Patent US992022A successfully refreshed from Google Patents.
Patent US4985677A successfully refreshed from Google Patents.
US4985677A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Magnetic resonance imaging and spectroscopy using an excitation pulse for multiple-dimensional selectivity
Assignee: Leland Stanford Junior University
•
Filing: 1989-06-22
•
Granted: 1991-01-15
•
Expires: 2009-06-22
Abstract
Abstract A method of obtaining multi-dimensional spatially-selective magnetic resonance signals from a body includes applying a static magnetic field (Bo) to said body thereby aligning nuclear spins along an axis (z), and applying one or more time-varying magnetic gradients (Gx(t), Gy(t), Gz(t)) during a time period, T. During the time period, T, an RF excitation pulse (B 1 ) is applied to said body to tip said nuclear spins, said RF excitation pulse being related to said modulated magnetic gradients by a first spatial frequency weighting function (W(k)(t)) whereby magnetic resonance signals transmitted by said tipped nuclear spins are spatially selective in multi dimensions. The resulting magnetic resonance signals are then detected to provide the multi-dimensional spatially-selective signals.
Inventors
- 👤 John M. Pauly
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-07 08:12
CPC Classifications
G; G01; G01R; G01R33/00; G01R33/20; G01R33/44; G01R33/446
Claims Analysis
Total Claims: 14
Claim 1
Independent Claim
130 words
A method of obtaining multi-dimensional spatially selective magnetic resonance signals from a body comprising the steps of (a) applying a static magnetic field (Bo) to said body thereby aligning nuclear spins along an axis (z), (b) applying multiple time varying magnetic gradients Gx(t), Gy(t), Gz(t) during a time period, T, with said gradients chosen so that a region of spatial frequency space is covered, (c) applying during said time period, T, an RF excitation pulse (B 1 ) to said body to tip said nuclear spins said RF excitation pulse being related to said times varying magnetic gradients by a first spatial frequency weighting function (W(k)(t)) whereby magnetic resonance signals transmitted by said tipped nuclear spins are spatially selective in multiple dimensions, (x,y,z), and (d) detecting said magnetic resonance signals.
Claim 2
Independent Claim
130 words
A method of obtaining multi-dimensional spatially selective magnetic resonance signals from a body comprising the steps of (a) applying a static magnetic field (Bo) to said body thereby aligning nuclear spins along an axis (z), (b) applying multiple time varying magnetic gradients Gx(t), Gy(t), Gz(t) during a time period, T, with said gradients chosen so that a region of spatial frequency space is covered, (c) applying during said time period, T, an RF excitation pulse (B 1 ) to said body to tip said nuclear spins said RF excitation pulse being related to said times varying magnetic gradients by a first spatial frequency weighting function (W(k)(t)) whereby magnetic resonance signals transmitted by said tipped nuclear spins are spatially selective in multiple dimensions, (x,y,z), and (d) detecting said magnetic resonance signals.
Claim 3
Dependent Claim
29 words
The method as defined by claim 1 wherein the k-space trajectory of said RF excitation pulse ends at the k-space origin, whereby said RF excitation pulse is inherently refocused.
Claim 4
Dependent Claim
61 words
The method as defined by claim 2 wherein a spatial frequency variable k(t) is defined as ##EQU16## and a spatial weighting function W(k(t) is defined as ##EQU17## and a sampling structure S(k) is defined as ##EQU18## whereby the transverse magnetization is the Fourier transform of the spatial frequency weighting multiplied by the spatial frequency sampling function M.sub.χυ (x)=iγM.sub.O .sub.K W(k)S(k)e.sup.iχ.k dk.
Claim 5
Dependent Claim
44 words
The method as defined by claim 1 wherein step (b) includes applying said two magnetic gradients with a second spatial weighting frequency weighting function (D(k)) which is related to said first spatial weighting function by a spatial frequency sampling function (S(k)) as follows: W(k)S(k)≈D(k)
Claim 6
Dependent Claim
44 words
The method as defined by claim 4 wherein said magnetic gradients are defined as ##EQU19## where A=determines the size of a spiral scanning trajectory in spatial frequency, or k-space, n=number of cycles in said spiral scanning trajectory, γ=magnetogyric ratio for a selected nuclear species.
Claim 7
Dependent Claim
31 words
The method as defined by claim 5 wherein step (c) includes applying an RF excitation pulse defined as follows: ##EQU20## where α=a tip angle scale β=spatial resolution of a selective volume.
Claim 8
Dependent Claim
131 words
Apparatus for obtaining multi-dimensional spatially selective magnetic resonance signals comprising, (a) means for applying a static magnetic field (Bo) to said body thereby aligning nuclear spins along an axis (z), (b) means for applying multiple time varying magnetic gradients (Gx(t), Gy(t), Gz(t)) during a time period, T, with said gradients chosen so that a region of spatial frequency space is covered, (c) means for applying during said time period, T, an RF excitation pulse (B 1 ) to said body to tip said nuclear spins, said RF excitation pulse being related to said time varying magnetic gradients by a first spatial frequency weighting function (W(k)(t)) whereby magnetic resonance signals transmitted by said tipped nuclear spins are spatially selective in two dimensions, (χ,Y), and (d) means for detecting said magnetic resonance signals.
Claim 9
Dependent Claim
131 words
Apparatus for obtaining multi-dimensional spatially selective magnetic resonance signals comprising, (a) means for applying a static magnetic field (Bo) to said body thereby aligning nuclear spins along an axis (z), (b) means for applying multiple time varying magnetic gradients (Gx(t), Gy(t), Gz(t)) during a time period, T, with said gradients chosen so that a region of spatial frequency space is covered, (c) means for applying during said time period, T, an RF excitation pulse (B 1 ) to said body to tip said nuclear spins, said RF excitation pulse being related to said time varying magnetic gradients by a first spatial frequency weighting function (W(k)(t)) whereby magnetic resonance signals transmitted by said tipped nuclear spins are spatially selective in two dimensions, (χ,Y), and (d) means for detecting said magnetic resonance signals.
Claim 10
Dependent Claim
44 words
Apparatus as defined by claim 7 wherein said means for applying two magnetic gradients applies gradients with a second spatial weighting frequency weighting function (D(h)) which is related to said first spatial weighting function by a spatial frequency sampling function (S(k) as follows: W(k)S(k)≈D(k).
Claim 11
Dependent Claim
43 words
Apparatus as defined by claim 8 wherein said magnetic gradients are defined as ##EQU21## where A=determines the size of a spiral scanning trajectory in spatial frequency, or k-space, n=number of cycles in said spiral scanning trajectory, γ=magnetogyric ratio for a selected nuclear species.
Claim 12
Dependent Claim
27 words
Apparatus as defined by claim 9 wherein said RF excitation pulse is defined as follows: ##EQU22## where =a tip angle scale β=spatial resolution of a selective volume.
Claim 13
Dependent Claim
28 words
Apparatus as defined by claim 7 wherein the k-space trajectory of said RF excitation pulse ends at the k-space origin, whereby said RF excitation pulse is inherently refocused.
Claim 14
Dependent Claim
60 words
Apparatus as defined by claim 11 wherein a spatial frequency variable k(t) is defined as ##EQU23## and a spatial weighting function W(k(t)) is defined as ##EQU24## and a sampling structure S(k) is defined as ##EQU25## whereby the transverse magnetization is the Fourier transform of the spatial frequency weighting multiplied by the spatial frequency sampling function M.sub.χυ (x)=iγM.sub.O .sub.K W(k)S(k)e.sup.ix.k dk.
References Cited (Backward Citations)
US4307343A
Cited
US4642567A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1994-01-14 | 1994-07-16 | 1995-01-15 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1998-01-14 | 1998-07-16 | 1999-01-15 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2002-01-14 | 2002-07-16 | 2003-01-15 | $7700.00 | Window Closed / Lapsed |