Patent US5023555A successfully refreshed from Google Patents.
US5023555A
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US
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Magnetic resonance imaging
Assignee: Instrumentarium Oyj
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Filing: 1990-01-02
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Granted: 1991-06-11
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Expires: 2010-01-02
Abstract
Abstract The invention provides a magnetic resonance imaging apparatus having a primary field generating means for generating a substantially uniform magnetic field, wherein that said primary field generating means is arranged in use to generate a magnetic field the field direction of which varies with time, e.g. a rotating field. The varying field operates to average out from the magnetic field experienced by the sample being imaged at least some of the external perturbing magnetic fields so reducing the sensitivity of the apparatus to such external fields.
Inventors
- 👤 Gosta J. Ehnholm
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-08 12:35
CPC Classifications
G; G01; G01R; G01R33/00; G01R33/20; G01R33/44; G01R33/445
Claims Analysis
Total Claims: 18
Claim 1
Independent Claim
41 words
A magnetic resonance imaging apparatus having a primary field generating means for generating a substantially uniform magnetic field, wherein said primary field generating means is arranged in use to generate a magnetic field the field direction of which varies with time.
Claim 2
Dependent Claim
41 words
A magnetic resonance imaging apparatus having a primary field generating means for generating a substantially uniform magnetic field, wherein said primary field generating means is arranged in use to generate a magnetic field the field direction of which varies with time.
Claim 3
Dependent Claim
30 words
Apparatus as claimed in claim 1 wherein said primary field generating means is arranged in use to generate a magnetic field the field direction of which varies cyclically with time.
Claim 4
Dependent Claim
31 words
Apparatus as claimed in claim 2 wherein said primary field generating means is arranged in use to generate a magnetic field the field direction of which rotates about a fixed axis.
Claim 5
Dependent Claim
35 words
Apparatus as claimed in claim 3 wherein said primary field generating means is arranged in use to generate a magnetic field the field direction of which rotates at a frequency of 25 to 1000 Hz.
Claim 6
Dependent Claim
35 words
Apparatus as claimed in claim 3 wherein said primary field generating means is arranged in use to generate a magnetic field the field direction of which rotates at a frequency of 100 to 500 Hz.
Claim 7
Dependent Claim
52 words
Apparatus as claimed in claim 3 arranged to receive power from an AC power supply and wherein said primary field generating means is arranged in use to generate a magnetic field the field direction of which rotates at a frequency which is an even harmonic of the frequency of said AC supply.
Claim 8
Dependent Claim
52 words
Apparatus as claimed in claim 5 arranged to receive power from an AC power supply and wherein said primary field generating means is arranged in use to generate a magnetic field the field direction of which rotates at a frequency which is an even harmonic of the frequency of said AC supply
Claim 9
Dependent Claim
86 words
In a method of magnetic resonance imaging of a sample which method comprises placing a sample within a substantially uniform primary magnetic field, exposing said sample to radiation of a frequency selected to excite nuclear spin transitions in selected non-zero spin nuclei therein, imposing a magnetic field gradient on said primary field, detecting magnetic resonance signals from said selected nuclei, and generating an image of said sample from said detected signals, the improvement comprising causing the field direction of said primary field to vary with time.
Claim 10
Dependent Claim
86 words
In a method of magnetic resonance imaging of a sample which method comprises placing a sample within a substantially uniform primary magnetic field, exposing said sample to radiation of a frequency selected to excite nuclear spin transitions in selected non-zero spin nuclei therein, imposing a magnetic field gradient on said primary field, detecting magnetic resonance signals from said selected nuclei, and generating an image of said sample from said detected signals, the improvement comprising causing the field direction of said primary field to vary with time.
Claim 11
Dependent Claim
22 words
A method as claimed in claim 8 wherein the field direction of said primary field is caused to vary cyclically with time.
Claim 12
Dependent Claim
23 words
A method as claimed in claim 9 wherein the field direction of said primary field is caused to rotate about a fixed axis.
Claim 13
Dependent Claim
27 words
A method as claimed in claim 10 wherein the field direction of said primary field is caused to rotate at a frequency of 25 to 1000 Hz.
Claim 14
Dependent Claim
27 words
A method as claimed in claim 11 wherein the field direction of said primary field is caused to rotate at a frequency of 100 to 500 Hz.
Claim 15
Dependent Claim
41 words
A method as claimed in claim 10 wherein said field direction is caused to rotate at a frequency which is an even harmonic of the frequency of an AC power supply powering the apparatus by which said imaging method is performed.
Claim 16
Dependent Claim
41 words
A method as claimed in claim 12 wherein said field direction is caused to rotate at a frequency which is an even harmonic of the frequency of an AC power supply powering the apparatus by which said imaging method is performed.
Claim 17
Dependent Claim
18 words
A method as claimed in claim 8 being a method of electron spin resonance enhanced magnetic resonance imaging.
Claim 18
Dependent Claim
20 words
A method as claimed in claim 8 wherein said sample is exposed to nuclear spin system pre-polarizing magnetic field pulses.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1994-06-10 | 1994-12-10 | 1995-06-11 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1998-06-10 | 1998-12-10 | 1999-06-11 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2002-06-10 | 2002-12-10 | 2003-06-11 | $7700.00 | Window Closed / Lapsed |