US5162730A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Method for operating a magnetic resonant imaging tomography apparatus
Assignee: Siemens AG
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Filing: 1990-11-13
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Granted: 1992-11-10
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Expires: 2010-11-13
Abstract
Abstract A method, in the form of a pulse sequence for operating a magnetic resonance imaging tomography apparatus according to a modification of the echo planar method includes the generation of a read-out gradient consisting of sub-pulses having reversing polarity, the read-out gradient being activated in each scan after an RF excitation. A phase coding gradient, also consisting of a number of sub-pulses, is activated at each polarity change of the read-out gradient. The sub-pulses of the phase coding gradient have a polarity which alternates from sub-pulse to sub-pulse, and an amplitude-time area which increases in steps. An improved signal-to-noise ratio is achieved with this pulse sequence and N/2 ghosts are avoided.
Inventors
- 👤 Franz Schmitt
- 👤 Hubertus Fischer
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-07 19:36
CPC Classifications
G; G01; G01R; G01R33/00; G01R33/20; G01R33/44; G01R33/48; G01R33/54; G01R33/56; G01R33/561; G01R33/5615; G01R33/5616
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
178 words
A method for operating a magnetic resonance imaging apparatus for obtaining a tomogram of an examination subject, comprising the steps of: subjecting said examination subject to an RF excitation pulse to excite nuclear spins in said examination subject and thereby to produce nuclear magnetic resonance signals; reading out said nuclear magnetic resonance signals under a read-out gradient consisting of a plurality of pulses of alternating polarity; phase coding the read out nuclear magnetic resonance signals by generating a phase coding gradient after said RF excitation pulse, said phase coding gradient consisting of a plurality of pulses, respectively occurring at each change in polarity of said read-out gradient, and alternating in polarity from pulse to pulse and having an amplitude-time area increasing in steps from pulse to pulse; digitizing the read-out nuclear magnetic resonance signals; entering the digitized read-out nuclear magnetic resonance signals from each pulse of said read-out gradient into respective rows of a raw data matrix in K-space controlled by the phase factors of said phase coding gradient; and constructing a tomogram from said raw data matrix.
Claim 2
Independent Claim
178 words
A method for operating a magnetic resonance imaging apparatus for obtaining a tomogram of an examination subject, comprising the steps of: subjecting said examination subject to an RF excitation pulse to excite nuclear spins in said examination subject and thereby to produce nuclear magnetic resonance signals; reading out said nuclear magnetic resonance signals under a read-out gradient consisting of a plurality of pulses of alternating polarity; phase coding the read out nuclear magnetic resonance signals by generating a phase coding gradient after said RF excitation pulse, said phase coding gradient consisting of a plurality of pulses, respectively occurring at each change in polarity of said read-out gradient, and alternating in polarity from pulse to pulse and having an amplitude-time area increasing in steps from pulse to pulse; digitizing the read-out nuclear magnetic resonance signals; entering the digitized read-out nuclear magnetic resonance signals from each pulse of said read-out gradient into respective rows of a raw data matrix in K-space controlled by the phase factors of said phase coding gradient; and constructing a tomogram from said raw data matrix.
Claim 3
Dependent Claim
40 words
A method as claimed in claim 1 wherein the step of phase coding the readout nuclear magnetic resonance signals is further defined by generating a phase coding gradient having an amplitude-time area increasing in constant steps from pulse to pulse.
Claim 4
Dependent Claim
35 words
A method as claimed in claim 1 wherein the step of phase coding the readout nuclear magnetic resonance signals is further defined by generating a phase coding gradient consisting of pulses having identical chronological duration.
Claim 5
Dependent Claim
32 words
A method as claimed in claim 1 comprising the additional step of: generating a pre-phasing pulse in the direction of said phase coding gradient before a first pulse of said read-out gradient.
Claim 6
Dependent Claim
98 words
A method as claimed in claim 1 wherein said raw data matrix has central rows, and wherein the step of phase coding the read out nuclear magnetic resonance signals is further defined by generating said phase coding gradient having pulses alternating in polarity from pulse to pulse and pulses having an amplitude-time area increasing in steps from pulse to pulse only during read-out of said nuclear magnetic resonance signals for said central rows of said raw data matrix, and thereafter generating a phase coding gradient consisting of a plurality of pulses of constant polarity and constant amplitude-time area.
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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) | 1995-11-10 | 1996-05-11 | 1996-11-10 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1999-11-10 | 2000-05-11 | 2000-11-10 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2003-11-10 | 2004-05-11 | 2004-11-10 | $7700.00 | Window Closed / Lapsed |