Patent US4993414A successfully refreshed from Google Patents.
US4993414A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Moving material projection imaging system using nuclear magnetic resonance
Assignee: Leland Stanford Junior University
•
Filing: 1989-08-28
•
Granted: 1991-02-19
•
Expires: 2009-08-28
Abstract
Abstract A two-dimensional projection image of the NMR activity within a volume is obtained. The signals due to static material are not excited and do not appear in the projection image. The signals due to moving blood in vessels produce an isolated image of the vessels with the superimposed structure removed. Excitation systems are used which excite only moving material and return static material to equilibrium.
Inventors
- 👤 Albert Macovski
- 👤 Dwight G. Nishimura
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 06:53
CPC Classifications
G; G01; G01R; G01R33/00; G01R33/20; G01R33/44; G01R33/48; G01R33/54; G01R33/56; G01R33/563
Claims Analysis
Total Claims: 13
Claim 1
Independent Claim
97 words
A method of imaging moving material in a volume using magnetic resonance comprising the steps of: substantially spatially uniformly exciting the magnetic moments in the volume during an excitation period so that static material will produce no net received signals following the excitation and static material magnetic moments will be returned to their equilibrium position whereby only moving material in said volume will produce net received signals, applying a static magnetic gradient waveform to said volume in said excitation period, and processing received signals to form a two-dimensional projection image of the moving material in the volume.
Claim 2
Independent Claim
97 words
A method of imaging moving material in a volume using magnetic resonance comprising the steps of: substantially spatially uniformly exciting the magnetic moments in the volume during an excitation period so that static material will produce no net received signals following the excitation and static material magnetic moments will be returned to their equilibrium position whereby only moving material in said volume will produce net received signals, applying a static magnetic gradient waveform to said volume in said excitation period, and processing received signals to form a two-dimensional projection image of the moving material in the volume.
Claim 3
Dependent Claim
56 words
The method as described in claim 1 wherein the step of exciting the magnetic moments in the volume includes the step of exciting the moments with a first excitation and then exciting the moments with a second excitation which is the inverse of the first excitation causing the moments of static material to return to equilibrium.
Claim 4
Dependent Claim
98 words
Apparatus for use in imaging moving material in a volume using magnetic resonance comprising: means for substantially spatially uniformly exciting magnetic moments in a volume during an excitation period such that static material will produce no net received signals following the excitation and static material magnetic moments will be returned to their equilibrium position whereby only moving material will produce net received signals, means for applying a static magnetic gradient waveform to said volume in said excitation period, and means for processing the received signals to form a two-dimensional projection image of the moving material in the volume.
Claim 5
Dependent Claim
98 words
Apparatus for use in imaging moving material in a volume using magnetic resonance comprising: means for substantially spatially uniformly exciting magnetic moments in a volume during an excitation period such that static material will produce no net received signals following the excitation and static material magnetic moments will be returned to their equilibrium position whereby only moving material will produce net received signals, means for applying a static magnetic gradient waveform to said volume in said excitation period, and means for processing the received signals to form a two-dimensional projection image of the moving material in the volume.
Claim 6
Dependent Claim
39 words
Apparatus as described in claim 3 where the means for exciting the volume includes means for providing a first excitation and means for providing a second excitation, following the first excitation, which is the inverse of the first excitation.
Claim 7
Dependent Claim
71 words
Apparatus as described in claim 4 where said means for providing a first excitation comprises means for providing a first excitation which provides a burst producing a flip angle of substantially 90° with respect to a reference phase and said means for providing a second excitation comprises means for providing a second excitation which provides a burst producing a flip angle of substantially -90° with respect to the same reference phase.
Claim 8
Dependent Claim
30 words
Apparatus as described in claim 3 where the means for applying a magnetic gradient waveform comprises means for providing a magnetic gradient waveform having a positive and a negative portion.
Claim 9
Dependent Claim
61 words
Apparatus as described in claim 6 where said means for providing a magnetic gradient waveform comprises means for providing a magnetic gradient waveform, where one polarity of the magnetic gradient waveform coincides with a first excitation burst and the other polarity of the magnetic gradient waveform corresponds to a second excitation burst whereby a selective region of the volume is excited.
Claim 10
Dependent Claim
47 words
Apparatus as described in claim 7 where said means for substantially spatially uniformly exciting magnetic moments includes means for providing a first excitation with a flip angle of substantially 90° and for providing a second excitation following the first excitation with a flip angle of substantially -90°.
Claim 11
Dependent Claim
28 words
Apparatus as described in claim 3 where the means for applying a magnetic gradient waveform comprises means for providing a magnetic gradient waveform having a zero average value.
Claim 12
Dependent Claim
44 words
Apparatus as described in claim 3 including means for providing a sequence of excitations with a gradient used during each excitation to selectively excite a sequence of planar sections and where the processing means includes means for measuring the projection of each planar section.
Claim 13
Dependent Claim
31 words
Apparatus as described in claim 10 where the means for measuring each projection includes means for applying a static gradient normal to the projection direction and Fourier transforming the received signal.
References Cited (Backward Citations)
US4254778A
Cited
US4553096A
Cited
US4564813A
Cited
US4516075A
Cited
US4516582A
Cited
US4532473A
Cited
US4574239A
Cited
US4602641A
Cited
US4654591A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1994-02-18 | 1994-08-20 | 1995-02-19 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1998-02-18 | 1998-08-20 | 1999-02-19 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2002-02-18 | 2002-08-20 | 2003-02-19 | $7700.00 | Window Closed / Lapsed |