High-contrast real-time optoacoustic imaging of subcutaneous blood vessels

In optoacoustic imaging, acoustical signals are generated when short light pulses are absorbed in tissue. Thus, the higher the absorption coefficient of the investigated tissue is, the stronger the optoacoustic signals will be. The absorption of blood in the NIR is several orders of magnitude higher than of other tissue types, so that it can be imaged with very high contrast. We developed a hardware platform based on our multichannel ultrasound beamformer DiPhAS which supports optoacoustic techniques and allows to image subcutaneous vessels with high signal to noise ratio in real time. A light weight handheld probe which integrates acoustic signal detection and laser light delivery allows convenient handling. Optimized reconstruction algorithms and a hardware with 128 channels allow data acquisition, processing and display at a repetition rate only limited by the laser PRF of 20Hz. The imaging performance of our system was characterized on optoacoustic phantoms. Further, 2D and 3D in-vivo data sets of human blood vessels were acquired and different reconstruction algorithms were applied in order to maximize the signal-to-noise ratio of the images. Using laser energies of about 10% of the maximum permissible energy, vessels could be imaged with a SNR in the range of 25 to 35dB.