JP2000316830A - Magnetic resonance imaging method and magnetic resonance imaging device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To pick up images of two intersecting cross sections within a subject at high time resolution and images of an area where the two cross sections intersect at high spatial resolution. SOLUTION: A first slice is excited by application of an RF pulse 101 and a slice gradient magnetic field 201, and a phase encoding inclined magnetic field 301 and readout inclined magnetic fields 401, 402 are applied to measure a signal 501. Next, a second slice is excited by applying an RF pulse 102 and a slice gradient magnetic field 303 perpendicular to the slice gradient magnetic field 201 at the same time, and a phase encoding gradient magnetic field 203 and readout gradient magnetic fields 404, 405 are applied to measure a signal 502. Thereafter, a slice encoding gradient magnetic field 205 is applied to one of the cross sections of an intersecting area and a phase encoding gradient magnetic field 305 is applied to the other of the cross sections; a spin echo signal 503 is measured as a readout gradient magnetic field 407 is being applied. These processes are repeatedly performed, and image reconfiguration is effected for each of the echo signals 501, 502, 503 to display images of first and second slices combined with an image of the intersecting area.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic resonance imaging method and a magnetic resonance imaging apparatus (hereinafter, referred to as an MRI apparatus), and more particularly to grasping a tip position of a catheter inserted into a body for performing treatment under an image guide. The present invention relates to a technique for acquiring and displaying an image suitable for guiding a catheter to a treatment site.

[0002]

2. Description of the Related Art In recent years, it has become widespread to perform treatment by inserting a catheter or a puncture needle into a patient while observing an image called interventional radiology (IVR). The term IVR literally comes from the fact that it is performed using radiation, mainly X-ray images. The IVR emits X-rays continuously or frequently while guiding a catheter or the like to a treatment site.
Since it is necessary to display and observe a fluoroscopic image on a monitor, there has been a problem that the X-ray exposure of the patient and the X-ray of the doctor increase.

On the other hand, an MRI apparatus was initially very long in imaging time and could not be used for IVR, but various high-speed imaging methods have been remarkably developed, and in recent years, an attempt has been made to apply an MRI apparatus to IVR. ing. The treatment method under image observation using this MRI apparatus is interventional M
It is referred to as RI (hereinafter referred to as IVMR).

When a catheter is guided in a patient, the catheter is guided through a blood vessel to a treatment site. However, since the blood vessel is meandering in the body and repeats branching, the distal end of the catheter is inserted into the blood vessel. In order to proceed, it is difficult to observe only images taken from one direction. For this reason, images taken from two directions are required for IVR or IVMR, and it is desired that the tip of the catheter be imaged simultaneously in those two directions.
The closer the images taken from the two directions are in time, the better. That is, it is preferable that the time resolution of the image is large.

[0005]

There is a multi-slice imaging method in an MRI apparatus. In this method, for example, nuclear spin excitation and signal measurement are alternately performed on two slices. In this multi-slice imaging method, slice selection can be performed so that two slices intersect.

However, the excited nuclear spins require a predetermined time according to the excitation angle before returning to the steady state. Therefore, if the excitation interval between two intersecting slices is reduced, another slice is excited before the nuclear spin in the previously excited slice returns to the steady state. At this time, a difference occurs in the excitation interval between the crossing region and the non-crossing region in the two slices. That is, the excitation interval is long in the non-crossing region, and short in the crossing region.

If the excitation interval is shorter than the longitudinal relaxation time of the excited nuclear spin, the relaxation of the longitudinal magnetization becomes insufficient and the measurement signal decreases. If this phenomenon occurs in the intersection area, the image quality deteriorates in the intersection area, although a good image is originally desired.

[0008] The present invention relates to a method in which the tip of a catheter is located.
It is an object of the present invention to provide an MRI apparatus capable of displaying an intersection area of two images with good image quality.

[0009]

According to the present invention, in order to achieve the above object, a first cross section at a predetermined position in a subject is excited by a first excitation pulse to measure a first echo signal. After the measurement of the echo signal, a second cross section that intersects the first cross section at a predetermined position in the subject is excited by a second excitation pulse to measure a second echo signal, and the second echo signal is measured. Measuring the third echo signal generated by the first and second excitation pulses while considering the intersection area of the first and second cross sections as a three-dimensional area after the measurement,
After the measurement of the three echo signals is completed, an image of a first cross section and an image of the intersection area are combined and an image of the second cross section and an image of the intersection area are combined and displayed. .

According to another aspect of the present invention, a static magnetic field generating means for applying a static magnetic field to a subject, a gradient magnetic field generating means for applying a gradient magnetic field to the static magnetic field, and a nuclear magnetic resonance A means for generating a high-frequency pulse causing a phenomenon, a detection system for detecting a nuclear magnetic resonance signal generated from the subject, a means for generating an image using the detected nuclear magnetic resonance signal, and displaying the image And a controller for controlling the high-frequency pulse generating means, the gradient magnetic field generating means, the detection system, and the image generating means, wherein the control device includes the high-frequency pulse generating means. And the gradient magnetic field generating means, and sequentially select and excite two slices crossing each other to measure an echo signal from each slice. An echo signal generated from the intersection area of the two slices due to spin is measured separately from the echo signals from the two preceding slices, and the two slice images are generated by the image generating means using the three echo signals. Then, the generated two slice images are displayed on the image display means.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 4 is a block diagram showing the overall configuration of the MRI apparatus for implementing the present invention. In FIG. 4, 2 is a static magnetic field generating magnet, 8 is a central processing unit (hereinafter referred to as CPU), 3 is a gradient magnetic field generating system, 4 is a sequencer, 5 is a transmitting system, 6 is a receiving system, and 7 is signal processing. System.

The static magnetic field generating magnet 2 applies a strong and uniform static magnetic field in a predetermined direction, for example, in the body axis direction of the subject 1 or in a direction orthogonal to the body axis, in a predetermined area of the space in which the subject 1 can be accommodated. A permanent magnet or a superconducting magnet-like magnet is arranged so as to surround the space.

The transmitting system 5 includes a high-frequency oscillator (synthesizer) 11, a modulator 12, a high-frequency amplifier 13, and a transmitting high-frequency coil 14a. The high-frequency pulse output from the synthesizer 11 is instructed by the CPU 8 and the sequencer 4. The signal is amplitude-modulated by the modulator 12, the modulated signal is amplified by the high-frequency amplifier 13, and the amplified high-frequency pulse is supplied to the transmission high-frequency coil 14 a disposed close to the subject 1. The object 1 is irradiated with an electromagnetic wave from the coil 14a.

The gradient magnetic field generating system 3 has three orthogonal axes,
That is, the gradient magnetic field coil 9 generates gradient magnetic fields in three directions of X, Y, and Z, and the gradient magnetic field power supply 10 drives the gradient magnetic field coils in each direction. The gradient magnetic field power supply is driven, and the generated gradient magnetic field is superimposed on the static magnetic field to generate a gradient magnetic field required for imaging.

The receiving system 6 includes a receiving high-frequency coil 14b.
, An amplifier 15, a quadrature detector 16, and an A / D converter 17, and a behavior signal of a nuclear spin generated from within the subject by an electromagnetic wave irradiated from the high-frequency coil 14 a of the transmission system 5 (electromagnetic wave, NMR A signal).
The detection signal is detected by a receiving high-frequency coil 14b disposed in close proximity to the amplifier, and the detection signal is amplified by an amplifier 15 and then input to a quadrature phase detector 16, where the quadrature detection is performed based on the output of the synthesizer 11. And a sin component,
The signal is separated into two signals of the cos component, input to the A / D converter 17, and is sampled by the A / D converter 17 based on the instructions of the CPU 8 and the sequencer 4, converted into a digital signal, and subjected to signal processing. Output to the system 7.

The signal processing system 7 includes a CPU 8, a recording device such as a magnetic disk device 18 and a magnetic tape device 19, and a display device 20 such as a CRT. On the other hand, processing such as Fourier transform, correction coefficient calculation, and image reconstruction is performed, and an image showing the nuclear density distribution in the slice plane of the subject 1, for example, a hydrogen nucleus (proton) density distribution image, and nuclear spin relaxation time Is displayed on the display device 20, and control software such as a pulse sequence and image data are recorded on the recording device. The MRI apparatus further includes an operation console (not shown), in which a keyboard (not shown) is arranged.

Next, a method of imaging a subject and a method of displaying an image according to the present invention will be described. FIG. 2 is a view for explaining the concept of the photographing method of the present invention. In FIG. 2, reference numeral 100 denotes a subject, which is shown as a rectangular parallelepiped in FIG. 1, but is actually a living body. Reference numeral 110 denotes a first imaging slice (hereinafter, referred to as a first slice), and 120 denotes a second imaging slice (hereinafter, referred to as a first slice).
Since these are set so as to intersect with each other, an intersection area 130 is generated at the center. M
In the RI device, a predetermined time (referred to as relaxation time) is required until the excited nuclear spin returns to a steady state.
When the slice 110 and the second slice 120 crossing it are excited at a time interval shorter than the relaxation time, the crossing region 13 is excited.
After the nuclear spin in 0 is excited for imaging the first slice 110, it will be excited for imaging the second slice 120 before returning to the steady state. For this reason, the nuclear spins in the intersection region 130 are in an over-excited state, and the signal intensity therefrom decreases as compared with the signal from the region where the intersection does not intersect.

When the signal strength from the intersection area is weak,
The density of the image of the intersection region 130 located at the center of the image of the first slice 110 and the image of the intersection region 130 located at the center of the image of the second slice 120 are reduced.
Diagnosis is difficult. The present invention solves the problem by separately measuring the signal of the intersection region 130 so that the intersection region 130 is not affected by the excitation for imaging the first slice 110 and the second slice 120. More specifically, signal measurement is performed by regarding the intersection area 130 as a three-dimensional area, and measurement data from the three-dimensional area is used as an image, which is combined with an image of the first slice 110 and the second slice 120 for use. Features.

Hereinafter, this detailed description will be described with reference to the pulse sequence diagram of FIG. FIG. 1 is basically obtained by adding three-dimensional measurement of an intersection area to a two-slice imaging method using a gradient echo method. In FIG. 1, RF
Is a high-frequency pulse that excites nuclear spins in the subject
RF pulse), the excitation angle of nuclear spin, and the frequency of the RF pulse. Gs1
Gs2 is the application timing and the application amount of the gradient magnetic field applied in the first direction of the three orthogonal axes described above, and Gs2 is the application timing of the gradient magnetic field in the second direction orthogonal to the gradient magnetic field Gs1 and its application. Gs3 indicates the application timing and the application amount of the gradient magnetic field in the third direction orthogonal to each of Gs1 and Gs2. In this example, Gs1 and Gs2 are used for slice selection and phase encoding, respectively, and Gs3 is used for lead-out (frequency encoding).
S indicates the appearance of the NMR signal to be measured. Further, τ shown in the lower part of the figure is the NMR generated from the intersection region 130.
A time for explaining the signal and TR indicates a repetition time of the sequence.

Next, a photographing method will be described with reference to FIGS. At the start of imaging, the operator sets two crossed slices 110 and 120 shown in FIG. The setting of the slices 110 and 120 is performed by selecting the frequency f of the RF pulse and the application direction of the gradient coil in the pulse sequence diagram 1. In the present embodiment, an example is shown in which the two slices 110 and 120 are set orthogonally. However, the selection of the first slice 110 is performed by setting the frequency of the RF pulse to f1 (the frequency band corresponds to the thickness of the first slice). The gradient magnetic field direction for slice selection to be used is set to the Gs1 direction, and the frequency of the RF pulse is set to f2 (the frequency band corresponds to the thickness of the second slice) for selection of the second slice 120;
The direction of the gradient magnetic field for slice selection to be used is G perpendicular to Gs1.
s2 direction. Further, the excitation angle α0 of nuclear spins of the first slice 110 and the second slice 120 can be set arbitrarily. However, an appropriate angle can be set depending on the time resolution of the image by shortening the repetition time TR of the pulse sequence. It is good to choose. For example, when TR is set to 20 to 30 ms, α0 is set to about 20 °.

The pulse sequence of FIG. 1 set as described above will be described with the passage of time. When the pulse sequence is started, first, the sequencer 4 sends the signal to the transmission system 5.
An RF pulse 101 having a frequency f1 and a frequency band corresponding to the thickness of the first slice 110 is applied to the subject from the transmitting high-frequency coil 14a and tilted in the Gs1 direction with respect to the gradient magnetic field power supply 10. Magnetic field 201
Is selected, and control is performed so that current is supplied to the gradient coil 9. . Then, when the RF pulse 101 having the frequency f1 is applied in a state where the gradient magnetic field 201 is applied in the Gs1 direction,
The nuclear spin in the first slice 110 in the subject is excited. The excitation angle of the nuclear spins excited at this time is 20 ° in total. A total of 20 ° means that the excitation angles are not the same for all nuclear spins, and some include those smaller than 20 ° and those excited at 90 ° larger than 20 °. Is 20 °. Then, the polarity of the gradient magnetic field Gs1 is reversed with respect to 201, and the gradient magnetic field 202 having an application amount of の of the application amount of 201 is applied. Thereby, the phases of the nuclear spins in the slice direction are adjusted.

After that, a predetermined amount of the gradient magnetic field 301 in the Gs2 direction is applied, and phase information corresponding to the position is given to the excited nuclear spins in the first slice 110. Further, a predetermined amount of gradient magnetic field 401 is applied in the Gs3 direction (readout direction) to perform phase diffusion of the excited nuclear spins in the Gs3 direction.

Next, the polarity of the gradient magnetic field in the Gs3 direction is reversed. Then, all the nuclear spins in the first slice 110 diffused by the application of Gs3402 are phased (referred to as rephase), and NMR signals are observed.
When the gradient magnetic field Gs3402 is applied, the sequencer 4 operates the reception system 6 and the reception high-frequency coil 14b
Then, the induced current due to the rotation of the nuclear spin is detected as an NMR signal 501. The detected NMR signal has a peak value when the applied amount of Gs3402 becomes equal to the applied amount of GS3401 after the start of application of Gs3402. Readout gradient magnetic field Gs340
In the case of No. 2, the application is completed at the time when the amount of application becomes twice the amount of Gs3401. The above procedure is widely known as an NMR signal measurement method generally using a gradient echo method.

When the measurement of the NMR signal 501 of the first slice 110 is completed, the preparation for the measurement of the NMR signal of the second slice is performed in the sequence as follows. The polarity of the phase encoding gradient magnetic field Gs2 is inverted, and the same amount as the applied amount of Gs2301 is applied. Thus, the first slice 1
The phase encoding amount applied to the nuclear spins in 10 is canceled (meaning that the phase encoding amount is returned to zero). That is, the phase is adjusted in the Gs2 direction. After the end of the measurement period of the NMR signal, the gradient magnetic field in the Gs3 direction is raised to a level having a considerable difference from Gs3402 and applied for a predetermined time. Thereby, the first slice 11
The phase diffusion of the nuclear spin in 0 in the Gs3 direction is performed. This G
The application of s3403 is performed so that a signal that causes an artifact due to the excitation spin of the first slice 110 is not measured during the measurement of the second slice.

Next, excitation for imaging the second slice 120 is performed. The second slice 120 is the first slice 11
Since it is orthogonal to 0, a gradient magnetic field Gs2 orthogonal to the gradient magnetic field Gs1 is used as the slice selection gradient magnetic field. The excitation of the second slice 120 is performed by applying a frequency f according to the position and thickness of the second slice 120 under the application of the gradient magnetic field Gs2303.
This is performed by applying the RF pulse 102 having the frequency band 2 and the frequency band, and the application timing is after the elapse of τ time from the excitation of the first slice 110. RF pulse 1
In 02, the nuclear spin in the second slice 120 may be tilted by an arbitrary angle, but in this embodiment, the first slice 1
The same 20 ° pulse as the 10 excitation is applied. RF
The pulse 102 is applied as a 20 ° RF pulse, which is also total. Then, this RF pulse 10
2 is the first slice 110 crossing the second slice 120
It also acts on the excited nuclear spins within, causing some 180 ° excitation of the nuclear spins. This embodiment utilizes this phenomenon.

When the excitation of nuclear spins in the second slice 120 is completed, the polarity of the gradient magnetic field Gs2 is inverted to Gs230.
Gs2304 is applied in an amount of 印 加 of the applied amount of 3
The phase of the nuclear spin is adjusted in the thickness direction of the slice 120. Then, a predetermined amount of the phase encoding gradient magnetic field Gs1203 of the second slice 120 is applied, and a predetermined amount of the readout direction gradient magnetic field Gs3 404 is applied. This Gs3404 performs phase diffusion of the excited nuclear spins in the readout direction. After the application of Gs3404 is completed, the polarity is inverted and applied as Gs3405.
The measurement of the R signal 502 is performed. This NMR signal 502
Is a gradient echo method measurement similarly to the measurement of the NMR signal 501 of the first slice 110, and the measured NMR signal 502 is obtained from the second slice including the intersection region of the first slice 110 and the second slice 120. NMR signal, and the signal from the intersection area and the second signal excluding the intersection area
The signal is slightly different in intensity from the signal from the slice.

Then, by applying the RF pulse 102, N
After the completion of the measurement of the MR signal, Gs1204 having the polarity of the phase encoding gradient magnetic field Gs1 inverted is applied to cancel the phase encoding of the excited nuclear spin. After the measurement of the NMR signal 502 is completed, the gradient magnetic field Gs3 is further increased by gradient magnetic fields Gs3406 and Gs3.
While the application is continued as 407, when the Gs3406 is applied, the gradient magnetic field Gs1205 and the gradient magnetic field Gs2305 are simultaneously applied. Of these gradient fields, Gs340
Numeral 6 has the same function as Gs3403, and Gs3407 is for generating an NMR signal (this is a spin echo signal) 503. Therefore, when the application of the gradient magnetic field Gs3 is viewed with time, [Gs3 (401) + Gs3 (402)
+ Gs3 (403)] and [Gs3 (404) + Gs3 (40
5) + Gs3 (406) + Gs3 (407) / 2] must be applied. The gradient magnetic field Gs1205 is for phase encoding applied to the spin echo signal 503 generated from the intersection area 130, and the gradient magnetic field Gs2305 is for applying slice encoding to nuclear spins in the intersection area 130. Note that the reason why the NMR signal 503 is generated as a spin echo signal is that the first slice 110
The peak of the spin echo signal 503 is due to the fact that there is a nuclear spin that is excited 90 ° by the excitation RF pulse 101 of the second slice 120 and that the excitation RF pulse 102 of the second slice 120 includes exciting the nuclear spin further 180 °. The value occurs at a time after a lapse of 2τ hours from the center of the application period of the RF pulse 101.

When the measurement of the spin echo signal 503 ends, the application of the readout gradient magnetic field Gs3407 ends. By applying these gradient magnetic fields, the intersection region between the first slice 110 and the second slice 120 is three-dimensionally measured.

The NMR signals 501, 502, and 503 measured by executing the above pulse sequence
Are stored in separate memories, each having a storage address commonly referred to as k-space.

Next, after the application of the gradient magnetic field Gs3407,
After a predetermined waiting time, that is, the RF pulse 101
The RF pulse 101 is applied again after the elapse of the TR time from the application of, and the above pulse sequence is repeatedly executed. At the time of this repetition, the phase encoding gradient magnetic field of the first slice 110 and the gradient magnetic field that cancels it out, and the phase encoding gradient magnetic field of the second slice 120 and the gradient magnetic field that cancels it out have stepwise intensity every time the pulse sequence is repeated. And the intersection area 13
The 0 phase encoding gradient magnetic field and the slice encoding gradient magnetic field change both gradient magnetic fields in such a manner as to change the slice encoding every step in each phase encoding step.

The intensity of the phase encoding gradient magnetic field of the first slice 110 and the second slice 120 is set according to the size of the field of view, and the number of steps is determined according to the desired spatial resolution and temporal resolution. Is set. For example, the phase encoding gradient magnetic field is 6
About 4,128,256 is good. Also, the intensity of the readout gradient magnetic field is set according to the size of the field of view, and the sampling number for signal measurement is set as 64, 128, 256 according to the desired spatial resolution.

Next, the setting of the phase encoding gradient magnetic field and the slice encoding gradient magnetic field for the measurement of the intersection area 130 will be described. The intersection region 130 is a columnar body having the slice thickness of the first slice 110 and the slice thickness of the second slice 120 as sides of the cross section and the length in the readout direction of the two slices. The three-dimensional measurement is performed by setting the phase encoding direction of the first slice 110 to the slice encoding direction and setting the phase encoding direction of the second slice 120 to the same phase encoding direction. Since the pulse sequence shown in FIG. 1 is repeatedly performed only for the phase encoding step of the first slice 110 or the second slice 120, the product of the number of phase encoding steps and the number of slice encoding steps of the intersection area 130 is set to be equal to that. I do. For example, if the phase encode steps of the two slices 110 and 120 are 64, the product of the number of phase encode steps and the number of slice encode steps of the intersection area 130 is 64, and if the phase encode step is 128, the product is 12
Set to 8. For example, when the product of the number of phase encode steps and the number of slice encode steps in the intersection area 130 is 64, the number of phase encode steps is set to 8, and the number of slice encode steps is set to 8. In this case, when the slice thickness of the first slice 110 and the second slice 120 is, for example, 10 mm, the intersection region 130
Has a spatial resolution of 1.25 mm (10 /
8 mm). Therefore, the field of view (FOV) of the first slice 110 and the second slice 120 is, for example, 16
When the image resolution is set to 0 × 160 (mm) and the number of pixels for the image measurement is set to 64 × 64, the spatial resolution of the non-intersecting area is about 2.5 × 2.5 (mm). This means that the spatial resolution in the encoding direction has been doubled.

To improve the spatial resolution of the intersection area 130 also in the readout direction, the gradient magnetic field Gs3 in the readout direction is used.
It is necessary to increase the number of samplings without changing the intensity of. For example, when the sampling number of the first slice 110 and the second slice 120 in the reading direction is 64, the sampling number is 128 in the measurement of the intersection area 130. Thereby, for example, the first slice 1
10 and the FOV in the reading direction of the second slice 120 is 1
When the distance is 60 mm, the spatial resolution of the intersection area 130 in the reading direction is 1.25 m in the phase encoding direction.
It can be the same value as m. The intersection area 130
Various combinations can be considered for the combination of the sampling number and the phase encoding step number for the measurement of the measurement. However, if the spatial resolution is excessively increased, the S / N is reduced. Therefore, the spatial resolution of the intersection area is about twice that of the non-intersection area. Although it is considered desirable to suppress this, it is not limited to the case where imaging is performed with an emphasis on lowering the spatial resolution of the non-intersecting region and increasing the temporal resolution of the image.

Next, a method for imaging the above measurement data will be described. First, the first slice 110 and the second slice 110
For the slice 120, the measurement data stored in each memory is subjected to a two-dimensional Fourier transform, and an image of each slice is reconstructed. This is known as an image reconstructing method in an ordinary MRI apparatus, and a detailed description thereof will be omitted. These images are temporarily stored for synthesis with the image of the intersection area 130.

Next, the imaging of the intersection area 130 will be described. Since the measurement data of the intersection area 130 is three-dimensional measurement data, it is necessary to use these as images along the first slice 110 and the second slice 120. In order to image the measurement data of the intersection area 130 along the first slice 110, it is necessary to convert three-dimensional data into two-dimensional data and then perform two-dimensional Fourier transform. As a method of converting three-dimensional data into two-dimensional data, (1) simply integrate (in absolute value or complex number) three-dimensional data in the slice thickness direction of the first slice 110;
(2) Average the three-dimensional data in the slice thickness direction of the first slice. (3) MIP (Maximum In)
(tensity Projection: maximum intensity projection)
Various methods such as performing processing can be adopted.
By performing the two-dimensional Fourier transform on the measurement data of the two-dimensional intersection area 130 by such a method, the intersection area 130 becomes an image along the first slice 110.
Then, this image is temporarily stored.

In the same manner as described above, the measurement data of the intersection area 130 is divided into two in the slice thickness direction of the second slice 120.
The image is reconstructed in a similar manner. This image is also temporarily stored.

The four images thus obtained are combined as follows and displayed on the display device 28. That is, first, the image of the first slice 110 and the intersection area 13
The images along the first slice 110 of 0 are combined to form and display an image as shown in FIG. Next, the image of the second slice 120 and the intersection area 1 along the second slice 120
30 composite images are displayed. Such display processing is sequentially performed every time the imaging is completed. The images can be combined by a method of superimposing or adding an image of the intersection area to the slice image and displaying the image, or a method of fitting the image of the intersection area and displaying the slice image. Note that it is also possible to arrange two combined images on the screen of the display so that they can be observed simultaneously by using a known technique.

[0038]

As described above, according to the present invention, two intersecting cross sections in a subject can be displayed with a high temporal resolution and the intersection region can be displayed with a high spatial resolution, as compared with the prior art. Since it is possible to display an image while maintaining the same time resolution as the two cross sections having and crossing, in treatment under image observation using a catheter or a puncture needle,
By imaging the tip of the catheter or the puncture needle in the subject in the intersection area, it is possible to clearly display them from two directions.

[Brief description of the drawings]

FIG. 1 is a pulse sequence diagram of the present invention.

FIG. 2 is a view showing the concept of image formation on two cross sections of the present invention.

FIG. 3 is a diagram illustrating characteristics of an image obtained by the present invention.

FIG. 4 is a block diagram showing a configuration of an MRI apparatus implementing the present invention.

[Description of Signs] 101 to 103 RF pulse 110 first slice 120 second slice 130 crossing area 201 to 205 gradient magnetic field in first direction 301 to 305 gradient magnetic field 401 in second direction 401 to 407 ... Readout gradient magnetic field 501, 502 ... Gradient echo signal 503 ... Spin echo signal

Claims (2)

[Claims] 1. A first excitation pulse excites a first cross section at a predetermined position in a subject to measure a first echo signal. After the measurement of the echo signal, the second excitation pulse measures the first echo signal. A second cross section that intersects the first cross section at a predetermined position in the inside is excited to measure a second echo signal, and after the measurement of the second echo signal, an intersection area between the first and second cross sections is measured. A third echo signal generated by the first and second excitation pulses is measured as a three-dimensional area, and
After the measurement of the three echo signals is completed, an image of a first cross section and an image of the intersection area are combined and an image of the second cross section and an image of the intersection area are combined and displayed. Magnetic resonance imaging method. 2. A static magnetic field generating means for applying a static magnetic field to a subject, a gradient magnetic field generating means for applying a gradient magnetic field to the static magnetic field, and a means for generating a high-frequency pulse causing a nuclear magnetic resonance phenomenon to the subject. A detection system for detecting a nuclear magnetic resonance signal generated from the subject, a unit for generating an image using the detected nuclear magnetic resonance signal, a unit for displaying the image, the high-frequency pulse generating unit, In a magnetic resonance imaging apparatus having a gradient magnetic field generating means, a control device for controlling the detection system and the image generating means,
The control device controls the high-frequency pulse generating means and the gradient magnetic field generating means, sequentially and selectively excites two slices crossing each other, measures an echo signal from each slice, and excites the two slices. Measuring the echo signal originating from the intersection region of the two slices separately from the echo signal from the two slices,
A magnetic resonance imaging apparatus, wherein the two slice images are generated by the image generation unit using the three echo signals, and the generated two slice images are displayed on the image display unit.