US4665366A
Expired / Lapsed
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NMR imaging system using phase-shifted signals
Assignee: Individual
•
Filing: 1985-03-11
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Granted: 1987-05-12
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Expires: 2005-03-11
Abstract
Abstract The nuclei in a volume are imaged using a sequence of excitations in the presence of one or more time-varying gradient fields. The resultant phase variations are cancelled to isolate a region of the volume. Various phase-modulation functions are used to provide a desired localization function. The excitation variations can be combined with time-varying gradients during the reception interval.
Inventors
- 👤 Albert Macovski
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-24 23:52
CPC Classifications
G; G01; G01R; G01R33/00; G01R33/20; G01R33/44; G01R33/446
Claims Analysis
Total Claims: 27
Claim 1
Independent Claim
107 words
In a method for imaging the magnetic resonance activity of an object the steps of: exciting the object with a sequence of rf magnetic excitations in the present of a time-varying magnetic gradient field, each excitation having a gradient field that is different from the gradient fields for other excitations; receiving a sequence of signals resulting from said excitations; and processing the received signals to map the magnetic resonance activity at a plurality of regions of the object defined by the interaction of rf excitations and the gradient field including cancelling the phase variation caused by the time-varying gradient field corresponding to a region of the object.
Claim 2
Dependent Claim
107 words
In a method for imaging the magnetic resonance activity of an object the steps of: exciting the object with a sequence of rf magnetic excitations in the present of a time-varying magnetic gradient field, each excitation having a gradient field that is different from the gradient fields for other excitations; receiving a sequence of signals resulting from said excitations; and processing the received signals to map the magnetic resonance activity at a plurality of regions of the object defined by the interaction of rf excitations and the gradient field including cancelling the phase variation caused by the time-varying gradient field corresponding to a region of the object.
Claim 3
Dependent Claim
36 words
The method as in claim 1 where the step of cancelling the phase variation includes the step of phase-shifting the received signals following each excitation an amount dependent on the region of the object being imaged.
Claim 4
Dependent Claim
42 words
The method as in claim 1 where the step of cancelling the phase variations includes the step of demodulating the received signals and phase shifting the demodulating signals following each excitation an amount dependent on the region of the object being imaged.
Claim 5
Dependent Claim
46 words
The method as in claim 1 where the step of cancelling the phase variations includes the step of demodulating the received signal using sine and cosine demodulators and amplitude modulating the output of each demodulator by factors dependent on the region of the object being imaged.
Claim 6
Dependent Claim
52 words
The method as in claim 1 where the step of processing the received signal includes the step of Fourier transforming the received signal and convolving the resultant spectrum with the transform of a sequence of phase shifted signals where the phase shift is dependent on the region of the object being imaged.
Claim 7
Dependent Claim
50 words
The method as in claim 1 where the step of processing the received signal includes the steps of Fourier transforming the received signal into components of a spectrum, weighting the components of the spectrum with weights dependent on the region of the object being imaged and summing the weighted components.
Claim 8
Dependent Claim
45 words
The method as in claim 1 including the step of multiplying the received signal by a sequence of phase shifts corresponding to a harmonic of the time-varying signal to obtain a resultant signal and using the resultant signal to provide a better defined localization function.
Claim 9
Dependent Claim
66 words
In a method for processing a received magnetic resonance signal resulting from repeated radio frequency excitations of an object in the presence of a magnetic field to produce an image of the object the steps of: compensating for the initial phase variations of the received magnetic resonance signal following each radio frequency excitation for each region of the object being imaged; and summing the compensated signals.
Claim 10
Dependent Claim
66 words
In a method for processing a received magnetic resonance signal resulting from repeated radio frequency excitations of an object in the presence of a magnetic field to produce an image of the object the steps of: compensating for the initial phase variations of the received magnetic resonance signal following each radio frequency excitation for each region of the object being imaged; and summing the compensated signals.
Claim 11
Dependent Claim
74 words
In a method for imaging the magnetic resonance activity of an object the steps of: applying time-varying gradient magnetic fields to said object; exciting the object with a sequence of rf magnetic excitations; receiving the resultant signals from the sequence of excitations; cancelling the initial phase shift following each excitation corresponding to a region of the object; multiplying the received signal by a waveform corresponding to the gradient signal; and filtering the resultant signal.
Claim 12
Dependent Claim
74 words
In a method for imaging the magnetic resonance activity of an object the steps of: applying time-varying gradient magnetic fields to said object; exciting the object with a sequence of rf magnetic excitations; receiving the resultant signals from the sequence of excitations; cancelling the initial phase shift following each excitation corresponding to a region of the object; multiplying the received signal by a waveform corresponding to the gradient signal; and filtering the resultant signal.
Claim 13
Dependent Claim
97 words
Apparatus for imaging the magnetic resonance activity of an object comprising: means for exciting the object with a sequence of rf magnetic excitations in the present of a time-varying magnetic gradient field, each excitation having a gradient field that is different from the gradient fields for other excitations; means for receiving a sequence of signals following the excitations; and means for processing the received signals to map the magnetic resonance activity at a plurality of regions of the object including cancelling the phase shift caused by the time-varying gradient field corresponding to a region of the object.
Claim 14
Dependent Claim
97 words
Apparatus for imaging the magnetic resonance activity of an object comprising: means for exciting the object with a sequence of rf magnetic excitations in the present of a time-varying magnetic gradient field, each excitation having a gradient field that is different from the gradient fields for other excitations; means for receiving a sequence of signals following the excitations; and means for processing the received signals to map the magnetic resonance activity at a plurality of regions of the object including cancelling the phase shift caused by the time-varying gradient field corresponding to a region of the object.
Claim 15
Dependent Claim
35 words
Apparatus as described in claim 10 where the means for cancelling the phase variation includes means for phase-shifting the received signals following each excitation an amount dependent on the region of the object being imaged.
Claim 16
Dependent Claim
43 words
Apparatus as described in claim 10 where the means for cancelling the phase variations includes means for demodulating the received signals and means for phase shifting the demodulation signals following each excitation an amount dependent on the region of the object being imaged.
Claim 17
Dependent Claim
47 words
Apparatus as described in claim 10 where the means for cancelling the phase variations includes means for demodulating the received signal using sine and cosine demodulators and means for amplitude modulating the output of each demodulator by factors dependent on the region of the object being imaged.
Claim 18
Dependent Claim
53 words
Apparatus as described in claim 10 where the means for processing the received signal includes means for Fourier transforming the received signal and means for convolving the resultant spectrum with the transform of a sequence of phase shifted signals where the phase shift is dependent on the region of the object being imaged.
Claim 19
Dependent Claim
48 words
Apparatus as described in claim 10 where the means for processing the received signal includes: means for Fourier transforming the received signal; means for weighting the components of the spectrum with weights dependent on the region of the object being imaged; and means for summing the weighted components.
Claim 20
Dependent Claim
41 words
Apparatus as described in claim 10 including means for multiplying the received signal by a sequence of phase shifts corresponding to a harmonic of the time-varying signal and means for processing the resultant signal to provide a better defined localization function.
Claim 21
Dependent Claim
21 words
Apparatus as described in claim 10 including means for applying a time-varying gradient signal during the time that signals are received.
Claim 22
Dependent Claim
25 words
Apparatus as described in claim 17 where the time-varying gradient is a continuous sinusoidal signal providing a time-varying gradient during the excitation and reception times.
Claim 23
Dependent Claim
17 words
Apparatus as described in claim 18 using a gradient circuit which is resonant at the sinusoidal frequency.
Claim 24
Dependent Claim
16 words
Apparatus as described in claim 10 including means for applying different gradient signals to each coordinate.
Claim 25
Dependent Claim
20 words
Apparatus as described in claim 20 where the different signals are sinusoids of different frequencies which are not harmonically related.
Claim 26
Dependent Claim
24 words
Apparatus as described in claim 20 where two of the coordinates have sinusoidal gradient signals of the same frequency which are of different phases.
Claim 27
Dependent Claim
45 words
Apparatus as described in claim 10 where the object includes blood vessels and including means for exciting the object at times corresponding to different blood velocities and means for subtracting the resultant images corresponding to different velocities whereby images are formed of blood vessels only.
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) | 1990-05-11 | 1990-11-10 | 1991-05-12 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1994-05-11 | 1994-11-10 | 1995-05-12 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1998-05-11 | 1998-11-10 | 1999-05-12 | $7700.00 | Window Closed / Lapsed |