S. Stolik

In vivo assessment of liver fibrosis using diffuse reflectance and fluorescence spectroscopy: A proof of concept

A novel application of diffuse reflectance and fluorescence spectroscopy in the assessment of liver fibrosis is here reported. To induce different stages of liver fibrosis, a sufficient number of male Wistar rats were differentially exposed to chronic administration with carbon tetrachloride. Then, diffuse reflectance and fluorescence spectra were in vivo measured from the liver surface of each animal by a minimal invasive laparoscopic procedure. The liver fibrosis degree was conventionally determined by means of histological examination using the Masons Trichrome stain, accompanied by hepatic expression of α-sma, and evaluation of the ALT/AST serum levels. The liver from rats exhibiting higher grades of fibrosis showed a significant increase in diffuse reflectance and fluorescence intensity when compared with control animals. At 365 nm, the diffuse reflectance spectrum exhibited an increase of 4 and 3-fold in mild and advanced fibrotic rats, respectively, when compared to the control group. Similarly, the fluorescence emission at 493 nm was 2-fold higher in fibrotic animals than in controls. By using fluorescence intensity, discrimination algorithms indicated 73% sensitivity and 94% specificity for recognition of hepatic fibrosis, while for diffuse reflectance, these values increased up to 85% and 100%, respectively. Taking into consideration there is a special need for developing new diagnostic approaches focused on detecting different stages of liver fibrosis with minimal invasiveness, these results suggest that diffuse reflectance and fluorescence spectroscopy could be worthy of further exploration in patients with liver disease.

Detection of Counterfeit Tequila by Fluorescence Spectroscopy

An ultraviolet (UV) light induced fluorescence study to discriminate fake tequila from genuine ones is presented. A portable homemade system based on four light emitting diodes (LEDs) from 255 to 405 nm and a miniature spectrometer was used. It has been shown that unlike fake and silver tequila, which produce weak fluorescence signal, genuine mixed, rested, and aged tequilas show high fluorescence emission in the range from 400 to 750 nm. The fluorescence intensity grows with aging in 100% agave tequila. Such fluorescence differences can even be observed with naked eyes. The presented results demonstrate that the fluorescence measurement could be a good method to detect counterfeit tequila.

Development of a phototherapy system with a pulse oximetry module as an element for tissue oxygen measurement

Photodynamic therapy is a type of phototherapy that involves the administration of a photosensitizer drug followed by a local illumination with light of specific wavelength. In the presence of oxygen molecules, the light illumination of photosensitizer can activate the production of reactive oxygen species which yield the death of target cells. In order to obtain the best therapy response, it can be measured the oxygen tissue concentration to adjust the initial parameters of the treatment. In this work it is presented an irradiation system which allows the application of radiation at wavelengths 450, 523, 630 nm using as a light sources, power-controlled light emitting diodes besides a module to measure the tissue oxygen saturation based on pulse oximetry.

Optimization of irradiation patterns using light emitting diodes

Since light emitting diodes have undergone a huge development in the last decades, they are achieving a widespread use in almost every activity substituting older light sources. The properties of the light emitting diodes such as their size, efficiency, wavelength of the emitted radiation, among others, have turn these devices into an increasingly applied solution for different applications. Some applications require a proper design of the illumination patterns. Here, it is presented a design solution for the radiation pattern of the light emitting diode using as the approximation the cone equation. Also, a method to design specific irradiance distributions using a certain number of diodes is discussed.

An irradiation system for photodynamic therapy with a fiber-optic sensor for measuring tissue oxygen

Photodynamic Therapy is a well known treatment based on the interaction of light of specific wavelength with a photosensitizing drug. In the presence of oxygen molecules, the illumination of the photosensitizer can activate the production of reactive oxygen species, which leads to the death of target cells within the treated tissue. In order to obtain the best therapy response, the tissue oxygen concentration should be measured to adjust the therapy parameters before and during the treatment. In this work, an irradiation system for 5−Aminolevulinic Acid Photodynamic Therapy is presented. It allows the application of visible light radiation of 630 nm using as a light source a high-brightness light emitting diode with an optical-power automatic control considering a light depth-distribution model. A module to measure the tissue oxygen saturation has been implemented into the system. It is based on two light emitting diodes of 660 nm and 940 nm as light sources, a photodiode as a detector and a new handheld fiber optic reflectance pulse oximetry sensor for estimating the blood oxygen saturation within the tissue. The pulse oximetry sensor was modeled through multilayered Monte Carlo simulations to study the behavior of the sensor with changes in skin thickness and melanin content.

Optical spectroscopy for differentiation of liver tissue under distinct stages of fibrosis: an ex vivo study

Liver fibrosis is the decisive step towards the development of cirrhosis; its early detection affects crucially the diagnosis of liver disease, its prognosis and therapeutic decision making. Nowadays, several techniques are employed to this task. However, they have the limitation in estimating different stages of the pathology. In this paper we present a preliminary study to evaluate if optical spectroscopy can be employed as an auxiliary tool of diagnosis of biopsies of human liver tissue to differentiate the fibrosis stages. Ex vivo fluorescence and diffuse reflectance spectra were acquired from biopsies using a portable fiber-optic system. Empirical discrimination algorithms based on fluorescence intensity ratio at 500 nm and 680 nm as well as diffuse reflectance intensity at 650 nm were developed. Sensitivity and specificity of around 80% and 85% were respectively achieved. The obtained results show that combined use of fluorescence and diffuse reflectance spectroscopy could represent a novel and useful tool in the early evaluation of liver fibrosis.

Irradiation system for interstitial photodynamic therapy

Interstitial Photodynamic Therapy (IPDT) is a promising form of treatment of deep-seated and bulky malignant tumors, based on the lethal cell response to the photochemical reactions when drug is light activated in presence of oxygen. In order to accomplish an effective internal illumination, laser sources are preferably used because of two important reasons: the monochromatic light can be confined to the narrow absorption band of the drug and the laser beam is easily focused into optical fibers. In this work the development of a diode-laser-light-source is presented. The system is tuned by temperature to get a better match in the 5-ALA absorption band. This system also comprises a trifurcated fiber system to accomplish interstitial illumination.

A diffuse reflectance spectroscopy system to study biological tissues

Diffuse reflectance spectroscopy (DRS) is a technique that allows the study of the structural and biochemical condition of tissues in a noninvasive-nonionizing way. DRS has been widely used in biomedical applications, mainly as an alternative to biopsy. Generally, the technique consists in the irradiation of a specific zone of a tissue with a reference spectrum. Then, the reemitted by the tissue light is detected. The changes suffered by the backscattered spectrum (after light-tissue interaction) with respect to the incident one carry information about the tissue properties. This work presents a novel system designed and developed to use DRS in biomedical applications. The system uses a LED as a light source and a specially designed optical fiber probe as a mean to deliver the light to the tissue surface, and to collect the reemitted photons from the studied sample. This probe was designed to accomplish two different tasks: to increase the sensitivity of the diagnosis; and to study the radial dependence of the backscattered light. The measuring probe was built in a way that allows taking readings when the exerted pressure on the tissue reaches certain predetermined values.

Experimental tests in tissue phantoms of a photoirradiation system with optical dosimetry for photodynamic therapy

Photodynamic therapy involves the administration of a photosensitizer drug followed by a local illumination with light of specific wavelength. In the presence of oxygen molecules, the light illumination of photosensitizer can activate the production of reactive oxygen species which produce the death of malignant cells. Light dose is an important factor for reach an effective therapy. In this work it is presented an irradiation system which allows the application of radiation at 630 nm for 5-AminoLevulinic Acid superficial Photodynamic Therapy using as a light source, a light emitting diode and an automatic control of output optical power using the results of a model of distribution of radiation in depth for different optical properties. The system was tested in tissue phantoms which allow a more controlled environment than test in vivo or in vitro.

Development of an irradiation system for photodynamic therapy with dosimetric control

Photodynamic therapy is a well know treatment based on the interaction of light with a photosensitizer drug and oxygen. It has been used for the treatment of certain diseases, especially cancer. One of the major problems in the implementation of the therapy is the use of lasers as light sources which increases the cost of the therapy. This is why we propose the development of photodynamic therapy irradiation system which allows the application of optical radiation at 630 nm for Protophorphyrin-IX therapy, using cheaper light sources as high power light emission diodes. Additionally, it is proposed an automatic control of power and time for the irradiation to ensure the stability of the system and also the future inclusion of an algorithm to determine the required optical dosimetry in depth to get optimal therapeutic effects.