Experimental evaluation of a high-speed photoacoustic tomography system based on a commercial ultrasound unit

A high-speed photoacoustic tomography (PAT) data acquisition system has been developed using a commercial ultrasound (US) unit. Since the US unit supports simultaneous signal acquisition from 64 parallel receive channels, PAT data from a 64-element US array aperture can be acquired using a single laser firing. This arrangement enables an object to be scanned in both US imaging and PAT modes using the same US receiving array and view angle, which facilitates off-line image co-registration and interpretation of the PAT data. To examine the performance of this dual-modality system, experiments were conducted using micro-flow vessel phantoms and ex vivo fresh canine prostate specimens. Preliminary results indicate that an object can be imaged successfully in both US and PAT modes, and that ultrasonic and optical contrast can be presented in a composite image display. In the PAT images, vascular structures are presented clearly and consistently with good contrast-to-noise ratio and satisfactory spatial resolution. A tumor-mimicking lesion induced at a depth of 1.5 cm in a canine prostate is also visualized clearly based on the intrinsic optical contrast between the lesion and the background prostate tissue.