Surgery – Diagnostic testing – Detecting nuclear – electromagnetic – or ultrasonic radiation
Reexamination Certificate
1999-05-27
2001-08-28
Smith, Ruth S. (Department: 3737)
Surgery
Diagnostic testing
Detecting nuclear, electromagnetic, or ultrasonic radiation
Reexamination Certificate
active
06280383
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to improvements in the use of magnetic resonance imaging, and more particularly to the study of tissue metabolism through the use of oxygen-16.
The ability to produce excellent images of the internal anatomical structure of living beings using nuclear magnetic resonance signals has been well established. Magnetic resonance imaging (“MRI”) is highly sensitive to the relaxation times of the nuclei emitting a magnetic resonance signal, and different relaxation times are manifested as different contrasts within the image. The tissues within the various organs and structures of a patient exhibit markedly different relaxation times. Diseased and injured tissue can result in changes in relaxation time relative to healthy tissue. Consequently, MRI produces very high contrast images of anatomical structure, in which injured and diseased tissues are clearly delineated from normal tissue.
Only nuclei containing an odd number of nucleons (protons and neutrons) emit a magnetic resonance signal. While the imaging of oxygen could be useful in the study of tissue metabolism, oxygen-16, the most common isotype of oxygen, has an even number of nucleons and cannot be imaged directly by magnetic resonance imaging. Oxygen-15, which contains an odd number of nucleons, is radioactive and potentially dangerous to the patient. Oxygen-17, which also contains an odd number of nucleons, is not radioactive, but is present in only trace amounts. Enriched oxygen-17 has limited availability and is expensive to prepare. U.S. Pat. No. 5,339,814 to Lasker discloses a process for visualizing tissue metabolism using a gas of an effective imaging amount of oxygen-17. U.S. Pat. No. 4,996,041 to Arai et al. discloses a diagnostic imaging agent including a complex of oxygen-17, a biologically acceptable liquid carrier, such as a perfluorinated compound, and an emulsifying agent. These references do not overcome the disadvantages of the use of oxygen-17.
SUMMARY OF THE INVENTION
The present invention is a method of studying tissue metabolism with oxygen-16. First, a magnetic resonance image of the tissue of interest is acquired. Oxygen, predominantly in the form of oxygen-16, is then delivered to the tissue of interest. A magnetic resonance image of the tissue of interest is then acquired when the tissue is in the state of increased oxygenation. The first and second images are compared to determine the effect of the delivery of oxygen on the tissue. Such effects may manifest themselves as changes in image characteristics, such as image contrast, image intensity and the morphology of the tissue in the images. A relative measure of the degree of tissue oxygenation before and after the delivery of oxygen may also be determined based on the changes in the image characteristics. The changes in image characteristics may also be correlated with the amount of oxygen delivered.
Preferably, only trace amounts of oxygen-17 is present in the oxygen delivered. Oxygen substantially in its naturally occurring isotopic proportions is preferably delivered. The oxygen may be administered by inhalation of gaseous oxygen. The tissue may also be directly perfused by gaseous oxygen. The oxygen may also be administered in combination with an oxygen carrier molecule, such as hemoglobin or heme.
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Fonar Corporation
Morgan & Finnegan L.L.P.
Smith Ruth S.
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