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US5757187A
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Apparatus and method for image formation in magnetic resonance utilizing weak time-varying gradient fields
Assignee: Wollin Ventures Inc
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Filing: 1997-08-22
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Granted: 1998-05-26
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Expires: 2017-08-22
Abstract
Abstract Weak oscillating gradients are used to modulate the angular momentum of the spins in a magnetic resonance imaging apparatus producing output signals in the receiver coil which can be synchronously demodulated to yield a periodic envelope containing integral harmonics of the oscillating gradient frequency. This periodic envelope is subjected to synchronous detection, continuously yielding the amplitudes of the individual harmonic components of the envelope which are then used to approximate an integral equation by a matrix solution to a linear transformation which generates the Radon transform of the transverse magnetization along the direction of the oscillating gradient, permitting image reconstruction. Truncation (Gibbs) artefacts are eliminated. Synchronous demodulation and synchronous detection of the impulse spectrum of the output signal from the receiver coil suppresses the continuous spectrum Johnson noise. The very weak higher harmonics are synchronously detected over multiple periods yielding an improved estimate of their central tendency.
Inventors
- 👤 Ernest Wollin
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 06:01
CPC Classifications
G; G01; G01F; G01F1/00; G01F1/704; G01F1/708; G01F1/716; G01R; G01R33/00; G01R33/20; G01R33/44; G01R33/48; G01R33/54; G01R33/56; G01R33/563
Claims Analysis
Total Claims: 25
Claim 1
Independent Claim
158 words
An apparatus for detecting fluid flow, comprising: means for generating a homogeneous magnetic field along a longitudinal axis of a pipe for containing said fluid flow; a plurality of conductive wires arranged in parallel to each other and to said pipe and formed in a shape of a cylinder; a first ring conductor for joining said conductive wires at one end of said conductive wires; a second ring conductor for joining said conductive wires at an end opposite said one end of said conductive wires; means for generating a time varying voltage and for applying said time varying voltage to at least one pair of said plurality of conductive wires; said time varying voltage producing a time varying electric field in said pipe and a linear magnetic field gradient in said pipe: and means for detecting output signals generated by fluid within said pipe and for determining a characteristic of said fluid flow based on said output signals.
Claim 2
Independent Claim
158 words
An apparatus for detecting fluid flow, comprising: means for generating a homogeneous magnetic field along a longitudinal axis of a pipe for containing said fluid flow; a plurality of conductive wires arranged in parallel to each other and to said pipe and formed in a shape of a cylinder; a first ring conductor for joining said conductive wires at one end of said conductive wires; a second ring conductor for joining said conductive wires at an end opposite said one end of said conductive wires; means for generating a time varying voltage and for applying said time varying voltage to at least one pair of said plurality of conductive wires; said time varying voltage producing a time varying electric field in said pipe and a linear magnetic field gradient in said pipe: and means for detecting output signals generated by fluid within said pipe and for determining a characteristic of said fluid flow based on said output signals.
Claim 3
Dependent Claim
29 words
An apparatus as set forth in claim 1, wherein said conductive wires are arranged in a bird cage configuration that is tuned to a Larmor frequency of said fluid.
Claim 4
Dependent Claim
50 words
An apparatus as set forth in claim 1, further comprising: means for generating RF fields having a frequency centered near a Larmor frequency of said fluid; and means for applying said RF fields to said conductive wires; wherein said RF fields become circularly polarized and rotate about said conductive wires.
Claim 5
Dependent Claim
66 words
An apparatus as set forth in claim 1, further comprising: a first set of filters connected on said first ring conductor between said conductive wires for tuning said conductive wires near a Larmor frequency of said fluid; and a second set of filters connected between said applying means and said first ring conductor for passing through said first frequency and for filtering out said Larmor frequency.
Claim 6
Dependent Claim
37 words
An apparatus as set forth in claim 1, wherein said conductive wires comprise said detecting means and said apparatus further comprises means for processing the output signals in order to produce an image of said fluid flow.
Claim 7
Dependent Claim
99 words
An MRI apparatus for producing an image of an object, comprising: means for generating oscillating gradients to modulate an angular momentum of spins of nuclei within said object and for producing output signals which are detected in a receiver coil; means for synchronously demodulating said output signals to yield a periodic envelope signal containing integral harmonics of an oscillating gradient frequency; means for synchronously detecting said periodic envelope signal to yield individual harmonic components of the envelope signal; and means for reconstructing the image of the object by approximation using a matrix solution using the detected periodic envelope signal.
Claim 8
Dependent Claim
99 words
An MRI apparatus for producing an image of an object, comprising: means for generating oscillating gradients to modulate an angular momentum of spins of nuclei within said object and for producing output signals which are detected in a receiver coil; means for synchronously demodulating said output signals to yield a periodic envelope signal containing integral harmonics of an oscillating gradient frequency; means for synchronously detecting said periodic envelope signal to yield individual harmonic components of the envelope signal; and means for reconstructing the image of the object by approximation using a matrix solution using the detected periodic envelope signal.
Claim 9
Independent Claim
111 words
A method for detecting fluid flow through a pipe, comprising the steps of: producing a homogeneous magnetic field throughout of a certain length of said pipe and along a first axis concentric with a longitudinal axis of the pipe; generating a radiofreguency signal; receiving at a receiving means said radiofrequency signal and generating radiofrequency fields across said pipe within said certain length in order to excite spins of nuclei within said fluid; detecting signals emitted by said nuclei within said fluid after the step of generating said radiofrequency fields; and processing the detected signals and mapping said fluid flow; wherein said radiofrequency fields produce linear magnetic field gradients in said fluid.
Claim 10
Independent Claim
111 words
A method for detecting fluid flow through a pipe, comprising the steps of: producing a homogeneous magnetic field throughout of a certain length of said pipe and along a first axis concentric with a longitudinal axis of the pipe; generating a radiofreguency signal; receiving at a receiving means said radiofrequency signal and generating radiofrequency fields across said pipe within said certain length in order to excite spins of nuclei within said fluid; detecting signals emitted by said nuclei within said fluid after the step of generating said radiofrequency fields; and processing the detected signals and mapping said fluid flow; wherein said radiofrequency fields produce linear magnetic field gradients in said fluid.
Claim 11
Dependent Claim
93 words
A method for generating images as set forth in claim 7, further comprising the steps of: arranging a plurality of conductive wires in parallel to each other in a shape of a cylinder around the pipe; joining said plurality of conductive wires with a first ring conductor at one end of said conductive wires; joining said plurality of conductive wires with a second ring conductor at an end opposite said one end of said conductive wires; wherein said first electric field rotates about said conductive wires at said Larmor frequency of said fluid.
Claim 12
Dependent Claim
34 words
A method for generating images as set forth in claim 33, wherein said step of generating said radiofrequency fields is performed by an antenna structure that also performs said step of detecting said signals.
Claim 13
Dependent Claim
30 words
A method for generating images as set forth in claim 7, wherein said step of processing uses a projection reconstruction technique to produce an image of flow of said fluid.
Claim 14
Dependent Claim
40 words
A method for generating images as set forth in claim 7, wherein said step of processing employs at least one look up table containing Bessel functions when processing said detected signals to produce an image of flow of said fluid.
Claim 15
Dependent Claim
42 words
A method for generating images as set forth in claim 7, wherein said step of processing employs at least one look up table containing solutions to Sommerfeld's integral when processing an detected signals to produce said image of flow of said fluid.
Claim 16
Dependent Claim
19 words
The MRI apparatus as set forth in claim 6, wherein said demodulating means comprises a synchronous double balanced demodulator.
Claim 17
Dependent Claim
30 words
(Newly Added) The MRI apparatus as set forth in claim 6, wherein said detecting means comprises an integrator for determining amplitudes of said individual harmonic components of the envelope signal.
Claim 18
Dependent Claim
58 words
The MRI apparatus as set forth in claim 6, wherein said detecting means comprises: an isolation amplifier for receiving said periodic envelope signal; a double balanced demodulator for receiving an output of said isolation amplifier; and an integrator for integrating an output of said double balanced demodulator and for generating said individual harmonic components of the envelope signal.
Claim 19
Dependent Claim
16 words
The apparatus as set forth in claim 1, wherein said generating means comprises a solenoid coil.
Claim 20
Dependent Claim
26 words
The apparatus as set forth in claim 1, wherein said pipe is non-conductive and nonferromagnetic and said plurality of conductive wires are positioned outside said pipe.
Claim 21
Dependent Claim
24 words
The apparatus as set forth in claim 1, wherein said generating means produces a pulse for flipping spins of nuclei within said fluid flow.
Claim 22
Dependent Claim
31 words
The apparatus as set forth in claim 1, wherein said generating means continuously generates a radiofrequency field to produce a spatially phase encoded transverse magnetization in nuclei within said fluid flow.
Claim 23
Dependent Claim
22 words
The apparatus as set forth in claim 1, wherein said detecting means maps the characteristic of flow velocity for said fluid flow.
Claim 24
Dependent Claim
35 words
The method as set forth in claim 7, wherein said step of generating said radiofrequency fields comprises the step of pulsing radiofrequency fields so as to repetitively flip spins of said nuclei within said fluid.
Claim 25
Dependent Claim
25 words
The method as set forth in claim 7, wherein said step of generating said radiofrequency fields comprises the step of continuously producing said radiofrequency fields.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 2001-05-25 | 2001-11-24 | 2002-05-26 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2005-05-25 | 2005-11-24 | 2006-05-26 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2009-05-25 | 2009-11-24 | 2010-05-26 | $7700.00 | Window Closed / Lapsed |