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UNIVERSITY OF BUCHAREST
FACULTY OF PHYSICS Guest
2024-11-24 9:51 |
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Conference: Bucharest University Faculty of Physics 2011 Meeting
Section: Biophysics; Medical Physics
Title:
Dynamic and static measurements of oxygenation and blood volume
Authors:
M. Patachia(1,2), D. C. A. Dutu(1), S Banita(1), D. C. Dumitras(1), Aurel Popescu(2)
Affiliation:
1Department of Lasers, National Institute for Laser, Plasma and Radiation Physics,
409 Atomistilor St., PO Box MG-36, 077125 Bucharest, Romania
2 Faculty of Physics, University of Bucharest, Romania
409 Atomistilor St., PO Box MG-36, 077125 Bucharest, Romania
2Faculty of Physics, University of Bucharest, Romania
E-mail
mihai.patachia@inflpr.ro
Keywords:
Abstract:
The multispectral DOT enables the non-invasive reconstruction of the internal tissue structure and the evaluation of the tissue pathology. Total hemoglobin concentration (THC) and tissue blood oxygenation (StO2) are used for evaluation of the tissue pathology.
Using optical measurements at multiple source-detector positions on the tissue surface, one can reconstruct the internal distribution of the absorption coefficient (µa) and the reduced scattering coefficient (µ´s) in two or three dimensions based on the transport model.
We have built an inexpensive continuous-wave DOT system containing two spatially combined laser diode sources (at 785 nm and 830 nm), one silicon photo diode (SiPD), a transimpedance amplifier and two lock-in amplifiers, which can acquire 128 independent measurements in less than 50 seconds through two time-division-multiplexed optic scheme with eight illumination fibers and eight detector fibers in the measuring head (optode) [1].
The spectral selectivity of a multispectral DOT system enables also the evaluation of some new physiological parameters related to hemoglobin concentration and blood oxygenation (THC and StO2 distributions) which can better characterize the angiogenesis in the tumor zone, improving the resolution and the contrast of the tomographic image.
A dynamic liquid phantom simulating the optical properties of the tissue was used in order to test the efficiency of the system. The basis of the phantom was formed by a scattering solution of Intralipid (Lipofundin) and water with an overall reduced scattering coefficient of 0.8 mm-1 (785 nm). The solution was placed in a cylindrical beaker. A magnetic stirring rod maintains the homogeneity during the experiment. Red blood cells obtained from healthy human blood were added to scattering solution to achieve a volume fraction of 1.5% and total hemoglobin concentration of 26 μM. This is a typical value for normal physiological conditions with an assumption of 4.0% blood volume and 40% hematocrit. The hemoglobin saturation was measured to be 85%.
In order to induce deoxygenation on the liquid phantom, 4 g of dry bakers yeast was added to the solution. The temperature of the phantom was maintained at 37°C to keep the yeast active. This condition was maintained over a time of about 20–30 min. Deoxygenation was observed until hemoglobin saturation reached a steady state at 25%. After deoxygenation of yeast-intralipid solution reached steady state, oxygenation was simulated again by delivering extra oxygen to the phantom from an oxygen tank. Oxygen supply was maintained until a steady state level of oxygenation was obtained. Steady state hemoglobin saturation was 89%.
The chromophore distribution analysis through continuous-wave Near Infrared Spectroscopy (cwNIRS) can enhance the resolution and accuracy in various deep-tissue applications of the cw DOT, including breast cancer imaging [2]. The THC increase in tumour is expected due to angiogenesis accompanying tumour growth.
The obtained results [3] confirm the design parameters of the liquid phantom and the ability of the system to evaluate the hemoglobin and oxyhemoglobin concentration.
The good agreement of the static and dynamic measurements demonstrates the homogeneity of the liquid phantom. The resulted data presented less than 5% variations in the measurements, which are due to the oxygen bubbles flowing in solution during the oxygenation process and to the yeast mud resulting from the insertion of the yeast bag in the liquid phantom.
1. D.C.A. Dutu, D.C. Dumitras, C. Matei, A. M. Magureanu, M. Patachia, S. Miclos, D. Savastru, X. Liang, H. Jiang, and N. Iftimia, "Design and parametric evaluation of a continuous-wave diffuse optical tomography system", ICPEPA ’09 Sapporo, Japan (2009).
2. S. Srinivasan, B. W. Pogue, S. D. Jiang, H. Dehghani, C. Kogel, S. Soho, J. J. Gibson, T. D. Tosteson, S. P. Poplack, and K. D. Paulsen, "Interpreting haemoglobin and water concentration, oxygen saturation, and scattering measured in vivo by near-infrared breast tomography", Proc. Natl. Acad. Sci. U. S. A. 100, 12349–12354 (2003).
3. M. Patachia, D.C.A. Dutu, D.C. Dumitras, "Blood oxygenation monitoring by diffuse optical tomography", Quantum Electronics 40 (12) 1062 – 1066 (2010).
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