Biomedical subjects

R Richards-Kortum

Publications and source records attributed to R Richards-Kortum.

50 records · Page 3Linked to original sources

PubMed1994

In vivo diagnosis of cervical intraepithelial neoplasia using 337-nm-excited laser-induced fluorescence.

Laser-induced fluorescence at 337-nm excitation was used in vivo to differentiate neoplastic [cervical intraepithelial neoplasia (CIN)], nonneoplastic abnormal (inflammation and human papilloma viral infection), and normal cervical tissues. A colposcope (low-magnification microscope used to view the cervix with reflected light) was used to identify 66 normal and 49 abnormal (5 inflammation, 21 human papilloma virus infection, and 23 CIN) sites on the cervix in 28 patients. These sites were then interrogated spectroscopically. A two-stage algorithm was developed to diagnose CIN. The first stage differentiated histologically abnormal tissues from colposcopically normal tissues with a sensitivity, specificity, and positive predictive value of 92%, 90%, and 88%, respectively. The second stage differentiated preneoplastic and neoplastic tissues from nonneoplastic abnormal tissues with a sensitivity, specificity, and positive predictive value of 87%, 73%, and 74%, respectively. Spectroscopic differences were consistent with a decrease in the absolute contribution of collagen fluorescence, an increase in the absolute contribution of oxyhemoglobin attenuation, and an increase in the relative contribution of reduced nicotinamide dinucleotide phosphate [NAD(P)H] fluorescence as tissue progresses from normal to abnormal in the same patient. These results suggest that in vivo fluorescence spectroscopy of the cervix can be used to diagnose CIN at colposcopy.

Cervix Uteri↗

PubMed1994

Fluorescence spectroscopy: a diagnostic tool for cervical intraepithelial neoplasia (CIN).

A spectroscopic system incorporating a pulsed nitrogen laser, an optical fiber probe, and an optical multichannel analyzer was utilized to record fluorescence spectra of the intact cervix at colposcopy. Spectra were obtained from 66 colposcopically normal areas and 49 histologically abnormal areas (5 pathologic inflammation, 21 HPV infection, 9 CIN I, 10 CIN II, and 4 CIN III) in 28 patients. The resulting spectra could be used to differentiate histologically abnormal tissues from colposcopically normal tissues with a sensitivity, specificity, and positive predictive value of 92, 90, and 88%. Furthermore, CIN could be differentiated from nonneoplastic abnormal tissues with a sensitivity, specificity, and positive predictive value of 87, 73, and 74%. These results suggest that laser-induced fluorescence can be used in the recognition and differential diagnosis of CIN at colposcopy.

Algorithms↗

PubMed1994

In vivo fluorescence spectroscopy: potential for non-invasive, automated diagnosis of cervical intraepithelial neoplasia and use as a surrogate endpoint biomarker.

A quantitative measure of intraepithelial neoplasia which can be made in vivo without the need for tissue removal would be of clinical significance. Our group is working to develop such a technique based on fluorescence spectroscopy. This paper reviews the use of fluorescence spectroscopy for tissue diagnosis, describes our work to apply this technique to the diagnosis of cervical intraepithelial neoplasia (CIN), and discusses the potential utility of fluorescence spectroscopy as a surrogate endpoint biomarker (SEB). The development and performance of a spectroscopic diagnostic algorithm for CIN is described in detail. Fluorescence excitation-emission matrices (EEMs) were obtained in vitro for 18 cervical biopsies from 10 patients. At all excitation emission maxima, but especially at 330 nm excitation, 385 nm emission, the average normalized fluorescence intensity of histologically normal tissue is greater than that of histologically abnormal tissue. A diagnostic algorithm based on the relative intensity at 330 nm excitation, 385 nm emission can differentiate histologically normal and abnormal biopsies with a higher sensitivity, but a lower positive predictive value and specificity than colposcopy. However, paired comparison of histologically normal and abnormal biopsies from the same patient results in a sensitivity of 75%, positive predictive value of 86%, and specificity of 88% for spectroscopic identification of histological abnormality--similar to that of colposcopy. Based on these results, in vivo studies of cervical tissue fluorescence were conducted. A spectroscopic system incorporating a pulsed nitrogen laser, an optical fiber probe, and an optical multi-channel analyzer was used to record fluorescence spectra of the intact cervix at colposcopy.(ABSTRACT TRUNCATED AT 250 WORDS)

Automation↗

PubMed1993

A characterization of the fluorescent properties of circulating human eosinophils.

This paper presents a characterization of the fluorescence properties of human eosinophils isolated from peripheral blood of normal donors over a wide range of excitation and emission wavelengths. Circulating eosinophils possess three fluorescence excitation emission maxima: one at 280 nm excitation, 330 nm emission, attributable to tryptophan fluorescence, and currently unassigned peaks at 360 nm excitation, 440 nm emission and 380 nm excitation, 415 nm emission. Fluorescence microscopy studies show that the fluorescence of eosinophils may be site dependent; specifically, when observed at 365 nm excitation, circulating eosinophil fluorescence appears blue-violet, while the fluorescence of tissue-dwelling eosinophils appears amber-gold. These results should be considered in developing an optical biopsy technique to identify eosinophils in human tissue.

Cell Separation↗

PubMed1993

Monte Carlo fluorescence verification of experimental results for the combined ultrasonic and spectroscopic imaging of coronary artery disease.

A system is being tested that combines fluorescence spectroscopy and intravascular ultrasound to image both chemical composition and structure of arterial tissue in vitro. In this system, distances obtained from A-mode ultrasound will be used to compensate for decreases in fluorescence intensity due to the detector-sample separation distance r. For concentrated rhodamine, a fluorescent dye, compensation has been experimentally achieved assuming fluorescence is emitted isotropically and decreases as 1/r2. For dilute rhodamine and human arterial tissue, however, compensation must be achieved with different models, since light penetration into the sample is more significant. Using optical properties consistent with those of the aforementioned samples, experimental results are successfully simulated with a Monte Carlo model for tissue fluorescence. Angular profiles are presented that demonstrate the quantitative difference between the fluorescence of these mediums. The profiles support the hypothesis that, although fluorescence is emitted isotropically within tissue, the angular distribution of light exiting the tissue is not isotropic due to reabsorption events.

Aorta↗

PubMed1991

476 nm excited laser-induced fluorescence spectroscopy of human coronary arteries: applications in cardiology.

We have shown that normal coronary arteries and noncalcified and calcified atherosclerotic plaque can be differentiated on the basis of the 476 nm excited fluorescence spectra, providing the basis of a spectroscopic guidance system for coronary artery laser angiosurgery. This discrimination is based on extraction of parameters from tissue fluorescence spectra, which are proportional to the tissue concentrations of structural proteins (collagen and elastin) and ceroid via a model of tissue fluorescence. We use these parameters to calculate the likelihood that an area of interest in a coronary artery is normal, noncalcified, or calcified plaque. This method of diagnosing atherosclerosis provides information about the histochemical composition of atherosclerotic lesions and is thus fundamentally different from the diagnostic methods currently used. It may ultimately have bearing on a number of pertinent clinical problems. We have discussed applications to studying initiating factors in formation and progression of plaque, healing after interventional treatments, and the likelihood of restenosis after PTCA.

Algorithms↗

PubMed1991

Spectroscopic diagnosis of colonic dysplasia.

We have developed a method for defining diagnostic algorithms for pathologic conditions based on fluorescence spectroscopy. We apply this method to human colon tissue and show that fluorescence can be used to diagnose the presence or absence of colonic adenoma. This method uses fluorescence excitation-emission matrices (EEM) to identify optimal excitation regions for obtaining fluorescence emission spectra which can be used to differentiate normal and pathologic tissues. In the case of normal and adenomatous colon tissue, these were found to be: 330, 370, and 430 nm +/- 10 nm. At these excitation wavelengths, emission wavelengths for use in diagnostic algorithms are identified from average difference and ratio of the spectra from normal and pathologic tissues. In colon tissue, at 370 nm excitation, 404, 480, and 680 nm were found to be useful emission wavelengths for diagnosing the presence of adenoma in vitro. The basis of colon tissue autofluorescence was investigated using EEM of pure molecules and relevant excitation-emission maxima in the literature.

Adenoma↗

PubMed1989

Alteration of spectral characteristics of human artery wall caused by 476-nm laser irradiation.

Fluorescence spectroscopy is a promising new technique for discrimination of normal and atherosclerotic arterial tissues. It has been suggested that this technique be used as a guidance system for laser angiosurgery catheters; however, irradiation by 476-nm light can change the spectroscopic properties of arterial tissue. We present studies that establish intensity levels and exposure times at which alterations in tissue spectral properties are minimal. We also investigate the nature of spectral alterations following exposure of normal human aorta to high intensities of 476-nm laser light. Changes in laser-induced fluorescence (LIF) are characterized by two prominent features: the peak fluorescence intensity decreases permanently, and the fluorescence lineshape changes in a largely reversible way. We relate these changes to alterations in individual tissue chromophores: permanent changes in absolute fluorescence intensity are due to irreversible changes in tissue fluorophores, reversible changes in fluorescence lineshape are due alterations in tissue absorbers. A simple kinetic model is used to describe the decrease in absolute fluorescence intensity.

Aorta↗

PubMed1989

Spectral diagnosis of atherosclerosis using an optical fiber laser catheter.

This communication demonstrates that fluorescence spectra of human aorta with good S/N ratios can be collected using an optical fiber laser catheter. The performance of this catheter is compared to a non-fiber optic collection system with an equivalent delivery/collection geometry. For a given sample, fluorescence lineshapes obtained using the two systems are identical; differences in peak fluorescence intensity are related to the different collection efficiencies of the two systems. It is shown that the fluorescence lineshape of arterial tissue depends on the delivery/collection geometry of the detection system, and that this is due to the interaction of absorption and fluorescence within the artery wall. This effect is investigated systematically using a specially designed collection system. Results are analyzed qualitatively using a simple, one-dimensional model of tissue fluorescence. With this analysis, we present design requirements for a collection system in which such geometric effects are eliminated, and show that our optical fiber laser catheter satisfies these requirements.

Aortic Diseases↗

PubMed1989

Argon ion laser-excited autofluorescence in normal and atherosclerotic aorta and coronary arteries: morphologic studies.

Argon ion laser-excited autofluorescence was studied in unstained frozen sections of 47 normal and atherosclerotic human aortas and coronary arteries by means of a bright-field microscope modified for fluorescence microscopy with 476 nm argon ion laser epillumination, and compared to morphology in serial sections stained with H & E, Movat pentachrome, and oil red O. Normal artery autofluorescence correlated morphologically with the structural protein fibers elastin and collagen in the intima, media, and adventitia. Atherosclerotic plaque autofluorescence correlated morphologically with lipid or calcified deposits in the atheroma core. The autofluorescence of these deposits differed from that of elastin and collagen in distribution, intensity, and color, and increased with the severity of the plaque. We conclude that argon ion laser-excited autofluorescence in normal and atherosclerotic arteries correlates with morphology and has diagnostic potential in laser angiosurgery.

Adult↗

PubMed1989

A one-layer model of laser-induced fluorescence for diagnosis of disease in human tissue: applications to atherosclerosis.

This paper describes a general model of tissue fluorescence which can be used both to: 1) determine chemical and physical properties of the tissue, and 2) design an optimal algorithm for clinical diagnosis of tissue composition. This model is based on a picture of tissue as a single, optically thick layer, in which fluorophores and absorbing species are homogeneously distributed. As a specific example, the model is applied to the laser induced fluorescence (LIF) of normal and atherosclerotic human aorta using 476 nm excitation. Methods for determining the relevant attenuation and fluorescence lineshapes are detailed, and these lineshapes are used to apply the model to data from 148 samples. The model parameters are related to the concentrations of the major arterial chromophores: structural proteins, hemoglobin and ceroid. In addition, the model parameters are used to derive diagnostic algorithms for the presence of atherosclerosis. Utilizing a binary classification scheme, the presence or absence of pathology was determined correctly in 88 percent of cases.

Algorithms↗

PubMedDate not supplied

Gastrointestinal tissue diagnosis by laser-induced fluorescence spectroscopy at endoscopy.

An endoscope-compatible, optical fiber system has been developed which can be used to obtain laser-induced fluorescence spectra of mucosal abnormalities during endoscopy in real time. The results of our previous in vitro studies have suggested that laser-induced fluorescence tissue spectra are sufficiently unique that they can be used to accurately diagnose mucosal abnormalities in some systems. To test this hypothesis in vivo, laser-induced fluorescence spectra were obtained during colonoscopy from 31 colonic adenomas, 4 hyperplastic polyps, and 32 examples of normal mucosa in 20 patients. The resulting spectra could be used to correctly differentiate adenomas from normal colonic mucosa and hyperplastic polyps in 97% of the specimens studied with the resulting sensitivity, specificity, and positive predictive value of 100%, 97%, and 94%, respectively. These results, although preliminary in nature, suggest that laser-induced fluorescence spectra can be used in the recognition and differential diagnosis of mucosal abnormalities at endoscopy.

Adenoma↗

PubMedDate not supplied

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.

Adult↗

PubMedDate not supplied

Detection and diagnosis of oral neoplasia with an optical coherence microscope.

The use of high resolution, in vivo optical imaging may offer a clinically useful adjunct to standard histopathologic techniques. A pilot study was performed to investigate the diagnostic capabilities of optical coherence microscopy (OCM) to discriminate between normal and abnormal oral tissue. Our objective is to determine whether OCM, a technique combining the subcellular resolution of confocal microscopy with the coherence gating and heterodyne detection of optical coherence tomography, has the same ability as confocal microscopy to detect morphological changes present in precancers of the epithelium while providing superior penetration depths. We report our results using OCM to characterize the features of normal and neoplastic oral mucosa excised from 13 subjects. Specifically, we use optical coherence and confocal microscopic images obtained from human oral biopsy specimens at various depths from the mucosal surface to examine the optical properties that distinguish normal and neoplastic oral mucosa. An analysis of penetration depths achieved by the OCM and its associated confocal arm found that the OCM consistently imaged more deeply. Extraction of scattering coefficients from reflected nuclear intensity is successful in nonhyperkeratotic layers and shows differentiation between scattering properties of normal and dysplastic epithelium and invasive cancer.

Humans↗