US5619138A
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Method of providing an RF pulse for use in NMR
Assignee: National Research Council Canada
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Filing: 1995-08-21
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Granted: 1997-04-08
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Expires: 2015-08-21
Abstract
Abstract The invention relates to a method of determining prefocused pulses with sufficiently low power and short duration to allow multi-slice in-vivo spectroscopic imaging of humans. The method has two main stages, analytic and numerical. In the analytic stage a magnetization response is selected with certain desired characteristics such as prefocused time. During the numerical stage, the response is then transformed into an RF pulse for use in magnetic resonance imaging. The theoretical response to the RF pulse is evaluated and characteristics such as duration and amplitude may be altered to meet further requirements. The theoretical response is then transformed into an RF pulse for use in magnetic resonance imaging or for further application of the numerical stage.
Inventors
- 👤 David E. Rourke
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-07 18:10
CPC Classifications
G; G01; G01R; G01R33/00; G01R33/20; G01R33/44; G01R33/446; G01R33/48; G01R33/483; G01R33/4833; G01R33/4835
Claims Analysis
Total Claims: 21
Claim 1
Independent Claim
67 words
A method of providing an RF pulse for use in MRI comprising the steps of: (a) selecting a reflection coefficient related to a predetermined magnetization response; (b) iteratively altering the reflection coefficient and evaluating a corresponding magnetization response and RF pulse until the corresponding magnetization response and RF pulse are within predetermined parameters; and (c) providing a representation of an RF pulse based on the reflection coefficient.
Claim 2
Independent Claim
67 words
A method of providing an RF pulse for use in MRI comprising the steps of: (a) selecting a reflection coefficient related to a predetermined magnetization response; (b) iteratively altering the reflection coefficient and evaluating a corresponding magnetization response and RF pulse until the corresponding magnetization response and RF pulse are within predetermined parameters; and (c) providing a representation of an RF pulse based on the reflection coefficient.
Claim 3
Dependent Claim
17 words
The method of claim 1 wherein a predefined pseudo random method is used to preform the optimization.
Claim 4
Dependent Claim
18 words
The method of claim 2 wherein a predetermined cost function is used to evaluate results of each iteration.
Claim 5
Dependent Claim
16 words
The method of claim 1 wherein the reflection coefficient is selected from equations for bandpass filters.
Claim 6
Dependent Claim
16 words
The method of claim 4 wherein the reflection coefficient corresponds to a Chebyshev I filter response.
Claim 7
Dependent Claim
14 words
The method of claim 4 wherein the reflection coefficient corresponds a Butterworth filter response.
Claim 8
Dependent Claim
22 words
The method of claim 1 further comprising the step of providing the representation of the RF pulse to a pulse generating means.
Claim 9
Independent Claim
103 words
A method of providing an RF pulse for use in MRI comprising the steps of: (a) selecting a reflection coefficient related to a predetermined magnetization response; (b) iteratively performing the following steps: (i) providing a representation of an RF pulse based on the reflection coefficient; (ii) determining the magnetization response of the representation; (iii) when the magnetization response and the RF pulse are not within predetermined parameters optimizing the reflection coefficient and returning to step (b) until the magnetization response and the RF pulse are within predetermined parameters; and (c) providing a final representation of an RF pulse based on the reflection coefficient.
Claim 10
Independent Claim
103 words
A method of providing an RF pulse for use in MRI comprising the steps of: (a) selecting a reflection coefficient related to a predetermined magnetization response; (b) iteratively performing the following steps: (i) providing a representation of an RF pulse based on the reflection coefficient; (ii) determining the magnetization response of the representation; (iii) when the magnetization response and the RF pulse are not within predetermined parameters optimizing the reflection coefficient and returning to step (b) until the magnetization response and the RF pulse are within predetermined parameters; and (c) providing a final representation of an RF pulse based on the reflection coefficient.
Claim 11
Dependent Claim
20 words
The method of claim 8 wherein the soliton lattice algorithm is used to provide the representation of the RF pulse.
Claim 12
Dependent Claim
17 words
The method of claim 8 wherein a predefined pseudo random method is used to perform the optimization.
Claim 13
Dependent Claim
18 words
The method of claim 8 wherein a predetermined cost function is used to evaluate results of each iteration.
Claim 14
Dependent Claim
15 words
The method of claim 8 wherein the reflection coefficient corresponds to a bandpass filter response.
Claim 15
Dependent Claim
16 words
The method of claim 12 wherein the reflection coefficient corresponds to a Chebyshev I filter response.
Claim 16
Dependent Claim
15 words
The method of claim 12 wherein the reflection coefficient corresponds to a Butterworth filter response.
Claim 17
Dependent Claim
22 words
The method of claim 8 further comprising the step of providing the representation of the RF pulse to a pulse generating means.
Claim 18
Independent Claim
147 words
A method of providing an RF pulse for use in MRI comprising the steps of: (a) selecting a reflection coefficient related to C n , a Chebyshev I filter response of order n, by the equation r(ξ)=i/(1+ε 2 C n 2 (ξ)) wherein i is an integer, C n 2 (ξ)=(cos(n cos -1 ξ)) 2 , ξ=Ω/Ω c , Ω c is specified by the desired cutoff frequency, and ε is specified by the allowable passband ripple; (b) using a soliton lattice algorithm and the reflection coefficient to provide a representation of an RF pulse; (c) determining the magnetization response of the representation; (d) when the magnetization response and the RF pulse are not within predetermined parameters optimizing the reflection coefficient based on a predetermined cost function and returning to step (b); and (e) providing a final representation of an RF pulse based on the reflection coefficient.
Claim 19
Independent Claim
147 words
A method of providing an RF pulse for use in MRI comprising the steps of: (a) selecting a reflection coefficient related to C n , a Chebyshev I filter response of order n, by the equation r(ξ)=i/(1+ε 2 C n 2 (ξ)) wherein i is an integer, C n 2 (ξ)=(cos(n cos -1 ξ)) 2 , ξ=Ω/Ω c , Ω c is specified by the desired cutoff frequency, and ε is specified by the allowable passband ripple; (b) using a soliton lattice algorithm and the reflection coefficient to provide a representation of an RF pulse; (c) determining the magnetization response of the representation; (d) when the magnetization response and the RF pulse are not within predetermined parameters optimizing the reflection coefficient based on a predetermined cost function and returning to step (b); and (e) providing a final representation of an RF pulse based on the reflection coefficient.
Claim 20
Dependent Claim
9 words
The method of claim 16 wherein n=10, and ε=0.2.
Claim 21
Dependent Claim
22 words
The method of claim 16 further comprising the step of providing the representation of the RF pulse to a pulse generating means.
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) | 2000-04-07 | 2000-10-07 | 2001-04-08 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2004-04-07 | 2004-10-07 | 2005-04-08 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2008-04-07 | 2008-10-07 | 2009-04-08 | $7700.00 | Window Closed / Lapsed |