Surgery – Diagnostic testing – Measuring or detecting nonradioactive constituent of body...
Reexamination Certificate
2000-03-28
2002-02-05
Nasser, Robert L. (Department: 3736)
Surgery
Diagnostic testing
Measuring or detecting nonradioactive constituent of body...
C600S317000, C436S172000, C422S080000, C422S082050, C422S082080
Reexamination Certificate
active
06345191
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a system for quantitative determination of the areal distribution of a quantity to be measured, including a planar sensor film, which is applied to a possibly curved measuring surface, such as the surface of a body organ, a region of the skin or a cell culture, and whose diffusion properties regarding a parameter to be determined are known, said sensor film containing a luminescent indicator responding to the parameter to be determined with a change of at least one optical property, and comprising an excitation and detection unit including a means for supplying excitation radiation of at least one wavelength and an imaging detection means, preferably a CCD camera, and an evaluation unit processing the image information obtained from the excitation and detection unit.
DESCRIPTION OF THE PRIOR ART
In medical diagnosis and in the monitoring and control of medical treatment it may be most desirable to determine the areal distribution of the concentration of a measurement variable on the surface of a body organ, such as the skin, or the distribution of the flow rate of a given substance through a boundary surface, such as a surface of a body organ, a region of the skin, or a cell culture in a laboratory set-up.
In this context a schematical configuration has become known from EP 0 516 610 B1, by means of which readings for the material flux, such as oxygen flux, through an interface, such as a skin surface, may be taken. The sensing layer of the measuring device, which is assigned to the boundary face or measuring surface, will exert a known or predefined, finite resistance to the material flux to be determined, at least one optical indicator being provided in the sensing layer for determining the material concentration on one side of the sensing layer. The measured or known concentration value on the other side of the sensing layer, or the difference relative to the first concentration value, is used to determine the material flux through the boundary face. In a variant of the invention the surface of the sensing layer is scanned by a plurality of detectors or by means of an imaging system (CCD).
In U.S. Pat. No. 5,593,899 an apparatus and method for measuring tissue oxygenation are disclosed, using the oxygen dependent quenching of a fluorescent indicator. To measure oxygen supply, a luminescent layer, which is part of a skin cream, is applied to a particular surface region of the skin, and is covered with an oxygen-impermeable film. The optical device enclosed in a plastic housing is provided with a plastic or glass cover which is directly placed over the O
2
-impermeable film. Further included are an interference filter and a photodiode. Via optical fiberguides the luminescent layer is exposed to excitation radiation from a modulated radiation source. The plastic housing further includes heating elements, which are connected to a thermoregulation circuit and heat up the measuring region to a temperature of 39° to 42° C. The arrangement described in this document is suitable only for integrated measurements over the entire measuring region covered by the optical device. It does not yield accurate information on boundaries between regions with satisfactory oxygen supply and those with oxygen deficiency.
Theoretical considerations on the local distribution of oxygen flux or subcutaneous oxygen concentration and a proposal concerning an imaging technique are disclosed in “Fluorescence Lifetime Imaging of the Skin PO
2
: Instrumentation and Results” in
Advances in Experimental Medicine and Biology
, Vol. 428, 605-611 (1997), Plenum Press, N.Y. In this article a sensor membrane measuring transcutaneous oxygen concentration is described, which consists of an optical isolating layer next to the skin, a sensing layer containing a luminescent indicator with O
2
-sensitive decay time, and an oxygen-impermeable supporting foil. Another membrane measuring oxygen flux, which is also described in this paper, differs from the former by a diffusion barrier with known oxygen permeability, which is used instead of the O
2
-impermeable layer. For the measuring process the sensor membrane is applied to the measuring surface, for example, a region of skin. A modulation technique is employed for measuring, where the LEDs emitting excitation radiation in the direction of the sensor membrane are driven by a square-wave generator. The phase-shifted light radiation emitted by the sensor membrane is detected by a CCD camera with modulated amplification and transmitted pixel by pixel to a computing unit for image-processing. Images of the oxygen distribution measured in a polymer layer as compared to the inhomogeneous oxygen distribution over a region of the skin are part of the documentation.
Other imaging methods using phase fluorimetry are disclosed in U.S. Pat. No. 5,485,530.
Finally, the paper “A modular luminescence lifetime imaging system for mapping oxygen distribution in biological samples” published in
Sensors and Actuators
B 51 (1998) 163-170, is concerned with an imaging method measuring two-dimensional oxygen distributions with planar optodes. The experimental set-up includes a test chamber with several perfusion channels, through which water with different oxygen concentrations is guided. In the direction of the optical system the channels are closed with a planar optode pressed against the test chamber. For excitation of the planar optode a fiber-optical ring light source is employed, radiation detection is effected by means of a CCD camera.
SUMMARY OF THE INVENTION
It is an object of this invention to further develop the above system so as to obtain reproducible measurement results of the areal or local distribution of the concentration of a measurement variable over a possibly curved surface, or the areal distribution of the material flux through a possibly curved surface, and to display the obtained results with the use of an imaging method.
According to the invention this object is achieved by providing the apparatus with an applicator tube to be placed over the measuring surface, whose rim facing the measuring surface is in elastic contact with the sensor film and is impervious to external radiation interfering with the detection means.
Following is a more detailed discussion of the present invention which is exemplified by measurements of the areal distribution of the transcutaneous oxygen concentration and the areal distribution of the oxygen flux through the skin, this does not imply that the invention is restricted to this specific purpose, the advantages obtained by this procedure will be fully applicable in the case of other medical or biological quantities and parameters. With a suitably chosen luminescent indicator it will be possible, for example, to measure the subcutaneous CO
2
concentration or distribution of the CO
2
flux through the skin. The system of the invention could also be employed for determining the areal distribution of the concentration or flux of ions, if the sensor film which is applied to the measuring surface, includes a luminescent indicator responding to the ion in question.
Use of the applicator tube to be placed on the measuring surface will result in an unambiguously defined optical configuration yielding reproducible measurement results. With its elastic rim that is in elastic contact with the sensor film, and its constant distance to the measuring surface given by the length of the tube, the applicator tube serves to protect the sensitive detection unit from straylight or undesirable background radiation. This is also true for uneven surfaces onto which the elastic rim fits closely.
The system is particularly suitable for use with curved measuring surfaces, for example, for measuring subcutaneous oxygen concentrations in a patient's limbs, where the detection means preferably includes a unit for determining the local fluorescence decay time or a derived quantity. To obtain an imaging technique that is independent of inhomogeneities of the distribution of the luminescent indicator in the s
Hartmann Paul
Ziegler Werner
Dykema Gossett PLLC
F. Hoffman-La Roche AG
Nasser Robert L.
Natnithithadha Navin
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