# US 5,706,805 A · Apparatus and methodology for determining oxygen tension in biological systems > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 5,706,805 A - Document ID: US5706805A - Status: Granted - Kind: A - Application number: 08/476,566 - Filed: 1995-06-07 - Granted: 1998-01-13 - Earliest claimed: 1993-08-12 - Assignees: Trustees of Dartmouth College - Inventors: Harold M. Swartz; Fuminori Goda; Tadeusz Walczak; Ke Jian Liu; Karsten Mader - Web page: https://patentgrep.com/patent/US5706805A ## CPC - A61B 5/145: Measuring characteristics of blood in vivo, e.g. gas concentration or pH-value {; Measuring characteristics of body fluids or tissues, e.g. interstitial fluid or cerebral tissue} (non-radiation detecting or locating of foreign bodies in blood A61B5/06) - A61B 5/411: {Detecting or monitoring allergy or intolerance reactions to an allergenic agent or substance} - A61B 5/415: {the glands, e.g. tonsils, adenoids or thymus} - A61B 5/416: {the spleen} - A61B 5/418: {lymph vessels, ducts or nodes} - G01R 33/465: applied to biological material, e.g. in vitro testing - G01R 33/60: using electron paramagnetic resonance (G01R33/24, G01R33/62 take precedence) - G01R 33/281: {Means for the use of in vitro contrast agents (G01R33/282 takes precedence; involving use of a contrast agent in MR imaging G01R33/5601; in vivo contrast agents A61K49/0002)} - A61B: DIAGNOSIS; SURGERY; IDENTIFICATION (usefulness limited to only animals A61D) - G01R: MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES (indicating correct tuning of resonant circuits H03J3/12) ## Abstract The invention provides apparatus and methods for measuring oxygen tensions in biological systems utilizing physiologically acceptable paramagnetic material, such as India ink or carbon black, and electron paramagnetic resonance (EPR) oximetry. India ink is introduced to the biological system and exposed to a magnetic field and an electromagnetic field in the 1-2 GHz range. The EPR spectra is then measured at the biological system to determine oxygen concentration. The EPR spectra is determined by an EPR spectrometer that adjusts the resonator to a single resonator frequency to compensate for movements of the biological system, such as a human or animal. The biological system can also include other in vivo tissues, cells, and cell cultures to directly measure pO.sub.2 non-destructively. The paramagnetic material can be used non-invasively or invasively depending on the goals of the pO2 measurement. A detecting inductive element, as part of the EPR spectrometer resonator, is adapted relative to the measurement particularities. ## Claims ### Claim 1 A method for determining oxygen tension in a biological system, comprising the steps of introducing a physiologically acceptable paramagnetic material to a surface of the biological system, said paramagnetic material having electron paramagnetic resonance spectra responsive to the presence of oxygen, protecting the material from sources of oxygen that are outside of the biological system, and determining the oxygen tension from the electron paramagnetic resonance spectra of the material. ### Claim 2 (depends on 1) A method according to claim 1, wherein the step of protecting the material comprises the step of covering the material with a gas impermeable seal. ### Claim 3 (depends on 2) A method according to claim 2, further comprising the step of sealing the seal to the surface with a substantially gas impermeable grease, the grease being disposed between the seal and the surface. ### Claim 4 (depends on 1) A method according to claim 1, further comprising the step of forming the material into a paramagnetic probe having a disc-like shape. ### Claim 5 (depends on 1) A method according to claim 1, wherein the paramagnetic material is selected from the group consisting essentially of carbonaceous materials including India ink, carbon black, coals, and chars. ### Claim 6 (depends on 1) A method according to claim 1, wherein the paramagnetic material is selected from the group consisting essentially of lithium phthalocyanine, India Ink, carbon black and coal. ### Claim 7 (depends on 1) A method according to claim 1, further comprising the step of utilizing human skin as the biological system. ### Claim 8 A method for determining oxygen tension in a biological system, comprising the steps of enclosing a paramagnetic material within an inert carrier, said paramagnetic material having electron paramagnetic resonance spectra responsive to the presence of oxygen, introducing the carrier to within the biological system, and determining the oxygen tension of the biological system from the electron paramagnetic resonance spectra of the material within the carrier, wherein the material is disposed within the carrier during the step of determining. ### Claim 9 (depends on 8) A method according to claim 8, wherein the inert carrier comprises a needle, and further comprising the step of connecting a removal member to the needle and so that the removal member extends from the needle to a position exterior to the biological system, whereby the removal member facilitates removal of the needle from the system. ### Claim 10 (depends on 8) A method according to claim 8, further comprising protecting the biological system from material toxicity by utilizing a carrier that is impermeable to the material. ### Claim 11 (depends on 8) A method according to claim 8, further comprising utilizing a cylindrical disc as the carrier.