JP2002136499A - Magnetic resonance imaging unit and magnetic resonance imaging method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To drastically relieve burden and time by shortening a time required from the positioning of image pickup slices to image conversion in an interactive image pickup method. SOLUTION: A magnetic resonance imaging unit for performing the interactive image pickup method is provided with a means for impressing a pulse sequence consisting of a plurality of pulse strings to individually scan the slices with different image pickup parameters concerning the display state of MR images on an image pickup object and for collecting the MR signals and with a means for generating the MR images from the MR signals. For example, the pulse strings comprise the pulse strings A1 and A2 where high-speed scanning property is regarded as the important one and the pulse strings B1 and B2 where image quality is regarded as the important one. The display state of the MR images is contrast and/or resolution. The image pickup parameters are the repetition time of the pulse strings and/or the flip angle of a high frequency pulse.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic resonance (MR) imaging (MRI) apparatus and a magnetic resonance imaging method for imaging the inside of an object to be imaged on the basis of a magnetic resonance phenomenon.
An imaging method in which an image of a slice can be displayed almost in real time while continuously changing an imaging slice (cross section), whereby a desired imaging slice can be determined on the spot or a captured image can be dynamically observed. And a magnetic resonance imaging method.

[0002]

2. Description of the Related Art At present, magnetic resonance imaging is already widely used as one of the imaging methods in the medical field. In this magnetic resonance imaging, a nuclear spin of an imaging target placed in a static magnetic field is magnetically excited by a high frequency signal of the Larmor frequency, and an image inside the imaging target is reconstructed from an MR signal generated by this excitation. This is an imaging method.

[0003] There are various types of magnetic resonance imaging, and the types are divided depending on the pulse sequence used for magnetic excitation and signal acquisition.

[0004] As one of the magnetic resonance imaging methods, in recent years, by repeatedly exciting magnetization in the same slice to be imaged, image data of the slice is continuously collected and a change in the image of the slice is performed. An imaging method called fluoroscopy is used in which a subject portion passing through a slice set at the same position as viewed from the apparatus side is continuously visualized by observing an image or moving a bed.

Further, as an imaging method in which the fluoroscopy is improved, a method called an interactive imaging method (or an interactive MRI) has been proposed. This technique does not limit the imaging slice to the same plane as in fluoroscopy, and allows the imaging slice to be continuously set and changed at an arbitrary position and / or direction while performing MR imaging. A desired imaging slice inside is set and visualized in a short time.

[0006]

However, in the conventional interactive imaging method, FE (F
field Echo) type or FISP (Fast)
Imaging with Steady Prece
session) type pulse sequence is used, and image data is collected in a short time. Therefore, it is useful for grasping the outline of the morphology of the imaging target, but contrast is necessary for observing the detailed structure inside the imaging target. And the signal-to-noise ratio (SNR) is insufficient.

Therefore, in the case of the conventional interactive imaging method, after determining an imaging slice from a schematic morphological image obtained by this imaging method, a pulse sequence for acquiring a high-contrast image is activated, and a still image of the slice is obtained. I was observing.

For this reason, not only positioning of a desired imaging slice is performed, but also an imaging time until obtaining an image of the desired imaging slice is lengthened, and since a high-contrast pulse sequence is started, operation is troublesome. Increase. As a result, there is an unsolved problem that the total diagnosis time is lengthened, the patient throughput is reduced, and the operational burden is large.

SUMMARY OF THE INVENTION The present invention has been made to overcome the current situation faced by the prior art, and when performing an interactive imaging method, from positioning of an imaging slice to imaging as compared with conventional imaging. It is an object of the present invention to shorten the time required for the operation and to significantly reduce the labor, thereby improving the efficiency of diagnosis and reducing the burden on operation.

[0010]

In order to achieve the above object, a magnetic resonance imaging apparatus according to the present invention is configured to continuously obtain an MR image of an object to be imaged based on an interactive imaging method. Signal acquisition means for applying a pulse sequence consisting of a plurality of pulse trains for individually scanning slices to the imaging target to collect MR signals, and image generation means for generating the MR images from the MR signals It is characterized by the following.

According to a preferred example, the plurality of pulse trains include a pulse train emphasizing high-speed scanning based on the interactive imaging method and a pulse train emphasizing image quality of the MR image.

Thus, the contrast of the image of at least one of the two or more slices at or near the same position of the object to be imaged is different from that of the other slices. Therefore, similar to the conventional interactive imaging method, while image data can be continuously collected in a short time, high-contrast images can be continuously obtained almost simultaneously. As a result, a desired imaging slice can be set quickly in a short time, and there is no need to separately activate a high-contrast pulse sequence as in the related art, so that the imaging time is reduced as a whole and the operational burden is reduced. it can.

For example, the imaging parameter is at least one of a repetition time of the plurality of pulse trains and a flip angle of a high-frequency pulse included in the pulse train.
Thus, changing the repetition time and / or flip angle can change the contrast and resolution of the image.

Further, for example, the imaging parameter is the kind of the plurality of pulse trains.

According to still another preferred embodiment, there is provided a slice setting means capable of setting a plurality of slices to which the plurality of pulse trains are respectively applied to arbitrary positions and directions. As a result, slices having different contrasts can be simultaneously or individually changed in position and direction, so that a desired slice can be quickly determined.

According to still another preferred embodiment, the image generating means reconstructs the MR signals of a plurality of slices to which the plurality of pulse trains are applied separately, and continuously reconstructs the MR signals for each reconstruction. And means for displaying. This allows images with different contrasts to be displayed continuously,
The desired slice can be quickly determined, and the image inside the imaging target after the slice determination can be observed without requiring a new sequence starting operation.

Further, in each of the above-described configurations, for example, the plurality of slices to which the plurality of pulse trains are individually applied are a plurality of slices obtained from the same position.

The plurality of slices to which the plurality of pulse trains are respectively applied are located at different slice positions.
A plurality of slices in which some of those positions overlap each other may be used. Thereby, a plurality of slices having different contrasts can be regarded as being collected from almost the same slice position.

Further, the plurality of slices to which the plurality of pulse trains are individually applied may be a plurality of slices located adjacent to each other.

Further, as one example, the plurality of slices to which the plurality of pulse trains are applied separately include a slice for applying the pulse train for emphasizing the high-speed scanning property, and two slices for applying the pulse train for emphasizing the image quality. May be three slices sandwiched from both sides.
Thereby, a plurality of slices having different contrasts can be regarded as being collected from almost the same slice position.

Further, for example, the plurality of pulse trains may be arranged so as to be interleaved with each other on a time axis. As a result, the scan time can be further reduced. When a sequence is set so as to thin out RF excitation for a certain slice by this interleaving, a repetition time TR that is significantly different from that of another slice can be set, and the contrast can be changed accordingly.

Further, according to the magnetic resonance imaging method of the present invention, in a method of continuously obtaining MR images of an imaging object based on an interactive imaging method, a plurality of pulse trains having different imaging parameters and scanning slices individually. A pulse sequence comprising the following steps: applying the pulse sequence to the imaging target to collect MR signals; and generating the MR image from the MR signals. As a result, as described above, a desired imaging slice can be quickly set in a short time, and there is no need to separately activate a high-contrast pulse sequence as in the related art. It is possible to provide an interactive imaging method in which the above burden is reduced.

[0023]

Embodiments of the present invention will be described below with reference to the drawings.

(First Embodiment) The first embodiment is described as follows.
This will be described with reference to FIGS.

FIG. 1 shows a schematic configuration of a magnetic resonance imaging apparatus according to this embodiment.

This magnetic resonance imaging apparatus has a substantially cylindrical static magnetic field magnet 1, and this magnet 1 generates a static magnetic field in an imaging region in its bore. In the bore of the magnet 1, a shim coil 2, a gradient coil 3, and an RF (high frequency) probe 4 are arranged.

The shim coil 2 is driven by a shim coil power supply 5 and generates a magnetic field for correcting non-uniformity of a static magnetic field. For convenience, the direction of the static magnetic field is represented by rectangular coordinates X,
It is taken in the direction of the Z axis of the Y and Z systems.

The gradient magnetic field coil 3 is driven by a gradient magnetic field power supply 6 and generates linear gradient magnetic field pulses corresponding to control values in the directions of three orthogonal axes (X, Y, Z axes). This gradient magnetic field is superimposed on the static magnetic field and gives spatial position information in each axial direction.

The RF probe 4 is provided inside the gradient coil 3 and includes the RF coil itself and a tuning / matching circuit for tuning the resonance frequency of the RF coil. Tuning can be performed at the resonance frequency of the nuclide of interest, for example, protons.
The RF probe 4 is connected to a transmitter 7 and a receiver 8 via a duplexer (not shown). Therefore R
The F probe 4 controls the switching of the duplexer,
It is connected to the transmitter 7 during transmission and connected to the receiver 8 during reception. In the present embodiment, the RF probe 4 is a probe for both transmission and reception. However, the RF probe 4 may be provided with a configuration separated into a transmission-only probe and a reception-only probe.

Further, the magnetic resonance imaging apparatus includes, as components for transmission / reception and system control:
It comprises a transmitter 7, a receiver 8, a data collector 9, a computer system 10, a display 11A, a console 11B, a sequence controller 12, and a parameter controller 13.

The transmitter 7 supplies a high-frequency current pulse to the RF probe 4. As a result, the RF probe 4 generates a high-frequency magnetic field (rotating magnetic field) having a frequency matching the resonance frequency of the target nuclide in the bore space of the magnet 1 including the imaging region.

The receiver 8 receives, via the RF probe 4, a magnetic resonance signal generated from proton spins of the subject to be imaged, amplifies the signal, detects the signal, and performs A / D conversion. As a result, the receiver 8 outputs digital echo data.

The data collector 9 temporarily stores the echo data, and transfers the stored data to the computer system 10 for each collection unit or collectively.

The computer system 10 has a control center function of the whole system, a function of reconstructing an MR image of a subject based on echo data, and an interface function of changing an imaging slice based on an interactive imaging method. And This interface function is realized, for example, by the configuration described in Japanese Patent Application Laid-Open No. 2000-189400.

Images and data related to the functions of the computer system 10 are displayed on the display 11A. Also,
The operator can input necessary information and data to the computer system 10 via the console 11B.

A sequence controller (also called a sequencer) 12 executes a pulse sequence for collecting MR data, and as a result, a shim coil power supply 5, a gradient magnetic field power supply 6, a transmitter 7, a receiver 8, and a data The operation of the collector 9 is controlled. FIG. 3 shows an example of the pulse sequence.

The slice rotation information set by the interface function of the computer system 10 is sent to the sequence controller 12. The computer system 10 supplies the rotation information to the parameter controller 13 and converts the rotation information into a gradient magnetic field intensity corresponding to the slice (cross-section) rotation amount. The gradient magnetic field intensity is output to the gradient magnetic field power supply 6, and the gradient magnetic field pulse generated by the gradient magnetic field coil 3 is changed and controlled so as to obtain a desired amount of slice rotation.

The offset frequency information corresponding to the slice shift amount set by the interface function of the computer system 10 is transmitted to the sequence controller 12.
Sent to Since the sequence controller 12 sends a control signal corresponding to the offset frequency to the transmitter 7, the frequency of the high-frequency magnetic field generated by the transmitter 7 is changed and controlled by the offset frequency.

The rotation amount and the shift amount are not limited to being set by the computer system 10, but may be set by the sequence controller 12. In addition, a rotation matrix action module and a cross section shift action module capable of outputting an offset corresponding to a control signal corresponding to the rotation amount and the shift amount are provided separately, and these modules directly set the rotation amount and the shift amount. It can also be configured as follows. Thereby, the processing time can be shortened.

FIG. 2 shows a schematic procedure executed by the computer system 10 and the sequence controller 12 in cooperation when executing the interactive imaging method.

First, a pulse sequence for executing an interactive imaging method with a slice (cross section) change is selected (procedure (a)), and executed to collect echo data (procedure (b)).

This pulse sequence is as shown in FIG.
It is set using an FE-based pulse train from the viewpoint of the advantage of the data collection time and the like. Specifically, the repetition time TR =
N first FE-system pulse trains A1, A2,... AN (flip angles θ = θ1 of respective RF frequencies) arranged in time series to form TR1, and a repetition time TR = TR
2 (> TR1) and M sets of the second FE-system pulse trains B1, B2,... BM (the flip angle θ of each RF frequency θ = θ2) arranged in time series are further arranged in time series. Have been. Each set of FE-system pulse trains A1 (AN,
B1 to BM) include an excitation RF pulse, a selective excitation slice gradient magnetic field Gs, a phase encoding gradient magnetic field Ge, and a read gradient magnetic field Gr for echo reading (frequency encoding).

Here, the repetition time TR1 is set to a short time to emphasize high-speed image data collection, and the flip angle θ1 is set to a small value (shallow). On the other hand, the repetition time TR2 and the flip angle θ2 are set to longer and deeper values aiming at improving image quality rather than high-speed collecting performance.

The repetition time TR and the flip angle θ are imaging parameters independent of each other, and the flip angles θ = θ1, θ
2 may be set by default, but it is preferable that the operator can manually set or switch the setting every time an image is taken. Therefore, a value of θ1 = θ2 may be adopted.

When the pulse sequence shown in FIG. 3 is repeatedly executed, the first FE pulse trains A1, A2,..., AN are repeated by the amount of phase encoding, and the second FE pulse trains B1, B
2,... BM are repeated by the amount of phase encoding. In the present embodiment, the slices to be selectively excited in each of the FE pulse trains A1 to AN and B1 to BM are set to have the slice gradient magnetic field Gs and the carrier frequency of the excitation RF wave so as to be at the same slice position of the imaging target. . For this reason, the first FE pulse trains A1 to AN are repeatedly applied for a total of n phase encodings, thereby collecting echo data necessary for image data of one slice.
In addition, the remaining second FE pulse trains B1 to BM are m
The echo data is repeatedly applied by the amount corresponding to the phase encoding, so that echo data necessary for image data of another slice located at the same position as the above-mentioned slice is collected in time.

The echo data of two slices (although the slice positions are the same) collected according to this pulse sequence are separately reconstructed by the computer system 10 (procedure (c)). Thus, the reconstructed image data is displayed on the display 11A, for example, as shown in FIG. 4 (procedure (d)). In this display mode, images IM1 and IM2 of two slices generated by alternately collecting data from the same slice position by N (M) phase encodings are displayed side by side on the display 11A.

According to this display, one slice image I
M1 is mainly a proton-density-enhanced image in which the repetition time TR is shortened (= TR1) and the flip angle θ is set shallow (= θ1) to focus on high-speed acquisition, as in the conventional interactive imaging. It is. The image IM1 is imaged in a short time, and the outline of the imaging region can be known. However, depending on the region, the contrast of the soft tissue may be insufficient or the resolution may be reduced.

To complement this, another image IM2 that has been collected in parallel with the above-mentioned image IM1 is displayed at the same time. Since the image IM2 gives priority to the image quality, the image IM2 has higher contrast and resolution than the above-described image IM1, and can more clearly show a portion that is difficult to observe in the image IM1.

[0049] For this reason, the operator has to use both images IM.
A command to change the imaging slice is issued using the slice change interface function implemented in the computer system 10 while looking at 1, IM2 (procedure (e)). In response to this change, the rotation matrix reflecting the changed slice and the slice offset amount are sent to the sequence controller 12 (procedure (f)).

Thereafter, the processing procedure returns to the procedure (b), and the above-described processing is repeatedly executed. Thus, the interactive imaging method is performed.

For this reason, according to the present embodiment, in the case of conventional interactive imaging, only a single sequence of a short repetition time TR is used, so that only an image with a low contrast ratio can be obtained. Can improve the problem.

That is, when performing interactive imaging, a plurality of sets of FE pulse trains A1 to AN (B1 to B2) having different pulse train repetition times TR and flip angles θ are used.
Since M) is sequentially and repeatedly performed in time series, a plurality of slice images having different contrasts and resolutions can be obtained for a plurality of slices at the same position. Therefore, unlike the conventional interactive imaging in which only the high-speed performance is emphasized, a clearer image in which the image quality is emphasized can be obtained at the same time while the slice position / angle is changed interactively. For this reason, a doctor can obtain an image with a high contrast ratio while imaging and observing a target cross section (slice) at a high speed, and thus can quickly set a slice position at which a lesion position is more accurately captured. The physician does not need to bother with activating a high-contrast pulse sequence as in the prior art.

Therefore, the desired slice can be positioned easily and in a short time, and the time and labor required from the positioning of the imaging slice to the imaging can be remarkably reduced. As a result, the efficiency of diagnosis can be improved and the burden on operation can be reduced. In addition, a diagnosis can be made without overlooking a dynamic disease state.

In the first embodiment, various modifications are possible.

According to the first modification, in each of the two sets of FE pulse trains A1 to A2 (B1 to BM) described above, k
It is desirable that the echo data in the vicinity of the zero encoding amount in the (frequency) space be located at the temporal end of the FE pulse trains A1 to AN (B1 to BM). Thereby, the repetition time TR is changed from TR1 to TR2, and TR2
The excitation condition of the magnetization becomes discontinuous at the portion where the operation is switched from to TR1, so that the independence of the contrast with respect to the two slices at the same slice position acquired with a time lag can be maintained.

According to the second modification, FIG.
Of the 2N (M = N) sets of pulse trains A1 to AN and B1 to BM each of the N (M) sets described in (1) above, the first or second half of the pulse trains A1 to AN (B1 to BM) are other than the FE type. of,
For example, an SE-based pulse train may be provided. This allows
Although the temporal resolution is slightly sacrificed, a plurality of types of MR images having different image qualities such as contrast and spatial resolution can be simultaneously displayed.

Further, in the third modification, in the magnetic resonance imaging apparatus according to the first embodiment, it is preferable that the flip angle θ can be changed as an imaging parameter during the interactive imaging. FIG. 5 shows a procedure for realizing an example of this configuration. In FIG.
In the same procedure as that described above, a procedure (e ′) including a process of determining whether to change the flip angle θ and inputting a change in the flip angle θ is inserted between the procedures (e) and (f). Have been. The control parameter of the flip angle thus changed is transmitted to the transmitter 7 in the processing of the procedure (f),
The flip angle of the excitation RF wave is updated.

(Second Embodiment) Referring to FIG.
The magnetic resonance imaging apparatus according to the embodiment will be described.

This apparatus is characterized in that images of a plurality of adjacent slices (for example, two slices) in the vicinity of the data acquisition area are acquired with different image qualities.
Note that the hardware configuration of this device and the devices implemented in the following embodiments are the same as those in FIG.

In order to realize this feature, the sequence controller 12 executes a pulse sequence shown in FIG.

As shown in FIG. 6A, this pulse sequence is composed of two sets of first FE-system pulse trains A1 and A2 arranged in time series so as to form a repetition time TR (flip of each RF frequency). Angle θ = θ1) and two sets of second FE-system pulse trains B1 and B2 arranged in time series so as to form the same repetition time TR (the flip angle θ = θ2 of each RF frequency). Are arranged in an interleaved manner.

Each set of FE pulse trains A1 (A2, B
1, B2) are an excitation RF pulse, a selective excitation slice gradient magnetic field Gs, a phase encoding gradient magnetic field Ge, and a read gradient magnetic field G for echo reading (frequency encoding).
r. Among these, as shown in FIG. 6B, in one set of FE pulse trains A1 and A2, the carrier frequency of the excitation RF pulse and the slice gradient magnetic field Gs are set so as to selectively excite one slice SL1. In the other set of FE pulse trains B1 and B2, the carrier frequency of the excitation RF pulse and the slice gradient magnetic field Gs are set so as to selectively excite the other slice SL2.

As an example, one set of FE pulse train B
Each of the flips θ = θ2 based on 1, B2 is set to a small value (shallower) in order to emphasize high-speed image data collection.
On the other hand, the flip angle θ = θ1 based on the other set of FE pulse trains A1 and A2 is set to a deeper value aimed at improving the image quality rather than the high-speed collecting property.

As a result, the display 11A displays the first
As in the embodiment, two slices SL1 and S
Images of L2 can be obtained continuously with different contrasts. Therefore, according to the second embodiment, the same operation and effect as in the first embodiment can be obtained.
In particular, the positions of the plurality of slices SL1 and SL2 having different contrasts are different adjacent positions, even in a range that can be regarded as substantially the same imaging region.

For this reason, unlike the case where two slice images are obtained from the same position, there is no need to be limited to the time until the spin balance at the time of data collection for each image.
Therefore, as shown in FIG.
Since various types of pulse sequences can be assembled in an interleaved manner, the time required for each repetition of the entire pulse sequence can be shortened, and thus the scan time can be further reduced.

In the second embodiment, as shown in FIG. 5, the flip angle (excitation angle) θ (θ1, θ2) can be arbitrarily changed during the echo data collection. You can also. Thereby, a plurality of types of contrast can be further adjusted in real time.

(Third Embodiment) Referring to FIG.
The magnetic resonance imaging apparatus according to the embodiment will be described.

This apparatus also collects images of a plurality of adjacent slices (for example, two slices) in the vicinity of the data collection area with different image qualities, as in the second embodiment. Features.

In order to realize this feature, the sequence controller 12 executes a pulse sequence shown in FIG.

As shown in FIG. 7 (a), this pulse sequence is composed of three sets of first FE pulse trains A1 to A3 arranged in time series so as to form a repetition time TR = TR1.
(The flip angle θ of each RF frequency = θ1) and 2
Two sets of second FE-system pulse trains B arranged in time series so as to form a double repetition time TR = TR2 = 2 · TR1
1, B2 (flip angle of each RF frequency θ = θ
2) are arranged in a time series in an interleaved manner. That is, the first pulse train B1 of the second FE pulse trains B1 and B2 is applied during the repetition time TR1 of the first FE pulse trains A1 and A2, and the application after the pulse train A2 is performed. It is set to a form that has been thinned once.

As shown in FIG. 7B, one set of FE pulse trains A1 to A3 has a carrier frequency of the excitation RF pulse and a slice gradient magnetic field Gs so as to selectively excite one slice SL1. In the FE pulse trains B1 and B2 of the other set, the carrier frequency of the excitation RF pulse and the gradient magnetic field for slice Gs are set so as to selectively excite the other slice SL2. In addition, slice SL
1 and SL2 have different frame rates.

As an example, one set of FE pulse train B
Each of the flips θ = θ2 based on 1, B2 is set to a small value (shallower) in order to emphasize high-speed image data collection.
On the other hand, the flip angle θ = θ1 based on the other set of FE pulse trains A1 to A3 is set to a deeper value aimed at improving the image quality rather than the high-speed collecting property.

As a result, the same functions and effects as those of the second embodiment can be obtained.

In the third embodiment, as shown in FIG. 5, the flip angle (excitation angle) θ (θ1, θ2) can be arbitrarily changed during the echo data collection. Is preferred. Thereby, a plurality of types of contrast can be further adjusted in real time.

(Fourth Embodiment) Referring to FIG.
The magnetic resonance imaging apparatus according to the embodiment will be described.

This apparatus is also characterized in that images of a plurality of slices (for example, two slices) in or near the data acquisition region are acquired by changing the image quality by changing the type of the pulse sequence.

In order to realize this feature, the sequence controller 12 executes a pulse sequence shown in FIG.

As shown in FIG. 8, this pulse sequence has two sets of FE-system pulse trains C1 and C2 arranged in time series so as to form a repetition time TR = TR1 (the flip angle θ of each excitation RF frequency = θ1) and two SE-system pulse trains D1 and D2 arranged in time series so as to form a repetition time TR2 (equal to or different from TR1).
(The flip angles θ of the respective excitation RF frequencies = θ2) are arranged in a time series in an interleaved manner.

Of these, one of the FE pulse trains C1 and C2
Is the excitation R so that one slice SL1 is selectively excited.
The carrier frequency of the F pulse and the gradient magnetic field for slice Gs are set, and the other SE-system pulse trains B1 and B2 form the carrier frequency of the excitation RF pulse and the gradient magnetic field for slice Gs so as to selectively excite the other slice SL2. Is set.

At this time, both slices SL1, SL2
May be set to be adjacent to each other as in the above-described embodiment (for example, see FIG. 7B), but as shown in FIG. 9, the two slices SL1 and SL2 are set so as to partially overlap each other. It is desirable. As a result, the relevance of the images obtained from both slices SL1 and SL2 is higher than in the case of a mere adjacent slice.

By changing the type of pulse sequence in this manner, one slice SL1 can be imaged at a high speed by the FE method, while the other slice SL2 can be imaged with a high contrast by the SE method. For this reason, the contrast of the images of both slices SL1 and SL2 can be changed, and an interactive MR that achieves both high-speed imaging and high-contrast imaging as in the above-described embodiment.
I can do it. In this case, the flip angle θ (θ
1, θ2) may be changed to further increase the degree of freedom of contrast differentiation.

FIG. 10 shows another example of the interactive imaging using the pulse trains of the FE method and the SE method. The pulse sequence shown in the figure is the echo time T of the SE-system pulse train D for acquiring the slice SL2.
During E, FE pulse trains C1 to C1
3 is used to collect data. in this case,
A rewind pulse is inserted in consideration of the rewinding of the magnetization between the pulse sequences of the FE method and the SE method.
In the case of the oblique section, a rewind pulse is also applied to the slice gradient magnetic field Gs.

As described above, the repetition time TR = TR2 by the SE method can be set longer by incorporating that of the FE method into the pulse train of the SE method in consideration of the unwinding of the magnetization. It is possible to obtain images with different contrasts that more positively utilize the difference in the method.

In the configuration shown in FIG. 10, the resolving power can be changed by rewinding the magnetization of the phase encoding gradient magnetic field Ge. However, in this case, the frame rates of the two images are different.

Although the slice positions of the two images obtained by the above-described second to fourth embodiments and their modifications can be regarded as substantially the same positions, they do not completely match. In order to suppress the decrease in the relevance between images due to this positional shift, as one example, the slice thickness of a basic slice (for example, a slice that emphasizes high definition and high contrast) is compared with another slice thickness. What is necessary is just to set the thickness of a slice (for example, a slice that emphasizes high-speed imaging) to be thin.

As shown in FIGS. 11A and 11B,
Two slices SL2 sandwiching a basic slice SL1 (for example, a slice with high contrast and high definition)
By using an excitation pulse (see FIG. 3A) having a characteristic of selectively exciting a slice (for example, a slice in which high-speed imaging is emphasized), it is possible to suppress the decrease in the relevance between the images. In this case, it is important to adjust the slice thickness of each slice. Usually, in order to minimize the influence of displacement between the slices SL1 and SL2, the slice SL2 on both sides is required.
It is effective to set. This slice SL2
As the frequency selection characteristics, a method of giving a frequency offset to a pulse waveform providing a single slice characteristic and a method of performing amplitude modulation on such a pulse waveform are known.

When collecting data for a plurality of slices, the direction of each slice can be made different. In this case, it is preferable that the section setting change interface prepared in the computer system 10 includes a setting button for specifying a direction and a pulse sequence for each slice.

Further, in each of the above embodiments, it may be effective to exchange the position information of each slice. To cope with this, the computer system 10 stores and exchanges the position information of each slice, and
It is desirable to have a function of sending to

Further, the present invention is not limited to the configuration of the above-described embodiment and its modifications, but can be embodied in other forms without departing from the gist of the claims.

[0090]

As described above, according to the present invention,
In interactive imaging, images of two or more slices at the same position or in close proximity to an imaging target are acquired in parallel, and at least one of the slices is maintained at a high contrast unlike the other slices. That is, it is possible to continuously obtain images with excellent time resolution in a short time and continuously obtain images with high contrast almost simultaneously. As a result, a desired imaging slice can be set in a short time. On the other hand, the time and effort of newly activating a high-contrast pulse sequence as in the related art is unnecessary, and as a whole, the positioning of the imaging slice can be reduced The time and labor required for imaging can be significantly reduced, whereby the efficiency of diagnosis can be improved and the burden on operation can be reduced.

[Brief description of the drawings]

FIG. 1 is a functional block diagram showing an example of a configuration of a magnetic resonance imaging apparatus according to an embodiment of the present invention.

FIG. 2 is a flowchart illustrating an outline of a procedure of interactive imaging.

FIG. 3 is a diagram of a pulse sequence used in the first embodiment.

FIG. 4 is a diagram illustrating a display mode of two images having different contrasts.

FIG. 5 is a diagram of a pulse sequence used in a modification of the first embodiment.

FIG. 6 is a diagram showing a pulse sequence and a slice position used in the second embodiment.

FIG. 7 is a diagram showing a pulse sequence and a slice position used in the third embodiment.

FIG. 8 is a diagram showing a pulse sequence used in the fourth embodiment.

FIG. 9 is a view for explaining two slice positions in interactive imaging performed in the fourth embodiment.

FIG. 10 is a diagram showing a pulse sequence used in one modification of the fourth embodiment.

FIG. 11 is an explanatory diagram of a slice position setting method applicable to the second to fourth embodiments and their modifications.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Magnet 3 Gradient magnetic field coil 4 RF probe 6 Gradient magnetic field power supply 7 Transmitter 8 Receiver 9 Data collector 10 Computer system 11A Display 11B Console 12 Sequence controller 13 Parameter controller

Claims (12)

[Claims] 1. A magnetic resonance imaging apparatus in which an MR image of an imaging target is continuously obtained based on an interactive imaging method, wherein a pulse sequence including a plurality of pulse trains having different imaging parameters and scanning slices individually. A magnetic resonance imaging apparatus comprising: a signal collecting unit that collects an MR signal by applying to the imaging target; and an image generating unit that generates the MR image from the MR signal. 2. The magnetic resonance imaging apparatus according to claim 1, wherein the plurality of pulse trains include a pulse train focused on high-speed scanning based on the interactive imaging method and the MR train.
A magnetic resonance imaging apparatus including a pulse train emphasizing image quality. 3. The magnetic resonance imaging apparatus according to claim 2, wherein the imaging parameter is at least one of a repetition time of the plurality of pulse trains and a flip angle of a high-frequency pulse included in the pulse train. 4. The magnetic resonance imaging apparatus according to claim 2, wherein the imaging parameter is a type of the plurality of pulse trains. 5. The magnetic resonance imaging apparatus according to claim 1, further comprising: a slice setting unit configured to set a plurality of slices to which the plurality of pulse trains are individually applied to an arbitrary position and an arbitrary direction. 6. The magnetic resonance imaging apparatus according to claim 1, wherein the image generation unit reconstructs the MR signals of a plurality of slices to which the plurality of pulse trains are individually applied, and A magnetic resonance imaging apparatus including a means for continuously displaying images. 7. The magnetic resonance imaging apparatus according to claim 1, wherein the plurality of slices to which the plurality of pulse trains are individually applied are a plurality of slices obtained from the same position. Resonance imaging device. 8. The magnetic resonance imaging apparatus according to claim 1, wherein the plurality of slices to which the plurality of pulse trains are respectively applied are different slice positions. A magnetic resonance imaging apparatus in which a plurality of slices partially overlap each other. 9. The magnetic resonance imaging apparatus according to claim 1, wherein the plurality of slices to which each of the plurality of pulse trains is applied are a plurality of slices located adjacent to each other. Magnetic resonance imaging device. 10. The magnetic resonance imaging apparatus according to claim 2, wherein the plurality of slices to which the plurality of pulse trains are individually applied are slices to which the high-speed scan-oriented pulse trains are applied, and wherein the slices are applied to the image quality. Apply pulse train emphasizing
A magnetic resonance imaging apparatus in which three slices are positioned so as to sandwich the slice from both sides. 11. The magnetic resonance imaging apparatus according to claim 1, wherein the plurality of pulse trains are arranged so as to be interleaved with each other on a time axis. 12. A magnetic resonance imaging method for continuously obtaining an MR image of an imaging target based on an interactive imaging method, comprising: preparing a pulse sequence including a plurality of pulse trains having different imaging parameters and individually scanning slices; A magnetic resonance imaging method, wherein the pulse sequence is applied to the imaging target to collect an MR signal, and the MR image is generated from the MR signal.