Fig. 3.

Photoacoustic imaging configurations. The detectors and the laser source may be on the same side or at an angle to each other. (A) Photoacoustic imaging performed using a conventional ultrasound transducer, in which only part of the spherical wave front originating from the target is registered by the transducer. (B) Photoacoustic tomography showing X-ray computed tomography–like reconstruction, in which a single detector can be rotated around the target or an array of multiple stationary detector elements can be deployed around the target. The signal arriving at each detector is filtered, back-projected along circular arcs in the spatial domain, and all the back-projections are then added together to obtain the final photoacoustic image, which represents the spatial distribution of optical absorption within the target.