The histological basis of detection of adenoma and cancer in the colon by autofluorescence endoscopic imaging

Detection and characterization of colorectal cancer by autofluorescence lifetime imaging on surgical specimens

Colorectal cancer (CRC) ranks among the most prevalent malignancies worldwide, driving a quest for comprehensive characterization methods. We report a characterization of the ex vivo autofluorescence lifetime fingerprint of colorectal tissues obtained from 73 patients that underwent surgical resection. We specifically target the autofluorescence characteristics of collagens, reduced nicotine adenine (phosphate) dinucleotide (NAD(P)H), and flavins employing a fiber-based dual excitation (375 nm and 445 nm) optical imaging system. Autofluorescence-derived parameters obtained from normal tissues, adenomatous lesions, and adenocarcinomas were analyzed considering the underlying clinicopathological features. Our results indicate that differences between tissues are primarily driven by collagen and flavins autofluorescence parameters. We also report changes in the autofluorescence parameters associated with NAD(P)H that we tentatively attribute to intratumoral heterogeneity, potentially associated to the presence of distinct metabolic subpopulations. Changes in autofluorescence signatures of malignant tumors were also observed with lymphatic and venous invasion, differentiation grade, and microsatellite instability. Finally, we characterized the impact of radiative treatment in the autofluorescence fingerprints of rectal tissues and observed a generalized increase in the mean lifetime of radiated adenocarcinomas, which is suggestive of altered metabolism and structural remodeling. Overall, our preliminary findings indicate that multiparametric autofluorescence lifetime measurements have the potential to significantly enhance clinical decision-making in CRC, spanning from initial diagnosis to ongoing management. We believe that our results will provide a foundational framework for future investigations to further understand and combat CRC exploiting autofluorescence measurements.

Stomach tissue classification using autofluorescence spectroscopy and machine learning

BACKGROUND AND OBJECTIVES

Determination of stomach tumor location and invasion depth requires delineation of gastric histological structure, which has hitherto been widely accomplished by histochemical staining. In recent years, alternative histochemical evaluation methods have been pursued to accelerate intraoperative diagnosis, often by bypassing the time-consuming step of dyeing. Owing to strong endogenous signals from coenzymes, metabolites, and proteins, autofluorescence spectroscopy is a favorable candidate technique to achieve this aim.

MATERIALS AND METHODS

We investigated stomach tissue slices and block specimens using a fast fluorescence imaging scanner. To obtain histological information from broad and structureless fluorescence spectra, we analyzed tens of thousands of spectra with multiple machine-learning algorithms and built a tissue classification model trained with dissected gastric tissues.

RESULTS

A machine-learning-based spectro-histological model was built based on the autofluorescence spectra measured from stomach tissue samples with delineated and validated histological structures. The scores from a principal components analysis were employed as input features, and prediction accuracy was confirmed to be 92.0%, 90.1%, and 91.4% for mucosa, submucosa, and muscularis propria, respectively. We investigated the tissue samples in both sliced and block forms using a fast fluorescence imaging scanner.

CONCLUSION

We successfully demonstrated differentiation of multiple tissue layers of well-defined specimens with the guidance of a histologist. Our spectro-histology classification model is applicable to histological prediction for both tissue blocks and slices, even though only sliced samples were trained.

Recent Advances and the Potential for Clinical Use of Autofluorescence Detection of Extra-Ophthalmic Tissues

The autofluorescence (AF) characteristics of endogenous fluorophores allow the label-free assessment and visualization of cells and tissues of the human body. While AF imaging (AFI) is well-established in ophthalmology, its clinical applications are steadily expanding to other disciplines. This review summarizes clinical advances of AF techniques published during the past decade. A systematic search of the MEDLINE database and Cochrane Library databases was performed to identify clinical AF studies in extra-ophthalmic tissues. In total, 1097 articles were identified, of which 113 from internal medicine, surgery, oral medicine, and dermatology were reviewed. While comparable technological standards exist in diabetology and cardiology, in all other disciplines, comparability between studies is limited due to the number of differing AF techniques and non-standardized imaging and data analysis. Clear evidence was found for skin AF as a surrogate for blood glucose homeostasis or cardiovascular risk grading. In thyroid surgery, foremost, less experienced surgeons may benefit from the AF-guided intraoperative separation of parathyroid from thyroid tissue. There is a growing interest in AF techniques in clinical disciplines, and promising advances have been made during the past decade. However, further research and development are mandatory to overcome the existing limitations and to maximize the clinical benefits.

Feasibility Study on Discrimination of Neo-plastic and Non-Neoplastic Gastric Tissues Using Spark Discharge Assisted Laser Induced Breakdown Spectroscopy

Introduction: The present work is a novel in vitro study that evaluated the possibility of diagnosing neoplastic from nonneoplastic gastric tissues using spark discharge assisted laser induced breakdown spectroscopy (SD-LIBS) method. Methods: In these experiments, the low energy laser pulses ablated a tiny amount of tissue surface leading to plasma formation. Then, a spark discharge was applied to plasma in order to intensify the plasma radiation. Light emission from plasma was recorded as spectra which were analyzed. Gastric tissues of 5 people were studied through this method. Results: The SD-LIBS technique had the potential to discriminate normal and cancerous tissues based on the significant differences in the intensities of some particular elements. The comparison of normalized calcium (Ca) and magnesium (Mg) peaks of neoplastic and nonneoplastic gastric tissues could be viewed as a practical measure for tissue discrimination since Ca and Mg peaks in spectra of neoplastic were noticeably higher than nonneoplastic. Conclusion: Considering the identification of gastric cancer, the applied method in these experiments seems quite fast, noninvasive and cost-effective with respect to other conventional methods. The significant increment of specific Ca and Mg lines of neoplastic gastric tissues in comparison to the nonneoplastic ones can be considered as valuable information that might bring about tissue classification. The number of samples in this work, however, was not sufficient for a decisive conclusion and further researches is needed to generalize this idea.

Hyperspectral imaging fluorescence excitation scanning for colon cancer detection

Optical spectroscopy and hyperspectral imaging have shown the potential to discriminate between cancerous and noncancerous tissue with high sensitivity and specificity. However, to date, these techniques have not been effectively translated to real-time endoscope platforms. Hyperspectral imaging of the fluorescence excitation spectrum represents new technology that may be well suited for endoscopic implementation. However, the feasibility of detecting differences between normal and cancerous mucosa using fluorescence excitation-scanning hyperspectral imaging has not been evaluated. The goal of this study was to evaluate the initial feasibility of using fluorescence excitation-scanning hyperspectral imaging for measuring changes in fluorescence excitation spectrum concurrent with colonic adenocarcinoma using a small pre-pilot-scale sample size. Ex vivo analysis was performed using resected pairs of colorectal adenocarcinoma and normal mucosa. Adenocarcinoma was confirmed by histologic evaluation of hematoxylin and eosin (H&E) permanent sections. Specimens were imaged using a custom hyperspectral imaging fluorescence excitation-scanning microscope system. Results demonstrated consistent spectral differences between normal and cancerous tissues over the fluorescence excitation range of 390 to 450 nm that could be the basis for wavelength-dependent detection of colorectal cancers. Hence, excitation-scanning hyperspectral imaging may offer an alternative approach for discriminating adenocarcinoma from surrounding normal colonic mucosa, but further studies will be required to evaluate the accuracy of this approach using a larger patient cohort.

Computational model of bladder tissue based on its measured optical properties

Urinary bladder diseases are a common problem throughout the world and often difficult to accurately diagnose. Furthermore, they pose a heavy financial burden on health services. Urinary bladder tissue from male pigs was spectrophotometrically measured and the resulting data used to calculate the absorption, transmission, and reflectance parameters, along with the derived coefficients of scattering and absorption. These were employed to create a "generic" computational bladder model based on optical properties, simulating the propagation of photons through the tissue at different wavelengths. Using the Monte-Carlo method and fluorescence spectra of UV and blue excited wavelength, diagnostically important biomarkers were modeled. Additionally, the multifunctional noninvasive diagnostics system "LAKK-M" was used to gather fluorescence data to further provide essential comparisons. The ultimate goal of the study was to successfully simulate the effects of varying excited radiation wavelengths on bladder tissue to determine the effectiveness of photonics diagnostic devices. With increased accuracy, this model could be used to reliably aid in differentiating healthy and pathological tissues within the bladder and potentially other hollow organs.

Hyperspectral Imaging Fluorescence Excitation Scanning for Detecting Colorectal Cancer: Pilot Study

Optical spectroscopy and hyperspectral imaging have shown the theoretical potential to discriminate between cancerous and non-cancerous tissue with high sensitivity and specificity. To date, these techniques have not been able to be effectively translated to endoscope platforms. Hyperspectral imaging of the fluorescence excitation spectrum represents a new technology that may be well-suited for endoscopic implementation. However, the feasibility of detecting differences between normal and cancerous mucosa using fluorescence excitation-scanning hyperspectral imaging has not been evaluated. The objective of this pilot study was to evaluate the changes in the fluorescence excitation spectrum of resected specimen pairs of colorectal adenocarcinoma and normal colorectal mucosa. Patients being treated for colorectal adenocarcinoma were enrolled. Representative adenocarcinoma and normal colonic mucosa specimens were collected from each case. Specimens were flash frozen in liquid nitrogen. Adenocarcinoma was confirmed by histologic evaluation of H&E permanent sections. Hyperspectral image data of the fluorescence excitation of adenocarcinoma and surrounding normal tissue were acquired using a custom microscope configuration previously developed in our lab. Results demonstrated consistent spectral differences between normal and cancerous tissues over the fluorescence excitation spectral range of 390-450 nm. We conclude that fluorescence excitation-scanning hyperspectral imaging may offer an alternative approach for differentiating adenocarcinoma and surrounding normal mucosa of the colon. Future work will focus on expanding the number of specimen pairs analyzed and will utilize fresh tissues where possible, as flash freezing and reconstituting tissues may have altered the autofluorescence properties.

In Vivo Detection of Rat Colorectal Cancers by using a Dual-Wavelength Excitation Method

Hypoxia is a characteristic feature of solid neoplasms, and insufficient oxygen supply increases cellular nicotinamide adenine dinucleotide (NADH) fluorescence, which is a main component of autofluorescence of the colorectal mucosa. We investigated whether a dual-wavelength excitation method which is optimized for sensing mucosal NADH fluorescence could be applicable to the detection of rat colorectal cancers in vivo. Rat colorectal adenocarcinomas were studied by using fluorescence stereomicroscopy. After autofluorescence images at 470 nm irradiated with dual-wavelength excitation at 365 nm (F365 ex) and 405 nm (F405 ex) were acquired, ratio images were produced by dividing F365 ex by F405 ex: The excitation-emission wavelength pairs in F365 ex and F405 ex were adjusted for acquisition of NADH fluorescence and reference fluorescence. Based on observations from the luminal surface in vivo, F365 ex/F405 ex ratio images indicated a 1.57-fold higher signal value in the cancers than in the surrounding normal mucosa. The signal values in F365 ex/F405 ex ratio images were less mutually related with the hemoglobin concentration index. Small adenocarcinomas (less than 4 mm) could be detected on F365 ex/F405 ex ratio images. The results showed that NADH fluorescence measurement with little interference from tissue hemoglobin is efficient for visualizing rat colorectal cancers in vivo, suggesting that the dual-wavelength excitation method has potential for label-free endoscopic detection of diminutive colorectal neoplasms.

Detection of lymph node metastases in human colorectal cancer by using 5-aminolevulinic acid-induced protoporphyrin IX fluorescence with spectral unmixing

Accurate evaluation of metastatic lymph nodes (LNs) is indispensable for adequate treatment of colorectal cancer (CRC) patients. Here, we demonstrate detection of metastases of human CRC in removed fresh LNs using 5-aminolevulinic acid (ALA)-induced protoporphyrin IX (PpIX) fluorescence. A spectral unmixing method was employed to reduce the overlap of collagen autofluorescence on PpIX fluorescence. A total of 17 surgery patients with advanced CRC were included in this study. After 5-ALA at a dose of 15 mg/kg of body weight was applied orally 2 h prior to surgery, 87 LNs were subjected to spectral fluorescence imaging and histopathological diagnosis, and statistical analysis was performed. No apparent side effect was observed to be associated with 5-ALA administration. The spectral unmixing fluorescence intensity of PpIX in metastatic LNs was 10.2-fold greater than that in nonmetastaic LNs. The receiver-operating-characteristic (ROC) analysis showed that the area under the curve (AUC) was calculated as 0.95. Our results show the potential of 5-ALA-induced PpIX fluorescence processed by spectral unmixing for detecting metastases in excised fresh LNs from patients with CRC, suggesting that this rapid and feasible method is applicable to gross evaluation of resected LN samples in pathology laboratories.

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

AIM: 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.

METHODS: 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.

RESULTS: 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.

CONCLUSION: 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.

Computer-aided diagnosis of neoplastic colorectal lesions using 'real-time' numerical color analysis during autofluorescence endoscopy

OBJECTIVE

Differentiating non-neoplastic colorectal lesions from neoplastic lesions during screening colonoscopies is essential to reduce the unnecessary treatment of non-neoplastic lesions. The present study was conducted to verify the diagnostic yields of the computer-aided diagnostic system that enables 'real-time' color analysis of colorectal lesions when applied to autofluorescence endoscopy (AFE).

PATIENTS AND METHODS

Consecutive patients who were scheduled to undergo a therapeutic colonoscopy in our department were enrolled in this study. The encountered lesions were evaluated in AFE and color-tone sampling was performed. Lesions with green/red (G/R) ratios less than 1.01 were judged to be neoplastic and those with G/R ratios of at least 1.01 were considered to be non-neoplastic. All lesions greater than 5 mm were endoscopically removed and lesions less than 5 mm were biopsied.

RESULTS

During the study period, a total of 32 patients with 102 colorectal lesions were evaluated with AFE. The mean G/R ratio for all neoplastic lesions was 0.86 [95% confidence interval (CI), 0.63-1.01], which was significantly lower than the mean G/R ratio for non-neoplastic lesions (1.12; 95% CI, 0.98-1.26; P<0.001). The mean G/R ratios were 1.36 (95% CI, 1.21-1.57) in normal mucosa, 1.12 (95% CI, 0.98-1.26) in hyperplastic lesions, 0.88 (95% CI, 0.69-1.02) in adenomas, and 0.61 (95% CI, 0.54-0.73) in intramucosal cancers. A G/R ratio cutoff value of 1.01 was applied for discriminating between neoplastic lesions and non-neoplastic lesions, and yielded sensitivity, specificity, positive and negative predictive values of 94.2, 88.9, 95.6, and 85.2%, respectively.

CONCLUSION

This diagnostic tool may lead to the reduction of unnecessary treatments for non-neoplastic lesions.

Assessing breast cancer margins ex vivo using aqueous quantum-dot-molecular probes

Positive margins have been a critical issue that hinders the success of breast- conserving surgery. The incidence of positive margins is estimated to range from 20% to as high as 60%. Currently, there is no effective intraoperative method for margin assessment. It would be desirable if there is a rapid and reliable breast cancer margin assessment tool in the operating room so that further surgery can be continued if necessary to reduce re-excision rate. In this study, we seek to develop a sensitive and specific molecular probe to help surgeons assess if the surgical margin is clean. The molecular probe consists of the unique aqueous quantum dots developed in our laboratory conjugated with antibodies specific to breast cancer markers such as Tn-antigen. Excised tumors from tumor-bearing nude mice were used to demonstrate the method. AQD-Tn mAb probe proved to be sensitive and specific to identify cancer area quantitatively without being affected by the heterogeneity of the tissue. The integrity of the surgical specimen was not affected by the AQD treatment. Furthermore, AQD-Tn mAb method could determine margin status within 30 minutes of tumor excision, indicating its potential as an accurate intraoperative margin assessment method.

Dual-wavelength excitation of mucosal autofluorescence for precise detection of diminutive colonic adenomas

BACKGROUND

The mucosal layer of the colon contains metabolism-related fluorophores, such as reduced nicotinamide adenine dinucleotide (NADH), which might have the potential to serve as biomarkers for detecting neoplasia.

OBJECTIVE

To examine NADH fluorescence in human colonic adenoma while eliminating the effect of hemoglobin absorption and to develop a novel imaging technique for precise detection of adenomas.

DESIGN

Cross-sectional study.

PATIENTS AND INTERVENTIONS

A total of 66 endoscopically resected colonic polyps were investigated. After serial acquisition of autofluorescence images between 450 and 490 nm illuminated with dual-wavelength excitation at 365 nm (F(365ex)) and 405 nm (F(405ex)) on cross sections of the samples, ratio images were created by dividing F(365ex) by F(405ex). The excitation-emission wavelength combinations in F(365ex) and F(405ex) were optimized for NADH fluorescence and reference fluorescence.

MAIN OUTCOME MEASUREMENTS

The F(365ex)/F(405ex) ratio in the tumorous (T) and normal (N) mucosa.

RESULTS

F(365ex)/F(405ex) ratio images showed a 1.81- and 1.12-fold higher signal intensity in the adenomas and hyperplastic polyps, respectively, than in the adjacent normal mucosa. The ratio between signal intensities in tumorous mucosa and normal mucosa in F(365ex)/F(405ex) ratio images for tubular adenomas was significantly higher than that for hyperplastic polyps. The signal intensity in F(365ex)/F(405ex) ratio images was not correlated with the hemoglobin concentration index evaluated by reflection images at 550 nm and 610 nm. Diminutive adenomas (<5 mm) and large adenomas were well discriminated in F(365ex)/F(405ex) ratio images.

LIMITATIONS

Ex vivo experiment.

CONCLUSIONS

These results suggest that the precise measurement of NADH fluorescence intensity together with eliminating the influence of blood hemoglobin concentration serves as a method for visualizing colonic adenomas and that the dual-wavelength excitation method is a promising technique applicable to endoscopic detection of early colonic adenomas.

Application of autofluorescence endoscopy for colorectal cancer screening: rationale and an update

As the result of basic researches, several intravital fluorophores have been determined so far in human colorectal tissue. Autofluorescence endoscopy (AFE) can detect slight alterations in their distribution and concentration during the colorectal carcinogenesis process and, thus facilitate noninvasive screening colonoscopies without the need for fluorescent substances or staining reagents to be administered. While detecting faint autofluorescence intensity by conventional fiberoptic endoscopy remains challenging, the latest AFE system with high-resolution videoendoscope capabilities enables such detection by using a false-color display algorithm. To this end, the diagnostic benefits of AFE have been reported in several multicenter randomized controlled studies of colorectal cancer (CRC) screening and differential diagnosis. CRC screening using the latest AFE technology could, therefore, lead to future reductions in CRC mortality.

Magnifying endoscopy with narrow-band imaging achieves superior accuracy in the differential diagnosis of superficial gastric lesions identified with white-light endoscopy: a prospective study

BACKGROUND

Conventional, white-light imaging endoscopy (WLE) results in a significant number of misdiagnoses in early gastric cancer. Magnifying endoscopy combined with narrow-band imaging (ME-NBI) is more accurate in the diagnosis of gastric cancer when the diagnostic triad of the disappearance of fine mucosal structure, microvascular dilation, and heterogeneity is used.

OBJECTIVE

The aim of the present study was to evaluate the superiority of ME-NBI in the differential diagnosis of superficial gastric lesions identified with conventional WLE.

DESIGN

Prospective, comparative study.

SETTING

Single academic center.

PATIENTS

This study involved patients who underwent WLE and ME-NBI for surveying synchronous or metachronous cancers because they had a high risk of gastric cancer.

INTERVENTION

Patients with superficial gastric lesions that were diagnosed by WLE as cancer or non-cancer with a slight suspicion of cancer were prospectively enrolled in the study. ME-NBI was used to further characterize lesions picked up with WLE.

MAIN OUTCOME MEASUREMENTS

Sensitivity and specificity for the diagnosis of gastric cancer, with pathology as the criterion standard.

RESULTS

A total of 201 lesions (mean diameter [+/- SD] 7.0 +/- 4.0 mm) from 111 patients (98 men, 13 women; mean age 66.3 years) were evaluated. Fourteen of the 201 lesions were pathologically proven as gastric cancer; the others were noncancerous lesions. The sensitivity and specificity for ME-NBI diagnosis with the use of the triad (92.9% and 94.7%, respectively) were significantly better than for WLE (42.9% and 61.0%, respectively; P < .0001).

LIMITATIONS

Single center and a highly selected population at high risk for gastric cancer.

CONCLUSION

ME-NBI achieved superior accuracy in the differential diagnosis of superficial gastric lesions identified with WLE. Thus, ME-NBI may increase the diagnostic value of endoscopy in a population at high risk of gastric cancer.

Analysis of the color patterns of early gastric cancer using an autofluorescence imaging video endoscopy system

BACKGROUND

Using a novel autofluorescence imaging video endoscopy system (AFI), tumors in the esophagus and the colon appeared purple in a green background, but the color patterns of early gastric cancer (EGC) were found to vary. Factors associated with these patterns remain unknown. The aims of the present study were to classify the color patterns of EGCs and to investigate the correlation between the patterns and clinicopathological features.

METHODS

A total of 107 EGCs that had been evaluated by AFI endoscopy, prior to endoscopic or surgical resection, were included. The color patterns of EGCs in AFI images and the association between tumor color and clinicopathological factors were evaluated. These factors included tumor morphology, location, size, background color, histological type, depth of invasion, lymphatic or vessel permeation, and ulceration.

RESULTS

The color patterns of EGCs were classified into the following four groups: purple tumors in a green background (52%); green tumors with a purple margin in a green background (21%); green tumors in a purple background (17%); and purple tumors in a purple background (10%). Univariate analysis showed that macroscopic type, histological type, ulceration, and background AFI color were significantly associated with tumor color, whereas multivariate analysis revealed that macroscopic type was the only independent contributor to tumor color.

CONCLUSION

The present study has enabled a clearer understanding of the significance of tumor color in relation to the AFI imaging of EGCs. Recognition of the color patterns in AFI images should help in the diagnosis of EGCs.

Trimodal imaging endoscopy may improve diagnostic accuracy of early gastric neoplasia: a feasibility study

BACKGROUND

A considerable number of superficial gastric neoplasias are overlooked with conventional white light imaging (WLI) endoscopy.

OBJECTIVE

The aim was to investigate the diagnostic potential of trimodal imaging endoscopy (TME), which combines WLI, autofluorescence imaging (AFI), and narrow-band imaging (NBI), for superficial gastric neoplasia.

DESIGN

Feasibility study.

SETTING

Single academic center.

PATIENTS

Sixty-two patients with or without gastric neoplasia.

INTERVENTION

Each patient serially assessed with WLI, AFI, and magnifying endoscopy with NBI (ME-NBI) by an endoscopist blinded for clinical information. ME-NBI over WLI and AFI was designated as TME. Histopathology of biopsy and ESD specimens was evaluated and used as the gold standard.

MAIN OUTCOME MEASUREMENTS

Sensitivity and specificity of endoscopic diagnosis of pathology-proven neoplasia by per-patient and per-lesion analyses.

RESULTS

The study included 47 pathology-proven neoplasias and 44 pathology-proven nonneoplasias that were detected as neoplasias with any of the modalities. By a per-lesion analysis, the sensitivity of TME (89.4%) was higher than that of WLI (76.6%) and AFI (68.1%). The specificity of TME (98.0%) was higher than that of WLI (84.3%) and AFI (23.5%). By a per-patient analysis, the sensitivity of TME (90.9%) was higher than that of WLI (75%) and AFI (68.2%). The specificity of TME (100%) was higher than that of WLI (72.2%) and AFI (44.4%).

LIMITATIONS

Case-enriched population at a single center.

CONCLUSIONS

Higher diagnostic accuracy of TME over conventional WLI indicates the feasibility of TME for the efficacious diagnosis of early gastric neoplasia.

Extending immunofluorescence detection limits in whole paraffin-embedded formalin fixed tissues using hyperspectral confocal fluorescence imaging

A major problem in microscopic imaging of ex vivo tissue sections stained with fluorescent agents (e.g. antibodies, peptides) is the confounding presence of background tissue autofluorescence. Autofluorescence limits (1) the accuracy of differentiating background signals from single and multiple fluorescence labels and (2) reliable quantification of fluorescent signals. Advanced techniques such as hyperspectral imaging and spectral unmixing can be applied to essentially remove this autofluorescent signal contribution, and this work attempts to quantify the effectiveness of autofluorescence spectral unmixing in a tumour xenograft model. Whole-specimen single-channel fluorescence images were acquired using excitation wavelengths of 488 nm (producing high autofluorescence) and 568 nm (producing negligible autofluorescence). These single-channel data sets are quantified against hyperspectral images acquired at 488 nm using a prototype whole-slide hyperspectral fluorescence scanner developed in our facility. The development and further refinement of this instrument will improve the quantification of weak fluorescent signals in fluorescence microscopy studies of ex vivo tissues in both preclinical and clinical applications.

Numerical analysis of the autofluorescence intensity of neoplastic and non-neoplastic colorectal lesions by using a novel videoendoscopy system

BACKGROUND

Autofluorescence endoscopy (AFE) may improve detection and diagnosis of colorectal lesions. Recently, AFE based on a high-resolution video endoscope was developed.

OBJECTIVE

A novel high-resolution video AFE system was used to quantify autofluorescence of colorectal lesions to determine the characteristics of non-neoplastic and neoplastic lesions.

DESIGN

Retrospective observational study.

SETTING

Single-center referral hospital.

PATIENTS

Ninety-seven patients with 103 colorectal lesions (22 non-neoplastic and 81 neoplastic lesions) who underwent AFE and were treated by using endoscopy or by surgery.

INTERVENTION

Recorded digital AFE images were analyzed to quantify autofluorescence. The following autofluorescence indexes were calculated: the green/red (G/R) ratio for each lesion, the color-contrast index between each lesion, and the corresponding normal region.

MAIN OUTCOME MEASUREMENTS

The G:R ratio, color-contrast index, and histopathologic characteristics for each colorectal lesion.

RESULTS

The mean G/R ratio was significantly higher in non-neoplastic lesions (1.17 [95% CI, 1.10-1.24], n = 22) than in neoplastic lesions (0.65 [95% CI, 0.63-0.68], n = 81) (P < .001). Mean color-contrast indexes were significantly lower in non-neoplastic lesions (7.99 [95% CI, 6.40-9.58], n = 22) than neoplastic lesions (35.06 [95% CI, 32.79-37.33], n = 81; P < .001). With a cutoff value of 1.01 for the G/R ratio and 13.94 for color-contrast index, AFE had a sensitivity and specificity of 98.8% and 86.4% respectively, for G/R ratio, and 98.8% and 90.9%, respectively, for color contrast index, in differentiating neoplastic from non-neoplastic colorectal lesions.

LIMITATIONS

Retrospective design.

CONCLUSIONS

The quantification of digital AFE images obtained from the novel high-resolution videoendoscopy system revealed that autofluorescence was significantly different between non-neoplastic and neoplastic lesions, and color tone in AFE may represent the histopathologic characteristics of the lesion.

Comparison of autofluorescence imaging endoscopic findings with pathologic findings after endoscopic submucosal dissection of gastric neoplasms

BACKGROUND/AIMS

All epithelial cells emit autofluoresce, with tumor cells emitting weaker autofluorescence. We categorized patterns of autofluorescence imaging (AFI) and compared their clinical characteristics and pathology findings after endoscopic submucosal dissection.

METHODS

Twenty patients were enrolled, comprising 4 adenomas and 16 early gastric cancers. AFI findings were classified as follows: G0 (well-defined pink lesion on a green background with a clear interface over >/=50% of its area), G1 (pink-green mottled lesion on a green background with a clear interface over <50% of its area), P1 (pink-green mottled lesion on a purple background with a clear interface over <50% of its area), and P2 (vague lesion on a purple background with a clear interface over </=10% of its area).

RESULTS

Most of the patients (80%) were male, and their median age was 62.4 years (range: 46-78 years). The lesion sizes by white-light mode, AFI mode, and pathology were 20.8+/-13.1, 22.8+/-15.4, and 20.0+/-17.7 mm (mean+/-SD), respectively. Sixteen cases of adenocarcinoma were classified as follows: G0 (n=10), G1 (n=2), P1 (n=2), and P2 (n=2). The G0 group has no p53 positive lesions, unlike the non-G0 group (p=0.044). All cases with the P1 and P2 patterns were of the gastric and intestinal types, respectively.

CONCLUSIONS

AFI images of gastric tumors were categorized into four patterns that were useful for defining the resection margin in 87.5% of cases, with G0 being the most common pattern (62.5%).

Evaluation of autofluorescence colonoscopy for the detection and diagnosis of colonic polyps

BACKGROUND

Colorectal cancer is the second most common cause of death in the United Kingdom. Most cancers are believed to arise within preexisting adenomas. Although colorectal adenomas have a clear neoplastic potential, hyperplastic polyps do not. It, therefore, would be helpful to be able to differentiate between different polyps at a colonoscopy. Autofluorescence (AF) endoscopy has been developed to enhance conventional white light (WL) endoscopy in the diagnosis of GI lesions.

OBJECTIVE

The aim of the present study was to evaluate whether AF colonoscopy can facilitate endoscopic detection and differentiation of colorectal polyps.

DESIGN

Patients were invited to attend for colonic assessment with both AF and WL endoscopy. AF readings, pictures, and biopsy specimens were taken of any visible pathology and of any high AF areas.

SETTING

Gartnavel General Hospital, Glasgow, U.K.

PATIENTS

A total of 107 patients were assessed.

INTERVENTION

Each patient was assessed with AF and WL colonoscopy.

MAIN OUTCOME MEASUREMENTS

An AF intensity ratio (AIR) was calculated for each polyp (ratio of direct polyp AF reading/background rectal AF activity).

RESULTS

A total of 75 polyps were detected: 54 adenomatous and 21 hyperplastic polyps. Colorectal adenomas had a significantly higher AIR compared with hyperplastic polyps (median, interquartile range): adenoma (3.54, 2.54-5.00] versus hyperplastic (1.60, 1.30-2.24); P = .0001). When using an AIR with the empirically cutoff value of 2.3, AF endoscopy had a sensitivity of 85% and a specificity of 81% at distinguishing adenomatous polyps from hyperplastic polyps.

CONCLUSIONS

AF colonoscopy may be a valuable tool for the visual distinction between adenomatous and hyperplastic polyps.

Does autofluorescence imaging videoendoscopy system improve the colonoscopic polyp detection rate?--a pilot study

OBJECTIVES

Colonoscopy is considered the gold standard for the detection of colorectal polyps; however, polyps can be missed with conventional white light (WL) colonoscopy. The aim of this pilot study was to evaluate whether a newly developed autofluorescence imaging (AFI) system can detect more colorectal polyps than WL.

METHODS

A modified back-to-back colonoscopy using AFI and WL was conducted for 167 patients in the right-sided colon including cecum, ascending and transverse colon by a single experienced colonoscopist. The patient was randomized to undergo the first colonoscopy with either AFI or WL (group A: AFI-WL, group B: WL-AFI). The time needed for both insertion and examination for withdrawal and all lesions detected in the right-sided colon were recorded.

RESULTS

Eighty-three patients were randomized to group A and 84 to group B. The total number of polyps detected by AFI and WL colonoscopy was 100 and 73, respectively. The miss rate for all polyps with AFI (30%) was significantly less than that with WL (49%) (P= 0.01).

CONCLUSIONS

AFI detects more polyps in the right-sided colon compared to WL colonoscopy.

ENDOSCOPIC MOLECULAR IMAGING: BEACON TO THE DESTINATION

Imaging technologies in gastrointestinal endoscopy have advanced greatly over the past few decades. Molecular imaging may be an additional innovation to conventional imaging methods and allow visualization of the localization, function, and characteristics of targets, especially in cancers. To realize endoscopic molecular imaging, there are three prerequisites: first, more target‐specific and highly sensitive biomarkers for clinical use; second, fluorochromes that have a high affinity to the markers and can produce a distinct signal; and third, equipment to visualize the indicator at high resolution in real time. This technique can be used for cancer screening and surveillance and can also provide important information for deciding treatment strategies and evaluating their effectiveness during therapy. Endoscopic molecular imaging will play a central role in gastrointestinal oncology in the near future.

Characteristics of laser-induced autofluorescence spectra in early colorectal carcinoma

AIM: To analyze the characteristics of laser-induced autofluorescence spectra in early colorectal carcinoma.

METHODS: An animal model of colorectal carcinoma was established by injecting DMH in abdominal cavity of Sprague-Dawley rats. Samples were collected from normal, early-stage and advanced carcinoma tissues, respectively. The characteristics of their laser-induced autofluorescence spectra were analyzed.

RESULTS: A total of 226 samples were collected, including 64 normal colorectal tissue samples, 78 early-stage and 84 advanced colorectal carcinoma tissue samples. Spectra peaks were observed at about 460 nm and 505 nm in different groups. The wavelength at 460 nm in normal tissue samples differed significantly from those in early stage and advanced colorectal cancer tissue samples (457.66 ± 3.28, 467.87 ± 7.71, 468.60 ± 4.53, P < 0.05). Spectra peaks were found at 635 nm in 73% advanced colorectal carcinoma tissue samples and 69% early-stage colorectal carcinoma tissue samples, but not in normal colorectal tissue samples. The mean wavelength at 460 nm was longer in normal colorectal tissue samples than in early stage and advanced colorectal carcinoma tissue samples (457.66 ± 3.28 vs 467.87 ± 7.71, 468.60 ± 4.53, P < 0.05). The values of I635/I460 and I635/I600 in early-stage (1.9507 ± 1.1460, 0.4215 ± 0.2582) and advanced carcinoma tissue samples (2.1368 ± 1.4721, 0.4482 ± 0.2309) were higher than those in normal colorectal tissue samples (0.7494 ± 0.1077, 0.1416 ± 0.0439, P < 0.05).

CONCLUSION: The characteristics of laser-induced autofluorescence spectra are different in normal colorectal tissue, early-stage and advanced colorectal carcinoma tissue, and can be used to diagnose early-stage colorectal carcinoma.

In vivo biomarkers for targeting colorectal neoplasms

Colorectal carcinoma continues to be a leading cause of cancer morbidity and mortality despite widespread adoption of screening methods. Targeted detection and therapy using recent advances in our knowledge of in vivo cancer biomarkers promise to significantly improve methods for early detection, risk stratification, and therapeutic intervention. The behavior of molecular targets in transformed tissues is being comprehensively assessed using new techniques of gene expression profiling and high throughput analyses. The identification of promising targets is stimulating the development of novel molecular probes, including significant progress in the field of activatable and peptide probes. These probes are being evaluated in small animal models of colorectal neoplasia and recently in the clinic. Furthermore, innovations in optical imaging instrumentation are resulting in the scaling down of size for endoscope compatibility. Advances in target identification, probe development, and novel instruments are progressing rapidly, and the integration of these technologies has a promising future in molecular medicine.

Characterization of tissue autofluorescence in Barrett's esophagus by confocal fluorescence microscopy

High grade dysplasia and early cancer in Barrett's esophagus can be distinguished in vivo by endoscopic autofluorescence point spectroscopy and imaging from non-dysplastic Barrett's mucosa. We used confocal fluorescence microscopy for ex vivo comparison of autofluorescence in non-dysplastic and dysplastic Barrett's esophagus. Unstained frozen sections were obtained from snap-frozen Barrett's esophagus biopsy samples and scanned with confocal fluorescence microscopy (458 nm excitation; 505-550 nm [green] and > 560 nm [red] emission). Digital micrographs were taken from areas with homogenous and specific histopathology. Visual inspection and statistical analysis were used to evaluate the image datasets. Dysplastic and non-dysplastic Barrett's esophagus epithelia fluoresced mainly in the green spectrum and the main sources of autofluorescence were the cytoplasm and lamina propria. High-grade dysplasia was differentiated from non-dysplastic Barrett's esophagus by microstructural tissue changes. However, there were no specific changes in either the locations or average intensities of intrinsic green and red autofluorescence at the epithelial level that could differentiate between dysplastic and non-dysplastic Barrett's esophagus epithelia, ex vivo. Detectable differences in autofluorescence between BE and dysplasia/cancer in vivo are probably not caused by specific changes in epithelial fluorophores but are likely due to other inherent changes (e.g. mucosal thickening and increased microvascularity) attenuating autofluorescence from the collagen-rich submucosa. Furthermore, confocal fluorescence microscopy provides 'histology-like' imaging of Barrett's tissues and may offer a unique opportunity to exploit microstructural tissue changes occurring during neoplastic transformation for in vivo detection of high-grade dysplasia in Barrett's patients using newly developed confocal fluorescence microendoscopy devices.

Autofluorescence properties of rat cerebellum cortex during postnatal development

BACKGROUND AND OBJECTIVES

The multilayered structure of rat neocerebellum cortex (VI-VIII lobules of the vermis) during postnatal development undergoes rearrangements, which in turn are affected by treatment with the anti-tumoral drug cisplatin. The dependence of autofluorescence emission properties on the tissue structural and molecular features has been investigated.

STUDY DESIGN/MATERIALS AND METHODS

Autofluorescence analysis was performed at defined time points of cerebellar histogenesis--11, 17, and 30 postnatal days- under normal conditions or after 5 microg/g body weight cisplatin treatment at 10 postnatal day. Autofluorescence signal was analyzed in vivo at the surface of intact lobules of cerebellum vermis by means of fiber optic spectrofluorometry, or on tissue sections by means of microspectrofluorometry and fluorescence imaging.

RESULTS

In vivo spectroscopy showed changes of autofluorescence signal both during normal histogenesis and after cisplatin treatment. External granular layer (EGL) and molecular layer (ML), that is, the more external layers were found to be interested by structural alterations, and showed the greatest changes in signal amplitude, accounting for the in vivo results. Fitting analysis indicated that changes in spectral shape reflected an increase in oxidative damages induced by cisplatin treatment.

CONCLUSIONS

The results confirm the relationship of the autofluorescence emission properties with histological and biochemical features of biological tissue.

Multispectral imaging autofluorescence microscopy in colonic and gastric cancer metastatic lymph nodes

BACKGROUND & AIMS

The lymphadenectomy and extended lymphadenectomy procedures have been points of controversy in surgical oncology. The methods available for the detection of metastatic lymph nodes are numerous. These include lymphoscintigraphy and radiolabeled antibody detection, but in most cancers the currently used technique is sentinel lymph node identification, performed primarily through the use of immunohistochemistry. We propose the application of autofluorescence (AF)-based techniques for lymph node evaluation in colorectal and gastric tumors.

METHODS

We studied 30 clinical cases: 15 colorectal cancers and 15 gastric cancers. All of the patients were in the advanced stages of the disease and were candidates for adjuvant therapy. Autofluorescence microspectroscopy and multispectral imaging autofluorescence microscopy have been used to analyze the AF emission of metastatic lymph node sections, excited with 365-nm wavelength radiation. The AF spectra were recorded in the range of 400-700 nm. Monochrome AF images were acquired sequentially through interference filters peaked at 450, 550, and 650 nm, and then combined together in a single red-green-blue image. The AF pattern and the emission spectrum of metastatic lymph nodes have unique characteristics that can be used to distinguish them from the normal ones.

RESULTS

The results, compared with standard histopathologic procedures and with specific staining methods, supplied a satisfactory validation of the proposed technique, revealing the possibility of improving the actual diagnostic procedures for malignant lymph node alterations.

CONCLUSIONS

With the development of appropriate instrumentation, the proposed technique could be particularly suitable in intrasurgical diagnosis of metastatic lymph nodes.

Correlation coefficient mapping in fluorescence spectroscopy: tissue classification for cancer detection

Correlation coefficient mapping has been applied to intrinsic fluorescence spectra of colonic tissue for the purpose of cancer diagnosis. Fluorescence emission spectra were collected of 57 colonic tissue sites in a range of 4 physiological conditions: normal (29), hyperplastic (2), adenomatous (5), and cancerous tissues (21). The sample-sample correlation was used to examine the ability of correlation coefficient mapping to determine tissue disease state. The correlation coefficient map indicates two main categories of samples. These categories were found to relate to disease states of the tissue. Sensitivity, selectivity, predictive value positive, and predictive value negative for differentiation between normal tissue and all other categories were all above 92%. This was found to be similar to, or higher than, tissue classification using existing methods of data reduction. Wavelength-wavelength correlation among the samples highlights areas of importance for tissue classification. The two-dimensional correlation map reveals absorption by NADH and hemoglobin in the samples as negative correlation, an effect not obvious from the one-dimensional fluorescence spectra alone. The integrity of tissue was examined in a time series of spectra of a single tissue sample taken after tissue resection. The wavelength-wavelength correlation coefficient map shows the areas of significance for each fluorophore and their relation to each other. NADH displays negative correlation to collagen and FAD, from the absorption of emission or fluorescence resonance energy transfer. The wavelength-wavelength correlation map for the decay set also clearly shows that there are only three fluorophores of importance in the samples, by the well-defined pattern of the map. The sample-sample correlation coefficient map reveals the changes over time and their impact on tissue classification. Correlation coefficient mapping proves to be an effective method for sample classification and cancer detection.

The status of in vivo autofluorescence spectroscopy and imaging for oral oncology

Autofluorescence spectroscopy and imaging have been studied for the early detection and classification of (pre)malignancies of the oral mucosa. In the present review we will give an overview of the literature on autofluorescence imaging and spectroscopy for various clinical questions. From the studies performed so far we hope to conclude whether autofluorescence spectroscopy and imaging are helpful in the diagnosis of lesions of the oral mucosa, and if this is the case: for which clinical questions they are suitable. A strong emphasis is put on in vivo human studies of the oral mucosa.

Cell and tissue autofluorescence research and diagnostic applications

Cells contain molecules, which become fluorescent when excited by UV/Vis radiation of suitable wavelength. This fluorescence emission, arising from endogenous fluorophores, is an intrinsic property of cells and is called auto-fluorescence to be distinguished from fluorescent signals obtained by adding exogenous markers. The majority of cell auto-fluorescence originates from mitochondria and lysosomes. Together with aromatic amino acids and lipo-pigments, the most important endogenous fluorophores are pyridinic (NADPH) and flavin coenzymes. In tissues, the extracellular matrix often contributes to the auto-fluorescence emission more than the cellular component, because collagen and elastin have, among the endogenous fluorophores, a relatively high quantum yield. Changes occurring in the cell and tissue state during physiological and/or pathological processes result in modifications of the amount and distribution of endogenous fluorophores and chemical-physical properties of their microenvironment. Therefore, analytical techniques based on auto-fluorescence monitoring can be utilized in order to obtain information about morphological and physiological state of cells and tissues. Moreover, auto-fluorescence analysis can be performed in real time because it does not require any treatment of fixing or staining of the specimens. In the past few years spectroscopic and imaging techniques have been developed for many different applications both in basic research and diagnostics.

Optical biopsy: a new frontier in endoscopic detection and diagnosis

Endoscopic diagnosis currently relies on the ability of the operator to visualize abnormal patterns in the image created by light reflected from the mucosal surface of the gastrointestinal tract. Advances in fiber optics, light sources, detectors, and molecular biology have led to the development of several novel methods for tissue evaluation in situ. The term "optical biopsy" refers to methods that use the properties of light to enable the operator to make an instant diagnosis at endoscopy, previously possible only by using histological or cytological analysis. Promising imaging techniques include fluorescence endoscopy, optical coherence tomography, confocal microendoscopy, and molecular imaging. Point detection schemes under development include light scattering and Raman spectroscopy. Such advanced diagnostic methods go beyond standard endoscopic techniques by offering improved image resolution, contrast, and tissue penetration and providing biochemical and molecular information about mucosal disease. This review describes the basic biophysics of light-tissue interactions, assesses the strengths and weaknesses of each method, and examines clinical and preclinical evidence for each approach.

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.

Investigation of normal and malignant laryngeal tissue by autofluorescence imaging technique

OBJECTIVE

During oncogenesis significant changes in tissue properties occur that result in alteration of fluorescence characteristics of the tissue. The differences in autofluorescence between normal and malignant tissues offer new possibilities in detecting epithelial pathological lesions.

AIM

The aim of our study was to determine the usefulness of autofluorescence technique in diagnostic of laryngeal tumors.

MATERIAL AND METHODS

Fluorescence in larynxes from 10 laryngectomized cancer patients was induced by excitation light at 360-450 nm wavelength. As a light source, mercury lamp and laser (404 nm) were used. The CCD camera captured the fluorescent light emitted. Normal epithelium and cancer tissue were also analyzed on fluorescence microscopy.

RESULTS

Laryngeal carcinoma tissues when excited with ultraviolet or blue light generate attenuated or absent autofluorescence in the green light band compare with normal epithelium where strong signal around 505 nm was detected. Average value of maximal autofluorescence intensities was 26.2V (range 18-35) and 4.4V (range 2-8) in healthy and cancerously changed mucosa respectively. Spectral analysis revealed that autofluorescence signal from unchanged mucosa (around 505 nm) was significantly higher compared to cancer tissue (P=0.005).

CONCLUSIONS

It seems that autofluorescence imaging may be a supplementary tool in diagnosis of laryngeal tumors.

A new infrared fluorescent-labeling agent and labeled antibody for diagnosing microcancers

PURPOSE

We have developed infrared fluorescent labeling agents and infrared-ray fluorescence endoscopes to establish a novel diagnostic technique. Since the fluorescence intensity of the initial labeled antibody (ICG-sulfo-OSu-labeled antibody) was not sufficient for practical use, we synthesized indocyanine green acylthiazolidinethione (ICG-ATT), which was expected to label various target molecules having amino groups efficiently.

MATERIALS AND METHODS

To confirm imaging of infrared fluorescence intensity of ICG-ATT- and ICG-sulfo-OSu-labeled anti-MUC1 antibodies, cotton thread was soaked in various concentrations of the antibody solution in 0.1M PBS, and observed under the epi-illumination infrared fluorescence microscope. Localization and the intensity of infrared fluorescence and DAB coloring was compared in paraffin sections of human gastric mucosa.

RESULTS

In the study of cotton threads, both labeled antibodies showed relatively clear infrared fluorescence, and significant difference was not observed between the two antibodies. ICG-ATT-labeled anti-MUC1 antibody produced stronger staining than that by ICG-sulfo-OSu-labeled antibody. Localization pattern of infrared fluorescent staining was in good agreement with that by the conventional method with oxidized DAB staining.

CONCLUSION

ICG-ATT is useful as a fluorescent-labeling agent for diagnosis of microcancers by infrared fluorescence endoscopes.

Effect of fiber optic probe geometry on depth-resolved fluorescence measurements from epithelial tissues: a Monte Carlo simulation

Developing fiber optic probe geometries to selectively measure fluorescence spectra from different sublayers within human epithelial tissues will potentially improve the endogenous fluorescence contrast between neoplastic and nonneoplastic tissues. In this study, two basic fiber optic probe geometries, which are called the variable aperture (VA) and multidistance (MD) approaches, are compared for depth-resolved fluorescence measurements from human cervical epithelial tissues. The VA probe has completely overlapping illumination and collection areas with variable diameters, while the MD probe employs separate illumination and collection fibers with a fixed separation between them. Monte Carlo simulation results show that the total fluorescence detected is significantly higher for the VA probe geometry, while the probing depth is significantly greater for the MD probe geometry. An important observation is that the VA probe is more sensitive to the epithelial layer, while the MD probe is more sensitive to the stromal layer. The effect of other factors, including numerical aperture (NA) and tissue optical properties on the fluorescence measurements with VA and MD probe geometries, are also evaluated. The total fluorescence detected with both probe geometries significantly increases when the fiber NA is changed from 0.22 to 0.37. The sensitivity to different sublayers is found to be strongly dependent on the tissue optical properties. The simulation results are used to design a simple fiber optic probe that combines both the VA and MD geometries to enable fluorescence measurements from the different sublayers within human epithelial tissues.

Preliminary study of detecting neoplastic growths in vivo with real time calibrated autofluorescence imaging

The goal of this study was to evaluate the capabilities of a calibrated autofluorescence imaging method for detecting neoplastic lesions. An imaging system that records autofluorescence images calibrated by the cross-polarized reflection images from excitation was instrumented for the evaluation. Cervical tissue was selected as the living tissue model. Sixteen human subjects were examined in vivo with the imaging system before routine examination procedures. It was found that calibrated autofluorescence signals from neoplastic lesions were generally lower than signals from normal cervical tissue. Neoplastic lesions can be differentiated from surrounding normal tissue based on the contrast in the calibrated autofluorescence. The effects of the optical properties of tissue on the calibrated fluorescence imaging were investigated.

Autofluorescence imaging to optimize 5-ALA-induced fluorescence endoscopy of bladder carcinoma

OBJECTIVES

To design an optical system for detecting autofluorescence (AF) of bladder tumors and to determine the success of reducing the false-positive rate of 5-aminolevulinic acid-induced fluorescence endoscopy (AFE). AFE provides significantly higher sensitivity in detecting and localizing bladder carcinoma compared with white light endoscopy. The specificity of AFE is equivalent to white light endoscopy, mostly because of the false-positive fluorescence of chronic cystitis lesions. Laser-induced spectral autofluorescence detection is also an efficient method in the diagnosis of bladder carcinoma.

METHODS

Bladder tissue was excited to AF using the D-Light (375 to 440 nm) after regular AFE with detection of fluorescence-positive areas. The optical image was produced using a special RGB camera. Biopsies were taken from AFE-positive areas, the peritumoral edges, and normal bladder mucosa. The AF images of the suspicious areas were compared with the AFE images and the histologic results.

RESULTS

A total of 43 biopsies were histologically examined (24 benign and 19 neoplastic). AF imaging showed contrast differences between papillary tumors, flat lesions, and normal mucosa. The combination of AFE with AF raised the specificity of AFE alone from 67% to 88%.

CONCLUSIONS

AF imaging is possible. The value of the method in reducing the false-positive rate of the highly sensitive AFE needs to be validated with higher numbers. The combination of AF with AFE had a 20% higher specificity than AFE alone in our study.

Autofluorescence endoscopy: feasibility of detection of GI neoplasms unapparent to white light endoscopy with an evolving technology

BACKGROUND

Case studies are presented of fluorescence endoscopy in the upper and lower GI tract to illustrate the ability to detect early-stage lesions that were not observable with white light endoscopy or those in which the assessment of the stage or extension of the lesion were equivocal.

METHODS

A new fluorescence imaging system was used in which blue light excites the naturally-occurring fluorescence of tissues (autofluorescence). The system produces real-time, false-color images that combine green and red fluorescence intensities. In general, abnormal lesions are seen to have an increase in the red-to-green fluorescence intensity compared with surrounding tissue. This system was evaluated in patients at 4 participating institutions, concurrently with standard white light endoscopy, with or without dye staining.

RESULTS

Selected cases are presented in which fluorescence imaging identified specific lesions including focal high-grade dysplasia in Barrett's mucosa, signet ring carcinoma of the stomach, and flat adenoma in the colon.

CONCLUSIONS

The capability of autofluorescence endoscopy to detect the presence and extent of occult malignant and premalignant GI lesions has been demonstrated. The future development and evaluation of this technology are discussed.

Detection of early gastric cancer by a real-time autofluorescence imaging system

A light-induced fluorescence endoscopy in the gastrointestinal tract system was used in 52 patients with 54 lesions (33 early gastric cancers, 21 benign lesions) to assess its ability to detect early gastric cancer. Comparing the images with the histological findings, 21 of the 33 carcinomas appeared dark red, ten had a mixed pattern of dark red and white, and two could not be detected. Of the 21 benign lesions, 18 appeared light blue, as do normal mucosa, with this system. In 85% of the cancer lesions (28/33), cancer extension was correctly detected. The sensitivity and specificity were 94 and 86%, respectively. Real-time autofluorescence endoscopy is a useful adjunct to conventional white-light endoscopy for detecting early gastric cancer.

Fluorescence spectroscopy of neoplastic and non-neoplastic tissues

Fast and non-invasive, diagnostic techniques based on fluorescence spectroscopy have the potential to link the biochemical and morphologic properties of tissues to individual patient care. One of the most widely explored applications of fluorescence spectroscopy is the detection of endoscopically invisible, early neoplastic growth in epithelial tissue sites. Currently, there are no effective diagnostic techniques for these early tissue transformations. If fluorescence spectroscopy can be applied successfully as a diagnostic technique in this clinical context, it may increase the potential for curative treatment, and thus, reduce complications and health care costs. Steady-state, fluorescence measurements from small tissue regions as well as relatively large tissue fields have been performed. To a much lesser extent, time-resolved, fluorescence measurements have also been explored for tissue characterization. Furthermore, sources of both intrinsic (endogenous fluorophores) and extrinsic fluorescence (exogenous fluorophores) have been considered. The goal of the current report is to provide a comprehensive review on steady-state and time-resolved, fluorescence measurements of neoplastic and non-neoplastic, biologic systems of varying degrees of complexity. First, the principles and methodology of fluorescence spectroscopy are discussed. Next, the endogenous fluorescence properties of cells, frozen tissue sections and excised and intact bulk tissues are presented; fluorescence measurements from both animal and human tissue models are discussed. This is concluded with future perspectives.