13 March 2009 Photoacoustic imaging with integrating line detectors
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Abstract
Photoacoustic Tomography is an emerging imaging technology mainly for medical and biological applications. A sample is illuminated by a short laser pulse. Depending on the optical properties the electromagnetic radiation is distributed and absorbed. Thereby local temperature increase generates thermal expansion and broadband ultrasonic signals, also called photoacoustic signals. Unlike conventional ultrasound in photoacoustic imaging the contrast depends on the optical properties of the sample which provides not only morphologic information but also functional information. This way photoacoustic imaging combines the advantages of optical imaging (high contrast) and ultrasonic imaging (high spatial resolution) and is particularly suited for medical applications like mammography or skin cancer detection. Our group uses integrating line detectors instead of ultrasonic point receivers. Line detectors integrate the pressure along one dimension whereby the 3D problem is reduced to a 2D problem and enables a tomography setup that requires only a single axis of rotation. Implementations of line detectors use optical interferometers, e.g. a Fabry-Perot interferometer or a Mach-Zehnder interferometer. We use free-beam interferometers as well as fiber-based interferometers for collecting photoacoustic signals. The latter are somewhat easier to handle because they require fewer optical components. Finally, the advantages of optical detection methods over piezoelectric detection methods are the better frequency response and the resistance against electrical interference from the environment. First measurements on phantoms and image reconstruction using a time reversal method demonstrated the capability of integrating line detectors for collecting broadband ultrasonic signals for photoacoustic tomography.
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Hubert Grün, Thomas Berer, Armin Hochreiner, Robert Nuster, Günther Paltauf, Peter Burgholzer, "Photoacoustic imaging with integrating line detectors", Proc. SPIE 7265, Medical Imaging 2009: Ultrasonic Imaging and Signal Processing, 72650K (13 March 2009); doi: 10.1117/12.811009; https://doi.org/10.1117/12.811009
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