Three-dimensional photoacoustic imaging using a two-dimensional CMUT array

Abstract

In this paper, we describe using a 2-D array of capacitive micromachined ultrasonic transducers (CMUTs) to perform 3-D photoacoustic and acoustic imaging. A tunable optical parametric oscillator laser system that generates nanosecond laser pulses was used to induce the photoacoustic signals. To demonstrate the feasibility of the system, 2 different phantoms were imaged. The first phantom consisted of alternating black and transparent fishing lines of 180 mum and 150 mum diameter, respectively. The second phantom comprised polyethylene tubes, embedded in chicken breast tissue, filled with liquids such as the dye indocyanine green, pig blood, and a mixture of the 2. The tubes were embedded at a depth of 0.8 cm inside the tissue and were at an overall distance of 1.8 cm from the CMUT array. Two-dimensional cross-sectional slices and 3-D volume rendered images of pulse-echo data as well as photoacoustic data are presented. The profile and beamwidths of the fishing line are analyzed and compared with a numerical simulation carried out using the Field II ultrasound simulation software. We investigated using a large aperture (64 x 64 element array) to perform photoacoustic and acoustic imaging by mechanically scanning a smaller CMUT array (16 x 16 elements). Two-dimensional transducer arrays overcome many of the limitations of a mechanically scanned system and enable volumetric imaging. Advantages of CMUT technology for photoacoustic imaging include the ease of integration with electronics, ability to fabricate large, fully populated 2-D arrays with arbitrary geometries, wide-bandwidth arrays and high-frequency arrays. A CMUT based photoacoustic system is proposed as a viable alternative to a piezoelectric transducer based photoacoustic systems.

In vivo three-dimensional photoacoustic imaging based on a clinical matrix array ultrasound probe

“…Compared to previous PA imaging systems employing 2-D array US transducers, [12][13][14] this system provides sub-millimeter spatial resolution, enables fast PA data acquisition, and incorporates real-time 3-D US imaging functionality of the commercial US scanner system. The current DAQ system acquires the PA data set for one volumetric frame in ∼20 sec from 36 laser firings.…”

“…Khuri-Yakub et al have fabricated a 2-D capacitive micromachined ultrasonic transducer (CMUT) with 16 × 16 elements (pitch size, 250 μm) for PA and US imaging. 12 Mechanical scanning was needed to form a large detection aperture to improve the image quality. Zhu et al have developed a 2-D array US transducer with 10 × 128 elements for US and PA characterization of ovarian tissue.…”

Wideband acoustic activation and detection of droplet vaporization events using a capacitive micromachined ultrasonic transducer

“…Compared to traditional piezoelectric technology, CMUTs are known for having a fractional frequency bandwidth usually wider than 100%. 26 Therefore, CMUT technology is particularly attractive for wideband imaging applications such as photoacoustic imaging 27 or contrast agent imaging, 28 or as a hydrophone. 29 In a previous study, Novell et al demonstrated that a CMUT array could be exploited to enhance the signal from contrast agents by recording the microbubble response at subharmonic and second harmonic frequencies simultaneously.…”

Ultrafast Photoacoustic Imaging and its Application to Real-Time 3D Imaging with Improved Focusing

“…2 Another method employs a 2D capacitive micromachined ultrasonic transducer (CMUT) to collect the volume data. 3 The other includes collocation of piezoelectric transducers. P. Ephrat et al arranged fifteen commercial transducers to constitute a sparse array.…”