Photoacoustic imaging: hybrid technology for small animals holding potentials translatable for clinical applications

Photoacoustic imaging is an emerging modality that exploits the photoacoustic effect to combine the high contrast of optical imaging with the spatial resolution and penetration depth of ultrasound. A key feature of PA imaging methods is that they exploit optical contrast but employ US detection principles. The PA effect offers a way to take advantage of the ability of light to penetrate into the body and let us defeat light diffusion by using US waves to “see” the penetrating light. The main advantage of this hybrid approach is that the optical properties of biological tissue, including high contrast and spectral specificity, are encoded in an ultrasound signal. Resolutions of better than 1 mm can be obtained at depths measured in centimeters (up to 7) and not in millimeters, depending on the laser wavelength and transducer frequency used, opening up entirely new regimens of “optical imaging.” From a clinical standpoint, PA imaging is complementary in nature and synergetic with US and a combined US and PA imaging system can be easily implemented due to the presence of a shared detector and associated electronics. Furthermore, such a system will be readily accepted by clinicians familiar with US imaging.