Surgery – Diagnostic testing – Detecting nuclear – electromagnetic – or ultrasonic radiation
Reexamination Certificate
2000-01-25
2003-02-04
Lateef, Marvin M. (Department: 3737)
Surgery
Diagnostic testing
Detecting nuclear, electromagnetic, or ultrasonic radiation
C600S473000, C600S477000, C600S310000
Reexamination Certificate
active
06516214
ABSTRACT:
FIELD OF THE INVENTION
The invention is in the field of diffuse optical tomography and stroke.
BACKGROUND OF THE INVENTION
Victims of stroke caused by an ischemic event in the brain can benefit from treatment with recombinant tissue plasminogen activator, a thrombolytic drug, within three hours of the ischemic event. On the other hand, if the stroke is caused by a bleed instead of an ischemic event, thrombolytic drugs are contraindicated. Thus, a quick and efficient means of distinguishing an ischemic event from a bleed in a stroke victim would aid a health care provider in managing the treatment of stroke victims. Furthermore, treatment protocols need to be tailored to individual patients. Therefore, continuous monitoring of cerebral perfusion would enable the health care provider to more effectively guide treatment in a patient with a specific pathology.
Diffuse optical tomography (DOT) refers to various non-invasive methods of imaging different tissues of a body or organ. Generally, DOT relies on the emission of light from a light source into the body, then detecting the light scattered from various tissues of the body. For example, since light scattered by hemoglobin in blood differs from light scattered by other tissues, DOT has been applied to the imaging of blood within the body. In addition, because the absorption of light by deoxyhemoglobin is different from the absorption of light by oxyhemoglobin, DOT has been used to locate areas of high or low oxygenation in the body by determining decreases or increases in the intensity of scattered light. However, the application of DOT in various imaging scenarios in the clinic has been limited by the inability to detect light scattered by deep tissues. This can be due to either the inability of the emitted light to reach deep tissues, or the inability to detect and measure the weak intensity of light scattered by the deep tissues (i.e., no measurable contrast between scattered light and background).
SUMMARY OF THE INVENTION
The invention is based on the recognition that ischemic events deep in the brain can be detected using DOT to monitor collateral blood flow abnormalities in cortical regions of the brain arising from the deep ischemic events using blood-borne tracer dyes (also called contrast agents or tracers). By extrapolating information from the cortical regions, deep ischemic events as well as cortical ischemic events in the brain can be monitored even if the light used for DOT does not penetrate into the deep portions of the brain, or if the contrast in the light scattered from blood and solid tissues in the deep portions of the brain is not easily detected.
The invention is also based on the recognition that a brain bleed can be imaged by DOT using a blood-borne tracer dye and detecting a localized region of a lower concentration of dye or of no dye at all, as compared to an adjacent region in the brain. The imaging of a brain bleed is made possible by recognizing that blood vessel constriction and clotting at the site of the bleed will inhibit the dye from infiltrating the region of the bleed while adjacent regions are unaffected. In addition, the use of a tracer dye increases the contrast in light scattered by blood versus solid tissue deep in the brain, thereby allowing blood volume to be imaged even where the intensity of scattered light is weak.
Accordingly, the invention features a method of detecting an ischemic event in a brain in a subject, using a first criterion, by (1) administering a dye bolus into the bloodstream of the subject; (2) directing light into the brain of the subject; (3) detecting light emitted from the brain over time at a detection location, the dye being present in the brain for at least a portion of the detection time, and the light emitted from the brain in the presence of the dye being different from the light emitted from the brain in the absence of the dye, the magnitude of the difference corresponding to the concentration of the dye; (3) establishing a reference time period corresponding to the time a peak concentration of a dye bolus takes to reach the detection location in a normal brain; (4) determining a subject time period corresponding to the time a peak concentration of the dye bolus takes to reach the detection location in the subject; and (5) comparing the subject time period with the reference time period, where a subject time period 1 or more seconds longer than the reference time period indicates an ischemic event in the brain. If the subject time period is 2 or more seconds longer than the reference time period, then an ischemic event in a deep portion of the brain is indicated.
In another aspect, the invention includes a method of detecting an ischemic event in a brain in a subject, using a second criterion, by (1) administering a dye bolus into the bloodstream of the subject; (2) directing light into the brain of the subject; (3) detecting light emitted from the brain over time at a detection location, the dye being present in the brain for at least a portion of the detection time, and the light emitted from the brain in the presence of dye being different from the light emitted from the brain in the absence of the dye, the magnitude of the difference corresponding to the concentration of the dye; (4) establishing a peak reference concentration of a dye bolus administered to a subject with a normal brain at the detection location; (5) determining a peak subject concentration of the dye bolus at the detection location; and (6) comparing the peak subject concentration with the peak reference concentration, where a peak subject concentration below the peak reference concentration indicates an ischemic event in the brain. If the peak subject concentration is below the peak reference concentration but at least 50% of the peak reference concentration, then an ischemic event in a deep portion of the brain is indicated.
The invention also includes a method of detecting an ischemic event in a brain in a subject, using a third criterion, by (1) administering a dye bolus into the bloodstream of the subject; (2) directing light into the brain of the subject; (3) detecting light emitted from the brain over time at a detection location, the dye being present in the brain for at least a portion of the detection time, and the light emitted from the brain in the presence of dye being different from the light emitted from the brain in the absence of the dye, the magnitude of the difference corresponding to the concentration of the dye; (4) establishing a reference time period corresponding to the time for the concentration of a dye bolus to vary from a threshold (e.g., 10, 5, 2, or 1% by volume) concentration to a peak concentration and back to the threshold concentration at the detection location in a normal brain; (5) determining a subject time period corresponding to the time for the concentration of the dye to vary from the threshold concentration to a peak concentration and back to the threshold concentration at the detection location; and (6) comparing the subject time period with the reference time period, where a subject time period longer than the reference time period indicates an ischemic event in the brain. If the subject time period is at least 2 seconds longer than the reference time period, then an ischemic event in a deep portion of the brain is indicated.
In still another aspect, the invention includes a method of detecting an ischemic event in a brain in a subject, using a fourth criterion, by (1) administering a dye bolus into the bloodstream of a subject; (2) directing light into the brain of the subject; (3) detecting light emitted from the brain over time at a detection location, the dye being present in the brain for at least a portion of the detection time, and the light emitted from the brain in the presence of the dye being different from the light emitted from the brain in the absence of the dye, the magnitude of the difference corresponding to the concentration of the dye; (4) establishing a reference map of cortical blood flow in a normal brain; (5) obtain
Shah Devaang
The General Hospital Corporation
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