Magnetic resonance imaging method and device therefor
First Claim
1. A magnetic resonance imaging method in which after irradiating RF pulses of magnetic resonance frequencies into an object to be inspected, a step of running a sequence for detecting echo signals sequentially and a step of reconstructing an image by making use of the detected echo signals which are repeated in parallel, and subsequent images are obtained by successively renewing a part of the echo signals used for reconstructing the previous image, characterized in that, a navigator echo is generated for every irradiation of the RF pulses and is detected, wherein one generated navigator echo which serves as a reference for correcting phases of the echo signals used for the image reconstruction and is successively renewed for every image, and phases of the echo signals are corrected based on the renewed navigator echo for every image.
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Abstract
In a magnetic resonance imaging method in which after irradiating RF pulses of magnetic resonance frequencies into an object to be inspected, a sequence of detecting echo signals sequentially and a step of reconstructing an image by making use of the obtained echo signals are repeated in parallel, and an animating image is obtained by successively renewing a part of the echo signals used for reconstructing the previous image, a navigator echo is generated for every irradiation of the RF pulses and is detected, a navigator echo which serves as a reference for correcting phases of the echo signals used for the image reconstruction is successively renewed for every image, and the phases of the echo signals are corrected based on the renewed navigator echo for every image obtain the same. Thereby, a reference time for correcting object motion by making use of navigator echoes (3021, 3022) is set short and artifacts due to an object motion is reduced with an accuracy corresponding to a high temporal resolution. Thus, an MRI method which permits reduction of artifacts due to object motions while keeping a high temporal resolution for an MRI of animating images is provided.
29 Citations
14 Claims
- 1. A magnetic resonance imaging method in which after irradiating RF pulses of magnetic resonance frequencies into an object to be inspected, a step of running a sequence for detecting echo signals sequentially and a step of reconstructing an image by making use of the detected echo signals which are repeated in parallel, and subsequent images are obtained by successively renewing a part of the echo signals used for reconstructing the previous image, characterized in that, a navigator echo is generated for every irradiation of the RF pulses and is detected, wherein one generated navigator echo which serves as a reference for correcting phases of the echo signals used for the image reconstruction and is successively renewed for every image, and phases of the echo signals are corrected based on the renewed navigator echo for every image.
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3. A magnetic resonance imaging method comprising the steps of:
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irradiating a RF pulse of magnetic resonance frequencies toward a predetermined slicing surface of an object to be inspected, and then detecting an echo signal group sequentially produced in association with the irradiation of the RF pulse; reconstructing a piece of image of the predetermined slicing surface by making use of a plurality of echo signal groups which are acquired by repeating said echo signal group detecting step a plurality of times; further reconstructing a subsequent piece of image of the predetermined slicing surface by making use of a part of the plurality of echo signal groups which is used for the previous image reconstruction and an echo signal group which is acquired by performing subsequently said echo signal group detecting step at least one time; and repeating said further step of reconstructing a subsequent piece of image while renewing a part of the plurality of echo signal groups used for the image reconstruction, wherein the magnetic resonance imaging method further comprises the steps of; introducing in each of said echo signal group detecting steps at least one navigator echo for each of the echo signal groups; role-assigning one of the respective navigator echoes introduced for a plurality of echo signal groups which are used for reconstructing a piece of image as a reference navigator echo exclusively for the reconstruction of the piece of image and the remaining navigator echoes as monitor navigator echoes; determining phase differences between the reference navigator echo and the monitor navigator echoes which are assigned exclusively for the reconstruction of the piece of image and correcting the phases of echo signal groups to which the respective monitor navigator echoes belong based on the determined phase differences; and selecting for a successive image reconstruction a new reference navigator echo other than the navigator echo which is used as the reference navigator echo in the previous image reconstruction among respective navigator echoes for a plurality of echo signal groups which are used for the successive image reconstruction. - View Dependent Claims (4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. A magnetic resonance imaging device comprising:
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means for repeatedly irradiating RF pulses of magnetic resonance frequencies at a predetermined interval onto an object to be inspected and placed in a static magnetic field; means for applying gradient magnetic fields in the space of the static magnetic field surrounding the object to be inspected so as to acquire an echo signal group and at least one navigator echo from a predetermined region on a predetermined slicing surface of the object to be inspected in response the respective irradiation of the RF pulses from said RF pulse irradiation means; means for detecting the echo signal groups and the navigator echoes belonging to the respective echo signal groups which are produced in response to the application of the gradient magnetic fields from said gradient magnetic field application means; and means for reconstructing one piece of image of the predetermined slicing surface by making use the plurality of echo signal groups acquired in said echo detecting means, wherein said image reconstructing means reconstruct a subsequent one piece of image of the predetermined slicing surface by making use of a part of the plurality of echo signal groups which are used for reconstructing a previous one piece of image and at least one echo signal group newly acquired from said echo detecting means, during the respective image reconstructions, one of the navigator echoes belonging to one of the plurality of echo signal groups which are used for each of the image reconstructions is assigned as a reference navigator echo, phase differences between the assigned reference navigator echo and other remaining navigator echoes are determined, the phases of the plurality of echo signal groups which are used for the image reconstruction are corrected based on the determined respective phase differences, and the reference navigator echo which is used for the phase correction of the respective plurality of echo signal groups is renewed for every image reconstruction. - View Dependent Claims (14)
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Specification