Abstract
Intensive research on photoacoustics (PA) for imaging of the living human body, including the skin, vessels, and tumors, has recently been conducted. We propose a PA measurement system based on a capacitive micromachined ultrasonic transducer (CMUT) with waterless coupling, short measurement time (<1 s), backward light irradiation, and a low-profile ultrasonic receiver unit (<1 cm). We fabricate a 64-element CMUT ring array with 6.2 mm diameter and 10.4 MHz center frequency in air, and 100% yield and uniform element response. To validate the PA tissue characterization, we employ pencil lead and red ink as solid and liquid models, respectively, and a living body to target moles and vessels. The system implements a near-field imaging system consisting of a 6 mm polydimethylsiloxane (PDMS) matching layer between the object and CMUT, which has a 3.7 MHz center frequency in PDMS. Experiments were performed in a waterless contact on the PDMS and the laser was irradiated with a 1 cm diameter. The experimental results show the feasibility of this near-field PA imaging system for position and depth detection of skin, mole, vessel cells, etc. Therefore, a system applicable to a low-profile compact biomedical device is presented.
Highlights
Photoacoustic imaging (PAI) in soft tissue has been studied extensively in the context of biomedical imaging
In this article, motivated by ultrasound medical imaging, we demonstrate PA volumetric imaging using a capacitive micromachined ultrasonic transducer (UT) (CMUT), which can be applied in compact devices such as smart watches and bands
Photoacoustic Image Results Based on Phantom and 2 mm diameter, respectively, to estimate spatial resolution and validate the imaging feasibility for both solid and liquid materials
Summary
Photoacoustic imaging (PAI) in soft tissue has been studied extensively in the context of biomedical imaging. Compared with optical imaging techniques, PAI provides deeper penetration and superior spatial resolution and contrast, as determined by the ultrasonic transducer (UT) specifications such as the center frequency, cell size and pitch, element size and pitch, and receiving sensitivity [1,2]. Most previous PAI studies have targeted spatial resolution and contrast improvement. The acoustic sensing system presented in this work has the following advantages: waterless coupling, backward-mode laser irradiation, a low-profile ultrasonic receiver unit (
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