Abstract
A photoacoustic tomograph based on optical ultrasound detection is demonstrated, which is capable of high resolution real-time projection imaging and fast three-dimensional (3D) imaging. Snapshots of the pressure field outside the imaged object are taken at defined delay times after photoacoustic excitation by use of a charge coupled device (CCD) camera in combination with an optical phase contrast method. From the obtained wave patterns photoacoustic projection images are reconstructed using a back propagation Fourier domain reconstruction algorithm. Applying the inverse Radon transform to a set of projections recorded over a half rotation of the sample provides 3D photoacoustic tomography images in less than one minute with a resolution below 100 µm. The sensitivity of the device was experimentally determined to be 5.1 kPa over a projection length of 1 mm. In vivo images of the vasculature of a mouse demonstrate the potential of the developed method for biomedical applications.
Highlights
Photoacoustic tomography (PAT) is a non-invasive imaging technique that can provide images with ultrasound resolution related to the distribution of optical absorption within biological tissue
Photoacoustic (or optoacoustic) tomography (PAT) relies on the thermoelastic effect, the generation of acoustic waves due to the absorption of pulsed laser light
We have shown the applicability of an optical phase contrast detection (OPCD) method in PAT [16]
Summary
Photoacoustic (or optoacoustic) tomography (PAT) is a non-invasive imaging technique that can provide images with ultrasound resolution related to the distribution of optical absorption within biological tissue. Its increasing significance in medical and biological research arises from the possibility to visualize intrinsic absorbers like hemoglobin. PAT relies on the thermoelastic effect, the generation of acoustic waves due to the absorption of pulsed laser light. Local absorption and rapid heating result in generation of broadband ultrasound waves. By recording these waves, the initial absorbed energy distribution can be reconstructed. Photoacoustic imaging is a hybrid technique making use of optical absorption and ultrasonic wave propagation, leading to high contrast and high spatial resolution
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