Marek Pawlowski

Oxygen distribution in the retinal and choroidal vessels of the cat as measured by a new phosphorescence imaging method

The oxygen tension in the vessels of the retina and optic nerve head has been measured noninvasively with a new phosphorescence imaging method. A phosphorescent oxygen-dependent probe, injected into the bloodstream of cats, was excited with a flash of light and the phosphorescence lifetime of the probe was measured. A simple Stern-Volmer relationship was used to convert lifetime to oxygen tension, and two-dimensional maps of intravascular oxygen tension were produced. We describe the equipment and the methodology for obtaining oxygen maps.

Monitoring of the Oxygen Pressure in the Blood of Live Animals Using the Oxygen Dependent Quenching of Phosphorescence

Oxygen dependent quenching of phosphorescence is a powerful new method for measuring oxygen pressure in biological systems (see Vanderkooi et al, J. Biol. Chem. 262 (1987) 5476; Wilson et al, J. Biol. Chem. 263 (1988) 2712). This technology has now been extended to include measurements of the phosphorescent of oxygen probes dissolved in the blood as a complex with albumin. In this communication, we report on a new microcomputer controlled phosphorimeter in which the tissue is illuminated by a flash lamp and the phosphorescence observed through flexible light guides designed to make measurements in regions down to approximately 1 mm in diameter. Measurements of the phosphorescence lifetimes of these probes in regions of tissue necessarily report a distribution of oxygen pressures due to the presence of blood in veins and arteriols as well as that present in the capillaries. Thus the phosphorescence decay is the sum of a continuum of exponentials with different decay constants and initial intensities. The complete phosphorescence decay curve is digitized using a 12 bit, 1 MHz A/D board and deconvoluted using numerical methods to yield a distribution of exponentials contributing to the total decay curve.

Imaging Oxygen Pressure in Tissue in Vivo by Phosphorescence Decay

A new imaging system, OxyMap®, has been developed to noninvasively obtain two dimensional maps of the distribution of oxygen concentration in living tissue by imaging the decay of the phosphorescent probes, such as Pd-meso-tetra (4-carboxyphenyl) porphine, in the blood. The phosphorescence of these probes is quenched by oxygen according to the relationship:

Effect of hyperventilation on oxygenation of the brain cortex of newborn piglets

\tfrac{{{T_0}}}{T} = 1 + {K_Q}^*{T_0}^*P{O_2}

Device and method for measuring tissue oxygenation through the skin using oxygen dependent quenching of phosphorescence

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Intravascular oxygen distribution in subcutaneous 9L tumors and radiation sensitivity

It is generally accepted that a non-invasive method for measuring oxygen pressure in the heart would be a valuable aid to investigators interested in heart and circulatory physiology. We have developed an optical method for imaging the oxygen pressure in the surface layer of tissue, 0.5 to 1 mm in depth, which is based on the oxygen dependent quenching of phosphoresence (Rumsey et al., 1988; 1990; 1991; Wilson et al., 1988; 1991; 1992). From these measurements, two dimensional maps are constructed, thereby providing an accurate analysis of oxygen pressure in tissue in response to various stimuli and experimental conditions. The motion of the heart induced largely by the systolic phase of the cardiac cycle limits the time available for image acquisistion. This necessitates the synchronization of the operation of the flash lamp and imaging of the phosphorescence with the cardiac cycle. In this study we provide preliminary data that show it is possible to obtain maps of oxygen pressure in the epicardium of the heart in vivo.