Natural fluorescence of normal and neoplastic human colon: a comprehensive "ex vivo" study

Autofluorescence spectroscopy in photodynamic therapy for skin rejuvenation: A theranostic approach in aesthetic medicine

BACKGROUND

The method of photodynamic therapy for skin rejuvenation (PDT-SR) provides an improvement in appearance with a safe and painless effect. The quality of treatment is most often assessed subjectively. The most informative morphological control methods are rarely used due to the invasiveness of the sampling procedure.

AIM

This study aimed to find out the possibility of using skin autofluorescence spectroscopy (SAF) for an objective assessment of changes occurring in the skin during PDT-SR.

METHODS

This study included 12 volunteers (10 women, 2 men) aged 32 to 79 years. Two (n = 6) or three (n = 6) PDT sessions were performed at intervals of 13-30 days. Photosensitizer chlorin e6, exposure 20 min, energy density 18-24 J/cm2 were used. SAF spectra were recorded using a two-wavelength fiber optic spectrometer under excitation at wavelengths (λex) of 365 nm and 440 nm. Measurements were made both before and after each PDT session and up to 25-238 days from the start of treatment. For the evaluation, we used the spectra AF365(λ) and AF440(λ) averaged over 40 points corrected for diffuse reflection at λex=440 nm in the range λem= 460-700 nm, as well as the spectra of the ratios AFN365(λ) and AFN440(λ), which were obtained by dividing the intensities of the current spectra by the intensities collected before PDT-SR.

RESULTS

PDT-SR led to changes in both the intensity and shape of the spectra. Analysis of the spectra using numerical fitting of the spectra showed that the main changes can be explained by changes in the content of advanced glycation end products (AGEs), as well as lipofuscin-like lipopigments (LPs) and porphyrins (PPs). The spectra of AGEs upon excitation at wavelengths of 365 and 440 nm differ, which may be due to the formation of two types of bonds, with collagen and elastin. By the end of the study, the vast majority of the examined volunteers showed a significant decrease of the parameters characterizing both of these types of AGEs, AGE365 (0.56-1.2) and AGE440 (0.58-1.01), relative to the beginning of the study. In most cases, a decrease was also noted for LPs and PPs. AGE365 and AGE440 were positively correlated with the age of the volunteers (r2 = 0.26-0.46 %). A steady decrease in the content of AGEs occurred approximately on the 40th day.

CONCLUSION

SAF spectroscopy makes it possible to assess changes in the content of AGEs, LPs, and PPs in the skin during PDT-SR. The method has great potential for non-invasive monitoring of the treatment process, as well as its improvement, including through its personalization. In addition, the method can be used to study the mechanisms of age-related skin changes at the molecular level and to study the processes of rejuvenation.

Choosing the Probe for Single-Molecule Fluorescence Microscopy

Probe choice in single-molecule microscopy requires deeper evaluations than those adopted for less sensitive fluorescence microscopy studies. Indeed, fluorophore characteristics can alter or hide subtle phenomena observable at the single-molecule level, wasting the potential of the sophisticated instrumentation and algorithms developed for advanced single-molecule applications. There are different reasons for this, linked, e.g., to fluorophore aspecific interactions, brightness, photostability, blinking, and emission and excitation spectra. In particular, these spectra and the excitation source are interdependent, and the latter affects the autofluorescence of sample substrate, medium, and/or biological specimen. Here, we review these and other critical points for fluorophore selection in single-molecule microscopy. We also describe the possible kinds of fluorophores and the microscopy techniques based on single-molecule fluorescence. We explain the importance and impact of the various issues in fluorophore choice, and discuss how this can become more effective and decisive for increasingly demanding experiments in single- and multiple-color applications.

Application of Two-Dimensional Fluorescence Spectroscopy for the On-Line Monitoring of Teff-Based Substrate Fermentation Inoculated with Certain Probiotic Bacteria

There is increasing demand for cereal-based probiotic fermented beverages as an alternative to dairy-based products due to their limitations. However, analyzing and monitoring the fermentation process is usually time consuming, costly, and labor intensive. This research therefore aims to apply two-dimensional (2D)-fluorescence spectroscopy coupled with partial least-squares regression (PLSR) and artificial neural networks (ANN) for the on-line quantitative analysis of cell growth and concentrations of lactic acid and glucose during the fermentation of a teff-based substrate. This substrate was inoculated with mixed strains of Lactiplantibacillus plantarum A6 (LPA6) and Lacticaseibacillus rhamnosus GG (LCGG). The fermentation was performed under two different conditions: condition 1 (7 g/100 mL substrate inoculated with 6 log cfu/mL) and condition 2 (4 g/100 mL substrate inoculated with 6 log cfu/mL). For the prediction of LPA6 and LCGG cell growth, the relative root mean square error of prediction (pRMSEP) was measured between 2.5 and 4.5%. The highest pRMSEP (4.5%) was observed for the prediction of LPA6 cell growth under condition 2 using ANN, but the lowest pRMSEP (2.5%) was observed for the prediction of LCGG cell growth under condition 1 with ANN. A slightly more accurate prediction was found with ANN under condition 1. However, under condition 2, a superior prediction was observed with PLSR as compared to ANN. Moreover, for the prediction of lactic acid concentration, the observed values of pRMSEP were 7.6 and 7.7% using PLSR and ANN, respectively. The highest error rates of 13 and 14% were observed for the prediction of glucose concentration using PLSR and ANN, respectively. Most of the predicted values had a coefficient of determination (R2) of more than 0.85. In conclusion, a 2D-fluorescence spectroscopy combined with PLSR and ANN can be used to accurately monitor LPA6 and LCGG cell counts and lactic acid concentration in the fermentation process of a teff-based substrate. The prediction of glucose concentration, however, showed a rather high error rate.

Autofluorescence imaging for recurrence detection in skin cancer postoperative scars

This clinical study is a first attempt to use autofluorescence for recurrence diagnosis of skin cancer in postoperative scars. The proposed diagnostic parameter is based on a reduction in scar autofluorescence, evaluated in the green spectral channel. The validity of the method has been tested on 110 postoperative scars from 56 patients suspected of non-melanoma skin cancer, with eight patients (13 scars) available for the repeated examination. The recurrence diagnosis within a scar has been made after two subsequent autofluorescence check-ups, representing the temporal difference between the scar autofluorescence amplitudes as a vector. The recognition of recurrence has been discussed to represent the significant deviations from the value of vector angle θ. This new autofluorescence-based method can be easily integrated into the postoperative monitoring of surgical scars and can help diagnose the recurrence of skin cancer from the early stage of scar development.

Label-free spectroscopic tissue characterization using fluorescence excitation-scanning spectral imaging

Spectral imaging approaches provide new possibilities for measuring and discriminating fluorescent molecules in living cells and tissues. These approaches often employ tunable filters and robust image processing algorithms to identify many fluorescent labels in a single image set. Here, we present results from a novel spectral imaging technology that scans the fluorescence excitation spectrum, demonstrating that excitation-scanning hyperspectral image data can discriminate among tissue types and estimate the molecular composition of tissues. This approach allows fast, accurate quantification of many fluorescent species from multivariate image data without the need of exogenous labels or dyes. We evaluated the ability of the excitation-scanning approach to identify endogenous fluorescence signatures in multiple unlabeled tissue types. Signatures were screened using multi-pass principal component analysis. Endmember extraction techniques revealed conserved autofluorescent signatures across multiple tissue types. We further examined the ability to detect known molecular signatures by constructing spectral libraries of common endogenous fluorophores and applying multiple spectral analysis techniques on test images from lung, liver and kidney. Spectral deconvolution revealed structure-specific morphologic contrast generated from pure molecule signatures. These results demonstrate that excitation-scanning spectral imaging, coupled with spectral imaging processing techniques, provides an approach for discriminating among tissue types and assessing the molecular composition of tissues. Additionally, excitation scanning offers the ability to rapidly screen molecular markers across a range of tissues without using fluorescent labels. This approach lays the groundwork for translation of excitation-scanning technologies to clinical imaging platforms.

Synergy of Fluorescence and Near-Infrared Spectroscopy in Detection of Colorectal Cancer

BACKGROUND

Colorectal cancer is one of the most common malignancies worldwide. There is an urgent need for simple and fast methods to improve tumor detection in the diagnostic and intraoperative setting to avoid complications and provide objective information in distinguishing malignant and benign colorectal tissue. Optical spectroscopy methods have recently shown a great potential for this discrimination in different organs.

MATERIALS AND METHODS

In this pilot study, fluorescence emission spectra (excitation: 473 nm) and diffuse reflectance spectra (DRS) of normal and tumor tissues from resected colorectal cancer specimen were measured using fiber optical probes in an ex vivo setting, and the data were subjected to multivariate analysis.

RESULTS

Substantial spectral differences were found in the fluorescence and DRS spectra of colorectal cancer tissue in comparison to benign tissue. The diagnostic potential of a multimode optical system combining both spectroscopic methods was investigated by mathematical combination. Compared with the individual techniques, a higher sensitivity of the joint DRS-fluorescence optical system in the discrimination between malignant and benign colorectal tissue could be observed.

CONCLUSIONS

In the pilot study presented herein, a quick and reliable method to differentiate malignant and benign colorectal tissue ex vivo with different spectroscopic techniques using spectral fiber probes could be established. Joint fluorescence and near-infrared spectroscopy had a higher sensitivity in tissue discrimination and showed to be a promising combination of two spectroscopic methods. Further studies using the synergic effect of fluorescence and DRS spectroscopy are needed to transfer these findings into the in vivo situation.

A novel LED-based 2D-fluorescence spectroscopy system for in-line monitoring of Chinese hamster ovary cell cultivations - Part I

A new two-dimensional fluorescence sensor system was developed for in-line monitoring of mammalian cell cultures. Fluorescence spectroscopy allows for the detection and quantification of naturally occurring intra- and extracellular fluorophores in the cell broth. The fluorescence signals correlate to the cells' current redox state and other relevant process parameters. Cell culture pretests with twelve different excitation wavelengths showed that only three wavelengths account for a vast majority of spectral variation. Accordingly, the newly developed device utilizes three high-power LEDs as excitation sources in combination with a back-thinned CCD-spectrometer for fluorescence detection. This setup was first tested in a lab design of experiments study with process relevant fluorophores proving its suitability for cell culture monitoring with LOD in the μg/L range. The sensor was then integrated into a CHO-K1 cell culture process. The acquired fluorescence spectra of several batches were evaluated using multivariate methods. The resulting batch evolution models were challenged in deviating and "golden batch" validation runs. These first tests showed that the new sensor can trace the cells' metabolic state in a fast and reliable manner. Cellular distress is quickly detected as a deviation from the "golden batch".

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.

Early detection of colorectal adenocarcinoma: a clinical decision support tool based on plasma porphyrin accumulation and risk factors

BACKGROUND

An increase in naturally-occurring porphyrins has been described in the blood of subjects bearing different kinds of tumors, including colorectal, and this is probably related to a systemic alteration of heme metabolism induced by tumor cells. The aim of our study was to develop an artificial neural network (ANN) classifier for early detection of colorectal adenocarcinoma based on plasma porphyrin accumulation and risk factors.

METHODS

We measured the endogenous fluorescence of blood plasma in 100 colorectal adenocarcinoma patients and 112 controls using a conventional spectrofluorometer. Height, weight, personal and family medical history, use of alcohol, red meat, vegetables and tobacco were all recorded. An ANN model was built up from demographic data and from the integral of the fluorescence emission peak in the range 610-650 nm. We used the Receiver Operating Characteristic (ROC) curve to assess performance in distinguishing colorectal adenocarcinoma patients and controls. A liquid chromatography-high resolution mass spectrometry (LC-HRMS) analytical method was employed to identify the agents responsible for native fluorescence.

RESULTS

The fluorescence analysis indicated that the integral of the fluorescence emission peak in the range 610-650 nm was significantly higher in colorectal adenocarcinoma patients than controls (p < 0.0001) and was weakly correlated with the TNM staging (Spearman's rho = 0.224, p = 0.011). LC-HRMS measurements showed that the agents responsible for the fluorescence emission were mainly protoporphyrin-IX (PpIX) and coproporphyrin-I (CpI). The overall accuracy of our ANN model was 88% (87% sensitivity and 90% specificity) with an area under the ROC curve of 0.83.

CONCLUSIONS

These results confirm that tumor cells accumulate a diagnostic level of endogenous porphyrin compounds and suggest that plasma porphyrin concentrations, indirectly measured through fluorescence analysis, may be useful, together with risk factors, as a clinical decision support tool for the early detection of colorectal adenocarcinoma. Our future efforts will be aimed at examining how plasma porphyrin accumulation correlates with survival and response to therapy.

Natural Fluorescence Spectroscopy of Human Blood Plasma in the Diagnosis of Colorectal Cancer: Feasibility Study and Preliminary Results

Aim and background

Fluorescence spectroscopy of biomolecules is considered a promising method to discriminate in vivo normal tissue from malignant tissue at various sites including breast, cervix, lung, and colon. However, only few studies have been reported on the feasibility of exploiting fluorescence spectroscopy of blood to characterize pathological changes usable in diagnostic oncology. In this study, the fluorescence characteristics of human blood plasma have been studied in the visible spectral range in an attempt to discriminate patients with colorectal cancer from subjects of a control population.

Patients and methods

The study involved 341 subjects, including 169 blood donors with no evidence of disease, 143 patients bearing colorectal adenocarcinomas (36 in the colon, 38 in the sigmoid colon and 69 in the rectum), 11 patients with local relapse, 10 patients with familial adenomatous polyposis and 8 with single adenomas. Blood samples were collected from all subjects and plasma fluorescence spectrum was analyzed using a conventional spectrofluorometer.

Results

The intensity of a fluorescence emission peak around 615–635 nm, which could reasonably be ascribed to endogenous porphyrins, was significantly different between patients bearing colorectal cancer and blood donors. The diagnostic capacity of the method was tested by ROC analysis, which resulted in an area under the curve of 0.72, close to that reported for the CEA test.

Conclusion

These results, although preliminary, suggest the potential of fluorescence measurements of blood plasma as an additional method for diagnostic application in colon cancer.

Observation of Zn-photoprotoporphyrin red Autofluorescence in human bronchial cancer using color-fluorescence endoscopy

Background

We observed red autofluorescence emanating from bronchial cancer lesions using a sensitive color-fluorescence endoscopy system. We investigated to clarify the origin of the red autofluorescence.

Methods

The wavelengths of the red autofluorescence emanating from lesions were measured in eight patients using a spectrum analyzer and compared based on pathologic findings. Red autofluorescence at 617.3, 617.4, 619.0, and 617.1 nm was emitted by normal bronchus, inflamed tissue, tissue exhibiting mild dysplasia, and malignant lesions, respectively.

Protoporphyrin, uroporphyrin, and coproporphyrin, the major porphyrin derivatives in human blood, were purchased to determine which porphyrin derivative is the source of red fluorescence when acquired de novo. We synthesized photoporphyrin, Zn-protoporphyrin and Zn-photoprotoporphyrin from protoporphyrin.

Results

Coproporphyrin and uroporphyrin emitted only weak fluorescence. Fluorescence was emitted by our synthesized Zn-photoprotoporphyrin at 625.5 nm and by photoprotoporphyrin at 664.0 nm.

Conclusions

From these results, we conclude that Zn-photoprotoporphyrin was the source of the red autofluorescence observed in bronchial lesions. Zn-protoporphyrin is converted to Zn-photoprotoporphyrin by radiation with excitation light. Our results suggest that red autofluorescence emanating from Zn-photoprotoporphyrin in human tissues could interfere with photodynamic diagnosis using porphyrin derivatives such as Photofrin® and Lazerphyrin® with a sensitive endoscopy system, because color cameras cannot differentiate Zn-photoprotoporphyrin red fluorescence from that of other porphyrin derivatives.

Autofluorescence Spectroscopy for Monitoring Metabolism in Animal Cells and Tissues

Excitation of biological substrates with light at a suitable wavelength can give rise to a light emission in the ultraviolet (UV)-visible, near-infrared (IR) spectral range, called autofluorescence (AF). This is a widespread phenomenon, ascribable to the general presence of biomolecules acting as endogenous fluorophores (EFs) in the organisms of the whole life kingdom. In cytochemistry and histochemistry, AF is often an unwanted signal enhancing the background and affecting in particular the detection of low signals or rare positive labeling spots of exogenous markers. Conversely, AF is increasingly considered as a powerful diagnostic tool because of its role as an intrinsic biomarker directly dependent on the nature, amount, and microenvironment of the EFs, in a strict relationship with metabolic processes and structural organization of cells and tissues. As a consequence, AF carries multiple information that can be decrypted by a proper analysis of the overall emission signal, allowing the characterization and monitoring of cell metabolism in situ, in real time and in the absence of perturbation from exogenous markers. In the animal kingdom, AF studies at the cellular level take advantage of the essential presence of NAD(P)H and flavins, primarily acting as coenzymes at multiple steps of common metabolic pathways for energy production, reductive biosynthesis and antioxidant defense. Additional EFs such as vitamin A, porphyrins, lipofuscins, proteins, and neuromediators can be detected in different kinds of cells and bulk tissues, and can be exploited as photophysical biomarkers of specific normal or altered morphofunctional properties, from the retinoid storage in the liver to aging processes, metabolic disorders or cell transformation processes. The AF phenomenon involves all living system, and literature reports numerous investigations and diagnostic applications of AF, taking advantage of continuously developing self-assembled or commercial instrumentation and measuring procedures, making almost impossible to provide their comprehensive description. Therefore a brief summary of the history of AF observations and of the development of measuring systems is provided, along with a description of the most common EFs and their metabolic significance. From our direct experience, examples of AF imaging and microspectrofluorometric procedures performed under a single excitation in the near-UV range for cell and tissue metabolism studies are then reported.

Real time optical Biopsy: Time-resolved Fluorescence Spectroscopy instrumentation and validation

The Time-resolved fluorescence spectroscopy (TR-FS) has the potential to differentiate tumor and normal tissue in real time during surgical excision. In this manuscript, we describe the design of a novel TR-FS device, along with preliminary data on detection accuracy for fluorophores in a mixture. The instrument is capable of near real-time fluorescence lifetime acquisition in multiple spectral bands and analysis. It is also able to recover fluorescence lifetime with sub-20ps accuracy as validated with individual organic fluorescence dyes and dye mixtures yielding lifetime values for standard fluorescence dyes that closely match with published data. We also show that TR-FS is able to quantify the relative concentration of fluorescence dyes in a mixture by the unmixing of lifetime decays. We show that the TR-FS prototype is able to identify in near-real time the concentrations of dyes in a complex mixture based on previously trained data. As a result, we demonstrate that in complex mixtures of fluorophores, the relative concentration information is encoded in the fluorescence lifetime across multiple spectral bands. We show for the first time the temporal and spectral measurements of a mixture of fluorochromes and the ability to differentiate relative concentrations of each fluorochrome mixture in real time.

Autofluorescence spectroscopy and imaging: a tool for biomedical research and diagnosis

Native fluorescence, or autofluorescence (AF), consists in the emission of light in the UV-visible, near-IR spectral range when biological substrates are excited with light at suitable wavelength. This is a well-known phenomenon, and the strict relationship of many endogenous fluorophores with morphofunctional properties of the living systems, influencing their AF emission features, offers an extremely powerful resource for directly monitoring the biological substrate condition. Starting from the last century, the technological progresses in microscopy and spectrofluorometry were convoying attention of the scientific community to this phenomenon. In the future, the interest in the autofluorescence will certainly continue. Current instrumentation and analytical procedures will likely be overcome by the unceasing progress in new devices for AF detection and data interpretation, while a progress is expected in the search and characterization of endogenous fluorophores and their roles as intrinsic biomarkers.

Discrimination among melanoma, nevi, and normal skin by using synchronous luminescence spectroscopy

Novel optical spectroscopy and imaging methods may be valuable in the early detection of cancer. This paper reports differences in the luminescence responses of pigmented skin lesions (melanomas and nevi) and apparently normal non-pigmented human skin, based on analyses of synchronous luminescence spectroscopy measurements. Measurements were performed in the excitation range of 330-545 nm, with synchronous intervals varying from 30-120 nm. Normal skin, nevi, and melanomas differ in the way they fluoresce, and these differences are more distinct in the synchronous fluorescence spectra than in the conventional emission and excitation spectra. The differences in the fluorescence characteristics of pigmented and normal skin samples were ascribed to differences in concentrations of endogenous fluorophores and chromophores. Principal component and linear discriminant analysis of the synchronous spectra measured at different synchronous intervals showed that the greatest variance among the sample groups was at the 70 nm interval spectra. These spectra were then used to create partial least squares discriminant analysis-based classification models. Evaluation of the quality of these models from the receiver operating characteristic curves showed they performed well, with a maximum value of 1 for the area under the curve for melanoma detection. Hence, synchronous luminescence spectroscopy coupled with statistical methods may be advantageous in the early detection of skin cancer.

Intraoperative fluorescence-guided resection of high-grade gliomas: a comparison of the present techniques and evolution of future strategies

OBJECTIVE

Fluorescence guidance has a demonstrated potential in maximizing the extent of high-grade glioma resection. Different fluorophores (fluorescent biomarkers), including 5-aminolevulinic acid (5-ALA) and fluorescein, have been examined with the use of several imaging techniques. Our goal was to review the state of this technology and discuss strategies for more widespread adoption.

METHODS

We performed a Medline search using the key words "fluorescence," "intraoperative fluorescence-guided resection," "intraoperative image-guided resection," and "brain glioma" for articles from 1960 until the present. This initial search revealed 267 articles. Each abstract and article was reviewed and the reference lists from select articles were further evaluated for relevance. A total of 64 articles included information about the role of fluorescence in resection of high-grade gliomas and therefore were selectively included for our analysis.

RESULTS

5-ALA and fluorescein sodium have shown promise as fluorescent markers in detecting residual tumor intraoperatively. These techniques have demonstrated a significant increase in the extent of tumor resection. Regulatory barriers have limited the use of 5-ALA and technological challenges have restricted the use of fluorescein and its derivatives in the United States. Limitations to this technology currently exist, such as the fact that fluorescence at tumor margins is not always reliable for identification of tumor-brain interface.

CONCLUSIONS

These techniques are safe and effective for increasing gross total resection. The development of more tumor-specific fluorophores is needed to resolve problems with subjective interpretation of fluorescent signal at tumor margins. Techniques such as quantum dots and polymer or iron oxide-based nanoparticles have shown promise as potential future tools.

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.

In vivo diagnosis of colonic precancer and cancer using near-infrared autofluorescence spectroscopy and biochemical modeling

The aim of this study is to evaluate the biochemical foundation and clinical capability of an image-guided near-infrared (NIR) autofluorescence (AF) spectroscopy technique for in vivo diagnosis of colonic malignancies during clinical colonoscopy. A novel endoscopic fiber-optic AF system was utilized for in vivo NIR AF measurements at 785 nm excitation. A total of 263 in vivo NIR AF spectra of colonic tissues were measured from 100 patients, in which 164 spectra were from benign tissue (116 normal and 48 hyperplastic polyps), 34 spectra were from precancer (adenomatous polyps), and 65 spectra were from cancer. The non-negativity constrained least squares minimization biochemical modeling was explored to estimate the biochemical compositions of colonic tissue using nine basis reference spectra from the representative biochemicals (i.e., collagen I, elastin, β-nicotinamide adenine dinucleotide, flavin adenine dinucleotide, L-tryptophan, hematoporphyrin, 4-pyridoxic acid, pyridoxal 5'-phosphate, and water) associated with structural or cellular metabolic progression in colonic precancer and cancer. High-quality in vivo NIR AF spectra in the spectral range of 810 to 1000 nm were acquired from colonic benign, precancerous, and cancerous mucosa under white-light reflectance endoscopic imaging guidance. Partial least squares discriminant analysis, together with the leave-one tissue site-out, cross validation on in vivo NIR AF spectra yields diagnostic sensitivities of 85.4%, 76.5%, and 84.6%, and specificities of 89.9%, 93.4%, and 91.4%, respectively, for classification of benign, precancer, and cancer in the colon. This work demonstrates that image-guided NIR AF spectroscopy in conjunction with biochemical modeling has promising potential for improving in vivo detection and diagnosis of colonic precancer and cancer during clinical colonoscopic screening.

Fluorescence lifetime spectroscopy for guided therapy of brain tumors

This study evaluates the potential of time-resolved laser induced fluorescence spectroscopy (TR-LIFS) as intra-operative tool for the delineation of brain tumor from normal brain. Forty two patients undergoing glioma (WHO grade I-IV) surgery were enrolled in this study. A TR-LIFS prototype apparatus (gated detection, fast digitizer) was used to induce in-vivo fluorescence using a pulsed N2 laser (337 nm excitation, 0.7 ns pulse width) and to record the time-resolved spectrum (360-550 nm range, 10 nm interval). The sites of TR-LIFS measurement were validated by conventional histopathology (H&E staining). Parameters derived from the TR-LIFS data including intensity values and time-resolved intensity decay features (average fluorescence lifetime and Laguerre coefficients values) were used for tissue characterization and classification. 71 areas of tumor and normal brain were analyzed. Several parameters allowed for the differentiation of distinct tissue types. For example, normal cortex (N=35) and normal white matter (N=12) exhibit a longer-lasting fluorescence emission at 390 nm (τ390=2.12±0.10 ns) when compared with 460 nm (τ460=1.16±0.08 ns). High grade glioma (grades III and IV) samples (N=17) demonstrate emission peaks at 460 nm, with large variation at 390 nm while low grade glioma (I and II) samples (N=7) demonstrated a peak fluorescence emission at 460 nm. A linear discriminant algorithm allowed for the classification of low-grade gliomas with 100% sensitivity and 98% specificity. High-grade glioma demonstrated a high degree of heterogeneity thus reducing the discrimination accuracy of these tumors to 47% sensitivity and 94% specificity. Current findings demonstrate that TR-LIFS holds the potential to diagnose brain tumors intra-operatively and to provide a valuable tool for aiding the neurosurgeon-neuropathologist team in to rapidly distinguish between tumor and normal brain during surgery.

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 in biology and medicine: slices of life

Multispectral imaging (MSI) is currently in a period of transition from its role as an exotic technique to its being offered in one form or another by all the major microscopy manufacturers. This is because it provides solutions to some of the major challenges in fluorescence-based imaging, namely ameliorating the consequences of the presence of autofluorescence and the need to easily accommodate relatively high levels of signal multiplexing. MSI, which spectrally characterizes and computationally eliminates autofluorescence, enhances the signal-to-background dramatically, revealing otherwise obscured targets. While this article concentrates on examples derived from liquid-crystal tunable filter-based technology, the intent is to showcase the advantages of multispectral imaging in general. Some technologies used to generate multispectral images are compatible with only particular optical configurations, such as point-scanning laser confocal microscopy. Band-sequential approaches, such as those afforded by liquid-crystal tunable filters (LCTFs), can be conveniently coupled with a variety of imaging modalities, which, in addition to fluorescence microscopy, include brightfield (nonfluorescent) microscopy as well as small-animal, noninvasive in-vivo imaging. Brightfield microscopy is the chosen format for histopathology, which relies on immunohistochemistry to provide molecularly resolved clinical information. However, in contrast to fluorescent labels, multiple chromogens, if they spatially overlap, are much harder to separate and quantitate, unless MSI approaches are used. In-vivo imaging is a rapidly growing field with applications in basic biology, drug discovery, and clinical medicine. The sensitivity of fluorescence-based in-vivo imaging, as with fluorescence microscopy, can be limited by the presence of significant autofluorescence, a limitation which can be overcome through the utilization of MSI.

Autofluorescence characterisation of isolated whole crypts and primary cultured human epithelial cells from normal, hyperplastic, and adenomatous colonic mucosa

BACKGROUND/AIMS

In vivo autofluorescence endoscopic imaging and spectroscopy have been used to detect and differentiate benign (hyperplastic) and preneoplastic (adenomatous) colonic lesions. This fluorescence is composed of contributions from the epithelium, lamina propria, and submucosa. Because epithelial autofluorescence in normal and diseased tissues is poorly understood, this was the focus of the present study.

METHODS

Whole colonic crypts were isolated, and short term primary cultures of epithelial cells were established from biopsies of normal, hyperplastic, and adenomatous colon. Autofluorescence (488 nm excitation) was examined by confocal fluorescence microscopy. Fluorescently labelled organelle probes and transmission electron microscopy were used to identify subcellular sources of fluorescence.

RESULTS

Mitochondria and lysosomes were identified as the main intracellular fluorescent components in all cell types. Normal and hyperplastic epithelial cells were weakly autofluorescent and had similar numbers of mitochondria and lysosomes, whereas adenomatous (dysplastic) epithelial cells showed much higher autofluorescence, and numerous highly autofluorescent lysosomal (lipofuscin) granules.

CONCLUSIONS

Short term primary cell cultures from endoscopic biopsies provide a novel model to understand differences in colonic tissue autofluorescence at the glandular (crypt) and cellular levels. The differences between normal, hyperplastic, and adenomatous epithelial cells are attributed in part to differences in the intrinsic numbers of mitochondria and lysosomes. This suggests that the detection of colonic epithelial fluorescence alone, if possible, may be sufficient to differentiate benign (hyperplastic) from preneoplastic and neoplastic (adenomatous) colonic intramucosal lesions during in vivo fluorescence endoscopy. Furthermore, highly orange/red autofluorescent intracellular granules found only in dysplastic epithelial cells may serve as a potential biomarker.

Noninvasive imaging of oral premalignancy and malignancy

Early detection of cancer and its precursors remains the best way to ensure patient survival and quality of life. Our specific aim is to test a multimodality approach to noninvasive diagnostics of oral premalignancy and malignancy. In the hamster cheek pouch model (120 hamsters), in vivo optical coherence tomography (OCT) and optical Doppler tomography (ODT) map epithelial, subepithelial, and vascular change throughout carcinogenesis. In vivo multiwavelength multiphoton (MPM) and second-harmonic generated (SHG) fluorescence techniques provided parallel data on surface and subsurface tissue structure, specifically collagen presence and structure, cellular presence, and vasculature. Images are diagnosed by two blinded, prestandardized investigators using a scale from 0 to 6 for all modalities. After sacrifice, histopathology is evaluated on a scale of 0 to 6. Imaging data are reproducibly obtained with good accuracy. Carcinogenesis-related structural and vascular changes are clearly visible to tissue depths of 2 mm. Sensitivity (OCT/ODT alone, 71 to 88%; OCT+MPMSHG, 79 to 91%) and specificity (OCT alone, 62 to 83%; OCT+MPMSHG, 67 to 90%) compare well with conventional techniques. Our conclusions are that OCT/ODT and MPM/SHG are promising noninvasive in vivo diagnostic modalities for oral dysplasia and malignancy.

Autofluorescence excitation-emission matrices for diagnosis of colonic cancer

AIM: To investigate the autofluorescence spectroscopic differences in normal and adenomatous colonic tissues and to determine the optimal excitation wavelengths for subsequent study and clinical application.

METHODS: Normal and adenomatous colonic tissues were obtained from patients during surgery. A FL/FS920 combined TCSPC spectrofluorimeter and a lifetime spectr-ometer system were used for fluorescence measurement. Fluorescence excitation wavelengths varying from 260 to 540 nm were used to induce the autofluorescence spectra, and the corresponding emission spectra were recorded from a range starting 20 nm above the excitation wavelength and extending to 800 nm. Emission spectra were assembled into a three-dimensional fluorescence spectroscopy and an excitation-emission matrix (EEM) to exploit endogenous fluorophores and diagnostic information. Then emission spectra of normal and adenomatous colonic tissues at certain excitation wavelengths were compared to determine the optimal excitation wavelengths for diagnosis of colonic cancer.

RESULTS: When compared to normal tissues, low NAD (P)H and FAD, but high amino acids and endogenous phorphyrins of protoporphyrin IX characterized the high-grade malignant colonic tissues. The optimal excitation wavelengths for diagnosis of colonic cancer were about 340, 380, 460, and 540 nm.

CONCLUSION: Significant differences in autofluorescence peaks and its intensities can be observed in normal and adenomatous colonic tissues. Autofluorescence EEMs are able to identify colonic tissues.

Autofluorescence spectroscopy of rat liver during experimental transplantation procedure. An approach for hepatic metabolism assessment

Ischemia-reperfusion injury, a major cause of organ metabolic alterations and consequent dysfunction in liver transplantation, could be overcome by optimizing organ preservation procedures. The potential of autofluorescence analysis was investigated with the aim to define parameters suitable for in vivo monitoring tissue functionality. Spectrofluorometric analysis was performed on explanted rat livers during cold storage, under standard (4 degrees C University of Wisconsin medium for 20 h) and purposely damaging (4 degrees C Eurocollins medium for 20, 43 and 72 h) preservation conditions, and reperfusion (rewarming-reoxygenation). For both preservation conditions, cold hypoxia caused a signal amplitude increase, mainly attributable to NAD(P)H, and a spectral shape modification, ascribable to changes in the relative contributions of NAD(P)H and flavins, as a result of the tissue reduced state enhancement. Upon rewarming-reoxygenation the autofluorescence signal decreased with a rate depending on the preservation conditions. The time constant changed according to the extent of the liver functionality impairment, as assessed by conventional biochemical and histochemical analyses, thus providing a parameter exploitable for an in situ, real time monitoring of the efficacy of experimental preservation procedures.

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.

The fluorescence of thyroid tissue

OBJECTIVE

To investigate the fluorescent characteristics of different thyroid tissues.

STUDY DESIGN

Fresh ex vivo thyroid tissue was surfaced scanned with a fluorescence spectrophotometer. Resultant spectra were evaluated via interpeak ratios.

RESULTS

Interpeak ratios of all histologies were found to be significantly different from each other (P < 0.001). The diagnostic sensitivity and specificity of fluorescent spectroscopy was 86% and 91% for thyroid nodule capsule, 78% and 59% for papillary thyroid carcinoma, and 82% and 63% for normal thyroid, respectively.

CONCLUSION

Fluorescent spectroscopy can been used to identify significant differences in the fluorescent characteristics of various thyroid histologies.

SIGNIFICANCE

This study is the first investigation of the fluorescence of thyroid tissue. The diagnostic ability of fluorescent spectrometry may allow it to be used as a localization aid for fine needle aspiration, using optical fiber probes. Further investigations may enhance the sensitivity and specificity of fluorescent spectrometry allowing it to replace or compliment fine needle aspiration.

EBM RATING

B-3.

In vivo autofluorescence spectrofluorometry of central serotonin

The autofluorescence properties of serotonin (5-HT) were investigated by light spectrofluorometry in in vitro, ex vivo and in vivo experiments. Ex vivo samples were prepared from rat brain regions containing serotonin (5-HT) i.e. cortex, striatum, hippocampus. Rats were untreated (controls) or previously submitted to chronic behavioural or pharmacological treatments known to affect endogenous 5-HT levels. Autofluorescence analysis (excitation: 366 nm) on hippocampus homogenates supplied with exogenous 5-HT revealed spectral alterations attributable to changes of endogenous 5-HT levels. In vivo, real time fluorescence studies were performed via a 50 microm diameter optic fiber probe stereotaxically implanted into selected brain areas of anaesthetised rats treated with fluoxetine or 5-OH-tryptophan. All autofluorescence data were consistent with those obtained in parallel experiments performed with ex vivo or in vivo voltammetry, confirming that auto-fluorescence spectroscopy is a suitable technique for the direct assessment of fluorescent neurotransmitters. This is a reliable evidence of the in vivo application of spectroscopy together with optic fiber probe for in vivo, in situ and real time measurement of 5-HT in discrete brain areas.

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.

Molecular fluorescence excitation-emission matrices relevant to tissue spectroscopy

In vivo and ex vivo studies of fluorescence from endogenous and exogenous molecules in tissues and cells are common for applications such as detection or characterization of early disease. A systematic determination of the excitation-emission matrices (EEM) of known and putative endogenous fluorophores and a number of exogenous fluorescent photodynamic therapy drugs has been performed in solution. The excitation wavelength range was 250-520 nm, with fluorescence emission spectra collected in the range 260-750 nm. In addition, EEM of intact normal and adenomatous human colon tissues are presented as an example of the relationship to the EEM of constituent fluorophores and illustrating the effects of tissue chromophore absorption. As a means to make this large quantity of spectral data generally available, an interactive database has been developed. This currently includes EEM and also absorption spectra of 35 different endogenous and exogenous fluorophores and chromophores and six photosensitizing agents. It is intended to maintain and extend this database in the public domain, accessible through the Photochemistry and Photobiology website (http://www.aspjournal. com/).

Autofluorescence Spectrofluorometry of central nervous system (CNS) neuromediators

BACKGROUND AND OBJECTIVES

Changes in the neurotransmitter 5-hydroxytriptamine (5-HT) are related to psychiatric diseases such as depression and anxiety. In this study, 5-HT autofluorescence properties were investigated in solution and in biological tissues.

STUDY DESIGN/MATERIALS AND METHODS

Spectrofluorometric characterization was performed on ex vivo samples (tissue sections, homogenates) of the 5-HT-rich brain region hippocampus from rats untreated or treated to affect endogenous 5-HT levels; in vivo, with a 50 solidus in circle optic fiber probe positioned via stereotaxis.

RESULTS

5-HT exhibited minor excitation and emission bands at wavelengths longer than the well known excitation and emission bands in the UV region, 250-320 nm. Spectrofluorometric measurements under 366 nm excitation on homogenates supplied with 5-HT or belonging to treated rats revealed spectral alterations attributable to changes in the amount of 5-HT. Ex vivo and in vivo autofluorescence data were consistent with those obtained by conventional voltammetry.

CONCLUSIONS

Autofluorescence spectroscopy potential is confirmed as a suitable technique for the direct measurement of neurotransmitters.

In vivo autofluorescence spectroscopy of oral premalignant and malignant lesions: distortion of fluorescence intensity by submucous fibrosis

BACKGROUND AND OBJECTIVES

To test whether autofluorescence spectroscopy can be used for the diagnosis of oral neoplasia in a high-risk population, we characterized the in vivo autofluorescence spectra from oral submucous fibrosis (OSF) lesions and oral premalignant and malignant lesions in both OSF and non-OSF patients.

STUDY DESIGN/MATERIALS AND METHODS

Autofluorescence emission spectra were measured under the excitation wavelength of 330 nm, using a Xenon lamp-based fluorospectrometer coupled to a handheld optical fiber probe. Autofluorescence spectroscopies were analyzed among patients with OSF lesions, and oral lesions of epithelial hyperkeratosis (EH), epithelial dysplasia (ED), and squamous cell carcinomas (SCC) and normal oral mucosa (NOM) of healthy volunteers.

RESULTS

We found that the most intensely autofluorescence emission peaks occurred at 380 nm and 460 nm. For comparing the spectral patterns among different groups of oral lesions and NOM, ratios of the area under the spectrum of 460+/-10 nm to that under the spectrum of 380+/-10 nm (denoted as A(460+/-10nm)/A(380+/-10nm)) were calculated. The mean ratio values increased gradually from OSF to NOM, to EH and ED, and to SCC. The ANOVA test showed significant differences in the ratio value among all categories of samples (P<0.01). On the other hand, we found that EH, ED, and SCC lesions on OSF patients had distorted autofluorescence intensity. The mean ratio values of EH, ED, and SCC between non-OSF and OSF patients show significant differences. Furthermore, an ANOVA test showed NOM is not distinguishable from EH and ED lesions on oral fibrotic mucosa (P>0.05).

CONCLUSIONS

Autofluorescence spectroscopy can be used to diagnose EH, ED, and SCC lesions in non-OSF patients but not in OSF patients.

Fluorescence emission-based detection and diagnosis of malignancy

Over the past decades, laser use in medicine has expanded from its initial application as a light-based scalpel to a plethora of clinical uses, ranging from surgical treatment through composite polymerization, dental ablation, vision correction, and skin resurfacing to diverse diagnostic modalities. Recently, the concept of light-based diagnostics and therapy has come under investigation. Low light intensities are used to excite endogenous or exogenous fluorophores, some of which have characteristic fluorescence emissions in pathological tissues. Thus, premalignancy and malignancy potentially can be detected and diagnosed. Photosensitized superficial lesions can subsequently be destroyed selectively by using higher intensities of laser light. The application of fluorescence emission-based detection and diagnosis of precancer and cancer is reviewed, based on its application to the oral cavity-the author's primary anatomical area of expertise. This approach is justified as the same principles apply throughout the human body; to any area accessible to the clinician either directly or by some sort of fiber-optic probe.

Auto-fluorescence spectra of oral submucous fibrosis

BACKGROUND

Oral submucous fibrosis (OSF) is a chronic oral mucosal disease characterized by progressive deposition of collagen in the subepithelial connective tissue and epithelial atrophy. Previous studies have shown that at 330-nm excitation, the 380- and 460-nm emission peaks of the auto-fluorescence spectra for oral mucosal tissues reflect the collagen content in the subepithelial connective tissue and the nicotinamide adenine dinucleotide phosphate (NADH) content in the epithelial cells, respectively. Therefore, at 330-nm excitation OSF mucosa may have a higher 380-nm emission peak and a lower 460-nm emission peak than the normal oral mucosa (NOM).

METHODS

To test the above hypothesis, we measured the in vivo auto-fluorescence spectra of 59 OSF mucosal sites and compared the measured spectra with auto-fluorescence spectra obtained from 15 NOM samples from 15 healthy volunteers, five samples of friction hyperkeratosis (histologic diagnosis, hyperkeratosis and acanthosis) on OSF buccal mucosa (FHOSF), and 29 samples of oral leukoplakia (histologic diagnosis, hyperkeratosis and acanthosis) on OSF buccal mucosa (OLOSF).

RESULTS

We found that the spectrum of the OSF mucosa had a significantly higher 380-nm emission peak and a significantly lower 460-nm emission peak than the spectra of NOM, FHOSF, and OLOSF samples. When the mean (+/-SD) fluorescence intensities at 380 +/- 15 nm (I380 +/- 15 nm) and 460 +/- 15 nm (I460 +/- 15 nm) emission peaks and the mean ratio of I460 +/- 15 nm/I380 +/- 15 nm were compared between groups, we found that OSF group had a significantly higher mean value of I380 +/- 15 nm, a significantly lower mean value of I460 +/- 15 nm, and a significantly lower mean ratio of I460 +/- 15 nm/I380 +/- 15 nm than the NOM, FHOSF, and OLOSF groups (P < 0.001). However, no significant differences in the mean values of I380 +/- 15 nm, I460 +/- 15 nm, and ratio of I460 +/- 15 nm/I380 +/- 15 nm were found between NOM and FHOSF or OLOSF samples as well as between FHOSF and OLOSF samples (P > 0.05).

CONCLUSION

Because OSF mucosa has a very unique pattern of auto-fluorescence spectrum, we conclude that auto-fluorescence spectroscopy is a good method for real-time diagnosis of OSF.

Temporally and spectrally resolved fluorescence spectroscopy for the detection of high grade dysplasia in Barrett's esophagus

BACKGROUND AND OBJECTIVES

Temporal and spectral fluorescence spectroscopy can identify adenomatous colonic polyps accurately. In this study, these techniques were examined as a potential means of improving the surveillance of high grade dysplasia (HGD) in Barrett's esophagus (BE).

STUDY DESIGN/MATERIALS AND METHODS

Using excitation wavelengths of 337 and 400 nm, 148 fluorescence spectra, and 108 transient decay profiles (at 550 +/- 20 nm) were obtained endoscopically in 37 patients. Corresponding biopsies were collected and classified as carcinoma, HGD, or low risk tissue (LRT) [non-dysplastic BE, indefinite for dysplasia (IFD), and low grade dysplasia (LGD)]. Diagnostic algorithms were developed retrospectively using linear discriminant analysis (LDA) to separate LRT from HGD.

RESULTS

LDA produced diagnostic algorithms based solely on spectral data. Moderate levels of sensitivity (Se) and specificity (Sp) were obtained for both 337 nm (Se = 74%, Sp = 67%) and 400 nm (Se = 74%, Sp = 85%) excitation.

CONCLUSIONS

In the diagnosis of HGD in BE, steady-state fluorescence was more effective than time-resolved data, and excitation at 400 nm excitation was more effective than 337 nm. While fluorescence-targeted biopsy is approaching clinical usefulness, increased sensitivity to dysplastic changes-possibly through modification of system parameters-is needed to improve accuracy levels.

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.

Diagnostic potential of autofluorescence for an assisted intraoperative delineation of glioblastoma resection margins

The intrinsic autofluorescence properties of biological tissues can be affected by the occurrence of histological and biochemical alterations induced by pathological processes. In this study the potential of autofluorescence to distinguish tumor from normal tissues was investigated with the view of a real-time diagnostic application in neurosurgery to delineate glioblastoma resection margins. The autofluorescence properties of nonneoplastic and neoplastic tissues were analyzed on tissue sections and homogenates by means of a microspectrofluorometer, and directly on patients affected by glioblastoma multiforme, during surgery, with a fiber-optic probe. Scan-microspectrofluorometric analysis on tissue sections evidenced a reduction of emission intensity and a broadening of the main emission band, along with a redshift of the peak position, from peritumoral nonneoplastic to neoplastic tissues. Differences in both spectral shape and signal amplitude were found in patients when the glioblastoma lesion autofluorescence was compared with those of cortex and white matter taken as healthy tissues. Both biochemical composition and histological organization contribute to modify the autofluorescence emission of neoplastic, with respect to nonneoplastic, brain tissues. The differences found in the in vivo analysis confirm the prospects for improving the efficacy of tumor resection margin delineation in neurosurgery.

Autofluorescence spectroscopy for in vivo diagnosis of DMBA-induced hamster buccal pouch pre-cancers and cancers

BACKGROUND

Our previous ex vivo study has shown that autofluorescence spectroscopy at 330-nm excitation can discriminate specimens of normal buccal pouch mucosa (normal), epithelial hyperkeratosis (hyperkeratosis), epithelial dysplasia (dysplasia), and squamous cell carcinoma (SCC) taken from DMBA-treated hamsters by using the method of partial least-squares discriminant analysis (PLSDA).

METHODS

This study used a fiber optics-based fluorescence spectroscopy system to measure the autofluorescence spectra of 23 normal, 14 hyperkeratosis, 28 dysplasia, and 10 SCC samples in vivo. PLSDA with cross-validation was used to analyze the autofluorescence spectral data of all samples.

RESULTS

We found that at 330-nm excitation, the autofluorescence spectra of all samples had two main peaks: one at 380 nm and the other at 460 nm. The hyperkeratosis samples had a higher 380-nm emission peak (EP) and a lower 460-nm EP than normal samples. On the contrary, the dysplasia samples had a lower 380-nm EP and a higher 460-nm EP than normal samples. Furthermore, the SCC samples had a much lower 380-nm EP and a much higher 460-nm EP than all other samples. To quantify the spectral changes during the progression of oral carcinogenesis, ratios of the area under the spectrum of 380 +/- 15 nm to that under the spectrum of 460 +/- 15 nm (denoted as A(380 +/- 15 nm)/A(460 +/- 15 nm)) for all samples were calculated. The mean ratio values of A(380 +/- 15 nm)/A(460 +/- 15 nm) decreased gradually from hyperkeratosis to normal, to dysplasia, and to SCC samples. Significant differences in this mean ratio were found between any two groups of normal, hyperkeratosis, dysplasia, and SCC samples. By choosing proper thresholds, PLSDA with cross-validation could provide an accurate identification rate of 86% for hyperkeratosis, of 87% for normal, and of 89% for dysplasia samples. In addition, by choosing a proper threshold, we could separate benign (normal and hyperkeratosis) from dysplasia or SCC tissues with a sensitivity of 92% and a specificity of 95%.

CONCLUSION

Our results indicate that the autofluorescence spectroscopy technique is a useful diagnostic tool for in vivo diagnosis of oral pre-cancers and cancers in DMBA-induced hamster buccal pouch carcinogenesis model.