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. The analytical solution to the power spectrum of PA signals generated by identical microspheres following discrete uniform random distribution in space was derived. The power spectrum was decomposed into several independent factors, of which the explicit analytical expressions were individually derived. The analytical expressions in combination allow the quantification of the power spectrum profiles and the PASA parameters. The simulation and experiment validation of analytical solution include: 1) the power spectrum profile of a single microsphere with a diameter of 300 μm; and 2) the PASA parameters of the PA signals generated by randomly distributed microspheres of diameters of 100, 200, 300, 400 and 500 μm, and at concentrations of 30, 60, 120, 240, 480 per 1.53 cubic centimeter in the observation range of [0.5, 13 MHz]. The single microsphere experiment confirmed our hypothesis that the periodical fluctuations of the PA signal power spectrum can be used to quantify the dimension of the microspheres. The multiple microsphere experiment validated that the PASA could quantify the dimensions and concentrations of the optical absorbers. In addition, slope, in comparison with other PASA parameters, is more robust as it is less affected by the uncertainties brought in by the optical illumination. |
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Biological research
Photoacoustic spectroscopy
Signal attenuation
Signal generators
Spherical lenses
Transducers
Calibration
