Abstract
Photoacoustic imaging is a new biomedical imaging modality based on the use of laser-generated ultrasound. It is a hybrid technique that combines the high contrast and spectroscopic-based specificity of optical imaging with the high spatial resolution available to ultrasound. As a consequence it overcomes the limited penetration depth/spatial resolution of purely optical imaging techniques such as multiphoton microscopy or diffuse optical tomography due to the overwhelming optical scattering exhibited by tissue. At the same time it retains their high contrast and spectral specificity enabling visualisation of anatomical features indistinguishable with other modalities such as ultrasound imaging. The technique has several specific attributes that make it a potentially powerful tool for preclinical cancer studies. First, it can provide 3D images of vascular anatomy with high spatial resolution and contrast, the latter being a consequence of the strong absorption of haemoglobin at visible and near-infrared wavelengths. Second, it can reveal the distribution of blood oxygen saturation over the vasculature by obtaining images at multiple wavelengths and exploiting the spectral difference between oxy and deoxyhaemoglobin. Third, by extracting the Doppler shift from photoacoustic waves generated in red blood cells, measurements of blood flow can be acquired. As well as exploiting endogenous contrast provided by haemoglobin, there is also the potential, through the use of targeted contrast agents or genetic reporters to provide information at a cellular/molecular level.
© 2013 Optical Society of America
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