US4777956A — NMR angiography system and method with immunity t…

Claim 1

Independent Claim 109 words

In a method for imaging moving material in a volume using magnetic resonance the steps of: exciting the magnetic moments of static material in the volume so that static material whose magnetic resonant frequency is other than the excitation frequency due to magnetic field inhomogeneity will produce no net received static material signals following the excitation and whereby said magnetic moments of static material will be returned to their equilibrium position, exciting the magnetic moments of moving material whereby only moving material will produce a net received signal, and processing the net received signal to form a two-dimensional projection image of moving material in a single volumetric imaging sequence.

Claim 2

Dependent Claim 109 words

In a method for imaging moving material in a volume using magnetic resonance the steps of: exciting the magnetic moments of static material in the volume so that static material whose magnetic resonant frequency is other than the excitation frequency due to magnetic field inhomogeneity will produce no net received static material signals following the excitation and whereby said magnetic moments of static material will be returned to their equilibrium position, exciting the magnetic moments of moving material whereby only moving material will produce a net received signal, and processing the net received signal to form a two-dimensional projection image of moving material in a single volumetric imaging sequence.

Claim 3

Dependent Claim 68 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 an inversion excitation and then exciting with a third excitation which is the same as the first excitation causing the moments of static material to return to equilibrium.

Claim 4

Dependent Claim 32 words

The method as described in claim 1 including the step of applying a magnetic gradient waveform to the volume during the excitation interval which provides no net phase shift for static material.

Claim 5

Dependent Claim 105 words

Apparatus for imaging the moving material in a volume using magnetic resonance comprising: means for exciting the magnetic moments of static material in the volume such that static material whose magnetic resonant frequency is other than the excitation frequency will produce no net received static material signals following the excitation and whereby static material magnetic moments will be returned to their equilibrium position, means for exciting the magnetic moments of moving material whereby only moving material will produce a net received signal, and means for processing the net received signal to form a two-dimensional projection image of moving material in a single volumetric imaging sequence.

Claim 6

Dependent Claim 105 words

Apparatus for imaging the moving material in a volume using magnetic resonance comprising: means for exciting the magnetic moments of static material in the volume such that static material whose magnetic resonant frequency is other than the excitation frequency will produce no net received static material signals following the excitation and whereby static material magnetic moments will be returned to their equilibrium position, means for exciting the magnetic moments of moving material whereby only moving material will produce a net received signal, and means for processing the net received signal to form a two-dimensional projection image of moving material in a single volumetric imaging sequence.

Claim 7

Dependent Claim 68 words

Apparatus as described in claim 4 wherein said means for exciting magnetic moments of static material and said means for exciting magnetic moments of moving material comprises means for providing a first excitation and means for providing a second excitation, following the first excitation, which is an inversion excitation and means for providing a third excitation, following the second excitation, which is the same as the first excitation.

Claim 8

Dependent Claim 61 words

Apparatus as described in claim 5 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 an inversion burst providing a flip angle of substantially -180° with respect to the same reference phase, and the third excitation provides the same 90° flip angle as the first.

Claim 9

Dependent Claim 26 words

Apparatus as described in claim 5 including means for providing magnetic gradient waveforms during the excitation interval which provides no net phase shift for static material.

Claim 10

Dependent Claim 28 words

Apparatus as described in claim 7 where the magnetic gradient waveforms coincide with the first and last excitation bursts whereby a selective region of the volume is excited.

Claim 11

Dependent Claim 30 words

Apparatus as described in claim 8 where the first excitation burst provides a flip angle of substantially 90° and the last excitation burst provides a flip angle of substantially 90°.

Claim 12

Dependent Claim 87 words

Apparatus as described in claim 7 where the means for excitation includes means for providing a first excitation burst and means for providing a second excitation burst which provides a tip angle which is substantially minus twice that of the first excitation and a third excitation burst substantially indentical to the first and gradient waveforms inserted between the first and second excitation bursts and the second and third excitation burst with substantially no gradient signal during the excitation bursts whereby the entire volume of interest is excited.

Claim 13

Dependent Claim 32 words

Apparatus as described in claim 7 including means for providing a sequence of excitations with magnetic gradients in different directions whereby the magnitude and direction of the moving material can be calculated.

Claim 14

Dependent Claim 45 words

Apparatus as described in claim 4 including means for providing a sequence of excitations with a gradient used during each excitation time to selectively excite a sequence of planar sections and where the processing means includes means for measuring the projection of each planar section.

Claim 15

Dependent Claim 31 words

Apparatus as described in claim 12 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.

Claim 16

Dependent Claim 38 words

Apparatus as described in claim 12 where the means for measuring each projection includes means for applying a time-varying gradient normal to the projection direction and processing the received signal to form the projection of each planar section.

Claim 17

Dependent Claim 43 words

Apparatus as described in claim 4 wherein the means for exciting the magnetic moments of moving material includes means for exciting the entire volume of interest and where the processing means includes means for simultaneously measuring the two-dimensional projection of the excited volume.

Claim 18

Dependent Claim 34 words

Apparatus as described in claim 15 wherein said means for exciting the magnetic moments of moving material further includes means for applying different gradient waveforms to the two axes normal to the projection direction.

Claim 19

Dependent Claim 23 words

Apparatus as described in claim 16 where one of the gradient waveforms is a static pulse and the other is a time-varying waveform.

Claim 20

Dependent Claim 13 words

Apparatus as described in claim 16 where both waveforms are time varying .

Claim 21

Dependent Claim 43 words

Apparatus as described in claim 16 including means for applying a sequence of volumetric excitations where one gradient waveform is static and the other a pulse preceding the readout of the resultant received signal where the pulse amplitude is varied for each excitation.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	1991-10-18	1992-04-18	1992-10-18	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	1995-10-18	1996-04-18	1996-10-18	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	1999-10-18	2000-04-18	2000-10-18	$7700.00	Window Closed / Lapsed

NMR angiography system and method with immunity to inhomogeneity

Abstract

Inventors

Bibliographic Details

Claims Analysis

References Cited (Backward Citations)

USPTO Annuity & Maintenance Windows

Assigned Categories & Tags

Assign Category Tag