JP2014151084A - Mri apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an MRI apparatus which allows an operator to accurately and easily set an imaging region or an imaging portion intended by the operator as ROI.SOLUTION: The MRI apparatus includes: a three-dimensional data acquisition section for acquiring three-dimensional data of an analyte by preparation imaging performed prior to main imaging; a positioning image generation section for generating a positioning projection image by projecting the three-dimensional data from a specified direction; a display section for displaying the positioning projection image; an interested region determination section for determining a three-dimensional interested region from two-dimensional information of an interested region frame set over the displayed positioning projection image and depth information of the positioning projection image included in the interested region frame; and a main imaging execution section for performing main imaging of the analyte for the set interested region.

Description

  Embodiments described herein relate generally to an MRI apparatus.

  An MRI apparatus is an apparatus that generates a subject image by applying a high-frequency magnetic field to a subject placed in a static magnetic field, detecting a magnetic resonance signal emitted from the subject by the application of the high-frequency magnetic field. When the subject is imaged by the MRI apparatus, a region of interest (hereinafter referred to as ROI (Region Of Interest)) to be an imaging range is designated, and the main imaging is performed on the designated ROI.

  In a general imaging procedure that has been performed in the past, a positioning image consisting of three cross-sectional images of an axial cross-sectional image, a coronal cross-sectional image, and a sagittal cross-sectional image is captured on a subject. The three cross-sectional images are displayed on the console display device. An operator such as an inspection engineer sets an ROI while using a mouse, a keyboard, or the like for the three-section positioning image displayed on the display device. The set ROI is displayed superimposed on the positioning image, and the ROI can be changed as necessary. When the ROI setting is completed, the main imaging is performed on the set ROI. In addition to this, a technique for setting a region-selective labeling pulse irradiation region on a positioning image in addition to an imaging target region has been studied (Patent Document 1, etc.).

JP 2012-16459 A

  However, each of the three cross-sectional images used as the positioning image is a two-dimensional image. For this reason, even if an attempt is made to set a desired ROI for an imaging region in which blood vessels and the like are complicated in a three-dimensional manner, it is difficult to grasp the three-dimensional structure from the positioning images of the three cross sections. In addition, there are cases where a tissue such as a blood vessel in the three-dimensional imaging space to be imaged is not included in the two-dimensional positioning image or is only partially included. For this reason, there has been a problem that the imaging region or imaging region intended by the operator is not accurately reflected in the ROI setting.

  Therefore, there is a demand for an MRI apparatus that can accurately and easily set an imaging region or an imaging region intended by an operator as an ROI.

  The MRI apparatus according to this embodiment includes a three-dimensional data acquisition unit that acquires three-dimensional image data of a subject by preparatory imaging performed before main imaging, and a projection image for positioning by projecting the three-dimensional image data from a specified direction. A positioning image generation unit that generates the positioning projection image, a display unit that displays the positioning projection image, two-dimensional information of the region of interest frame that is set on the displayed positioning projection image, and the region of interest frame A region-of-interest determination unit that determines a three-dimensional region of interest from the depth information of the positioning projection image included in the image, and a main imaging execution unit that performs main imaging of the subject with respect to the set region of interest; It is provided with.

The figure which shows the structural example of the MRI apparatus of embodiment. The functional block diagram which extracted the function relevant to the ROI setting of the MRI apparatus of embodiment. The figure which shows an example of the conventional display screen of a console display part. The flowchart which shows the operation example of the MRI apparatus which concerns on embodiment. The figure which shows typically the three-dimensional image data acquired by preparatory imaging. The figure which illustrates the projection direction of a MIP image. The figure which illustrates the MIP image corresponding to each projection direction. The figure which shows an example of the display screen which concerns on embodiment of a console display part. The figure explaining the determination method of the ROI depth range in all the designation modes. The figure explaining the determination method of the ROI depth range in partial designation | designated mode.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

(1) Overall Configuration FIG. 1 is a block diagram showing the overall configuration of an MRI (Magnetic Resonance Imaging) apparatus 1 in the present embodiment. The MRI apparatus 1 of the embodiment includes a magnet stand 100, a bed 200, a control cabinet component 300, a console 400, and the like.

  The magnet mount 100 includes a static magnetic field magnet 10, a gradient magnetic field coil 11, an RF coil 12, and the like, and these components are housed in a cylindrical casing. The bed 200 includes a bed body 20 and a top plate 21.

  On the other hand, the control cabinet component 300 includes a static magnetic field power supply 30, a gradient magnetic field power supply 31 (31x for X axis, 31y for Y axis, 31z for Z axis), RF receiver 32, RF transmitter 33, sequence controller 34, etc. It has. The console 400 is configured as a computer having a processor 40, a storage unit 41, an input unit 42, a display unit 43, and the like.

  The static magnetic field magnet 10 of the magnet mount 100 has a substantially cylindrical shape, and generates a static magnetic field in a bore (a space inside the cylinder of the static magnetic field magnet 10) that is an imaging region of a subject (patient). The static magnetic field magnet 10 incorporates a superconducting coil, and the superconducting coil is cooled to a very low temperature by liquid helium. The static magnetic field magnet 10 generates a static magnetic field by applying a current supplied from the static magnetic field power source 30 to the superconducting coil in the excitation mode, and then, when the permanent magnetic mode is entered, the static magnetic field power source 30 is disconnected. . Once in the permanent current mode, the static magnetic field magnet 10 continues to generate a large static magnetic field for a long time, for example, for one year or more. The static magnetic field magnet 10 may be configured as a permanent magnet.

  The gradient coil 11 also has a substantially cylindrical shape and is fixed inside the static magnetic field magnet 10. The gradient magnetic field coil 11 applies a gradient magnetic field to the subject in the X-axis, Y-axis, and Z-axis directions by a current supplied from a gradient magnetic field power supply (31x, 31y, 31z).

  The bed body 20 of the bed 200 can move the top plate 21 in the vertical direction, and moves the subject placed on the top plate 21 to a predetermined height before imaging. Thereafter, at the time of imaging, the top 21 is moved in the horizontal direction to move the subject into the bore.

  The RF coil 12 is also called a whole body coil, and is fixed inside the gradient magnetic field coil 11 so as to be opposed to each other with a subject interposed therebetween. The RF coil 12 irradiates the subject with an RF pulse transmitted from the RF transmitter 33, and receives a magnetic resonance signal emitted from the subject by excitation of hydrogen nuclei.

  The RF transmitter 33 transmits an RF pulse to the RF coil 12 based on an instruction from the sequence controller 34. On the other hand, the RF receiver 32 detects a magnetic resonance signal received by the RF coil 12 and transmits raw data obtained by digitizing the detected magnetic resonance signal to the sequence controller 34.

  The sequence controller 34 scans the subject by driving the gradient magnetic field power supply 31, the RF transmitter 33, and the RF receiver 32 under the control of the console 400. When the sequence controller 34 scans and receives raw data from the RF receiver 32, the sequence controller 34 transmits the raw data to the console 400.

  The console 400 controls the entire MRI apparatus 1. Specifically, imaging conditions and other various information and instructions are received by operating a mouse, a keyboard, etc. (input unit 42) such as a laboratory technician. Then, the processor 40 causes the sequence controller 34 to execute a scan based on the input imaging condition, and reconstructs an image based on the raw data transmitted from the sequence controller 34. The reconstructed image is displayed on the display unit 43 or stored in the storage unit 41.

  FIG. 2 is a functional block diagram in which, among various functions realized by the MRI apparatus 1 of the present embodiment, functions related to the setting of ROI are extracted.

  The imaging unit 500 images the subject according to the imaging conditions set on the console 400 and generates a captured image. The functions of the imaging unit 500 are realized by the image reconstruction process performed by the console 400 in addition to each component of the magnet mount 100 and the control cabinet component 300 shown in FIG.

  The preliminary imaging execution unit 501 of the imaging unit 500 executes preliminary imaging performed before the main imaging. Then, the 3D image acquisition unit 502 generates 3D image data of the subject from the data obtained by the preliminary imaging. This three-dimensional image data becomes original image data of a positioning image described later. The imaging method for the preparatory imaging is not particularly limited. For example, it is an MRA (Magnetic Resonance Angiography) imaging method for acquiring a three-dimensional blood vessel image.

  The positioning image generation unit 510 projects the 3D image data acquired by the 3D image acquisition unit 502 from a specified direction to generate a positioning projection image. The projection process here is, for example, a process in which a three-dimensional MRA image is projected by a maximum value projection method (Maximum Intensity Projection: MIP method) to draw a blood vessel, and this MIP process is performed by the MIP processing unit 512. The MIP processing is suitable when the three-dimensional MRA imaging method is a so-called bright blood method such as a TOF (Time Of Flight) method.

  On the other hand, when the 3D MRA imaging method is the black blood method, the blood vessel may be projected by a minimum value projection method (minimum intensity projection: MinIP method) instead of the MIP method. .

  The positioning projection image generated by the positioning image generation unit 510, for example, the positioning MIP image or the positioning MinIP image, is displayed on the screen of the display unit 43.

  A user such as a doctor or a laboratory technician designates an ROI using a positioning image such as an MIP image displayed on the display unit 43. Specifically, the ROI frame corresponding to the range of the ROI when viewed from the projection direction is displayed on the positioning image, and the position and size of the ROI frame are displayed on the user interface (input unit 42) such as a mouse. By adjusting using, a two-dimensional ROI viewed from the projection direction is set.

  The region-of-interest determination unit 521 of the imaging condition setting unit 520 inputs the two-dimensional ROI information set by the user, and inputs information related to the ROI depth range from the positioning image generation unit 510 to determine the three-dimensional ROI. . In addition to the above ROI, the imaging condition setting unit 520 sets imaging conditions necessary for actual imaging from various parameters input via the user interface 42 and the like.

  The main imaging execution unit 503 of the imaging unit 500 performs main imaging of the subject based on various imaging conditions determined or set by the imaging condition setting unit 520.

(2) Positioning Image Generation and ROI Setting Hereinafter, positioning image generation and ROI setting of the MRI apparatus 1 according to the present embodiment will be described. Before that, for comparison with the present embodiment, a conventional positioning image The generation and ROI setting will be briefly described.

  FIG. 3 is a diagram illustrating an example of a conventional display screen W0 of the display unit 43 of the console 400. In the series display field D1 in the lower left of the display screen W0, the imaging order of the series (referred to as an imaging unit when imaging a plurality of images continuously by a predetermined imaging method) is displayed together with the number and ID of each series. ing. A check mark “” on the left of the “series number 1000” column indicates that imaging of the series ID “Locator 3 Axis” has already been completed. Here, the imaging of “Locator 3 Axis” is imaging (three-section imaging for positioning) for acquiring a positioning image composed of three cross-sectional images of an axial cross-sectional image, a sagittal cross-sectional image, and a coronal cross-sectional image.

  On the other hand, the check mark “R” on the right side of the “series number 2000” field indicates that the imaging condition of the series ID “AX T1W (SE)” is displayed in the imaging condition display field D2 at the lower right of the display screen W0. It is shown that. Since the imaging of “series number 2000” has not been executed yet, the imaging condition in the imaging condition display field D2 is currently set or can be changed.

  A thumbnail image display field D3 is provided immediately above the imaging condition display field D2. In the thumbnail image display field D3, captured images are displayed as thumbnail images.

  In the upper part of the display screen W0, an image display field D4 for enlarging the captured image is provided. In the display example of FIG. 3, three cross-sectional positioning images (axial cross-sectional image Im1, sagittal cross-sectional image Im2, and coronal cross-sectional image Im3) captured by the series number 1000 are displayed.

  Conventional ROI setting is performed by superimposing and displaying the ROI frame on the above-described three-section positioning image, and adjusting the position and size of the ROI frame by a mouse or the like or numerical input. However, each of the three cross-sectional images (axial cross-sectional image Im1, sagittal cross-sectional image Im2, and coronal cross-sectional image Im3) used as a conventional positioning image is a two-dimensional image. For this reason, there is a problem that it is difficult to grasp the three-dimensional structure from the positioning images of the three cross sections even if an attempt is made to set a desired ROI for an imaging region where blood vessels and the like are complicatedly arranged in a three-dimensional manner. In addition, there are cases where a tissue such as a blood vessel in the three-dimensional imaging space to be imaged is not included in the two-dimensional positioning image or is only partially included. For this reason, there has been a problem that the imaging region or imaging region intended by the operator is not accurately reflected in the ROI setting.

  The method of generating the positioning image and setting the ROI of the MRI apparatus 1 according to the present embodiment solves the above-described conventional problems, and will be specifically described below.

  FIG. 4 is a flowchart showing an operation example of the MRI apparatus 1 according to the present embodiment. In step ST0, the three cross sections of the subject are imaged in the same manner as in the prior art to obtain a three cross section image. Based on these three cross-sectional images, it is confirmed that the imaging region of the subject to be imaged is approximately in the vicinity of the center of the magnetic field.

  Next, in step ST1, preparatory imaging for acquiring a positioning image in the present embodiment is performed. Note that in the MRI apparatus 1 of the present embodiment, since the detailed ROI is set based on the positioning image acquired by the preparation imaging, the conventional three-section imaging in step ST0 may be omitted.

  In step ST2, 3D image data is generated from the data acquired by the preparatory imaging. This three-dimensional image data becomes original image data of a positioning projection image to be described later. The imaging method for the preparatory imaging is not particularly limited. For example, it is an MRA (Magnetic Resonance Angiography) imaging method for acquiring a three-dimensional blood vessel image. More specifically, for example, imaging methods such as TOF (Time Of Flight) method, PC (Phase Contrast) method, FBI (Fresh Blood Imaging) method, and TimeSLIP (Time-Spatial Labeling Inversion Pulse) method.

  FIG. 5 is a diagram schematically showing three-dimensional image data acquired by the preparatory imaging. The three-dimensional image data illustrated in FIG. 5 is image data obtained by imaging a three-dimensional volume V indicated by a rectangular parallelepiped with a plurality of slices, and uses an axial cross section (XY cross section) of the subject as a slice plane. In the illustration of FIG. 5, the X direction is the sagittal direction (direction perpendicular to the sagittal section), and the Y direction is the coronal direction (direction perpendicular to the coronal section). Further, in FIG. 5 (and each figure after FIG. 5), it is assumed that only one blood vessel branched in the middle exists in the three-dimensional image data corresponding to the three-dimensional volume V, but this is only described. This is a blood vessel model for convenience, and a large number of blood vessels may actually exist.

  In step ST3 of FIG. 4, a projection image is generated by projecting the acquired three-dimensional image data from a plurality of designated directions. The projection image is typically an MIP image or a MinIP image, but will be described below using an MIP image as an example.

  FIGS. 6A and 6B are diagrams illustrating the projection direction of the MIP image, and FIG. 7 is a diagram illustrating the MIP image corresponding to each projection direction.

  6A and 6B, three-dimensional image data (same as in FIG. 5) acquired by the preliminary imaging is obtained from four directions (direction A, direction B, direction C, direction D) perpendicular to the Z axis. The projection is illustrated. FIG. 7 illustrates four MIP images (Ima, Imb, Imc, and Imd) respectively corresponding to these four directions. In this example, the direction A is the sagittal direction and the direction D is the coronal direction.

  The above four directions are merely examples for explanation, and the directions and numbers are arbitrary. For example, an XY plane including the center of the three-dimensional image data may be projected in a direction that rotates 360 degrees every other degree toward the center of the three-dimensional image data. In this case, 360 MIP images from different projection directions are generated. The MIP image generated in this way is displayed on the display screen W1 of the display unit 43 of the console 400.

  FIG. 8 is a diagram showing a display example of the display screen W1 according to the present embodiment. A first difference from the conventional display screen W0 (FIG. 3) is that a plurality of thumbnail images respectively corresponding to the plurality of MIP images generated in step ST3 are displayed in the thumbnail image display field D3. These thumbnail images correspond to a plurality of projection directions, and in the example of FIG. 8, four MIP images projected from the four directions A, B, C, and D are displayed as thumbnail images. . If there are a large number of projection directions and not all of them can be displayed, the thumbnail image display field D3 may be scrolled and displayed cyclically. The thumbnail image display processing corresponds to step ST4 in FIG.

  A second difference from the conventional display screen W0 is that one thumbnail image selected from a plurality of thumbnail images displayed in the thumbnail image display column D3 is enlarged and displayed in the image display column D4. This is a point used as a positioning image for setting. In the example of FIG. 8, the MIP image Ima projected from the direction A (sagittal direction) is enlarged and displayed in the image display field D4 as a positioning image. The enlarged display of the selected MIP thumbnail image corresponds to step ST5 in FIG.

  Note that it is up to the user to select which thumbnail image to select. By observing the plurality of thumbnail images displayed in the thumbnail image display field D3, the user can grasp the running state of the blood vessel in the depth direction, which was not obtained with the two-dimensional cross-sectional image. The positioning image most suitable for the ROI setting can be selected.

  As another difference from the conventional display screen W0, an “all designation” button B1 and a “partial designation” button B2 are provided above the thumbnail image display field D3.

  In the series display column D1 in the lower left of FIG. 8, the imaging for acquiring the three cross-sectional images in step ST0 corresponds to the imaging of the series 1000 (“Locator 3 Axis”), and the preliminary imaging in step ST1 is the imaging of the series 2000. ("MRA 3D"). The series 3000 imaging (“SG T1W (SE)”) and the series 4000 imaging (“AX T2W (FSE)”) are the main imaging.

  FIG. 8 shows the display screen in which the preparatory imaging of the series 2000 is completed and the imaging conditions of the next main imaging (series 3000) are set from the MIP image based on the MRA three-dimensional image data acquired by the preliminary imaging. W1.

  When the positioning image Ima is enlarged and displayed in step ST5, the user sets an ROI frame as shown by a bold line on the positioning image Ima. By setting the ROI frame, the ROI can be specified for two dimensions of the three-dimensional ROI. Specifically, the plane perpendicular to the projection direction of the selected positioning image Ima is determined as the slice plane, and the ROI two-dimensional information, that is, the slice plane phase, is determined from the ROI frame information set on the positioning image Ima. The FOV (Field Of View) in each of the encoding direction (PE direction) and the readout direction (RO direction) can be automatically determined.

  In step ST6 of FIG. 4, in addition to the ROI two-dimensional information determined as described above, the apparatus automatically determines the depth range of the ROI and determines the three-dimensional ROI.

  The ROI depth range determination method includes, for example, an all designation mode and a partial designation mode. The full designation mode and the partial designation mode can be designated by the user clicking either the “full designation” button B1 or the “partial designation” button B2 shown in FIG.

  FIGS. 9A to 9C are diagrams illustrating a method for determining the ROI depth range in the all designation mode. In the all designation mode, as shown in FIGS. 9B and 9C, the entire depth range of the three-dimensional image data (original data of the MIP image for setting the ROI frame) viewed from the projection direction is set to the ROI depth. Determine as a range. According to the ROI determination method in the all-designation mode, the blood vessel visible in the MIP image can be surely stored in the three-dimensional ROI, and the processing is simple.

  If either one of the number of slices or slice thickness is set in advance, the other can be automatically determined from the ROI depth range (depth width) automatically determined above.

  On the other hand, FIGS. 10A to 10C are diagrams illustrating a method for determining the ROI depth range in the partial designation mode. In the partial designation mode, as shown in FIGS. 10B and 10C, when viewed from the projection direction, the range in the depth direction of the blood vessel existing in the ROI frame is determined as the depth range of the ROI. For example, as shown in FIG. 10B, when the blood vessel exists only in a narrow range in a part of the ROI depth direction, the narrow range is determined as the ROI depth range. In addition, as shown in FIG. 10C, when a blood vessel is spread over a considerably wide range in the depth direction of the ROI, a region where the blood vessel does not exist is not included in the depth range while covering the widened range. Determine the ROI depth range.

  Note that the depth position information of the blood vessel rendered in the MIP image can be acquired by referring to the MIP processing unit 512. Therefore, if the ROI frame is set, the range in the depth direction of the blood vessel existing in the ROI frame can be obtained from the ROI frame information and the blood vessel depth position information.

  Although the ROI determination method in the partial designation mode is somewhat complicated, the width in the depth direction of the ROI can be suppressed to a necessary minimum width where a blood vessel exists. For this reason, if the slice thickness is the same, the number of slices can be reduced as compared with the all designation mode, and the imaging time can be shortened.

  In step ST7, the main imaging is executed based on the three-dimensional ROI determined as described above.

  Note that the ROI depth range determined by the apparatus in the full designation mode or the partial designation mode can be changed by a user operation.

  Further, instead of the automatic determination of the ROI depth range by the apparatus, the user may set ROI three-dimensional information. In this case, for example, two MIP images viewed from two projection directions orthogonal to each other may be displayed in the image display field D4, and ROI frames may be set for the two MIP images, respectively. Even in this case, since the running state of the blood vessel in the three-dimensional space is drawn without omission in the two positioning MIP images, the desired ROI is set as compared with the conventional ROI setting using a two-dimensional three-section. Can be set accurately.

  As described above, according to the MRI apparatus 1 of the embodiment, a desired ROI can be accurately and easily set as an ROI even for an imaging region in which blood vessels and the like are complicated in a three-dimensional manner. .

  Although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are also included in the invention described in the claims and the equivalents thereof.

DESCRIPTION OF SYMBOLS 1 MRI apparatus 43 Display part 500 Imaging part 502 Three-dimensional image acquisition part 503 This imaging execution part 510 Positioning image generation part 512 MIP processing part 520 Imaging condition setting part 521 Area of interest determination part

Claims (7)

A three-dimensional data acquisition unit that acquires three-dimensional image data of the subject by preparatory imaging performed before the main imaging;
A positioning image generator that projects the three-dimensional image data from a specified direction to generate a positioning projection image;
A display unit for displaying the positioning projection image;
A three-dimensional region of interest is determined from the two-dimensional information of the region-of-interest frame set over the displayed projection image for positioning and the depth information of the positioning-projection image included in the region-of-interest frame. A region of interest determination unit,
A main imaging execution unit that performs main imaging of the subject with respect to the set region of interest;
An MRI apparatus characterized by comprising: The positioning projection image is a MIP (Maximum Intensity Projection) image of a three-dimensional MRA image in which blood vessels are depicted.
The MRI apparatus according to claim 1. The positioning projection image is a MinIP (Minimum Intensity Projection) image of a three-dimensional MRA image in which blood vessels are depicted.
The MRI apparatus according to claim 1. The region-of-interest determination unit determines a depth range of the three-dimensional image data viewed from the projection direction as a depth range of the three-dimensional region of interest;
The MRI apparatus according to claim 1. The region-of-interest determination unit determines a range in the depth direction of the blood vessel existing in the region of interest frame as the depth range of the three-dimensional region of interest when the blood vessel is viewed from the projection direction;
The MRI apparatus according to claim 2 or 3, wherein The image generation unit
Generating a plurality of positioning images corresponding to a plurality of designated directions;
The display unit
Displaying a plurality of the positioning projection images as thumbnail images, while enlarging and displaying one designated thumbnail image as a positioning projection image to be set for the region of interest frame;
The MRI apparatus according to claim 1. The specified direction can be changed,
The image generation unit generates a positioning projection image projected from a new specified direction each time the specified direction is changed.
The MRI apparatus according to claim 1.

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