Reduced scan time cardiac gated magnetic resonance cine and flow imaging

Claim 2

A cine magnetic resonance imaging method comprising: (a) monitoring cardiac cycles of a subject in a magnetic resonance imaging region; (b) in coordination with each monitored cardiac cycle, generating a series of groups of consecutive echo sequences and receiving a corresponding plurality of echo signals, each echo signal corresponding to one view of k-space, a positive portion of k-space being segmented into n segments, a negative portion of k-space being segmented into a corresponding n segments, all of the views of each group being from one of the positive k-space portion and the negative k-space portion; (c) repeating step (b) with each of the groups at substantially the same time in each of a plurality of the monitored cardiac cycles; (d) sorting the echo signals by group such that each group corresponds to a different time interval of each of the subject's cardiac cycles; (e) reconstructing a frame image representation from the echo signals of each group.

Claim 3

The method as set forth in claim 1 wherein the echo sequence generating step includes generating a motion sensitized echo sequence and a reference echo sequence and receiving a motion sensitized echo signal and a reference echo signal corresponding to each view of k-space; in the sorting step, the reference and motion sensitized echo signals corresponding to each frame are separated; in the reconstructing step, the motion sensitized and reference echo signals of each group are reconstructed into separate reference and motion sensitized frame images; and further including subtracting the reference and motion sensitized frame images corresponding to the same group to create a flow image, whereby a plurality of flow images each corresponding to one of the time intervals of the subject's cardiac cycle are generated.

Claim 4

The method as set forth in claim 2 wherein in each group, corresponding reference and motion sensitive views are collected back-to-back in the same group.

Claim 5

A cine magnetic resonance imaging method in which a positive portion of k-space is segmented into n segments and a negative portion of k-space is segmented into a corresponding n segments, the first segment of both positive and negative k-space containing views with highest order frequency components, subsequent segments containing views with progressively lower order frequency components, and nth positive and negative segments containing views with central-most, lowest order frequency components, the method comprising: (a) monitoring cardiac cycles of a subject in a magnetic resonance imaging region; (b) in coordination with each monitored cardiac cycle, generating a series of groups of consecutive echo sequences and receiving a corresponding plurality of echo signals, each echo signal corresponding to one view of k-space, all of the views in each group being from one of the positive k-space portion and the negative k-space portion, echo signals corresponding to views from the nth positive and negative segments of k-space are generated most central within each group and echo signals corresponding to views from the first and second segmentations of k-space are at the ends of each group, whereby the central views are collected in the middle of each time interval of the subject's cardiac cycle; (c) repeating step (b) with each of the groups at substantially the same time in each of a plurality of the monitored cardiac cycles; (d) sorting the echo signals by group such that each group corresponds to a different time interval of each of the subject's cardiac cycles; (e) reconstructing a frame image representation from the echo signals of each group.

Claim 6

A cine magnetic resonance imaging method in which a positive portion of k-space is segmented into n segments and a negative portion of k-space is segmented into a corresponding n segments, the first segment of both positive and negative k-space containing views with highest order frequency components, subsequent segments containing views with progressively lower order frequency components, and nth positive and negative segments containing views with central-most, lowest order frequency components, the method comprising: (a) monitoring cardiac cycles of a subject in a magnetic resonance imaging region; (b) in coordination with each monitored cardiac cycle, generating a series of groups of consecutive echo sequences and receiving a corresponding plurality of echo signals, each echo signal corresponding to one view of k-space, all of the views in each group being from one of the positive k-space portion and the negative k-space portion, echo signals corresponding to views from the nth positive and negative segments of k-space are generated most central within each group and echo signals corresponding to views from the first and second segmentations of k-space are at the ends of each group, whereby the central views are collected in the middle of each time interval of the subject's cardiac cycle; (c) repeating step (b) with each of the groups at substantially the same time in each of a plurality of the monitored cardiac cycles; (d) sorting the echo signals by group such that each group corresponds to a different time interval of each of the subject's cardiac cycles; (e) reconstructing a frame image representation from the echo signals of each group.

Claim 7

The method as set forth in claim 4 wherein the views in k-space are numbered sequentially and wherein in each group, all of the views are one of even and odd numbered views.

Claim 8

The method as set forth in claim 5 wherein the echo sequence generating step includes generating a motion sensitized echo sequence and a reference echo sequence and receiving a motion sensitized echo signal and a reference echo signal corresponding to each view of k-space; in the sorting step, the reference and motion sensitized echo signals corresponding to each frame are separated; in the reconstructing step, the motion sensitized and reference echo signals of each group are reconstructed into separate reference and motion sensitized frame images; and further including subtracting the reference and motion sensitized frame images corresponding to the same group to create a flow image, whereby a plurality of flow images each corresponding to one of the time intervals of the subject's cardiac cycle are generated.

Claim 9

The method as set forth in claim 6 wherein in each group, corresponding reference and motion sensitive views are collected back-to-back in the same group.

Claim 10

The method as set forth in claim 4 wherein the echo sequence generating step includes generating a motion sensitized echo sequence and a reference echo sequence and receiving a motion sensitized echo signal and a reference echo signal corresponding to each view of k-space; in the sorting step, the reference and motion sensitized echo signals corresponding to each frame are separated; in the reconstructing step, the motion sensitized and reference echo signals of each group are reconstructed into separate reference and motion sensitized frame images; and further including subtracting the reference and motion sensitized frame images corresponding to the same group to create a flow image, whereby a plurality of flow images each corresponding to one of the time intervals of the subject's cardiac cycle are generated.

Claim 11

The method as set forth in claim 8 wherein in each group, corresponding reference and motion sensitive views are collected back-to-back in the same group.

Claim 12

A cine magnetic resonance imaging method in which a positive portion of k-space is segmented into n segments and a negative portion of k-space is segmented into a corresponding n segments, the first segment of both positive and negative k-space containing views with highest order frequency components, subsequent segments containing views with progressively lower order frequency components, and nth positive and negative segments containing views with central-most, lowest order frequency components, the method comprising: (a) monitoring cardiac cycles of a subject in a magnetic resonance imaging region; (b) in coordination with each monitored cardiac cycle, generating a series of groups of consecutive echo sequences and receiving a corresponding plurality of echo signals, each echo signal corresponding to one view of k-space, the views in k-space being numbered sequentially, all of the views in each group being from one of the positive k-space portion and the negative k-space portion, all of the views are one of even and odd numbered views; (c) repeating step (b) with each of the groups at substantially the same time in each of a plurality of the monitored cardiac cycles; (d) sorting the echo signals by group such that each group corresponds to a different time interval of each of the subject's cardiac cycles; (e) reconstructing a frame image representation from the echo signals of each group.

Claim 13

A cine magnetic resonance imaging method in which a positive portion of k-space is segmented into n segments and a negative portion of k-space is segmented into a corresponding n segments, the first segment of both positive and negative k-space containing views with highest order frequency components, subsequent segments containing views with progressively lower order frequency components, and nth positive and negative segments containing views with central-most, lowest order frequency components, the method comprising: (a) monitoring cardiac cycles of a subject in a magnetic resonance imaging region; (b) in coordination with each monitored cardiac cycle, generating a series of groups of consecutive echo sequences and receiving a corresponding plurality of echo signals, each echo signal corresponding to one view of k-space, the views in k-space being numbered sequentially, all of the views in each group being from one of the positive k-space portion and the negative k-space portion, all of the views are one of even and odd numbered views; (c) repeating step (b) with each of the groups at substantially the same time in each of a plurality of the monitored cardiac cycles; (d) sorting the echo signals by group such that each group corresponds to a different time interval of each of the subject's cardiac cycles; (e) reconstructing a frame image representation from the echo signals of each group.

Claim 14

A cine magnetic resonance imaging method in which a positive portion of k-space is segmented into n segments, and a negative portion of k-space is segmented into a corresponding n segments, the first segment of both positive and negative k-space containing views with highest order frequency components, subsequent segments containing views with progressively lower order frequency components, and the nth positive and negative segments containing views with central-most, lowest order frequency components, the method comprising: (a) monitoring cardiac cycles of a subject in a magnetic resonance imaging region; (b) in coordination with each monitored cardiac cycle, generating a series of groups of consecutive echo sequences and receiving a corresponding plurality of groups of magnetic resonance echo signals, each echo signals corresponding to one view of k-space, the echo signals corresponding to views of the nth positive and negative segments of k-space being generated at a common, central position of each group; (c) repeating step (b) with each of the groups at substantially the same time in each of a plurality of the monitored cardiac cycles; (d) sorting the echo signals by group such that each group corresponds to a different time interval of each of the subject's cardiac cycles; (e) reconstructing a frame image representation from the echo signals of each group.

Claim 15

A cine magnetic resonance imaging method in which a positive portion of k-space is segmented into n segments, and a negative portion of k-space is segmented into a corresponding n segments, the first segment of both positive and negative k-space containing views with highest order frequency components, subsequent segments containing views with progressively lower order frequency components, and the nth positive and negative segments containing views with central-most, lowest order frequency components, the method comprising: (a) monitoring cardiac cycles of a subject in a magnetic resonance imaging region; (b) in coordination with each monitored cardiac cycle, generating a series of groups of consecutive echo sequences and receiving a corresponding plurality of groups of magnetic resonance echo signals, each echo signals corresponding to one view of k-space, the echo signals corresponding to views of the nth positive and negative segments of k-space being generated at a common, central position of each group; (c) repeating step (b) with each of the groups at substantially the same time in each of a plurality of the monitored cardiac cycles; (d) sorting the echo signals by group such that each group corresponds to a different time interval of each of the subject's cardiac cycles; (e) reconstructing a frame image representation from the echo signals of each group.

Claim 16

The method as set forth in claim 11 wherein the views in k-space are numbered sequentially and wherein in each group, all of the views are one of even and odd numbered views.

Claim 17

The method as set forth in claim 11 wherein the echo sequence generating step includes generating a motion sensitized echo sequence and a reference echo sequence and receiving a motion sensitized echo signal and a reference echo signal corresponding to each view of k-space; in the sorting step, the reference and motion sensitized echo signals corresponding to each frame are separated; in the reconstructing step, the motion sensitized and reference echo signals of each group are reconstructed into separate reference and motion sensitized frame images; and further including subtracting the reference and motion sensitized frame images corresponding to the same group to create a flow image, whereby a plurality of flow images each corresponding to one of the time intervals of the subject's cardiac cycle are generated.

Claim 18

A cine magnetic resonance imaging method comprising: (a) monitoring cardiac cycles of a subject in a magnetic resonance imaging region; (b) in coordination with each monitored cardiac cycle, generating a series of groups of consecutive echo sequences and receiving a corresponding plurality of groups of magnetic resonance echo signals, each echo signal corresponding to one view of k-space in each group, a positive portion of k-space being segmented into n segments, a negative portion of k-space being segmented into a corresponding n segments, the first segment of both positive and negative k-space containing views with highest order frequency components, subsequent segments containing views with progressively lower order frequency components, and the nth positive and negative segments containing views with central-most, lowest order frequency components, adjacent pairs of echo sequences generate a motion sensitized echo signal and a reference echo signal corresponding to the same view; (c) repeating step (b) with each of the groups at substantially the same time in each of a plurality of the monitored cardiac cycles; (d) sorting the echo signals by group and by motion sensitized and reference signals within each group; (e) reconstructing a motion sensitized frame image and a reference frame image from the echo signals of each group; (f) subtracting the reference and motion sensitized frame images corresponding to the same group to create a flow image, whereby a plurality of flow images each corresponding to a plurality of different times within the subject's cardiac cycle are produced.

Claim 19

A cine magnetic resonance imaging method comprising: (a) monitoring cardiac cycles of a subject in a magnetic resonance imaging region; (b) in coordination with each monitored cardiac cycle, generating a series of groups of consecutive echo sequences and receiving a corresponding plurality of groups of magnetic resonance echo signals, each echo signal corresponding to one view of k-space in each group, a positive portion of k-space being segmented into n segments, a negative portion of k-space being segmented into a corresponding n segments, the first segment of both positive and negative k-space containing views with highest order frequency components, subsequent segments containing views with progressively lower order frequency components, and the nth positive and negative segments containing views with central-most, lowest order frequency components, adjacent pairs of echo sequences generate a motion sensitized echo signal and a reference echo signal corresponding to the same view; (c) repeating step (b) with each of the groups at substantially the same time in each of a plurality of the monitored cardiac cycles; (d) sorting the echo signals by group and by motion sensitized and reference signals within each group; (e) reconstructing a motion sensitized frame image and a reference frame image from the echo signals of each group; (f) subtracting the reference and motion sensitized frame images corresponding to the same group to create a flow image, whereby a plurality of flow images each corresponding to a plurality of different times within the subject's cardiac cycle are produced.

Claim 20

A cine magnetic resonance imaging method in which a positive portion of k-space is segmented into n segments, a negative portion of k-space is segmented into a corresponding n segments, the first segment of both positive and negative k-space containing views with highest order frequency components, subsequent segments containing views with progressively lower order frequency components, and the nth positive and negative segments containing views with central-most, lowest order frequency components, the method comprising: (a) monitoring cardiac cycles of a subject in a magnetic resonance imaging region; (b) in coordination with each monitored cardiac cycle, generating a series of groups of consecutive echo sequences and receiving a corresponding plurality of groups of magnetic resonance echo signals, each echo signal corresponding to one view of k-space in each group, adjacent pairs of echo sequences generate a motion sensitized echo signal and a reference echo signal corresponding to the same view in each group, echo signals corresponding to views from the nth positive and negative segments of k-space are generated most central within each group and echo signals corresponding to views from the first and second segmentations of k-space are at the ends of each group, whereby the central views are collected in the middle of each time interval of the subject's cardiac cycle; (c) repeating step (b) with each of the groups at substantially the same time in each of a plurality of the monitored cardiac cycles; (d) sorting the echo signals by group and by motion sensitized and reference signals within each group; (e) reconstructing a motion sensitized frame image and a reference frame image from the echo signals of each group; (f) subtracting the reference and motion sensitized frame images corresponding to the same group to create a flow image, whereby a plurality of flow images each corresponding to one of the subject's cardiac cycle time intervals are produced.

Claim 21

A cine magnetic resonance imaging method in which a positive portion of k-space is segmented into n segments, a negative portion of k-space is segmented into a corresponding n segments, the first segment of both positive and negative k-space containing views with highest order frequency components, subsequent segments containing views with progressively lower order frequency components, and the nth positive and negative segments containing views with central-most, lowest order frequency components, the method comprising: (a) monitoring cardiac cycles of a subject in a magnetic resonance imaging region; (b) in coordination with each monitored cardiac cycle, generating a series of groups of consecutive echo sequences and receiving a corresponding plurality of groups of magnetic resonance echo signals, each echo signal corresponding to one view of k-space in each group, adjacent pairs of echo sequences generate a motion sensitized echo signal and a reference echo signal corresponding to the same view in each group, echo signals corresponding to views from the nth positive and negative segments of k-space are generated most central within each group and echo signals corresponding to views from the first and second segmentations of k-space are at the ends of each group, whereby the central views are collected in the middle of each time interval of the subject's cardiac cycle; (c) repeating step (b) with each of the groups at substantially the same time in each of a plurality of the monitored cardiac cycles; (d) sorting the echo signals by group and by motion sensitized and reference signals within each group; (e) reconstructing a motion sensitized frame image and a reference frame image from the echo signals of each group; (f) subtracting the reference and motion sensitized frame images corresponding to the same group to create a flow image, whereby a plurality of flow images each corresponding to one of the subject's cardiac cycle time intervals are produced.

Claim 22

A cine magnetic resonance imaging method in which a positive portion of k-space is segmented into n segments and a negative portion of k-space is segmented into a corresponding n segments, the method comprising: (a) monitoring cardiac cycles of a subject in a magnetic resonance imaging region; (b) in coordination with each monitored cardiac cycle, generating a series of groups of consecutive echo sequences and receiving a corresponding plurality of groups of magnetic resonance echo signals, each echo signal corresponding to one view of k-space in each group, the views in k-space being numbered sequentially, adjacent pairs of echo sequences generate a motion sensitized echo signal and a reference echo signal corresponding to the same view in each group, all of the views being one of even and odd numbered views; (c) repeating step (b) with each of the groups at substantially the same time in each of a plurality of the monitored cardiac cycles; (d) sorting the echo signals by group and by motion sensitized and reference signals within each group; (e) reconstructing a motion sensitized frame image and a reference frame image from the echo signals of each group; (f) subtracting the reference and motion sensitized frame images corresponding to the same group to create a flow image.

Claim 23

A cine magnetic resonance imaging method in which a positive portion of k-space is segmented into n segments and a negative portion of k-space is segmented into a corresponding n segments, the method comprising: (a) monitoring cardiac cycles of a subject in a magnetic resonance imaging region; (b) in coordination with each monitored cardiac cycle, generating a series of groups of consecutive echo sequences and receiving a corresponding plurality of groups of magnetic resonance echo signals, each echo signal corresponding to one view of k-space in each group, the views in k-space being numbered sequentially, adjacent pairs of echo sequences generate a motion sensitized echo signal and a reference echo signal corresponding to the same view in each group, all of the views being one of even and odd numbered views; (c) repeating step (b) with each of the groups at substantially the same time in each of a plurality of the monitored cardiac cycles; (d) sorting the echo signals by group and by motion sensitized and reference signals within each group; (e) reconstructing a motion sensitized frame image and a reference frame image from the echo signals of each group; (f) subtracting the reference and motion sensitized frame images corresponding to the same group to create a flow image.

Claim 24

A cine magnetic resonance imaging method comprising: (a) monitoring cardiac cycles of a subject in a magnetic imaging region; (b) in coordination with each monitored cardiac cycle, generating a series of groups of consecutive echo sequences and receiving a corresponding plurality of groups of magnetic resonance echo signals, the echo sequences generating motion sensitized echo signals and reference echo signals corresponding to each of a plurality of differently phase encoded views; (c) repeating step (b) with each of the groups at substantially the same time in each of a plurality of the monitored cardiac cycles; (d) sorting the echo signals by group and by motion sensitized and reference signals within each group; (e) reconstructing a motion sensitized frame image and a reference frame image from the echo signals of each group; (f) subtracting the reference and motion sensitized frame images corresponding to the same group to create a flow image, whereby a plurality of flow images corresponding to a plurality of different times within the subject's cardiac cycle are produced.

Claim 25

A cine magnetic resonance imaging method comprising: (a) monitoring cardiac cycles of a subject in a magnetic imaging region; (b) in coordination with each monitored cardiac cycle, generating a series of groups of consecutive echo sequences and receiving a corresponding plurality of groups of magnetic resonance echo signals, the echo sequences generating motion sensitized echo signals and reference echo signals corresponding to each of a plurality of differently phase encoded views; (c) repeating step (b) with each of the groups at substantially the same time in each of a plurality of the monitored cardiac cycles; (d) sorting the echo signals by group and by motion sensitized and reference signals within each group; (e) reconstructing a motion sensitized frame image and a reference frame image from the echo signals of each group; (f) subtracting the reference and motion sensitized frame images corresponding to the same group to create a flow image, whereby a plurality of flow images corresponding to a plurality of different times within the subject's cardiac cycle are produced.

Claim 26

A cine magnetic resonance imaging apparatus comprising: (a) a cardiac monitoring means for monitoring cardiac cycles of a subject in a magnetic resonance imaging region; (b) a magnetic resonance echo signal generating means for generating a series of groups of consecutive echo generating magnetic resonance sequences and receiving a corresponding plurality of groups of magnetic resonance echo signals, in coordination with each of a plurality of monitored cardiac cycles, each echo signal corresponding to one view of k-space, a positive portion of k-space being segmented into n segments and a negative portion of k-space being segmented into a corresponding n segments, the first segment of both positive and negative k-space containing views with highest order frequency components, subsequent segments containing views with progressively lower order frequency components, and the nth positive and negative segments containing views with central-most, lowest order frequency components, all of the views of each group being from one of the positive k-space portion and the negative k-space portion, each of the groups of echo signals are received at substantially the same time in each of the plurality of the monitored cardiac cycles; (c) a sorting means for sorting the echo signals by group such that each group corresponds to a different time interval of the subject's cardiac cycle; (d) an image reconstruction means for reconstructing a frame image representation from the echo signals of each group.

Claim 27

A cine magnetic resonance imaging apparatus comprising: (a) a cardiac monitoring means for monitoring cardiac cycles of a subject in a magnetic resonance imaging region; (b) a magnetic resonance echo signal generating means for generating a series of groups of consecutive echo generating magnetic resonance sequences and receiving a corresponding plurality of groups of magnetic resonance echo signals, in coordination with each of a plurality of monitored cardiac cycles, each echo signal corresponding to one view of k-space, a positive portion of k-space being segmented into n segments and a negative portion of k-space being segmented into a corresponding n segments, the first segment of both positive and negative k-space containing views with highest order frequency components, subsequent segments containing views with progressively lower order frequency components, and the nth positive and negative segments containing views with central-most, lowest order frequency components, all of the views of each group being from one of the positive k-space portion and the negative k-space portion, each of the groups of echo signals are received at substantially the same time in each of the plurality of the monitored cardiac cycles; (c) a sorting means for sorting the echo signals by group such that each group corresponds to a different time interval of the subject's cardiac cycle; (d) an image reconstruction means for reconstructing a frame image representation from the echo signals of each group.

Claim 28

A cine magnetic resonance imaging apparatus in which a positive portion of k-space is segmented into n segments, and a negative portion of k-space is segmented into a corresponding n segments, the first segment of both positive and negative k-space containing views with highest order frequency components, subsequent segments containing views with progressively lower order frequency components, and the nth positive and negative segments containing views with central-most, lowest order frequency components, the apparatus comprising: (a) a cardiac monitoring means for monitoring cardiac cycles of a subject in a magnetic resonance imaging region; (b) a magnetic resonance echo signal generating means for generating a series of groups of consecutive echo generating sequences and receiving a corresponding plurality of groups of magnetic resonance echo signals, each echo signal corresponding to one view of k-space, the echo signals corresponding to views of the nth segments of k-space being generated at a common, central position of each group, such that each of the groups of echo signals are received at substantially the same time in each of a plurality of the monitored cardiac cycles; (c) a sorting means for sorting the echo signals by group such that each group corresponds to a different time interval of the subject's cardiac cycle; (d) an image reconstruction means for reconstructing a frame image representation from the echo signals of each group.

Claim 29

A cine magnetic resonance imaging apparatus in which a positive portion of k-space is segmented into n segments, and a negative portion of k-space is segmented into a corresponding n segments, the first segment of both positive and negative k-space containing views with highest order frequency components, subsequent segments containing views with progressively lower order frequency components, and the nth positive and negative segments containing views with central-most, lowest order frequency components, the apparatus comprising: (a) a cardiac monitoring means for monitoring cardiac cycles of a subject in a magnetic resonance imaging region; (b) a magnetic resonance echo signal generating means for generating a series of groups of consecutive echo generating sequences and receiving a corresponding plurality of groups of magnetic resonance echo signals, each echo signal corresponding to one view of k-space, the echo signals corresponding to views of the nth segments of k-space being generated at a common, central position of each group, such that each of the groups of echo signals are received at substantially the same time in each of a plurality of the monitored cardiac cycles; (c) a sorting means for sorting the echo signals by group such that each group corresponds to a different time interval of the subject's cardiac cycle; (d) an image reconstruction means for reconstructing a frame image representation from the echo signals of each group.

Claim 30

A cine magnetic resonance imaging apparatus comprising: (a) a cardiac monitoring means for monitoring cardiac cycles of a subject in a magnetic resonance imaging region; (b) a means for generating a series of groups of consecutive echo generating sequences and receiving a corresponding plurality of groups of magnetic resonance echo signals in coordination with each monitored cardiac cycle, each echo signal corresponding to a one view of k-space such that in each group, adjacent pairs of echo sequences generate a motion sensitized echo signal and a reference echo signal corresponding to the same view, each of the groups being generated at substantially the same time in each of a plurality of the monitored cardiac cycles; (c) a means for sorting the echo signals by group and by motion sensitized and reference signals within each group; (d) a means for reconstructing a motion sensitized frame image and a reference frame image from the echo signals of each group; (e) a means for subtracting the reference and motion sensitized frame images corresponding to the same group to create a flow image.

Claim 31

A cine magnetic resonance imaging apparatus comprising: (a) a cardiac monitoring means for monitoring cardiac cycles of a subject in a magnetic resonance imaging region; (b) a means for generating a series of groups of consecutive echo generating sequences and receiving a corresponding plurality of groups of magnetic resonance echo signals in coordination with each monitored cardiac cycle, each echo signal corresponding to a one view of k-space such that in each group, adjacent pairs of echo sequences generate a motion sensitized echo signal and a reference echo signal corresponding to the same view, each of the groups being generated at substantially the same time in each of a plurality of the monitored cardiac cycles; (c) a means for sorting the echo signals by group and by motion sensitized and reference signals within each group; (d) a means for reconstructing a motion sensitized frame image and a reference frame image from the echo signals of each group; (e) a means for subtracting the reference and motion sensitized frame images corresponding to the same group to create a flow image.