Optical treatment of pathological tissues comprises techniques like Low Intensity Laser Treatment (LILT) or Photodynamic Therapy (PDT). PDT consists on the inoculation of a photosensitizer in the tissue, which tends to be accumulated in cancerous cells, and on the posterior optical radiation of the area. The photosensitizer, that can be topical or systemic, is excited and cell necrosis is provoked. The collateral harmful effects of other destructive techniques, like radiotherapy or chemotherapy, are avoided with PDT. PDT can also be used as a complementary technique of conventional excisional surgical operations. The application of PDT to skin disorders is straightforward due to the fact that it is an external and accessible tissue. In this work, we analyze the application of PDT to several skin pathologies and the results obtained, by means of mainly the usage of Metvix® as a topical photosensitizer and with an optical source in the range of 635 nm. The analysis includes a predictive model of the PDT process, based on an optical propagation equation and a photosensitizer degradation approach that provides an estimation of tissue destruction.

The applications of nanoparticles in optical techniques of diagnosis and treatment of biological tissues are increasing. Image contrast can be improved in diagnostic approaches such as fluorescence, spectroscopy or optical coherence tomography. The therapeutic effect can be increased if nanoparticles are previously incorporated in the biological tissue. This is the case in thermotherapy, or in Photodynamic Therapy. All these applications take advantage of specific properties of the nanoparticles involved, either optical up-or down-conversion, thermal confinement or the ability to act as a drug-carrier.Although many biomedical applications that involve nanoparticles are being proposed and tested, there is a need to take into account the influence of those nanoparticles on optical radiation propagation. The previously mentioned optical treatment and diagnosis techniques assume a particular optical propagation pattern, which is altered by the addition of nanoparticles. This change depends on the nanoparticle material, shape, size and concentration, among other parameters. In order to try to quantify these changes, in this work several phantoms that include different nanoparticles are analyzed, in order to estimate the influence of nanoparticles in optical propagation. A theoretical model of optical propagation, which takes into account the absorption and scattering changes in the medium, is also considered. Nanoparticles of different sizes from 40 nm to 1 µm are analyzed. Nanoparticle materials of interest in biomedical applications are employed. The results are relevant in diagnosis interpretation of images and treatment outcome evaluation when nanoparticles are present.

Digital Image Plane Holography (DIPH) is a non-invasive optical technique which is able to recover the whole object wave. An object is illuminated and the diffused backscattered light is carried to a digital sensor by using a lens, where it interferes with a divergent reference wave with its origin in the lens aperture plane. Selecting each aperture image in the Fourier plane, the amplitude and the phase of the object beam are obtained. If two holograms are recorded at different times, after a small displacement, the reconstructed intensity distributions can be taken as a speckle field, while the phase difference distribution can be analyzed by an interferometric approach. In this work scattering media are investigated by using digital holography. The aim of this paper is to determine the viability of the technique to characterized optical properties of the sample. Different scattering media are modeled with different scattering properties. Each model generates a speckle pattern with different statistical properties (size, contrast, intensity). Both the visibility of the interferometric fringes and the properties of speckle pattern are related with optical properties of the media such as absorption and scattering coefficient. The ability to measure these properties makes the technique a promising method for biomedical applications.

Photodynamic Therapy is a selective optical tumor destruction technique with practically no secondary effects. Monitoring by fluorescence photosensitizer emission is essential for an adequate treatment dosimetry, which avoids recurrence.