Usually, tissue images at cellular level need biopsies to be done. Considering this, diagnostic devices, such as microendoscopes, have been developed with the purpose of do not be invasive. This study goal is the development of a dual-channel microendoscope, using two fluorescent labels: proflavine and protoporphyrin IX (PpIX), both approved by Food and Drug Administration. This system, with the potential to perform a microscopic diagnosis and to monitor a photodynamic therapy (PDT) session, uses a halogen lamp and an image fiber bundle to perform subcellular image. Proflavine fluorescence indicates the nuclei of the cell, which is the reference for PpIX localization on image tissue. Preliminary results indicate the efficacy of this optical technique to detect abnormal tissues and to improve the PDT dosimetry. This was the first time, up to our knowledge, that PpIX fluorescence was microscopically observed in vivo, in real time, combined to other fluorescent marker (Proflavine), which allowed to simultaneously observe the spatial localization of the PpIX in the mucosal tissue. We believe this system is very promising tool to monitor PDT in mucosa as it happens. Further experiments have to be performed in order to validate the system for PDT monitoring.
Phototherapies have been increasingly used in several applications such as the control of pain and inflammatory processes, photodynamic therapy, and even aesthetics uses. After many decades, the dosimetry for those techniques remains challenging. One of the key issues is the lack of homogeneity obtained for tissue illumination, which may limit adequate treatment. Especially concerning lesions, the surface tissue is usually irregular, and the light does not couple to the tissue efficiently to promote an effective treatment. A series of experiments have been performed using optical phantoms, in which coupling was improved by introducing a gel with a low concentration of scattering agents between the fiber and the phantom as an attempt to improve the homogeneity of light distribution within the phantoms. The effects promoted by roughness on phantom tissue surfaces are considerably attenuated when the coupling gel was introduced, resulting in a more uniform illumination pattern that may be used to promote better phototherapy treatments outcome.
Both for therapeutic and diagnosis purposes, light dosimetry is generally based on empirical data reported in the literature. It is known that tissue color, hydration and surface roughness influences the light propagation. In this context, it is important to investigate ways to minimize these effects leading to an enhanced phototherapy or photodiagnosis application. This study aims to evaluate how different coupling agents alter the light distribution at the light-phantom interface. Diffuse reflectance measurements were performed in order to compare the light interaction with the phantom with and without the coupling agents.
Photodynamic therapy (PDT) is a technique used for several tumor types treatment. Light penetration on biological tissue
is one limiting factor for PDT applied to large tumors. An alternative is using interstitial PDT, in which optical fibers are
inserted into tumors. Cylindrical diffusers have been used in interstitial PDT. Light emission of different diffusers depends
on the manufacturing process, size and optical properties of fibers, which make difficult to establish an adequate light
dosimetry, since usually light profile is not designed for direct tissue-fiber contact. This study discusses the relevance of
light distribution by a cylindrical diffuser into a turbid lipid emulsion solution, and how parts of a single diffuser contribute
to illumination. A 2 cm-long cylindrical diffuser optical fiber was connected to a diode laser (630 nm), and the light spatial
distribution was measured by scanning the solution with a collection probe. From the light field profile generated by a 1
mm-long intermediary element of a 20 mm-long cylindrical diffuser, recovery of light distribution for the entire diffuser
was obtained. PDT was performed in rat healthy liver for a real treatment outcome analysis. By using computational tools,
a typical necrosis profile generated by the irradiation with such a diffuser fiber was reconstructed. The results showed that
it was possible predicting theoretically the shape of a necrosis profile in a healthy, homogeneous tissue with reasonable
accuracy. The ability to predict the necrosis profile obtained from an interstitial illumination by optical diffusers has the
potential improve light dosimetry for interstitial PDT.
Optical techniques has been described as auxiliary technology for screening of neoplasia because shows the potential for tissues differentiation in real-time and it is a noninvasive detection and safe. However, only endogenous fluorophores presents the lesion may be insufficient and needed of the administration of the fluorophores synthesized, such as, precursor molecule of protoporphyrin IX (PpIX) induced by 5- aminolevulinic acid and your derivatives. Topical application of methylaminolevulinate (MAL), induces formation of the endogenous photosensitizer, PpIX in tissues where carcinogenesis has begun. The PpIX tend to accumulate in premalignant and malignant tissues and the illumination with light with appropriate wavelength beginning to excitation of PpIX fluorescence, which helps to localize PpIX-rich areas and identify potentially malignant tissues. The aim of the study is to evaluate the production of PpIX in the cervix with CIN I through of the fluorescence images captured after 1 hour of cream application. It was possible to visualize PpIX fluorescence in cervix and it was possible to observe the selectivity in fluorescence in squamous-columnar junction, which a pre-cancerous condition (CIN) and usually is localized. Through the image processing it was possible to quantify the increase of red fluorescence. For the CIN I the increase of red fluorescence was approximately of 4 times indicating a good PpIX formation.
Onychomycosis is a common disease of the nail plate, constituting approximately half of all cases of nail infection. Onychomycosis diagnosis is challenging because it is hard to distinguish from other diseases of the nail lamina such as psoriasis, lichen ruber or eczematous nails. The existing methods of diagnostics so far consist of clinical and laboratory analysis, such as: Direct Mycological examination and culture, PCR and histopathology with PAS staining. However, they all share certain disadvantages in terms of sensitivity and specificity, time delay, or cost.
This study aimed to evaluate the use of infrared and fluorescence imaging as new non-invasive diagnostic tools in patients with suspected onychomycosis, and compare them with established techniques.
For fluorescence analysis, a Clinical Evince (MM Optics®) was used, which consists of an optical assembly with UV LED light source wavelength 400 nm ± 10 nm and the maximum light intensity: 40 mW/cm2 ± 20%. For infrared analysis, a Fluke® Camera FKL model Ti400 was used. Patients with onychomycosis and control group were analyzed for comparison. The fluorescence images were processed using MATLAB® routines, and infrared images were analyzed using the SmartView® 3.6 software analysis provided by the company Fluke®.
The results demonstrated that both infrared and fluorescence could be complementary to diagnose different types of onychomycosis lesions. The simplicity of operation, quick response and non-invasive assessment of the nail patients in real time, are important factors to be consider for an implementation.
The use of light as a therapeutic agent has been the subject of several studies; however, the dosimetry for its clinical application is still based on empirical data. The propagation of light in biological tissues depends on the tissue optical properties, and these properties may vary among people, tissues and sites, making it diffcult to establish dosimetry. In this context, the research for methods to determine the spatial distribution of light in individual biological tissues becomes essential, allowing the individual dosimetry. This study aims to image the diffuse reflectance at the optical phantom surface to infer the spatial distribution of light inside a phantom when an absorbing obstacle is present. Red laser were used as light source on solid turbid optical phantom; a small black sphere was used as absorbing obstacle. It is important to know, in real time and in a non-invasive way, about the existence of heterogeneities that may compromise the light propagation inside a biological tissue, so that the light dosimetry might be properly established.