Researchers Joanna Brunker and Paul Beard at UCL, Department of Medical Physics and Biomedical Engineering, London, UK used a Litron Nano L double pulse laser in their ground breaking work. 
The Nano L PIV laser uses a dedicated dual cavity design with a single integrated PSU to provide two completely independent, collinear and stable pulses with inter-pulse time intervals determined by the researchers as required by their experiments. More information about double pulse lasers …>
Photoacoustic Doppler velocimetry provides a major opportunity to overcome limitations of existing blood flow measuring methods. By enabling measurements with high spatial resolution several millimetres deep in tissue, it could probe microvascular blood flow abnormalities characteristic of many different diseases. 
Although previous work has demonstrated feasibility in solid phantoms, measurements in blood have proved significantly more challenging. This difficulty is commonly attributed to the requirement that the absorber spatial distribution is heterogeneous relative to the minimum detectable acoustic wavelength.
Read the full paper …>
UCL Medical Physics and Biomedical Engineering.