Forward-looking photoacoustic imaging (PAI), with the potential to capture three-dimensional (3D) images of tissue structures and distinguish their characteristics, is desired in order to perform more efficient catheter interventions for complicated diseases, such as chronic total occlusion. However, few studies have reported forward-looking 3D PAI. In this study, we experimentally demonstrated the forward-looking 3D PAI in vitro with our optical-resolution PAI system.
To construct a 3D image, an optical-resolution PAI with a piezoelectric fiber actuator is used. The actuator is attached to the fiber and oscillates it to spirally control the direction of a laser. For each laser emission, a photoacoustic signal that is generated at each laser line (or volume) is received by a capacitive micromachined ultrasound transducer (CMUT). As the laser directions and ultrasound time of flight are known, the positions of the laser-induced ultrasound sources are determined and therefore, the 3D image can be constructed.
In our in vitro experiments, a laser pulse was emitted from multi-mode fiber illuminated carbon rod samples with diameters of 0.5 mm. The rod samples formed grid structures with a spacing of 1.0 mm. The distance between the CMUT receiver and the samples was about 10 mm. The structures in the resultant images, created with a rendering technique, were visualized with a signal-to-noise ratio of over 10. In the presentation, detailed results taken by the forward-looking 3D PAI system will be described.
Tomohiko Tanaka, Ryo Imai, Taiichi Takezaki, Takahiro Matsuda, and Shinsuke Onoe, "Forward-looking 3D photoacoustics for intravascular imaging (Conference Presentation)," Proc. SPIE 10494, Photons Plus Ultrasound: Imaging and Sensing 2018, 1049418 (Presented at SPIE BiOS: January 29, 2018; Published: 15 March 2018); https://doi.org/10.1117/12.2291624.5752218868001.
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