Karl Franzens University Graz
Graz University of Technology
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Karl Franzens University Graz | Graz University of Technology | |
Molecular photoacoustic imaging of contrast agents using pump-probe excitation Video: https://unimeet.uni-graz.at/b/nus-prq-dom-giv Biomedical photoacoustic imaging relies on the absorption and thermalisation of optical excitation pulses to generate and detect ultrasound waves in tissue from which high-resolution images (tens of microns) are reconstructed. The images show the initial pressure distribution, which is primarily dependent upon to the distribution of the tissue chromophores. For excitation wavelengths in the visible and near-infrared range, the overwhelming contrast comes from haemoglobin. While tissues that contain almost transparent cells may be visualised using contrast agents, their abundance is typically low and results in weak increases in image contrast compared to the endogenous background. While multiwavelength imaging and spectral unmixing techniques are often being used to recover images of the contrast agent distributions, these methods have been shown to be of limited validity. To address this limitation, our work is aimed at developing experimental methods that exploit the photophysical properties of specific contrast agents. Using pump-probe excitation, differences in the photoacoustic signal amplitude can be generated that are not observed in the endogenous tissue chromophores. Difference imaging can then be used to visualise the contrast agents. In this talk, an overview of some of the challenges in molecular photoacoustic tomography is given, and our recent work on pump-probe excitation of genetically expressed reporter proteins and polymer nanoparticles is presented. |