RESUMO
This work reports the optical properties of porcine pancreatic tissue in the broad wavelength range of 600-1100 nm. Absorption and reduced scattering coefficients (µa and µs') of the ex vivo pancreas were obtained by means of Time-domain Diffuse Optical Spectroscopy. We have investigated different experimental conditions-including compression, repositioning, spatial sampling, temporal stability-the effect of the freezing procedure (fresh vs frozen-thawed pancreas), and finally inter-sample variability. Good repeatability under different experimental conditions was obtained (median coefficient of variation less than 8% and ~ 16% for µa and µs', respectively). Freezing-thawing the samples caused an irreversible threefold reduction of µs' and no effect on µa. The absorption and reduced scattering spectra averaged over different samples were in the range of 0.12-0.74 cm-1 and 12-21 cm-1 with an inter-sample variation of ~ 10% and ~ 40% for µa and µs', respectively. The calculated effective transport coefficient (µeff) for fresh pancreatic tissue shows that regions between 800-900 nm and 1050-1100 nm are similar and offer the lowest tissue attenuation in the considered range (i.e., µeff ranging from 2.4 to 2.7 cm-1). These data, describing specific light-pancreas interactions in the therapeutic optical window for the first time, provide pivotal information for planning of light-based thermotherapies (e.g., laser ablation) and instruction of light transport models for biophotonic applications involving this organ.
Assuntos
Hipertermia Induzida , Fototerapia , Animais , Pâncreas , Espalhamento de Radiação , Análise Espectral/métodos , SuínosRESUMO
Gold nanoparticles (GNPs)-based photothermal therapy (PTT) is a promising minimally invasive thermal therapy for the treatment of focal malignancies. Although GNPs-based PTT has been known for over two decades and GNPs possess unique properties as therapeutic agents, the delivery of a safe and effective therapy is still an open question. This review aims at providing relevant and recent information on the usage of GNPs in combination with the laser to treat cancers, pointing out the practical aspects that bear on the therapy outcome. Emphasis is given to the assessment of the GNPs' properties and the physical mechanisms underlying the laser-induced heat generation in GNPs-loaded tissues. The main techniques available for temperature measurement and the current theoretical simulation approaches predicting the therapeutic outcome are reviewed. Topical challenges in delivering safe thermal dosage are also presented with the aim to discuss the state-of-the-art and the future perspective in the field of GNPs-mediated PTT.
Assuntos
Nanopartículas Metálicas , Neoplasias , Ouro , Humanos , Lasers , Neoplasias/tratamento farmacológico , FototerapiaRESUMO
The increasing recognition of minimally invasive thermal treatment of tumors motivate the development of accurate thermometry approaches for guaranteeing the therapeutic efficacy and safety. Magnetic Resonance Thermometry Imaging (MRTI) is nowadays considered the gold-standard in thermometry for tumor thermal therapy, and assessment of its performances is required for clinical applications. This study evaluates the accuracy of fast MRTI on a synthetic phantom, using dense ultra-short Fiber Bragg Grating (FBG) array, as a reference. Fast MRTI is achieved with a multi-slice gradient-echo echo-planar imaging (GRE-EPI) sequence, allowing monitoring the temperature increase induced with a 980 nm laser source. The temperature distributions measured with 1 mm-spatial resolution with both FBGs and MRTI were compared. The root mean squared error (RMSE) value obtained by comparing temperature profiles showed a maximum error of 1.2 °C. The Bland-Altman analysis revealed a mean of difference of 0.1 °C and limits of agreement 1.5/-1.3 °C. FBG sensors allowed to extensively assess the performances of the GRE-EPI sequence, in addition to the information on the MRTI precision estimated by considering the signal-to-noise ratio of the images (0.4 °C). Overall, the results obtained for the GRE-EPI fully satisfy the accuracy (~2 °C) required for proper temperature monitoring during thermal therapies.