Photodynamic therapy (PDT) has become a promising alternative for treatment of skin lesions such as squamous cell carcinoma. We propose a method to monitor the effects of PDT in a noninvasive way by using the optical attenuation coefficient (OAC) calculated from optical coherence tomography (OCT) images. We conducted a study on mice with chemically induced neoplastic lesions and performed PDT on these lesions using homemade photosensitizers. The response of neoplastic lesions to therapy was monitored using, at the same time, macroscopic clinical visualization, histopathological analysis, OCT imaging, and OCT-based attenuation coefficient measurement. Results with all four modalities demonstrated a positive response to treatment. The attenuation coefficient was found to be 1.4 higher in skin lesions than in healthy tissue and it decreased after therapy. This study shows that the OAC is a potential tool to noninvasively assess the evolution of skin neoplastic lesions with time after treatment.
The use of laser for bone cutting can be more advantageous than the use of drill. However, for a safe clinical application,
it is necessary to know the effects of laser irradiation on bone tissues. In this study, the Fourier Transform Infrared
spectroscopy (FTIR) was used to verify the molecular and compositional changes promoted by laser irradiation on bone
tissue. Bone slabs were obtained from rabbit's tibia and analyzed using ATR-FTIR. After the initial analysis, the samples
were irradiated using a pulsed Er,Cr:YSGG laser (2780nm), and analyzed one more time. In order to verify changes due
to laser irradiation, the area under phosphate (1300-900cm<sup>-1</sup>), amides (1680-1200cm<sup>-1</sup>), water (3600-2400cm<sup>-1</sup>), and
carbonate (around 870cm<sup>-1</sup> and between 1600-1300cm<sup>-1</sup>) bands were calculated, and normalized by phosphate band area
(1300-900cm<sup>-1</sup>). It was observed that Er,Cr:YSGG irradiation promoted a significant decrease in the content of water
and amides I and III at irradiated bone, evidencing that laser procedure caused an evaporation of the organic content and
changed the collagen structure, suggesting that these changes may interfere with the healing process. In this way, these
changes should be considered in a clinical application of laser irradiation in surgeries.
Nonlinear microscopy imaging technique enable take both images of collagen fibers in dermis through second harmonic
generation (SHG) signal and elastic fibers by two-photon emission fluorescence microscopy (TPEFM). These techniques
are the most commonly used technique for turbid and thick tissue imaging and also to image biological samples which
presents highly ordered structural proteins without any exogenous label. The objective of this study is characterizing
dermis of third-degree burned skin by TPEFM and SHG technique. The modelocked laser (Spectra Physics) source used
in this study with pulse width of approximately 100 fs at 80 MHz was directed into a multiphoton microscope using a
laser scanning unit (Olympus Fluoview 300), mounted on an inverted confocal system microscope (Olympus IX81), with
focusing objective (40x, NA = 1.30). The samples were obtained from Wistar rats, male, adult. One dorsum area was
submitted to burn caused by vapour exposure. The biopsies obtained were cryosectioned in slices of 20 μm width.
Selected area of interface between the injured and healthy subdermal burned skin were imaged by TPEFM and SHG
technique. Two different autofluorescence signals are observed as a function of excitation wavelength. The
autofluorescence observed at 760 nm and 690 nm suggest components of extracellular matrix at differents depths. In
SHG images, collagen fibers are visible. According to the images obtained, these methodologies can be used to
characterize dermis of burned tissue as its healing process with reduced out-of-plane photobleaching and phototoxicity.