US5361028A — Method and apparatus for high speed magnetic reso…

Claim 1

Independent Claim 235 words

A method of magnetic resonance imaging, comprising the steps of: (a) placing an object to be examined in a static magnetic field; (b) carrying out a pulse sequence, including: (b1) applying RF pulses and a slicing gradient magnetic field for exciting a desired imaging region in the object to be examined; (b2) applying a reading gradient magnetic field which regularly fluctuates between a negative value and a positive value onto the object to be examined; (b3) applying an initial phase encoding gradient magnetic field for specifying a partial region in a k-space onto the object to be examined before the reading gradient magnetic field is applied in step (b2); (b4) applying a predetermined pulse shaped phase encoding gradient magnetic field onto the object to be examined, every time the reading gradient magnetic field changes polarity; (b5) collecting echo signals for the partial region in the k-space emitted from the desired imaging region, every time the reading gradient magnetic field changes polarity; (c) repeating the pulse sequence of step (b) a plurality of times while sequentially changing a setting of the initial phase encoding gradient magnetic field applied in step (b3), such that the echo signals are collected for an entire region of the k-space; and (d) reconstructing MR images from the echo signals for the entire region of the k-space collected in step (b5) by a repeated application of the pulse sequence of step (b).

Claim 2

Independent Claim 235 words

A method of magnetic resonance imaging, comprising the steps of: (a) placing an object to be examined in a static magnetic field; (b) carrying out a pulse sequence, including: (b1) applying RF pulses and a slicing gradient magnetic field for exciting a desired imaging region in the object to be examined; (b2) applying a reading gradient magnetic field which regularly fluctuates between a negative value and a positive value onto the object to be examined; (b3) applying an initial phase encoding gradient magnetic field for specifying a partial region in a k-space onto the object to be examined before the reading gradient magnetic field is applied in step (b2); (b4) applying a predetermined pulse shaped phase encoding gradient magnetic field onto the object to be examined, every time the reading gradient magnetic field changes polarity; (b5) collecting echo signals for the partial region in the k-space emitted from the desired imaging region, every time the reading gradient magnetic field changes polarity; (c) repeating the pulse sequence of step (b) a plurality of times while sequentially changing a setting of the initial phase encoding gradient magnetic field applied in step (b3), such that the echo signals are collected for an entire region of the k-space; and (d) reconstructing MR images from the echo signals for the entire region of the k-space collected in step (b5) by a repeated application of the pulse sequence of step (b).

Claim 3

Dependent Claim 109 words

The method of claim 1 wherein the step (b1) of the pulse sequence of the step (b) further includes: (b1-1) applying 90° RF pulse and the slicing gradient magnetic field for exciting the desired imaging region in the body to be examined; and (b1-2) applying 180° RF pulse and the slicing gradient magnetic field for producing echoes; and wherein the pulse sequence at the step (b) further includes the step of repeating the steps (b1-2) and (b2) to (b5) for a plurality of times, with the setting of the initial phase encoding gradient magnetic field applied at the step (b3) being different in each repetition of the step (b3).

Claim 4

Dependent Claim 71 words

The method of claim 1, wherein the pulse sequence at the step (b) further includes: (b6) applying rewinding phase encoding gradient magnetic field for making an integrated value of the phase encoding gradient magnetic field applied to the body to be examined to be a predetermined constant value, after the echo signals are collected at the step (b5), before the pulse sequence of the step (b) is repeated for next time.

Claim 5

Dependent Claim 107 words

The method of claim 1, wherein the pulse sequence at the step (b) further includes: (b7) applying off-set reading gradient magnetic field for dividing the partial region in the k-space into a plurality of parts along a reading gradient magnetic field direction of the k-space, to the body to be examined before the reading gradient magnetic field is applied at the step (b3); and (b8) applying off-set cancelling gradient magnetic field for cancelling the off-set reading gradient magnetic field applied at the step (b7), after the echo signals are collected at the step (b5), before the pulse sequence of the step (b) is repeated for next time.

Claim 6

Dependent Claim 100 words

The method of claim 1, wherein the pulse sequence at the step (b) further includes: (b9) applying off-set slice phase encoding gradient magnetic field for off-setting the k-space in a slicing gradient magnetic field direction, to the body to be examined before the reading gradient magnetic field is applied at the step (b3); and (b10) applying phase off-set rewinding gradient magnetic field for cancelling the off-set slice phase encoding gradient magnetic field applied at the step (b9), after the echo signals are collected at the step (b5), before the pulse sequence of the step (b) is repeated for next time.

Claim 7

Dependent Claim 27 words

The method of claim 1, wherein at the step (b1), the RE pulses are applied according to one of CPMG (Carr-Purcell-Meiboom-Gill) scheme and modified CP (Cart-Purcell) scheme.

Claim 8

Dependent Claim 30 words

The method of claim 1, wherein at the step (b1), the RF pulses applied are for flipping target nuclear spins in the desired imaging region by a predetermined flip angle.

Claim 9

Dependent Claim 50 words

The method of claim 7, wherein the pulse sequence at the step (b) further includes: (b11) applying a cancelling RF pulses for flipping the target nuclear spins in the desired imaging region by a negative of the predetermined flip angle, after the echo signals are collected at the step (b5).

Claim 10

Dependent Claim 70 words

The method of claim 1, wherein the pulse sequence at the step (b) further includes: (b12) applying one of a pre-pulse sequence for enhancing a contrast for a longitudinal relaxation time of target nuclear spins in the desired imaging region, a prepulse sequence for enhancing a contrast for a transverse relaxation time of target nuclear spins in the desired imaging region, and a pre-pulse sequence for suppressing chemical shift artifacts.

Claim 11

Dependent Claim 35 words

The method of claim 1, wherein at the step (d), the echo signals are rearranged according to a data acquisition pattern determined by the initial phase encoding gradient magnetic field applied at the step (b3).

Claim 12

Dependent Claim 63 words

The method of claim 10, wherein at the step (b5), the echo signals are collected according to the data acquisition pattern in which the echo signals for which one of a longitudinal relaxation time and a transverse relaxation time of target nuclear spins in the desired imaging region has a predetermined length are collected in a vicinity of an origin of the k-space.

Claim 13

Dependent Claim 48 words

The method of claim 10, wherein at the step (b5), the echo signals are collected according to the data acquisition pattern in which the echo signals which are least influenced by inhomogeneity of the static magnetic field are collected in a vicinity of an origin of the k-space.

Claim 14

Dependent Claim 66 words

The method of claim 1, wherein at the step (d), at least one of data order, amplitudes and phases of the echo signals collected at the step (b5) is corrected according to a peak position and an amplitude at the peak position of the echo signals obtained without using the initial and pulse shaped phase encoding gradient magnetic fields, before the MR images are reconstructed .

Claim 15

Dependent Claim 30 words

The method of claim 1, wherein at the step (d), the MR images reconstructed are corrected according to an inhomogeneity of the static magnetic field in the desired imaging region.

Claim 16

Independent Claim 278 words

An apparatus for magnetic resonance imaging, comprising: means for producing a static magnetic field in which a body to be examined is to be place; pulse sequence execution means for carrying out a pulse sequence, including: first means for applying RF pulses and a slicing gradient magnetic field for exciting a desired imaging region in the body to be examined; second means for applying a reading gradient magnetic field which regularly fluctuates between a negative value and a positive value onto the body to be examined; third means for applying initial phase encoding gradient magnetic field for specifying a partial region in a k-space, onto the body to be examined before the reading gradient magnetic field is applied by the second means, and applying a predetermined pulse shaped phase encoding gradient magnetic field onto the body to be examined, every time the reading gradient magnetic field changes polarity; data acquisition means for collecting echo signals for the partial region in the k-space emitted from the desired imaging region, every time the reading gradient magnetic field changes polarity; control means for controlling the pulse sequence execution means to repeat the pulse sequence by the first, second, and third means and the data acquisition means a plurality of times, while sequentially changing a setting of the initial phase encoding gradient magnetic field applied by the third means, such that the echo signals are collected for an entire region of the k-space; and image reconstruction means for reconstructing MR images from the echo signals for the entire region of the k-space collected by the data acquisition means by a repeated application of the pulse sequence by the pulse sequence execution means.

Claim 17

Independent Claim 278 words

An apparatus for magnetic resonance imaging, comprising: means for producing a static magnetic field in which a body to be examined is to be place; pulse sequence execution means for carrying out a pulse sequence, including: first means for applying RF pulses and a slicing gradient magnetic field for exciting a desired imaging region in the body to be examined; second means for applying a reading gradient magnetic field which regularly fluctuates between a negative value and a positive value onto the body to be examined; third means for applying initial phase encoding gradient magnetic field for specifying a partial region in a k-space, onto the body to be examined before the reading gradient magnetic field is applied by the second means, and applying a predetermined pulse shaped phase encoding gradient magnetic field onto the body to be examined, every time the reading gradient magnetic field changes polarity; data acquisition means for collecting echo signals for the partial region in the k-space emitted from the desired imaging region, every time the reading gradient magnetic field changes polarity; control means for controlling the pulse sequence execution means to repeat the pulse sequence by the first, second, and third means and the data acquisition means a plurality of times, while sequentially changing a setting of the initial phase encoding gradient magnetic field applied by the third means, such that the echo signals are collected for an entire region of the k-space; and image reconstruction means for reconstructing MR images from the echo signals for the entire region of the k-space collected by the data acquisition means by a repeated application of the pulse sequence by the pulse sequence execution means.

Claim 18

Dependent Claim 106 words

The apparatus of claim 15, wherein the first means applies: 90° RF pulse and the slicing gradient magnetic field for exciting the desired imaging region in the body to be examined; and 180° RF pulse and the slicing gradient magnetic field for producing echoes; and wherein the pulse sequence execution means repeats the application of the 180° RF pulse and the slicing gradient magnetic field by the first means and subsequent operations of the second, third, and data aquisition means, for a plurality off times, with the setting of the initial phase encoding gradient magnetic field applied by the third means being different in each repetition.

Claim 19

Dependent Claim 73 words

The apparatus of claim 15, wherein the pulse sequence execution means further includes: means for applying rewinding phase encoding gradient magnetic field for making an integrated value of the phase encoding gradient magnetic field applied to the body to be examined to be a predetermined constant value, after the echo signals are collected by the data acquisition means, before the pulse sequence by the pulse sequence execution means is repeated for next time.

Claim 20

Dependent Claim 111 words

The apparatus of claim 15, wherein the pulse sequence execution means further includes: off-set means for applying off-set reading gradient magnetic field for dividing the partial region in the k-space into a plurality of parts along a reading gradient magnetic field direction of the k-space, to the body to be examined before the reading gradient magnetic field is applied by the second means; and means for applying off-set cancelling gradient magnetic field for cancelling the off-set reading gradient magnetic field applied by the off-set means, after the echo signals are collected by the data acquisition means, before the pulse sequence by the pulse sequence execution means is repeated for next time.

Claim 21

Dependent Claim 104 words

The apparatus of claim 15, wherein the pulse sequence execution means further includes: off-set means for applying off-set slice phase encoding gradient magnetic field for off-setting the k-space in a slicing gradient magnetic field direction, to the body to be examined before the reading gradient magnetic field is applied by the second means; and means for applying phase off-set rewinding gradient magnetic field for cancelling the off-set slice phase encoding gradient magnetic field applied by the off-set means, after the echo signals are collected by the data acquisition means, before the pulse sequence by the pulse sequence execution means is repeated for next time.

Claim 22

Independent Claim 25 words

The apparatus of claim 1S, wherein the first means applies the RF pulses according to one of CPMG (Carr-Purcell-Meiboom-Gill) scheme and modified CP (Cart-Purcell) scheme.

Claim 23

Dependent Claim 27 words

The apparatus of claim 15, wherein the first means applies the RF pulses for flipping target nuclear spins the desired imaging region by a predetermined Flip angle.

Claim 24

Dependent Claim 50 words

The apparatus of claim 21, wherein the pulse sequence execution means further includes: means for applying a cancelling RF pulses for flipping the target nuclear spins in the desired imaging region by a negative of the predetermined flip angle, after the echo signals are collected by the data acquisition means.

Claim 25

Dependent Claim 69 words

The apparatus of claim 15, wherein the pulse sequence execution means further includes: means for applying one of a pre-pulse sequence for enhancing a contrast for a longitudinal relaxation time of target nuclear spins in the desired imaging region, a pre-pulse sequence for enhancing a contrast for a transverse relaxation time of target nuclear spins in the desired imaging region, and a pre-pulse sequence for suppressing chemical shift artifacts.

Claim 26

Dependent Claim 34 words

The apparatus of claim 15, wherein the image reconstruction means rearranges the echo signals according to a data acquisition pattern determined by the initial phase encoding gradient magnetic field applied by the third means.

Claim 27

Dependent Claim 62 words

The apparatus of claim 24, wherein the data acquisition means collects the echo signals according to the data acquisition pattern in which the echo signals for which one of a longitudinal relaxation time and a transverse relaxation time of target nuclear spins in the desired imaging region has a predetermined length are collected in a vicinity of an origin of the k-space.

Claim 28

Dependent Claim 47 words

The apparatus of claim 24, wherein the data acquisition means collects the echo signals according to the data acquisition pattern in which the echo signals which are least influenced by inhomogeneity of the static magnetic field are collected in a vicinity of an origin of the k-space.

Claim 29

Dependent Claim 65 words

The apparatus of claim 15, wherein the image reconstruction means corrects at least one of data order, amplitudes and phases of the echo signals collected by the data acquisition means according to a peak position and an amplitude at the peak position of the echo signals obtained without using the initial and pulse shaped phase encoding gradient magnetic fields, before the MR images are reconstructed.

Claim 30

Dependent Claim 29 words

The apparatus of claim 15, wherein the image reconstruction means corrects the MR images reconstructed according to an inhomogeneity of the static magnetic field in the desired imaging region.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	1997-10-31	1998-05-02	1998-11-01	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	2001-10-31	2002-05-02	2002-11-01	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	2005-10-31	2006-05-02	2006-11-01	$7700.00	Window Closed / Lapsed

Method and apparatus for high speed magnetic resonance imaging with improved image quality

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