Photoacoustic field calculation for nonspherical axisymmetric fluid particles

Abstract

The photoacoustic (PA) field calculation using a Green's function approach for nonspherical axisymmetric fluid particles is discussed. The PA fields have been computed for spheroidal droplets, Chebyshev particles and normal and pathological red blood cells (RBCs) over a large frequency band (10–1000 MHz). Theoretically constructed RBC contours have been fitted using the Legendre polynomial expansion for parametrization of cell shapes. It is shown that first minimum of the PA spectrum appears at a lower frequency as the width of the particle along the direction of measurement increases. The spectra for higher order (n = 6, 8) Chebyshev particles resembled that of an equivalent sphere up to first minimum. The first minimum for a stomatocyte appeared (420 MHz) much earlier compared to that (640 MHz) of normal RBC when measured along the direction of the symmetry axis; whereas the locations were 310 and 240 MHz, respectively from a perpendicular direction. The evaluation of cellular morphology might be feasible by analyzing the single particle PA spectrum.