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Photoacoustic Doppler (PAD) power spectra showing an evident Doppler shift represent the major characteristics of the continuous wave-excited or burst wave-excited versions of PAD flow measurements. In this paper, the flow angle dependences of the PAD power spectra are investigated using an experiment setup that was established based on intensity-modulated continuous wave laser excitation. The setup has an overall configuration that is similar to a previously reported configuration, but is more sophisticated in that it accurately aligns the laser illumination with the ultrasound detection process, and in that it picks up the correct sample position. In the analysis of the power spectra data, we find that the background power spectra can be extracted by combining the output signals from the two channels of the lock-in amplifier, which is very useful for identification of the PAD power spectra. The power spectra are presented and analyzed in opposite flow directions, at different flow speeds, and at different flow angles. The power spectra at a 90° flow angle show the unique properties of symmetrical shapes due to PAD broadening. For the other flow angles, the smoothed power spectra clearly show a flow angle cosine relationship.

To study the risk of retinal thermal injury from 532 nm laser during photodynamic therapy (PDT) for choroidal neovascularization (CNV) by measuring the retinal temperat ure increase of rabbit eyes. A microthermocouple technique was developed to measure retinal temperature increase du ring PDT in pigmented and non-pigmented rabbit eyes. The 532 nm laser exposures were performed with 100-s duration, 2-mm spot size, and retinal irradiance ranging from 400 to 1600 mW/cm 2 . A K-type microthermocouple was inserted through the sclerotomy and advanced until the tip reached the retina at the posterior pole. The thermocouple was connected a computer that recorded and analyzed retinal temperature data. The results showed that the retinal temperature increase during laser exposure was proportional to retinal irradiance with a particular spot diameter, exposure duration, wavelength, and fundus pigmentation. And the measured retinal temperature increases in pigmented rabbits were a little higher than those in albino rabbits under the same radiant condition. Retinal threshold irradiance re quired for visible lesions at laser wavelength of 532 nm with 2.0-mm spot size and 100-s duration was 1657 mW/cm

During numerical simulation of laser and tissue thermal interaction, the light fluence rate distribution should be formularized and constituted to the source term in the heat transfer equation. Usually the solution of light irradiative transport equation is given in extreme conditions such as full absorption (Lambert-Beer Law), full scattering (Lubelka-Munk theory), most scattering (Diffusion Approximation) et al. But in specific conditions, these solutions will induce different errors. The usually used Monte Carlo simulation (MCS) is more universal and exact but has difficulty to deal with dynamic parameter and fast simulation. Its area partition pattern has limits when applying FEM (finite element method) to solve the bio-heat transfer partial differential coefficient equation. Laser heat source plots of above methods showed much difference with MCS. In order to solve this problem, through analyzing different optical actions such as reflection, scattering and absorption on the laser induced heat generation in bio-tissue, a new attempt was made out which combined the modified beam broaden model and the diffusion approximation model. First the scattering coefficient was replaced by reduced scattering coefficient in the beam broaden model, which is more reasonable when scattering was treated as anisotropic scattering. Secondly the attenuation coefficient was replaced by effective attenuation coefficient in scattering dominating turbid bio-tissue. The computation results of the modified method were compared with Monte Carlo simulation and showed the model provided reasonable predictions of heat source term distribution than past methods. Such a research is useful for explaining the physical characteristics of heat source in the heat transfer equation, establishing effective photo-thermal model, and providing theory contrast for related laser medicine experiments.

Technology for fluorescence spectral imaging of microscopic has made significant strides advantages in the past several years. These advances have led to the enhanced choice of suitable diagnosis bases. Of course, fluorescence imaging can facilitate the study of disease at the molecular level in vivo. And this type of optical imaging has enabled real-time research to track cell movement, cell growth and other cell functions. With the addition of spectral imaging, fluorescence spectral imaging could complete a so-called 4-dimension imaging for the object. The investigator can obtain either the color imaging information or the information beyond it. The combination of both of them could show the relative completeness message. For evolution of software tools to deal with the resulting high-dimensionality datasets, it is necessary to find some effective and comparative reliable datasets analytical methods. In this paper, it also describes some quantitative fluorescence in tissue and addresses further applications of fluorescence spectral imaging. It includes MSE (Minimum Squared Error), PCA (Principal Components Analysis), ICA (Independent Component Analysis), FEA (Finite-Element Analysis), wavelet theory and their applications. They are useful in intact animals for disease detection, screening, diagnosis, treatment evaluation and drug development.

A portable diffuse correlation spectroscopy (DCS) flowmeter has been extended to measure both tissue blood flow and oxygenation (namely, DCS flow oximeter). For validation purposes, calf muscle blood oxygenation during cuff inflation and deflation was measured concurrently using the DCS flow oximeter and a commercial tissue oximeter. The oxygenation traces from the two measurements exhibited similar dynamic responses, and data were highly correlated (r(mean)0.9, P10(-5), n=10). The portable, inexpensive, and easy-to-use DCS flow oximeter holds promise for bedside monitoring of tissue blood flow and oxygenation in clinics.