Detection of colonic dysplasia by light-induced fluorescence endoscopy: a pilot study

Vision 20/20: Molecular-guided surgical oncology based upon tumor metabolism or immunologic phenotype: Technological pathways for point of care imaging and intervention

Surgical guidance with fluorescence has been demonstrated in individual clinical trials for decades, but the scientific and commercial conditions exist today for a dramatic increase in clinical value. In the past decade, increased use of indocyanine green based visualization of vascular flow, biliary function, and tissue perfusion has spawned a robust growth in commercial systems that have near-infrared emission imaging and video display capabilities. This recent history combined with major preclinical innovations in fluorescent-labeled molecular probes, has the potential for a shift in surgical practice toward resection guidance based upon molecular information in addition to conventional visual and palpable cues. Most surgical subspecialties already have treatment management decisions partially based upon the immunohistochemical phenotype of the cancer, as assessed from molecular pathology of the biopsy tissue. This phenotyping can inform the surgical resection process by spatial mapping of these features. Further integration of the diagnostic and therapeutic value of tumor metabolism sensing molecules or immune binding agents directly into the surgical process can help this field mature. Maximal value to the patient would come from identifying the spatial patterns of molecular expression in vivo that are well known to exist. However, as each molecular agent is advanced into trials, the performance of the imaging system can have a critical impact on the success. For example, use of pre-existing commercial imaging systems are not well suited to image receptor targeted fluorophores because of the lower concentrations expected, requiring orders of magnitude more sensitivity. Additionally the imaging system needs the appropriate dynamic range and image processing features to view molecular probes or therapeutics that may have nonspecific uptake or pharmacokinetic issues which lead to limitations in contrast. Imaging systems need to be chosen based upon objective performance criteria, and issues around calibration, validation, and interpretation need to be established before a clinical trial starts. Finally, as early phase trials become more established, the costs associated with failures can be crippling to the field, and so judicious use of phase 0 trials with microdose levels of agents is one viable paradigm to help the field advance, but this places high sensitivity requirements on the imaging systems used. Molecular-guided surgery has truly transformative potential, and several key challenges are outlined here with the goal of seeing efficient advancement with ideal choices. The focus of this vision 20/20 paper is on the technological aspects that are needed to be paired with these agents.

Label-free imaging characteristics of colonic mucinous adenocarcinoma using multiphoton microscopy

Colorectal carcinoma (CRC) has high mortality and increased incidence rates. An early detection of CRC is very important. Multiphoton microscopy (MPM) with high resolution and high sensitivity is used to effectively distinguish the microstructure changes of normal and mucinous adenocarcinoma slices of ex vivo human colonic tissues. In mucinous adenocarcinoma mucosa, the glands are distorted and elongated, the gland cavity is indistinct, and the mesh collagen fibers are diminished. In the submucosa, the collagens are seriously disordered, elongated, pushed aside, and sparsely visible, the content of elastic fibers is also broken and almost disappearing. Many cancer cells, some in cavity-like shape full of mucus surrounded by some collagen fibers, occupied the submucosa, which are comparable to hematoxylin-eosin (HE) stained images. Second harmonic generation and two-photon excitation fluorescence (SHG/TPEF) intensity ratio can be used further to quantitatively evaluate normality and abnormality. The fast Fourier transform (FFT) images show that the normal collagen fibrils are dense and in random order, and the cancerous collagen is certainly organized. The exploratory results show that it has potential for the development of multiphoton mini-endoscopy in real-time early diagnosis of CRC.

Assessment of photobleaching during endoscopic autofluorescence imaging of the lower GI tract

BACKGROUND AND OBJECTIVES

In autofluorescence endoscopy, the difference in the fluorescence of intrinsic fluorophores is imaged to help visualize pre-malignant lesions, as in the system evaluated here. In this, blue light is used for excitation and the green autofluorescence is normalized by the red diffuse reflectance and presented using a false color scale. The present study was designed to quantify the degree of fluorescence photobleaching induced by the excitation light during use in the colon, since significant photobleaching could lead to false interpretation of the images, particularly false-positive lesions.

STUDY DESIGN

Measurements were made ex vivo and in vivo, both using the endoscopic imaging system and a separate fiberoptic spectroscopy probe in externalized rat jejunum and in patients undergoing routine colonoscopy, using exposures typical of autofluorescence endoscopic examination.

RESULTS

Photobleaching could be potentially caused at blue light exposure. However, at light intensities and exposure times that are typically used in clinical practice, the average photobleaching (% loss of peak fluorescence intensity) was <1% and <6% in the rat and human tissues, respectively. Nevertheless, the range was large: from -17% to +18% in rats and -33% to +43% in patients, where negative values denote an apparent increase in fluorescence. Both the large positive and negative deviations are believed in part to be due to a measurement artifact caused by uncontrollable tissue motility.

SUMMARY AND CONCLUSIONS

It is concluded that, using exposures typically encountered in clinical practice, there is minimal photobleaching during fluorescence endoscopy at exposure such as are used in the Onco-LIFE and comparable systems. The small changes in fluorescence intensity and spectral shift that do occur are not likely to be detectable by eye, and so should not impact significantly on the diagnostic accuracy of the technique.

Clinical evaluation of endoscopic trimodal imaging for the detection and differentiation of colonic polyps

BACKGROUND & AIMS

Endoscopic trimodal imaging (ETMI) incorporates high-resolution endoscopy (HRE) and autofluorescence imaging (AFI) for adenoma detection, and narrow-band imaging (NBI) for differentiation of adenomas from nonneoplastic polyps. The aim of this study was to compare AFI with HRE for adenoma detection and to assess the diagnostic accuracy of NBI for differentiation of polyps. This was a randomized trial of tandem colonoscopies. The study was performed at the Academic Medical Center in Amsterdam.

METHODS

One hundred patients underwent colonoscopy with ETMI. Each colonic segment was examined twice for polyps, once with HRE and once with AFI, in random order per patient. All detected polyps were assessed with NBI for pit pattern and with AFI for color, and subsequently removed. Histopathology served as the gold standard for diagnosis. The main outcome measures of this study were adenoma miss-rates of AFI and HRE, and diagnostic accuracy of NBI and AFI for differentiating adenomas from nonneoplastic polyps.

RESULTS

Among 50 patients examined with AFI first, 32 adenomas were detected initially. Subsequent inspection with HRE identified 8 additional adenomas. Among 50 patients examined with HRE first, 35 adenomas were detected initially. Successive AFI yielded 14 additional adenomas. The adenoma miss-rates of AFI and HRE therefore were 20% and 29%, respectively (P = .351). The sensitivity, specificity, and overall accuracy of NBI for differentiation were 90%, 70%, and 79%, respectively; corresponding figures for AFI were 99%, 35%, and 63%, respectively.

CONCLUSIONS

The overall adenoma miss-rate was 25%; AFI did not significantly reduce the adenoma miss-rate compared with HRE. Both NBI and AFI had a disappointing diagnostic accuracy for polyp differentiation, although AFI had a high sensitivity.

Detection of colonic dysplasia in vivo using a targeted heptapeptide and confocal microendoscopy

A combination of targeted probes and new imaging technologies provides a powerful set of tools with the potential to improve the early detection of cancer. To develop a probe for detecting colon cancer, we screened phage display peptide libraries against fresh human colonic adenomas for high-affinity ligands with preferential binding to premalignant tissue. We identified a specific heptapeptide sequence, VRPMPLQ, which we synthesized, conjugated with fluorescein and tested in patients undergoing colonoscopy. We imaged topically administered peptide using a fluorescence confocal microendoscope delivered through the instrument channel of a standard colonoscope. In vivo images were acquired at 12 frames per second with 50-microm working distance and 2.5-microm (transverse) and 20-microm (axial) resolution. The fluorescein-conjugated peptide bound more strongly to dysplastic colonocytes than to adjacent normal cells with 81% sensitivity and 82% specificity. This methodology represents a promising diagnostic imaging approach for the early detection of colorectal cancer and potentially of other epithelial malignancies.

Review article: New developments in colonic imaging

BACKGROUND

Colonoscopic detection and removal of neoplasia from the colorectum prevent the development of colorectal cancer. Sporadic adenomas and neoplasia associated with ulcerative colitis are frequently missed during colonoscopy, as a result of which, interval cancers might develop.

AIM

To review new developments in colonoscopic imaging concerning the detection of neoplasia.

METHODS

Medical databases were searched for relevant publications, dealing with advanced endoscopic imaging techniques during colonoscopy.

RESULTS

Pancolonic chromoendoscopy has shown to increase the detection of sporadic adenomas and ulcerative colitis associated neoplasia, at the expense of longer examination times. As chromoendoscopy is labour intensive and time-consuming, its widespread use has been hampered. Narrow band imaging is a novel endoscopic imaging technique, which enhances mucosal and vascular details. Recent studies indicate that narrow band imaging has a high yield for neoplasia; however, no improvement compared to standard colonoscopy has been demonstrated. Autofluorescence imaging is another new technique for which blue endoscopic light is used to induce mucosal autofluorescence. So far, preliminary results have shown promising results of autofluorescence imaging for neoplasia detection.

CONCLUSION

Whether chromoendoscopy or novel advanced imaging techniques will change current colonoscopic practice depends on results of future studies comparing these different colonoscopic techniques.

Optical detection of tumors in vivo by visible light tissue oximetry

Endoscopy is a standard procedure for identifying tumors in patients suspected of having gastrointestinal (G.I.) cancer. The early detection of G.I. neoplasms during endoscopy is currently made by a subjective visual inspection that relies to a high degree on the experience of the examiner. This process can be difficult and unreliable, as tumor lesions may be visually indistinguishable from benign inflammatory conditions and the surrounding mucosa. In this study, we evaluated the ability of local ischemia detection using visible light spectroscopy (VLS) to differentiate neoplastic from normal tissue based on capillary tissue oxygenation during endoscopy. Real-time data were collected (i) from human subjects (N = 34) monitored at various sites during endoscopy (enteric mucosa, malignant, and abnormal tissue such as polyps) and (ii) murine animal subjects with human tumor xenografts. Tissue oximetry in human subjects during endoscopy revealed a tissue oxygenation (StO2%, mean +/- SD) of 46 +/- 22% in tumors, which was significantly lower than for normal mucosal oxygenation (72 +/- 4%; P < or = 0.0001). No difference in tissue oxygenation was observed between normal and non-tumor abnormal tissues (P = N.S.). Similarly, VLS tissue oximetry for murine tumors revealed a mean local tumor oxygenation of 45% in LNCaP, 50% in M21, and 24% in SCCVII tumors, all significantly lower than normal muscle tissue (74%, P < 0.001). These results were further substantiated by positive controls, where a rapid real-time drop in tumor oxygenation was measured during local ischemia induced by clamping or epinephrine. We conclude that VLS tissue oximetry can distinguish neoplastic tissue from normal tissue with a high specificity (though a low sensitivity), potentially aiding the endoscopic detection of gastrointestinal tumors.

Endoscopic fluorescence spectroscopic imaging in the gastrointestinal tract

Fluorescence detection is one of a series of new optical biopsy techniques that have been adapted and evaluated for implementation in gastrointestinal endoscopy. Endogenous fluorescence enables the detection of metabolic and structural changes in human tissue and thus may offer information for the detection of early stage dysplastic and malignant lesions of the mucosa that remain invisible in white light endoscopy. Tissue fluorescence can be detected by point-spectroscopic sampling of the mucosa or by processing the fluorescence information to generate an endoscopic image. Different approaches have been evaluated in pilot studies, and the results in terms of high diagnostic sensitivity and specificity are encouraging. However, large multi-center trials are necessary to evaluate the accuracy and predictability of these new optical tools for the endoscopic diagnosis of early cancerous lesions in the gastrointestinal tract.

Photodynamic diagnosis in the gastrointestinal tract

Clinical data on photodynamic diagnosis for the detection of premalignant and malignant lesions in the gastrointestinal tract are encouraging so far. A major benefit of using autofluorescence is the lack of side effects because no sensitizer has to be applied.However, highly sophisticated detection systems are needed to enhance the weak autofluorescence-based fluorescent signal. New prototypes of autofluorescence video endoscopes are under way and will be decisive for further clinical use, especially because results of recently published studies have been disappointing.

Cytology and image cytometry after colonic lavage: a complementary diagnostic tool in patients with ulcerative colitis

BACKGROUND

Patients with extensive, long-standing ulcerative colitis have increased risk of colorectal cancer.

AIMS

To improve the detection of high-risk patients, using a combination of colonic cytology, histology, and DNA image cytometry after segmental colonic lavage.

PATIENTS

A series of 16 patients (8 high-risk patients) with ulcerative colitis were investigated.

METHODS

After segmental lavage step, biopsies were obtained. Gradient centrifugation of the colonic fluid was performed for isolation and purification of epithelial cells. The smears and biopsy specimens obtained were stained for routine interpretation and for DNA image cytometry.

RESULTS

Segmental lavage could be performed in all patients. Specimens from two high-risk patients showed low grade dysplasia and atypia by means of histology and cytology, respectively. In one patient, without increased colorectal cancer risk, atypia was detected. Three patients in the high-risk group, two of those diagnosed as positive for dysplasia and atypia, showed aneuploidy histologically and cytologically. DNA aneuploidy, in cytological material, was found exclusively in three low-risk patients, one of those had atypia cytologically.

CONCLUSIONS

Isolation and purification of epithelial cells after segmental colonic lavage using density gradient centrifugation can be performed as part of routine endoscopy. It provides information about atypical cells and DNA aneuploidy as additional markers of malignant transformation. The combination of cytologic examination and DNA image cytometry might improve the detection of high-risk ulcerative colitis patients.

Detection of high-grade dysplasia in Barrett's esophagus by spectroscopy measurement of 5-aminolevulinic acid-induced protoporphyrin IX fluorescence

BACKGROUND

Preliminary studies with qualitative detection methods suggest that 5-aminolevulinic acid-induced protoporphyrin IX fluorescence might improve the detection of dysplastic Barrett's epithelium. This study used quantitative methods to determine whether aminolevulinic acid-induced protoporphyrin IX fluorescence can differentiate between Barrett's mucosa with and without dysplasia.

METHODS

Patients were given 10 mg/kg of aminolevulinic acid orally 3 hours before endoscopy. Quantitative fluorescence spectra were acquired by using a nitrogen-pumped dye laser (l 400 nm) spectrograph system. The protoporphyrin IX fluorescence intensity at 635 nm was compared with the histopathologic diagnosis for mucosal biopsy specimens taken immediately after the fluorescence measurements.

RESULTS

Ninety-seven spectra were obtained from 20 patients. The mean (+/- standard error) standardized protoporphyrin IX fluorescence intensity was significantly greater (p < 0.05) for high-grade dysplastic Barrett's epithelium (0.29 +/- 0.07, n = 13) than for nondysplastic Barrett's epithelium (0.11 +/- 0.02, n = 43). By using protoporphyrin IX fluorescence alone, high-grade dysplasia was distinguished from nondysplastic tissue types with 77% sensitivity and 71% specificity. Decreased autofluorescence was particularly found in nodular high-grade dysplasia. By using the fluorescence intensity ratio of 635 nm/480 nm, nodular high-grade dysplasia could be differentiated from nondysplastic tissue with 100% sensitivity and 100% specificity.

CONCLUSION

Protoporphyrin IX fluorescence may be useful for identifying areas of high-grade dysplasia in Barrett's esophagus and for targeting of biopsies.

Pressure dye-spray: a simple and reliable method for differentiating adenomas from hyperplastic polyps in the colon

BACKGROUND

Based on 10 years of experience with chromoendoscopy, our hypothesis was that colonic adenomas can be differentiated from hyperplastic polyps by use of a high-pressure spray-jet of dye (pressure dye-spray). To test the accuracy of pressure dye-spray, classification of colonic polyps as adenomas and hyperplastic polyps by pressure dye-spray and ordinary colonoscopic findings (shape, size, and color surface appearance) were compared.

METHODS

Pressure dye-spray chromoendoscopy was performed by using 0.035% indigo carmine, a spray-type cannula, and a water pump. Polyps were first classified as adenomas or hyperplastic polyps by ordinary colonoscopic findings. One or more pressure dye-spray bursts were then focused on the polyp from a distance of 1 to 2 cm. Polyps were classified as adenomas only if oozing of blood was evident; otherwise, they were classified as hyperplastic polyps. A histologic diagnosis was obtained for all polyps, and the results of ordinary colonoscopic findings and pressure dye-spray were compared.

RESULTS

This study examined 1468 polyps (1201 adenomas, 267 hyperplastic polyps; mean diameter 4 mm). The sensitivities for polyp differentiation with pressure dye-spray and ordinary colonoscopic findings were, respectively, 97.9% and 73.4% (p < 0.0001); specificities were, respectively, 96.6% and 92.1% (p = 0.077).

CONCLUSIONS

Pressure dye-spray was found to be a reliable technique for differentiation between adenomas and hyperplastic polyps.

Receptor-targeted optical imaging of tumors with near-infrared fluorescent ligands

We report here the in vivo diagnostic use of a peptide-dye conjugate consisting of a cyanine dye and the somatostatin analog octreotate as a contrast agent for optical tumor imaging. When used in whole-body in vivo imaging of mouse xenografts, indotricarbocyanine-octreotate accumulated in tumor tissue. Tumor fluorescence rapidly increased and was more than threefold higher than that of normal tissue from 3 to 24 h after application. The targeting conjugate was also specifically internalized by primary human neuroendocrine tumor cells. This imaging approach, combining the specificity of ligand/receptor interaction with near-infrared fluorescence detection, may be applied in various other fields of cancer diagnosis.