Objectieve:In order to get the photoacoustic (PA) image of micro-blood vessel deep inside biological tissue.Materials and Methods:A 532nm pulse laser with the repetition rate of 10Hz was used as the pumping source.A wide band unfocused needle ultrasound transducer was used to collect time-domain PA signal of the tissue-mimicking phantom by circular scan.The 2D optical absorption image was reconstructed by time-domain spherical back projection algorithm.The spatial resolution was measured by line-spread-function(LSF).Results:The experimental results demonstrated that the spatial resolution was 0.1 mm and the PA image of the micro-vascular network agreed well with the tissue-mimicking phantom.Conclusion:The proposed method is valuable for the diagnosis of early cancer inside tissue.

Objective To get photoacoustic (PA) image of vascular structure inside mouse brain in vivo.Methods A 532nm pulsed laser was used as the pumping source to generate PA signal,and a wide-band PVDF unfocused ultrasound transducer was used to collect time-domain PA signal by circular scan.PA signal recorded at each scanning position was then de-noised by wavelets transform using soft-thresholding.The PA image of the mouse brain vessel was reconstructed by time-domain spherical back projection algorithm.Results PA image agreed well with the histological picture of mouse brain vessel.Conclusion The experimental result indicates the potential value of clinical application.