KEYWORDS: Doppler tomography, Optical coherence tomography, Heart, Signal processing, Electronic filtering, Linear filtering, Field programmable gate arrays, Signal analyzers, In vivo imaging, Optical filters
We demonstrate a field programmable gate-array-based real-time optical Doppler tomography system. A complex-valued bandpass filter is used for the first time in optical coherence tomography signal processing to create the analytic signal. This method simplifies the filter design, and allows efficient and compact implementation by combining the conversion to an analytic signal with a pulse shaping function without the need for extra resources as compared to the Hilbert transform method. The conversion of the analytic signal to amplitude and phase is done by use of the coordinate rotation digital computer (CORDIC) algorithm, which is an efficient algorithm that maps well to the field programmable gate array. Flow phantom experiments, and the use of this system for in vivo imaging of cardiac dynamics in the chick embryo, are presented. We demonstrate the visualization of blood flow in the early embryonic heart as well as in the aorta, small peripheric vitelline vessels, and coronary arteries of fully formed chick hearts.
We investigate vascular changes during Photodynamic therapy (PDT) of skin tumors using optical Doppler tomography
(ODT). The effect of vascular shut down on tumor destruction is currently not known, and to optimize treatment it is
relevant to investigate this issue further. Optical Doppler tomography is capable of measuring blood flow in biological
tissue down to 1-2 mm with sub-mm/s velocity sensitivity and micrometer spatial resolution making it suitable for blood
flow measurements in the skin. We demonstrate the ability of detecting blood flow in the human skin using non-interstitial
ODT to preserve the non-invasiveness. In general a very limited blood flow activity was observed in normal
skin and around skin tumors making monitoring of changes difficult. We suggest solutions to a number of practical
issues such as sampling errors and natural fluctuations in flow activity for future work.
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