Predicting optoacoustic spectral behaviour of human erythrocytes, stomatocytes and echinocytes using a modified Green's function method.

Optoacoustic (OA) spectral properties of various sources mimicking normal and pathological red blood cells (RBCs) have been studied. The shapes of normal RBC and cells suffering from stomatocytosis (denoted by ST) were generated using mathematical models. However, the shape corresponding to the cells affected by echinocytosis (referred to as ET) was constructed by uniformly distributing half prolate spheroids on a central spherical object. The OA field emitted by an acoustically inhomogeneous source was calculated for a wide acoustic frequency bandwidth (1-1500 MHz with an increment 5 MHz) by solving the time-independent wave equation employing a modified Green's function approach. The OA spectra averaged over 200 orientations for normal RBC and STs demonstrate similar features (one minimum occurring nearly at 906 MHz). The same graphs for ETs are remarkably different from that of normal RBC and exhibit better match with that of a spherical RBC (first minimum appearing at around 425 MHz). The spectral features of ETs above 425 MHz may enable us to differentiate diseased cells (echinocytosis) from normal RBCs.