Patent CA1009339A successfully refreshed from Google Patents.
Patent US4821016A successfully refreshed from Google Patents.
Patent CH569141B5 successfully refreshed from Google Patents.
US5070876A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Flow-independent magnetic resonance projection angiography
Assignee: Leland Stanford Junior University
•
Filing: 1989-08-07
•
Granted: 1991-12-10
•
Expires: 2009-08-07
Abstract
Abstract The performance of current, flow-based sequences for imaging vasculature using MR is severely restricted in regions with inherently slow flow. We address this problem with a flow-independent imaging method. Specifically, we generate projection images of blood in the limbs while suppressing signals from all other tissues (primarily skeletal muscle, bone marrow, and subcutaneous fat) using a flow-compensated, water-selective, short TI inversion recovery sequence with a long echo time. We experimentally evaluate the effectiveness of this sequence and present in vivo results clearly demonstrating the method's potential.
Inventors
- 👤 Graham A. Wright
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-06 19:39
CPC Classifications
G; G01; G01R; G01R33/00; G01R33/20; G01R33/44; G01R33/48; G01R33/54; G01R33/56; G01R33/563; G01R33/565; G01R33/56509
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
137 words
A signal acquisition method for use in flow-independent magnetic resonance projection angiography comprising the steps of a) positioning a body having muscle, fat, and blood in a static magnetic field, b) applying a first RF pulse to flip magnetic spins of atoms in said body by 180°, c) applying a second RF pulse after a time period related to T1 of fat to differentiate magnetic spins of fat from magnetic spins of muscle and blood, d) applying a sequence of 180° RF pulses to refocus magnetic spins of blood and increase the T2 time for blood and permit acquisition of data at a late echo time and thereby differentiate magnetic spins of muscle from magnetic spins of blood, e) applying orthogonal linear gradients to detect a spin echo from blood, and f) detecting a spin echo signal.
Claim 2
Dependent Claim
137 words
A signal acquisition method for use in flow-independent magnetic resonance projection angiography comprising the steps of a) positioning a body having muscle, fat, and blood in a static magnetic field, b) applying a first RF pulse to flip magnetic spins of atoms in said body by 180°, c) applying a second RF pulse after a time period related to T1 of fat to differentiate magnetic spins of fat from magnetic spins of muscle and blood, d) applying a sequence of 180° RF pulses to refocus magnetic spins of blood and increase the T2 time for blood and permit acquisition of data at a late echo time and thereby differentiate magnetic spins of muscle from magnetic spins of blood, e) applying orthogonal linear gradients to detect a spin echo from blood, and f) detecting a spin echo signal.
Claim 3
Dependent Claim
22 words
The method as defined by claim 1 wherein said step of applying a second RF pulse includes applying a 90° RF pulse.
Claim 4
Dependent Claim
30 words
The method as defined by claim 1 wherein said step of applying a second RF pulse includes applying a frequency selective group of pulses for flipping magnetic spins of water.
Claim 5
Dependent Claim
24 words
The method as defined in claim 1 wherein said step of applying a sequence of 180° pulses comprises applying a MLEV refocussing echo train.
Claim 6
Dependent Claim
36 words
The method as defined by claim 1 wherein said step of applying orthogonal linear gradients includes applying spoiling gradients along one axis, a phase encode gradient along another axis, and a readout gradient along another axis.
Claim 7
Dependent Claim
126 words
A signal acquisition method for use in flow-independent magnetic resonace projection angiography comprising the steps of a) positioning a body having muscle, fat and blood in a static magnetic field, b) applying a frequency selective group of pulses for flipping magnetic spins of water after a time period related to the relaxation time T1 of fat to differentiate magnetic spins of fat from magnetic spins of muscle and blood, c) applying a sequence of 180° RF pulses to refocus magnetic spins of blood and increase the relaxation time T2 for blood and permit acquisition of data at a late echo time and thereby differentiate muscle from blood, d) applying orthogonal linear gradients to detect a spin echo from blood, and e) detecting a spin echo signal.
Claim 8
Dependent Claim
126 words
A signal acquisition method for use in flow-independent magnetic resonace projection angiography comprising the steps of a) positioning a body having muscle, fat and blood in a static magnetic field, b) applying a frequency selective group of pulses for flipping magnetic spins of water after a time period related to the relaxation time T1 of fat to differentiate magnetic spins of fat from magnetic spins of muscle and blood, c) applying a sequence of 180° RF pulses to refocus magnetic spins of blood and increase the relaxation time T2 for blood and permit acquisition of data at a late echo time and thereby differentiate muscle from blood, d) applying orthogonal linear gradients to detect a spin echo from blood, and e) detecting a spin echo signal.
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) | 1994-12-09 | 1995-06-10 | 1995-12-10 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1998-12-09 | 1999-06-10 | 1999-12-10 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2002-12-09 | 2003-06-10 | 2003-12-10 | $7700.00 | Window Closed / Lapsed |