JP2003319918A - Mri system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve imaging efficiency by performing the positioning of MRI in a short period of time in real time photographing on purpose of the positioning of regular photographing of the MRI. <P>SOLUTION: The MRI system performs first photographing at a position set by an operator and second photographing based on photographing positional information of the first image. When the photographing position of the second image has to be changed, the MRI system repeats the first image photographing and image photographing. The MRI system has an image storing means for storing the first image and automatically displays the first image stored in the image storing means as the initial first image displayed when shifting from photographing of the second image to that of the first image. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an MRI apparatus for imaging the inside of a subject by utilizing the magnetic resonance phenomenon of the subject, and in particular, it is easy to set the position of an image cross section for main imaging.
I apparatus (magnetic resonance imaging apparatus)

[0002]

2. Description of the Related Art A magnetic resonance imaging method excites a nuclear spin of a subject tissue placed in a static magnetic field with a high-frequency signal having the Larmor frequency, and from a magnetic resonance signal generated by the excitation. This is an image diagnostic method for reconstructing an image.

The MRI apparatus is an image diagnostic apparatus utilizing the nuclear magnetic resonance phenomenon, and it is possible to obtain a lot of diagnostic information such as biochemical information and functional diagnostic information as well as anatomical diagnostic information. It has become indispensable in the field of diagnosis.

When an image is taken by the MRI apparatus, it is important to set the imaging section. Originally used for clinical diagnosis
Since high resolution is required for images (hereinafter referred to as main captured images and the method of capturing this image is referred to as main captured images), it takes time to collect and reconstruct image data. However, it was difficult to find the optimum image section. Therefore, conventionally, a method has been adopted in which a shooting mode of a real-time shot image excellent in real-time property is used at the sacrifice of resolution, and the optimum real-shooting position and tilt in the main shooting are set by the real-time image shooting. That is, for example, a sagittal plane and an axial plane of a subject are imaged by using a pulse sequence that can be displayed in real time in order to find an optimum imaging cross section in a three-dimensional subject space, and the subject is combined from these two images. A method of estimating the three-dimensional information in the inside and setting the cross section of the main imaging (for example, Japanese Patent Application No. 11-299453) has been adopted.

[0005]

However, even when the main photographing is performed on the optimum cross section set in the real-time photographed image as described above, the main photographing on a cross section different from the set cross section is required. There are cases. For example, as a result of detailed observation on a high-resolution main-photographed image obtained by main-photographing, it is necessary to photograph another cross-section adjacent to a preset cross-section. In such a case, in the conventional MRI apparatus, the real-time imaging method operates independently of the main imaging. Therefore, if the shooting cross section was changed during the main shooting as described above, the real-time shooting mode had to set the shooting position and so on again from the first stage, which required a lot of shooting time. . In particular, in the case of obtaining a plurality of main imaged images at different parts of the same subject, real-time imaging at each part had to be repeated from the beginning to set the position of the optimum image cross section. . Therefore, it took a lot of time to complete the collection of all the main shot images.

The present invention has been made in order to solve the above problems in the conventional method, and the purpose thereof is to provide an MRI capable of positioning a main photographed image in a short time.
To provide a device.

[0007]

In order to solve the above problems, in the first invention of the present invention, the first image is photographed at a plurality of positions set by the operator, and the photographing position information of this image is taken. In the MRI apparatus for performing the second image capturing using the second image capturing device, a position information storage unit that stores the image capturing position information of the last acquired image of the plurality of first images;
If it is instructed to change the shooting position of the second image, the shooting is switched from the shooting of the second image to the shooting of the first image, and shooting for obtaining the changed shooting position information of the second image is performed. A position correction unit is provided, and the shooting position correction unit obtains the last acquired first image corresponding to the shooting position information stored in the position information storage unit as an initial image at the time of shifting to the shooting of the first image. There is provided an MRI apparatus including a display unit for displaying one image.

According to the second aspect of the invention, the first image is photographed at a plurality of positions set by the operator, and the resolution is higher than that of the first image depending on the photographing position of the first image. In the MRI apparatus for photographing the second image, a display device for displaying the photographed first image, position correction means for correcting the photographing position of the first image displayed on the display device, and A position information storage unit capable of storing a plurality of pieces of shooting position information of the first image corrected by the unit; and when the shooting of the second image is instructed, the position information storage unit stores the position information storage unit. There is provided an MRI apparatus characterized by collectively performing a plurality of second image capturing operations based on a plurality of image capturing position information. Therefore, according to the present invention, it is possible to set the optimum position in a short time in the positioning operation of the main captured image, and it is possible to improve the photographing efficiency.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION (First Embodiment) A first embodiment of the present invention will be described below. 1 is a block diagram showing a schematic configuration of the entire MRI apparatus according to the first embodiment of the present invention, and FIG. 2 is a detailed block diagram of the high speed operation / storage unit 5 in FIG.

This MRI apparatus comprises a static magnetic field generating section 1 and a gradient magnetic field generating section 2 for generating a magnetic field, a transmitting / receiving section 3 for transmitting / receiving an RF pulse signal, and a high speed calculation / storage section 5 for reconstructing and storing an image. A bed 8, an input unit 22 and a display unit 21, and a control unit 4 that controls the entire unit.

The static magnetic field generator 1 includes a main magnet 13 which is, for example, a superconducting magnet, and forms a strong static magnetic field around the subject 11. Further, the static magnetic field generator 1 has a helium cooler 9
And a cooling system control circuit 10 for controlling this.

The gradient magnetic field generator 2 has X and Y orthogonal to each other.
And a gradient magnetic field coil 14 in the Z-axis direction and a gradient magnetic field power supply 25 for supplying a current to this coil. The gradient magnetic field signal is supplied to the gradient magnetic field power supply 25 by the sequence control circuit 24 of the control unit 4, and the space in which the subject 11 is placed is encoded. That is, by controlling the pulse current supplied from the gradient magnetic field power supply 25 to the X-, Y-, and Z-axis gradient magnetic field coils 14 based on this signal,
The gradient magnetic fields in the X-, Y-, and Z-axis directions are combined, and the slice-direction gradient magnetic field Gs, the phase-encoding-direction gradient magnetic field Ge, and the frequency-encoding-direction gradient magnetic field Gr that are orthogonal to each other can be set arbitrarily. The gradient magnetic field in each direction is superimposed on the static magnetic field and applied to the subject 11.

The transmitter / receiver 3 houses an irradiation coil 15 for irradiating the subject 11 with RF pulses and a receiving coil 16 for receiving and detecting MR signals, and a transmitter 17 connected to these coils. And a receiver 18. However, the irradiation coil 15 and the reception coil 16 are often separated as shown in FIG.

The transmitter 17 is a sequence control circuit 2 described later.
Controlled by 4. The irradiation coil 15 is driven by the RF pulse current having the same magnetic resonance frequency as that determined by the static magnetic field intensity of the main magnet 13 and modulated by the selective excitation waveform, and the subject 11 is irradiated with the RF pulse.
The receiver 18 performs A / D conversion after performing signal processing such as intermediate frequency conversion, phase detection, and filtering on the signal received as the MR signal by the reception coil 16.

The control unit 4 comprises a main control circuit 23 and a sequence control circuit 24. The main control circuit 23 has a function of controlling the entire apparatus as a whole, and in particular, the sequence control circuit 24 has information on the pulse sequence (for example, the intensity of the pulse current applied to the gradient magnetic field coil 14 and the irradiation coil 15 and the application thereof). It has an important function to send information about time, application timing, etc.). When setting the optimum position of the main shot image, the position information of the real-time shot image used together is converted into the corresponding gradient magnetic field information to give a command to the sequence control circuit 24.

The sequence control circuit 24 has a CPU and a memory, stores the pulse sequence information sent from the main control circuit 23, and controls the gradient magnetic field power supply 25, the transmitter 17, and the receiver 18 according to this information. To do.

The high speed operation / storage unit 5 includes a high speed operation circuit 19 and a storage circuit 20. The MR signal output from the receiver 18 is input to the high-speed arithmetic circuit 19 via the sequence control circuit 24, and the MR signal is stored on the frequency space data memory 31.
The signals are arranged, two-dimensional Fourier transform is performed, and reconstructed into image data (MR image) in real space.

The memory circuit 20 is a frequency space data memory 3
1, a reconstructed image memory 32, and a photographing position information memory 3
3, a real-time photographed image memory 34 and a main photographed image memory 37. The frequency space data memory 31 is a memory circuit for arranging the MR signals sent from the receiver 18 as described above, and the reconstructed image memory 32 is obtained by performing image reconstruction using the original data. It is a storage circuit for storing the acquired MR image.
On the other hand, the photographing position information memory 33 is a storage circuit for storing information on the optimum photographing position at the time of the main photographing obtained by the real-time photographing, and the stored position information is sent to the main control circuit 23 prior to the main photographing and pulsed. Sequence conditions are set.

The real-time photographed image memory 34 is a storage circuit for storing an image obtained by real-time photographing. For storing current image memories 35-1 to 35-3 in which three images orthogonal to each other are stored and a reference image for selectively displaying one of these images and resetting the photographing position. , Reference image memory 3
It is composed of 6. The main-photographed image memory 37 is a memory for storing an image obtained by main-photographing.

The bed 8 can move the subject 11 in the body axis direction together with the tabletop, and has a structure that can be inserted into the opening of the main magnet 13.

The input section 22 is equipped with various switches, a keyboard, a display panel, a mouse, etc. on the operation desk, and the operator gives various conditions for photographing, the start of inspection, the movement of the mechanism section, and the like. These control signals are sent to each unit via the main control circuit 23. On the other hand, the mouse is used as an input device for interactively operating the display on the monitor of the display unit 21. The display unit 21 is composed of a monitor and displays a real-time captured image and a main captured image.

In the present embodiment, prior to the main photographing of the MRI image, simple preliminary photographing (real-time photographing) is performed in order to know the clinically most effective image cross section. This real-time imaging is inferior in resolution because the number of pixels of the image is smaller than that in the main imaging, but it takes less time to collect MR data and reconstruct an image. Therefore, almost real-time image display is possible.

The operation of the first embodiment will be described below with reference to FIGS. FIG. 3 shows a flowchart of the photographing procedure in the first embodiment of the present invention.

First, the operator (doctor or inspection technician) of the apparatus sets the real-time imaging mode to the input unit 2 of the apparatus.
2 is selected (step S1). Next, the light of a light projector (not shown) is applied to the position of the organ to be diagnosed, and the position of an axial image, which is a reference image captured first, for example, perpendicular to the body axis is set (step S2). Note that the reference image means a real-time captured image corresponding to a captured image for main shooting, and in real-time shooting, two images orthogonal to the reference image are continuously captured in addition to the reference image. For example, in the initial shooting, a sagittal image (longitudinal section image seen from the side) and a coronal image (longitudinal section image seen from the front) are sequentially taken in addition to the axial image serving as the reference image.

At this time, selection of a pulse sequence and a display screen at the time of real-time photographing is also performed in the input unit 22, and the pulse sequence is generally fiel capable of high-speed photographing.
The d-echo method is applied.

When the operator inputs a shooting start command from the input unit 22 following the setting of the shooting conditions, the position information of the reference image (axial image) set in step S2 is sent to the main control circuit 23. And is stored in the photographing position information memory 33. Further, a control signal for forming this reference image is transmitted from the main control circuit 23 to the sequence control circuit 24.

Further, according to this control signal, a pulse sequence control signal is sent from the sequence control circuit 24 to the gradient magnetic field power supply 25, the transmitter 17 and the receiver 18. Next, the pulse current supplied to the three gradient magnetic field coils 14 according to the pulse sequence control signal is set by the gradient magnetic field power supply 25, and the slice, the phase encode,
The gradient magnetic field strength in each direction of reading is set. Similarly, the transmitter 17 also sets the frequency and phase of the RF pulse supplied to the irradiation coil 15.

Next, the sequence control circuit 24 of the control unit 4
The three gradient magnetic field power supplies 25 constituting the gradient magnetic field generator 2 are driven by the control signal of the
Real-time image capturing is started (step S
3). At this time, a pulse current for capturing an axial image set as the first reference image of the subject 11 is supplied from the gradient magnetic field power supply 25 to the gradient magnetic field coil 14.
On the other hand, under the control of the sequence control circuit 24, the transmitting / receiving unit 3
The RF pulse current is supplied to the irradiation coil 15 from the transmitter 17.

This RF pulse current has the same frequency as the magnetic resonance frequency determined by the strength of the static magnetic field of the main magnet 13 and is modulated by the selective excitation waveform. RF in coil 15
The subject 11 is irradiated with the RF pulse by supplying the pulse current, and the echo signal generated in the body of the subject 11 by the irradiation of the RF pulse is received as the MR signal by the receiving coil 16 of the transceiver 3. .

The MR signal is subjected to signal processing such as intermediate frequency conversion, phase detection and filtering in the receiver 18 and then A / D converted. Further, in the frequency space data memory 31 in the storage circuit 20, the MR space signal It is saved as raw data.

An image of the MR signal arranged in the frequency space is reconstructed by a two-dimensional Fourier transform in the high speed operation / storage unit 5, and this image data is temporarily stored in a reconstructed image memory 32 in the storage circuit 20. And the current image memory 35-1 of the real-time captured image memory 34
Stored in.

Subsequently, the gradient magnetic field for capturing the coronal image and the sagittal image orthogonal to the axial image is generated based on the sequence control signal from the sequence control circuit 24. And an RF pulse is formed at the transmitter 17. The MR data obtained at this time is subjected to image reconstruction in the high-speed calculation / storage section 5, and this image data is passed through the reconstructed image memory 32 in the storage circuit 20 to the current image memory 35-of the real-time captured image memory 34. 2 and the current image memory 35-3.

If the image pixels of the real-time photographed image are 64 × 64, the display speed of the real-time photographed image photographed by the field-echo method is about one per second. Therefore, the time required for real-time shooting of three images orthogonal to each other is about 3 seconds. The three real-time captured images obtained in this way are displayed on the display 21 via the main control circuit 23 (step S4).

FIG. 4 shows an example of a method of displaying a real-time photographed image on the display unit 21. The display area on the monitor of the display unit 21 is divided into four areas. The upper left area is the reference image area 41, and the upper right area and the lower area are the current image areas 42 to 4.
It is 4. The three real-time captured images are first displayed in the current image area. For example, a coronal image is displayed in the upper right area, an axial image that is a reference image is displayed in the lower left area, and a sagittal image is displayed in the lower right area. When changing the position or angle of the reference image, the image most suitable for the setting is copied to the reference image area by the mouse of the input unit 22. For example, current image memory 3
By copying the data 5-3 to the reference image memory 36, the sagittal image of the subject 11 displayed in the lower right area is displayed in the reference image area as shown in FIG. Further, a marker 1 (axial image position in the initial photographing) for designating a position change in a direction substantially perpendicular to the body axis and a marker 2 (coronal image position in the initial photographing) for designating a position change in the body axis direction are provided. Is displayed.

The operator makes new settings for the real-time photographed image with reference to these three images. For example, when shifting the reference image by ΔZ in the body axis direction, the marker 1 displayed in the reference image area is input to the input unit 22.
The mouse is used to shift in the horizontal direction by a predetermined distance (ΔZ), and a command to complete the change of the photographing position is input from the input unit 22 (step S5). The reference image is ΔZ in the body axis direction
The shifted information is sent from the display 21 to the main control circuit 23. At this time, the main control circuit 23 uses the imaging position information memory 3
The position information before the shift stored in 3 is read out, and ΔZ is added to this. The main control circuit 23 stores the new position information obtained by the addition in the imaging position information memory 33 (step S6). Based on this newly set position information, a real-time image is captured in step S4. That is, the main control circuit 23 transmits to the sequence control circuit 24 as a control signal for forming a new imaging section. Further, according to this control signal, a pulse sequence control signal is sent from the sequence control circuit 24 to the gradient magnetic field power supply 25, the transmitter 17 and the receiver 18.

Next, the pulse currents supplied to the three gradient magnetic field coils 14 according to the pulse sequence control signal are set by the gradient magnetic field power supply 25, and the gradient magnetic field strengths in the slice, phase encode and read directions are newly set. It Similarly, the RF supplied to the irradiation coil 15
The frequency and phase of the pulse are also set by the transmitter 17. The method of setting the pulse current for the gradient magnetic field coil 14 and the RF pulse for the irradiation coil 15 based on the position information of the image cross section displayed on the MR image as described above is described in Japanese Patent Laid-Open No. 2000-189400.

As described above, the gradient magnetic field and the RF pulse for a new imaging section are reset and real-time imaging is performed again, and the three image data obtained are the current images in the real-time imaging image memory 34. Memory 35-1
To 35-3 to update the image data at the time of initial shooting. At this time, the current image on the display unit 21 at the time of initial shooting is also updated to a new image. (Step S4).

Since the movement of the marker on the reference image in FIG. 4 is in the body axis direction, the slice position of only the axial image is updated in the real-time photographed image after the photographing position is changed, but the marker 1 is in any direction. Can be set to. Therefore, all three orthogonal real-time captured images are usually updated and displayed.

FIG. 5 shows the movement of the marker on the reference image in the setting of the photographing position for the main photographing. Figure 5
FIG. 5A shows a case where the image cross section of the MR image moves parallel to the direction of the body axis, and FIG. 5B shows a case where the image cross section of the MR image moves rotationally at the center of the region of interest. In practice, the optimum photographing position is reset by instructing position correction by appropriately combining these two movement methods.

FIG. 6 shows three images which are orthogonal to each other when a new photographing position is set at an angle α with respect to the axial image of the initial image.
6A shows the image before the change, and FIG. 6B shows the image after the change.

As described above, the operation of collecting the three real-time shot images orthogonal to each other while moving the marker on the display 21 is performed until the reference image is set to the optimum position for the main shot. It is repeated (steps S4 to S7).

Next, when the operator selects the main photographing mode of the input section 22, the last real-time photographed image is saved and the real-time photographing is finished. That is, the reference image for main photographing set using the real-time image and the two images orthogonal to the reference image are stored in the real-time photographed image memory 34 in the storage circuit 20, and are related to the position and inclination of the cross section of the image for main photographing. The information is stored in the shooting position information memory 33 in the storage circuit 20, and the real-time shooting ends for the time being (steps S8 to S9).

After the shooting conditions such as the pulse sequence for the main shooting have been set, when the start command for the main shooting is input, the main shooting is started (step S10).
~ S11).

Here, as the pulse sequence for the main photographing, for example, a cine mode high-speed Spin-ech using electrocardiographic synchronization is used.
The method such as SSFP (Stesdy-State-Free-Precession) method is used. That is, when the start command for the main photographing is input, the memory circuit 20 has already been input in step S8.
The data relating to the position and tilt of the real-time photographed image stored in the photographing position information memory 33 (hereinafter collectively referred to as position information) is used. Main control circuit 23
Receives the position information of the last real-time shot image, and uses this data as the position information for main shooting to perform main shooting (step S12). That is, the main control circuit 23 transmits a control signal for forming a main imaging section to the sequence control circuit 24. Further, according to this control signal, a pulse sequence control signal is sent from the sequence control circuit 24 to the gradient magnetic field power supply 25, the transmitter 17 and the receiver 18.

3 according to this pulse sequence control signal
The pulse current supplied to one of the gradient magnetic field coils 14 is set by the gradient magnetic field power supply 25, and the gradient magnetic field strength in each direction of slice, phase encode and read is set.
Similarly, the transmitter 17 also sets the frequency and phase of the RF pulse supplied to the irradiation coil 15.

Next, the sequence control circuit 24 of the control unit 4
The three gradient magnetic field power supplies 25 constituting the gradient magnetic field generation unit 2 are driven by the control signal of 1, and imaging of an MRI image is started. That is, a pulse current for capturing a main captured image is supplied from the gradient magnetic field power supply 25 to the gradient magnetic field coil 14 based on a control signal from the sequence control circuit 24. On the other hand, an RF pulse current is supplied to the irradiation coil 15 from the transmitter 17 of the transmitter / receiver 3.

By supplying the RF pulse current to the coil 15, the subject 11 is irradiated with the RF pulse, and this R
The echo signal generated in the body of the subject 11 by the irradiation of the F pulse is MR-generated by the receiving coil 16 of the transmitting / receiving unit 3.
It is received as a signal.

This MR signal is subjected to signal processing such as intermediate frequency conversion, phase detection and filtering in the receiver 18 and then A / D converted, and further high speed operation / storage unit 5 is provided.
In the frequency space data memory 31 of the memory circuit 20 of FIG. The MR signal arranged in the frequency space is subjected to image reconstruction by the two-dimensional Fourier transform in the high speed calculation / storage unit 5, and this reconstructed image is stored in the reconstructed image memory 32 and switched to the display of the main photographing mode. It is displayed on the monitor of the displayed display unit 21 (step S13).

The operator observes the image for main photographing displayed on the monitor, and when it is confirmed that the main photographing image is photographed at the optimum position, this image is recorded in the main photographing image memory 37 in the storage circuit 20. , And all MRI imaging is completed (steps S17 to S18).

On the other hand, when it is necessary to change the position of the main photographic image, the real-time photographic mode is switched again and the photographic position is reset. That is, the operator selects the real-time shooting mode with the input unit 22, and the monitor of the display unit 21 returns to the real-time shooting display mode. At this time, the monitor displays the current image memory 3 of the real-time captured image memory 34 in step S8.
The three final current images stored in 5-1 to 35-3 and the reference image in the reference image memory 36 are displayed again, and a marker based on the data of the photographing position information memory 33 is also displayed in the reference image area. To be done. (Steps S14 to S15).

The operator drags the mouse to
The image most suitable for changing the position of the reference image among the images is copied to the reference image area, and the marker on the image is moved by the same mouse to reset the position data of the reference image (step S16). Further, the position data at this time is stored in the photographing position information memory 33. When this setting is completed, a command to start the real-time shooting is issued through the input unit 22, and the work of searching for the optimum screen position during the main shooting is continued while observing the real-time shot image on the monitor again (steps S3 to S3). S9). According to the embodiment of the present invention described above, the final image and its position information in the real-time shooting are stored in the real-time image shooting memory 34.
And since it is stored in the shooting position information memory 33,
Even if the position setting of the main shot image is incorrect, immediately read the final image collected during real-time shooting,
Since the appropriate shooting position can be reset based on this final image, the shooting efficiency is significantly improved.

(Second Embodiment) Next, a second embodiment of the present invention will be described with reference to FIGS. 1, 7 and 8. The purpose of this embodiment is to provide an efficient imaging method in the case of collecting a plurality of images of different imaging sites in actual imaging.

FIG. 7 is a block diagram of the high speed operation / storage unit 5. FIG. 8 is a flowchart showing the procedure of imaging in the second embodiment of the present invention, which is an imaging when obtaining Nx main imaging images at different parts Xn (n = 1 to Nx) of the subject 11. Here are the steps:

First, as in the first embodiment, the real-time shooting mode is set in the input section 22 of the apparatus,
Imaging conditions such as a pulse sequence are input (step S21). Next, the first site Xn (n
= 1) is irradiated with light from a light projector (not shown), and the position of the axial image perpendicular to the body axis is set as the reference image to be captured first (step S22).

When the operator inputs a start command for real-time shooting from the input unit 22 following the setting of the above-mentioned shooting conditions, the position information of the reference image (axial image) set in step S22 is used as the main control circuit 23. To the photographing position information memory 41 of the storage circuit 20.
Stored in -1. On the other hand, based on this position information, the main control circuit 23 transmits a control signal for forming this reference imaging cross section to the sequence control circuit 24, and the sequence control circuit 24 supplies the gradient magnetic field power supply 25 and the like. A pulse sequence control signal is sent to the transmitter 17 and the receiver 18.

The pulse current supplied to the gradient magnetic field coil 14 according to the pulse sequence control signal is set by the gradient magnetic field power supply 25, and the slice, phase encode,
The gradient magnetic field strength in each direction of reading is set. Similarly, the transmitter 17 also sets the frequency and phase of the RF pulse supplied to the irradiation coil 15.

Next, the sequence control circuit 24 of the control unit 4
The three gradient magnetic field power supplies 25 constituting the gradient magnetic field generation unit 2 are driven by the control signal of the first part Xn (n = n = n).
The real-time imaging (n = 1) of the MRI image in 1) is started (step S23). At this time, a pulse current for capturing an axial image set as the first reference image of the subject 11 is supplied from the gradient magnetic field power supply 25 to the gradient magnetic field coil 14. On the other hand, the sequence control circuit 24
An RF pulse current is supplied to the irradiation coil 15 from the transmitter 17 of the transmitter / receiver 3 based on the control.

This RF pulse current has the same frequency as the magnetic resonance frequency determined by the strength of the static magnetic field of the main magnet 13, and is modulated by the selective excitation waveform. RF in coil 15
The subject 11 is irradiated with the RF pulse by supplying the pulse current, and the echo signal generated in the body of the subject 11 by the irradiation of the RF pulse is received as the MR signal by the receiving coil 16 of the transceiver 3. .

This MR signal is subjected to signal processing such as intermediate frequency conversion, phase detection and filtering in the receiver 18 and then A / D converted, and further in a frequency space data memory 31 in the storage circuit 20 into a frequency space data. It is saved as raw data. The MR signal arranged in the frequency space is subjected to image reconstruction by the two-dimensional Fourier transform in the high speed operation / storage unit 5, and this image data is stored in the storage circuit 2.
It is temporarily stored in the reconstructed image memory 32 within 0 and is also stored in the real-time captured image memory 42-1.

Subsequently, the gradient magnetic field for photographing the coronal image and the sagittal image orthogonal to the axial image is generated based on the sequence control signal from the sequence control circuit 24. And an RF pulse is formed at the transmitter 17. The MR data obtained at this time is subjected to image reconstruction in the high-speed operation / storage unit 5, and this image data is transferred via the reconstructed image memory 32 in the storage circuit 20 to the real-time captured image memory 42-like the axial image. Stored in 1.

The three real-time photographed images thus obtained are displayed on the display 21 through the main control circuit 23 in the form as shown in FIG. 4 (step S).
24).

The three real-time photographed images are first displayed in the current image area. For example, a coronal image is displayed in the upper right area, an axial image that is a reference image is displayed in the lower left area, and a sagittal image is displayed in the lower right area. When changing the position or angle of the reference image, the image most suitable for the setting is copied to the reference image area by the mouse of the input unit 22. Further, a marker 1 (an axial image position in the initial shooting) for designating a position change in a direction substantially perpendicular to the body axis and a marker 2 (a coronal image position in the initial shooting) for designating a position change in the body axis direction.
Is displayed.

The operator refers to these three images and newly sets the real-time photographed image. For example, when shifting the reference image by ΔZ in the body axis direction, the marker 1 displayed in the reference image area is input to the input unit 22.
The mouse is used to shift in the horizontal direction by a predetermined distance (ΔZ), and a command to complete the change of the photographing position is input from the input unit 22 (step S25). The reference image is Δ in the body axis direction
The Z-shifted information is sent from the display 21 to the main control circuit 23. At this time, the main control circuit 23 reads the pre-shift position information stored in the imaging position information memory 33,
ΔZ is added to this. The new position information obtained by the addition is input to the imaging position information memory 41-1 to update the shooting position information at the time of initial shooting (steps S25 to S2).
6). On the other hand, a real-time image is captured again based on this newly set position information.

As described above, the gradient magnetic field and the RF pulse corresponding to the newly set imaging position are reset, and real-time imaging is performed again. The obtained three image data are stored in the real-time imaging image memory 42-. 1 is input to update the image data at the time of initial shooting. At this time, the display unit 21
The three current images at the initial shooting of are also updated to new images. (Step S24).

In this way, the operation of collecting the three real-time shot images orthogonal to each other while moving the marker on the display 21 is repeated until the reference image is set at the optimum position for the main shot. (Steps S24 to S26), the final real-time image and its position information are input to the real-time captured image memory 42-1 and the position information to the imaging position information memory 41-1 and the data up to that point is updated and saved. (Step S27-
S28).

When the setting of the optimum main photographing position with Xn (n = 1) is completed, the marker is marked with Xn (n) on the image displayed in the reference image area of the real-time photographed image displayed on the display unit 21. = 2) (step S2
9 to S30), real-time shooting is performed by the same operation as in the case of Xn (n = 1), and the obtained final real-time shot image and its position information are stored in the real-time shot image memory 42-2 and the shooting position information memory 41-2. (Steps S24 to S30).

Similarly, for images taken for Xn (n = 3 to Nx), real-time photographed image memories 42-3 to 42-Nx and photographing position information memory 41-
3 to 41-Nx. When the storage of the shooting position information in step S28 is completed in this way, the camera moves to the next real-time shooting area (that is, n = n + 1) and a new real-time shooting is performed, and the last area Xn (n = N
x) when the real-time shooting ends (that is, n>
Nx: Step 29) The real-time shooting mode ends (step S31). When the Nx real-time captured images and their position information are stored, the operator selects the main capturing mode of the input unit 22, and further inputs the capturing conditions including the pulse sequence during the main capturing (step S32). ).

Here, when the start command of the main photographing is inputted, the first position is obtained by using the position information of the real-time photographed image already stored in the photographing position information memory 41-1 of the storage circuit 20 in the step S28. Area Xn (n
= 1), the main photographing is started (step S33).

The main control circuit 23 receives the position information of the last real-time photographed image at Xn (n = 1), and uses this data as the position information to perform the main photographing at Xn (n = 1). That is, the main control circuit 23 transmits a control signal for forming a main imaging section to the sequence control circuit 24. Further, according to this control signal, a pulse sequence control signal is sent from the sequence control circuit 24 to the gradient magnetic field power supply 25 and the transmitter 17 and the receiver 18, and Xn (n is the same as that of the first embodiment of the present invention. =
The image in 1) is captured (steps S34 to S3).
5).

The main control circuit 23 calculates the image photographed at Xn (n = 1) at high speed, and the main photographed image memory 43 of the storage unit 5 is operated.
When it is saved in -1 (step S36), Xn (n =
The shooting position information of the final real-time image in 2) is read from the shooting position information memory 41-2, and Xn (n =
The image obtained by the same operation as 1) is stored in the main captured image memory 43-2. Furthermore, Xn (n = 3 to Nx)
In the same manner, the main photographing is performed in the same manner, and the obtained image is stored in the main photographing image memories 43-3 to 43-Nx.

In this way, when the storage of the main photographed image in step S36 is completed, a new main photographing is performed by moving to the next main photographing portion (that is, n = n + 1), and the final photographing portion Xn (n = n When the main photographing in Nx) is finished (that is, n> Nx: step 37), the main photographing is finished (step S38). In the second embodiment, first, a plurality of different parts Xn (n = 1 to Nx) are used by using real-time imaging.
The optimum position information for the main shooting is stored, and the same part Xn (n
= 1 to Nx), the number of transitions from real-time shooting to actual shooting is only one compared to the conventional method, and the shooting efficiency is greatly improved. Be done. However, as described in the first embodiment, it is necessary to change the position of the shot image at the stage of the main shooting. (Third Embodiment) A third embodiment which solves the above problems in the second embodiment will be described with reference to FIGS. 9 and 10. In the flowcharts of FIGS. 9 to 10 showing the photographing procedure of the third embodiment, steps S41 to S56 are steps S of the flowchart of FIG.
Since it is the same as 21 to S38, the description thereof is omitted.

Different Xn (n = Nx) in step 56
At the time point when the collection of the main photographed images in the region is finished, the main photographed images stored in the main photographed image memories 43-1 to 43-Nx are checked on the display unit 21 by the operator for the quality of the photographing position. If the re-imaging is not necessary, the main imaging ends (step S58). On the other hand, if there is an image that needs re-imaging, the image is returned to real-time imaging and the imaging position is reset.

That is, the operator selects the real-time shooting mode with the input unit 22, and the monitor of the display unit 21 returns to the real-time shooting display mode. At this time, the three final current images and the final reference image stored in the real-time captured image memory 42 in step S48 are again displayed on the monitor, and the marker based on the data of the capturing position information memory 41 is further displayed in the reference image area. Is also displayed. (Steps S57 and S5
9).

The operator drags the mouse to
The image most suitable for changing the position of the reference image among the images is copied to the reference image area, and the marker on the image is moved by the same mouse to reset the position data of the reference image (step S60).

Further, the position data at this time is input to the photographing position information memory 41 and the old data already stored is updated. When this setting is completed, a command to start real-time imaging is given through the input unit 22, real-time imaging is performed again, and the screen position is set again while observing the obtained image on the monitor (steps S61 to S64). .

If the optimum photographing position for the main photographing is set by repeating such setting work,
This real-time photographed image is stored in the real-time photographed image memory 42, and its position information is recorded in the photographing position information memory 41.
And the real-time shooting ends. (Steps S65 to S67).

Next, the operator selects the main photographing mode of the input unit 22, and the position information for the main photographing stored in the photographing position information memory 41 is read (step S6).
8). The pulse current of the gradient magnetic field coil 14 and the RF pulse for transmission of the RF coil are determined on the basis of this position information to collect an MRI image, and this image is stored in the main captured image memory 43 and at the same time in the main capturing mode. Is displayed on the display unit 21 switched to the display of (steps S69 to S70).

The operator observes the displayed image for main photographing, and when it is confirmed that the image is photographed at the optimum position, the main photographed image is saved and the photographing ends (step S71). , S74, S75).

On the other hand, when it is necessary to change the shooting position of the main shot image, the real-time shooting mode is switched again to reset the shooting position. That is, the operator switches the display unit 21 to the real-time shooting display mode by selecting the real-time shooting mode with the input unit 22. At this time, the final real-time image obtained in step S66 is displayed again on the monitor (step S66).
71-S73).

In this way, in the third embodiment, the main photographing and the real-time photographing are repeatedly performed until all the main photographing images can be photographed at the optimum positions. The position information of the final real-time image of is read, and a new shooting position is set for this image. Therefore, the optimum shooting position can be set in a short time, and the shooting efficiency can be improved.

Although the specific embodiments of the present invention have been described above, the present invention is not limited to the above-mentioned embodiments, but can be modified and carried out. For example, the pulse sequence during real-time imaging is not limited to the field-echo method, and other high-speed imaging method may be used. Also, the display method of the real-time captured image is shown for three current images and one reference image,
The display number is not limited to this. Further, the markers displayed on the reference image do not necessarily have to be orthogonal. Furthermore, in the embodiment of the present invention, three two-dimensional images are used as the current images, but the position of the image for main photographing as shown in Japanese Patent Application No. 11-299453 is set from the three-dimensional image data set. It may be a method of doing.

[0082]

As described above, according to the present invention, the real-time photographed image linked with the main photographed image can be used together, so that the position of the photographed image can be set in a short time and the photographing efficiency is excellent. An MRI device can be provided. It should be noted that the present invention is particularly effective for setting a cross-sectional position at an arbitrary angle, which cannot be set without repeating positioning imaging many times, such as when imaging a specific cross section of the heart.

[Brief description of drawings]

FIG. 1 is a diagram showing a schematic configuration of an entire MRI apparatus according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a configuration of a high-speed calculation / storage unit according to the first embodiment of the present invention.

FIG. 3 is a diagram showing an imaging procedure flowchart in the first embodiment of the present invention.

FIG. 4 is a diagram showing a method of displaying a real-time captured image according to the present invention.

FIG. 5 is a diagram showing a method of selecting an imaging position by using a marker of the present invention.

FIG. 6 is a diagram showing real-time captured images before and after updating a capturing position according to the present invention.

FIG. 7 is a diagram showing a configuration of a high speed operation / storage unit according to a second embodiment of the present invention.

FIG. 8 is a diagram showing an imaging procedure flowchart in the second embodiment of the present invention.

FIG. 9 is a diagram showing an imaging procedure flowchart in the third embodiment of the invention.

FIG. 10 is a diagram showing an imaging procedure flowchart in the third embodiment of the invention.

[Explanation of symbols]

19 ... High-speed arithmetic circuit 21 ... Display 22 ... Input section 23 ... Main control circuit 31 ... Frequency space data memory 32 ... Reconstructed image memory 33 ... Shooting position information memory 34 ... Real-time shooting image memory 37 ... Main shooting image memory

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 4C096 AA20 AB37 AB50 AD02 AD14                       AD15 AD25 AD30 BB21 DC33                       DC40 DD01 DD13                 5B057 AA07 BA07 BA24 BA26 CA08                       CA13 CA16 CC03 CH08 CH11                       CH18 DA02 DA04 DA07 DA08                       DA16 DB03 DB09 DC08 DC09                       DC32

Claims (7)

[Claims] 1. An MRI apparatus for performing first image capturing at a plurality of positions set by an operator and performing second image capturing using image capturing position information of the images. When the position information storage unit that stores the shooting position information of the last acquired image and the change of the shooting position of the second image are instructed, from the shooting of the second image to the first image A shooting position correction unit is provided for shifting to shooting and obtaining changed shooting position information of the second image, and the shooting position correction unit is an initial image at the time of shifting to shooting of the first image. The MRI apparatus further includes a display unit that displays the last acquired first image corresponding to the imaging position information stored in the position information storage unit. 2. The display means has at least two display areas for displaying a captured image, and one display area has a marker for indicating a position where the first image is captured together with the first image. The MRI apparatus according to claim 1, further comprising: 3. The photographing position correcting means has an input means for an operator to move the position of the marker, and the photographing of the first image based on the position of the marker newly set by the operator. 3. The MR according to claim 2, wherein
I device. 4. The MRI according to claim 1, wherein the second image has a higher resolution than the first image.
apparatus. 5. A first image is photographed at a plurality of positions set by an operator, and a second image having a higher resolution than the first image is photographed according to the photographing position of the first image. In the MRI apparatus for performing, a display device for displaying the photographed first image, a photographing position correcting means for correcting the photographing position of the first image displayed on the display device, and a photographing position correcting means for correcting the photographing position. Position information storage means capable of storing a plurality of shooting position information of the first image, and when the shooting of the second image is instructed, the plurality of shooting positions stored in the position information storage means. An MRI apparatus characterized in that a plurality of second image capturing operations are collectively executed based on information. 6. The MRI apparatus according to claim 5, wherein the display device displays the first image together with a marker for indicating a position where the first image is photographed. 7. The position correction means has an input means for an operator to move the position of the marker, and stores the position of the marker newly set by the operator in the position information storage means. The MRI apparatus according to claim 5, which is characterized in that: