Optical properties measurements in scattering media by Time-Correlated Single-Photon-Counting System (TCSPCS)

摘要

Time-Correlated Single-Photon-Counting (TCSPC) systems have been often adopted to prepare more compact and less expensive instruments for medical imaging. Then it is important to investigate in detail the performances of each imaging system in measuring the optical properties of turbid media. Our experimental apparatus is composed by an Hamamatsu PLP02 pulsed diode laser at 824 nm with 1Mhz repetition rate and a pulse duration of 40 ps. The signal has been collected from the investigated sample by means of fiber bundles and has been analyzed by an Edinburgh Instrument TCSPCS equipped with a 8 channels Hamamatsu multichannel plate R4110U-F008 and an SPC300 acquisition module. Solutions of distilled water and commercial Intralipid 10% at different concentrations have been investigated. To obtain optical parameters, the experimental data have been fitted with an analytic solution to the diffusion equation. Also the convolution effect of the measured Temporal Point Spread Functions (TPSF) by the Impulse Response Function (IRF) of the system has been investigated. A linear trend has been obtained for the reduced scattering coefficient μ'_s with concentration in solution of the scattering agent (Intralipid 10%) and an agreement within few percent has been reported with Mie theory predictions. The results here obtained confirm that all the details in fitting and convolution procedures become particularly important when slight difference in absorption and scattering coefficients have to be examined.