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R Richards-Kortum

Publications and source records attributed to R Richards-Kortum.

At least 19 recordsLinked to original sources
PubMed2003

Optical systems for in vivo molecular imaging of cancer.

Progress toward a molecular characterization of cancer would have important clinical benefits; thus, there is an important need to image the molecular features of cancer in vivo. In this paper, we describe a comprehensive strategy to develop inexpensive, rugged and portable optical imaging systems for molecular imaging of cancer, which couples the development of optically active contrast agents with advances in functional genomics of cancer. We describe initial results obtained using optically active contrast agents to image the expression of three well known molecular signatures of neoplasia: including over expression of the epidermal growth factor receptor (EGFR), matrix metallo-proteases (MMPs), and oncoproteins associated with human papillomavirus (HPV) infection. At the same time, we are developing inexpensive, portable optical systems to image the morphologic and molecular signatures of neoplasia noninvasively in real time. These real-time, portable, inexpensive systems can provide tools to characterize the molecular features of cancer in vivo.

Biomarkers, Tumor↗
PubMed2002

Near real time in vivo fibre optic confocal microscopy: sub-cellular structure resolved.

We have built a fibre optic confocal reflectance microscope capable of imaging biological tissue in near real time. The measured lateral resolution is 3 micro m and axial resolution is 6 micro m. Images of epithelial cells, excised tissue biopsies, and the human lip in vivo have been obtained at 15 frames s-1. Both cell morphology and tissue architecture can be appreciated from images obtained with this microscope. This device has the potential to enable reflected light confocal imaging of internal organs for in situ detection of pathology.

Animals↗
PubMed2001

Reflectance spectroscopy for in vivo characterization of ovarian tissue.

BACKGROUND AND OBJECTIVE: To explore whether reflectance spectroscopy can differentiate normal ovary, benign neoplasms, and ovarian cancer. STUDY DESIGN/MATERIALS AND METHODS: Reflectance spectra (390-600 nm) were measured at three source-detector separations (SDS) in vivo at 64 sites in 16 patients undergoing oophorectomy. Parameters with largest statistical differences were identified. Based on these parameters algorithms were developed and evaluated. RESULTS: Promising parameters were the reflectance intensity from 540 to 580 nm (SDS, 1.1 mm), the slope of the reflectance spectrum from 490 to 520 nm (SDS, 1.1 mm), the slope from 510 to 530 nm (SDS, 2.1 mm), and the slope from 510 to 530 (SDS, 3 mm). Average sensitivity and specificity were 86 +/- 6% and 79 +/- 5% to separate normal ovary from benign neoplasms and cancers. Average sensitivity and specificity were 86 +/- 4% and 80 +/- 8% to separate ovarian cancers from benign neoplasms and normal ovary. CONCLUSION: Reflectance spectroscopy should be further investigated for ovarian cancer screening.

Algorithms↗
PubMed2001

Fluorescence spectroscopy of epithelial tissue throughout the dysplasia-carcinoma sequence in an animal model: spectroscopic changes precede morphologic changes.

BACKGROUND AND OBJECTIVE: The hamster cheek pouch carcinogenesis model, using chronic treatments of dimethylbenz[alpha]anthracene (DMBA) was used as a model system to investigate changes in epithelial tissue autofluorescence throughout the dysplasia-carcinoma sequence. STUDY DESIGN/MATERIALS AND METHODS: Fluorescence emission spectra were measured weekly from 42 DMBA-treated animals and 20 control animals at 337, 380, and 460 nm excitation. A subset of data in which histopathology was available was used to develop diagnostic algorithms to separate neoplastic and non-neoplastic tissue. The change in fluorescence intensity over time was examined in all samples at excitation-emission wavelength pairs identified as diagnostically useful. RESULTS: Algorithms based on autofluorescence can separate neoplastic and non-neoplastic tissue with 95% sensitivity and 93% specificity. Greatest contributions to diagnostic algorithms are obtained at 380 nm excitation, and 430, 470, and 600 nm emission. Changes in fluorescence intensity are apparent as early as 3 weeks after initial treatment with DMBA, whereas morphologic changes associated with dysplasia occur on average at 7.5-12.5 weeks after initial treatment. CONCLUSIONS: Fluorescence spectroscopy provides a potential tool to identify biochemical changes associated with dysplasia and hyperplasia, which precede morphologic changes observed in histologically stained sections.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed2001

Fluorescence spectroscopy for in vivo characterization of ovarian tissue.

BACKGROUND AND OBJECTIVE: The objective of this study was to explore whether fluorescence spectroscopy signatures differed between normal variations within the ovary, benign neoplasms, and ovarian cancer. STUDY DESIGN/MATERIALS AND METHODS: Ovarian tissue fluorescence emission spectra were collected sequentially at 18 excitation wavelengths ranging from 330 to 500 nm from 11 patients undergoing oophorectomy and assembled into fluorescence excitation emission matrices (EEMs); biopsies corresponded to the area interrogated. Spectral areas that could differentiate normal ovary, benign neoplasms, and cancers were evaluated, using histopathology as the reference standard. RESULTS: The most promising measurements are (1) the integrated fluorescence intensity from 400 to 430 nm excitation at 460 nm emission, and (2) the ratios of fluorescence intensities at 330 nm excitation, 385 and 500 nm emission, and at 375 and 415 nm excitation, 460 nm emission. Simple systems to visualize these optical signatures at laparoscopy could be designed. CONCLUSION: Fluorescence spectroscopy may have the ability to distinguish ovarian cancers from normal ovarian structures and benign neoplasms, as well as differentiate between normal variations and metaplastic structures and should be further explored as a device for the early detection of ovarian cancers.

Female↗
PubMed2001

Fast and noninvasive fluorescence imaging of biological tissues in vivo using a flying-spot scanner.

We have developed a flying-spot scanner (FSS), for fluorescence imaging of tissues in vivo. The FSS is based on the principles of single-pixel illumination and detection via a raster scanning technique. The principal components of the scanner are a laser light source, a pair of horizontal and vertical scanning mirrors to deflect the laser light in these respective directions on the tissue surface, and a photo multiplier tube (PMT) detector. This paper characterizes the performance of the FSS for fluorescence imaging of tissues in vivo. First, a signal-to-noise ratio (SNR) analysis is presented. This is followed by characterization of the experimental SNR, linearity and spatial resolution of the FSS. Finally, the feasibility of tissue fluorescence imaging is demonstrated using an animal model. In summary, the performance of the FSS is comparable to that of fluorescence-imaging systems based on multipixel illumination and detection. The primary advantage of the FSS is the order-of-magnitude reduction in the cost of the light source and detector. However, the primary disadvantage of the FSS its significantly slower frame rate (1 Hz). In applications where high frame rates are not critical, the FSS will represent a low-cost alternative to multichannel fluorescence imaging-systems.

Animals↗
PubMed2001

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.

Adult↗
PubMed2001

Autofluorescence microscopy of fresh cervical-tissue sections reveals alterations in tissue biochemistry with dysplasia.

Fluorescence spectroscopy offers an effective, noninvasive approach to the detection of precancers in multiple organ sites. Clinical studies have demonstrated that fluorescence spectroscopy can provide highly sensitive, specific and cost-effective diagnosis of cervical precancers. However, the underlying biochemical mechanisms responsible for differences in the fluorescence spectra of normal and dysplastic tissue are not fully understood. We designed a study to assess the differences in autofluorescence of normal and dysplastic cervical tissue. Transverse, fresh tissue sections were prepared from colposcopically normal and abnormal biopsies in a 34-patient study. Autofluorescence images were acquired at 380 and 460 nm excitation. Results showed statistically significant increases in epithelial fluorescence intensity (arbitrary units) at 380 nm excitation in dysplastic tissue (106 +/- 39) relative to normal tissue (85 +/- 30). The fluorophore responsible for this increase is possibly reduced nicotinamide adenine dinucleotide. Stromal fluorescence intensities in the dysplastic samples decreased at both 380 nm (102 +/- 34 [dysplasia] vs 151 +/- 44 [normal]) and 460 nm excitation (93 +/- 35 [dysplasia] vs 137 +/- 49 [normal]), wavelengths at which collagen is excited. Decreased redox ratio (17-40% reduction) in dysplastic tissue sections, indicative of increased metabolic activity, was observed in one-third of the paired samples. These results provide valuable insight into the biological basis of the differences in fluorescence of normal and precancerous cervical tissue.

Adult↗
PubMed2001

Biomarker modulation in a nonhuman rhesus primate model for ovarian cancer chemoprevention.

OBJECTIVE: The objective of this study was to explore whether a nonhuman primate model could be developed to test drugs for the prevention of ovarian cancer. METHODS: Nineteen adult female Rhesus macaques were given fenretinide (4HPR), oral contraceptives (OCP), the combination (4HPR + OCP), or no medication for 3 months. Exploratory laparotomy was done pre- and postdrug to assess intermediary biomarkers of neoplastic phenotype, proliferation, response pathways, and growth-regulatory and metabolic markers. Fluorescence emission spectra were plotted for each group pre- and postdrug and means were overlaid on these plots and normalized. Fluorescence intensities were compared using the 2-tailed Student t test, (P = 0.1-0.01). RESULTS: All monkeys tolerated drugs and surgeries without difficulty. Histochemical markers showed no significant trend. However, fluorescence spectroscopy showed increased intensity at 450 nm excitation, 550 nm emission correlating with increased FAD presence. The 4HPR group (P = 0.01) showed higher intensity than the OCP group (P = 0.05-0.07) when compared with the controls. Decreased emission was seen at 350 nm excitation, 450 nm emission correlating with decreased NAD(P)H presence. The OCP group showed the largest change (P < 0.01), and the control group showed the smallest change. CONCLUSIONS: The nonhuman primate is an excellent model to test drug effect on the ovarian surface epithelium and merits additional study. Fluorescence spectroscopy was the most sensitive marker for drug activity and the apparent increase in NAD and FAD in the 4HPR group is consistent with the effect of 4HPR observed in cell culture. The differences between the OCP and the 4HPR groups suggest a different mechanism of activity of these drugs.

Animals↗
PubMed2000

Autofluorescence patterns in short-term cultures of normal cervical tissue.

Fluorescence spectroscopy has potential to improve cervical precancer detection. The relationship between tissue biochemistry and fluorescence is poorly understood. The goal of this study was to characterize normal cervical autofluorescence, using fresh tissue short-term tissue cultures and epithelial cell suspensions. Transverse, short-term tissue cultures were prepared from 31 cervical biopsies; autofluorescence images were obtained at 380 and 460 nm excitation. Fluorescence excitation-emission matrices were measured from normal, precancerous and cancerous cervical cell suspensions. Observed fluorescence patterns contrast those reported for frozen-thawed tissue, and were placed into groups with (1) bright epithelial and weak stromal fluorescence; (2) similar epithelial and stromal fluorescence; and (3) weak epithelial and bright stromal fluorescence. The average ages of women in the groups were 30.9, 38.0 and 49.2 years. Epithelial fluorescence intensity was similar in Groups 1 and 2, but weaker in Group 3. Stromal intensity was similar in Groups 2 and 3, but weaker in Group 1. The ratio of epithelial to stromal fluorescence intensity was significantly different for all groups. EEMs of cell suspensions showed peaks consistent with tryptophan, reduced form of nicotinamide adenine dinucleotide (phosphate) and flavin adenine dinucleotide. Short-term tissue cultures represent a novel, biologically appropriate model to understand cervical autofluorescence. Our results suggest a biological basis for the increased fluorescence seen in older, postmenopausal women.

Adult↗
PubMed1999

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.

Adolescent↗
PubMed1999

Fluorescence spectroscopy of the cervix: influence of acetic acid, cervical mucus, and vaginal medications.

BACKGROUND AND OBJECTIVE: Fluorescence spectroscopy has been shown to provide information useful in the detection of cervical dysplasia. The goal of this study was to determine if substances found on the cervix such as acetic acid, mucus, and vaginal medications can influence the fluorescence in the spectral region useful for discriminating normal cervical tissue from abnormal tissue. STUDY DESIGN/MATERIALS AND METHODS: Fluorescence spectra were collected at 337 nm excitation from the cervix in vivo both before and after application of acetic acid; the data were analyzed to identify the effects of the acetic acid on the spectra. Cervical mucus was acquired from patients referred for colposcopy and frozen until measurements were taken. Fluorescence excitation-emission matrices (EEMs) were measured for the mucus samples. Additionally, the transmission spectra of mucus were measured to determine if its absorption could influence the fluorescence signal measured from the tissue. EEMs were measured for samples of commonly prescribed vaginal medications. All EEMs were compared to those of cervical biopsies. RESULTS: Acetic acid introduces changes in both the lineshape and intensity of the spectra. On average, the changes are more significant in spectra of abnormal tissue. Cervical mucus was found to have no significant absorption bands, but the measured fluorescence was approximately the same order of magnitude as that measured from the cervix in vitro. Most medications exhibited significant fluorescence in the spectral region of diagnostic interest for the cervix. CONCLUSIONS: Acetic acid appears to increase the differences in fluorescence emission spectra of normal and pre-cancerous cervical tissues; thus, its use is beneficial. The presence of cervical mucus can possibly interfere with the collection of fluorescence spectra for tissue classification. Patients should not use vaginal preparations during the 48 hours prior to tissue fluorescence measurements.

Acetic Acid↗
PubMed1999

Fluorescence spectroscopy for diagnosis of squamous intraepithelial lesions of the cervix.

OBJECTIVE: To calculate receiver operating characteristic (ROC) curves for fluorescence spectroscopy in order to measure its performance in the diagnosis of squamous intraepithelial lesions (SILs) and to compare these curves with those for other diagnostic methods: colposcopy, cervicography, speculoscopy, Papanicolaou smear screening, and human papillomavirus (HPV) testing. DATA SOURCES: Data from our previous clinical study were used to calculate ROC curves for fluorescence spectroscopy. Curves for other techniques were calculated from other investigators' reports. To identify these, a MEDLINE search for articles published from 1966 to 1996 was carried out, using the search terms "colposcopy," "cervicoscopy," "cervicography," "speculoscopy," "Papanicolaou smear," "HPV testing," "fluorescence spectroscopy," and "polar probe" in conjunction with the terms "diagnosis," "positive predictive value," "negative predictive value," and "receiver operating characteristic curve." METHODS OF STUDY SELECTION: We found 270 articles, from which articles were selected if they reported results of studies involving high-disease-prevalence populations, reported findings of studies in which colposcopically directed biopsy was the criterion standard, and included sufficient data for recalculation of the reported sensitivities and specificities. TABULATION, INTEGRATION, AND RESULTS: We calculated ROC curves for fluorescence spectroscopy using Bayesian and neural net algorithms. A meta-analytic approach was used to calculate ROC curves for the other techniques. Areas under the curves were calculated. Fluorescence spectroscopy using the neural net algorithm had the highest area under the ROC curve, followed by fluorescence spectroscopy using the Bayesian algorithm, followed by colposcopy, the standard diagnostic technique. Cervicography, Papanicolaou smear screening, and HPV testing performed comparably with each other but not as well as fluorescence spectroscopy and colposcopy. CONCLUSION: Fluorescence spectroscopy performs better than colposcopy and other techniques in the diagnosis of SILs. Because it also permits real-time diagnosis and has the potential of being used by inexperienced health care personnel, this technology holds bright promise.

Carcinoma in Situ↗
PubMed1999

Screening for squamous intraepithelial lesions with fluorescence spectroscopy.

OBJECTIVE: To evaluate the accuracy of fluorescence spectroscopy in screening for squamous intraepithelial lesions (SILs) and to compare its performance with that of Papanicolaou smear screening, colposcopy, cervicoscopy, cervicography, and human papillomavirus (HPV) testing. DATA SOURCES: Receiver operating characteristic (ROC) curve analysis was used to analyze performance by fluorescence spectroscopy (primary data) and other methods (secondary data). METHODS OF STUDY SELECTION: In our search, 275 articles were identified in MEDLINE (1966-1996). Articles were included if the investigators had studied a population in whom low disease prevalence was expected; used either Papanicolaou smear screening and colposcopy or colposcopically directed biopsy as a standard against which the screening technique was measured, and included enough data for recalculation of reported sensitivities and specificities. TABULATION, INTEGRATION, AND RESULTS: Receiver operating characteristic curves for fluorescence spectroscopy were calculated using a Bayesian algorithm, and ROC curves for the other screening methods were constructed using metaanalytic techniques. Areas under the ROC curves and Q points were calculated. Screening colposcopy had the highest area under the curve (0.95), followed by screening cervicography (0.90), HPV testing (0.88), cervicoscopy (0.85), fluorescence spectroscopy (0.76), and Papanicolaou smear screening (0.70). CONCLUSION: In terms of screening for SILs, fluorescence spectroscopy performed better than the standard technique, Papanicolaou smear screening, and less well than screening colposcopy, cervicography, HPV testing, and cervicoscopy. The promise of this research technique warrants further investigation.

Female↗
PubMed1999

A comparison of C/B ratios from studies using receiver operating characteristic curve analysis.

In receiver operating characteristic (ROC) curve analysis, the optimal cutoff value for a diagnostic test can be found on the ROC curve where the slope of the curve is equal to (C/B) x (1-p[D])/p[D], where p[D] is the disease prevalence and C/B is the ratio of net costs of treating nondiseased individuals to net benefits of treating diseased individuals. We conducted a structured review of the medical literature to examine C/B ratios found in ROC curve analysis. Only two studies were found in which a C/B ratio was explicitly calculated; in another 11 studies, a C/B ratio was based on a so-called holistic estimate, an all-encompassing educated estimate of the relative costs and benefits relevant to the clinical situation. The C/B ratios ranged from 0.0025 (tuberculosis screening) to 2.7 (teeth restoration for carious lesions). Clinical scenarios that are directly life threatening but curable had C/B ratios of less than 0.05. This analysis led us to construct a table of ordered C/B ratios that may be used by investigators to approximate C/B ratios for other clinical situations in order to establish cutpoints for new diagnostic tests.

Clinical Laboratory Techniques↗
PubMed1999

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.

Algorithms↗
PubMed1998

Noninvasive diagnosis of oral neoplasia based on fluorescence spectroscopy and native tissue autofluorescence.

OBJECTIVE: To evaluate the clinical potential of fluorescence spectroscopy (a noninvasive technique for assessing the chemical and morphologic composition of tissue) for in vivo detection of oral cavity neoplasia. DESIGN: A fluorescence spectroscopy system recorded spectra from oral cavity sites in 8 healthy volunteers and in 15 patients with premalignant or malignant oral cavity lesions at 337-, 365-, and 410-nm excitation wavelengths in the emission range of 350 to 700 nm. Fluorescence peak intensities and spectral line shapes were compared and diagnostic algorithms were developed to distinguish normal sites from abnormal sites. SETTING: The head and neck cancer clinic at a tertiary referral center in Houston, Tex. RESULTS: Differences were found in spectra from normal, dysplastic, and malignant oral mucosa. The fluorescence intensity of normal mucosa was greater than that of abnormal areas. In addition, the ratio of red region (635-nm) to blue region (455-490-nm) intensities was greater in abnormal areas. Diagnostic discrimination was achieved when test site spectra were compared with spectra from a normal site in the same patient. One diagnostic algorithm based on spectra at 337 nm gave a sensitivity of 88% and a specificity of 100%. CONCLUSIONS: Consistent differences exist between the fluorescence spectra of abnormal and normal oral mucosa. Therefore, fluorescence spectroscopy has the potential to improve the noninvasive diagnosis of oral cavity neoplasia. Further studies will better define the role of this technique in the detection of premalignant and early oral cancer lesions.

Adult↗