WO1996003073A1 - Process for visualizing tissue metabolism using oxygen-17 - Google Patents
Process for visualizing tissue metabolism using oxygen-17 Download PDFInfo
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- WO1996003073A1 WO1996003073A1 PCT/US1994/008436 US9408436W WO9603073A1 WO 1996003073 A1 WO1996003073 A1 WO 1996003073A1 US 9408436 W US9408436 W US 9408436W WO 9603073 A1 WO9603073 A1 WO 9603073A1
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R33/00—Arrangements or instruments for measuring magnetic variables
- G01R33/20—Arrangements or instruments for measuring magnetic variables involving magnetic resonance
- G01R33/44—Arrangements or instruments for measuring magnetic variables involving magnetic resonance using nuclear magnetic resonance [NMR]
- G01R33/48—NMR imaging systems
- G01R33/54—Signal processing systems, e.g. using pulse sequences ; Generation or control of pulse sequences; Operator console
- G01R33/56—Image enhancement or correction, e.g. subtraction or averaging techniques, e.g. improvement of signal-to-noise ratio and resolution
- G01R33/5601—Image enhancement or correction, e.g. subtraction or averaging techniques, e.g. improvement of signal-to-noise ratio and resolution involving use of a contrast agent for contrast manipulation, e.g. a paramagnetic, super-paramagnetic, ferromagnetic or hyperpolarised contrast agent
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
- A61K49/00—Preparations for testing in vivo
- A61K49/06—Nuclear magnetic resonance [NMR] contrast preparations; Magnetic resonance imaging [MRI] contrast preparations
- A61K49/18—Nuclear magnetic resonance [NMR] contrast preparations; Magnetic resonance imaging [MRI] contrast preparations characterised by a special physical form, e.g. emulsions, microcapsules, liposomes
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R33/00—Arrangements or instruments for measuring magnetic variables
- G01R33/20—Arrangements or instruments for measuring magnetic variables involving magnetic resonance
- G01R33/44—Arrangements or instruments for measuring magnetic variables involving magnetic resonance using nuclear magnetic resonance [NMR]
- G01R33/46—NMR spectroscopy
- G01R33/465—NMR spectroscopy applied to biological material, e.g. in vitro testing
Definitions
- the present invention relates to a process for visualizing tissue metabolism in a subject using a magnetic resonance imaging system and oxygen-17.
- Oxygen-17 is injected into the peritoneal cavity of a subject as a gas or contained in microbubbles.
- Magnetic resonance imaging systems rely on the tendency of atomic nuclei possessing magnetic moments to align their spins with an external magnetic field. Because only nuclei with odd numbers of nucleons have a magnetic moment, only those nuclei can be detected and imaged using magnetic resonance. At present, hydrogen with one nucleon, a proton, in its nucleus is the element of choice for diagnostic tissue imaging.
- Magnetic resonance imaging data obtained using non-metabolically derived hydrogen although useful in providing information on tissue perfusion (blood flow to that tissue) and structure, are of limited use in detecting the metabolism of those tissues. Visualization of tissue metabolism using magnetic resonance imaging can be obtained by imaging H 2 0 formed during aerobic metabolism.
- H 2 0 is formed as a byproduct of oxygen consumption.
- the metabolic formation of H 2 0 can be detected using isotopes of oxygen.
- the most common isotope of oxygen, oxygen-16 has an even number of nucleons and, thus, cannot be imaged in a magnetic imaging system.
- Another isotope of oxygen, oxygen-15 is unstable with a short half life (radioactive) and its use would expose a subject to potentially harmful radiation.
- the oxygen isotope, oxygen-17 ( 17 0 2 ) is stable, has an odd nucleon number and is suitable for use in magnetic resonance imaging. Further, because 17 0 2 can be detected by a proton magnetic resonance imaging in the form of H 2 " ⁇ , the use of 17 0 2 provides data on the metabolic state of imaged tissues.
- 17 0 2 is administered intravenously in an artificial blood composition comprising perfluorohydrocarbons as the oxygen carrier. See U.S. Patent No. 4,996,041, the disclosure of which is incorporated herein by reference. Because of the limited oxygen-carrying capacity of perfluorohydrocarbons, that process requires loading the patient with large volumes of the artificial blood composition. Further, the effects of artificial blood compositions per se on tissue metabolism are not yet known.
- PCT Patent Publication No. WO 91/07990 reports the use of an inhalant gas containing 17 0 2 as a nuclear magnetic imaging agent. That process requires large volumes of expensive 17 0 2 gas and is limited in its use to subjects having normal respiratory function. Large volumes of inhalant gas are needed in that process because only a small portion of the inhaled gas comes in contact with the blood.
- Oxygen absorption into the blood can occur through from the peritoneal cavity. Wilks, S., J. APPI. Physics. 14:311 (1939) and Van Liew et al., Microvascular Research. 1:257 (1969). Not only does the peritoneal cavity offer a large surface area for absorption (equivalent to that of skin) , but also the membrane surfaces in the peritoneal cavity (the peritoneum and the omenturn) are readily supplied with capillary vessels that provide ready access to the blood. Indeed, anoxic animals (animals with a deficiency in blood oxygen tension) can be successfully oxygenated with oxygen delivered into the peritoneal cavity. Bilge et al., Biomaterials. Artificial Cells. Artificial Organs. 17(4) :413 (1989).
- the present invention provides a process of visualizing tissue metabolism of a subject comprising injecting 17 0 2 into the peritoneal cavity of a subject and detecting metabolically formed H 2 17 0 using a magnetic resonance imaging system.
- a benefit of the process of the present invention is the provision of an efficient process of introducing 17 0 2 into tissues for imaging in a magnetic imaging system to detect localized metabolic activity under physiological conditions by monitoring the in vivo metabolism of oxygen via the production and detection of H 2 17 0.
- a further benefit of the present invention is the provision of an efficient process of introducing 17 0 2 into tissues for imaging in a magnetic imaging system to detect localized metabolic activity in subjects having respiratory dysfunction.
- the present invention is directed to a process of visualizing tissue metabolism in a subject comprising the steps of: a) injecting a gas containing an effective imaging amount of 17 0 2 into the peritoneal cavity of the subject; b) maintaining the subject for a time period sufficient for the 17 0 2 to be (i) absorbed into the blood stream of the subject, (ii) distributed throughout the tissues of the subject, and (iii) converted to H 2 "0; and c) detecting the H 2 17 0 with a magnetic resonance imaging system thereby visualizing the tissue metabolism.
- the gas containing 17 0 2 is air, oxygen, carbon dioxide or a mixture of oxygen and carbon dioxide.
- the gas is a mixture of about 50 percent by volume oxygen and about 50 percent by volume carbon dioxide.
- the carbon dioxide can itself contain 17 0 2 and have the formula C 17 0 2 .
- the present invention contemplates a process of visualizing tissue metabolism in a subject comprising the steps of: a) injecting microbubbles of substantially uniform diameter that contain an effective imaging amount of 17 0 2 into the peritoneal cavity of the subject; b) maintaining the subject for a time period sufficient for the microbubbles containing an effective imaging amount of 17 0 2 to be (i) absorbed into the blood of the subject, (ii) distributed throughout the tissues of the subject, and (iii) for the 17 0 2 to be converted to H 2 "0; and c) detecting the H 2 17 0 with a magnetic resonance imaging system thereby visualizing the tissue metabolism.
- the microbubbles are formed by subjecting a viscous solution in an atmosphere of 17 0 2 to frequency energy in the range of from about 5,000 Hz to about 30,000 Hz for a time period sufficient to form, but not stabilize the microbubbles.
- the viscous solution is preferably an aqueous protein solution comprising from about 2 percent by weight to about 10 percent by weight of albumin.
- the viscous solution comprises an aqueous protein solution of about 5 percent by weight of albumin.
- the present invention relates to a process of visualizing tissue metabolism using magnetic resonance imaging of H 2 17 0.
- a gas containing an effective imaging amount of 17 0 2 is injected into the peritoneal cavity of a subject; the subject is maintained for a period of time sufficient for the 17 0 2 to be absorbed into the blood stream, distributed to tissues throughout the subject, and converted to H 2 17 0.
- the H 2 17 0 formed in a particular tissue is visualized by imaging the tissue with a magnetic resonance imaging system.
- the term "subject” refers to a mammal and includes human as well as non-human mammals.
- the gas containing 17 0 2 can be air (a mixture of about 20 percent by volume oxygen and about 80 percent by volume nitrogen) , oxygen ( 16 0 2 or l ⁇ 0 2 ) , carbon dioxide or a mixture of carbon dioxide and oxygen.
- Each of those gases can contain from about zero to about 10 percent by volume water as a vapor.
- the water vapor comprises from about 4 percent by volume to about 8 percent by volume of the gas.
- Gases for use in the present invention are commercially available. By way of example, a mixtures of "0 2 and 17 0 2 is commercially available from Isotec Inc., Miamisburg, OH.
- the gas contains an effective imaging amount of 17 0 2 .
- An effective imaging amount of 17 0 2 is that amount necessary to provide tissue visualization of formed H 2 17 0 with magnetic resonance imaging. Means for determining an effective imaging amount in a particular subject will depend, as is well known in the art, on the nature of the gas used, the mass of the subject being imaged, the sensitivity of the magnetic resonance imaging system and the like.
- the gas containing 17 0 2 is a mixture of oxygen and carbon dioxide.
- the oxygen component of such a mixture can comprise any combination of 16 0 2 , "0 2 and 17 0 2 so long as an injected volume of the mixture provides an effective imaging amount of 17 0 2 .
- the carbon dioxide component of such a mixture can contain any combination of C" ⁇ 2 and C 17 0 2 so long as an injected volume of the mixture provides an effective imaging amount of 17 0 2 .
- the volume of gas injected into the peritoneal cavity of a particular subject is selected inter alia on the basis of subject size and gas composition.
- the only limitation on injected volume is that the particular volume selected not adversely affect the subject and that the volume contain an effective imaging amount of 17 0 2 .
- a sufficient time period is from about 20 minutes to about 90 minutes and, preferably from about 20 minutes to about 60 minutes.
- Tissue H 2 17 0 is visualized by imaging that tissue with a magnetic resonance imaging system.
- the visualization of tissue H 2 17 0 can be accomplished with commercially available magnetic imaging systems such as a General Electric 1.5 T Signa imaging system [IH resonant frequency 63.9 megahertz (MHz)].
- Commercially available magnetic resonance imaging systems are typically characterized by the magnetic field strength used, with a field strength of 2.0 Telsa as the current maximum and 0.2 Telsa as the current minimum.
- each detected nucleus has a characteristic frequency.
- the resonance frequency for hydrogen is 42.57 MHz; for phosphorus-31 is 17.24 MHz; and for sodium-23 is 11.26 MHz.
- the present invention relates to a process of visualizing tissue metabolism using magnetic imaging of H 2 17 0 comprising the steps of: a) injecting microbubbles of substantially uniform diameter that contain an effective imaging amount of 17 0 2 into the peritoneal cavity of a subject, wherein said microbubbles are formed by subjecting a viscous solution in an atmosphere of 17 0 2 to frequency energy in the range of from about 5,000 Hz to about 30,000 Hz for a time period sufficient to form said microbubbles; b) maintaining said subject for a time period sufficient for said microbubbles containing an effective imaging amount of 17 0 2 to be (i) absorbed into the blood stream of said subject, (ii) distributed throughout the tissues of said subject, and (iii) for said 17 0 2 to be converted to H 2 "0; and c) detecting said H 2 17 0 with a magnetic resonance imaging system thereby visualizing said tissue metabolism.
- Microbubbles containing 17 0 2 are formed by introducing 17 0 2 into a viscous solution by subjecting the viscous solution to high frequency ultrasonic energy of from about 5,000 Hz to about 30,000 Hz for a time period sufficient to form microbubbles having a diameter of from about 2 microns to about 20 microns and, preferably from about 2 microns to about 4 microns.
- the time period depends as is well known in the art upon the particular ultrasonic energy used.
- a procedure for forming microbubbles from viscous solutions can be found in U.S. Patent Nos. 4,572,203 and 4,774,958, the disclosures of which are incorporated herein by reference.
- Exemplary viscous solutions include aqueous media having dissolved or suspended therein from about 40 percent by weight to about 80 percent by weight of a biocompatible polymer such as dextrose or sorbitol.
- a biocompatible polymer such as dextrose or sorbitol.
- a viscous solution is an aqueous protein solution comprising from about 2 percent by weight to about 10 percent by weight of a biocompatible protein such as albumin.
- a biocompatible protein such as albumin.
- the aqueous protein solution comprises about 5 percent by weight albumin.
- Microbubbles formed from such a 5 percent by weight albumin solution have a diameter of from about 2 microns to about 4 microns.
- the viscous solution can further comprise nutrients such as glucose and electrolytes such as sodium, chloride, potassium, calcium and the like.
- nutrients such as glucose and electrolytes such as sodium, chloride, potassium, calcium and the like.
- the high frequency energy level used to form microbubbles is selected so as to form unstable microbubbles of a uniform diameter, which microbubbles break up after injection into the peritoneal cavity releasing 17 0 2 into the peritoneal cavity.
- the method of microbubble formation used with the present invention does not involve heat or chemical denaturation and stabilization of formed microbubbles.
- microbubbles for use in the present invention are formed using high frequency energy in the range of from about 5,000 Hz. to about 15,000 Hz.
- a 400 gram Sprague Dawley rat was anesthetized with sodium pentobarbital (30mg/kg) . About 30 milliliters (ml) of a 50 percent by volume mixture of carbon dioxide and oxygen (50 percent by volume 1 0 2 and 50 percent by volume C l ⁇ 0 2 ) was injected into the peritoneal cavity. Volume changes were analyzed every twenty minutes for a period of 100 minutes after injection. Visualization of H 2 17 0 in brain tissue was monitored over the same period of time.
- Magnetic resonance images of the rat brain were performed using a 1.5 Tesla GE Signa system. Imaging was enhanced by the use of a 10 cm solenoid coil placed orthogonal to the field of the Signa. Dilutions of H 2 17 0 in 5mm tubes were placed in the field as references to observe any field changes that might occur during imaging.
- the slice thickness of the images was 3mm and the images were acquired over a period of 11 minutes. Measurements of contrast at two reference sites in the hypothalamus and cortex were made.
- H 2 17 0 was observed by magnetic resonance imaging 40 minutes after injection. Ninety minutes after injection, no H 2 17 0 could be visualized in the brain.
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Abstract
The present invention provides a process for visualizing tissue metabolism in a subject comprising injecting 17O2 into the peritoneal cavity of a subject and detecting formed H217O in tissues of the subject. The 17O2 is injected as a gas or as microbubbles formed from an aqueous protein solution.
Description
PROCESS FOR VISUALIZING TISSUE METABOLISM USING OXYGEN-17
Description
Technical rigid Qt the Invention
The present invention relates to a process for visualizing tissue metabolism in a subject using a magnetic resonance imaging system and oxygen-17. Oxygen-17 is injected into the peritoneal cavity of a subject as a gas or contained in microbubbles.
Background of the Invention
Magnetic resonance imaging systems rely on the tendency of atomic nuclei possessing magnetic moments to align their spins with an external magnetic field. Because only nuclei with odd numbers of nucleons have a magnetic moment, only those nuclei can be detected and imaged using magnetic resonance. At present, hydrogen with one nucleon, a proton, in its nucleus is the element of choice for diagnostic tissue imaging.
Magnetic resonance imaging data obtained using non-metabolically derived hydrogen, although useful in providing information on tissue perfusion (blood flow to that tissue) and structure, are of limited use in detecting the metabolism of those tissues. Visualization of tissue metabolism using magnetic resonance imaging can be obtained by imaging H20 formed during aerobic metabolism.
Under aerobic conditions, H20 is formed as a byproduct of oxygen consumption. The metabolic formation of H20 can be detected using isotopes of oxygen. The most common isotope of oxygen, oxygen-16, has an even number of nucleons and, thus, cannot be imaged in a magnetic imaging system. Another isotope of
oxygen, oxygen-15, is unstable with a short half life (radioactive) and its use would expose a subject to potentially harmful radiation.
The oxygen isotope, oxygen-17 (1702) , is stable, has an odd nucleon number and is suitable for use in magnetic resonance imaging. Further, because 1702 can be detected by a proton magnetic resonance imaging in the form of H2"θ, the use of 1702 provides data on the metabolic state of imaged tissues.
A magnetic resonance imaging process using 1702 has been previously reported. In accordance with that process, 1702 is administered intravenously in an artificial blood composition comprising perfluorohydrocarbons as the oxygen carrier. See U.S. Patent No. 4,996,041, the disclosure of which is incorporated herein by reference. Because of the limited oxygen-carrying capacity of perfluorohydrocarbons, that process requires loading the patient with large volumes of the artificial blood composition. Further, the effects of artificial blood compositions per se on tissue metabolism are not yet known.
PCT Patent Publication No. WO 91/07990 reports the use of an inhalant gas containing 1702 as a nuclear magnetic imaging agent. That process requires large volumes of expensive 1702 gas and is limited in its use to subjects having normal respiratory function. Large volumes of inhalant gas are needed in that process because only a small portion of the inhaled gas comes in contact with the blood.
Oxygen absorption into the blood can occur through from the peritoneal cavity. Wilks, S., J. APPI. Physics. 14:311 (1939) and Van Liew et al., Microvascular Research. 1:257 (1969). Not only does the peritoneal cavity offer a large surface area for
absorption (equivalent to that of skin) , but also the membrane surfaces in the peritoneal cavity (the peritoneum and the omenturn) are readily supplied with capillary vessels that provide ready access to the blood. Indeed, anoxic animals (animals with a deficiency in blood oxygen tension) can be successfully oxygenated with oxygen delivered into the peritoneal cavity. Bilge et al., Biomaterials. Artificial Cells. Artificial Organs. 17(4) :413 (1989).
Brief Summary of the Invention
The present invention provides a process of visualizing tissue metabolism of a subject comprising injecting 1702 into the peritoneal cavity of a subject and detecting metabolically formed H2 170 using a magnetic resonance imaging system. A benefit of the process of the present invention is the provision of an efficient process of introducing 1702 into tissues for imaging in a magnetic imaging system to detect localized metabolic activity under physiological conditions by monitoring the in vivo metabolism of oxygen via the production and detection of H2 170. A further benefit of the present invention is the provision of an efficient process of introducing 1702 into tissues for imaging in a magnetic imaging system to detect localized metabolic activity in subjects having respiratory dysfunction.
In one aspect, the present invention is directed to a process of visualizing tissue metabolism in a subject comprising the steps of: a) injecting a gas containing an effective imaging amount of 1702 into the peritoneal cavity of the subject; b) maintaining the subject for a time period sufficient for the 1702 to be (i) absorbed into the blood stream of the subject, (ii) distributed
throughout the tissues of the subject, and (iii) converted to H2"0; and c) detecting the H2 170 with a magnetic resonance imaging system thereby visualizing the tissue metabolism.
The gas containing 1702 is air, oxygen, carbon dioxide or a mixture of oxygen and carbon dioxide. In a preferred embodiment, the gas is a mixture of about 50 percent by volume oxygen and about 50 percent by volume carbon dioxide. The carbon dioxide can itself contain 1702 and have the formula C1702.
In another aspect, the present invention contemplates a process of visualizing tissue metabolism in a subject comprising the steps of: a) injecting microbubbles of substantially uniform diameter that contain an effective imaging amount of 1702 into the peritoneal cavity of the subject; b) maintaining the subject for a time period sufficient for the microbubbles containing an effective imaging amount of 1702 to be (i) absorbed into the blood of the subject, (ii) distributed throughout the tissues of the subject, and (iii) for the 1702 to be converted to H2"0; and c) detecting the H2 170 with a magnetic resonance imaging system thereby visualizing the tissue metabolism.
The microbubbles are formed by subjecting a viscous solution in an atmosphere of 1702 to frequency energy in the range of from about 5,000 Hz to about 30,000 Hz for a time period sufficient to form, but not stabilize the microbubbles. The viscous solution is preferably an aqueous protein solution comprising from about 2 percent by weight to about 10 percent by weight of albumin. In a more preferred embodiment, the viscous
solution comprises an aqueous protein solution of about 5 percent by weight of albumin.
Detailed Description of the Invention
A. Gas Containing 10.
The present invention relates to a process of visualizing tissue metabolism using magnetic resonance imaging of H2 170. In accordance with that process, a gas containing an effective imaging amount of 1702 is injected into the peritoneal cavity of a subject; the subject is maintained for a period of time sufficient for the 1702 to be absorbed into the blood stream, distributed to tissues throughout the subject, and converted to H2 170. The H2 170 formed in a particular tissue is visualized by imaging the tissue with a magnetic resonance imaging system.
As used herein, the term "subject" refers to a mammal and includes human as well as non-human mammals.
The gas containing 1702 can be air (a mixture of about 20 percent by volume oxygen and about 80 percent by volume nitrogen) , oxygen (1602 or lβ02) , carbon dioxide or a mixture of carbon dioxide and oxygen. Each of those gases can contain from about zero to about 10 percent by volume water as a vapor. Preferably, the water vapor comprises from about 4 percent by volume to about 8 percent by volume of the gas. Gases for use in the present invention are commercially available. By way of example, a mixtures of "02 and 1702 is commercially available from Isotec Inc., Miamisburg, OH.
The gas contains an effective imaging amount of 1702. An effective imaging amount of 1702 is that amount necessary to provide tissue visualization of
formed H2 170 with magnetic resonance imaging. Means for determining an effective imaging amount in a particular subject will depend, as is well known in the art, on the nature of the gas used, the mass of the subject being imaged, the sensitivity of the magnetic resonance imaging system and the like.
In a preferred embodiment, the gas containing 1702 is a mixture of oxygen and carbon dioxide. The oxygen component of such a mixture can comprise any combination of 1602, "02 and 1702 so long as an injected volume of the mixture provides an effective imaging amount of 1702. Additionally or alternatively, the carbon dioxide component of such a mixture can contain any combination of C"θ2 and C1702 so long as an injected volume of the mixture provides an effective imaging amount of 1702.
The advantage of using carbon dioxide is that C02 is absorbed from the peritoneal cavity into the blood stream more readily than oxygen. Further, carbon dioxide enhances the absorption of oxygen across the membranes lining the peritoneal cavity.
The volume of gas injected into the peritoneal cavity of a particular subject is selected inter alia on the basis of subject size and gas composition. The only limitation on injected volume is that the particular volume selected not adversely affect the subject and that the volume contain an effective imaging amount of 1702.
After injection of a gas containing 1702, the subject is maintained for a time period sufficient for (1) the injected 1702 to be absorbed from the peritoneal cavity into the blood, (2) the absorbed 1702 to be distributed throughout the subject and enter the tissues of the subject, and (3) the 1702 in the tissue to be converted to H2 170. Typically, a sufficient time
period is from about 20 minutes to about 90 minutes and, preferably from about 20 minutes to about 60 minutes.
Tissue H2 170 is visualized by imaging that tissue with a magnetic resonance imaging system. The visualization of tissue H2 170 can be accomplished with commercially available magnetic imaging systems such as a General Electric 1.5 T Signa imaging system [IH resonant frequency 63.9 megahertz (MHz)]. Commercially available magnetic resonance imaging systems are typically characterized by the magnetic field strength used, with a field strength of 2.0 Telsa as the current maximum and 0.2 Telsa as the current minimum.
For a given field strength, each detected nucleus has a characteristic frequency. For example, at a field strength of 1.0 Telsa, the resonance frequency for hydrogen is 42.57 MHz; for phosphorus-31 is 17.24 MHz; and for sodium-23 is 11.26 MHz.
B. Microbubbles Containing 17Q 2
In another aspect, the present invention relates to a process of visualizing tissue metabolism using magnetic imaging of H2 170 comprising the steps of: a) injecting microbubbles of substantially uniform diameter that contain an effective imaging amount of 1702 into the peritoneal cavity of a subject, wherein said microbubbles are formed by subjecting a viscous solution in an atmosphere of 1702 to frequency energy in the range of from about 5,000 Hz to about 30,000 Hz for a time period sufficient to form said microbubbles; b) maintaining said subject for a time period sufficient for said microbubbles containing an effective imaging amount of 1702 to be (i) absorbed into the blood stream of said subject, (ii) distributed
throughout the tissues of said subject, and (iii) for said 1702 to be converted to H2"0; and c) detecting said H2 170 with a magnetic resonance imaging system thereby visualizing said tissue metabolism.
Microbubbles containing 1702 are formed by introducing 1702 into a viscous solution by subjecting the viscous solution to high frequency ultrasonic energy of from about 5,000 Hz to about 30,000 Hz for a time period sufficient to form microbubbles having a diameter of from about 2 microns to about 20 microns and, preferably from about 2 microns to about 4 microns. The time period depends as is well known in the art upon the particular ultrasonic energy used. A procedure for forming microbubbles from viscous solutions can be found in U.S. Patent Nos. 4,572,203 and 4,774,958, the disclosures of which are incorporated herein by reference.
Exemplary viscous solutions include aqueous media having dissolved or suspended therein from about 40 percent by weight to about 80 percent by weight of a biocompatible polymer such as dextrose or sorbitol. U.S. Patent Nos. 4,572,203 and 4,774,958.
In a preferred embodiment, a viscous solution is an aqueous protein solution comprising from about 2 percent by weight to about 10 percent by weight of a biocompatible protein such as albumin. Preferably the aqueous protein solution comprises about 5 percent by weight albumin. Microbubbles formed from such a 5 percent by weight albumin solution have a diameter of from about 2 microns to about 4 microns. U.S. Patent No. 4,774,958.
The viscous solution can further comprise nutrients such as glucose and electrolytes such as sodium, chloride, potassium, calcium and the like.
The high frequency energy level used to form microbubbles is selected so as to form unstable microbubbles of a uniform diameter, which microbubbles break up after injection into the peritoneal cavity releasing 1702 into the peritoneal cavity.
Thus, unlike the method of microbubble formation disclosed in U.S. Patent Nos. 4,572,203 and 4,774,958, the method of microbubble formation used with the present invention does not involve heat or chemical denaturation and stabilization of formed microbubbles.
In a preferred embodiment, microbubbles for use in the present invention are formed using high frequency energy in the range of from about 5,000 Hz. to about 15,000 Hz.
The following example illustrates a particular embodiment of the present invention and is not limiting of the specification and claims in any way.
Example
EXAMPLE 1: Magnetic Resonance Imaging of Rat Brain
A 400 gram Sprague Dawley rat was anesthetized with sodium pentobarbital (30mg/kg) . About 30 milliliters (ml) of a 50 percent by volume mixture of carbon dioxide and oxygen (50 percent by volume 102 and 50 percent by volume Clβ02) was injected into the peritoneal cavity. Volume changes were analyzed every twenty minutes for a period of 100 minutes after injection. Visualization of H2 170 in brain tissue was monitored over the same period of time.
Direct measurement of volume changes indicated that 28 percent of the oxygen from the gas mixture of carbon dioxide and oxygen was absorbed by 60 minutes after injection.
Magnetic resonance images of the rat brain were performed using a 1.5 Tesla GE Signa system. Imaging was enhanced by the use of a 10 cm solenoid coil placed orthogonal to the field of the Signa. Dilutions of H2 170 in 5mm tubes were placed in the field as references to observe any field changes that might occur during imaging.
Scout images of the brain at repetition times of 3000 milliseconds (ms) and excitation times of 60 ms provided heavily "T2 weighted" images. The slice thickness of the images was 3mm and the images were acquired over a period of 11 minutes. Measurements of contrast at two reference sites in the hypothalamus and cortex were made.
The presence of H2 170 was observed by magnetic resonance imaging 40 minutes after injection. Ninety minutes after injection, no H2 170 could be visualized in the brain.
Although the present invention has been described in terms of certain preferred embodiments, and exemplified with respect thereto, one skilled in the art will readily appreciate that various modifications, changes, omissions and substitutions can be made without departing from the spirit thereof.
Claims
1. A process of visualizing tissue metabolism in a subject comprising the steps of: a) injecting a gas containing an effective imaging amount of 1702 into the peritoneal cavity of said subject; b) maintaining said subject for a time period sufficient for said 1702 to be (i) absorbed into the blood stream of said subject, (ii) distributed throughout the tissues of said subject, and (iii) converted to H2 170; and c) detecting said H2 170 with a magnetic resonance imaging system thereby visualizing said tissue metabolism.
2. The process according to claim 2 wherein said gas is air, oxygen, carbon dioxide or a mixture of oxygen and carbon dioxide.
3. The process according to claim 2 wherein said carbon dioxide is C1702.
4. The process according to claim 1 wherein said gas is a mixture of about 50 percent by volume oxygen and about 50 percent by volume carbon dioxide.
5. A process of visualizing tissue metabolism in a subject comprising the steps of: a) injecting microbubbles of substantially uniform diameter that contain an effective imaging amount of 1702 into the peritoneal cavity of a ' subject, wherein said microbubbles are formed by subjecting viscous solution in an atmosphere of 1702 to high frequency energy in the range of from about 5,000 Hz to about 15,000 Hz for a time period sufficient to form said microbubbles; b) maintaining said subject for a time period sufficient for said microbubbles containing an effective imaging amount of 1702 to be (i) absorbed into the blood stream of said subject, (ii) distributed throughout the tissues of said subject, and (iii) for said 1702 to be converted to H2 170; and c) detecting said H2 170 with a magnetic resonance imaging system thereby visualizing said tissue metabolism.
6. The process according to claim 5 wherein said viscous solution is an aqueous protein solution comprising from about 2 percent by weight to about 10 percent by weight of albumin.
7. The process according to claim 6 wherein said aqueous protein solution comprises about 5 percent by weight of albumin.
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US07/869,547 US5339814A (en) | 1992-04-14 | 1992-04-14 | Process for visualizing tissue metabolism using oxygen-17 |
PCT/US1994/008436 WO1996003073A1 (en) | 1992-04-14 | 1994-07-26 | Process for visualizing tissue metabolism using oxygen-17 |
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US07/869,547 US5339814A (en) | 1992-04-14 | 1992-04-14 | Process for visualizing tissue metabolism using oxygen-17 |
PCT/US1994/008436 WO1996003073A1 (en) | 1992-04-14 | 1994-07-26 | Process for visualizing tissue metabolism using oxygen-17 |
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WO (1) | WO1996003073A1 (en) |
Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
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US4849210A (en) * | 1985-05-08 | 1989-07-18 | Molecular Biosystems, Inc. | Magnetic resonance imaging of liver and spleen with superparamagnetic contrast agents |
US4993415A (en) * | 1988-08-19 | 1991-02-19 | Alliance Pharmaceutical Corp. | Magnetic resonance imaging with perfluorocarbon hydrides |
US4996041A (en) * | 1988-08-19 | 1991-02-26 | Toshiyuki Arai | Method for introducing oxygen-17 into tissue for imaging in a magnetic resonance imaging system |
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1994
- 1994-07-26 WO PCT/US1994/008436 patent/WO1996003073A1/en active Application Filing
Patent Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4849210A (en) * | 1985-05-08 | 1989-07-18 | Molecular Biosystems, Inc. | Magnetic resonance imaging of liver and spleen with superparamagnetic contrast agents |
US4993415A (en) * | 1988-08-19 | 1991-02-19 | Alliance Pharmaceutical Corp. | Magnetic resonance imaging with perfluorocarbon hydrides |
US4996041A (en) * | 1988-08-19 | 1991-02-26 | Toshiyuki Arai | Method for introducing oxygen-17 into tissue for imaging in a magnetic resonance imaging system |
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