# US 7,746,075 B2 · Methods, systems, circuits and computer program products for determining polarization of a gas > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 7,746,075 B2 - Document ID: US7746075B2 - Status: Granted - Kind: B2 - Application number: 11/856,805 - Filed: 2007-09-18 - Published: 2008-01-10 - Granted: 2010-06-29 - Earliest claimed: 2002-05-17 - Assignees: Medi-Physics, Inc. - Inventors: Zivko Djukic; Steve Kadlecek; John Nouls; Ian Nelson; Bastiaan Driehuys - Web page: https://patentgrep.com/patent/US7746075B2 ## CPC - G01R 33/282: {Means specially adapted for hyperpolarisation or for hyperpolarised contrast agents, e.g. for the generation of hyperpolarised gases using optical pumping cells, for storing hyperpolarised contrast agents or for the determination of the polarisation of a hyperpolarised contrast agent} - G01R 33/3628: {Tuning/matching of the transmit/receive coil} - G01R 33/3671: {involving modulation of the quality factor of the RF coil (G01R33/3642 takes precedence)} - G01R: MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES (indicating correct tuning of resonant circuits H03J3/12) ## Abstract A circuit for determining a polarization of a gas. The circuit includes a polarimetry circuit having an NMR coil that is configured to excite a polarized gas and that is responsive to an electromagnetic signal generated by the excited, polarized gas. The polarimetry circuit has a reproducible polarization measurement variability of less than about 2% when the NMR coil is exposed to a temperature in a range of about 0° C. to about 200° C. ## Claims ### Claim 1 A circuit for determining a polarization of a gas, comprising: a polarimetry circuit having an NMR coil that is configured to excite a polarized gas and that is responsive to an electromagnetic signal generated by the excited, polarized gas, the polarimetry circuit having a reproducible polarization measurement variability of less than about 2% when the NMR coil is exposed to a temperature in a range of about 0° C. to about 200° C. ### Claim 2 (depends on 1) The circuit of claim 1, wherein the polarimetry circuit has a reproducible polarization measurement variability of less than about 1% when the NMR coil is exposed to a temperature in a range of about 0° C. to about 200° C. ### Claim 3 (depends on 1) The circuit of claim 1, wherein the circuit-to-circuit polarization measurement variability is less than about 3% when the NMR coil is exposed to a temperature in a range of about 0° C. to about 200° C. ### Claim 4 (depends on 1) The circuit of claim 1, wherein the polarimetry circuit comprises: an oscillator circuit comprising an NMR coil that is adjacent to an optical cell containing the polarized gas; a pulse generator circuit that is configured to generate an electrical pulse that is transmitted to the optical cell through the NMR coil to excite the polarized gas; a Q-reduction circuit that is independent of the pulse generator circuit and is configured to reduce oscillations in the oscillator circuit from the electrical pulse responsive to a control signal; and a receive circuit that is responsive to an electrical signal induced in the oscillator circuit due to the electromagnetic signal generated by the excited, polarized gas. ### Claim 5 (depends on 4) The circuit of claim 4, wherein the pulse generator circuit comprises: a pair of diodes connected in anti-parallel and are placed in parallel with the oscillator circuit upon conclusion of the electrical pulse to limit a voltage drop across the oscillator circuit to a conduction voltage of one of the pair of diodes. ### Claim 6 (depends on 5) The circuit of claim 5, wherein each of the pair of diodes has a leakage current associated therewith that is less than about 1 μA. ### Claim 7 (depends on 6) The circuit of claim 6, wherein each of the pair of diodes has a leakage current associated therewith that is approximately 200 nA. ### Claim 8 (depends on 4) The circuit of claim 4, wherein the Q-reduction circuit comprises a field effect transistor that is connected in parallel with the oscillator circuit. ### Claim 9 (depends on 8) The circuit of claim 8, wherein the Q-reduction circuit further comprises: a capacitor connected between a gate terminal of the field effect transistor and a reference potential; an amplifier circuit having an input terminal that is coupled to the control signal; a resistor connected between the gate terminal of the field effect transistor and an output terminal of an amplifier circuit; and a diode connected in parallel with the resistor. ### Claim 10 (depends on 4) The circuit of claim 4, wherein the oscillator circuit comprises: a tuning capacitor; and a resistor connected in series with the tuning capacitor, the resistor and the tuning capacitor connected in parallel with the NMR coil. ### Claim 11 (depends on 10) The circuit of claim 10, wherein the tuning capacitor has a Q-value about 25 times the Q-value of the NMR coil. ### Claim 12 (depends on 10) The circuit of claim 10, wherein the tuning capacitor has a Q-value greater than about 1000. ### Claim 13 (depends on 10) The circuit of claim 10, wherein the oscillator circuit has a Q-value in a range of about 10 to about 30. ### Claim 14 (depends on 4) The circuit of claim 4, wherein the receive circuit comprises: an amplifier circuit having a gain that is proportional to a ratio of resistance values associated with a first resistor and a second resistor. ### Claim 15 (depends on 14) The circuit of claim 14, wherein the first and the second resistors have about a 1% variability tolerance. ### Claim 16 (depends on 4) The circuit of claim 4, wherein the NMR coil is a precision layer wound NMR coil. ### Claim 17 (depends on 4) The circuit of claim 4, wherein a frequency of the electrical signal induced in the oscillator is associated with a frequency at which a Q-value of the NMR coil is substantially independent of temperature between about 30° C. and about 200° C. ### Claim 18 (depends on 4) The circuit of claim 4, wherein the frequency of the electrical signal induced in the oscillator is about 61 kHz. ### Claim 19 (depends on 1) The circuit of claim 1, wherein the gas comprises at least one of 129Xe, 3He, 13C compounds, and 15N compounds.