Workshop on Bioimaging I, Wed, 14 Nov, 2007
Speaker: Martin Frenz
Abstract
Optoacoustic (OA) imaging of biological tissue is a technique undergoing rapid development with great promise for early breast and skin cancer diagnostics as well as small animal research. It is based on the detection of ultrasound waves generated inside the tissue by irradiation with ns laser pulses. Optically absorbing structures are heated by the irradiating light and subsequently generate acoustic relaxation transients that can be measured at the tissue surface by a linear array ultrasonic detector. Due to the short laser pulses used, spatially resolved information is conserved in the temporal profile of the measured signals and can be reconstructed using inverse methods. Compared to echo-ultrasound imaging and computer tomography, optoacoustic imaging exhibits two main drawbacks, which make solving the inverse problem complicated. First, the irradiating laser light can not be focused due to the strong scattering of tissue that will lead the sum-and-delay algorithm commonly used in ultrasonic imaging to produce strong artefacts and secondly, optoacoustic signals can usually not be acquired on a closed surface around the sample as done in CT, which makes the use of the inverse radon transform for image reconstruction problematic. These problems will be discussed. Besides, a reconstruction algorithm based on a regularizing FFT interpolation method which has been optimized for real-time imaging will be presented. The system can be integrated into a real-time phased-array ultrasound imaging device, giving important complementary information to the classical echographic images. Simulations as well as phantom studies will be presented.
URL: www.ricam.oeaw.ac.at/specsem/ssqbm/participants/abstracts/index.php
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