EP0216490A2
Expired / Lapsed
EP
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Moving material projection imaging system using nuclear magnetic resonance
Assignee: Leland Stanford Junior University
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Filing: 1986-08-14
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Granted: —
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Expires: 2006-08-14
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 state material to equilibrium.
Inventors
- 👤 Albert Macovski
- 👤 Dwight George Nishimura
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-26 21:00
CPC Classifications
G; G01; G01R; G01R33/00; G01R33/20; G01R33/44; G01R33/48; G01R33/54; G01R33/56; G01R33/563
Claims Analysis
Total Claims: 16
Claim 1
Independent Claim
76 words
In a method for imaging moving material in a volume using magnetic resonance the steps of: exciting the magnetic moments in the volume so that static material will produce no net received signals following the excitation and their magnetic moments will be returned to their equilibrium position whereby only moving material will produce a net received signal, and processing the resultant received signals to form a two-dimensional projection image of the moving material in the volume.
Claim 2
Dependent Claim
76 words
In a method for imaging moving material in a volume using magnetic resonance the steps of: exciting the magnetic moments in the volume so that static material will produce no net received signals following the excitation and their magnetic moments will be returned to their equilibrium position whereby only moving material will produce a net received signal, and processing the resultant 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 excitaton causing the moments of static material to return to equilibrium.
Claim 4
Dependent Claim
34 words
The method as described in Claim 1 wherein the step of exciting the magnetic moments includes the step of exciting the moments with a 2π radian flip angle excitation returning static material to equilibrium.
Claim 5
Dependent Claim
24 words
The method as described in Claim 1 including the step of applying a zero-average magnetic gradient waveform to the volume during the excitation interval.
Claim 6
Dependent Claim
77 words
Apparatus for imaging the moving material in a volume using magnetic resonance comprising: means for exciting the magnetic moments in the volume such that static material will produce no net received signals following the excitation and their magnetic moment will be returned to the equilibrium position whereby only moving material will produce a net received signal, and means for processing the resultant received signal to form a two-dimensional projection image of the moving material in the volume.
Claim 7
Dependent Claim
77 words
Apparatus for imaging the moving material in a volume using magnetic resonance comprising: means for exciting the magnetic moments in the volume such that static material will produce no net received signals following the excitation and their magnetic moment will be returned to the equilibrium position whereby only moving material will produce a net received signal, and means for processing the resultant received signal to form a two-dimensional projection image of the moving material in the volume.
Claim 8
Dependent Claim
39 words
Apparatus as described in Claim 5 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 9
Dependent Claim
47 words
Apparatus as described in Claim 6 where the first excitation is a burst providing a flip angle of substantially 90° with respect to a reference phase and the second excitation is a burst providing a flip angle of substantially -90° with respect to the same reference phase.
Claim 10
Dependent Claim
26 words
Apparatus as described in Claim 5 where the means for excitation includes means for providing a burst which provides a flip angle of substantially 2π radians.
Claim 11
Dependent Claim
17 words
Apparatus as described in Claim 8 where the envelope of the burst is substantially a hyperbolic secant.
Claim 12
Dependent Claim
18 words
Apparatus as described in Claim 5 including means for providing a magnetic gradient waveform during the excitation interval.
Claim 13
Dependent Claim
18 words
Apparatus as described in Claim 10 where the magnetic gradient waveform has a positive and a negative portion.
Claim 14
Dependent Claim
53 words
Apparatus as described in Claim 11 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 which is the inverse of the first excitation burst whereby a selective region of the volume is excited.
Claim 15
Dependent Claim
30 words
Apparatus as described in Claim 12 where the first excitation burst provides a flip angle of substantially 90° and the second excitation burst provides a flip angle of substantially -90°.
Claim 16
Dependent Claim
68 words
Apparatus as described in Claim 10 where the means for excitation includes means for providing a first excitation burst and means for providing a second excitation burst which is the inverse of the first excitation burst where a zero average gradient waveform is inserted between the first and second excitation bursts with substantially no gradient signal during the excitation bursts whereby the entire volume of interest is excited.
References Cited (Backward Citations)
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