Conventional ultrasound (US) and photoacoustic (PA) multimodality imaging require the use of a US pulse for US data acquisition and a laser pulse for PA data acquisition. We propose a method for concurrent US and PA data acquisition with a single-laser pulse. A light-absorbing multilayer film that can generate a US pulse based on the thermoelastic effect is used. The selection of appropriate layer thickness, interlayer spacing, and absorption coefficient allows the spectral characteristics of the generated US signal to be adjusted so that it does not overlap with the spectrum of the PA signal generated by the light transmitting through the layer. Thus, the US signal and the PA signal can be generated, received, and separated by using a single-laser pulse combined with spectral filtering. This method is demonstrated using a multilayer film that generates US signals with a center frequency of 24.2 MHz and fractional bandwidth of 26.8%. The synthetic-aperture focusing technique is applied to improve the lateral resolution and the signal-to-noise ratio. A cyst-like phantom and a film phantom were used to demonstrate the feasibility of this method of concurrent PA-US imaging using single-laser pulses.
We propose a multilayer film structure to generate high frequency and narrowband ultrasound. It consists of three light-absorbing layers and two light-transmittance layers. The amplitude is tunable by adjusting the optical absorption coefficient of light-absorbing layers. The delay can be adjusted by changing thicknesses of light-transmittance layers. In one example, the generated high frequency narrowband ultrasound signal has a center frequency of 18.4MHz and 32.6% fractional bandwidth using the proposed multilayer structure. Compared with this result, the single layer structure produces a center frequency of 20.2MHz and 125.7% fractional bandwidth. In addition, a single laser pulse was employed to generate US on the multilayer film as an US source and PA signals of the high optical absorption region of the phantom at the same time. Because the spectral characteristics of the ultrasound signals generated by the multi-layer film are tunable, it can be designed such that the US echo and PA echo are spectrally separable, thus enabling simultaneous US/PA imaging using only a single laser pulse. Feasibility of this proposed method was demonstrated by imaging of a cyst-like phantom.
Photoacoustic (PA) imaging has been investigated for intravascular applications. One of the main challenges
is that the imaging frame rate is limited by the pulse repetition frequency (PRF), thus making real-time
imaging difficult with most high-power solid-state pulse lasers. The goal of this study is to combine
omni-directional optical excitation with a ring array transducer for high-frame-rate imaging, so that the image
frame rate is the same as the laser PRF. In the preliminary study, we developed a real-time integrated
IVUS/IVPA imaging system by modifying an IVUS system in combination with a high-speed Nd:YLF pulsed
laser. In addition, an optical fiber with axicon-like distal tip is designed for omni-directional excitation. In this
design, a PA image is acquired without rotating the laser light. The imaging frame rate of this integrated
imaging system is 19 fps. Both US and PA images are recorded at the same time and co-registered in the
fusion image. The US/PA images of tungsten wire, black tube and rabbit's atherosclerotic aorta were acquired
with this integrated system to evaluate its imaging performance. The lateral/axial -6 dB resolution of US
image is 2.56°/62.4μm. Resolution of PA imaging is 3.76°/91.5μm. The imaging system was also utilized to
acquire IVUS/IVPA images of atherosclerotic rabbit's aorta in ex vivo study.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.