Study of the fluorescence properties of normal and neoplastic human cervical tissue

Alzheimer's disease diagnosis by blood plasma molecular fluorescence spectroscopy (EEM)

Despite tremendous research advances in detecting Alzheimer's disease (AD), traditional diagnostic tests remain expensive, time-consuming or invasive. The search for a low-cost, rapid, and minimally invasive test has marked a new era of research and technological developments toward establishing blood-based AD biomarkers. The current study has employed excitation-emission matrices (EEM) of fluorescence spectroscopy combined with machine learning to diagnose AD using blood plasma samples from 230 individuals (83 AD patients from 147 healthy controls). To evaluate the performance of the classification algorithms, we calculated the commonly used figures of merit (accuracy, sensitivity and specificity) and figures of merit that take into account the samples unbalance and the discrimination power of the models, as F₂-score (F₂), Matthews correlation coefficient (MCC) and test effectiveness (\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\delta$$\end{document}δ). The classification models achieved satisfactory results: Parallel Factor Analysis with Quadratic Discriminant Analysis (PARAFAC-QDA) with 83.33% sensitivity, 100% specificity, 86.21% F₂; and Tucker3-QDA with 91.67% sensitivity, 95.45% specificity and 91.67% F₂. In addition, the classifiers show high overall performance with 94.12% accuracy and 0.87 MCC. Regarding the discrimination power between healthy and AD patients, the classification algorithms showed high effectiveness with the mean scores separated by three or more standard deviations. The PARAFAC's spectral profiles and the wavelength values from both models loading profiles can be used in future research to relate this information to plasma AD biomarkers. Our results point to a rapid, low-cost and minimally invasive blood-based method for AD diagnosis.

An effective approach to the early diagnosis of colorectal cancer based on three-dimensional fluorescence spectra of human blood plasma

Colorectal cancer (CRC) is a common malignancy in the gastrointestinal tract, and its screening rates remain relatively low in the general population due to the lack of specific symptoms and effective methods. It is still in urgent need to develop rapid and reliable approach to the early diagnosis of CRC. Herein, based on the three-dimensional (3D) fluorescence spectra of human blood plasma, a combination strategy of Tchebichef image moments coupled with partial least squares-discriminate analysis (TM-PLS-DA) was proposed for the detection of CRC from three classes (CRC samples, adenomas samples and non-malignant findings). The established TM-PLS-DA classification model provided an 84 % correct classification for CRC prediction. Venetian blinds 10-fold cross validation was carried out. The error rates both in cross validation and test sets were less than 0.16. Sensitivity and specificity for CRC prediction were 0.95 and 0.88, respectively. At the same time, the diagnostic capacity of the proposed method was tested by receiver operating characteristics (ROC) analysis with area under the curve (AUC) of 0.94 for CRC diagnosis. These results demonstrate that the proposed TM-PLS-DA method based on the 3D fluorescence spectra of blood plasma has great advantage for the accurate CRC detection, which will provide a potential alternative approach for cancer diagnostics.

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.

Diagnostic imaging of cervical intraepithelial neoplasia based on hematoxylin and eosin fluorescence

Background

Pathological classification of cervical intraepithelial neoplasia (CIN) is problematic as it relies on subjective criteria. We developed an imaging method that uses spectroscopy to assess the fluorescent intensity of cervical biopsies derived directly from hematoxylin and eosin (H&E) stained tissues.

Methods

Archived H&E slides were identified containing normal cervical tissue, CIN I, and CIN III cases, from a Community Hospital and an Academic Medical Center. Cases were obtained by consensus review of at least 2 senior pathologists. Images from H&E slides were captured first with bright field illumination and then with fluorescent illumination. We used a Zeiss Axio Observer Z1 microscope and an AxioVision 4.6.3-AP1 camera at excitation wavelength of 450–490 nm with emission captured at 515–565 nm. The 32-bit grayscale fluorescence images were used for image analysis.

Results

We reviewed 108 slides: 46 normal, 33 CIN I and 29 CIN III. Fluorescent intensity increased progressively in normal epithelial tissue as cells matured and advanced from the basal to superficial regions of the epithelium. In CIN I cases this change was less prominent as compared to normal. In high grade CIN lesions, there was a slight or no increase in fluorescent intensity. All groups examined were statistically different.

Conclusion

Presently, there are no markers to help in classification of CIN I-III lesions. Our imaging method may complement standard H&E pathological review and provide objective criteria to support the CIN diagnosis.

Hyperspectral diagnostic imaging of the cervix: report on a new investigational device

OBJECTIVE

To describe our experience with a noncontact in vivo fluorescence imaging device for the detection and localization of cervical intraepithelial neoplasia (CIN).

MATERIALS AND METHODS

Sixty-two women with abnormal Papanicolaou (Pap) smears, and 4 women with normal Pap smears, were recruited to undergo fluorescence imaging of the cervix during colposcopy. After topically applying dilute acetic acid, the surface of the cervix was scanned with 365 nm ultraviolet light for about 12 sec. Colposcopy and biopsies of visualized lesions were then performed. The fluorescence emission curves generated by normal cervical tissue and various states of cervical pathology were inspected and assigned relative scores of 1-5 based on the height and slope of the curves at peak fluorescence emissions. A score of 1 indicated a curve with high magnitude and distinct peak, and a score of 5 described a curve of low magnitude and rounded/flattened peak. Scores of 2-4 represented curves with incremental changes of about 25% in the height of the curve between scores of 1 and 5. Biopsies were classified as high grade (HG, CIN 2/3), low grade (LG, HPV/CIN 1), or nondysplastic (ND). Among women with abnormal Pap smears, only those who had biopsies with concordant interpretations by two independent pathologists were included in the descriptive analysis. All of the patients with normal Pap smears were included.

RESULTS

A total of 35 women were included in the analysis. Of 62 women with abnormal Pap smears who underwent fluorescence imaging and colposcopy, 31 met the inclusion criteria. Among these 31 women, Pap smears consisted of 6 atypical squamous cells of undetermined significance (ASCUS), 16 low-grade squamous intraepithelial lesions (LGSILs), and 9 high-grade squamous intraepithelial lesions (HGSILs). Of the 4 women with normal Pap smears, 1 had an abnormal colposcopy and a nondysplastic biopsy. Among all 35 women, 42 total biopsies were included, consisting of 11 HG, 25 LG, and 6 ND. Normal squamous tissue generated a score of 1, normal metaplastic tissue a score of 2 or 3, and normal columnar tissue of score of 5 in 35/35 (100%) women. Among the 11 HG lesions, 8 had a score of 4 and 2 had a score of 5. One case was uninterpretable due to a low signal-to-noise ratio. Among the 25 LG lesions, 15 had a score of 3, 6 had a score of 4 or 5, 2 had a score of 1, and 2 cases were uninterpretable.

CONCLUSIONS

HG lesions generated spectra distinct from normal tissue in 8/10 (80%) evaluable cases, but LG lesions generated spectra indistinguishable from that of normal metaplastic tissue. Further modifications to this technique are needed before an objective, reproducible, and discriminatory scoring system can be developed. ▪.

Erythrocyte Protoporphyrin Fluorescence as a Biomarker to Monitor the Anticancer Effect of Semecarpus Anacardium in DMBA Induced Mammary Carcinoma Rat Model

Endogenous fluorescence has been proposed as a means of aiding the diagnosis of various malignancies. It has been suggested that erythrocytes may be the carriers of fluorophors that accumulate in cancer tissue and may be useful in the diagnosis and treatment of malignancies. Hence, the present study was designed to explore the spectrofluorimetric analysis of blood components as a marker for the analysis of mammary carcinoma treatment and also to bring about the protective effect of the drug Semecarpus anacardium on oxidative stress mediated damage of erythrocytes. Fluorescence spectra of the blood components were studied and also the level of lipid per oxides and antioxidant enzymes status in erythrocytes were determined in DMBA induced mammary carcinoma rats treated with Semecarpus anacardium Linn nut milk extract. Fluorescence emission spectroscopy of blood components are altered under cancer conditions and the drug effectively ameliorated these alterations in mammary carcinoma induced rats. The drug also effectively reduced the oxidative stress induced erythrocyte damage thereby restoring the erythrocytes antioxidant status. These results suggest that erythrocytes may be the carriers of fluorophors that accumulate in cancer tissue and hence acts as new biomarkers for the diagnosis and treatment.

Native fluorescence spectroscopic characterization of DMBA induced carcinogenesis in mice skin for the early detection of tissue transformation

The objective of the study is to characterize the endogenous porphyrin fluorescence in a dimethylbenz(a)anthracene (DMBA) induced mouse skin tumor model using native fluorescence emission and excitation spectroscopy.

Application of HPLC combined with laser induced fluorescence for protein profile analysis of tissue homogenates in cervical cancer

A highly objective method, High Performance Liquid Chromatography with Laser Induced Fluorescence (HPLC-LIF) technique was used to study the protein profiles of normal and cervical cancer tissue homogenates. A total of 44 samples including normal cervical biopsy samples from the hysterectomy patients and the patients suffering from different stages of the cervical cancer were recorded by HPLC-LIF and analysed by Principle Component Analysis (PCA) to get statistical information on different tissue components. Discrimination of different stages of the samples was carried out by considering three parameters--scores of factor, spectral residual, and Mahalanobis Distance. Diagnostic accuracy of the method was evaluated using Receiver Operating Characteristic (ROC) analysis, and Youden's index (J) plots. The PCA results showed high sensitivity and specificity (~100) for cervical cancer diagnosis. ROC and Youden's index curves for both normal and malignant standard sets show good diagnostic accuracy with high AUC values. The statistical analysis has shown that the differences in protein profiles can be used to diagnose biochemical changes in the tissue, and thus can be readily applied for the detection of cervical cancer, even in situations where a histopathology examination is not easy because of nonavailability of experienced pathologists.

Fluorescence spectroscopy of an in vitro model of human cervical neoplasia identifies graded spectral shape changes with neoplastic phenotype and a differential effect of acetic acid

BACKGROUND

The clinical utility of spectroscopic methods for the diagnosis of cervical cancer is limited by significant inter-patient variation in the spectroscopic properties of the cervix. Improved understanding of the contributions of the components of cervical tissue to the observed spectra would therefore be helpful in the development of spectroscopic approaches to the study of cervical disease in vivo.

METHODS

In this study, we used organotypic epithelial raft culture as an in vitro model system to analyse the fluorescence properties of the surface squamous epithelium specifically. The spectrum of cervical dysplasia was modelled by producing rafts lined by primary human keratinocytes (PHKs) and the HaCaT, SiHa and CaSki human keratinocyte cell lines and fluorescence emission spectra were recorded at a wide range of excitation wavelengths.

RESULTS

Statistically significant differences in spectral shape were identified between the different rafts at excitation wavelengths between 250nm and 310nm. A graded, differential effect of acetic acid on fluorescence intensity was also observed, consistent with the visible effects of acetic acid on clinical examination at colposcopy.

CONCLUSION

These data suggest that the development of neoplastic changes in the squamous epithelium of the cervix are associated with alterations in its fluorescence properties and that the application of acetic acid has a demonstrable effect on these properties. Identification of these alterations may aid the discrimination of cervical lesions in vivo.

Synchronous fluorescence spectroscopy for the detection and characterization of cervical cancers in vitro

The objective of this study was to assess the diagnostic potential of synchronous fluorescence (SF) spectroscopy (SFS) technique for the detection and characterization of normal and different malignancy stages of moderately differentiated squamous cell carcinoma (MDSCC), poorly differentiated squamous cell carcinoma (PDSCC) cervical tissues. SF spectra were measured from 45 biopsies from 30 patients in vitro. Characteristic, highly resolved peaks and significant spectral differences between normal and MDSCC, PDSCC cervical tissues were obtained. Nine potential ratios were calculated and used as input variables for a discriminant analysis across different groups. The potentiality of the SFS technique was estimated by two discriminant analyses. Discriminant analysis I performed across normal and abnormal (including MDSCC and PDSCC) cervical tissues classified as 100% both original and the cross-validated grouped cases. In discriminant analysis II performed across the three groups, normal, MDSCC and PDSCC, 100% of both original and the cross-validated grouped cases were correctly classified. Using the SFS technique, one can obtain all the key biochemical markers such as tryptophan, collagen, hemoglobin, reduced form of nicotinamide adenine dinucleotide and flavin adenine dinucleotide in a single scan and hence they can be targeted as tumor markers in the detection of normal from abnormal cervical tissues.

Comparison of Human Papilloma Virus Testing and Spectroscopy Combined With Cervical Cytology for the Detection of High-grade Cervical Neoplasia

OBJECTIVE

This study compared the performance of cervical cytology plus human papilloma virus testing (Pap + HPV) or cervical spectroscopy (Pap + CS) for identifying high-grade cervical neoplasia in a high-risk population of women referred for colposcopy.

MATERIALS AND METHODS

Each of 113 subjects underwent spectroscopy, thin-layer cytology, HPV testing, colposcopy, biopsy when indicated, and/or endocervical curettage. Evaluable data for analysis were collected for 102 of the subjects. Sensitivity and specificity were calculated for both strategies.

RESULTS

Pap + HPV and Pap + CS achieved equivalent sensitivities (95%) for high-grade lesions, with both detecting 17 of 18 histology confirmed cervical intraepithelial neoplasia (CIN) 2+ lesions. Pap + HPV had a specificity of only 27.4% compared with 65.5% for Pap + CS (p < .0001).

CONCLUSIONS

Spectroscopic interrogation of the cervix is equally sensitive and 2-fold more specific than HPV testing when combined with cervical cytology for identifying high-grade cervical neoplasia.

Fluorescence spectroscopy of anin vitro model of human cervical precancer identifies neoplastic phenotype

The clinical diagnosis of cervical neoplasia by spectroscopic methods is potentially a reliable, fast and cost-effective alternative to the conventional smear test. However, it is currently limited by significant inter-patient variation in the spectroscopic properties of the cervix. Characterisation of suitable in vitro models of the spectroscopic changes that take place during neoplastic progression may prove to be a significant step towards the successful development of reliable in vivo systems. In this study, we used organotypic epithelial raft culture as an in vitro model of cervical tissue to analyse changes in the fluorescence properties of surface squamous epithelium that are associated with the development of neoplastic disease. Collagen plugs lined by primary human keratinocytes (PHKs) were used to model the normal cervical epithelium, and plugs lined by cells of the SiHa line were used as a model of neoplastic cervical tissue. Fluorescence emission spectra of these rafts were recorded at excitation wavelengths in the 250-330 nm range, complementing previous work published at longer wavelengths. Normalised, truncated emission spectra were analysed using multivariate principal component analysis. We successfully distinguished between in vitro models of normal and neoplastic cervical tissue and demonstrated a differential effect of acetic acid, which enhances the discrimination of normal from neoplastic tissue. Identification of these differences between in vitro organotypic epithelial rafts may ultimately aid the discrimination of cervical lesions in vivo.

Spectroscopic Imaging as a Triage Test for Cervical Disease

OBJECTIVE

The objective of the study was to evaluate the potential safety and effectiveness of tissue spectroscopy for the diagnosis of cervical cancer in a prospective multicenter study of women scheduled for colposcopy on the basis of an abnormal Pap test or other risk factor.

MATERIALS AND METHODS

Five hundred seventy-two women underwent spectroscopy of the cervix during their colposcopy visit. Spectroscopy measurements taken over a scan period of 4 minutes and 30 seconds were integrated by a cross-validated pattern recognition model and compared with biopsy results to yield sensitivity and specificity of cervical spectroscopy.

RESULTS

The median age of subjects enrolled in the study was 27.7 years. The sensitivity of cervical spectroscopy was 95.1% with a corresponding 55.2% specificity for benign lesions. Several potential confounding factors (eg, mucous, blood, patient motion, ambient light) were examined to determine their potential impact on the accuracy of the test. Ambient light seemed to have the greatest effect, but no single factor contributed significantly to the results. The subjects did not experience any adverse events from undergoing the test.

CONCLUSIONS

Spectroscopy of the cervix has the potential to accurately detect cervical moderate and high-grade dysplasia while also reducing the false-positive rate for benign cervices. The test is relatively simple to implement and was well accepted by subjects enrolled in the study.

In vivo nonlinear spectral imaging in mouse skin

We report on two-photon autofluorescence and second harmonic spectral imaging of live mouse tissues. The use of a high sensitivity detector and ultraviolet optics allowed us to record razor-sharp deep-tissue spectral images of weak autofluorescence and short-wavelength second harmonic generation by mouse skin. Real-color image representation combined with depth-resolved spectral analysis enabled us to identify tissue structures. The results show that linking nonlinear deep-tissue imaging microscopy with autofluorescence spectroscopy has the potential to provide important information for the diagnosis of skin tissues.

Novel optical detection system for in vivo identification and localization of cervical intraepithelial neoplasia

A noncontact optical detection system is developed for the in vivo identification and localization of high-grade cervical intraepithelial neoplasia (CIN 2,3). Diagnostic scans of the entire human cervix are performed following acetic acid application employing three integrated optical measurements: laser-induced fluorescence spectroscopy, white light diffuse reflectance spectroscopy, and video imaging. Full cervical scans comprising 499 interrogation locations at 1-mm spatial resolution are completed in 12 s. Diffuse reflectance and fluorescence spectra with signal-to-noise ratios of better than 100-to-1 are collected between 360 and 720 nm in increments of 1 nm, with an inherent spectral resolution of 8 nm. Glare reduction and optical vignetting are handled with a novel illumination scheme and subsequent spectral arbitration algorithms. The system is designed and found to be well below acceptable safe optical exposure levels. Typical reproducibility across multiple systems is approximately 5%, providing reliable and accurate detection of in vivo cervical neoplasia in normal clinical use.

Synchronous fluorescence spectroscopic characterization of DMBA-TPA-induced squamous cell carcinoma in mice

While initially confined to the epidermis, squamous cell carcinoma can eventually penetrate into the underlying tissue if not diagnosed early and treated. The noninvasive early detection of the carcinoma is important to achieve a complete treatment of the disease. Of the various non-invasive optical techniques, the synchronous fluorescence (SF) technique is considered to provide a simplified spectral profile with more sharp spectral signatures of the endogenous fluorophores in complex systems. The potential use of the SF technique in the characterization of the sequential tissue transformation in 7,12-dimethylbenz(a)anthracene-12-O-tetradecanoylphorbol-13-acetate (DMBA-TPA)-induced mouse skin tumor model in conjunction with simple statistical analysis is explored. The SF spectra show distinct differences during the earlier weeks of the tumor-induction period. Intensity ratio variables are calculated and used in three discriminant analyses. All the discriminant analyses show better classification results with accuracy greater than 80%. From the observed differences in the spectral characteristics and the ratio variables that resulted in better classification between groups, it is concluded that tryptophan, collagen, and NADH are the key fluorophores that undergo changes during tissue transformation process and hence they can be targeted as tumor markers to diagnose normal from abnormal tissues using the SF technique.

Detection of morphological changes of the ovine cervix in response to sex steroids using a fluorescence confocal endomicroscope

OBJECTIVE

This study examined morphological changes of the ovine cervix in response to sex steroids using confocal microscopy.

STUDY DESIGN

Experimental animals were ovariectomized, and the hormonal status of 4 groups of ewes (n = 5) was manipulated using sex steroids (no replacement, estradiol, progesterone, estradiol, and progesterone). The results were correlated with control ewes (n = 7) in naturally occurring reproductive states (estrus and midluteal).

RESULTS

Plasma progesterone concentrations of experimental animals were comparable with those observed during normal reproduction. Confocal microscopy enabled subcellular resolution of the cervical epithelium and the detection of morphological changes associated with alterations in progesterone and estradiol in both artificially manipulated and naturally cycling ewes. Differences in nuclear size, distribution, and density could be differentiated in confocal images and histologic sections of ectocervix from animals in estrus and in the presence of exogenous estradiol.

CONCLUSION

Confocal microscopy has potential diagnostic value for the detection of cellular and subcellular changes of the cervical epithelium.

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 characterization for the early diagnosis of neoplastic changes in DMBA/TPA-induced mouse skin carcinogenesis

BACKGROUND AND OBJECTIVE

Squamous cell carcinoma (SCC), the second most common skin cancer, usually remains confined to the epidermis for some time but eventually penetrates the underlying tissues, if left untreated. The non-invasive early detection of the SCC is important for appropriate therapeutic strategies. In this study, we aim to characterize the tissue transformation in DMBA/TPA induced mouse skin tumor model using autofluorescence excitation emission matrix (EEM) in conjunction with a multivariate statistical method for early detection of the neoplastic changes.

STUDY DESIGN/MATERIALS AND METHODS

The fluorescence EEM from experimental group (n = 40; DMBA/TPA application), control group (n = 6; acetone application), and the blank group (n = 6; no application of DMBA/TPA or acetone) were measured every week using a spectrofluorometer coupled with a fiber optic bundle. The EEM was recorded at excitation wavelengths from 280 to 460 nm at 10 nm intervals and the fluorescence emission was scanned from 300 to 750 nm. The fluorescence emission characteristics corresponding to different fluorophores were extracted from the EEM and the spectral data were used in a multiple/linear discriminant statistical algorithm.

RESULTS

The changes in the fluorescence emission intensity were observed as early as the 1st week of tumor initiation by DMBA. Morphological changes as well as differences in the gross appearance of the skin surface were observed during the entire tumor initiation and promotion period of 15 weeks. The statistical analysis was performed for each excitation wavelength in the EEM and better classification accuracy was obtained for 280 and 410 nm excitations, corresponding to tryptophan and endogenous porphyrins, respectively. The statistical analysis of the combination wavelengths resulted in 11.6% increase in the overall classification accuracy when compared to the highest classification accuracy obtained with single wavelength analysis.

CONCLUSION

The intensity ratio mapping using the combination of emission intensities of key fluorophores such as tryptophan, collagen, NADH, and endogenous porphyrins from the measured EEM in conjunction with a simple multivariate statistical analysis can be used as a potential tool for the discrimination of early neoplastic changes with improved classification accuracy. Tryptophan and endogenous porphyrins may be used as biomarkers for the discrimination of early neoplastic changes when single wavelength excitations are used.

A pilot study for a screening trial of cervical fluorescence spectroscopy

Fluorescence spectroscopy is a promising technology for detection of epithelial precancers and cancers. In preparation for a multicenter phase II screening trial, a pilot trial was conducted to test data collection and patient examination procedures, use data forms, time procedures, and identify problems with preliminary data analysis. Women 18 years of age and older underwent a questionnaire, a complete history, and a physical examination, including a pan-colposcopy of the lower genital tract. A fiber-optic probe measured fluorescence excitation-emission matrices at 1-3 cervical sites for 58 women. The data collection procedures, data forms, and procedure times worked well, although collection times for all the clinical data take an average of 28 min. The clinical team followed procedures well, and the data could be retrieved from the database at all sites. The multivariate analysis algorithm correctly identified squamous normal tissue 99% of the time and columnar normal tissue only 7%. The assessment of ploidy from monolayer samples was not accurate in this small sample. The study was successful as a pilot trial. We learned who participated, who withdrew, how often abnormalities were present, and that algorithms that have worked extremely well in previous studies do not work as well when a few study parameters are changed. The current algorithm for diagnosis identified squamous normal tissue very accurately and did less well for columnar normal tissue. Inflammation may be an explanation for this phenomenon. Fluorescence spectroscopy is a promising technology for the detection of epithelial precancers and cancers. The screening trial of fluorescence and reflectance spectroscopy was successful.

Optical detection of high-grade cervical intraepithelial neoplasia in vivo: results of a 604-patient study

OBJECTIVE

The purpose of this study was to assess the in vivo optical detection of high-grade cervical intraepithelial neoplasia (2/3+) on the whole cervix with a noncontact, spectroscopic device.

STUDY DESIGN

Cervical scanning devices collected intrinsic fluorescence and broadband white light spectra and video images from 604 women during routine colposcopy examinations at 6 clinical centers. A statistically significant dataset was developed of intrinsic fluorescence and white light-induced cervical tissue spectra that was correlated to expert histopathologic determination. On the basis of a retrospective analysis of the acquired data, a classification algorithm was developed, validated, and optimized.

RESULTS

Intrinsic fluorescence, backscattered white light, and video imaging each contribute complementary information to diagnostic algorithms for high-grade cervical neoplasia. More than 10000 measurements that were made on colposcopically identified tissue from >500 subjects were the basis for algorithm training and testing. Algorithm performance demonstrated a sensitivity of approximately 90%. This performance was confirmed by various training methods. With the use of a multivariate classification algorithm, optical detection is predicted to detect 33% more high-grade cervical intraepithelial neoplasia (2/3+) than colposcopy alone.

CONCLUSION

Full cervix optical interrogation for the detection of high-grade cervical intraepithelial neoplasia is feasible and appears capable of detecting more high-grade cervical intraepithelial neoplasia than colposcopy alone. With the use of this classification algorithm, a multisite, randomized controlled trial is underway that compares the combination of optical detection and colposcopy versus colposcopy alone.

Effect of probe pressure on cervical fluorescence spectroscopy measurements

Fluorescence spectroscopy is a promising technology for detection of epithelial precancers and cancers. While age and menopausal status influence measurements in the cervix, other variables do not significantly affect the diagnosis. In this study we examine probe pressure as a variable. A fiber optic probe to measure fluorescence spectra at different calibrated levels of pressure was designed and tested. A pilot study was conducted measuring fluorescence excitation emission matrices in 20 patients at light, medium, and firm pressure. Spectroscopic data were pre-processed and analyzed to compare mean peak intensities as a function of pressure. Further statistical analyses tested for differences in intensities at each excitation/emission wavelength pair. Four providers made measurements from 41 sites; 33 yielded good quality spectroscopic data (22 squamous normal, 7 squamous abnormal, 3 columnar normal, 1 transformation zone) from 17 of 20 patients. At all pressure levels, abnormal tissue showed less fluorescence intensity than normal tissue, and post-menopausal patients showed higher fluorescence intensity than premenopausal patients, consistent with previous analyses. A permutation analysis suggests that pressure does not significantly affect fluorescence intensity or lineshape. While other studies are needed to confirm these findings, this study suggests that fluorescence spectroscopy is a robust technology likely not influenced by fiber optic probe pressure.

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.

Optical imaging of the cervix

Recent advances in fiber optics, sources and detectors, imaging, and computer-controlled instrumentation have stimulated a period of unprecedented growth in the development of photonics technologies for a wide variety of diagnostic and therapeutic clinical applications. These include the application of quantitative optical spectroscopy and imaging for the detection of precancerous lesions in the uterine cervix, a topic of interest at the Second International Conference on Cervical Cancer, which was held April 11-14, 2002. Investigators have applied the Littenberg method of emerging technology assessment to new optical methods used to detect cervical neoplasia. Currently, such technologies as fluorescence spectroscopy (the combination of fluorescence and diffuse reflectance spectroscopy), tri-modal spectroscopy, and light-scattering spectroscopy that probe the spectral characteristics of tissue are being investigated. Optical technologies that create images of subcellular structure without biopsy subsequent to pathology that currently are under investigation include in vivo confocal imaging and optical coherence tomography. Numerous small studies have demonstrated the potential of these optical technologies. What remains to be elucidated are the fundamental biophysical origins of variations in remitted optical signals between normal and dysplastic tissue. Large multicenter randomized controlled trials are needed to confirm the detection and imaging capabilities of optical technology. Furthermore, the development of contrast agents that could boost detection with these technologies is needed, and basic biologic characterization of signals should be pursued. Applying the Littenberg assessment will help ensure that superior, not simply alternative, technologies are implemented.

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.

Native fluorescence spectroscopy of blood plasma in the characterization of oral malignancy

Native fluorescence characteristics of blood plasma were studied in the visible spectral region, at two different excitation wavelengths, 405 and 420 nm, to discriminate patients with different stages of oral malignancy from healthy subjects. The fluorescence spectra of blood plasma of oral malignant subjects exhibit characteristic spectral differences with respect to normal subjects. Different ratios were calculated using the fluorescence intensity values at those emission wavelengths that give characteristic spectral features of each group of experimental subjects studied. These fluorescence intensity ratios were used as input variables for a multiple linear discriminant analysis across different groups. Leave-one out cross-validation was used to check the reliability of each discriminant analysis performed. The discriminant analysis performed across normal and oral cancerous subjects classified 94.7% of the original grouped cases and 93.7% of the cross-validated grouped cases. A classification algorithm was developed on the basis of the score of the discriminant functions (discriminant score) resulted in the analyses. The diagnostic potentiality of the present technique was also estimated in the discrimination of malignant subjects from normal and nonmalignant diseased subjects such as liver diseases. In the discriminant analysis performed across the three groups, normal, oral malignancy (including early and advanced stages) and liver diseases, 99% of the original grouped cases and 95.9% of the cross-validated grouped cases were correctly classified. Similar analysis performed across normal, early stage of oral malignancy, advanced oral malignancy and liver diseases correctly classified 94.9% of the original grouped cases and 91.8% of the cross-validated grouped cases.

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.

Fiber optic probes for biomedical optical spectroscopy

Fiber optic probes are a key element for biomedical spectroscopic sensing. We review the use of fiber optic probes for optical spectroscopy, focusing on applications in turbid media, such as tissue. The design of probes for reflectance, polarized reflectance, fluorescence, and Raman spectroscopy is illustrated. We cover universal design principles as well as technologies for beam deflecting and reshaping.

Optimal excitation wavelengths for discrimination of cervical neoplasia

Fluorescence spectroscopy has shown promise for the in vivo, real-time detection of cervical neoplasia. However, selection of excitation wavelength has in the past been based on in vitro studies and the availability of light sources. The goal of this study was to determine optimal excitation wavelengths for in vivo detection of cervical neoplasia. Fluorescence excitation-emission matrices (EEMs) were measured in vivo from 351 sites in 146 patients. Data were analyzed in pairs of diagnostic classes to determine which combination of excitation wavelengths yields classification algorithms with the greatest sensitivity and specificity. We find that 330-340-, 350-380-, and 400-450-nm excitation yield the best performance. The sensitivity and specificity for discrimination of squamous normal tissue and high-grade squamous intraepithelial lesion (HGSIL) were 71% and 77% on cross validation using three excitation wavelengths. These results are comparable with those found in earlier in vivo studies; however, in this study we find that the proportion of samples which are HGSIL influences performance. Furthermore stratification of samples within low-grade squamous intraepithelial lesion and HGSIL also appears to influence diagnostic performance. Future diagnostic studies should be carried out at these excitation wavelengths in larger groups so that data can be stratified by diagnostic subcategory, age and menopausal status. Similarly, large studies should be done in screening populations.

Reflectance spectroscopy for in vivo detection of cervical precancer

Optical technologies, in particular fluorescence spectroscopy, have shown the potential to provide improved detection methods for cervical neoplasia that are sensitive and cost effective through accurate, objective, instantaneous point-of-care diagnostic tools. The specific goals of this study were to analyze reflectance spectra of normal and neoplastic cervical tissue in vivo and to evaluate the data for use in diagnostic algorithm development. Spectroscopic measurements were obtained at four distinct source-detector separations from 324 sites in 161 patients. As the source-detector separation increases, greater tissue depth is probed. The average spectra of each diagnostic class differed at all source-detector separations, with the greatest differences occurring at the smallest source-detector separations. Algorithms, based on principal-component analysis and Mahalanobis distance classification, were developed and evaluated for all combinations of source-detector separations relative to the gold standard of colposcopically directed biopsy. The diagnostic combination of squamous normal versus high-grade squamous intraepithelial lesions gave good discrimination with a sensitivity of 72% and a specificity of 81%; discrimination of columnar normal versus high-grade squamous intraepithelial lesions also was good, with sensitivity of 72% and specificity of 83%. Thus, reflectance spectroscopy appears promising for in vivo detection of cervical precancer. Strategies that combine fluorescence and reflectance spectroscopy may enhance the discrimination capabilities.

Trimodal spectroscopy for the detection and characterization of cervical precancers in vivo

OBJECTIVE

The objective of this study was to assess the potential of 3 spectroscopic techniques (intrinsic fluorescence, diffuse reflectance, and light scattering) individually and in combination (trimodal spectroscopy) for the detection of cervical squamous intraepithelial lesions.

STUDY DESIGN

The study was conducted with 44 patients who underwent colposcopy for the evaluation of an abnormal Papanicolaou smear. Fluorescence and reflectance spectra were collected from colposcopically normal and abnormal sites and analyzed to extract quantitative information about tissue biochemistry and morphologic condition. This information was compared with histopathologic classification, and diagnostic algorithms were developed and validated with the use of logistic regression and cross-validation.

RESULTS

Diagnostically significant differences exist in the composition of fluorescing biochemicals, the scattering properties, and the epithelial cell nuclear morphology of cervical squamous intraepithelial lesions and non-squamous intraepithelial lesions. Trimodal spectroscopy is a superior tool for the detection of cervical squamous intraepithelial lesions than any 1 of the techniques alone.

CONCLUSION

Trimodal spectroscopy has the potential to improve the in vivo detection of precancerous cervical changes.

Understanding the contributions of NADH and collagen to cervical tissue fluorescence spectra: modeling, measurements, and implications

OBJECTIVE

At 380 nm excitation, cervical tissue fluorescence spectra demonstrate characteristic changes with both patient age and the presence of dysplasia. A Monte Carlo model was developed in order to quantitatively examine how intrinsic NADH and collagen fluorescence, in combination with tissue scattering and absorption properties, yield measured tissue spectra.

METHODS

Excitation-emission matrices were measured for live cervical cells and collagen gel phantoms. Fluorescence microscopy of fresh tissue sections was performed to obtain the location and density of fluorophores as a function of patient age and the presence of dysplasia. A Monte Carlo model was developed which incorporated measurements of fluorophore line shapes and spatial distributions.

RESULTS

Modeled spectra were consistent with clinical measurements and indicate that an increase in NADH fluorescence and decrease in collagen fluorescence create clinically observed differences between normal and dysplastic tissue spectra. Model predictions were most sensitive to patient age and epithelial thickness.

CONCLUSIONS

Monte Carlo techniques provide an important means to investigate the combined contributions of multiple fluorophores to measured emission spectra. The approach will prove increasingly valuable as a more sophisticated understanding of in vivo optical properties is developed.

Cervical fluorescence of normal women

BACKGROUND AND OBJECTIVE

Cervical tissue fluorescence spectra have previously been measured in vivo in women with a recent abnormal Papanicolaou smear. Diagnostic algorithms have been developed to diagnose squamous intraepithelial lesions (SILs) based on these fluorescence emission spectra. However, algorithms have not been tested in women with no history of cervical neoplasia.

STUDY DESIGN/MATERIALS AND METHODS

Cervical fluorescence was measured from 54 women with no history of cervical dysplasia, and the spectra were compared to those from colposcopically normal sites in women with suspected dysplasia. Representative spectra from each group were compared and a two-sided, unpaired Student's t-test was performed to compare mean principal component scores used in previously published diagnostic algorithms. The ability of previously reported diagnostic algorithms to classify these samples as normal tissue was also assessed.

RESULTS

At the 0.05 level of significance, the mean scores of 4 of the 7 important principal components were statistically different for the two populations. However, when the data collected from volunteers in this study were preprocessed in the appropriate manner and the algorithms were applied, more normal samples were correctly classified than in the previous clinical study in which these algorithms were developed.

CONCLUSION

Previously reported algorithms can accurately classify tissue type based on spectra from women with and without a history of cervical neoplasia.

Propagation of fluorescent light

BACKGROUND AND OBJECTIVE

In general, the remitted fluorescence spectrum is affected by the scattering and absorption properties of tissue. Other important factors are boundary conditions, geometry of the tissue sample, and the quantum yield of tissue fluorophores. Each of these factors is examined through a series of Monte Carlo simulations.

STUDY DESIGN/MATERIALS AND METHODS

Monte Carlo modeling is used to simulate the propagation of excitation light and the resulting fluorescence. Remitted fluorescence is determined for semi-infinite single and multiple layer geometries and for cubic geometries representing small tissue samples. Monte Carlo results are compared to approximations obtained with a heuristic model.

RESULTS

Remitted fluorescence as a function of (1) the depth of fluorescence generation and (2) radial escape position is presented for semi-infinite single and multiple layer geometries. Fluorescence from a small tissue sample is simulated in terms of a cubic geometry, and losses from the sides and bottom are presented as a function of cube dimensions in terms of optical depth of the excitation wavelength. Monte Carlo results for a homogeneous semi-infinite layer are compared to a simple, fast heuristic model.

CONCLUSION

Both Monte Carlo simulations and the heuristic model clearly detail the volume of tissue interrogated by fluorescence. Since approximately 35-40% of the remitted fluorescence is due to photons originally directed away from the surface, distal layers affect the remitted fluorescence. Fluorescence spectra from small biopsy samples may not produce the correct line shape owing to wavelength dependent losses.

Multispectral imaging autofluorescence microscopy for the analysis of lymph-node tissues

Although histochemical and immunohistochemical methods are the standard procedures in diagnosis of lymphoproliferative disorders, useful improvements in evidencing histopathologic manifestations can be obtained with the introduction of tissue autofluorescence analyses. We used microspectrofluorometry and a Multispectral Imaging Autofluorescence Microscopy (MIAM) technique to analyze lymph-node biopsies from patients with lymphoadenopathy of different origins. Images of tissue autofluorescence were obtained by excitation at 365 nm of lymph-node sections and sequential detection with interference filters (50 nm bandwidth) peaked at 450, 550 and 658 nm. Monochrome images were combined together in a single red-green-blue color image. Most of the fluorescence was observed within the blue spectral band because of large contributions from extracellular collagen and elastin fibers as well as from reduced form of intracellular nicotinamide adenine dinucleotide (phosphate). Autofluorescence imaging shows morphological differences between neoplastic and non-neoplastic tissues. The reactive hyperplasia samples show the typical lymph-node organization with weak fluorescent follicles separated by high fluorescent connective trabeculae. In the neoplastic lymph nodes the loss of follicle organization is observed. Consequently, MIAM permits to discriminate between non-neoplastic and neoplastic tissues on the basis of their autofluorescence pattern. Multispectral imaging of tissue autofluorescence may present some advantages with respect to standard histochemical microscopy since it (1) does not require any chemical manipulation of samples; (2) gives real-time results performing the analysis immediately upon specimen resection; and (3) supplies a representation of the biological structure organization linked to endogenous fluorophores.

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.

Quantitative near-infrared spectroscopy of cervical dysplasia in vivo

The aims of this study were: (i) to quantify near-infrared optical properties of normal cervical tissues and high-grade squamous intra-epithelial lesions (H-SIL); (ii) to assess the feasibility of differentiating normal cervical tissues from H-SIL on the basis of these properties; and (iii) to determine how cervical tissue optical properties change following photodynamic therapy (PDT) of H-SIL in vivo. Using the frequency domain photon migration technique, non-invasive measurements of normal and dysplastic ecto-cervical tissue optical properties, i.e. absorption (mu(a)) and effective scattering coefficients, and physiological parameters, i.e. tissue water and haemoglobin concentration, percentage oxygen saturation (%SO(2)), were performed on 10 patients scheduled for PDT of histologically-proven H-SIL. Cervix absorption and effective scattering parameters were up to 15% lower in H-SIL sites compared with normal cervical tissue for all wavelengths studied (674, 811, 849, 956 nm). Following PDT, all mu(a) values increased significantly, due to elevated tissue blood and water content associated with PDT-induced hyperaemia and oedema. Tissue total haemoglobin concentration ([TotHb]) and arterio-venous oxygen saturation measured in H-SIL sites were lower than normal sites ([TotHb]: 88.6 +/- 35.8 micromol/l versus 124.7 +/- 22.6 micromol/l; %SO(2): 76.5 +/- 14.7% versus 84.9 +/- 3.4%).

Performance estimation of diagnostic tests for cervical precancer based on fluorescence spectroscopy: effects of tissue type, sample size, population, and signal-to-noise ratio

Fluorescence spectroscopy may provide a cost-effective tool to improve precancer detection. We describe a method to estimate the diagnostic performance of classifiers based on optical spectra, and to explore the sensitivity of these estimations to factors affecting spectrometer cost. Fluorescence spectra were obtained at three excitation wavelengths in 92 patients with an abnormal Papanicolaou smear and 51 patients with no history of an abnormal smear. Bayesian classification rules were developed and evaluated at multiple misclassification costs. We explored the sensitivity of classifier performance to variations in tissue type, sample size, tested population, signal to noise ratio (SNR), and number of excitation and emission wavelengths. Sensitivity and specificity could be evaluated within +/- 7%. Minimal decrease in diagnostic performance is observed as SNR is reduced to 15, the number of excitation-emission wavelength combinations is reduced to 15 or the number of excitation wavelengths is reduced to one. Diagnostic performance is compromised when ultraviolet excitation is not included. Significant spectrometer cost reduction is possible without compromising diagnostic ability. Decision-analytic methods can be used to rate designs based on incremental cost-effectiveness.

Autofluorescence in normal and malignant human oral tissues and in DMBA-induced hamster buccal pouch carcinogenesis

Light-induced fluorescence spectroscopy was conducted on human oral malignant and normal tissues. Under 330-nm excitation wavelength, significant differences in fluorescence intensity were observed around 380- and 460-nm emission. Furthermore, 7,12-dimethylbenz[a]anthracene (DMBA)-induced carcinogenesis in hamster buccal pouch was investigated to elucidate whether similar alterations of fluorescence spectroscopy occurred during the development of squamous cell carcinoma. Similar to the spectral profiles of human oral malignant and normal tissues, the most intense fluorescence peaks in the pouches occurred at 380 nm and 460 nm emission under 330 nm excitation wavelength. At 380 nm emission, the fluorescence intensity of normal pouch mucosa was stronger than those of DMBA-treated abnormal tissues at different stages of carcinogenesis. However, at 460 nm emission, the fluorescence intensity of DMBA-treated tissues was not only stronger than that of normal pouch mucosa but also shifted to 470 nm. These results suggest that under 330 nm excitation wavelength fluorescence spectroscopy may be useful for the detection of oral malignant lesions.