Laser-diode based 10MHz photoacoustic Doppler flowmetry at 830 nm

Photoacoustic Doppler Flowmetry has several potential advantages over its purely acoustical counterpart. The key ones are better inherent contrast and potential molecular information. It is therefore highly desired to continue to develop this modality into a viable complementary tool alongside with Doppler Ultrasound flowmetry. Working towards this goal we have constructed a Photoacoustic Doppler setup based on a combined pair of laser diodes at 830nm and a 10MHz focused acoustical transducer. Using tone-burst intensity modulation, depth-resolved Doppler spectrograms of a phantom vessel containing flowing suspension of carbon particles, were obtained. In order to investigate the conditions required for successful photoacoustic Doppler measurement in blood a k-space photoacoustic simulation was performed. It tested the photoacoustic response which is obtained for moving random spatial distributions of red blood cells and the effect of several parameters, such as particles density, ultrasonic frequency and optical spot size.