Cost-effective Design of a Photoacoustic-Ultrasound Microscope Using Single Laser Pulses

A dual-modality photoacoustic-ultrasound system was developed for mapping three-dimensional models of tumor angiogenesis. The system features micron scale spatial resolution in photoacoustic imaging, high resolution in ultrasound imaging and high imaging depth. With a single pulsed laser diode, the system is able to make dual-modality images by laser induced ultrasound without an additional ultrasonic pulser. A multilayer film made by PDMS and graphite powder was used to generate high frequency and narrow band ultrasound. Accordingly, photoacoustic and ultrasound signals can be separated with simple filtering and the photoacoustic image and the ultrasound image can be generated concurrently. The scheme creates 10 dB signal contrast and was tested with a fiber and cyst phantom. Gold nanorods with the absorption peak in near infrared range were used to generate the photoacoustic signal. By targeting gold nanorods on the vessels, the system has the potential to investigate neovascularization and establish 3D tumor angiogenesis models.