Suren Stolik

Worldwide, breast cancer is the most common type of cancer that mainly affects women. Several diagnosis techniques based on optical instrumentation and image analysis have been developed, and these are commonly used in conjunction with conventional diagnostic devices such as mammographs, ultrasound, and magnetic resonance imaging of the breast. The cost of using these instruments is increasing, and developing countries, whose deaths indices due to breast cancer are high, cannot access conventional diagnostic methods and have even less access to newer techniques. Other studies, based on the analysis of images acquired by traditional methods, require high resolutions and knowledge of the origin of the captures in order to avoid errors. For this reason, the design of a low-cost diffuse optical mammography system for biomedical image processing in breast cancer diagnosis is presented. The system combines the acquisition of breast tissue photographs, diffuse optical reflectance (as a biophotonics technique), and the processing of digital images for the study and diagnosis of breast cancer. The system was developed in the form of a medical examination table with a 638 nm red-light source, using light-emitted diode technology (LED) and a low-cost web camera for the acquisition of breast tissue images. The system is automatic, and its control, through a graphical user interface (GUI), saves costs and allows for the subsequent analysis of images using a digital image-processing algorithm. The results obtained allow for the possibility of planning in vivo measurements. In addition, the acquisition of images every 30° around the breast tissue could be used in future research in order to perform a three-dimensional (3D) reconstruction and an analysis of the captures through deep learning techniques. These could be combined with virtual, augmented, or mixed reality environments to predict the position of tumors, increase the likelihood of a correct medical diagnosis, and develop a training system for specialists. Furthermore, the system allows for the possibility to develop analysis of optical characterization for new phantom studies in breast cancer diagnosis through bioimaging techniques.

Many applications in various fields require uniform illumination from light sources, for example, in medical imaging in the biophotonics area. In this work, the design and application of an annular light-emitting diode array capable of producing a homogeneous irradiance pattern is presented. As part of the design process, software that allows the simulation of the irradiance pattern as a function of the LED’s radiant intensity distribution, and the position and inclination angle of the LEDs, was developed and validated. Based on the simulation results, a source that produces homogeneous illumination over an area of 20 mm in diameter, where the lowest irradiance is more than 94% of the maximum irradiance, was constructed and tested in real conditions. The simulation method and theoretical calculations on which the array is based can be applied to the design of sources for other applications where a homogeneous irradiance is required.

Non-alcoholic fatty liver disease is a highly prevalent condition worldwide that increases the risk to develop liver fibrosis, cirrhosis, and hepatocellular carcinoma. Thus, it is imperative to develop novel diagnostic tools that together with liver biopsy help to differentiate mild and advanced degrees of steatosis. Ex-vivo liver samples were collected from mice fed a methionine-choline deficient diet for two or eight weeks, and from a control group. The degree of hepatic steatosis was histologically evaluated, and fat content was assessed by Oil-Red O staining. On the other hand, fluorescence spectroscopy was used for the assessment of the steatosis progression. Fluorescence spectra were recorded at excitation wavelengths of 330, 365, 385, 405, and 415 nm by establishing surface contact of the fiber optic probe with the liver specimens. A multi-variate statistical approach based on principal component analysis followed by quadratic discriminant analysis was applied to spectral data to obtain classifiers able to distinguish mild and moderate stages of steatosis at the different excitation wavelengths. Receiver Operating Characteristic (ROC) curves were computed to compare classifier’s performances for each one of the five excitation wavelengths and steatosis stages. Optimal sensitivity and specificity were calculated from the corresponding ROC curves using the Youden index. Intensity in the endogenous fluorescence spectra at the given wavelengths progressively increased according to the time of exposure to diet. The area under the curve of the spectra was able to discriminate control liver samples from those with steatosis and differentiate among the time of exposure to the diet for most of the used excitation wavelengths. High specificities and sensitivities were obtained for every case; however, fluorescence spectra obtained by exciting with 405 nm yielded the best results distinguishing between the mentioned classes with a total classification error of 1.5% and optimal sensitivities and specificities better than 98.6% and 99.3%, respectively.

This paper presents the first results of the combination of optical techniques, through fluorescence images captured by endoscopic techniques, and imaging processing methods to give a quantitative result that will be useful to physicians to observing and following up Photodynamic Therapy (PDT) for liver cancer. The experiment was applied to an animal model using δ-aminolevulinic acid (ALA) as a photosensitizing agent, red light for the application of PDT, white light for diffuse reflectance and light of 405 nm for the capture of fluorescence photographs with endoscopic procedures on the surface of the liver. As part of the image processing, metrics such as the Euclidean distance were used and the RGB color composition components.

The Journal of Biomedical Optics (JBO) publishes peer-reviewed papers on the use of novel optical systems and techniques for improved health care and biomedical research.

Background: During the last years, fluorescence spectroscopy has been used as a potential tool for the evaluation and characterization of tissues with different disease conditions due to its low cost, high sensitivity, and minimally or noninvasive character. Objective: In this study, fluorescence spectroscopy was used to study 19 paraffin blocks containing human liver tissue from biopsies. Methods and results: All samples were previously analyzed by two senior pathologists in a single-blind trial. After their evaluation, four liver samples were classified as nonfibrosis (F0), four as initial fibrosis (F1–F2), four as advanced fibrosis (F3), and six as cirrhosis (F4). The fluorescence was induced at different wavelengths as follows: 330, 365, and 405 nm using a portable fiber-optic system. The fluorescence spectra were recorded in the range of 400–750 nm. A distinctive correlation between the shape of each spectrum and the level of fibrosis in the liver sample was detected. A multi-variate statistical analysis based on principal component analysis followed by linear discrimination analysis was applied to develop algorithms able to distinguish different stages of fibrosis based on the characteristics of fluorescence spectra. Pairwise comparisons were performed: F0 versus F1–F2, F1–F2 versus F3, F3 versus F4, and F1–F2 versus F4. The algorithms applied to each set of data yielded values of sensitivity and specificity that were higher than 90% and 95%, respectively, in all the analyzed cases. Conclusions: With this study, it is concluded that fluorescence spectroscopy can be used as a complementary tool for the assessment of liver fibrosis in liver tissue samples, which sets the stage for subsequent clinical trials.

This paper presents the implementation of an endoscopic system with an opto-mechanical revolver for the interchange of five illumination sources for the in vivo diagnostic of abnormalities in liver tissue. Also, the system allows to save images produced by light reflection or autofluorescence. A pedal was implemented to automatically interchange the illumination sources during the endoscopic procedure. Software was developed to save the images captured by the endocamera. Fatty liver images were taken in an animal model which shows the advance of the disease.

There is an increased interest in biophotonic techniques for diagnosis and treatment of diseases and thus the development of new equipment which requires calibration and testing. For this purpose, the development of low cost optical tissue phantoms it is important because it is required a medium for light propagation studies. The absorption, scattering and anisotropy coefficients of a fat emulsion called Intralipid 10% have been measured at seven different wavelengths in the visible range using light-emitting diodes instead of lasers which are more commonly used. It was performed measurements of light fluence in a mixture of Intralipid and black India ink to verify the obtained coefficients. The experimental results were compared and validated against Monte Carlo simulations.

Objective: In this work an irradiance and temperature controlled in-vitro system for conducting investigations in PDT and phototherapy is presented. Background data: The development of new light sources has caused a considerable increase in research and application of several photodynamic (PDT) therapeutic methods, as well as other light-based therapeutic techniques. However, further work is needed to fully understand and elucidate the mechanisms as well as to increase the effectiveness of PDT. Nowadays, there are no commercial systems to perform automated light exposure experiments with cultured cells. Also, there are very few reports of similar photoirradiation systems. Materials and methods: The system is composed of 24 independent light-emitting diodes that can be used to irradiate separate wells in a microwell plate. The system includes a module to measure changes in temperature within each irradiated well without contact. The light sources are placed on a plate that can easily be changed in order to irradiate at different wavelengths. The performance of the system is fully controlled with a computer, and all the experimental data are properly recorded. Results: The design, construction, operation, and a full characterization of the system are presented. Conclusions: A novel fully automated photoirradiation system has been developed. The system allows the design of the experiments in this area with precise dosimetry, temperature, and irradiation regime controls reducing manipulation of the samples and saving time.