Abstract
In this study, a virtual-point concept was introduced into fiber-laser photoacoustic tomography to improve the elevational image resolution. The flexible fiber laser was bent into an arc shape to conform to the ultrasound wavefront, which formed an ultrasound focus at the center of the arc. The synthetic aperture focusing technique was utilized to reconstruct the images; as a result, the elevational resolution particularly within the out-of-focus region was considerably improved compared to the resolution of an image retrieved by multiplexing the PA time-resolved signals with sound velocity. The all-optical fiber-laser photoacoustic tomography system with a high spatial resolution has potential for various applications, including biomedical research and preclinical/clinical diagnosis.
Highlights
Photoacoustic tomography (PAT) is a hybrid, noninvasive biomedical imaging technology that combines the high contrast of optical imaging and deep penetration of ultrasonography [1,2,3,4,5,6]
The average optical fluence on the target surface is ∼3 mJ/cm2, which is within the maximum permissible exposure (MPE) of 20 mJ/cm2 recommended by the American National Standards Institute (ANSI)
Elevational resolution improvement To verify the improvement in elevational resolution by the virtual-point synthetic aperture focusing technique (SAFT), the k-wave MATLAB® toolbox was used to simulate the spatial response of the focused fiber laser to ultrasound
Summary
Photoacoustic tomography (PAT) is a hybrid, noninvasive biomedical imaging technology that combines the high contrast of optical imaging and deep penetration of ultrasonography [1,2,3,4,5,6]. Photoacoustic (PA) signals generated from an absorber irradiated using a short-pulse laser are detected to acquire the structural and functional information of the biological tissues. The absorber can be endogenous in biological tissues, for example, hemoglobin, melanin, and lipids, or an exogenous contrast agent such as dyes and nanomaterials [7,8,9]. Most PAT systems detect PA signals using piezoelectric (PZT) ultrasound transducers that are sensitive to electromagnetic interference (EMI) and have limited acceptance angles because of their large aperture sizes [10]. Small-sized transducers theoretically have larger acceptance angles, their sensitivity is low because of the smaller active element and higher
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