Abstract
We have newly developed coaxial and confocal optical-resolution photoacoustic microscopy based on sol-gel composite materials. This transducer contains a concave-shaped piezoelectric layer with a focus depth of 5 mm and a hole with a diameter of 3 mm at the center to pass a laser beam into a phantom. Therefore, this system can directly detect an excited photoacoustic signal without prisms or acoustic lenses. We demonstrate the capability of the system through pulse-echo and photoacoustic imaging experiments. The center frequency of the fabricated transducer is approximately 7 MHz, and its relative bandwidth is 86%. An ex-vivo experiment is conducted, and photoacoustic signals are clearly obtained. As a result, 2- and 3-dimensional maximum amplitude projection images are reconstructed.
Highlights
Photoacoustic (PA) imaging is a novel visualization method that provides optical resolution and acoustic penetration
Microscopy (OR-PAM) is a PA imaging method where the optical focal size is considerably smaller than that of ultrasound, and the spatial resolution of Optical resolution PA microscopy (OR-PAM) is generally determined by optical diffraction
The signal-to-noise ratio (SNR) and sensitivity of PA signals mainly depend on energy power required to transmit a pulsed laser and the receiving performance of an optic-acoustic transmitter (OAT), which transmits a pulsed laser and receives PA signals
Summary
Photoacoustic (PA) imaging is a novel visualization method that provides optical resolution and acoustic penetration. Prisms are used as a customized optical-acoustic combiner with an unfocused ultrasonic transducer, as shown in Figure 1a [1]. In this design, a silicone oil layer sandwiched by two prisms is utilized to achieve the confocal and coaxial alignment of optical and acoustic beams. The silicone layer is optically transparent but acoustically reflective. Wang et al have developed a different PA imaging system using a reflective objective and an ultrasonic transducer, as shown in Figure 1b [2]
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