Process and device for non-invasively determining cerebral blood flow by near-infrared spectroscopy
First Claim
1. A process for the noninvasive determination of blood flow, comprising the steps of:
- intravenously administrating a predetermined amount of a tracer substance simultaneously into different regions of a patient, the tracer substance having absorption properties in the near-infrared spectrum;
determining a first dye curve by near-infrared spectroscopy; and
determining a second dye curve by pulse densitometry, wherein the first and second dye curves are determined simultaneously.
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Abstract
A process and device for noninvasive measurement of cerebral blood flow simultaneously determines of a blood flow index which is directly proportional to the blood flow. Cerebral surge kinetics of an intravenously injected indicator dye with absorption properties in the near-infrared spectrum is sensed by near-infrared spectroscopy and the arterial surge kinetics is sensed by pulse densitometry. A device for carrying out this process consists of a multichannel apparatus having at least two near-infrared spectroscopes, each having two pulsed monochromatic light sources, a measuring and a reference wavelength, in the range of the near-infrared spectrum; one or more light sensors connected to a photomultiplier; and a noninvasive measuring device which determines, by pulse densitometry, the concentration of the tracer in the arterial blood of the circulatory system.
91 Citations
17 Claims
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1. A process for the noninvasive determination of blood flow, comprising the steps of:
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intravenously administrating a predetermined amount of a tracer substance simultaneously into different regions of a patient, the tracer substance having absorption properties in the near-infrared spectrum;
determining a first dye curve by near-infrared spectroscopy; and
determining a second dye curve by pulse densitometry, wherein the first and second dye curves are determined simultaneously. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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6. The process according to claim 5, wherein the step of determining the transport function g(t) further comprises varying parameters of the transport function by an interative, nonlinear matching process according to the principle of smallest squares, wherein the squares of differences between the measured cerebral dye curve c(t) and a convolution result of arterial dye curve a(t) are minimized according to the following formula:
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7. The process according to claim 6, further comprising the step of describing the transport function g(t) by a logarithmic normal distribution according to the following formula:
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8. The process according to claim 7, wherein the transport function g(t) for a plurality of intra vascular compartments N having blood circulating there through at varying rates can be represented by the sum of two logarithmic normal distributions according to the formula:
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9. The process according to claim 8, further comprising the step of determining a blood flow index using the transcerebral dye transport function g(t) according to the formula:
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blood flow index=surge maximum/surge time, wherein surge time [s]=t(y % of signal rise)−
t(x % of signal rise)and t is time [s] and x and y are variables that define the beginning and end of a temporal surge interval of the transcerebral transport function being measured.
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10. The process according to claim 5, further comprising the step of quantifying by regional breakdown a relative cerebral blood volume as a product of average transit time (mtt) of transport function g(t) and of the relative blood flow index of the corresponding region.
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11. The process according to claim 3, further comprising the step of performing a regional breakdown of blood circulation measurement by measuring, with near-infrared spectroscopy, the passage of the indicator dye using a plurality of light sensors arranged spatially on the patient.
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12. The process according to claim 2, wherein the cerebral blood flow is detected regionally in different hemispheres of the brain simultaneously by simultaneous measurement using several monochromatic light sources, each light source having one or more subordinate light sensors.
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13. The process according to claim 1, further comprising the step of quantifying cardiac output according to the Stewart-Hamilton equation.
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14. The process according to claim 1, further comprising the step of quantifying intra thoracic blood volume as a product of average transit time (mtt) and cardiac output.
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15. A system for noninvasive determination of cerebral blood flow comprising:
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means for intravenously administrating a predetermined amount of a tracer substance, the tracer substance having absorption properties in the near-infrared spectrum;
a noninvasive pulse densitometry measuring device which measures an arterial dye curve;
a plurality of near-infrared spectroscopes, each said spectroscope having at least two pulsed monochromatic light sources in the wavelength range of the near-infrared spectrum for measuring a cerebral dye curve in each cerebral hemisphere, one light source produces a measuring wavelength at which the tracer substance has a maximum absorption rate, and the other light source produces a reference wavelength at which the tracer substance used has a minimum absorption rate; and
a plurality of light sensors communicating with the light sources, the light sensors being connected to a photomultiplier for separate measurement of a cerebral dye curve for each cerebral hemisphere. - View Dependent Claims (16, 17)
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Specification