JP5638192B2 - Magnetic resonance imaging system - Google Patents

Description

  The present invention measures nuclear magnetic resonance (hereinafter referred to as `` NMR '') signals from hydrogen, phosphorus, etc. in a subject and images nuclear density distribution, relaxation time distribution, etc. In particular, the present invention relates to a magnetic resonance imaging apparatus capable of imaging a wide range or whole body of a subject divided into a plurality of regions.

  Magnetic resonance imaging equipment (hereinafter referred to as MRI equipment) divides the subject into multiple regions (hereinafter referred to as stations) for imaging (hereinafter referred to as multi-station imaging), and images at each station position There is a multi-station imaging method in which an image (hereinafter referred to as a station image) is synthesized for each image type to create a wide range image of a subject.

  In the multi-station imaging method, a plurality of image types such as T1-weighted images, T2-weighted images, and proton density images are captured at each station while moving the bed, and the station images acquired at each station are synthesized. A wide range image of the subject is created for each image type (see, for example, Non-Patent Document 1).

  In the multi-station imaging method that performs imaging over a wide range, the number of images that can be obtained increases, which increases the burden on the operator for image confirmation after imaging. As a method for reducing the burden, Patent Document 1 discloses that a plurality of station images are classified by sequence, station, or slice so that the upper part of the screen is a head image and the lower part of the screen is a leg image. An example of display is disclosed.

  Japanese Patent Application Laid-Open No. 2004-228561 describes a technique for realizing a screen display layout change using various information attached to an image.

  Furthermore, Patent Document 3 describes a technique for efficiently selecting and displaying series data of a plurality of imaging regions.

WO 2006-134958 JP 2004-33381 A JP 2007-244624 A Japan Medical Association Vol. 61, No. 10, pp. 21-22, 2001

  However, Patent Documents 1, 2, 3, and Non-Patent Document 1 are processing techniques for images after all multi-station imaging has been completed. In the prior art, display and composition processing are performed after the imaging of all stations is completed. Therefore, there is always a time for waiting for the end of imaging.

  Furthermore, if the imaging type, the number of stations, and the number of multi-slices are increased, the imaging time is extended accordingly, so that the waiting time of the operator until the station image can be displayed and synthesized can be extended.

  Accordingly, an object of the present invention is to provide an MRI apparatus capable of realizing the efficiency improvement of the multi-station imaging procedure and the improvement of the throughput.

  In order to achieve the above object, the MRI apparatus of the present invention includes a means for determining a display layout at the time when parameters for multi-station imaging are set, a means for performing display immediately from an image that has been reconstructed, and 2 It is characterized by having means for determining the positional relationship with the previous station image immediately after completing the image reconstruction beyond the station, and combining and displaying it.

  According to the present invention, the time from image acquisition to image alignment display can be shortened, and the overall throughput of multi-station imaging can be improved. In addition, the whole body image can be monitored immediately by combining and displaying the images after the reconstruction. In addition, even if the image acquisition fails due to a body movement or the like, it can be confirmed immediately that it is a failure, so that measures such as re-shooting can be performed immediately.

  Hereinafter, preferred embodiments of the MRI apparatus of the present invention will be described with reference to the accompanying drawings. Note that components having the same function are denoted by the same reference symbols throughout the drawings for describing the embodiments of the invention, and the repetitive description thereof is omitted.

First, an overall outline of an example of an MRI apparatus according to the present invention will be described with reference to FIG.
FIG. 1 is a block diagram showing the overall configuration of an embodiment of an MRI apparatus according to the present invention. This MRI apparatus obtains a tomographic image of a subject using the NMR phenomenon. As shown in FIG. 2, the MRI apparatus includes a static magnetic field generation system 2, a gradient magnetic field generation system 3, a transmission system 5, A reception system 6, a signal processing system 7, a sequencer 4, and a central processing unit (CPU) 8 are provided.

  The static magnetic field generation system 2 generates a uniform static magnetic field in the direction perpendicular to the body axis in the space around the subject 1 if the vertical magnetic field method is used, and in the direction of the body axis if the horizontal magnetic field method is used. Thus, a permanent magnet type, normal conducting type or superconducting type static magnetic field generating source is arranged around the subject 1.

The gradient magnetic field generating system 3 includes a gradient magnetic field coil 9 wound in the three axes of X, Y, and Z, which is a coordinate system (stationary coordinate system) of the MRI apparatus, and a gradient magnetic field power source 10 for driving each gradient magnetic field coil. The gradient magnetic fields Gx, Gy, Gz are applied in the three axial directions of X, Y, and Z by driving the gradient magnetic field power supply 10 of each coil according to a command from the sequencer 4 described later. At the time of imaging, a slice direction gradient magnetic field pulse (Gs) is applied in a direction orthogonal to the slice plane (imaging cross section) to set a slice plane for the subject 1, and the remaining two orthogonal to the slice plane and orthogonal to each other A phase encoding direction gradient magnetic field pulse (Gp) and a frequency encoding direction gradient magnetic field pulse (Gf) are applied in one direction, and position information in each direction is encoded into an echo signal.
The sequencer 4 is a control means that repeatedly applies a high-frequency magnetic field pulse (hereinafter referred to as an “RF pulse”) and a gradient magnetic field pulse in a predetermined pulse sequence, and operates under the control of the CPU 8 and tomographic image data of the subject 1 Various commands necessary for collection are sent to the transmission system 5, the gradient magnetic field generation system 3, and the reception system 6.

  The transmission system 5 irradiates the subject 1 with RF pulses in order to cause nuclear magnetic resonance to occur in the nuclear spins of the atoms constituting the living tissue of the subject 1, and includes a high frequency oscillator 11, a modulator 12, and a high frequency amplifier. 13 and a high frequency coil (transmission coil) 14a on the transmission side. The high-frequency pulse output from the high-frequency oscillator is amplitude-modulated by the modulator 12 at the timing according to the command from the sequencer 4, and the amplitude-modulated high-frequency pulse is amplified by the high-frequency amplifier 13 and then placed close to the subject 1. By supplying to the high frequency coil 14a, the subject 1 is irradiated with the RF pulse.

  The receiving system 6 detects an echo signal (NMR signal) emitted by nuclear magnetic resonance of nuclear spins constituting the biological tissue of the subject 1, and receives a high-frequency coil (receiving coil) 14b on the receiving side and a signal amplifier 15 And a quadrature phase detector 16 and an A / D converter 17. After the NMR signal of the response of the subject 1 induced by the electromagnetic wave irradiated from the high frequency coil 14a on the transmission side is detected by the high frequency coil 14b arranged close to the subject 1 and amplified by the signal amplifier 15, The quadrature phase detector 16 divides the signal into two orthogonal signals at the timing according to the command from the sequencer 4, and each signal is converted into a digital quantity by the A / D converter 17 and sent to the signal processing system 7.

  The signal processing system 7 performs various data processing and display and storage of processing results, and has an external storage device such as an optical disk 19 and a magnetic disk 18 and a display 20 composed of a CRT, etc. Is input to the CPU 8, the CPU 8 executes processing such as signal processing and image reconstruction, and displays the tomographic image of the subject 1 as a result on the display 20, and the magnetic disk 18 of the external storage device. Record in etc.

  The operation unit 25 inputs various control information of the MRI apparatus and control information of processing performed in the signal processing system 7, and includes a trackball or mouse 23 and a keyboard 24. The operation unit 25 is disposed close to the display 20, and the operator controls various processes of the MRI apparatus interactively through the operation unit 25 while looking at the display 20.

  In FIG. 1, the high-frequency coil 14a and the gradient magnetic field coil 9 on the transmission side face the subject 1 in the static magnetic field space of the static magnetic field generation system 2 in which the subject 1 is inserted in the vertical magnetic field method. If the horizontal magnetic field method is used, the subject 1 is installed so as to surround it. The high-frequency coil 14b on the receiving side is installed so as to face or surround the subject 1.

  At present, the radionuclide to be imaged by the MRI apparatus is a hydrogen nucleus (proton) which is a main constituent material of the subject as being widely used clinically. Information on the spatial distribution of the proton density and the spatial distribution of the relaxation time of the excited state is imaged, thereby imaging the form or function of the human head, abdomen, limbs, etc. two-dimensionally or three-dimensionally.

<Example 1>
Next, the flow of multi-station imaging using the present invention will be described.
FIG. 2 is a flowchart illustrating an example of the flow of multi-station imaging.
Step 1: An operator registers information on a patient to be imaged.
Step 2: The operator sets a multi-station imaging protocol.
Step 3: The operator starts scanogram imaging.
Step 4: The operator performs multi-station positioning and parameter confirmation / change.
Step 5: The device determines the display format from the protocol information.
Step 6: The operator starts actual imaging.
Step 7: The apparatus performs signal measurement and reconstruction, and acquires an image.
Step 8: The device displays the reconstructed image at a predetermined position in the display format.
When the display format is composite display, the reconstructed images up to the previous station or composite images thereof are combined and displayed.
Step 9: The apparatus determines whether all imaging has been completed.
Step 10: The apparatus repeats measurement, reconstruction, and display until the end of imaging.

  The multi-station imaging protocol in Step 2 is a set of imaging sequences prepared for imaging a wide area of the subject 1, and the image type and station position are set, and imaging is performed in the set order. By performing the above, a desired image can be obtained.

  The protocol is roughly divided into scanogram imaging for acquiring an image used for positioning, and main imaging for imaging each station in accordance with positioning on the scanogram obtained by scanogram imaging.

The operator first starts scanogram imaging (step 3).
In scanogram imaging, each station is imaged in a scanogram sequence while the bed is moved.

  After all imaging is completed, the obtained image is displayed on the positioning screen, and the operator inputs the imaging position on the image. Further, when it is necessary to change the parameters of the main imaging, new parameters are input (step 4).

From the imaging position and parameters input by the operator, the number of images, the image type, and the number of stations obtained by starting the main imaging are determined. From this information, the display format of the captured image is determined (step 5).
For example, if the number of stations is 4, and each station is set to capture five T1-weighted images, T2-weighted images, and proton images, the display format is set to a vertical station ( Head to foot) are arranged side by side (T1 → T2 → Proton), and it is decided to display multi-slices by switching tabs.
By this determination, the display on the display is switched.

  The operator starts actual imaging (step 6).

  The apparatus executes an imaging sequence according to the protocol, performs signal measurement and reconstruction, and acquires an image (step 7).

  The obtained image has a known station position, image type, and slice number. Therefore, since the image display position in the display format can be uniquely determined, it is immediately displayed at that position (step 8).

  Information for determining the image display position may be referred to image information generated by the device to be added to the reconstructed image, an index given for classification, a DICOM tag, or the like. Since the order is known, a method of displaying in order of imaging may be used, and there is no limitation on the means as long as an image is displayed at the position.

  The format shown in FIG. 3 is divided for each station, but composite display can also be set as a display format. For example, if a composite display format as shown in FIG. 4 is set in advance, when an image is obtained after two or more stations are captured, the positional relationship with the previous station is determined, and composite processing is performed. The image is replaced with the already displayed image.

The apparatus determines whether or not the imaging set in the protocol has been completed (step 9), and repeats imaging and display until the imaging set in the protocol is completed (step 10).
A specific display image will be described.
FIG. 5A is a display example when the T1-weighted imaging of one station is completed.
FIG. 5B is a display example at the time when the T2-weighted imaging of one station is completed.
FIG. 5-3 is a display example at the time when all the imaging of one station is completed and T1 weighted imaging of two stations is completed.
FIG. 5-4 is a display example when the composite display format is set. After the reconstruction is completed, it is sequentially combined and automatically updated and displayed.

The display format in step 5 is determined uniquely by registering the format in advance.
For example, defaults are set in advance from the following cases.
Fig. 6-1: Multiple slices and multiple sequences are displayed for each station.
Fig. 6-2: Multi-slice display of whole sequence images in one sequence.
FIG. 6-3: Composite display of FIG. 6-2.
FIG. 6-4: Multiple whole body images of the same slice are displayed side by side.
6-5: Composite display of FIG. 6-4.
Alternatively, the format may be automatically determined from FIGS. 6-1 to 6-5 by a combination of a plurality of conditions obtained from the imaging conditions.

Also, the format is not limited to that shown in the above example, and various formats can be set according to the diagnostic application by previously registering the object to be compared.
For example, when there are uses such as comparing images picked up by changing TE in the same sequence, a layout in which a plurality of whole body images of the same slice as shown in FIG. 6-6 are displayed side by side is also possible.

<Example 2>
Next, Example 2 will be described with reference to the drawings. A difference from the first embodiment is an instruction to re-shoot. Hereinafter, only different portions will be described, and description of the same portions will be omitted.
When it is found that the image displayed in the display format in step 8 in FIG. 2 is an imaging failure due to a cause such as body movement of the subject, the operator designates the failure image, thereby imaging the position. Try again.

The flow of a reshooting instruction in the second embodiment will be described with reference to FIG.
The operator confirms the image displayed on the display format (step 21).
When the failed image is confirmed (step 22), the mouse is clicked on the image (step 23).
The apparatus stores the station position, sequence, and slice number of the selected image in a list (step 24).

It is determined whether the selected image belongs to the station and sequence currently being captured (step 25). If so, the imaging is immediately stopped (step 26). After referring to the list and confirming the station and sequence to be re-imaged, the imaging is started again (step 27). The image after re-imaging is displayed in a display format by replacing the image before re-taking.
It is determined whether the selected image is the same as the station currently being imaged (step 28). If the selected image is the same but the sequence is different, the process waits for the sequence being imaged to end (step 29), Take an image.

If the station is different from the station that is currently imaging, the process waits until all imaging of the current station is completed (step 30), and after completion, the bed is moved to perform imaging again.
When selecting a failed image on the combined display, the user clicks on the failed portion on the combined image. From the clicked position, the station position, sequence, and slice number of the selected image are determined.
After the re-imaging, the image before re-taking and the re-captured image are replaced and a combining process is performed to update the display.

Note that the failure image may be determined not only by the operator's instruction but also automatically by the apparatus.
For example, when paying attention to the composite display, it is conceivable to extract the contour of the body to detect the connection with the previous station, and to determine that the imaging has failed when a shift greater than a threshold is detected. Also in this case, the processing after the determination is the same as the flow after step 24.

The perspective view of the whole basic composition in one example of the MRI apparatus concerning the present invention. The figure explaining the flow of the multi-station imaging using this invention. The figure which shows an example of the display format of this invention. The figure which shows an example of the display format of this invention. The figure explaining the image of the image display during imaging of this invention. The figure explaining the image of the image display during imaging of this invention. The figure explaining the image of the image display during imaging of this invention. The figure explaining the image of the image display during imaging of this invention. The figure which shows an example of the default display format of this invention. The figure which shows an example of the default display format of this invention. The figure which shows an example of the default display format of this invention. The figure which shows an example of the default display format of this invention. The figure which shows an example of the default display format of this invention. The figure which shows an example of the default display format of this invention. The figure explaining the flow which implement | achieves the re-imaging instruction | indication of this invention.

Explanation of symbols

  1 ... subject, 2 ... static magnetic field generation system, 3 ... gradient magnetic field generation system, 4 ... sequencer, 5 ... transmission system, 6 ... reception system, 7 ... signal processing system, 8 ... central processing unit (CPU), 9 ... Gradient magnetic field coil, 10 ... Gradient magnetic field power supply, 11 ... High frequency transmitter, 12 ... Modulator, 13 ... High frequency amplifier, 14a ... High frequency coil (transmitting coil), 14b ... High frequency coil (receiving coil), 15 ... Signal amplifier, 16 ... Quadrature phase detector, 17 ... D converter, 18 ... Magnetic disk, 19 ... Optical disk, 20 ... Display, 21 ... ROM, 22 ... RAM, 23 ... Trackball or mouse, 24 ... Keyboard, 51 ... Gantry, 52 ... Table, 53 ... Case, 54 ... Processing device.

Claims (6)

The subject is divided into a plurality of regions, the subject is imaged for each image type at a station corresponding to each of the plurality of regions, and the station image captured at each station is synthesized for each image type. In a magnetic resonance imaging apparatus for performing multi-station imaging for creating images in a plurality of regions of the subject,
Means for determining a display format for displaying a captured image of the subject based on the set parameters at the time when parameters necessary for executing the multi-station imaging are set;
Means for performing image reconstruction using an echo signal emitted from the subject to create a station image, and sequentially displaying on the display screen according to the display format from the image for which the image reconstruction has been completed;
Means for determining the positional relationship between one station image and another station image when the image reconstruction is completed at two or more stations, and combining and displaying both station images. ,
Magnetic resonance imaging apparatus characterized by performing re-imaging of the selected station image as different from the display screen in Nozomu Tokoro image. The subject is divided into a plurality of regions, the subject is imaged for each image type at a station corresponding to each of the plurality of regions, and the station image captured at each station is synthesized for each image type. In a magnetic resonance imaging apparatus for performing multi-station imaging for creating images in a plurality of regions of the subject,
Means for determining a display format for displaying a captured image of the subject based on the set parameters at the time when parameters necessary for executing the multi-station imaging are set;
Means for performing image reconstruction using an echo signal emitted from the subject to create a station image, and sequentially displaying on the display screen according to the display format from the image for which the image reconstruction has been completed;
Means for determining the positional relationship between one station image and another station image when the image reconstruction is completed at two or more stations, and combining and displaying both station images. ,
A magnetic resonance imaging apparatus comprising: determining whether a station image displayed on the display screen is different from a desired image, and performing re-imaging of the station image determined to be different from the desired image. The magnetic resonance imaging apparatus according to claim 1.
It is determined whether the selected image is an image of a station and a sequence being captured at the time of selection. If the selected image is an image being captured, the imaging is stopped and imaging of the selected image is started again. A magnetic resonance imaging apparatus comprising: means for restarting imaging of the selected image after waiting for the sequence being imaged to end when the sequence is the same station but different. The magnetic resonance imaging apparatus according to claim 2.
It is determined whether the determined image is an image of a station and a sequence being captured at the time of determination. If the determined image is an image being captured, the imaging is stopped and imaging of the determined image is started again. A magnetic resonance imaging apparatus comprising: means for re-starting imaging of the determined image after waiting for the sequence being imaged to end when the sequence is the same station but different. The magnetic resonance imaging apparatus according to claim 1 or 2,
The determination of the positional relationship uses a magnetic resonance imaging apparatus using image information such as station positions, sequences, slice numbers or indexes assigned for classification, DICOM tags, etc. of images stored in advance. The magnetic resonance imaging apparatus according to claim 1 or 2,
The magnetic resonance imaging apparatus according to claim 1, wherein the display format is uniquely determined at the time when the format is registered in advance and parameters necessary for executing the multi-station imaging are set.

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