In vivo light scattering measurements for detection of precancerous conditions of the cervix

Hyperspectral imaging as a new diagnostic tool for cervical intraepithelial neoplasia

PURPOSE

Cervical cancer screening by visual inspection with acetic acid (VIA) during colposcopy can be challenging and is highly dependent on the clinical experience of the examiner. Health-care systems lack qualified physicians able to perform the examination in both industrialized and low- and middle-income countries. Previous work has shown the general potential of hyperspectral imaging (HSI) to discriminate CIN from normal tissue, but clinical translation has been limited due to the lack of medically approved HSI systems.

METHODS

In this study, we evaluate the feasibility of a commercially available HSI system for CIN detection in a prospective monocentric clinical trial.

RESULTS

By obtaining spectral fingerprints of 41 patients with CIN 1-3 we show that HSI-based differentiation between CIN and normal tissue is possible with high statistical significance. Major spectral differences were seen in the 555-585 wavelength area.

CONCLUSION

HSI advances tissue differentiation by associating each pixel with high-dimensional spectra and thereby obtains morphological and biochemical information of the observed tissue. Currently available and medically approved HSI systems may represent a contact- and marker-free examiner-independent method for the diagnosis of CIN.

The detection of cervical neoplasia via optical ımaging: a pilot clinical study

PURPOSE

The present study aims to develop a new high-resolution imaging system for the early diagnosis of cervical neoplasia based on increased vessel density of the cervical tissue.

METHODS

An optical device was developed to obtain high contrast and resolution images of vascular structures of the cervix in the present study. The device utilizes a telecentric lens to capture cervix images under light illumination with a wavelength of 550 nm emitted from LEDs. Images were obtained using the telecentric lens with or without acetic acid application to the cervix. Image processing algorithms were used to contrast and extract the skeleton of the vascular structures on the cervix. In the evaluation of the vascular density, the cervical images were divided into 12 o'clock positions, and the fractal dimension of the vascularity was calculated for each dial area between the o'clock positions. The region with the largest fractal dimension was accepted as the region with the highest probability of lesion. The range of vessel sizes was split into small classes of "bins" for each dial area with the highest fractal dimension. To validate the system's success in differentiating between normal and HSIL lesions, forty five patients who underwent colposcopy and biopsy were included in a pilot study.

RESULTS

The system correctly classified four HSIL cases out of five and failed to detect one HSIL case, achieving an accuracy rate of 97.8% with an 80% sensitivity and 100% specificity.

CONCLUSION

The developed high-resolution optical imaging system may potentially be used in detecting cervical neoplasia just before the biopsy and reduce the number of false-positive cases.

Study of cervical precancerous lesions detection by spectroscopy and support vector machine

BACKGROUND AND OBJECTIVE

Diffuse reflectance spectroscopy (DRS) offers a fast, non-invasive, and low-cost alternative for cervical cancer diagnosis. We aim to develop a method for screening precancerous lesions based on DRS.

MATERIAL AND METHODS

Characteristic parameters of cervical tissue were extracted from spectra, including optical characteristic parameters such as absorption and scattering coefficients, and some slope and area parameters of the spectrum. Data were randomly divided into training (60%) and test (40%) sets. Of the 210 included patients, 166 were healthy, 22 had erosion of the cervix, and 31 had cervical intraepithelial neoplasia (CIN). The support vector machine (SVM) algorithm was used to classify normal and abnormal cervical tissue based on 11 characteristic parameters.

RESULTS

The SVM with linear kernel function, applied on the training data, could distinguish tissue with lesions from healthy tissue with an accuracy of 1.00. When the classifiers were applied to the test set, erosion of cervix and CIN could be discriminated from healthy tissue with an accuracy of 0.95 (±0.03).

CONCLUSIONS

This research shows that the diagnostic algorithm can be valuable for non-invasive diagnosis of cervical cancer. This is a significant step toward the development of a tool for tissue assessment of cervical cancer.

Combined reflectance spectroscopy and coherent light backscattering measurement differentiate cervical cancer from normal epithelial tissue in a xenograft mouse model

Cervical cancer is a type of slow-growing cancer associated with high mortality rates. Early detection can enable lifesaving early intervention. Current cervical premalignant lesion detection methods suffer from both high miss rates and excessive referrals for unnecessary biopsies. Herein, coherent light backscatter and modifications in reflected white-light spectra were measured to specifically discriminate between cervical tumors and normal squamous epithelial tissues resected from a mouse xenograft model. The combined measurements resulted in 92% sensitivity and 93% specificity in discrimination between the two tissues. These methods can be used to develop a noninvasive portable optical probe for sensitive and objective detection of precancer and cancer epithelial lesions in the cervix and other accessible epithelial tissues.

Novel advancements in colposcopy: historical perspectives and a systematic review of future developments

OBJECTIVE

To describe novel innovations and techniques for the detection of high-grade dysplasia.

MATERIALS AND METHODS

Studies were identified through the PubMed database, spanning the last 10 years. The key words (["computerized colposcopy" or "digital colposcopy" or "spectroscopy" or "multispectral digital colposcopy" or "dynamic spectral imaging", or "electrical impedance spectroscopy" or "confocal endomicroscopy" or "confocal microscopy"or "optical coherence tomography"] and ["cervical dysplasia" or cervical precancer" or "cervix" or "cervical"]) were used. The inclusion criteria were published articles of original research referring to noncolposcopic evaluation of the cervix for the detection of cervical dysplasia. Only English-language articles from the past 10 years were included, in which the technologies were used in vivo, and sensitivities and specificities could be calculated.

RESULTS

The single author reviewed the articles for inclusion. Primary search of the database yielded 59 articles, and secondary cross-reference yielded 12 articles. Thirty-two articles met the inclusion criteria.

CONCLUSIONS

An instrument that globally assesses the cervix, such as computer-assisted colposcopy, optical spectroscopy, and dynamic spectral imaging, would provided the most comprehensive estimate of disease and is therefore best suited when treatment is preferred. Electrical impedance spectroscopy, confocal microscopy, and optical coherence tomography provide information at the cellular level to estimate histology and are therefore best suited when deferment of treatment is preferred. If a device is to eventually replace the colposcope, it will likely combine technologies to best meet the needs of the target population, and as such, no single instrument may prove to be universally appropriate. Analyses of false-positive rates, additional colposcopies and biopsies, cost, and absolute life-savings will be important when considering these technologies and are limited thus far.

Early detection of high-grade squamous intraepithelial lesions in the cervix with quantitative spectroscopic imaging

Quantitative spectroscopy has recently been extended from a contact-probe to wide-area spectroscopic imaging to enable mapping of optical properties across a wide area of tissue. We train quantitative spectroscopic imaging (QSI) to identify cervical high-grade squamous intraepithelial lesions (HSILs) in 34 subjects undergoing the loop electrosurgical excision procedure (LEEP subjects). QSI's performance is then prospectively evaluated on the clinically suspicious biopsy sites from 47 subjects undergoing colposcopic-directed biopsy. The results show the per-subject normalized reduced scattering coefficient at 700 nm (An) and the total hemoglobin concentration are significantly different (p<0.05) between HSIL and non-HSIL sites in LEEP subjects. An alone retrospectively distinguishes HSIL from non-HSIL with 89% sensitivity and 83% specificity. It alone applied prospectively on the biopsy sites distinguishes HSIL from non-HSIL with 81% sensitivity and 78% specificity. The findings of this study agree with those of an earlier contact-probe study, validating the robustness of QSI, and specifically An, for identifying HSIL. The performance of An suggests an easy to use and an inexpensive to manufacture monochromatic instrument is capable of early cervical cancer detection, which could be used as a screening and diagnostic tool for detecting cervical cancer in low resource countries.

The use of optical spectroscopy for in vivo detection of cervical pre-cancer

In order to investigate the effectiveness of optical spectroscopy for in vivo diagnosis of cervical pre-cancerous conditions, a series of published studies are surveyed. The six optical technologies investigated include fluorescence spectroscopy, reflectance spectroscopy, and their combination using point probe or multispectral imaging approaches. Searching in the well-known databases, the most recent published works were sought out. Various aspects of the studies were evaluated including the details of the technology used, the pathologic threshold for tissue classification and the gold standard, the study population and prevalence of disease in this population, the method of measurement, the number of clinicians involved in the study, the classification and validation algorithms, and the performance in terms of sensitivity, specificity and, when available, the area under the receiver operating characteristic curve. Forty-four studies conducted from 1994 to 2012 were evaluated. The data are gathered in two comprehensive tables, and five illustrations are provided to simplify a comparison between studies from different points of view. There is a broad band of studies from small pilot studies through phase III clinical trials. Among the reviewed articles, only three factors were found to influence the performance of the optical spectroscopy studies. Multispectral approaches show higher specificity than the point probe approaches (p = 0.001). The use of acetic acid before measurement and prevalence of disease among the studied population, also, have an impact on the sensitivity and specificity of the studies (p < 0.05), respectively.

Adjunctive colposcopy technologies for examination of the uterine cervix--DySIS, LuViva Advanced Cervical Scan and Niris Imaging System: a systematic review and economic evaluation

BACKGROUND

Women in England (aged 25-64 years) are invited for cervical screening every 3-5 years to assess for cervical intraepithelial neoplasia (CIN) or cancer. CIN is a term describing abnormal changes in the cells of the cervix, ranging from CIN1 to CIN3, which is precancerous. Colposcopy is used to visualise the cervix. Three adjunctive colposcopy technologies for examination of the cervix have been included in this assessment: Dynamic Spectral Imaging System (DySIS), the LuViva Advanced Cervical Scan and the Niris Imaging System.

OBJECTIVE

To determine the clinical effectiveness and cost-effectiveness of adjunctive colposcopy technologies for examination of the uterine cervix for patients referred for colposcopy through the NHS Cervical Screening Programme.

DATA SOURCES

Sixteen electronic databases [Allied and Complementary Medicine Database (AMED), BIOSIS Previews, Cochrane Database of Systematic Reviews (CDSR), Cochrane Central Register of Controlled Trials (CENTRAL), Cumulative Index to Nursing and Allied Health Literature (CINAHL), Database of Abstracts of Reviews of Effects (DARE), EMBASE, Health Management Information Consortium (HMIC), Health Technology Assessment (HTA) database; Inspec, Inside Conferences, MEDLINE, NHS Economic Evaluation Database (NHS EED), PASCAL, Science Citation Index Expanded (SCIE) and Science Citation Index (SCI) - Conference Proceedings], and two clinical trial registries [ClinicalTrials.gov and Current Controlled Trials (CCT)] were searched to September-October 2011.

REVIEW METHODS

Studies comparing DySIS, LuViva or Niris with conventional colposcopy were sought; a narrative synthesis was undertaken. A decision-analytic model was developed, which measured outcomes in terms of quality-adjusted life-years (QALYs) and costs were evaluated from the perspective of the NHS and Personal Social Services with a time horizon of 50 years.

RESULTS

Six studies were included: two studies of DySIS, one study of LuViva and three studies of Niris. The DySIS studies were well reported and had a low risk of bias; they found higher sensitivity with DySIS (both the DySISmap alone and in combination with colposcopy) than colposcopy alone for identifying CIN2+ disease, although specificity was lower with DySIS. The studies of LuViva and Niris were poorly reported and had limitations, which indicated that their results were subject to a high risk of bias; the results of these studies cannot be considered reliable. The base-case cost-effectiveness analysis suggests that both DySIS treatment options are less costly and more effective than colposcopy alone in the overall weighted population; these results were robust to the ranges tested in the sensitivity analysis. DySISmap alone was more costly and more effective in several of the referral groups but the incremental cost-effectiveness ratio (ICER) was never higher than £1687 per QALY. DySIS plus colposcopy was less costly and more effective in all reasons for referral. Only indicative analyses were carried out on Niris and LuViva and no conclusions could be made on their cost-effectiveness.

LIMITATIONS

The assessment is limited by the available evidence on the new technologies, natural history of the disease area and current treatment patterns.

CONCLUSIONS

DySIS, particularly in combination with colposcopy, has higher sensitivity than colposcopy alone. There is no reliable evidence on the clinical effectiveness of LuViva and Niris. DySIS plus colposcopy appears to be less costly and more effective than both the DySISmap alone and colposcopy alone; these results were robust to the sensitivity analyses undertaken. Given the lack of reliable evidence on LuViva and Niris, no conclusions on their potential cost-effectiveness can be drawn. There is some uncertainty about how generalisable these findings will be to the population of women referred for colposcopy in the future, owing to the introduction of the human papillomavirus (HPV) triage test and uptake of the HPV vaccine.

Optical spectroscopy: current advances and future applications in cancer diagnostics and therapy

Optical spectroscopy (OS) is a tissue-sensing technique that could enhance cancer diagnosis and treatment in the near future. With OS, tissue is illuminated with a selected light spectrum. Different tissue types can be distinguished from each other based on specific changes in the reflected light spectrum that are a result of differences on a molecular level between compared tissues. Therefore, OS has the potential to become an important optical tool for cancer diagnosis and treatment monitoring. In recent years, significant progress has been made in the discriminating abilities of OS techniques between normal and cancer tissues of multiple human tissue types. This article provides an overview of the advances made with diffuse reflectance, fluorescence and Raman spectroscopy techniques in the field of clinical oncology, and focuses on the different clinical applications that OS could enhance.

Has fluorescence spectroscopy come of age? A case series of oral precancers and cancers using white light, fluorescent light at 405 nm, and reflected light at 545 nm using the Trimira Identafi 3000

BACKGROUND

Optical spectroscopy devices are being developed and tested for the screening and diagnosis of cancer and precancer in multiple organ sites. The studies reported here used a prototype of a device that uses white light, green-amber light at 545 nm, and violet light at 405 nm. Given that oral neoplasia is rare, the need for a device that increases the sensitivity of comprehensive white light oral screening is evident. Such a device, in the hands of dentists, family practitioners, otorhinolaryngologists, general surgeons, obstetrician gynecologists, and internists, could greatly increase the number of patients who have lesions detected in the precancerous phase.

OBJECTIVES

The objective of this study was to present a case series of oral precancers and cancers that have been photographed during larger ongoing clinical trials.

METHODS

Over 300 patients were measured at 2 clinical sites that are comprehensive cancer centers and a faculty practice associated with a major dental school. Each site is conducting independent research on the sensitivity and specificity of several optical technologies for the diagnosis of oral neoplasia. The cases presented in this case series were taken from the larger database of images from the clinical trials using the aforementioned device. Optical spectroscopy was performed and biopsies obtained from all sites measured, representing abnormal and normal areas on comprehensive white light examination and after use of the fluorescence and reflectance spectroscopy device. The gold standard of test accuracy was the histologic report of biopsies read by the study histopathologists at each of the 3 study sites.

RESULTS

Comprehensive white light examination showed some lesions; however, the addition of a fluorescence image and a selected reflectance wavelength was helpful in identifying other characteristics of the lesions. The addition of the violet light-induced fluorescence excited at 405 nm provided an additional view of both the stromal neovasculature of the lesions and the stromal changes associated with lesion growth that were biologically indicative of stromal breakdown. The addition of 545 nm green-amber light reflectance increased the view of the keratinized image and allowed the abnormal surface vasculature to be more prominent.

CONCLUSIONS

Optical spectroscopy is a promising technology for the diagnosis of oral neoplasia. The conclusion of several ongoing clinical trials and an eventual randomized Phase III clinical trial will provide definitive findings that sensitivity is or is not increased over comprehensive white light examination.

Physician attitudes toward dissemination of optical spectroscopy devices for cervical cancer control: an industrial-academic collaborative study

BACKGROUND

Optical spectroscopy has been studied for biologic plausibility, technical efficacy, clinical effectiveness, patient satisfaction, and cost-effectiveness.

OBJECTIVE

We sought to identify health care provider attitudes or practices that might act as barriers or to the dissemination of this new technology.

METHODS

Through an academic-industrial partnership, we conducted a series of focus groups to examine physician barriers to optical diagnosis. The study was conducted in 2 stages. First, a pilot group of 10 physicians (8 obstetrician gynecologists and 2 family practitioners) was randomly selected from 8 regions of the United States and each physician was interviewed individually. Physicians were presented with the results of a large trial (N = 980) testing the accuracy of a spectroscopy-based device in the detection of cervical neoplasia. They were also shown a prototype of the device and were given a period of time to ask questions and receive answers regarding the device. They were also asked to provide feedback on a questionnaire that was then revised and presented to 3 larger focus groups (n = 13, 15, and 17 for a total N = 45). The larger focus groups were conducted during national scientific meetings with 20 obstetrician gynecologists and 25 primary care physicians (family practitioners and internists).

RESULTS

When asked about the dissemination potential of the new cervical screening technology, all study groups tended to rely on established clinical guidelines from their respective professional societies with regard to the screening and diagnosis of cervical cancer. In addition, study participants consistently agreed that real-time spectroscopy would be viewed positively by their patients. Participants were positive about the new technology's potential as an adjunct to colposcopy and agreed that the improved accuracy would result in reduced health care costs (due to decreased biopsies and decreased visits). Although all participants saw the potential of real-time diagnosis, there were many perceived barriers. These barriers included changes in scheduling and work-flow, liability, documentation, ease of use, length of training, device cost, and reimbursement by third-party payers.

CONCLUSIONS

Barriers exist to the dissemination of optical technologies into physician practice. These will need to be addressed before cervical screening and diagnosis programs can take advantage of spectroscopy-based instruments for cancer control.

Accuracy of optical spectroscopy for the detection of cervical intraepithelial neoplasia without colposcopic tissue information; a step toward automation for low resource settings

Optical spectroscopy has been proposed as an accurate and low-cost alternative for detection of cervical intraepithelial neoplasia. We previously published an algorithm using optical spectroscopy as an adjunct to colposcopy and found good accuracy (sensitivity=1.00 [95% confidence interval (CI)=0.92 to 1.00], specificity=0.71 [95% CI=0.62 to 0.79]). Those results used measurements taken by expert colposcopists as well as the colposcopy diagnosis. In this study, we trained and tested an algorithm for the detection of cervical intraepithelial neoplasia (i.e., identifying those patients who had histology reading CIN 2 or worse) that did not include the colposcopic diagnosis. Furthermore, we explored the interaction between spectroscopy and colposcopy, examining the importance of probe placement expertise. The colposcopic diagnosis-independent spectroscopy algorithm had a sensitivity of 0.98 (95% CI=0.89 to 1.00) and a specificity of 0.62 (95% CI=0.52 to 0.71). The difference in the partial area under the ROC curves between spectroscopy with and without the colposcopic diagnosis was statistically significant at the patient level (p=0.05) but not the site level (p=0.13). The results suggest that the device has high accuracy over a wide range of provider accuracy and hence could plausibly be implemented by providers with limited training.

Assessing the contribution of cell body and intracellular organelles to the backward light scattering

We report a method of assessing the contribution of whole cell body and its nucleus to the clinically most relevant backward light scattering. We first construct an experimental system that can measure forward scattering and use the system to precisely extract the optical properties of a specimen such as the refractive index contrast, size distribution, and their density. A system that can simultaneously detect the backscattered light is installed to collect the backscattering for the same specimen. By comparing the measured backscattering spectrum with that estimated from the parameters determined by the forward scattering experiment, the contribution of cell body and nucleus to the backward light scattering is quantitatively assessed. For the HeLa cells in suspension, we found that the cell body contributes less than 10% and cell nucleus on the order of 0.1% to the total backscattering signal. Quantitative determination of the origin of backscattered light may help design a system that aims for detecting particular structure of biological tissues.

Separation of normal and premalignant cervical epithelial cells using confocal light absorption and scattering spectroscopic microscopy ex vivo

Confocal light absorption and scattering spectroscopic (CLASS) microscopy can detect changes in biochemicals and the morphology of cells. It is therefore used to detect high-grade cervical squamous intraepithelial lesion (HSIL) cells in the diagnosis of premalignant cervical lesions. Forty cervical samples from women with abnormal Pap smear test results were collected, and twenty cases were diagnosed as HSIL; the rest were normal or low-grade cervical squamous intraepithelial lesion (LSIL). The enlarged and condensed nuclei of HSIL cells as viewed under CLASS microscopy were much brighter and bigger than those of non-HSIL cells. Cytological elastic scattered light data was then collected at wavelengths between 400 and 1000 nm. Between 600 nm to 800 nm, the relative elastic scattered light intensity of HSIL cells was higher than that of the non-HSIL. Relative intensity peaks occurred at 700 nm and 800 nm. CLASS sensitivity and specificity results for HSIL and non-HSIL compared to cytology diagnoses were 80% and 90%, respectively. This study demonstrated that CLASS microscopy could effectively detect cervical precancerous lesions. Further study will verify this conclusion before the method is used in clinic for early detection of cervical cancer.

Detecting high-grade squamous intraepithelial lesions in the cervix with quantitative spectroscopy and per-patient normalization

This study develops a spectroscopic algorithm for detection of cervical high grade squamous intraepithelial lesions (HSILs). We collected reflectance and fluorescence spectra with the quantitative spectroscopy probe to measure nine spectroscopic parameters from 43 patients undergoing standard colposcopy with directed biopsy. We found that there is improved accuracy for distinguishing HSIL from non-HSIL (low grade SIL and normal tissue) when we "normalized" spectroscopy parameters by dividing the values extracted from each clinically determined suspicious site by the corresponding value extracted from a clinically normal squamous site from the same patient. The "normalized" scattering parameter (A) at 700nm, best distinguished HSIL from non-HSIL with sensitivity and specificity of 89% and 79% suggesting that a simple, monochromatic instrument measuring only A may accurately detect HSIL.

Towards a field-compatible optical spectroscopic device for cervical cancer screening in resource-limited settings: effects of calibration and pressure

Quantitative optical spectroscopy has the potential to provide an effective low cost, and portable solution for cervical pre-cancer screening in resource-limited communities. However, clinical studies to validate the use of this technology in resource-limited settings require low power consumption and good quality control that is minimally influenced by the operator or variable environmental conditions in the field. The goal of this study was to evaluate the effects of two sources of potential error: calibration and pressure on the extraction of absorption and scattering properties of normal cervical tissues in a resource-limited setting in Leogane, Haiti. Our results show that self-calibrated measurements improved scattering measurements through real-time correction of system drift, in addition to minimizing the time required for post-calibration. Variations in pressure (tested without the potential confounding effects of calibration error) caused local changes in vasculature and scatterer density that significantly impacted the tissue absorption and scattering properties Future spectroscopic systems intended for clinical use, particularly where operator training is not viable and environmental conditions unpredictable, should incorporate a real-time self-calibration channel and collect diffuse reflectance spectra at a consistent pressure to maximize data integrity.

Different optical properties between human hepatocellular carcinoma tissues and non-tumorous hepatic tissues in vitro

There has been an ongoing search for clinically acceptable methods for the accurate, efficient and simple diagnosis and prognosis of hepatocellular carcinoma (HCC). Optical spectroscopy is a technique with potential clinical applications to diagnose cancer diseases. The purpose of this study was to obtain the optical properties of HCC tissues and non-tumorous hepatic tissues and identify the difference between them. A total of 55 tissue samples (HCC tissue, n=38; non-tumorous hepatic tissue, n=17) were surgically resected from patients with HCC. The optical parameters were measured in 10-nm steps using single-integrating-sphere system in the wavelength range of 400 to 1800 nm. It was found that the optical properties and their differences varied with the wavelength for the HCC tissue and the non-tumorous hepatic tissue in the entire wavelength range of research. The absorption coefficient of the HCC tissue (1.48±0.99, 1.46±0.88, 0.86±0.61, 2.15±0.53, 0.54±0.10, 0.79±0.15 mm(-1)) was significantly lower than that of the non-tumorous hepatic tissue (2.79±1.73, 3.13±1.47, 3.06±2.79, 2.57±0.55, 0.62±0.10, 0.93±0.16 mm(-1)) at wavelengths of 400, 410, 450, 1450, 1660 and 1800 nm, respectively (P<0.05). The reduced scattering coefficient of HCC tissue (5.28±1.70, 4.91±1.54, 1.26±0.35 mm(-1)) and non-tumorous hepatic tissue (8.14±3.70, 9.27±3.08, 2.55±0.57 mm(-1)) was significantly different at 460, 500 and 1800 nm respectively (P<0.05). These results show different pathologic liver tissues have different optical properties. It provides a better understanding of the relationship between optical parameters and physiological characteristics in human liver tissues. And it would be very useful for developing a non-invasive, real-time, simple and efficient way for medical management of HCC in the future.

Recent advances in optical imaging for cervical cancer detection

Cervical cancer is one of the most common and lethal gynecological malignancies in both developing and developed countries, and therefore, there is a considerable interest in early diagnosis and treatment of precancerous lesions. Although the current standard care mainly based on cytology and colposcopy has reduced rates of cervical cancer morbidity and mortality, many lesions are still missed or overcalled and referred for unnecessary biopsies. Optical imaging technologies, spectroscopy approaches and high-resolution imaging methods are anticipated to improve the conventional cervical cancer screening providing in vivo diagnosis with high sensitivity and specificity. Their concept is that morphologic and biochemical properties of the cervical tissue are altered in response to its malignant transformation. In addition, contrast agents that target against specific neoplastic biomarkers can enhance the effectiveness of this new technology. Due to the unprecedented growth of these optical techniques accompanied probably by favorable cost-effectiveness, the primary detection of premalignant lesions may become more accessible in both the developing and the developed countries and can offer see-to-treat workflows and early therapeutic interventions.

Accuracy of optical spectroscopy for the detection of cervical intraepithelial neoplasia: Testing a device as an adjunct to colposcopy

Testing emerging technologies involves the evaluation of biologic plausibility, technical efficacy, clinical effectiveness, patient satisfaction, and cost-effectiveness. The objective of this study was to select an effective classification algorithm for optical spectroscopy as an adjunct to colposcopy and obtain preliminary estimates of its accuracy for the detection of CIN 2 or worse. We recruited 1,000 patients from screening and prevention clinics and 850 patients from colposcopy clinics at two comprehensive cancer centers and a community hospital. Optical spectroscopy was performed, and 4,864 biopsies were obtained from the sites measured, including abnormal and normal colposcopic areas. The gold standard was the histologic report of biopsies, read 2 to 3 times by histopathologists blinded to the cytologic, histopathologic, and spectroscopic results. We calculated sensitivities, specificities, receiver operating characteristic (ROC) curves, and areas under the ROC curves. We identified a cutpoint for an algorithm based on optical spectroscopy that yielded an estimated sensitivity of 1.00 [95% confidence interval (CI) = 0.92-1.00] and an estimated specificity of 0.71 [95% CI = 0.62-0.79] in a combined screening and diagnostic population. The positive and negative predictive values were 0.58 and 1.00, respectively. The area under the ROC curve was 0.85 (95% CI = 0.81-0.89). The per-patient and per-site performance were similar in the diagnostic and poorer in the screening settings. Like colposcopy, the device performs best in a diagnostic population. Alternative statistical approaches demonstrate that the analysis is robust and that spectroscopy works as well as or slightly better than colposcopy for the detection of CIN 2 to cancer.

Effect of bile absorption coefficients on the estimation of liver tissue optical properties and related implications in discriminating healthy and tumorous samples

We investigated differences between healthy tissue and metastatic tumor from ex vivo human partial liver resections using diffuse optical spectroscopy with a fiber optic probe. We extracted various physiological and morphological parameters from the spectra. During evaluation of the residual between the measurements and a fit model based on diffusion theory, we found that bile is an additional chromophore absorbing in the visible wavelength range that was missing in our model. Consistency of the residual with the absorption spectrum of bile was noticed. An accurate measurement of the absorption coefficient of bile from various human bile samples was performed and implemented into the fit model. Having the absorption coefficient of bile as a priori knowledge in the model showed a clear improvement in terms of reducing the fitting discrepancies. The addition of this chromophore yields significantly different estimates of the amount of blood. Furthermore, the estimated bile volume fraction and reduced scattering amplitude turned out to be two main relevant discriminators between normal and metastatic liver tissues.

Sensitivity of spatially resolved reflectance signals to coincident variations in tissue optical properties

Canonical correlation analysis, a multivariate statistical technique, was used to investigate the degree of association between tissue optical properties and spatially resolved reflectance signals. Monte Carlo modeling was employed to simulate signals corresponding to different combinations of optical properties and these data sets were fed as input to statistical analysis. The results show that it is possible to adjust the separation and angular orientation of source and detector fibers such that the effect of a particular optical property will be augmented among coincident variations in other properties. The trends observed exhibit differences when compared with a conventional univariate sensitivity analysis in which only a single property is varied whereas all other parameters of interest are kept constant.

Detection of cervical intraepithelial neoplasias and cancers in cervical tissue by in vivo light scattering

OBJECTIVE: To examine the utility of in vivo elastic light scattering measurements to identify cervical intraepithelial neoplasias (CIN) 2/3 and cancers in women undergoing colposcopy and to determine the effects of patient characteristics such as menstrual status on the elastic light scattering spectroscopic measurements. MATERIALS AND METHODS: A fiber optic probe was used to measure light transport in the cervical epithelium of patients undergoing colposcopy. Spectroscopic results from 151 patients were compared with histopathology of the measured and biopsied sites. A method of classifying the measured sites into two clinically relevant categories was developed and tested using five-fold cross-validation. RESULTS: Statistically significant effects by age at diagnosis, menopausal status, timing of the menstrual cycle, and oral contraceptive use were identified, and adjustments based upon these measurements were incorporated in the classification algorithm. A sensitivity of 77±5% and a specificity of 62±2% were obtained for separating CIN 2/3 and cancer from other pathologies and normal tissue. CONCLUSIONS: The effects of both menstrual status and age should be taken into account in the algorithm for classifying tissue sites based on elastic light scattering spectroscopy. When this is done, elastic light scattering spectroscopy shows good potential for real-time diagnosis of cervical tissue at colposcopy. Guiding biopsy location is one potential near-term clinical application area, while facilitating "see and treat" protocols is a longer term goal. Improvements in accuracy are essential.

Effect of anatomy on spectroscopic detection of cervical dysplasia

It has long been speculated that underlying variations in tissue anatomy affect in vivo spectroscopic measurements. We investigate the effects of cervical anatomy on reflectance and fluorescence spectroscopy to guide the development of a diagnostic algorithm for identifying high-grade squamous intraepithelial lesions (HSILs) free of the confounding effects of anatomy. We use spectroscopy in both contact probe and imaging modes to study patients undergoing either colposcopy or treatment for HSIL. Physical models of light propagation in tissue are used to extract parameters related to tissue morphology and biochemistry. Our results show that the transformation zone, the area in which the vast majority of HSILs are found, is spectroscopically distinct from the adjacent squamous mucosa, and that these anatomical differences can directly influence spectroscopic diagnostic parameters. Specifically, we demonstrate that performance of diagnostic algorithms for identifying HSILs is artificially enhanced when clinically normal squamous sites are included in the statistical analysis of the spectroscopic data. We conclude that underlying differences in tissue anatomy can have a confounding effect on diagnostic spectroscopic parameters and that the common practice of including clinically normal squamous sites in cervical spectroscopy results in artificially improved performance in distinguishing HSILs from clinically suspicious non-HSILs.

Quantitative physiology of the precancerous cervix in vivo through optical spectroscopy

Cervical cancer is the second most common female cancer worldwide. The ability to quantify physiological and morphological changes in the cervix is not only useful in the diagnosis of cervical precancers but also important in aiding the design of cost-effective detection systems for use in developing countries that lack well-established screening and diagnostic programs. We assessed the capability of a diffuse reflectance spectroscopy technique to identify contrasts in optical biomarkers that vary with different grades of cervical intraepithelial neoplasia (CIN) from normal cervical tissues. The technology consists of an optical probe and an instrument (with broadband light source, dispersive element, and detector), and a Monte Carlo algorithm to extract optical biomarker contributions including total hemoglobin (Hb) concentration, Hb saturation, and reduced scattering coefficient from the measured spectra. Among 38 patients and 89 sites examined, 46 squamous normal sites, 18 CIN 1, and 15 CIN 2(+) sites were included in the analysis. Total Hb was statistically higher in CIN 2(+) (18.3 +/- 3.6 microM, mean +/- SE) compared with normal (9.58 +/- 1.91 microM) and CIN 1 (12.8 +/- 2.6 microM), whereas scattering was significantly reduced in CIN 1 (8.3 +/- 0.8 cm(-1)) and CIN 2(+) (8.6 +/- 1.0 cm(-1)) compared with normal (10.2 +/- 1.1 cm(-1)). Hemoglobin saturation was not significantly altered in CIN 2(+) compared with normal and CIN 1. The difference in total Hb is likely because of stromal angiogenesis, whereas decreased scattering can be attributed to breakdown of collagen network in the cervical stroma.

Automated identification of tumor microscopic morphology based on macroscopically measured scatter signatures

An automated algorithm and methodology is presented to identify tumor-tissue morphologies based on broadband scatter data measured by raster scan imaging of the samples. A quasi-confocal reflectance imaging system was used to directly measure the tissue scatter reflectance in situ, and the spectrum was used to identify the scattering power, amplitude, and total wavelength-integrated intensity. Pancreatic tumor and normal samples were characterized using the instrument, and subtle changes in the scatter signal were encountered within regions of each sample. Discrimination between normal versus tumor tissue was readily performed using a K-nearest neighbor classifier algorithm. A similar approach worked for regions of tumor morphology when statistical preprocessing of the scattering parameters was included to create additional data features. This type of automated interpretation methodology can provide a tool for guiding surgical resection in areas where microscopy imaging cannot be realized efficiently by the surgeon. In addition, the results indicate important design changes for future systems.

In vivo light scattering for the detection of cancerous and precancerous lesions of the cervix

A noninvasive optical diagnostic system for detection of cancerous and precancerous lesions of the cervix was evaluated in vivo. The optical system included a fiber-optic probe designed to measure polarized and unpolarized light transport properties of a small volume of tissue. An algorithm for diagnosing tissue based on the optical measurements was developed that used four optical properties, three of which were related to light scattering properties and the fourth of which was related to hemoglobin concentration. A sensitivity of ~77% and specificities in the mid 60% range were obtained for separating high grade squamous intraepithelial lesions and cancer from other pathologies and normal tissue. The use of different cross-validation methods in algorithm development is analyzed, and the relative difficulties of diagnosing certain pathologies are assessed. Furthermore, the robustness of the optical system for use by different doctors and to changes in fiber-optic probe are also assessed, and potential improvements in the optical system are discussed.

Advances in quantitative UV-visible spectroscopy for clinical and pre-clinical application in cancer

Methods of optical spectroscopy that provide quantitative, physically or physiologically meaningful measures of tissue properties are an attractive tool for the study, diagnosis, prognosis, and treatment of various cancers. Recent development of methodologies to convert measured reflectance and fluorescence spectra from tissue to cancer-relevant parameters such as vascular volume, oxygenation, extracellular matrix extent, metabolic redox states, and cellular proliferation have significantly advanced the field of tissue optical spectroscopy. The number of publications reporting quantitative tissue spectroscopy results in the UV-visible wavelength range has increased sharply in the past three years, and includes new and emerging studies that correlate optically measured parameters with independent measures such as immunohistochemistry, which should aid in increased clinical acceptance of these technologies.

Quantitative imaging of scattering changes associated with epithelial proliferation, necrosis, and fibrosis in tumors using microsampling reflectance spectroscopy

Highly localized reflectance measurements can be used to directly quantify scatter changes in tissues. We present a microsampling approach that is used to raster scan tumors to extract parameters believed to be related to the tissue ultrastructure. A confocal reflectance imager was developed to examine scatter changes across pathologically distinct regions within tumor tissues. Tissue sections from two murine tumors, AsPC-1 pancreas tumor and the Mat-LyLu Dunning prostate tumor, were imaged. After imaging, histopathology-guided region-of-interest studies of the images allowed analysis of the variations in scattering resulting from differences in tissue ultra-structure. On average, the median scatter power of tumor cells with high proliferation index (HPI) was about 26% less compared to tumor cells with low proliferation index (LPI). Necrosis exhibited the lowest scatter power signature across all the tissue types considered, with about 55% lower median scatter power than LPI tumor cells. Additionally, the level and maturity of the tumor's fibroplastic response was found to influence the scatter signal. This approach to scatter visualization of tissue ultrastructure in situ could provide a unique tool for guiding surgical resection, but this kind of interpretation into what the signal means relative to the pathology is required before proceeding to clinical studies.

Optical imaging for cervical cancer detection: solutions for a continuing global problem

Cervical cancer is the leading cause of cancer death for women in developing countries. Optical technologies can improve the accuracy and availability of cervical cancer screening. For example, battery-powered digital cameras can obtain multi-spectral images of the entire cervix, highlighting suspicious areas, and high-resolution optical technologies can further interrogate such areas, providing in vivo diagnosis with high sensitivity and specificity. In addition, targeted contrast agents can highlight changes in biomarkers of cervical neoplasia. Such advances should provide a much needed global approach to cervical cancer prevention.

Combined Monte Carlo and finite-difference time-domain modeling for biophotonic analysis: implications on reflectance-based diagnosis of epithelial precancer

Monte Carlo (MC) modeling of photon transport in tissues is generally performed using simplified functions that only approximate the angular scattering properties of tissue constituents. However, such approximations may not be sufficient for fully characterizing tissue scatterers such as cells. Finite-difference time-domain (FDTD) modeling provides a flexible approach to compute realistic tissue phase functions that describe probability of scattering at different angles. We describe a computational framework that combines MC and FDTD modeling, and allows random sampling of scattering directions from FDTD phase functions. We carry out simulations to assess the influence of incorporating realistic FDTD phase functions on modeling spectroscopic reflectance signals obtained from normal and precancerous epithelial tissues. Simulations employ various fiber optic probe designs to analyze the sensitivity of different probe geometries to FDTD-generated phase functions. Combined MC/FDTD modeling results indicate that the form of the phase function used is an important factor in determining the reflectance profile of tissues, and detected reflectance intensity can change up to approximately 30% when a realistic FDTD phase function is used instead of an approximating function. The results presented need to be taken into account when developing photon propagation models or implementing inverse algorithms to extract optical properties from measurements.

The clinical effectiveness of optical spectroscopy for the in vivo diagnosis of cervical intraepithelial neoplasia: where are we?

OBJECTIVE

In this review, we evaluate the diagnostic efficacy of optical spectroscopy technologies (fluorescence and reflectance spectroscopy) for the in vivo diagnosis of cervical neoplasia using both point probe and multispectral imaging approaches.

METHODS

We searched electronic databases using the following terms: cervical cancer, cervical intraepithelial neoplasia, squamous intraepithelial lesion, and spectroscopy, fluorescence spectroscopy, or reflectance spectroscopy. We included studies that evaluated fluorescence and reflectance spectroscopy devices for in vivo diagnosis, compared those results with biopsy results, and reported on the sensitivity and specificity of the devices tested.

RESULTS

Twenty-six studies, including seven phase II trials and one randomized clinical trial, met our acceptability criteria. We found several important differences across the studies including device approach (multispectral versus point probe), study population, disease classification system, and disease threshold. This heterogeneity prevented formal combination of sensitivity and specificity results.

CONCLUSION

Optical spectroscopy has similar performance to colposcopy and may help localize lesions and therefore be an effective adjunct to colposcopy. Reports on the diagnostic accuracy of these devices should use common thresholds for the construction of receiver operating characteristic curves to enable comparisons with standard technologies and facilitate their adoption. Optical spectroscopy has also been identified for possible use as ASCUS triage and primary screening, yet neither has been sufficiently evaluated to warrant a conclusion as to their suitability in this role.

The clinical effectiveness of fluorescence and reflectance spectroscopy for the in vivo diagnosis of cervical neoplasia: An analysis by phase of trial design

OBJECTIVE

In this review, we focus on the pilot, Phase I, II, and III clinical trials of fluorescence spectroscopy, reflectance spectroscopy, and their combination for the in vivo diagnosis of cervical neoplasia using both point probe and multi-spectral imaging approaches. Research groups that have progressed from pilot through Phase II/III clinical trials were analyzed.

METHODS

A formal search was conducted to identify articles which report the performance of fluorescence and reflectance spectroscopy trials which diagnose cervical neoplasia in vivo. This report focuses on the funding source, prevalence of disease in the trials, type of population (screening versus diagnostic), gold standard criterion for diagnosis (histopathology versus colposcopy alone and histopathology), histopathologic classification (World Health Organization (WHO) 8 categories, Bethesda 5 categories, or both (13 categories)), number of clinical trial sites, number of medical investigators, number of histopathology reviews by histopathologists for a consensus diagnosis, use of acetic acid, explicit sample size calculation in the published report, actual sample size in the trial, ages of patients included in the trial, and the phase of the trial design, as they affect performance and plotted as sensitivity and 1-specificity.

RESULTS

Twenty-six studies were included and their heterogeneity precluded formal meta-analytic combination. While most factors inherent in the review were not significant sources of variability; there were three variables that affected performance, i.e., sample size, age of patients, and phase of trial design.

DISCUSSION

As with pharmaceutical trials, as the sample size increased, as the heterogeneity of the population increased, as the age of the patients included patients over 50 years old, and as the phase of clinical trial design progressed from pilot through Phase III randomized trial, the performance of all devices decreased.

The performance of fluorescence and reflectance spectroscopy for the in vivo diagnosis of cervical neoplasia; point probe versus multispectral approaches

OBJECTIVE

This review evaluates the diagnostic efficacy of fluorescence spectroscopy, reflectance spectroscopy, and their combination that use both point probe and multispectral imaging approaches in diagnosing cervical neoplasia in vivo.

METHODS

Articles were selected for this review from a literature search which report the performance of fluorescence and reflectance spectroscopy devices in diagnosing cervical neoplasia in vivo. This analysis focused on the comparison of point probe versus multispectral approaches; the use of fluorescence, reflectance, and their combination; and finally the types of populations that have been studied for in vivo diagnosis of squamous intraepithelial lesions (SIL).

RESULTS

Twenty-six studies were included and their heterogeneity precluded formal meta-analysis. Though point probes were expected to have greater specificity and multispectral approaches greater sensitivity, there was considerable overlap in the performance of point probe and multispectral devices. There were few studies that studied fluorescence spectroscopy alone and reflectance spectroscopy alone. Combined fluorescence and reflectance approaches showed considerable overlap among point probe and multispectral devices. The overlap of performance suggests that fluorescence and reflectance may have similar performance. Currently the paucity of data precludes definitive conclusions regarding the additive effect of both approaches. Only two of twenty-six trials have recruited patients with no history of an abnormal Papanicolaou smear (screening populations) and twenty-four trials include patients with a range of cervical abnormalities from atypia to cancer (diagnostic populations).

DISCUSSION

Optical spectroscopy using a point probe and multispectral approaches appears to overlap in performance. Fluorescence and reflectance spectroscopies examine different aspects of epithelial-stromal biology and appear to yield similar diagnostic performance. While intuitively appealing, their combination may or may not be additive. There have been few studies of these technologies in screening populations. Better definitions of device trial design and reporting requirements would facilitate combining analyses to formally examine performance.