EP0204320A2
Expired / Lapsed
EP
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Magnetic resonance imaging method
Assignee: Hitachi Ltd
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Filing: 1986-06-03
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Granted: —
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Expires: 2006-06-03
Abstract
Abstract In order to measure a static field distribution with one scanning operation and to make image distortion corrections with the static field distribution and a gradient field distribution simultaneously considered, an image is reconstructed using a spin echo signal produced under the condition that a time interval between a 90° pulse and a 180° pulse differs from an interval between the 180° pulse and the time origin of the spin echo signal, the static field distribution is evaluated from the relation of distortions to phase errors free from a phase distortion attributed to the characteristic of a detecting part and a phase distortion attributed to the dynamic characteristic of the gradient field, a relations existing between the spatial distortion and phase distortion of the reconstructed image and a magneticfeild distribution including the gradient field is obtained, and the distortion magnitude of the reconstructed image is evaluated from the measured magnetic field distribution.
Inventors
- 👤 Koichi Sano
- 👤 Tetsuro Yokohama
- 👤 Hideaki Koizumi
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-24 01:25
CPC Classifications
G; G01; G01R; G01R33/00; G01R33/20; G01R33/44; G01R33/48; G01R33/54; G01R33/56; G01R33/565; G01R33/56518; G01R33/56563
Claims Analysis
Total Claims: 13
Claim 1
Independent Claim
146 words
In an NMR imaging apparatus having magnetic field generation means to generate a static field, a gradient field and an RF field, detection means to detect an NMR signal from an object to-be-imaged, and calculation means to subject the detected signal to a calculation for reconstructing an image; an NMR imaging method characterized by sampling a spin echo signal produced under a condition that a time interval between a 90 ° pulse and a 180 ° pulse generated by said magnetic field generation means differs from an interval between the 180 ° pulse and a time origin of the spin echo signal, subjecting such sampled signals to reconstruction of images which includes processing for correcting phase errors attributed to said detection means and phase errors attributed to the different sampling time intervals, and evaluating a static field distribution from a relationship between phase magnitudes and distortions.
Claim 2
Dependent Claim
146 words
In an NMR imaging apparatus having magnetic field generation means to generate a static field, a gradient field and an RF field, detection means to detect an NMR signal from an object to-be-imaged, and calculation means to subject the detected signal to a calculation for reconstructing an image; an NMR imaging method characterized by sampling a spin echo signal produced under a condition that a time interval between a 90 ° pulse and a 180 ° pulse generated by said magnetic field generation means differs from an interval between the 180 ° pulse and a time origin of the spin echo signal, subjecting such sampled signals to reconstruction of images which includes processing for correcting phase errors attributed to said detection means and phase errors attributed to the different sampling time intervals, and evaluating a static field distribution from a relationship between phase magnitudes and distortions.
Claim 3
Dependent Claim
52 words
An NMR imaging method according to Claim 1, wherein in the sampling, an origin of a sampling axis is so set that the time interval between the 90 ° pulse and the 180 ° pulse equalizes to a time interval between the 180 ° pulse and the origin of the sampling axis.
Claim 4
Dependent Claim
31 words
An NMR imaging method according to Claim 1, wherein in the sampling, an origin of a sampling axis is brought into agreement with the time origin of the spin echo signal.
Claim 5
Dependent Claim
119 words
In an NMR imaging apparatus having means to generate a static field, a gradient field and an RF field, detection means to derive an NMR signal from an object to-be-examined, and means to subject the detected signal to various calculations including reconstruction of an image; an NMR imaging method characterized by executing the image reconstruction with a spin echo signal produced under a condition that a time interval between a 90 ° pulse and a 180 ° pulse differs from an interval between the 180 ° pulse and a time origin of the spin echo signal, and measuring a static field distribution and a gradient field distribution from spatial distortion magnitudes and phase distortion magnitudes of the reconstructed images.
Claim 6
Dependent Claim
119 words
In an NMR imaging apparatus having means to generate a static field, a gradient field and an RF field, detection means to derive an NMR signal from an object to-be-examined, and means to subject the detected signal to various calculations including reconstruction of an image; an NMR imaging method characterized by executing the image reconstruction with a spin echo signal produced under a condition that a time interval between a 90 ° pulse and a 180 ° pulse differs from an interval between the 180 ° pulse and a time origin of the spin echo signal, and measuring a static field distribution and a gradient field distribution from spatial distortion magnitudes and phase distortion magnitudes of the reconstructed images.
Claim 7
Dependent Claim
26 words
An NMR imaging method according to Claim 4, wherein the static field distribution and the gradient field distribution are measured from only the spatial distortion magnitudes.
Claim 8
Dependent Claim
79 words
In an NMR imaging apparatus having means to generate a static field, a gradient field and an RF field, detection means to derive an NMR signal from an object to-be-examined, and means to subject the detected signal to various calculations including reconstruction of an image; an NMR imaging method characterized by correcting spatial distortions, density distortions and phase distortions of reconstructed images on the basis of spatial inhomogeneities of the static field and the gradient field measured in advance.
Claim 9
Dependent Claim
79 words
In an NMR imaging apparatus having means to generate a static field, a gradient field and an RF field, detection means to derive an NMR signal from an object to-be-examined, and means to subject the detected signal to various calculations including reconstruction of an image; an NMR imaging method characterized by correcting spatial distortions, density distortions and phase distortions of reconstructed images on the basis of spatial inhomogeneities of the static field and the gradient field measured in advance.
Claim 10
Dependent Claim
22 words
The missing page 8 is submitted, in triplicate, which should be inserted between pages 7 and 9 of the originally filed description.
Claim 11
Dependent Claim
22 words
The missing page 8 is submitted, in triplicate, which should be inserted between pages 7 and 9 of the originally filed description.
Claim 12
Dependent Claim
33 words
According to Rule 88, it is requested to correct the description. This correction is obvious since it merely explains further steps following Formula (1) on page 7 to Formula (6) on page 9.
Claim 13
Dependent Claim
33 words
According to Rule 88, it is requested to correct the description. This correction is obvious since it merely explains further steps following Formula (1) on page 7 to Formula (6) on page 9.
References Cited (Backward Citations)
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