Biomedical subjects

Rebecca Richards-Kortum

Publications and source records attributed to Rebecca Richards-Kortum.

At least 19 recordsLinked to original sources

PubMed2004

Vision enhancement system for detection of oral cavity neoplasia based on autofluorescence.

BACKGROUND: Early detection of squamous cell carcinoma (SCC) in the oral cavity can improve survival. It is often difficult to distinguish neoplastic and benign lesions with standard white light illumination. We evaluated whether a technique that capitalizes on an alternative source of contrast, tissue autofluorescence, improves visual examination. METHODS: Autofluorescence of freshly resected oral tissue was observed visually and photographed at specific excitation/emission wavelength combinations optimized for response of the human visual system and tissue fluorescence properties. Perceived tumor margins were indicated for each wavelength combination. Punch biopsies were obtained from several sites from each specimen. Sensitivity and specificity were evaluated by correlating histopathologic diagnosis with visual impression. RESULTS: Best results were achieved with illumination at 400 nm and observation at 530 nm. Here, sensitivity and specificity were 91% and 86% in discrimination of normal tissue from neoplasia. This compares favorably with white light examination, in which sensitivity and specificity were 75% and 43%. CONCLUSIONS: Oral cavity autofluorescence can be easily viewed by the human eye in real time. Visual examination of autofluorescence enhances perceived contrast between normal and neoplastic oral mucosa in fresh tissue resections.

Biopsy, Needle↗

PubMed2004

The effects of repeated spectroscopic pressure measurements on fluorescence intensity in the cervix.

OBJECTIVE: Fluorescence spectroscopy is a promising technology for the detection of cervical squamous intraepithelial lesions (SILs). In this study we took repeated measures in the cervix to determine whether the order of measurement produces changes in fluorescence intensity and whether there are differences in variation due to pressure. METHODS: A pressure sensitive fiber-optic probe to measure fluorescence spectra was calibrated at light, medium, and firm levels (0.2, 0.4, 0.6 N). Measurements were made 3 times at each of 2 sites in the patient's cervix. Spectroscopic data were preprocessed and analyzed to compare order of pressure and intensity variability as a function of pressure on measurements. RESULTS: Four providers took 3 measurements from 2 sites each in 18 patients, yielding 108 measurements. After corrections for multiple comparisons, neither the order of probe pressure nor the variability of probe pressure significantly affected variations in fluorescence intensity. CONCLUSION: This study shows that the probe pressure variability is probably not an issue for these devices.

Adult↗

PubMed2004

In vivo pathology: microendoscopy as a new endoscopic imaging modality.

Confocal microendoscopy permits direct observation of pathologic change at the microscopic level rather than traditional inference based on indirect changes at the macroscopic (cell) level. The main benefit includes earlier detection of precancerous and cancer conditions through improved biopsy selection and examination and more cost-effective solutions to screening and surveillance. Numerous outstanding research and commercial groups with varying approaches to confocal microendoscopy are allocating significant efforts to making the technology commercially available. The initial instruments will likely be geared toward screening for and surveillance of esophageal and colon-related conditions. Future developments related to greater functionality, improved ease of use, and automated analysis are likely to facilitate adoption and use of the technology. Clinical gastroenterologists should look forward to the potential of confocal microendoscopy as a logical and needed modality to advance the field of gastroenterology.

Animals↗

PubMed2003

Cervical cancer chemoprevention, vaccines, and surrogate endpoint biomarkers.

At the Second International Conference on Cervical Cancer, held April 11-14, 2002, experts in cervical cancer prevention, detection, and treatment reviewed the need for more research in chemoprevention, including prophylactic and therapeutic vaccines, immunomodulators, peptides, and surrogate endpoint biomarkers. Investigators and clinicians noted the need for more rigorous Phase I randomized clinical trials, more attention to the risk factors that can affect study results in this patient population, and validation of optical technologies that will provide valuable quantitative information in real time regarding disease regression and progression. They discussed the role of the human papillomavirus (HPV) in cervical cancer development and the importance of developing strategies to suppress HPV persistence and progression. Results in Phase I randomized clinical trials have been disappointing because few have demonstrated statistically significant regression attributable to the agent tested. Researchers recommended using a transgenic mouse model to test and validate new compounds, initiating vaccine and immunomodulator trials, and developing immunologic surrogate endpoint biomarkers.

Biomarkers, Tumor↗

PubMed2003

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.

Cervix Uteri↗

PubMed2003

Real-time vital optical imaging of precancer using anti-epidermal growth factor receptor antibodies conjugated to gold nanoparticles.

Recent developments in photonic technology provide the ability to noninvasively image cells in vivo; these new cellular imaging technologies have the potential to dramatically improve the prevention, detection, and therapy of epithelial cancers. Endoscope-compatible microscopies, such as optical coherence tomography and reflectance confocal microscopy, image reflected light, providing a three-dimensional picture of tissue microanatomy with excellent spatial resolution (1-10 micro m). However, their ability to image molecular biomarkers associated with cancer is limited. Here, we describe a new class of molecular specific contrast agents for vital reflectance imaging based on gold nanoparticles attached to probe molecules with high affinity for specific cellular biomarkers. The application of gold bioconjugates for vital imaging of precancers is demonstrated using cancer cell suspensions, three-dimensional cell cultures, and normal and neoplastic fresh cervical biopsies. We show that gold conjugates can be delivered topically for imaging throughout the whole epithelium. These contrast agents have potential to extend the ability of vital reflectance microscopies for in vivo molecular imaging. They can potentially enable combined screening, detection, and therapy of disease using inexpensive imaging systems; such tools could allow mass screening of diseases such as cancer in resource-poor settings.

Antibodies, Monoclonal↗

PubMed2003

Patient distress and satisfaction with optical spectroscopy in cervical dysplasia detection.

OBJECTIVE: The aim of this investigation was to evaluate the impact of optical spectroscopy, a new approach for the detection of cervical dysplasia, on patient well-being and satisfaction. STUDY DESIGN: Patient distress and satisfaction with optical spectroscopy compared with the Papanicolaou test and colposcopically directed biopsy were measured in a volunteer sample of 314 women with no history of abnormal Papanicolaou test findings. RESULTS: Participants reported significantly less pain and anxiety (P<.001) during optical spectroscopy than during the Papanicolaou test or colposcopically directed biopsy. Generally, participants found spectroscopy equal to the Papanicolaou test and to biopsy on a variety of questions that measured satisfaction. There were statistically significant differences between spectroscopy and the Papanicolaou test or biopsy on issues such as the discomfort and fear caused by the test, the amount of time taken, the room lighting, and perceptions of accuracy. CONCLUSION: That patients reported less distress during spectroscopy than during a Papanicolaou test, colposcopy, or biopsy suggests the possibility of improved adherence to cervical cancer screening and follow-up in settings in which it is used.

Adult↗

PubMed2003

Optimal visual perception and detection of oral cavity neoplasia.

The most common way to detect disease is by visual inspection of the suspect tissue. However, the human eye is not optimized for this task because the perceived spectrum of light is divided into three channels, all of which have overlapping spectral sensitivity curves. Here, we present new methods to optimize visually perceived contrast based on spectral differences between normal and abnormal tissue. We apply these methods to the perception of fluorescence emission from the oral cavity. Abnormalities in the oral cavity are optimally perceived when the excitation is between nm. To optimally visualize fluorescence at 340-nm excitation, the emission should be observed through a blue bandpass filter transmitting light at 430 nm.

Color↗

PubMed2003

Light scattering from cervical cells throughout neoplastic progression: influence of nuclear morphology, DNA content, and chromatin texture.

A number of noninvasive fiber optic optical technologies are under development for real-time diagnosis of neoplasia. We investigate how the light scattering properties of cervical cells are affected by changes in nuclear morphology, DNA content, and chromatin texture, which occur during neoplastic progression. We used a Cyto-Savant computer-assisted image analysis system to acquire quantitative nuclear features measurements from 122 Feulgen-thionin-stained histopathologic sections of cervical tissue. A subset of the measured nuclear features was incorporated into a finite-difference time-domain (FDTD) model of cellular light scattering. The magnitude and angular distribution of scattered light was calculated for cervical cells as a function of pathologic grade. The nuclear atypia strongly affected light scattering properties. The increased size and elevated DNA content of nuclei in high-grade lesions caused the most significant changes in scattering intensity. The spatial dimensions of chromatin texture features and the amplitude of refractive index fluctuations within the nucleus impacted both the angular distribution of scattering angles and the total amount of scattered light. Cellular scattering is sensitive to changes in nuclear morphology that accompany neoplastic progression. Understanding the quantitative relationships between nuclear features and scattering properties will aid in the development of noninvasive optical technologies for detection of precancerous conditions.

Cell Nucleus↗

PubMed2003

Light scattering from normal and dysplastic cervical cells at different epithelial depths: finite-difference time-domain modeling with a perfectly matched layer boundary condition.

The finite-difference time-domain (FDTD) method provides a flexible approach to studying the scattering that arises from arbitrarily inhomogeneous structures. We implemented a three-dimensional FDTD program code to model light scattering from biological cells. The perfectly matched layer (PML) boundary condition has been used to terminate the FDTD computational grid. We investigated differences in angle-dependent scattering properties of normal and dysplastic cervical cells. Specifically, the scattering patterns and phase functions have been computed for normal and dysplastic cervical cells at three different epithelial depths, namely, basal/parabasal, intermediate, and superficial. Construction of cervical cells within the FDTD computational grid is based on morphological and chromatin texture features obtained from quantitative histopathology. The results show that angle-dependent scattering characteristics are different not only for normal and dysplastic cells but also for cells at different epithelial depths. The calculated scattering cross-sections are significantly greater for dysplastic cells. The scattering cross-sections of cells at different depths indicate that scattering decreases in going from the superficial layer to the intermediate layer, but then increases in the basal/parabasal layer. This trend for epithelial cell scattering has also been observed in confocal images of ex vivo cervical tissue.

Algorithms↗

PubMed2003

Effects of biographical variables on cervical fluorescence emission spectra.

Diagnostic algorithms can classify tissue samples as diseased or nondiseased based on fluorescence emission collected from the intact cervix. Such algorithms can distinguish high-grade squamous intraepithelial lesions from low-grade squamous intraepithelial lesions. An understanding of the effects of the values of biographical covariates, such as age, race, smoking, or menopausal status on the emission spectra for each patient could improve diagnostic efficiency. The analysis described was performed using data collected from two previously published clinical trials; one study measured spectra from 395 sites in 95 patients referred to a colposcopy clinic with abnormal Pap smears, and the second study measured spectra from 204 sites in 54 patients self-referred for screening and expected to have a normal Pap smear. For this analysis, data about age, race, menstrual cycle, and smoking were collected. The principal components from normalized data were compared. There are clear intensity differences observed with age and menopausal status; postmenopausal patients exhibit higher emission intensities. Differences associated with biographical variables need to be tested in larger studies, which stratify adequately for these variables. The addition of these biographical variables in the preprocessing of data could dramatically improve algorithm performance and applicability.

Adult↗

PubMed2003

Microanatomical and biochemical origins of normal and precancerous cervical autofluorescence using laser-scanning fluorescence confocal microscopy.

Clinical studies have shown that in vivo fluorescence spectroscopy can improve the diagnosis of cervical precancer. Recent work suggests that epithelial fluorescence increases, whereas stromal fluorescence decreases, with precancer. However, the microanatomic and biochemical sources of fluorescence in living cervical tissue have not yet been established. This study aims to characterize the origins of living normal and precancerous cervical fluorescence at microscopic levels using laser-scanning fluorescence confocal microscopy. Ten pairs of colposcopically normal and abnormal biopsies were obtained; transverse, 200 microm thick, short-term tissue cultures were prepared and imaged when viable with UV (351-364 nm) and 488 nm excitation before and after addition of the vital dye, Mitotracker Orange. In normal epithelium basal epithelial cells showed cytoplasmic fluorescence; parabasal, intermediate and superficial cells showed fluorescence only at the periphery of the cell. In low-grade precancers cytoplasmic fluorescence was visible in the bottom one-third of the epithelium; in high-grade precancers cytoplasmic fluorescence was visible throughout the lower two-thirds of the epithelium. Cytoplasmic fluorescence was colocalized with the MitoTracker probe and is attributed to mitochondrial reduced form of nicotinamide adenine dinucleotide at UV excitation and mitochondrial flavin adenine dinucleotide at 488 nm excitation. Stromal fluorescence originated from matrix fibers; with the development of precancer the density and fluorescence intensity of matrix fibers decrease. Autofluorescence properties of precancerous cervix reflect an increased number of metabolically active mitochondria in epithelial cells and a reduced stromal fluorescence, which can be an indicator for altered communication between precancerous epithelium and stroma. These changes can explain differences in in vivo fluorescence spectra of normal and precancerous cervical tissue.

Cervix Uteri↗

PubMed2002

Near real-time in vivo confocal imaging of mouse mammary tumors.

The goal of this study was to evaluate the ability of near real-time reflectance confocal microscopy to image tumor metastasis in vivo in an animal model. We used an epi-illumination confocal microscope to capture images of mouse mammary tumors in nude immunodeficient and Balb/C immunocompetent mice. In vivo confocal images and videos of normal and neoplastic areas were obtained before and after the application of a 6% acetic acid solution, with a lateral resolution of 0.8 microns and an axial resolution of 2-3 microns. Average imaging depths ranged from 150 microns to greater than 300 microns. We were able to differentiate between normal and abnormal tissue areas within the mammary gland, including areas of adipose tissue, fibroblasts and connective tissue, neoplastic tissue, and blood flow within blood vessels. Intravital imaging with reflectance confocal microscopy appears to be a useful tool to study tumor metastasis in vivo.

Animals↗

PubMed2002

Near real-time confocal microscopy of amelanotic tissue: detection of dysplasia in ex vivo cervical tissue.

RATIONALE AND OBJECTIVES: The authors performed this study to determine whether images of ex vivo tissue obtained with a near real-time confocal microscope can be used to differentiate between normal and dysplastic tissue. MATERIALS AND METHODS: Biopsy specimens of colposcopically normal and abnormal cervical tissue were obtained from 19 patients and imaged at various depths with a confocal microscope. Nuclear morphologic features were extracted from the confocal images; in addition, a group of reviewers examined the images and attempted to identify whether the specimen contained high-grade dysplasia. Results of both analyses were compared with the histopathologic findings of the same specimens provided by a board-certified pathologist with expertise in gynecologic pathology. RESULTS: The morphologic feature measurements compared well with the findings at pathologic examination. The use of the nuclear-cytoplasmic ratio to determine the presence of dysplasia resulted in a sensitivity of 100% and a specificity of 91%. The untrained reviewers had an average sensitivity of 95% and an average specificity of 69% in the determination of dysplasia. CONCLUSION: The results indicate the clinical potential of in vivo confocal imaging in the detection of dysplasia.

Carcinoma in Situ↗

PubMed2002

Optical spectroscopy for detection of neoplasia.

Fluorescence and reflectance spectroscopy provide the ability to assess tissue structure and metabolism in vivo in real time, providing improved diagnosis of pre-cancerous lesions. Reflectance spectroscopy can probe changes in epithelial nuclei that are important in pre-cancer detection, such as mean nuclear diameter, nuclear size distribution and nuclear refractive index. Fluorescence spectroscopy can probe changes in epithelial cell metabolism, by assessing mitochondrial fluorophores, and epithelial-stromal interactions, by assessing the decrease in collagen crosslink fluorescence that occurs with pre-cancer. Thus, fluorescence and reflectance spectroscopy provide complementary information useful for pre-cancer diagnosis. Tissue engineering provides three-dimensional cell cultures that can be used to further explore the relationship between tissue structure and biological events important in cancer development and progression. In the future, improving our understanding of the biological changes that can be assessed using spectroscopy will not only improve optical techniques but also provide new tools to better understand cancer biology.

Animals↗

PubMed2002

Fiber-optic confocal reflectance microscope with miniature objective for in vivo imaging of human tissues.

We have built a fiber-optic confocal reflectance microscope capable of imaging human tissues in near real time. Miniaturization of the objective lens and the mechanical components for positioning and axially scanning the objective enables the device to be used in inner organs of the human body. The lateral resolution is 2 micrometers and axial resolution is 10 micrometers. Confocal images of fixed tissue biopsies and the human lip in vivo have been obtained at 15 frames/s without any fluorescent stains. Both cell morphology and tissue architecture can be appreciated from images obtained with this microscope.

Biopsy↗

PubMed2002

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.

Carcinoma, Squamous Cell↗

PubMed2002

Realistic three-dimensional epithelial tissue phantoms for biomedical optics.

We introduce new realistic three-dimensional tissue phantoms which can help to understand the optical properties of human epithelium as well as the optical signatures associated with the dysplasia to carcinoma sequence. The phantoms are based on a step by step multilayer reconstitution of the epithelial tissue using main components characteristic for the human epithelium. Each consecutive step is aimed to increase the similarity between real tissue and a phantom. We began by modeling the stromal layer which predominantly consists of a network of collagen bundles. Phantoms consisting of a collagen matrix alone and in the presence of embedded cervical cells were created. Their morphology and fluorescence properties were studied and were compared with those of cervical epithelium. We show that the phantoms resemble the microstructure and the optical properties of the human epithelial tissue. We also demonstrate that the proposed phantoms provide an opportunity to study changes in optical properties of different tissue components as a result of their interactions with each other or exogenous factors.

Biomedical Technology↗