JP5337383B2 - Magnetic resonance imaging apparatus and positioning method - Google Patents

Description

  The present invention requires a magnetic resonance imaging apparatus that images the internal structure and fluid dynamics using the magnetic resonance phenomenon of the nucleus inside the subject, and is necessary as a preliminary preparation when imaging with the apparatus. The present invention relates to a positioning method for setting the position of a proper imaging region.

  Magnetic resonance imaging is a medical magnetic resonance imaging, in which a nuclear spin of a subject placed in a static magnetic field is magnetically excited with a high frequency signal of Larmor frequency, and FID (free induction decay) generated by this excitation. This is an imaging method based on obtaining an image of a subject from a signal or an echo signal.

  In this magnetic resonance imaging, prior to actual imaging (main imaging), a positioning process for specifying the imaging position is often performed. In this positioning process, the already collected three-dimensional image data may be reconstructed and used, or a new positioning scan may be performed to collect positioning image data.

Conventionally, for positioning in magnetic resonance imaging, a method of setting the next imaging position by setting a three-dimensional ROI on a reference image for positioning is known, as described in Patent Document 1, for example. Yes. A plurality of positioning reference images can be displayed simultaneously, and an ROI is displayed on each image.
JP 2000-189400 A

  However, although a plurality of positioning reference images can be displayed at the same time, it is not limited that they are parallel or perpendicular to each other. Therefore, even if a three-dimensional ROI is displayed vertically on a certain reference image, it is not always parallel or vertical on other images, and this three-dimensional ROI can be freely rotated and displayed three-dimensionally. There were many. As a result, it is difficult to determine at which position on the image the set three-dimensional ROI intersects, and it is necessary to re-take the image several times before obtaining the image of interest. It was happening. In order to prevent such a reduction in work efficiency, considerable experience and skill are required in the positioning skill of the operator.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a positioning method in magnetic resonance imaging capable of more efficiently executing a positioning operation using a reference image.

  In order to solve the above problems, the present invention provides a positioning method in magnetic resonance imaging as one aspect thereof. In this positioning method, a first display step of displaying, as a reference image, a part of tomographic image data in three-dimensional image data composed of a plurality of prepared tomographic image data in a region including a region to be imaged of a subject. A first setting step for setting a three-dimensional ROI (region of interest) on the reference image displayed in the first display step, and the three-dimensional ROI set in the first setting step. An editing step of editing the projection data when the three-dimensional image data is projected from at least one of a direction perpendicular to the three-dimensional ROI and a horizontal direction; and the projection data edited by the editing step is used for positioning And a second display step of displaying together with the three-dimensional ROI as a reference image.

  Moreover, in order to solve the said subject, this invention provides the magnetic resonance imaging apparatus as another aspect. In this magnetic resonance imaging apparatus, a first tomographic image data is displayed as a reference image in a part of a three-dimensional image data composed of a plurality of tomographic image data prepared in advance in an area including a part to be imaged of a subject. Display means, first setting means for setting a three-dimensional ROI (region of interest) on the reference image displayed by the first display means, and the three-dimensional ROI set by the first setting means Editing means for editing projection data when the three-dimensional image data is projected from at least one of a direction perpendicular to the three-dimensional ROI and a horizontal direction on the top, and positioning the projection data edited by the editing means Second display means for displaying together with the three-dimensional ROI as a reference image for use.

  According to the positioning scanning method and the magnetic resonance imaging apparatus of the present invention, for example, a part (for example, one or two or more) of three-dimensional image data composed of a plurality of pieces of tomographic image data for a diagnostic region of a subject. A tomographic image is designated and displayed as a reference image. A three-dimensional ROI is set on the reference image, and image data projected from the vertical and / or horizontal direction on the three-dimensional ROI is further edited from the three-dimensional image data. The edited image data is displayed as a reference image at the time of positioning together with the three-dimensional ROI. For this reason, it becomes possible to easily determine at which position on the image the set three-dimensional ROI intersects. Therefore, the work efficiency of ROI setting, that is, positioning can be increased.

Hereinafter, with reference to FIGS, illustrating an embodiment of a magnetic resonance imaging (MRI) apparatus according to the present invention.

  FIG. 1 is a block diagram of a magnetic resonance imaging apparatus according to the embodiment. The magnetic resonance imaging apparatus includes a magnet unit for generating a static magnetic field, a gradient magnetic field unit for generating a gradient magnetic field for giving positional information to the static magnetic field, a transmitter / receiver unit for receiving magnetic excitation and NMR signals, It has functionally a control / arithmetic unit for system control and data processing.

Specifically, as illustrated in FIG. 1, the magnet unit includes, for example, a normal conducting magnet 1 and a static magnetic field power source 2 that supplies current to the magnet 1, and an opening into which the subject P is inserted. A static magnetic field H ₀ is generated in the z-axis direction.

The gradient magnetic field unit includes three pairs of gradient magnetic field coils 4 in the x-axis, y-axis, and z-axis directions incorporated in the magnet 1, a drive circuit 5 that supplies current to these gradient magnetic field coils 4, and And a gradient magnetic field power supply including the gradient magnetic field control device 6. The gradient magnetic field control device 6 operates the drive circuit 5 in accordance with the pulse sequence supplied from the main control device 7. Accordingly, in order to impart positional information for imaging, by superimposing a linear magnetic field in the static magnetic field H _0, the gradient magnetic field is formed.

  The transmission / reception unit includes a transmission coil 8a and a reception coil 8b disposed to face the subject P in the opening of the magnet 1, and a transmitter 9 individually connected to the transmission coil 8a and the reception coil 8b. And a receiver 10. The transmitter 9 generates a high-frequency pulse for exciting NMR (nuclear magnetic resonance) based on a command from the control device 7. The receiver 10 receives and amplifies the NMR signal obtained by the receiving coil 8 b, and sends the NMR signal to the storage device 11 based on a command from the control device 7.

  Further, the control / arithmetic unit receives the operation command from the control device 7 connected to the transmitter 9, the receiver 10, and the gradient magnetic field control device 6, the storage device 11 that stores the NMR signal, and the control device 7. , An arithmetic device 12 for processing a memory signal of the storage device 11 and a display device 13 for display. An input device 14 such as a keyboard and a mouse is connected to the control device 7. The control device 7 instructs the transmitter 9, the receiver 10, and the gradient magnetic field control device 6 to perform a pulse sequence necessary for actual imaging (main scan), and cooperates with the input device 14 and the display device 13. Thus, the positioning process for determining the position of the main scan is executed interactively. This positioning process includes a three-dimensional ROI (region of interest) setting process, which will be described later.

  The arithmetic device 12 generates image data by subjecting the captured NMR signal to a huge amount of arithmetic processing including Fourier transform. This image data is displayed on the display device 13 as necessary. In this way, magnetic resonance imaging is performed, and image data, that is, an image obtained by magnetic resonance imaging is displayed on the display device 13 and stored in the storage device 11.

  In order to execute magnetic resonance imaging, it is necessary to perform so-called positioning, in which part of the subject to be imaged, the imaging position is determined prior to actual imaging (main scan). For this positioning, positioning image data is obtained by executing magnetic resonance imaging for positioning (referred to as positioning scan, pre-scan, preparatory scan, etc.). In this embodiment, three-dimensional image data (volume data) of the imaging region of the subject or a plurality of sets of image data acquired from different directions are collected as positioning images by this magnetic resonance scan for positioning. The positioning image data is stored in the storage device 11 in advance, and is read out under the control of the control device 7 during the positioning operation and displayed on the display device 13.

Next, with reference to FIGS, mainly positioning processing using a three-dimensional shape of the ROI (region of interest), illustrating the effect of the magnetic resonance imaging apparatus according to the present embodiment.

  FIG. 2 shows an outline of the positioning process executed by the control device 7. The control device 7 receives the operator's predetermined operation information from the input device 4 and performs the positioning process shown in FIG.

  As shown in the figure, the control device 7 reads out image data (reference image data) to be used as a reference image for positioning from the storage device 11 at the start of the processing (step S1). This reference image data is a set of three-dimensional image data prepared in advance or data captured from different directions. In the present embodiment, for example, three tomographic images captured or reconstructed from three directions of sagittal S, axial A, and coronal C are used as reference images (see FIG. 3). One tomographic image may be adopted as the reference image.

  Next, the control device 7 displays the three tomographic images on the display device 13 (step S2). Then, based on the operation information, it is determined whether or not this displayed image can be used as a reference image (step S3). When it is desired to replace the image displayed by the operator with another reference image, the control device 7 returns the process to step S2. As a result, the operator can freely select the reference image from the already captured image group.

  When the reference image is determined in this way, the control device 7 sets and displays the three-dimensional ROI at the initial position (step S4: see FIG. 3). The three-dimensional ROI employs a plate-shaped ROI having a thickness here, but may be another three-dimensional ROI. This three-dimensional ROI is for setting an imaging position for the main imaging to be scanned later.

  Next, the control device 7 determines whether or not it is necessary to change (move, rotate) the position of the three-dimensional ROI while referring to the operation information of the operator coming from the input device 14 (step S5). For this reason, when the operator desires to change the position, the displayed three-dimensional ROI is moved and / or rotated according to the contents of the operation information (step S6). This moving operation is performed on any one of the three sagittal images S, the axial images A, and the coronal images C, and the processing performed on one image is applied to the position of the three-dimensional ROI on the remaining two images. (Refer to FIG. 4 reflected immediately). This series of processing is performed interactively, and finally the 3D ROI is placed at the 3D spatial position desired by the operator (step S7).

  At this time, since the reference image is data of a cross section taken from different directions, the position-changed three-dimensional ROI is displayed in three dimensions.

Accordingly, the control device generates an image of the subject by projecting from the vertical and / or horizontal direction of the three-dimensional ROI from the three-dimensional image data prepared in advance, and displays it together with the three-dimensional ROI (steps S8 and S9) FIG. 5). In this embodiment, two directions H1 and H2 that are horizontal to the three-dimensional ROI are set on the sagittal image S as reprojection directions, and an image viewed from these directions is reconstructed and reconstructed. Display the image as a reference image. That is, the reference picture image is an image when projected along one horizontal direction H1, may be displayed together with three-dimensional ROI. Ginseng Teruga image is an image when projected along the other horizontal direction H2, may be displayed together with three-dimensional ROI.

  The projection direction when generating this projection image may be a direction perpendicular to the three-dimensional ROI, and the image for determining the projection direction is not limited to the sagittal image S, but the axial image A or the coronal image C. May be used.

  The control device 7 again determines whether or not the position of the three-dimensional ROI may be the current position based on operation information from the operator (step S10). The operator observes both the three-dimensional ROI on the reference image already displayed and the three-dimensional ROI on the image along the direction newly projected this time, and the three-dimensional ROI is at a desired position. It can be judged whether or not.

  Therefore, when it is determined that the current position of the three-dimensional ROI is not appropriate, the three-dimensional ROI is reset on the reference image based on the operation information (step S11), or the three-dimensional ROI is displayed on the projection image. Reset is performed (steps S12 and S13). When resetting the three-dimensional ROI on the reference image, the control device 7 returns the process to step S4. On the other hand, when resetting the three-dimensional ROI on the projection image, the control device 7 shifts the process to step S13 to reset and display the three-dimensional ROI on the projection image.

  Through these processes, the spatial position coordinates of the three-dimensional ROI finally determined are taken into the storage device 11 as the ROI position, that is, the scan position at the time of actual imaging (step S14).

  As described above, a vertical or horizontal image is edited and displayed with respect to the three-dimensional ROI at the time of positioning using the cross-sectional conversion technology from the three-dimensional image data prepared in advance. For this reason, even if the three-dimensional ROI displayed on a plurality of reference images that are not parallel or perpendicular to each other is displayed in a three-dimensional manner, the operator can edit the three-dimensional ROI as if projected from the vertical or horizontal direction. Additional images can be referenced. Furthermore, a three-dimensional ROI can be set on the reference image.

  As a result, the intersection position between the three-dimensional ROI and the reference image, which has been difficult to predict so far, can be confirmed by visual observation, and it is not necessary to perform positioning according to the feeling as in the past, and the desired positioning is performed accurately. be able to. Therefore, the throughput of positioning scan in magnetic resonance imaging can be remarkably improved, and the operational burden on the operator can be greatly reduced.

1 is a block diagram showing a schematic configuration of a magnetic resonance imaging apparatus according to an embodiment of the present invention. The flowchart explaining the outline | summary of the ROI setting process for the positioning performed with the control apparatus of an Example. The figure which displayed the reference image and three-dimensional ROI. The figure at the time of rotating 3D ROI. The figure which showed the horizontal direction of three-dimensional ROI .

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Magnet 4 Gradient magnetic field coil 5 Drive circuit 6 Gradient magnetic field control apparatus 7 Control apparatus 8a Transmission coil 8b Reception coil 9 Transmitter 10 Receiver 11 Storage apparatus 12 Calculation apparatus 13 Display apparatus 14 Input device

Claims (6)

A first display step of displaying, as a reference image, a part of tomographic image data in three-dimensional image data composed of a plurality of tomographic image data prepared in advance in an area including a region to be imaged of a subject;
A first setting step of setting a three-dimensional ROI (region of interest) on the reference image displayed in the first display step;
An editing step of editing projection data when the three-dimensional image data is projected from at least one of a direction perpendicular to the three-dimensional ROI and a horizontal direction on the three-dimensional ROI set in the first setting step. When,
And a second display step of displaying the projection data edited in this editing step together with the three-dimensional ROI as a positioning reference image. The positioning method according to claim 1,
A positioning method in magnetic resonance imaging, further comprising: a second setting step of setting a spatial position of the three-dimensional ROI on the reference image displayed in the second display step. The positioning method according to claim 1 or 2,
The first display step is a step of displaying at least one tomographic image data as a partial tomographic image data in the three-dimensional image data including the plurality of tomographic image data. Positioning method in magnetic resonance imaging. In the positioning method according to any one of claims 1 to 3,
The magnetic resonance imaging method according to claim 1, wherein the editing step is a step of editing projection data when the three-dimensional image data is projected from both a direction perpendicular to the three-dimensional ROI and a horizontal direction. First display means for displaying, as a reference image, a part of tomographic image data in a three-dimensional image data composed of a plurality of tomographic image data prepared in advance in an area including a region to be imaged of a subject;
First setting means for setting a three-dimensional ROI (region of interest) on the reference image displayed by the first display means;
Editing means for editing projection data when the three-dimensional image data is projected on at least one of a direction perpendicular to the three-dimensional ROI and a horizontal direction on the three-dimensional ROI set by the first setting means. When,
And a second display means for displaying the projection data edited by the editing means together with the three-dimensional ROI as a positioning reference image. The magnetic resonance imaging apparatus according to claim 5.
A magnetic resonance imaging apparatus, further comprising: second setting means for setting a spatial position of the three-dimensional ROI on the reference image displayed by the second display means.

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