WO2004059336A1 - Calibration of a polarization measurement station - Google Patents
Calibration of a polarization measurement station Download PDFInfo
- Publication number
- WO2004059336A1 WO2004059336A1 PCT/US2003/040715 US0340715W WO2004059336A1 WO 2004059336 A1 WO2004059336 A1 WO 2004059336A1 US 0340715 W US0340715 W US 0340715W WO 2004059336 A1 WO2004059336 A1 WO 2004059336A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- polarization
- active circuit
- coil
- circuit
- nmr
- Prior art date
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Classifications
-
- 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
- G01R33/58—Calibration of imaging systems, e.g. using test probes, Phantoms; Calibration objects or fiducial markers such as active or passive RF coils surrounding an MR active material
-
- 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
- G01R33/58—Calibration of imaging systems, e.g. using test probes, Phantoms; Calibration objects or fiducial markers such as active or passive RF coils surrounding an MR active material
- G01R33/583—Calibration of signal excitation or detection systems, e.g. for optimal RF excitation power or frequency
-
- 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
- G01R33/28—Details of apparatus provided for in groups G01R33/44 - G01R33/64
- G01R33/281—Means for the use of in vitro contrast agents
Definitions
- the present invention relates to the fields of Magnetic Resonance Imaging (MRI) and NMR spectroscopy. More specifically, the present invention is directed to equipment and methods for calibrating equipment used to measure the polarization of a substance.
- MRI Magnetic Resonance Imaging
- NMR NMR spectroscopy
- Polarizers are used to produce and accumulate hyperpolarized noble gases. Polarizers artificially enhance the polarization of certain noble gas nuclei (such as 129 Xe or 3 He) over the natural or equilibrium levels, i.e., the Boltzmann polarization. Such an increase is desirable because it enhances and increases the MRI signal intensity, thereby providing better images or signals of the substance in the body. See U. S. Patent Nos. 5,545,396; 5,642,625; 5,809,801; 6,079,213, and 6,295,834; the disclosures of these patents are hereby incorporated by reference herein as if recited in full herein.
- the noble gas can be blended with optically pumped alkali metal vapors such as rubidium ("Rb"). These optically pumped metal atoms collide with the noble gas atoms and hyperpolarize the noble gas nuclei through a phenomenon known as "spin-exchange.”
- the "optical pumping" of the alkali metal vapor is produced by irradiating the alkali-metal vapor with circularly polarized light at the wavelength of the first principal resonance for the alkali metal (e.g., 795 nm for Rb). Generally stated, the ground state atoms become excited, then subsequently decay back to the ground state.
- the alkali metal is removed from the hyperpolarized gas prior to introduction into a patient to form a non-toxic and/or sterile composition.
- Other polarization techniques not employing alkali metal spin exchange can also be employed as is known to those of skill in the art.
- the hyperpolarized state of the gas can deteriorate or decay relatively quickly and therefore must be handled, collected, transported, and stored carefully.
- the "Ti" decay constant associated with the hyperpolarized gas' longitudinal relaxation time is often used to describe the length of time it takes a gas sample to depolarize in a given situation, generally by about 36.7%.
- the handling of the hyperpolarized gas is critical because of the sensitivity of the hyperpolarized state to environmental and handling factors and the potential for undesirable decay of the gas from its hyperpolarized state prior to the planned end use, i.e., delivery to a patient for imaging.
- Processing, transporting, and storing the hyperpolarized gases — as well as delivery of the gas to the patient or end user — can expose the hyperpolarized gases to various relaxation mechanisms such as magnetic gradients, contact-induced relaxation, paramagnetic impurities, and the like.
- Polarization measurement station 12 includes an NMR pickup coil 14 held by a planar substrate 16 horizontally spanning the axis of a first and second annular coil form 18 and 20. Pickup coil 14 is connected to an NMR pickup circuit 15. Coil forms 18 and 20 are about 30 inches in diameter while pickup coil 14 measures about one inch in diameter.
- the polarized gas sample 11 is positioned upon substrate 16 over pickup coil 14.
- Polarization measurement station 12 may be calibrated before leaving its manufacture facility through comparison with thermally polarized H 2 O in a high field NMR magnet.
- the present invention provides equipment and methods for calibrating a polarization measurement station.
- the present invention provides a transfer standard device having an active electronic circuit which simulates a sample of gas polarized to a specific level.
- the circuit may include a coil.
- the present invention will always read that specific level of polarization. For example, a transfer standard prototype having a circuit that always responds as a sample of 3 He polarized to 23.8% has been constructed.
- the present invention further provides a method for testing the calibration of an instrument for measuring the polarization of a sample, wherein the instrument includes an NMR pickup coil connected to NMR pickup circuitry.
- the method includes the step of placing an active circuit adjacent to the NMR pickup coil, wherein the active circuit is loosely coupled to the NMR pickup coil and responds as a hyperpolarized gas having a specific level of polarization when measured by the NMR pickup coil.
- the present invention still further provides a method for calibrating a polarization measurement station having an NMR pickup coil connected to NMR pickup circuitry.
- the method includes the step of placing an active circuit adjacent to the NMR pickup coil, wherein the active circuit responds as a hyperpolarized gas having a specific level of polarization when measured by the NMR pickup coil. Then the instrument for measuring the polarization of a sample is adjusted so as to be calibrated to read the specific level of polarization of the active circuit.
- the transfer standard's apparent "polarization" is first measured on a calibrated polarization measuring device. This is done by placing the transfer standard on the device in place of polarized gas and taking a measurement with the device just as though a polarized gas sample were present. The transfer standard is then assigned the apparent polarization measured by the device. The transfer standard can then be removed to the location of another such device and measured in the same way. The calibration of the second device can then be adjusted to match the first.
- Figure 1 depicts a polarization measurement station incorporating an NMR pickup coil.
- Figure 2 is an alternate depiction of a polarization measurement station incorporating an NMR pickup coil.
- Figure 3 depicts a transfer standard of the present invention positioned in the polarization measurement station of Figure 2.
- Figure 4 depicts a transfer standard coil located axially-aligned with an NMR pickup coil.
- Figure 5 depicts a transfer standard coil in coplanar alignment with an NMR pickup coil.
- Figure 6 depicts an LC Wien-bridge oscillator circuit.
- Figure 7 depicts the LC Wien-bridge oscillator circuit of Figure 6 redrawn as a parallel LRC circuit.
- Figure 8 depicts a tank circuit for coplanar alignment with a pickup coil having a discrete inductor in series with the transfer standard coil.
- Figure 9 depicts an example of a free induction decay (FID) of a sample of 17.2% polarized 3He.
- Figure 10 depicts the response signal from a transfer standard device exhibiting 23.8% apparent polarization
- Figure 11 depicts a concentric coplanar transfer standard demonstration device.
- Figure 12 shows the peak-to-peak values of the FIDs as reported by the calibration station (open circles) as well as selected peak-to-peak values obtained by extrapolating the exponential FID envelope function back to before the 3 ms postmute time.
- Figures 13 and 14 depict an alternate embodiment of a transfer standard of the present invention.
- Transfer standard 10 for use in a polarization measurement station 12.
- Transfer standard 10 includes a 9-inch by 9-inch by 1-inch container 22.
- Transfer standard 10 is shown in a partial cut-away view in Figure 3 to include an 8 inch transfer standard coil 24 having a 5- turn loop 26 connected to an active, e.g. battery powered, circuit 28 powered by a 9 volt battery power source.
- Container 22 desirably includes indicia for positioning transfer standard 10 on substrate 16 so that coil 24 is in axial-alignment with pickup coil 14.
- the apparent "polarization" must first be measured on a calibrated polarization measuring device. This is done simply by placing the transfer standard on the calibrated polarization measuring device in place of polarized gas and taking a measurement with the device just as though a polarized gas sample were present. The transfer standard is then assigned the apparent polarization measured by the device. The transfer standard can then be removed to the location of another such device and measured in the same way; the calibration of the second device can then be adjusted to match the first.
- Transfer coil 24 of transfer standard 10 desirably includes a geometry selected such that it is "loosely” coupled to pickup coil 14 in polarization measurement station 12.
- loosely is taken to mean that the resonant frequency and quality factor (0 of the NMR pickup circuit to which pickup coil 14 is connected are changed negligibly by the addition of transfer standard 10.
- Figures 4 and 5 illustrate 2 possibilities for this geometry.
- Figure 4 depicts a transfer standard coil which is coaxial with the NMR pickup coil while
- Figure 5 depicts a transfer standard coil which is coplanar with the NMR pickup coil.
- the transfer coil 24 will likely always be positioned in spaced overlying registry with pickup coil 14 rather than in pure coplanar alignment.
- the present invention thus employs the terms
- Transfer coil 24 is incorporated into the Wien-bridge oscillator circuit 30 of Figure 6, where the frequency selection is accomplished by means of the parallel EC tank circuit 32 (where E is transfer standard coil 24 itself).
- LC tank circuit 32 is desirably incorporated into container 22 so as to provide a single unit to for easier handling.
- coil 24 and circuit 30 may be provided in separate housings and electrically connected together.
- Oscillator circuit 30 makes use of negative feedback provided by the R1R2 network and positive feedback provided by the tank circuit combined with R3. fRl + R2 ⁇ ( Z
- the condition for stable oscillation is that the positive feedback be greater than or equal to the negative feedback. In terms of the individual components, this condition can be written as
- Z is the impedance of EC tank circuit 32, or:
- Z is maximal, purely resistive, and equal to E/RC.
- the equivalent resistance is negative, i.e., if a voltage is applied to the circuit, a current flows backward.
- the condition for oscillation is that the energy supplied by the negative resistance each cycle must be greater than or equal to the energy dissipated in the tank circuit.
- the energy dissipated in the tank is given by U _ 2 V _ ⁇ CV 2 ⁇
- the oscillation condition is then AU ⁇ AU', or
- the components of the transfer standard circuit are chosen such that oscillation condition is approached without actually being met.
- the circuit then behaves like a parallel ERC circuit with very high equivalent quality factor, Q eg (Q eq is selected, for 24 kHz operation, to be approximately 1500).
- Q eg Q eq is selected, for 24 kHz operation, to be approximately 1500.
- This is useful as a transfer standard because a sample of polarized gas behaves very much like a high- ⁇ ERC circuit loosely coupled to the NMR pickup coil used to detect the polarization.
- Transfer standard coil 24 itself should be chosen such that the polarimetry circuit's operation is not affected by the presence of the transfer standard (e.g. resonant frequency and Q changed by less than 1%).
- M In terms of the mutual inductance M of the two coils and the indutance L nmr of the NMR coil, it is desired that M «L nmr .
- M In terms of the mutual inductance M of the two coils and the indutance L nmr of the NMR coil, it is desired that M «L nmr .
- N nmr is the number of turns in the ⁇ MR pickup coil
- N ts is the number of turns in the transfer standard coil
- a nmr is the diameter of the nmr pickup coil
- a ts is the diameter of the transfer standard coil
- d is the distance between the loops. Also, d is much larger than the radius a of either loop.
- the solution of the mutual inductance of two identical coaxial loops is given in Jackson, J.D., Classical Electrodynamics. 2 ed. 1975, New York: John Wiley & Sons, pg. 848, problem 6.7, which is hereby incorporated by reference herein.
- the disadvantage of such geometry is that the coupling between the two coils is a very sensitive function of the separation distance (M ⁇ d ⁇ 3 ).
- the advantage of such geometry is that the coupling can be easily adjusted by varying this distance.
- transfer standard 10 is relatively insensitive to the placement of transfer standard coil 24.
- calculations show that the apparent polarization of an 8" transfer standard coil should drop by approximately 1% for a 1/8" lateral displacement (from concentric) and approximately 1% for a 3/4" vertical displacement (from coplanar).
- Such low variance is a significant finding as transfer standard 10, being typically positioned on top of plate 16, will not be precisely coplanar with pickup coil 14 but will have a small vertical displacement.
- transfer standard coil 24 "rings up". Voltage is added to the coil at a rate
- I p is the current in the nmr coil and V p cos ⁇ t is the pulse voltage applied to the nmr coil.
- V p cos ⁇ t is the pulse voltage applied to the nmr coil.
- E 2 denotes the relaxation time of the coil oscillations (analogous to the transverse relaxation time of a polarized sample).
- a bag of 3 He in the fairly homogeneous holding field of the polarimetry station looks to the polarimetry circuit similar to be a loosely coupled coil with large but finite Q.
- Figure 9 shows the signal obtained on a polarization measurement device using the prototype transfer standard (also shown is an FID from actual He for compa ⁇ son, though this FID was acquired on a different device of the same design).
- the transfer standard signal was measured as a function of both pulse duration and voltage. The results of these measurements are displayed in Figure 10.
- the nonzero ⁇ -intercept in signal vs. pulse duration is entirely due to the pulse ringdown (no ⁇ -switch was employed).
- the behavior of signal vs. pulse voltage at low voltage is due to the diode gate in the polarimetry transmit circuit; its effect may be approximated by subtracting a voltage equal to two diode drops from the pulse voltage applied. The remaining nonzero .y-intercept is again due to pulse ringdown.
- Example 2 With reference to Figure 11, a concentric coplanar transfer standard 110 was constructed using an 8" diameter V" thick PNC pipe as a coil form 102. 100 turns of wire 104 were wound in a channel 106 machined on form 102. The coil was tuned to roughly match the polarimetry circuit and the effect of the transfer standard on the polarimetry circuit's parameters (by looking for a change in the "coil test" response) was determined. This procedure was repeated, removing a few turns at a time, until no change in the response was visible. It was determined that only 5 turns were required for the transfer standard.
- the Wien oscillator circuit was then constructed around the 5-turn coil and the apparent polarization was measured. It was decided to cut the apparent polarization by a factor of approximately 15 by adding an additional 220 ⁇ H inductor (Coilcraft
- Transfer standard 210 includes mating housing components 212 and 214 which define therebetween a coil cavity 216 and a circuit compartment 218 (shown by phantom lines in Figure 13).
- Coil cavity 216 receives a coil form 220 about which a transfer standard coil 222 having a 5 -turn loop 224 and a comiected active circuit 226 powered by a battery 228.
- Housing components 212 and 214 are desirably formed from a non-ferrous material, such as a suitable plastic.
- a number of screws 230 hold coil form 220 in place with respect to housing components 212 and 214 while screws 232 hold components 212 and 214 together.
- Other fastening devices as well as adhesives are contemplated for performing the function of screws 230 and 232.
- Tranfer standard 210 further includes cylindrical pins 234 depending from second housing component 214. Pins 234 are spaced to matingly engage tap apertures 236 defined by the upward-facing major surface of planar substrate 216 so as to ensure the proper alignment of transfer standard 210 with respect to the NMR coil 14 of calibration station 10. Proper alignment of transfer standard 210 and NMR coil 14 will minimize errors in measuring the apparent polarization of transfer standard 210.
Abstract
Description
Claims
Priority Applications (5)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
EP03814245A EP1573349A1 (en) | 2002-12-20 | 2003-12-19 | Calibration of a polarization measurement station |
AU2003301172A AU2003301172B2 (en) | 2002-12-20 | 2003-12-19 | Calibration of a polarization measurement station |
NZ540078A NZ540078A (en) | 2002-12-20 | 2003-12-19 | Calibration of a polarization measurement station |
JP2004563858A JP4570034B2 (en) | 2002-12-20 | 2003-12-19 | Calibration of polarization measuring station |
CA002506433A CA2506433A1 (en) | 2002-12-20 | 2003-12-19 | Calibration of a polarization measurement station |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US43510102P | 2002-12-20 | 2002-12-20 | |
US60/435,101 | 2002-12-20 |
Publications (1)
Publication Number | Publication Date |
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WO2004059336A1 true WO2004059336A1 (en) | 2004-07-15 |
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ID=32682156
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
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PCT/US2003/040715 WO2004059336A1 (en) | 2002-12-20 | 2003-12-19 | Calibration of a polarization measurement station |
Country Status (10)
Country | Link |
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US (1) | US6867591B2 (en) |
EP (1) | EP1573349A1 (en) |
JP (1) | JP4570034B2 (en) |
KR (1) | KR20050084371A (en) |
CN (1) | CN100516925C (en) |
AU (1) | AU2003301172B2 (en) |
CA (1) | CA2506433A1 (en) |
NZ (1) | NZ540078A (en) |
WO (1) | WO2004059336A1 (en) |
ZA (1) | ZA200505402B (en) |
Families Citing this family (3)
Publication number | Priority date | Publication date | Assignee | Title |
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CN100516925C (en) * | 2002-12-20 | 2009-07-22 | 医疗物理有限公司 | Calibration of a polarization measurement station |
US7218111B2 (en) * | 2004-12-07 | 2007-05-15 | James Maurice Daniels | Instrument to measure the polarization of a hyperpolarized substance |
WO2009153705A1 (en) * | 2008-06-20 | 2009-12-23 | Koninklijke Philips Electronics N.V. | Electronic load simulator device for testing rf coils |
Citations (3)
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US4452250A (en) * | 1982-04-29 | 1984-06-05 | Britton Chance | NMR System for the non-invasive study of phosphorus metabilism |
JPS6050441A (en) * | 1983-08-30 | 1985-03-20 | Yokogawa Medical Syst Ltd | Magnetic-field calibrating device in nuclear-magnetic- resonance imaging apparatus |
US20010029739A1 (en) * | 1998-09-30 | 2001-10-18 | Zollinger David L. | Hyperpolarized noble gas extraction methods, masking methods, and associated transport containers |
Family Cites Families (11)
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JPH0194258A (en) * | 1987-10-06 | 1989-04-12 | Koyo Seiko Co Ltd | Diagnostic apparatus |
JPH06281625A (en) * | 1993-03-26 | 1994-10-07 | Nippon Steel Corp | Device for calibrating sensitivity of leakage magnetic flaw detection device |
US5545396A (en) * | 1994-04-08 | 1996-08-13 | The Research Foundation Of State University Of New York | Magnetic resonance imaging using hyperpolarized noble gases |
US5642625A (en) * | 1996-03-29 | 1997-07-01 | The Trustees Of Princeton University | High volume hyperpolarizer for spin-polarized noble gas |
US5809801A (en) * | 1996-03-29 | 1998-09-22 | The Trustees Of Princeton University | Cryogenic accumulator for spin-polarized xenon-129 |
DE19742543C2 (en) * | 1997-09-26 | 1999-09-23 | Otten Ernst Wilhelm | Method and device for determining the degree of polarization of nuclear spin polarized gases, in particular the helium isotope · 3 · He and · 1 ·· 2 ·· 9 · Xe |
US6079213A (en) * | 1997-12-12 | 2000-06-27 | Magnetic Imaging Technologies Incorporated | Methods of collecting, thawing, and extending the useful life of polarized gases and associated accumulators and heating jackets |
EP1155339A1 (en) * | 1999-02-23 | 2001-11-21 | Medi-Physics, Inc. | Portable system for monitoring the polarization level of a hyperpolarized gas during transport |
US6295834B1 (en) * | 1999-06-30 | 2001-10-02 | Medi-Physics, Inc. | NMR polarization monitoring coils, hyperpolarizers with same, and methods for determining the polarization level of accumulated hyperpolarized noble gases during production |
US6356080B1 (en) * | 1999-09-28 | 2002-03-12 | James Maurice Daniels | Device to measure the polarization of a hyperpolarized resonant substance |
CN100516925C (en) * | 2002-12-20 | 2009-07-22 | 医疗物理有限公司 | Calibration of a polarization measurement station |
-
2003
- 2003-12-19 CN CNB2003801065658A patent/CN100516925C/en not_active Expired - Fee Related
- 2003-12-19 JP JP2004563858A patent/JP4570034B2/en not_active Expired - Lifetime
- 2003-12-19 WO PCT/US2003/040715 patent/WO2004059336A1/en active Application Filing
- 2003-12-19 CA CA002506433A patent/CA2506433A1/en not_active Abandoned
- 2003-12-19 EP EP03814245A patent/EP1573349A1/en not_active Withdrawn
- 2003-12-19 NZ NZ540078A patent/NZ540078A/en not_active IP Right Cessation
- 2003-12-19 AU AU2003301172A patent/AU2003301172B2/en not_active Ceased
- 2003-12-19 US US10/741,610 patent/US6867591B2/en active Active
- 2003-12-19 KR KR1020057011175A patent/KR20050084371A/en not_active Application Discontinuation
-
2006
- 2006-01-25 ZA ZA200505402A patent/ZA200505402B/en unknown
Patent Citations (3)
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US4452250A (en) * | 1982-04-29 | 1984-06-05 | Britton Chance | NMR System for the non-invasive study of phosphorus metabilism |
JPS6050441A (en) * | 1983-08-30 | 1985-03-20 | Yokogawa Medical Syst Ltd | Magnetic-field calibrating device in nuclear-magnetic- resonance imaging apparatus |
US20010029739A1 (en) * | 1998-09-30 | 2001-10-18 | Zollinger David L. | Hyperpolarized noble gas extraction methods, masking methods, and associated transport containers |
Non-Patent Citations (2)
Title |
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MUGLER J P ET AL: "MR IMAGING AND SPECTROSCOPY USING HYPERPOLARIZED 129XE GAS: PRELIMINARY HUMAN RESULTS", MAGNETIC RESONANCE IN MEDICINE, ACADEMIC PRESS, DULUTH, MN, US, vol. 37, no. 6, 1 June 1997 (1997-06-01), pages 809 - 815, XP000655650, ISSN: 0740-3194 * |
PATENT ABSTRACTS OF JAPAN vol. 0091, no. 74 (P - 374) 19 July 1985 (1985-07-19) * |
Also Published As
Publication number | Publication date |
---|---|
JP4570034B2 (en) | 2010-10-27 |
KR20050084371A (en) | 2005-08-26 |
NZ540078A (en) | 2007-05-31 |
CN100516925C (en) | 2009-07-22 |
AU2003301172B2 (en) | 2010-02-18 |
CN1726402A (en) | 2006-01-25 |
US20040145368A1 (en) | 2004-07-29 |
AU2003301172A1 (en) | 2004-07-22 |
CA2506433A1 (en) | 2004-07-15 |
US6867591B2 (en) | 2005-03-15 |
JP2006511802A (en) | 2006-04-06 |
ZA200505402B (en) | 2006-03-29 |
EP1573349A1 (en) | 2005-09-14 |
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