Fluorescence Colonoscopy Research Articles

Biomolecular imaging of colorectal tumor lesions using a FITC-labeled scFv-C\u03ba fragment antibody

For the sensitive diagnosis of colorectal cancer lesions, advanced molecular imaging techniques using cancer-specific targets have emerged. However, issues regarding the clearance of unbound probes and immunogenicity remain unresolved. To overcome these limitations, we developed a small-sized scFv antibody fragment conjugated with FITC for the real-time detection of colorectal cancer by in vivo molecular endoscopy imaging. A small-sized scFv fragment can target colon cancer secreted protein-2 (CCSP-2), highly expressed in colorectal adenocarcinoma tissues; moreover, its full-length IgG probe has been used for molecular imaging previously. To assess the efficacy of anti-CCSP-2 scFv-FITC, surgical specimens were obtained from 21 patients with colorectal cancer for ex vivo molecular fluorescence analysis, histology, and immunohistochemistry. Orthotopic mice were administered with anti-CCSP-2 scFv-FITC topically and intravenously, and distinct tumor lesions were observed by real-time fluorescence colonoscopy. The fluorescence imaging of human colon cancer specimens allowed the differentiation of malignant tissues from non-malignant tissues (p < 0.05), and the CCSP-2 expression level was found to be correlated with the fluorescence intensity. Here, we demonstrated the feasibility and safety of anti-CCSP-2 scFv-FITC for molecular imaging as well as its potential in real-time fluorescence colonoscopy for the differential diagnosis of tumor lesions.

Detection of colorectal dysplasia using fluorescently labelled lectins.

Colorectal cancer screening using conventional colonoscopy lacks molecular information and can miss dysplastic lesions. We tested here the ability of fluorescently labelled lectins to distinguish dysplasia from normal tissue when sprayed on to the luminal surface epithelium of freshly resected colon tissue from the Apcmin mouse and when applied to fixed human colorectal tissue sections. Wheat germ agglutinin (WGA) showed significantly decreased binding to adenomas in the mouse tissue and in sections of human colon from 47 patients. Changes in WGA binding to the human surface epithelium allowed regions containing normal epithelium (NE) or hyperplastic polyps (HP) to be distinguished from regions containing low-grade dysplasia (LGD), high-grade dysplasia (HGD) or carcinoma (C), with 81% sensitivity, 87% specificity and 93% positive predictive value (PPV). Helix pomatia agglutinin (HGA) distinguished epithelial regions containing NE from regions containing HP, LGD, HGD or C, with 89% sensitivity, 87% specificity and 97% PPV. The decreased binding of WGA and HPA to the luminal surface epithelium in human dysplasia suggests that these lectins may enable more sensitive detection of disease in the clinic using fluorescence colonoscopy.

Molecular Fluorescence Endoscopy Targeting Vascular Endothelial Growth Factor A for Improved Colorectal Polyp Detection

Small and flat adenomas are known to carry a high miss-rate during standard white-light endoscopy. Increased detection rate may be achieved by molecular fluorescence endoscopy with targeted near-infrared (NIR) fluorescent tracers. The aim of this study was to validate vascular endothelial growth factor A (VEGF-A) and epidermal growth factor receptor (EGFR)-targeted fluorescent tracers during ex vivo colonoscopy with an NIR endoscopy platform. VEGF-A and EGFR expression was determined by immunohistochemistry on a large subset of human colorectal tissue samples--48 sessile serrated adenomas/polyps, 70 sporadic high-grade dysplastic adenomas, and 19 hyperplastic polyps--and tissue derived from patients with Lynch syndrome--78 low-grade dysplastic adenomas, 57 high-grade dysplastic adenomas, and 31 colon cancer samples. To perform an ex vivo colonoscopy procedure, 14 mice with small intraperitoneal EGFR-positive HCT116(luc) tumors received intravenous bevacizumab-800CW (anti-VEGF-A), cetuximab-800CW (anti-EGFR), control tracer IgG-800CW, or sodium chloride. Three days later, 8 resected HCT116(luc) tumors (2-5 mm) were stitched into 1 freshly resected human colon specimen and followed by an ex vivo molecular fluorescence colonoscopy procedure. Immunohistochemistry showed high VEGF-A expression in 79%-96% and high EGFR expression in 51%-69% of the colorectal lesions. Both targets were significantly overexpressed in the colorectal lesions, compared with the adjacent normal colon crypts. During ex vivo molecular fluorescence endoscopy, all tumors could clearly be delineated for both bevacizumab-800CW and cetuximab-800CW tracers. Specific tumor uptake was confirmed with fluorescent microscopy showing, respectively, stromal and cell membrane fluorescence. VEGF-A is a promising target for molecular fluorescence endoscopy because it showed a high protein expression, especially in sessile serrated adenomas/polyps and Lynch syndrome. We demonstrated the feasibility to visualize small tumors in real time during colonoscopy using a NIR fluorescence endoscopy platform, providing the endoscopist a wide-field red-flag technique for adenoma detection. Clinical studies are currently being performed in order to provide in-human evaluation of our approach.

Colorectal cancer: An intravenous probe for colorectal cancer screening.

Early detection of colorectal lesions is the cornerstone of cancer prevention. Intravenous administration of a novel fluorescent peptide probe now enables the screening of the whole colorectal area using near-infrared fluorescence colonoscopy, an approach that was documented as safe, well-tolerated and specific in its detection of colorectal polyps.

2158 The Nationwide Cancer Genome Screening Project for Gastrointestinal Cancer in Japan (GI-SCREEN): Simultaneous identification of KRAS, NRAS, BRAF, and PIK3CA mutation in advanced colorectal cancer (aCRC) (GI-SCREEN 2013-01)

resection (11.7%). Colon histological sections were stained with fluorescently labeled lectins, and the lectin binding to surface epithelium, which would be observable in colonoscopy, was compared with conventional histopathology for the presence of disease and disease stage. Results: Normal colonic epithelium (NE) occupied 40.1% of the area of all sections, hyperplastic polyps (HP) occupied 10.2%, low-grade (LGD) dysplasia 25.6%, high-grade (HGD) dysplasia 13.9%, and adenocarcinoma (C) 10.2%, as assessed by conventional histopathology based on H&E staining. Lesions were located in the ascending (10.4%), transverse (15.6%), descending (14.3%), sigmoid (42.9%) colon and rectum (7.8%), with the mean lesion size being 16.0±14.2mm (range 2−60mm). The lectin wheat germ agglutinin (WGA), when fluorescently-labeled, was capable of distinguishing epithelial regions containing NE or HP from regions containing LGD, HGD or cancer, with 81% sensitivity and 87% specificity. Conclusions: Automated analysis of fluorescently-labeled WGA binding to the surface epithelium of excised colon sections may be used for improving the assessment of early dysplasia in CRC. The same fluorescent lectin may also be useful as a topical imaging agent for improving detection of early dysplasia using fluorescence colonoscopy, increasing the early diagnosis of CRC and improving patient survival. No conflict of interest.

Abstract LB-122: molecular imaging of early colorectal dysplasia using fluorescently-labeled lectins

Abstract Objective Screening for colorectal cancer (CRC) is currently performed using bright-field colonoscopy, which has low specificity and sensitivity for the detection of early dysplasia in the colon. Fluorescently labeled lectins have been applied topically for detecting glycosylation changes in early dysplastic lesions in the esophagus, providing a route for improved endoscopic detection using fluorescence endoscopy [1]. We have identified here fluorescently labeled lectins that can detect changes in glycosylated biomarkers on the surface epithelium of early dysplasia in CRC. These probes may enable fluorescence-guided resection of dysplastic lesions at colonoscopy and subsequent automated assessment of colon histopathology. Study Design Ninety-nine colon lesions in 48 patients (34 males, 14 females; mean patient age 68.8 ± 8.3 yr, range 53-95 yr) were identified during routine colonoscopy at Addenbrooke's Hospital, Cambridge, UK. Lesions suspected of being dysplastic or neoplastic, were detected using magnification colonoscopy or surgery, and removal performed at biopsy (11.7%) and/or polypectomy (62.1%), or partial colon resection (11.7%). Colon histological sections were stained with fluorescently labeled lectins, and the lectin binding to surface epithelium, which would be observable in colonoscopy, was compared with conventional histopathology for the presence of disease and disease stage. Results Normal colonic epithelium (NE) occupied 40.1% of the area of all sections, hyperplastic polyps (HP) occupied 10.2%, low- (LGD) dysplasia 25.6%, high-grade (HGD) dysplasia 13.9%, and adenocarcinoma (C) 10.2%, as assessed by conventional histopathology based on H&amp;E staining. Lesions were located in the ascending (10.4%), transverse (15.6%), descending (14.3%), sigmoid (42.9%) colon and rectum (7.8%), with the mean lesion size being 16.0 ± 14.2 mm (range 2-60 mm). The lectin wheat germ agglutinin (WGA), when fluorescently-labeled, was capable of distinguishing epithelial regions containing NE from regions containing LGD, HGD and cancer, with &amp;gt;81% sensitivity, &amp;gt;79% specificity and &amp;gt;93% positive predictive value. Conclusions Automated analysis of fluorescently-labeled WGA binding to the surface epithelium of excised colon sections may be used for improving the assessment of early dysplasia in CRC. The same fluorescent lectin may also be useful as a topical imaging agent for improving detection of early dysplasia using fluorescence colonoscopy, increasing the early diagnosis of CRC and improving patient survival.

Detection of colorectal polyps in humans using an intravenously administered fluorescent peptide targeted against c-Met.

Colon cancer prevention currently relies on colonoscopy using white light to detect and remove polyps, but small and flat polyps are difficult to detect and frequently missed when using this technique. Fluorescence colonoscopy combined with a fluorescent probe specific for a polyp biomarker may improve polyp detection. Here we describe GE-137, a water-soluble probe consisting of a 26-amino acid cyclic peptide that binds the human tyrosine kinase c-Met conjugated to a fluorescent cyanine dye. Intravenous administration of GE-137 leads to its accumulation specifically in c-Met-expressing tumors in mice, and it is safe and well tolerated in humans. Fluorescence colonoscopy in patients receiving intravenous GE-137 enabled visualization of all neoplastic polyps that were visible with white light (38), as well as an additional nine polyps that were not visible with white light. This first-in-human pilot study shows that molecular imaging using an intravenous fluorescent agent specific for c-Met is feasible and safe, and that it may enable the detection of polyps missed by other techniques.

P-222 Detection of colorectal dysplasia using fluorescently-labeled lectins

Introduction: Early detection of colorectal cancer is based currently on white light colonoscopy. However, diminutive and flat lesions may be frequently missed, particularly in the proximal colon where these lesions are typically advanced and require a more effective screening tool. We describe here the use of fluorescently labeled lectins targeting glycosylated biomarkers of dysplasia on the luminal surface epithelium, which may enable automated histological assessment of biopsies and fluorescence-guided resection at colonoscopy. Methods: Colonoscopy identified 99 colorectal lesions in 48 patients. Biopsy and/or polypectomy, or partial colon resection were performed for suspected neoplastic lesions. Formalin-fixed-paraffin-embedded materials derived from these lesions were studied. Binding of fluorescently-labeled lectins to the luminal surface epithelium observable in colonoscopy was compared with histological assessment. Fluorescence intensity and chemical stains for mucins were analysed quantitatively, allowing consistent and standardised quantitative comparisons across samples. Results: Normal epithelium (NE) occupied 40.1% of the area of the tissue sections, with hyperplastic polyps (HP) occupying 10.2%, low-grade (LGD) dysplasia 25.6%, high-grade (HGD) dysplasia 13.9%, and carcinoma (C) 10.2%. Fluorescent lectin histochemistry showed that wheat germ agglutinin (WGA) and Helix pomatia agglutinin (HPA) decreased their binding in the progression to cancer (P < 0.001, Jonckheere's trend analysis) and could distinguish epithelial regions containing NE from regions containing LGD, HGD or C (sensitivity and specificity: 81% and 79% for WGA; 85% and 89% for HPA, respectively). The same pattern was observed previously in our lab using fluorescent lectins to aid the endoscopic identification of dysplasia in Barrett's oesophagus (Bird-Lieberman, E.L., et al., Nat Med, 2012. 18(2): p. 315-21). Remarkably, WGA can distinguish hyperplasia from regions containing LGD, HGD or C with 100% sensitivity and specificity in our dataset. A strong linear correlation was observed between WGA binding and alcian blue staining (R = 0.79, P < 0.0001), consistent with the specificity of WGA for acidic glycans. Conclusion: Analysis of fluorescently-labeled lectin binding, in particular WGA, to the luminal surface epithelium of excised colorectal tissue sections may be automated for improved assessment of colonic dysplasia. Fluorescently-labeled WGA may also be a useful tool for improving detection of dysplasia using fluorescence colonoscopy. Figure: P-222

Abstract 4101: Early detection of colonic neoplasia using fluorescence microendoscopy

Abstract Purpose: The objective of this research is to integrate nanotechnology with molecular imaging for early detection of colorectal cancer (CRC). CRC undergoes a protracted asymptomatic stage before it reaches the advance stage. Therefore, detection in the early onset through regular screening will improve therapeutic outcomes and save lives. In that regard, colonoscopy is considered the golden standard for early detection. However, its effectiveness for early detection of tumor growth is mitigated by its incapacity to disclose molecular level changes. Recent studies have reported the miss rate for this tumor size-dependent technique is as high as 20% for polyps. One molecule associated with the development and progress of CRC is the Thomsen-Friedenreich (TF) antigen (Ag). High expression of TF disaccharide in CRC and its absence from normal tissue represents a unique association in CRC that exhibits the qualities of a prognostic biomarker. Method: We developed a fluorescence (FL) nanobeacon, which can bind specifically to TF-associated CRC due the presence of multiple identical copies of peanut agglutinin (PNA) molecules derivatized on the surface of the nanobeacon. The physical property of the FL nanobeacon such as size, shape, surface topography, elemental composition and polymer distribution was evaluated using dynamic light scattering, scanning electron microscopy, X-ray photoelectron spectroscopy and permeation chromatography, respectively. We assessed the sensitivity and specificity of the nanobeacon on human specimens using FL microscopy, Western blot and quantitative PCR. TF Imaging data was validated by depletion of TF expression employing a glycanase assay. In addition, we developed an orthotopic rat model of CRC using Athymic nude rats to assess the specificity of the nanobeacon using white light colonoscopy and FL microendoscopy. Furthermore, the biodistribution of the nanobeacon was assessed using an orthotopic mouse model. Results: The overall size of the nanobeacon is approximately 350 nm. It contains 0.05% coumarin 6 dye in the polystyrene center core. There are approximately 200-300 PNA molecules, which serve as molecular recognition moieties for TF Ag. The nanobeacon specifically reported CRC by recognizing the tumor-specific Ag through surface-immobilized PNA. Removal of TF from human colorectal cancer cells and tissues resulted in a significant loss of FL signal, which suggests the specificity of the probe. In vivo imaging data demonstrated that the FL colonoscopy using the nanobeacon can detect CRC much earlier than conventional colonoscopy. Finally, biodistribution study showed that the nanobeacon is not absorbed by colonic mucosa upon being sprayed topically, thus there is no register toxicity associated with this probe. Conclusion: We demonstrated the potential use of a novel nanobeacon for early detection of CRC. Data obtained in this work suggests that TF Ag can be used as a potential biomarker for imaging CRC. Citation Format: Wellington Pham, Hironori Kumagai, Ken-Ichiro Hiwatari, Seiji Koike, Etsuo Tobita, Tokio Kitamura, Kohta Mohri, Shinji Sakuma. Early detection of colonic neoplasia using fluorescence microendoscopy. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 4101. doi:10.1158/1538-7445.AM2014-4101

Fluorescence-based endoscopic imaging of Thomsen-Friedenreich antigen to improve early detection of colorectal cancer.

Thomsen-Friedenreich (TF) antigen belongs to the mucin-type tumor-associated carbohydrate antigen. Notably, TF antigen is overexpressed in colorectal cancer (CRC) but is rarely expressed in normal colonic tissue. Increased TF antigen expression is associated with tumor invasion and metastasis. In this study, we sought to validate a novel nanobeacon for imaging TF-associated CRC in a preclinical animal model. We developed and characterized the nanobeacon for use with fluorescence colonoscopy. In vivo imaging was performed on an orthotopic rat model of CRC. Both white light and fluorescence colonoscopy methods were utilized to establish the ratio-imaging index for the probe. The nanobeacon exhibited specificity for TF-associated cancer. Fluorescence colonoscopy using the probe can detect lesions at the stage which is not readily confirmed by conventional visualization methods. Further, the probe can report the dynamic change of TF expression as tumor regresses during chemotherapy. Data from this study suggests that fluorescence colonoscopy can improve early CRC detection. Supplemented by the established ratio-imaging index, the probe can be used not only for early detection, but also for reporting tumor response during chemotherapy. Furthermore, since the data obtained through in vivo imaging confirmed that the probe was not absorbed by the colonic mucosa, no registered toxicity is associated with this nanobeacon. Taken together, these data demonstrate the potential of this novel probe for imaging TF antigen as a biomarker for the early detection and prediction of the progression of CRC at the molecular level.

Fluorescence Diagnostics of Colon Malignant and Premalignant Lesions Using 5-Aminolevulinic Acid

Improvement of colon cancer diagnosis is a very important medical problem. Methods of fluorescence diagnosis (FD) with 5-aminolevulinic acid (5-ALA) have been used in detection of early cancer on the surface of mucosa. The objective of the study was to estimate the effectiveness of FD with 5-ALA in the detection of malignant lesions in the colon. From 2008 to 2010 full examinations have been performed in 78 patients suffering from colon polyps. For the study we used drug Alasens based on 5-ALA. Fluorescence colonoscopy with Alasens was made using the visual assessment of fluorescence images in combination with local fluorescence spectroscopy. The results of FD were compared with those of final histopathological study. The application of the method during colonoscopy allows specifying diagnosis, identifying areas of colon tumors transformation, and also showing a place for targeted biopsy. Sensitivity and specificity of FD with Alasens were 94.9% and 62.5%, respectively. The application of local fluorescence spectroscopy as a step of the combined approach allows increasing the specificity of fluorescence colonoscopy from 62.5% up to 93.7%.

Fluorescence Endoscopy of Cathepsin Activity Discriminates Dysplasia from Colitis

Surveillance colonoscopy using random biopsies to detect colitis-associated cancer (CAC) suffers from poor sensitivity. Although chromoendoscopy improves detection, acceptance in the community has been slow. Here, we examine the usefulness of near infrared fluorescence (NIRF) endoscopy to image molecular probes for cathepsin activity in colitis-induced dysplasia. In patient samples, cathepsin activity was correlated with colitis and dysplasia. In mice, cathepsin activity was detected as fluorescent hydrolysis product of substrate-based probes after injection into Il10(-/-) colitic mice. Fluorescence colonoscopy and colonic whole-mount imaging were performed before complete sectioning and pathology review of resected colons. Cathepsin activity was 5-fold and 8-fold higher in dysplasia and CAC, respectively, compared with areas of mild colitis in patient tissue sections. The signal-to-noise ratios for dysplastic lesions seen by endoscopy in Il10(-/-) mice were 5.2 ± 1.3 (P = 0.0001). Lesions with increased NIRF emissions were classified as raised or flat dysplasia, lymphoid tissue, and ulcers. Using images collected by endoscopy, a receiver operating characteristic curve for correctly diagnosing dysplasia was calculated. The area under the curve was 0.927. At a cutoff of 1000 mean fluorescence intensity, the sensitivity and specificity for detecting dysplasia were 100% and 83%, respectively. Analysis revealed that focally enhanced NIRF emissions derived from increased numbers of infiltrating myeloid-derived suppressor cells and macrophages with equivalent cathepsin activity. These studies indicate that cathepsin substrate-based probe imaging correctly identifies dysplastic foci within chronically inflamed colons. Combined white light and NIRF endoscopy presents unique advantages that may increase sensitivity and specificity of surveillance colonoscopy in patients with CAC.

Fluorescence diagnosis using 5-aminolevulinic acid in coloproctology/Fluoreszenz-Diagnostik in der Koloproktologie mittels 5-Aminolävulinsäure

AbstractMethods of fluorescence diagnosis (FD) with 5-aminolevulinic acid (5-ALA) have frequently been used for the detection of early cancer on the surface of the mucosa and skin. The objective of this study was to estimate the effectiveness of FD using Alasens (5-ALA) for the detection of malignant lesions in the colon.In the article, our experience of fluorescence colonoscopy is represented using Alasens (5-ALA) in 78 patients with colonic polyps. FD was performed using the visual assessment of fluorescence images in combination with local fluorescence spectroscopy.The sensitivity and specificity of FD with Alasens was 94.9% and 62.5%, respectively. The application of local fluorescence spectroscopy as a step of the combined approach allows the specificity to be increased from fluorescence colonoscopy from 62.5% up to 93.7%.

In Vivo Optical Molecular Imaging of Matrix Metalloproteinase Activity following Celecoxib Therapy for Colorectal Cancer

We present an optical molecular imaging approach to measure the efficacy of the cyclooxygenase-2 (COX-2) inhibitor celecoxib on tumor growth rate through its effect on matrix metalloproteinase (MMP) activity. A xenograft model of colorectal cancer was generated in nude mice, which were then randomized to receive celecoxib versus vehicle. MMP activity was measured by an enzyme-activatable optical molecular probe. A novel genetically engineered mouse (GEM) model of colorectal cancer was also used to assess celecoxib's effect on MMP activity, which was measured by quantitative fluorescence colonoscopy. Subcutaneously implanted xenograft tumors were 84% (SD 20.2%) smaller in volume in the treatment group versus the control group. Moreover, treated animals exhibited only a 7.6% (SEM 9%) increase in MMP activity versus 106% (SEM 8%) for untreated animals. There was an apparent linear relationship (r = .91) between measured MMP activity and tumor growth rate. Finally, in the GEM model experiment, treated murine tumors remained relatively unchanged in volume and MMP activity; however, untreated tumors grew significantly and showed an increase in MMP activity. This method may provide for the improved identification of patients for whom COX-2 inhibition therapy is indicated by allowing one to balance the patient's cardiovascular risk with the cancer's responsiveness to celecoxib.

Fluorescence endoscopic detection of murine colitis-associated colon cancer by topically applied enzymatically rapid-activatable probe

ObjectivesScreening colonoscopy to monitor for early colitis-associated colon cancer (CAC) is difficult due to the aberrant mucosal patterns associated with long-standing colitis. The aim of this study was to develop...

Hexaminolevulinate-induced fluorescence colonoscopy versus white light endoscopy for diagnosis of neoplastic lesions in the colon

To compare the rate of detection of colorectal neoplastic lesions using the selective photosensitizer precursor hexaminolevulinate (HAL) combined with a new fluorescence video endoscope system against that of standard white light endoscopy, and secondarily, to evaluate the safety profile of HAL-induced fluorescence colonoscopy. This prospective phase II clinical pilot study from two hospital study centers included 25 patients with known or highly suspected colorectal neoplasia. They underwent sensitization with locally applied 500 ml HAL enemas at a concentration of 1.6 mmol/L. At 60 minutes after enteral HAL administration, fluorescence imaging was done using a special light source capable of delivering either white light or blue excitation light. Red fluorescence induced by illumination with blue light was detected via a prototype fluorescence video colonoscope. Biopsies were taken from suspicious areas found with white or blue light. Using histology as the gold standard, 55 / 93 of neoplastic lesions were detected with white light endoscopy, 53 / 93 with both white and blue light, 38 / 93 with blue light and second-pass white light, and 27/93 with blue light only. Of all neoplastic lesions, 91 / 93 revealed red fluorescence under fluorescence imaging ( P < 0.0001). Fluorescence mode showed 38.7 % (36 / 93) more neoplasms than did white light endoscopy. An isolated slight elevation of bilirubin, by a factor of 1.5, was noted after the administration of HAL. Administration of HAL as enema induces selective lesion fluorescence and increases lesion detection rate in patients with colorectal neoplasia, especially of flat, nonvisible adenomas.

Commentaire de travail de B. Mayinger et al., pp. 28

See also: Hexaminolevulinate-induced fluorescence colonoscopy versus white light endoscopy for diagnosis of neoplastic lesions in the colonEndoscopy 2010; 42(01): 28-33DOI: 10.1055/s-0029-1243804

Evaluation and clinically relevant applications of a fluorescent imaging analog to fluorodeoxyglucose positron emission tomography

A fluorescent analog to 2-deoxy-2 [(18)F] fluoro-D-glucose position emission tomography (FDG-PET) would allow for the introduction of metabolic imaging into intraoperative and minimally invasive settings. We present through in vitro and in vivo experimentation an evaluation of 2-(N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)amino)-2-deoxyglucose (2-NBDG), a fluorescently labeled glucose molecule, as a molecular beacon of glucose utilization. The competitive inhibition of 2-NBDG uptake by excess free glucose is directly compared against FDG uptake inhibition in cultured cells. 2-NBDG uptake in the brain of a mouse experiencing a generalized seizure is measured, as well as in subcutaneously implanted tumors in mice during fed and fasting states. Localization of 2-NBDG into malignant tissues is studied by laser scanning microscopy. The clinical relevance of 2-NBDG imaging is examined by performing fluorescence colonoscopy, and by correlating preoperative FDG-PET with intraoperative fluorescence imaging. 2-NBDG exhibits a similar uptake inhibition to FDG by excess glucose in the growth media. Uptake is significantly increased in the brain of an animal experiencing seizures versus control, and in subcutaneous tumors after the animals are kept nil per os (NPO) for 24 h versus ad libitum feeding. The clinical utility of 2-NBDG is confirmed by the demonstration of very high target-to-background ratios in minimally invasive and intraoperative imaging of malignant lesions. We present an optical analog of FDG-PET to extend the applicability of metabolic imaging to minimally invasive and intraoperative settings.

Low Frequency of Colorectal Dysplasia in Patients with Long-Standing Inflammatory Bowel Disease Colitis: Detection by Fluorescence Endoscopy

Patients with long-standing inflammatory bowel disease (IBD) have an increased risk of developing colonic dysplasias. Dysplastic changes in flat mucosa are likely to be missed by conventional colonoscopy. Endoscopic fluorescence imaging, using 5-aminolevulinic acid (5-ALA) as photosensitizer, has evolved as a new technique to differentiate between normal colonic mucosa and dysplasia. We combined this technique with random biopsies to prospectively evaluate the occurrence of dysplasias in patients with long-standing IBD. 52 colonoscopies were performed in 42 consecutive patients (n = 28 with ulcerative colitis, n = 11 with Crohn's colitis, n = 3 with indeterminate colitis; mean age 43 years, range 21 - 78) with long-standing IBD colitis (median disease duration 14 years, range 3 - 40). All patients were in clinical remission. Patients were examined using both conventional white light and by fluorescence colonoscopy using oral 5-ALA. Four biopsies were taken every 10 cm from mucosa of normal appearance. In addition, macroscopically suspicious and fluorescence-positive areas were biopsied. A total of 688 biopsies of red-fluorescent (n = 20) and nonfluorescent (n = 662) areas of mucosa were taken. Dysplasia was detected histopathologically in only two of the biopsies. These biopsies were taken from two polypoid lesions which were fluorescence-negative. The rate of colonic dysplasia in patients with long-standing IBD colitis may be lower than previously reported.