Photoacoustic imaging using a two-dimensional CMUT array

Photoacoustic imaging is a promising complement to pulse-echo ultrasound imaging because it provides contrast between areas with different light absorption characteristics. Specifically, regions with higher blood concentration can be identified, which is useful for imaging vascularization and the early detection of cancer. Here we present volumetric photoacoustic images of a vessel-like phantom. The phantom consists of three 1.3-mm diameter tubes inside a tissue mimicking material. The center tube is filled with ink to provide optical contrast. A two-dimensional capacitive micromachined ultrasonic transducer (CMUT) array is used for acoustic detection. The use of a two-dimensional transducer array eliminates the drawbacks of a mechanically scanned system and enables volumetric imaging. CMUT technology enables new types of transducer arrays that would benefit photoacoustic imaging. Fully populated two-dimensional arrays, annular ring-arrays, and high-frequency arrays have all been demonstrated using CMUT technology and have advantages for photoacoustic imaging systems. Other advantages of CMUT technology for photoacoustic imaging include a wider bandwidth than comparable piezoelectric devices and ease of integration with electronics.