Abstract
Photoacoustic tomography relies on a dense coverage of the surface surrounding the imaged object with ultrasound sensors in order to enable an accurate reconstruction. A curved arrangement of integrating line sensors is proposed that is able to acquire data for a linear projection image of the absorbed energy density distribution in the object. Upon rotation of the object relative to the array, three-dimensional (3D) images can be obtained.The proposed design is based on the cost-effective piezoelectric polymer film technology with 64 line shaped sensors arranged on a half-cylindrical surface. It is combined with an optical parametric oscillator for the near infrared as a source for laser pulses. Image reconstruction from recorded signals consists of two-dimensional (2D) back projection followed by an inverse Radon transform.The tomograph exhibits a spatial resolution on the order of 200 to 250μm. In a phantom experiment, the steps from acquisition of a single, 2D projection image to a full 3D image are demonstrated. Finally, in vivo projection images of a human finger are shown, revealing the near real-time imaging capability of the device in 2D.
Highlights
Photoacoustic imaging has been established as a method for obtaining images of biological tissue with optical contrast and high resolution
Pulsed laser sources that are suitable for photoacoustic excitation, primarily optical parametric oscillators (OPOs), are offered with specifications ideal for this purpose
We present a photoacoustic tomograph manufactured of relatively low-cost components such as standard electronics and a piezoelectric polymer film, combined with an OPO for the near infrared
Summary
Photoacoustic (or optoacoustic) imaging has been established as a method for obtaining images of biological tissue with optical contrast and high resolution The combination of these favorable properties arises from the thermoelastic generation of sound waves by deeply penetrating, diffuse light from pulsed laser sources. Still much less expensive than magnetic resonance tomography devices, the costs of commercial photoacoustic tomographs for small animal imaging are rather high and it has become an attractive alternative to design and manufacture PAT devices in the own lab. This is facilitated by the availability of multichannel analog to digital converters with the desired bandwidth. Pulsed laser sources that are suitable for photoacoustic excitation, primarily optical parametric oscillators (OPOs), are offered with specifications ideal for this purpose
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