JPH11276452A - MR imaging method and apparatus - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To collect signals using only an optimum surface coil among a plurality of surface coils, increase an SN ratio, reduce a memory usage, and perform high-speed data processing. SOLUTION: A sequencer 9 for executing a pre-pulse sequence or an imaging pulse sequence, a reception system 13 for collecting echo signals via each of surface coils constituting the array coil 5, a computer 7, and each of the array coils 5 A coil switching unit 29 for selectively switching the surface coils, a surface coil selection unit 31 for selecting at least one surface coil whose signal intensity of the echo signal is equal to or more than a certain value during execution of the pre-pulse sequence, and execution of the imaging pulse sequence Occasionally, an image reconstruction device 33 that collects echo signals from only the selected surface coil and reconstructs an image of the selected slice is provided, and does not collect data from the surface coil having a weak signal intensity.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to nuclear magnetic resonance (N)
More particularly, the present invention relates to a technique for reconstructing a tomographic image based on echo signals collected by an array coil including a plurality of surface coils.

[0002]

2. Description of the Related Art An echo signal is collected by an array coil constituted by arranging a plurality of surface coils so as not to interfere with each other, and a signal from each surface coil is synthesized to reconstruct a tomographic image. The method of effectively expanding the imaging field of view by Magnetic Resonance in Medicine
16, pages 192 to 225, and Japanese Patent Publication No. 4-42937.

[0003]

However, in the case of such a conventional example, there are the following problems. In other words, the signal from the surface coil located immediately below the excitation position is dominant, and the signal intensity decreases as the surface coil is farther from the excitation position. There is a problem that it decreases. In addition, since data is collected from all surface coils that make up the array coil, the amount of memory used increases, the number of images captured decreases, and the amount of processing data increases, and the synthesis process takes time and the throughput increases. There is also a problem that is reduced.

In order to avoid such a problem, it is conceivable that the photographer visually determines a surface coil close to the excitation position and performs imaging using only the surface coil.
It is difficult to grasp their positional relationship and it is not practical.

[0005] The present invention has been made in view of such circumstances, and by collecting signals using only an optimum surface coil among a plurality of surface coils, the SN ratio is improved.
It is an object of the present invention to provide an MR imaging method and apparatus capable of increasing the ratio, using a small amount of memory, and performing high-speed data processing.

[0006]

The present invention has the following configuration to achieve the above object. That is, an MR imaging method according to claim 1 is an MR imaging method for performing imaging based on a signal from an array coil composed of a plurality of surface coils using nuclear magnetic resonance (NMR phenomenon). ,
(A) A pre-pulse sequence is executed to select one slice in a direction orthogonal to the arrangement direction of the surface coils, and an echo signal generated by exciting the selected slice is output to all surfaces constituting the array coil. (C) obtaining a reconstructed image after performing in advance a process of collecting through a coil and (b) a process of selecting at least one surface coil in which the signal strength of the collected echo signal is equal to or more than a certain value. (C) collecting an echo signal generated by exciting the selected slice by using only the selected surface coil; and (d) collecting the echo signal based on the collected echo signal. And a step of reconstructing the image.

An MR imaging apparatus according to a second aspect uses nuclear magnetic resonance (NMR phenomenon) to perform imaging based on signals from an array coil composed of a plurality of surface coils. In the apparatus, a pulse group including an excitation RF pulse is applied to a subject placed in a static magnetic field to execute a pre-pulse sequence or an imaging pulse sequence, and the pulse sequence execution unit operates. Collecting means for collecting, via each of the surface coils constituting the array coil, an echo signal generated by the operation, and a surface for selectively switching each surface coil of the array coil and connecting to the collecting means. A coil switching means for executing a pre-pulse sequence prior to the imaging pulse sequence; One slice in the direction orthogonal to the array direction of the coils is selected, and echo signals generated by exciting the selected slice are collected through all the surface coils constituting the array coil, and the selected slice is collected. Surface coil selecting means for selecting at least one surface coil having a signal strength of an echo signal collected from a predetermined value or more, and collecting only the surface coil selected by the surface coil selecting means by the surface coil switching means. After connecting to the means, an imaging pulse sequence is executed, an echo signal generated by exciting the selected slice is collected using only the surface coil, and an image of the selected slice is formed based on the collected echo signal. Image reconstructing means for reconstructing.

According to a third aspect of the present invention, there is provided an MR imaging method which utilizes nuclear magnetic resonance (NMR phenomenon) to perform imaging based on signals from an array coil comprising a plurality of surface coils. In the method, (a) echo signals from the subject along the arrangement of the surface coils are collected through all the surface coils, and an image of a maximum field of view (hereinafter, referred to as a maximum field image) that can be captured by the array coil is displayed. (B) indicating a desired region of interest in the maximum field of view image; (c) the positional relationship between the region of interest and the maximum field of view image; and the position of the maximum field of view image and each surface coil. Selecting at least one surface coil close to the region of interest based on the relationship; and (d) selecting an echo signal from the region of interest from the selected surface coil. Collected using Runomi the steps of reconstructing an image of the region of interest and is characterized in that it consists of.

An MR imaging apparatus according to a fourth aspect of the present invention utilizes nuclear magnetic resonance (NMR phenomenon) to perform imaging based on signals from an array coil composed of a plurality of surface coils. In the apparatus, a collecting unit that collects an echo signal generated from a subject via each of surface coils constituting the array coil, and selectively switches each surface coil of the array coil to the collecting unit. An echo signal from the subject is collected via the collecting means along the surface coil switching means to be connected and the arrangement of the surface coils, and an image of a maximum visual field that can be photographed by the array coil (hereinafter referred to as a maximum visual field image) ), Indicating means for indicating a desired region of interest in the maximum field of view image, and displaying the area of interest and the maximum field of view. Based on the positional relationship with the image and the positional relationship between the maximum field-of-view image and each surface coil, a surface coil selecting unit that selects at least one surface coil close to the region of interest, and the surface coil selecting unit. After connecting only the selected surface coil to the collecting means by the surface coil switching means, an echo signal from the region of interest is collected using only the surface coil, and the interest signal is collected based on the collected echo signal. Image reconstruction means for reconstructing the image of the area.

[Operation] The operation of the method according to the first aspect is as follows. First, a pre-pulse sequence is executed to excite the selected slice, and echo signals are collected through all surface coils. Then, at least one of the surface coils whose signal strength is equal to or more than a certain value is selected. This excludes surface coils that are far from the selected slice and have low signal strength. Next, echo signals generated by executing the imaging pulse sequence are collected only from the surface coils selected as described above. Although the image of the selected slice is reconstructed based on the collected echo signals, signals from surface coils having low signal strength are not collected, and the number of data to be processed can be reduced.

The operation of the device invention according to claim 2 is as follows. The surface coil selecting means executes the pre-pulse sequence by the pulse sequence executing means to excite the selected slice, and collects the echo signal by the collecting means via all the surface coils. Based on the echo signals collected in this way, the surface coil selecting means selects at least one surface coil whose signal strength is equal to or higher than a certain value. The image reconstructing means executes the imaging pulse sequence by the pulse sequence executing means after connecting only the selected surface coil to the collecting means by the surface coil switching means. Therefore, although the image of the selected slice is reconstructed based on the collected echo signals, signals from surface coils having low signal strength are not collected, and the number of data to be processed can be reduced.

The operation of the method according to the third aspect is as follows. First, echo signals are collected through all surface coils, and a maximum field-of-view image (generally, low resolution) is displayed based on the echo signals. The photographer designates a region of interest to be photographed while viewing the displayed maximum field of view image. Since the positional relationship between the region of interest and the maximum field-of-view image is known at this time, a surface close to the designated region of interest is determined based on this positional relationship and the positional relationship between the maximum field-of-view image and each surface coil known in advance. The coil can be selected automatically. Echo signals are collected only from the surface coils selected in this way, and an image of the region of interest is reconstructed. However, signals from surface coils far from the region of interest are not collected, and the number of data to be processed is reduced. be able to.

The operation of the device according to the fourth aspect is as follows. The display means displays a maximum field-of-view image based on echo signals collected from all surface coils via the collection means. The photographer indicates a region of interest in the maximum field of view image by the instruction means. Since the positional relationship between the region of interest and the maximum field of view image is known at this time, this positional relationship,
The surface coil selecting means selects a surface coil close to the region of interest based on the previously determined maximum visual field image and the positional relationship between the surface coils. The image reconstruction means connects only the selected surface coil to the collection means by the surface coil switching means, collects echo signals and reconstructs an image of the region of interest, but collects signals from surface coils far from the region of interest. Therefore, the number of data to be processed can be reduced.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. <First Embodiment> FIG. 1 is a block diagram showing a schematic configuration of an MR imaging apparatus according to a first embodiment.

The subject M is mounted inside a static magnetic field formed by a main magnet (not shown) and a gradient magnetic field formed by a gradient magnetic field coil 1 for applying a magnetic field to the static magnetic field. The gradient magnetic field coil 1 includes three gradient magnetic fields Gr and G changing in three directions orthogonal to xyz.
It is composed of three sets of coils (not shown) for superimposing p and Gs pulses (composed of readout gradient magnetic field pulses, phase encoding gradient magnetic field pulses, and slice selection gradient magnetic field pulses). The RF coil 3 irradiates the subject M with an excitation RF pulse or the like.
Is for receiving an NMR signal generated from the subject M. The RF coil 3 and the array coil 5 are attached to the subject M.

As shown in FIG. 2, the array coil 5 is constituted by, for example, four surface coils 5a to 5d arranged one-dimensionally. Each of the surface coils 5a to 5d is configured to overlap by a predetermined distance so that adjacent coils do not interfere with each other.

The computer 7 controls the overall operation of the apparatus as a whole, and the sequencer 9 controls the sequence of acquiring data for tomographic image reconstruction under the control of the computer 7. It has a function of giving various commands to the transmission system 11, the reception system 13, and the gradient power supply 15. The gradient magnetic field pulse G
x, Gy, Gz (for example, corresponding to Gp, Gr, Gs to be described later) are respectively given a command to drive each of the gradient magnetic field coils 1 to generate a gradient magnetic field pulse G to be described later.
The waveforms and generation timings of p, Gr, and Gs are determined.

The sequencer 9 (pulse sequence execution means) controls the modulator 17 of the transmission system 11 and controls excitation RF in a pre-pulse sequence or an imaging sequence described later.
The waveform and generation timing of a modulated wave such as a pulse or a refocus RF pulse are defined. The modulator 17 is provided with a carrier having a frequency corresponding to the resonance frequency of the subject M from the high frequency generator 19, and the carrier is modulated by the modulator 17. The RF signal whose waveform and generation timing are defined in this manner is supplied to the above-described RF coil 3 via the transmission amplifier 21.
R such as an excitation RF pulse (typically a 90 ° pulse) or a refocus RF pulse (generally a 180 ° pulse)
The subject M is irradiated as an F pulse. Note that the sequencer 9 corresponds to the pulse sequence executing means in the present invention.

The NMR signal generated from the subject M is received by the array coil 5 and sent to the receiving system 13.
The receiving system 13 includes a receiving amplifier 23 (23a to 23d),
Phase detector 25 (25a to 25d) and A / D converter 2
7 (27a to 27d) and a coil switching unit 29 (29a to 29d) for selectively switching each of the surface coils 5a to 5d constituting the array coil 5 to the reception amplifier 23.
d). These are all surface coils 5
It is configured to operate individually for each of a to 5d.
The coil switching section 29 corresponds to the surface coil switching means in the present invention.

The coil switching section 29 performs a switching operation in accordance with an instruction from the sequencer 9, and switches each coil such that all the surface coils 5a to 5d are connected to the receiving amplifiers 23a to 23d when the pre-pulse sequence is executed. The sections 29a to 29d operate so that at the time of execution of the imaging sequence, at least one of the surface coils 5a to 5d whose intensity of the NMR signal exceeds a certain value from the result of the pre-pulse sequence is connected to the reception amplifier 23. The coil switching units 29a to 29d operate. Then, after the NMR signal given to the receiving amplifier 23 is phase-detected by the phase detector 25, it is converted into digital data by the A / D converter 27, and the NMR signal is taken into the computer 7 as data. I have. For example, the surface coil 5
If the signal intensity of the signal a exceeds a certain value, only the coil switching unit 29a closes during the execution of the imaging pulse sequence,
Only the surface coil 5a is connected to the receiving amplifier 23a, and the NMR signal received by the surface coil 5a is provided to the computer 7 via the phase detector 25a and the A / D converter 27a. Which of the surface coils 5a to 5d is connected to the receiving amplifier 23 is determined by the surface coil selector 31 connected to the host computer 7. The host computer 7 and the receiving system 1
Reference numeral 3 corresponds to the collecting means of the present invention, and the surface coil selecting unit 3
1 corresponds to a surface coil selecting means.

The NMR signal data captured by the computer 7 is subjected to data processing by an image reconstruction device 33 (image reconstruction means) connected to the computer 7 to reconstruct a tomographic image. The data processing refers to, for example, reconstructing a tomographic image by a two-dimensional Fourier transform method or the like. When data is collected using two or more of the surface coils 5a to 5d, an addition method is used. One tomographic image is reconstructed by synthesizing using, for example,.

The tomographic image thus reconstructed is C
The information is output to a display unit 35 composed of an RT or the like, and is used for diagnosis by an operator or an operator. Further, the computer 7 is also connected to a mouse 37 which is a pointing device for instructing a partial enlargement of a tomographic image displayed on the display unit 35, a processing item, and the like.

Next, the operation of the apparatus configured as described above will be described with reference to FIGS. 3 is a diagram showing a positional relationship between the array coil 5 and the subject M, FIG. 4 is an example of a pre-pulse sequence, and FIG. 5 is a time chart illustrating an example of an imaging pulse sequence. FIG. 6 is a schematic diagram showing the signal intensity of the echo signal obtained from each surface coil for each slice.

[Pre-Pulse Sequence] First, the subject M
The RF coil 3 and the array coil 5. The positional relationship between the surface coils 5a to 5d and the slices SL1 to SL7 in the subject M is as shown in FIG. That is, the slices SL1 to SL7 are set so as to be orthogonal to the arrangement direction of the surface coils 5a to 5d, the slice SL1 is orthogonal to only the surface coil 5a, the slice SL2 is only to the surface coils 5a and 5b, and the slice SL3 is to the surface. Slice SL4 only for coil 5b
Represents only the surface coils 5b and 5c, slice SL5 represents only the surface coil 5c, and slice SL6 represents the surface coils 5c and 5c.
In only 5d, the slice SL7 is orthogonal to only the surface coil 5d.

The sequencer 9 activates the coil switching unit 29 and controls each of the coil switching units 29a to 29d to close. That is, the surface coils 5a to 5d are connected to the respective receiving amplifiers 23a to 23d.

Next, a pre-pulse sequence as shown in FIG. 4 is executed. That is, one excitation RF pulse 50 (90 ° pulse) is irradiated via the RF coil 3, and one refocus RF pulse 51 is irradiated after a predetermined time (FIG. 4A). At the same time as the excitation RF pulse 50,
A slice selection gradient magnetic field pulse 61 for selecting a slice SL1 via the gradient magnetic field coil 1 is generated (FIG. 4).
(B)), a slice-selecting gradient magnetic field pulse 62 is generated simultaneously with the refocusing RF pulse 51. Then, from the irradiation time of the refocus RF pulse 51, the excitation RF
Since the echo signal ES, which is an NMR signal, is generated around the time point at which the irradiation interval between the pulse 50 and the refocus RF pulse 51 has elapsed (FIG. 4E), the dephasing is performed before the irradiation of the refocus RF pulse 51. A gradient magnetic field pulse 71 for reading is generated, and a read gradient magnetic field pulse 72 for performing frequency encoding is generated in accordance with the generation time point of the echo signal ES from the selected slice SL1 (FIG. 4).
(C)), collecting the echo signals ES. In this pre-pulse sequence, it is not necessary to reconstruct a tomographic image from the collected echo signals, and it is preferable not to generate a gradient magnetic field pulse for phase encoding because the signal intensity is important (see FIG. )).

Next, the slice selection gradient magnetic field pulse 6
The frequencies such as 1 and 62 are matched with the slice SL2, and the above-described pre-pulse sequence is executed to collect the echo signal ES from the slice SL2. Further, the pre-pulse sequence is sequentially executed for the slices SL3 to SL7.

As a result, the echo signals E collected from the surface coils 5a to 5d for each of the slices SL1 to SL7.
It is assumed that the signal strength of S is as shown in FIG. In addition,
A plurality of prepulse sequences may be executed for each of the slices SL1 to SL7, and the signal intensities may be added to obtain a signal intensity as shown in FIG. This makes it possible to select with high accuracy even when there is no large difference in signal strength.

The surface coil selector 31 is provided for each surface coil 5.
Referring to the signal strength data of the echo signals obtained from each of the slices SL1 to SL7 by a to 5d, first, the maximum signal strength is obtained for each of the slices SL1 to SL7.

In this example, in the slice SL1, the signal intensity of the echo signal by the surface coil 5a becomes maximum at Em1 (FIG. 6A), and in the slice SL2, the signal intensity of the echo signal by the surface coil 5a becomes maximum at Em2. (FIG. 6B), the surface coil 5b in the slice SL3.
Signal intensity Em3 (FIG. 6 (c)), slice SL4
Then, the signal strength Em4 by the surface coil 5c (FIG. 6)
(D)), the signal intensity Em5 of the surface coil 5c in the slice SL5 (FIG. 6E), the signal intensity Em6 of the surface coil 5d in the slice SL6 (FIG. 6F), and the signal intensity of the surface coil 5d in the slice SL7. Em7
(FIG. 6 (g)) becomes the maximum. Then, first, these surface coils 5a, 5a, 5b, 5c, 5c, 5d, 5d
Are used to collect echo signals from the slices SL1 to SL7, and at least one surface coil is selected for one slice.

Next, the surface coil selecting section 31, for example,
A threshold is set for each slice at the maximum value / 2 of the signal strength for each of the slices 5a to 5d, and all surface coils exceeding this are used for data collection from that slice. These values are indicated by dashed lines in FIG. 6. By setting these threshold values, the surface coil 5b in the slice SL2, the surface coil 5b in the slice SL4, and the surface coil 5c in the slice SL6 also collect echo signals. Selected to be used for

That is, the surface coils 5a to 5d selected for each of the slices SL1 to SL7 are arranged as follows. Such a correspondence table between the selected slice and the surface coil to be used is stored in the host computer 7. Selected slice Surface coil to be used SL1 5a SL2 5a 5b SL3 5b SL4 5b 5c SL5 5c SL6 5c 5d SL7 5d

After executing the pre-pulse sequence as described above and selecting at least one surface coil to be used for each slice, the imaging pulse sequence is executed as follows.

"Imaging pulse sequence" First, the sequencer 9 connects only the surface coil 5a appropriate for the "selected slice SL1" to the receiving amplifier 23a based on the correspondence table between the selected slice and the surface coil to be used. Only the coil switching unit 29a is closed and the other coil switching units 2 are closed.
Open 9b-29d. Then, an imaging pulse sequence as shown in FIG. 5 is executed to generate an echo signal ES and perform data collection. This is obtained by adding a gradient magnetic field pulse 80 for phase encoding (FIG. 5D) to the pre-pulse sequence shown in FIG.

In the case of "selected slice SL2", only the coil switching units 29a and 29b are closed to execute the imaging pulse sequence, and in the case of "selected slice SL3", only the coil switching unit 29b is closed. Selected slice SL
4 ", only the coil switching units 29b and 29c
In the case of “selected slice SL5”, the coil switching unit 29
In the case of only “c” and “selected slice SL6”, only the coil switching units 29c and 29d are closed, and in the case of “selected slice SL7”, only the coil switching unit 29d is closed to execute the imaging pulse sequence.

When the data collection is completed, the image reconstruction device 3
3 reconstructs a tomographic image of each of the slices SL1 to SL7, but in the case of the slice SL1, one surface coil 5a
Reconstructed based on data collected from only the surface coils 5a and 5b in the case of slice SL2, and reconstructed by combining (for example, the addition method) data collected from only the two surface coils 5a and 5b, and in the case of slice SL3. One surface coil 5
b, in the case of slice SL4, two surface coils 5b,
5c, one surface coil 5 in the case of slice SL5
c, in the case of slice SL6, two surface coils 5c,
5d, one surface coil 5d in the case of slice SL7
Reconstruction is based on data from only one. The images of the reconstructed slices SL1 to SL7 are output to the display unit 35.

As described above, the pre-pulse sequence is performed in advance before the imaging pulse sequence, and an appropriate surface coil is selected for each selected slice. In the imaging sequence, signals from the surface coil having a low signal intensity are not collected. Since signals are collected only from surface coils having an intensity equal to or more than a certain value to reconstruct a tomographic image of a selected slice, SN
An image with a high ratio can be obtained. In addition, the amount of memory used is small, data processing can be performed at high speed, and throughput can be improved.

<Second Embodiment> Next, a second embodiment will be described. Since the block diagram is the same as the first embodiment shown in FIG. 1, the configuration will be described with reference to FIG. I do. The description of the configuration having the same function as that of the first embodiment is omitted.

In the first embodiment, there is a pre-pulse sequence in which no image reconstruction is performed and an imaging pulse sequence for performing image reconstruction. In this embodiment, however, there is no such distinction and the imaging pulse sequence is not used. Only (FIG. 5) is executed.

First, the sequencer 9 includes a coil switching unit 29
To control all the surface coils 5a to 5d by the receiving amplifier 2
Connect to 3a to 23d. Next, the imaging pulse sequence as shown in FIG.
Collect echo signals from d. The echo signal collected in this way is synthesized by the image reconstruction device 33, and the image of the maximum field of view (maximum field image) that can be photographed using all four surface coils 5a to 5d is displayed at a low resolution on the display unit 35. (Display means). The mouse 37 corresponding to the instruction means is operated by the operator, and instructs a desired range in the maximum visual field image displayed on the display unit 35 as a region of interest.

At this time, based on the positional relationship between the maximum visual field image and the desired region of interest and the positional relationship between the maximum visual field image and each of the surface coils 5a to 5d which are known in advance, the surface coil selecting unit 31 (surface coil) is selected. Coil selecting means) selects at least one surface coil having a positional relationship close to a desired region of interest. The surface coil selection unit 31 stores an address AD of the maximum visual field image known in advance and addresses ADC of the surface coils 5a to 5d at this address AD as shown in FIG. And the address of the region of interest (AD
R1, ADR2) to select a surface coil. When imaging a region of interest, the coil switching unit 2
9 is switched, and only the selected surface coil is connected to the receiving amplifier 23 to collect echo signals.

Next, the operation of the above apparatus will be described with reference to the schematic diagrams of FIGS. The positional relationship between the subject M and each of the surface coils 5a to 5d of the array coil 5 will be described assuming that it is as shown in FIG.

First, the sequencer 9 controls the coil switching section 29 so that all the surface coils 5a to 5d are connected to the receiving amplifier 2. For example, the sequencer 9 controls the gradient magnetic field so as to obtain a coronal image, and performs the imaging pulse. Execute the sequence. As a result, the captured low-resolution maximum field-of-view image ROI1 is displayed on the display unit 35 as shown in FIG.

The operator operates the maximum field of view image ROI1
By operating the mouse 37 while viewing the area, a region desired to be viewed at a high resolution is designated as the region of interest ROI2. For example, as shown in FIG. 8, a region of interest ROI2 surrounding the tumor T1 is indicated.
The addresses of the designated upper and lower sides of the region of interest ROI2 at the address AD of the maximum visual field image ROI1 are referred to as a first address ADR1 and a second address ADR2, respectively. The surface coil selector 31 determines whether the first address AD
The first address ADR1 is obtained from R1, the second address ADR2 and the address ADC of the surface coil (address ADC of the surface coil 5a, address ADC of the surface coil 5b, address ADC of the surface coil 5c, address ADC4 of the surface coil 5d). Since the address ADC2 of the surface coil 5b and the second address ADR2 correspond to the address ADC3 of the surface coil 5c, the region of interest RO
Surface coil 5 as a suitable coil for photographing I2
b, 5c are selected.

Then, the sequencer 9 receives the surface coils 5 b and 5 c selected by the surface coil
3 to execute an imaging pulse sequence. Then, by combining the echo signals obtained from the two surface coils 5b and 5c, the region of interest ROI2 in which the tumor T1 is drawn is output to the display unit 35.

As shown in FIG. 9, when the operator instructs the region of interest ROI3 to surround the tumor T2 in the maximum field of view image ROI1, the first / second address ADR1 / ADR2 of the region of interest ROI3 is displayed. Is the surface coil 5c
, Only one surface coil 5c is selected and imaging is performed.

As described above, the region of interest ROI2 (or ROI2)
I3) and the positional relationship between the maximum visual field image ROI1 and the maximum visual field image ROI1 and the surface coils 5a to 5
region of interest RO based on the positional relationship with
Only the surface coil close to I2 (or ROI3) is automatically selected, and the selected surface coil 5b, 5c (or 5
c) Only the echo signal is collected from the region of interest ROI2
(Or ROI3) image is reconstructed. Therefore,
Surface coils 5a, 5d (or 5a, 5a,
5b, 5d), no signal is collected, and the number of data to be processed can be reduced. In addition, the amount of memory used can be reduced, data processing can be performed at high speed, and throughput can be improved.

In the second embodiment, each of the surface coils 5a to 5d at the address of the maximum visual field image ROI1 is set.
The surface coil was selected based on the physical relationship between the physical mounting position and the region of interest.
The selection may be made in consideration of the sensitivity distributions a to 5d.

In the first and second embodiments described above, 4
The array coil 5 composed of the surface coils 5a has been described as an example, but the present invention can be applied to an array coil composed of two or more surface coils.

[0050]

As is apparent from the above description, according to the first aspect of the present invention, a pre-pulse sequence is performed before an imaging pulse sequence to select an appropriate surface coil, and an imaging sequence is selected. Does not collect signals from surface coils with low signal strength, but collects signals only from surface coils with a signal strength of a certain value or more to reconstruct an image, so that a reconstructed image with a high SN ratio is obtained. be able to. In addition, the amount of memory used is small, data processing can be performed at high speed, and throughput can be improved.

According to the second aspect of the present invention, the method of the first aspect can be suitably implemented.

According to the third aspect of the present invention, the instruction is made based on the positional relationship between the region of interest and the maximum visual field image and the positional relationship between the maximum visual field image and each surface coil which is known in advance. Only the surface coil close to the selected region of interest is automatically selected, and an echo signal is collected from only the selected surface coil to reconstruct an image of the region of interest. Therefore,
Signals from surface coils far from the region of interest are not collected, and the number of data to be processed can be reduced. In addition, the amount of memory used is small, data processing can be performed at high speed, and throughput can be improved.

Further, according to the device invention of the fourth aspect, the method invention of the third aspect can be suitably implemented.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a schematic configuration of an MR imaging apparatus according to a first embodiment.

FIG. 2 is a diagram illustrating an example of an array coil.

FIG. 3 is a diagram showing a positional relationship between an array coil and a subject.

FIG. 4 is a time chart illustrating an example of a pre-pulse sequence.

FIG. 5 is a time chart illustrating an example of an imaging pulse sequence.

FIG. 6 is a schematic diagram showing the signal strength of an echo signal obtained from each surface coil for each slice.

FIG. 7 is a diagram provided for explanation of a second embodiment.

FIG. 8 is a diagram provided for describing a process of selecting a surface coil.

FIG. 9 is a diagram for explaining a process of selecting a surface coil.

[Explanation of symbols]

 M ... subject 1 ... gradient coil 3 ... RF coil 5 ... array coil 5a to 5d ... surface coil 7 ... computer 9 ... sequencer 11 ... transmission system 13 ... reception system 29 ... coil switching unit 31 ... surface coil selection unit 33 ... Image reconstructing device 35 display unit 37 mouse SL1 to SL7 slice

Claims (4)

[Claims] 1. An MR imaging method for performing imaging based on signals from an array coil composed of a plurality of surface coils using nuclear magnetic resonance (NMR phenomenon), wherein (a) a pre-pulse sequence is executed. hand,
A step of selecting one slice in a direction orthogonal to the arrangement direction of the surface coils and collecting echo signals generated by exciting the selected slice through all the surface coils constituting the array coil; ( b) selecting at least one surface coil whose signal strength of the collected echo signal is equal to or greater than a predetermined value, and (c) executing an imaging pulse sequence for obtaining a reconstructed image. The echo signal generated by exciting the selected slice is
Collecting by using only the selected surface coil,
(D) reconstructing an image of the selected slice based on the collected echo signals. 2. An MR imaging apparatus for performing imaging based on a signal from an array coil including a plurality of surface coils by utilizing nuclear magnetic resonance (NMR phenomenon). A pulse sequence executing means for irradiating a subject placed in a static magnetic field to execute a pre-pulse sequence or an imaging pulse sequence, and an echo signal generated by operating the pulse sequence executing means, Collecting means for collecting through each of the surface coils constituting the coil, surface coil switching means for selectively switching each surface coil of the array coil to connect to the collecting means, and prior to the imaging pulse sequence Execute the pre-pulse sequence and select one slice in the direction orthogonal to the surface coil arrangement direction. Select and collect echo signals generated by exciting the selected slice through all surface coils constituting the array coil, and the signal intensity of the echo signal collected from the selected slice is equal to or more than a certain value. A surface coil selecting means for selecting at least one surface coil, and after connecting only the surface coil selected by the surface coil selecting means to the collecting means by the surface coil switching means, execute an imaging pulse sequence, Image reconstruction means for acquiring an echo signal generated by exciting the selected slice using only the surface coil, and reconstructing an image of the selected slice based on the acquired echo signal. An MR imaging apparatus comprising: 3. An MR imaging method for performing imaging based on signals from an array coil composed of a plurality of surface coils using nuclear magnetic resonance (NMR phenomenon), wherein (a) the arrangement of the surface coils Collecting echo signals from a subject along the surface through all surface coils and displaying an image of a maximum field of view (hereinafter, referred to as a maximum field image) that can be photographed by an array coil; and (b) the maximum field image Indicating a desired region of interest at
(C) selecting at least one surface coil close to the region of interest based on a positional relationship between the region of interest and the maximum visual field image and a positional relationship between the maximum visual field image and each surface coil. (D) collecting echo signals from the region of interest using only the selected surface coil, and reconstructing an image of the region of interest. 4. An MR imaging apparatus that performs imaging based on signals from an array coil composed of a plurality of surface coils by utilizing nuclear magnetic resonance (NMR phenomenon). Collecting means for collecting through each of the surface coils constituting the array coil; surface coil switching means for selectively switching each surface coil of the array coil to connect to the collecting means; Display means for collecting echo signals from the subject along the array through the collecting means and displaying an image of a maximum visual field (hereinafter, referred to as a maximum visual field image) which can be photographed by the array coil; Indicating means for indicating a desired region of interest in an image; a positional relationship between the region of interest and the maximum field-of-view image; Surface coil selecting means for selecting at least one surface coil close to the region of interest based on the positional relationship with the coil, and only the surface coil selected by the surface coil selecting means by the surface coil switching means. After connecting to the collecting means, the echo signal from the region of interest is collected using only the surface coil, image reconstruction means for reconstructing the image of the region of interest based on the collected echo signal, An MR imaging apparatus, comprising: