autofluorescence imaging of early colorectal cancer

REVIEW ARTICLE

Autofluorescence imaging of early colorectal cancer

Yoji Takeuchi*, Noboru Hanaoka, Masao Hanafusa, Ryu Ishihara, Koji Higashino,Hiroyasu Iishi, and Noriya Uedo

Department of Gastrointestinal Oncology, Osaka Medical Centre for Cancer and Cardiovascular Diseases,1-3-3 Nakamichi Higashinari-ku, Osaka, 537-8511, Japan

Received 28 February 2011, revised 30 March 2011, accepted 31 March 2011Published online 10 May 2011

Key words: autofluorescence imaging, colonoscopy, early colorectal cancer, image enhanced endoscopy

1. Introduction

Colorectal cancer is one of the most common causesof cancer death in developed countries [1]. Also inJapan, colorectal cancer is increasing and has esti-mated most common cause of cancer death in 2015[2]. Most sporadic non-hereditary cases arise frombenign adenomas [3] and removal of colorectal ade-noma is thought to reduce the risk of subsequentcolorectal cancer by as much as 80% [4]. Therefore,to detect and remove colorectal neoplasms (adeno-mas and carcinomas) has very important role in pre-vention of colorectal cancer death. Colonoscopy isthe most reliable methods to detect colorectal neo-plasms but it has a problem for overlooking ofneplasms [5, 6]. Colorectal cancer after negative co-lonoscopy has been also reported previously [7],although it is uncommon. Therefore, more reliablealternative colonoscopy is anticipated to improve the

prognosis of patients with colorectal cancer. Imageenhanced endoscopy (IEE) is expected to betterdetect adenomas than the conventional white lightimaging (WLI). Chromoendosocopy using indigocarmine, which is one of the dye-based IEE, has cur-rently been an effective procedure for detection ofcolorectal neoplasms [8]. However, as it is somewhatcomplicated and time consuming, its routine use islimited. Equipment-based IEE (e.g. Narrow bandimaging; NBI, autofluorescence imaging; AFI) is ex-pected alternative to chromoendoscopy as simpleand time saving technique. In this review, we intro-duce one of the new diagnostic imaging technologiesthat uses a combination of autofluorescence and re-flection imaging: the AFI video-endoscopy system(Olympus Medical Systems, Tokyo, Japan) and typi-cal image of colorectal cancer using AFI colono-scope.

# 2011 by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

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Autofluorescence imaging (AFI) is expected to betterdetect colorectal neoplasms than the conventional whitelight imaging (WLI). The AFI image of colorectal can-cer is different according to its macroscopic type. Pro-truded lesion, which is the most common macroscopictype of colorectal neoplasms, is revealed as magentaprotruded lesion. Flat lesion, which is uncommon macro-scopic type, is presented as distinct magenta area sur-rounding green mucosa using AFI. And depressed lesion,which is rare macroscopic type, is revealed as green areasurrounded by magenta mucosa.

AFI image of colorectal cancer according to macroscopictype of the lesion (protruded, flat, and depressed type,respectively)

* Corresponding author: e-mail: [email protected], Phone: +81 6 6972 1181, Fax: +81 6 6981 4067

J. Biophotonics 4, No. 7–8, 490–497 (2011) / DOI 10.1002/jbio.201100013

2. Autofluorescence imagingvideo-endoscopy system

2.1 Principle of autofluorescencevideo-endoscopy [9]

When a short wavelength excitation light irradiates asubstance called a fluorophore, that substance emitsa longer wavelength light, that is, fluorescence. Inthe digestive tract, endogeneous fluorophore, suchas collagen, nicotinamide, adenine dinucleotide, fla-vin and porphyrins, exist in both mucosa and sub-mucosa; therefore, they emit a natural tissue fluores-cence called autofluorescence when the excitationlight illuminates the mucosa. AFI video-endoscopysystem produces real-time pseudo-color images fromdetection of the autofluorescence. In the develop-ment and evaluation of fluorescence-based diagnostictechnologies, either autofluorescence or fluorescencecaused by an exogenously administered fluorescentdrug such as 5-aminovulinic acid is used. Becausethe AFI video-endoscopy system only utilizes natur-al tissue fluorescence from an endogenous fluoro-phore, it does not require any drug administration ordye spraying, which may cause adverse effects.

Detection of abnormal lesions by AFI video-endoscopy depends on changes in the concentrationor depth distribution of endogenous fluorophores,changes in the tissue microarchitecture, or both, in-cluding altered mucosal thickness or blood (haemo-globin) concentration, which affect the fluorescenceintensity or spectrum. Autofluorescence is basicallyreduced at the tumors compared with the normalmucosa [10]; possible mechanisms are shown inFigure 1. The differences in the fluorescence fea-

tures, mainly determined by the intensity, are repre-sented as color differences in the AFI video-endo-scopy images.

2.2 Instruments of the autofluorescenceimaging system

Because earlier autofluorescence imaging systemsused a fiberoptic endoscope and a heavy image-in-tensifying camera unit attached to the eyepiece, theyfailed to provide sufficient image quality and ma-neuverability. Thus, they were not suitable for clini-cal use in this video-endoscopy era. The AFI systemuses a dedicated video-endoscope (CF-FH260AZI;Olympus Medical Systems), in which are incorpo-rated two charge-coupled devices (CCDs) for theautofluorescence and white light modes. The scopediameter is 14.8 mm and the tip length is about22 mm. Thus, the appearance of the AFI colono-scope is the same as that of a conventional video-en-doscope and its maneuverability is slightly worse butacceptable compared with conventional colonoscope.Each mode is selected by pressing a small button onthe control head for a few seconds. The AFI is thefirst imaging system that detects autofluorescence bya CCD in the video-endoscope.

In the autofluorescence mode, the excitation lightfor inducting autofluorescence (395–475 nm), andthe narrowband green (G0-) light (550 nm) for re-cording reflection images, were illuminated sequen-tially from the light source through the rotation fil-ter. An excitation light cut filter is incorporated withthe CCD for the autofluorescence mode to permitonly 490- to 625-nm wavelength light to intensity the

Figure 1 (online color at:www.biophotonics-journal.org)Principle of autofluorescence endo-scopy and possible mechanisms ofcolor change.

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CCD. The CCD has especially high sensitivity and itdoes not need image intensification. When theG0-light is illuminated, reflection images are taken.The image processor artificially colors the autofluor-escence images to green, and the green reflectionimage to red and blue, and composite images aredisplayed on the video screen (Figure 2).

The wavelength of G0-light are determined by ab-sorption features of hemoglobin. Normal mucosaemits bright autofluorescence, and thus the compo-site color appears bright green. Because a tumourabsorbs autofluorescence well, it looks magenta,which is the complementary color of green. As he-moglobin absorbs both autofluorescence and G0-light(550 nm), areas containing more microvessels withhemoglobin are displayed as dark green in the AFIimage.

In the white light mode, the light source providesred, green and blue wavelength light sequentiallyby a rotation filter. As the CCD for the white lightmode is the same as that equipped in high-definitionmagnifying colonoscope without AFI (EVIS CF-H260AZI), diagnosis could be made with informa-tion from autofluorescence observation in additionto the high-definition white light video images.

3. Endoscopic features of colorectal cancerusing autofluorescence imaging

3.1 Protruded lesion

Colorectal mucosa without inflammation is basicallypresented as green color using AFI. Protruded lesion

(Paris classification Type 0–I), which is the mostcommon macroscopic type of colorectal neoplasms,is easily detectable with its morphological featureusing WLI. It is presented as magenta protruded le-sion (Figure 3a–d).

3.2 Flat lesion

Flat lesion (Paris classification Type 0–IIa) is un-common macroscopic type of colorectal cancer. Flatlesion is usually similar colored or reddish comparedto surrounding mucosa and sometimes hard to re-cognize. Therefore, it is easily overlooked and willbe cause of interval cancer, which is generally knownas an invasive colorectal cancer that develops in theintervals between negative screening colonoscopyand next screening colonoscopy. Flat lesion is pre-sented as distinct magenta area surrounding greenmucosa using AFI.

3.3 Depressed lesion

Depressed lesion (Paris classification Type 0–IIc) israre macroscopic type of colorectal cancer. De-pressed lesion is thought to arise through the de novopathogenic sequence and demonstrate early invasivecharacteristics. It is difficult to identify depressed le-sion using conventional WLI colonoscopy. We havereported AFI image of a diminutive, depressed-typeearly colon cancer invaded to the submucosal layer[11]. The lesion was revealed as a 5 mm green areasurrounded by magenta mucosa.

Figure 2 (online color at:www.biophotonics-journal.org)Diagram of the autofluorescenceimaging (AFI) system.

Y. Takeuchi et al.: AFI of early CRC492

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# 2011 by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim www.biophotonics-journal.org

4. Discussion

AFI is one of the equipment-based IEE, which canprovide emphasized image of gastrointestinal neo-plasms and is expected to reduce overlooking lesionsduring screening colonoscopy. Chromoendoscopyusing indigo carmine has been also expected to im-prove adenoma detection rate, but it has not been apopular method in clinical practice, because it is toocomplicated and time-consuming for routine clinical

usage. For endoscopists using AFI, all they need isto push the button and wait for a few seconds duringthe examination. It is simple and time saving methodcompared to chromoendoscopy.

Inoue et al. reported the superiority of AFI com-pared to WLI for visualization of the surface appear-ance and difference in color of the lesion and maybe a valuable tool for detection of superficial color-ectal neoplastic lesions [12]. Matsuda et al. reportedthat AFI revealed better detection of flat lesionsthan WLI did in the right-sided colon [13]. The miss

A

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D

C

Figure 3 (online color at: www.biophotonics-journal.org) (A) White light image of protruded lesion in the transverse co-lon. The size was 8 mm. (B) AFI image of protruded lesion in the transverse colon. The lesion was recognized as magentaprotruded lesion. (C) Chromoendoscopic image of protruded lesion in the transverse colon using 0.4% indigo carmine.(D) Microscopic image of endoscopically resected specimen. The lesion invaded into submucosal layer.




rate for all polyps with AFI (30%) was significantlyless than that with WLI (49%) ( p ¼ 0.01). Contraryto these results, we have reported that AFI did notdemonstrate superior efficacy to WLI for detectionof colorectal lesions in the left-sided colon.

The differences between two pilot studies mightbe caused by investigated location in each study. Theimage quality of AFI, i.e. resolution (almost same le-vel compared to thin caliber endoscope), refresh rateand speed of brightness control, is worse than thatof WLI. These are weak points of AFI and neces-sary to maintain an adequate distance from the mu-cosa, observe the colonic mucosa slowly and recog-

nize the color difference between the lesion andthe surrounding mucosa carefully. However it is of-ten difficult to keep an adequate distance from themucosa and colonoscopic movement slow in the nar-row and tortuous sigmoid colon. We supposed thatAFI could not fully realize its ability in the sigmoidcolon. On the other hand, the right sided colon iswider and relatively straighter than the sigmoid co-lon, and might provide more desirable conditions forAFI. Attachment of a transparent hood to the tip ofan AFI colonoscope can maintain an adequate dis-tance to the mucosa and help the CCD to catch theautofluorescence, even in the narrow and tortuous

A

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Figure 4 (online color at: www.biophotonics-journal.org) (A) White light image of flat lesion in the transverse colon. Thelesion is similar coloured with surrounding mucosa. It could not be seen clearly. (B) AFI image of flat lesion in the trans-verse colon. The lesion is presented as distinct magenta area surrounding green mucosa. It could be seen clearly. (C)Chromoendoscopic image of flat lesion in the transverse colon using 0.4% indigo carmine. (D) Microscopic image of en-doscopically resected specimen. The lesion is limited in the mucosal layer.


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sigmoid colon. Now we have attached a transparenthood (D-201-16403; Olympus) to the tip of an AFIcolonoscope during colonoscopy screening [14]. Andwe have reported the efficacy of AFI with a trans-parent hood for detection of colorectal neoplasm intotal colonoscopy [15].

It is known that protruded and flat lesion, whichis the majority of macroscopic type of colorectalneoplasms, is revealed as magenta lesion in greensurrounding mucosa using AFI, but depressed type

colorectal neoplasm is rare and the AFI image of de-pressed type lesion has never been known pre-viously. We have reported the AFI image of de-pressed type early colorectal cancer and it is similarto the AFI image of depressed type early gastriccancer [16], which is revealed as green area sur-rounding normal magenta mucosa. Actually, thiscase was just a case-report, we cannot know that allthe depressed type early colorectal cancer is re-vealed as same as this case, and we don’t have the

A

B

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Figure 5 (A) White light image of depressed lesion in the sigmoid colon. The lesion is similar coloured with surroundingmucosa. It is difficult to detect using conventional colonoscopy. (B) AFI image of depressed lesion in the sigmoid colon.The lesion is presented as green area surrounding magenta mucosa. (C) Chromoendoscopic image of depressed lesion inthe sigmoid colon using 0.4% indigo carmine. (D) Microscopic image of surgically resected specimen. The lesion invadedinto submucosal layer.




data of false negative of AFI. However, this casemaybe important for revealing the possibility of vi-sualization of depressed type colon cancer usingAFI, the possibility of detection for depressed typecolorectal cancer using AFI, and the fact that it wasinvasive cancer nevertheless its small size.

Kulper et al. also reported that AFI could differ-entiate colonic lesions with high levels of sensitivity[17]. So, it may suggest an ability of AFI to discardnon-neoplastic polyp. But, AFI colonoscope is alsoequipped with NBI mode and endoscopist using AFIcolonoscope can utilize NBI mode to discard non-neoplastic polyp. We hope to make a new diagnosticstrategy using IEE (AFI and NBI) in the future.

5. Conclusion

We have reported the AFI image of colorectal neo-plasms according to various macroscopic types. AFIcan provide emphasized image of colorectal neo-plasms and may contribute to reduce overlooking oflesions during screening colonoscopy.

Yoji Takeuchi is Physician inchief at the Department ofGastrointestinal Oncology,Osaka Medical Center forCancer and CardiovascularDiseases. He is Member ofthe Japanese Gastroentero-logical Endoscopy Society,the Japanese Society of In-ternal Medicine and the Ja-panese Society of Gastroen-terology.

Noboru Hanaoka is Staffdoctor at the Department ofGastrointestinal Oncology,Osaka Medical Center forCancer and CardiovascularDiseases.

Masao Hanafusa is SeniorResident at the Departmentof Gastrointestinal Oncol-ogy, Osaka Medical Centerfor Cancer and Cardiovascu-lar Diseases.

Ryu Ishihara is DepartmentManager at the Departmentof Gastrointestinal Oncol-ogy, Osaka Medical Centerfor Cancer and Cardiovascu-lar Diseases.

Koji Higashino is Vice De-partment Manager at theDepartment of Gastrointest-inal Oncology, Osaka Medi-cal Center for Cancer andCardiovascular Diseases.

Hiroyasu Iishi is GeneralManager at the Departmentof Gastrointestinal Oncol-ogy, Osaka Medical Centerfor Cancer and Cardiovascu-lar Diseases.


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Noriya Uedo is Vice De-partment Manager at theDepartment of Gastrointest-inal Oncology, Osaka Medi-cal Center for Cancer andCardiovascular Diseases.




autofluorescence imaging of early colorectal cancer

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