identified. AFI and NBI could distinguish adenoma from hyperplastic polyps with an accuracy of 84.9 % and 88.4 %, respectively, whereas HRE exhibited an accuracy of 75.9 %. In the 358 lesions in which the AFI diagnosis was consistent with that of NBI, the accuracy, sensitivity, and specificity were high, at 91.9 %, 92.7 %, and 92.9 %, respectively. During the study comparing specialists and residents, AFI and NBI dramatically improved the diagnostic accuracy of residents from 69.1 % to 86.1 % and 84.7 %, respectively. Both AFI and NBI are considered to be feasible tools that can discriminate colon adenoma from hyperplastic polyps, and their use may be particularly beneficial for less-experienced endoscopists.

Endosopic Autofluorescence Imaging is Useful for the Differential Diagnosis of Intestinal Lymphomas Resembling Lymphoid Hyperplasia

A method for the differential diagnosis of intestinal lymphomas resembling lymphoid hyperplasia (LH) by endoscopy remains to be clearly established. To evaluate the usefulness of autofluorescence imaging (AFI) in diagnosing intestinal lymphoma. Single-center study. Prospective study. One hundred forty-three samples obtained from the intestinal tissues of 21 patients with malignant lymphoma were included in the study. The terminal ileum and entire colon were observed using conventional endoscopy equipped with AFI. The AFI images were taken by 3 endoscopists and then were evaluated by 3 predominant color intensities; green, magenta, and blended. To quantify the strength of fluorescence captured by AFI, the area of the obtained biopsy specimens on images was manually traced, the signal density of either magenta or green was measured, and then the ratio of the reverse gamma value of green divided by that of magenta was defined as the Fluorescence index (F index). The ability to use AFI to distinguish intestinal lymphoma from normal or LH. The cell density is inversely proportional to the F index. The F index of lymphoma was significantly lower than that of normal mucosa or LH. The visual classification of AFI showed the overall accuracy in diagnosing lymphoma was 91.5%, and was well correlated with the F index. Single-center study. AFI-embossed lymphoma lesions seemed as magenta and could be discriminated from LH or normal mucosa with a high overall accuracy through perception of the cell density of the lesion. Therefore, AFI is considered to be an effective procedure for determining the accurate stage and appropriate therapy in intestinal lymphoma.

Su1478 An Inter-Observer Agreement Study of Autofluorescence Endoscopy in Barrett's Oesophagus Among Expert Endoscopists

Autofluorescence imaging (AFI) is used as a ‘red flag' technique during Barrett's surveillance to identify subtle abnormal lesions which are not evident in high resolution white light endoscopy (HRE). This technique was found to have significant false positive results, but the sensitivity remains high. The aim of this study was to assess the interobserver agreement in detecting dysplastic lesions and to assess the overall accuracy of AFI among expert endoscopists. Anonymised AFI and HRE images were prospectively collected from patients undergoing Barrett's surveillance and dysplasia work-up. The AFI images were presented on power point in random order, followed by corresponding HRE and AFI images in a second folder. Three expert endoscopists (>150 AF endoscopies) scored the work sheet on separate occasions after an automated training presentation. The inter-observer agreement was calculated using kappa values (bias corrected) and the accuracy was calculated with histology as gold standard. 74 sets of anonymised white light and AFI images were prospectively collected from 63 patients (48 males, mean age 69). The inter-observer agreement for number of AF lesions noted was fair with a Kappa value of 0.39 (95% CI 0.28-0.52) for AFI images which improved significantly (p=0.04) to moderate kappa (0.57 and 95% CI 0.44-0.7) when corresponding AFI and HRE images are presented side by side. The inter-observer agreement for the quadrant with most significant AF lesion was moderate with a kappa of 0.48 (95% CI 0.37-0.6) which improved (p=0.08) to substantial kappa 0.62 (95% CI 0.50-0.72) when corresponding images were presented. The sensitivity for dysplasia detection was 0.75 (95% CI-0.68-0.81) and 0.84 (95% CI 0.78-0.89) using AFI images alone and using corresponding images respectively. Similarly, the specificity was 0.76 (95% CI 0.71-0.81) and 0.85 (95% CI 0.8-0.89). The overall accuracy of detecting dysplasia was 0.76 (95% CI 0.7-0.81) using AFI images alone and 0.85 (95% CI 0.79-0.89) using corresponding HRE and AFI images. The inter-observer agreement for dysplasia detection in Barrett's oesophagus using AFI images alone is only moderate among expert endoscopists, although it improved with addition of HRE. The overall accuracy of dysplasia using AF imaging was reasonable. Better understanding and recognition of what constitutes an AF positive signal on the endoscopic images is needed to improve this technique.

Evaluation of visualization of squamous cell carcinoma of esophagus and pharynx using an autofluorescence imaging videoendoscope system

An autofluorescence imaging (AFI) videoendoscope system produces pseudo-color images combining autofluorescence and green reflectance, with the utility of this system previously confirmed for the diagnosis of bronchial squamous cell carcinoma (SCC). Our aim was to evaluate visualization of esophageal and pharyngeal SCC comparing AFI with white light endoscopy (WLE). Thirty-two patients with superficial esophageal SCC and 11 patients with superficial pharyngeal SCC diagnosed in other hospitals were enrolled in this prospective study. We observed the esophagus and pharynx with WLE followed by AFI and took both WLE and AFI images of the esophageal and pharyngeal SCC. Three experienced endoscopists subsequently evaluated the visualization quality of images from both systems on a three-tier scale: visible, illegible and invisible. A total of 39 superficial esophageal SCC were diagnosed with 20, 11 and eight lesions classified as visible, illegible and invisible, respectively, by WLE compared to 31, three and five lesions, respectively, using AFI. Using AFI, 79% of superficial esophageal SCC lesions were visible, compared to only 51% with WLE (P < 0.05). In addition, 12 superficial pharyngeal SCC were diagnosed with four, five and three lesions considered as visible, illegible and invisible, respectively, using WLE in contrast to nine, three and 0 lesions, respectively, by AFI. Thus, using AFI, 75% of superficial pharyngeal SCC lesions were visible compared with only 33% with WLE (P = 0.13). The AFI system appears to be more useful than WLE for early diagnosis of SCC of the esophagus and pharynx.

Combining Autofluorescence Imaging and Narrow-Band Imaging for the Differentiation of Adenomas from Non-Neoplastic Colonic Polyps Among Experienced and Non-Experienced Endoscopists

Endoscopic tri-modal imaging incorporates high-resolution white-light endoscopy (HR-WLE), narrow-band imaging (NBI), and autofluorescence imaging (AFI). Combining these advanced techniques may improve endoscopic differentiation between adenomas and non-neoplastic polyps. In this study, we aimed to assess the interobserver variability and accuracy of HR-WLE, NBI, and AFI for polyp differentiation and to evaluate the combined use of AFI and NBI. First, still images of 50 polyps (22 adenomas; median 3 mm) were randomly displayed to three experienced and four non-experienced endoscopists. All HR-WLE and NBI images were scored for Kudo classification and AFI images for color. Second, the combined AFI and NBI images were assessed using a newly developed algorithm by six additional non-experienced endoscopists. The outcomes measured were interobserver agreement and diagnostic accuracy using histopathology as reference standard. Experienced endoscopists had better interobserver agreement for NBI (kappa=0.77) than for AFI (kappa=0.33), whereas non-experienced endoscopists had better agreement for AFI (kappa=0.58) than for NBI (kappa=0.33). The accuracies of HR-WLE, NBI, and AFI among experienced endoscopists were 65, 70, and 74, respectively. Figures among non-experienced endoscopists were 57, 63, and 77. The algorithm was associated with a significantly higher accuracy of 85% among all observers (P<0.023). These figures were confirmed in the second evaluation study. Non-experienced endoscopists have better interobserver agreement and accuracy for AFI than for HR-WLE or NBI, indicating that AFI is easier to use for polyp differentiation in non-experienced setting. The newly developed algorithm, combining information of AFI and NBI together, had the highest accuracy and obtained equal results between experienced and non-experienced endoscopists.

Assessment of novel endoscopic techniques for visualizing superficial esophageal squamous cell carcinoma: autofluorescence and narrow-band imaging

Lugol chromoendoscopy (LCE) is a useful technique for visualizing superficial esophageal squamous cell carcinoma (SESCC), but the stimulating effect of the Lugol solution can sometimes cause clinical problems. Newly developed techniques such as narrow-band imaging (NBI) and autofluorescence imaging (AFI) enable SESCC to be easily visualized without LCE. This study aimed to assess the visualizing power of white-light imaging (WLI), NBI, and AFI, compared with LCE. Sixteen patients with 16 SESCCs underwent LCE and endoscopy with NBI and AFI before endoscopic or surgical treatment. Twenty sets of endoscopic SESCC images were prepared, each of which contained still images from WLI, NBI, AFI, and LCE. The image sets were shown to 25 endoscopists, who then each completed a questionnaire about the ease-of-detection of the SESCCs, scoring WLI, NBI, and AFI images with reference to a perfect score for LCE; mean scores were compared. Overall, significantly higher scores were given for NBI than for WLI and AFI, with no significant difference between WLI and AFI. Stratification by endoscopist characteristics indicated that younger or less experienced endoscopists gave significantly higher scores for AFI than WLI. Stratification by lesion characteristics revealed that AFI had significantly higher scores than WLI for flat/elevated lesions or those with diameter >or=20 mm; scores were significantly lower for depressed lesions or those with diameter <20 mm. For SESCC, the visualizing power of NBI seems more similar to that of LCE than AFI or WLI: NBI might be more useful than AFI or WLI in detecting SESCC. AFI seems to have both superior and inferior visualizing power to WLI depending on characteristics of endoscopists or SESCC lesions.

What Can We See in the Different Lights?

In the study “Usefulness of Autofluorescence Imaging for the Estimating the Extent of Gastric Neoplastic Lesions: a Prospective Multicenter Study” by Lee et al, the authors investigated autofluorescence imaging (AFI) videoendoscopy system for the diagnosis of tumor extent of gastric neoplasms. They suggested that this new imaging system would be beneficial for determinating tumor boundary of gastric epithelial neoplasia before endoscopic resection in selected patients. In this commentary, I would like to add some explanations about the principle of autofluorescence endoscopy and our interpretation of AFI images in the stomach. I believe that the basic knowledge on AFI mechanisms would facilitate the readers in understanding the findings of this new technology. AFI illuminates blue excitation light (390-470 nm) and green light (540-560 nm) that are sequentially provided from a light source instead of ordinary white light through an endoscope to the mucosa. Since the vital organs including the digestive tracts contain certain biomolecules that act as endogeneous fluorophores, they emit natural tissue fluorescence i.e., autofluorescence by the excitation light. The autofluorescence is too weak to be detected by naked eyes of a human being. However, AFI captures it with a high sensitivity charged coupled device (CCD) at the tip of the endoscope and processes real-time pseudocolor images by computation on a video screen. Although the fluorophres exist in both mucosa and submucosa, collagen in the submucosa discharges strong autofluorescence in the green region light. AFI represents difference of autofluorescence property, which is mainly determined by intensity, as color difference, so areas with strong autofluorescence appear bright green and areas with weak autofluorescence appear purple or greenish purple in the images. In the AFI images, normal mucosa in the digestive tract looks green, whereas that in the gastric fundus looks purple. The reason why the gastric body shows unique color is probably because thick fundic mucosa, that has proper gastric function such as acid secretion, reduces autofluorescence from the submucosa. In patients with Helicobacter pylori-associated atrophic gastritis, the fundic mucosa becomes thin, and thus the atrophic mucosa looks green similar to the intestinal mucosa. 1 For a tumor in the digestive tract, it basically appears as a purple area in the green mucosa by AFI because autofluoresce is reduced at tumor. Most of the gastric tumors show similar pattern to tumors in other digestive tract, but some of the tumors look different, green in the AFI images. Our data suggested that tumor color in AFI images has the strongest association with morphology but not with histology. 2

AUTOFLUORESCENCE IMAGING IS USEFUL TO ASSESS ACTIVITY OF ULCERATIVE COLITIS

The efficacy of autofluorescence imaging (AFI) for assessing ulcerative colitis (UC) activity was reviewed. AFI images of UC lesions could be classified into four categories: green; green with purple spots; purple with green spots; and purple. The strength of purple in AFI images of UC lesions is related to histologic severity, thus this classification is helpful to assess the activity of UC. The autofluorescence of AFI images was also quantified using color analysis software. Active lesions had significantly low autofluorescence/reflex ratio than inactive areas in UC patients. The ratio is inversely proportional to histologic severity. When the cut‐off is 0.9, the accuracy to predict histologic activity by AFI is 92%.