JP2017086728A - Magnetic resonance imaging apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To display images without a waiting time when a plurality of images are loaded and displayed.SOLUTION: An MRI device comprises: static magnetic field generation means for generating a uniform static magnetic field in a space accommodating a subject; gradient magnetic field generation means for generating a gradient magnetic field by superposing the static magnetic field; high frequency magnetic field generation means for generating a high frequency magnetic field to be emitted to the subject; detection means for detecting an NMR signal generated from the subject; and imaging means for imaging the detected NMR signal. When a plurality of images are loaded and displayed on a display, if the number of the plurality of images is equal to or more than a specified number, at least a part of compressed images of the plurality of images is displayed on the display until all the images are loaded.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a magnetic resonance imaging (hereinafter referred to as “MRI”) apparatus, and more particularly to a technique for enabling an image to be displayed without waiting time when a plurality of images are loaded and displayed.

  The MRI device measures NMR signals generated by the spins of the subject, especially the tissues of the human body, and visualizes the form and function of the head, abdomen, limbs, etc. in two or three dimensions Device. In imaging, the NMR signal is given different phase encoding depending on the gradient magnetic field, frequency-encoded, and measured as time series data. The measured NMR signal is reconstructed into an image by two-dimensional or three-dimensional Fourier transform.

  On the other hand, in MRI, a plurality of images for a plurality of regions of a subject acquired by multi-station / multi-slice imaging are classified based on one attribute selected from a plurality of attributes of each image, A plurality of images belonging to each category are aligned based on at least one of the attributes not selected, and displayed on the display in the aligned order (see, for example, Patent Document 1).

JP 2009-101205 A

  However, in the technique described in Patent Document 1, when displaying a large number of images obtained by multi-station / multi-slice imaging on a display so that an operator can view them, it takes time to load an image until the first image is displayed. There is a problem that it takes.

  Accordingly, an object of the present invention is to provide an MRI apparatus capable of displaying an image without waiting for image loading when displaying a large number of images on a display.

  In order to achieve the above object, the present invention comprises a static magnetic field generating means for generating a uniform static magnetic field in a space for accommodating a subject, a gradient magnetic field generating means for generating a gradient magnetic field by superimposing the static magnetic field, An MRI apparatus comprising: a high-frequency magnetic field generating means for generating a high-frequency magnetic field for irradiating the subject; a detecting means for detecting an NMR signal generated from the subject; and an imaging means for imaging the detected NMR signal When a plurality of images are loaded and displayed on the display when the number of images is equal to or greater than the prescribed number, at least a part of the plurality of images is loaded until all the images are loaded. An MRI apparatus characterized by displaying a compressed image on the display is provided.

  ADVANTAGE OF THE INVENTION According to this invention, the MRI apparatus which can reduce an operator's stress can be provided because an image can be browsed without the waiting time of image loading.

The whole block diagram of the MRI apparatus which has this invention. The image figure which is loading the image in the image browsing task. Example 1 flow chart Example 2 flow chart

  Hereinafter, preferred embodiments of the MRI apparatus of the present invention will be described in detail 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 uses a NMR phenomenon to obtain a tomographic image of a subject.As shown in FIG. 1, 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 generation system 3 includes a gradient magnetic field coil 9 that applies a gradient magnetic field in the three-axis directions of X, Y, and Z, which is a coordinate system (stationary coordinate system) of the MRI apparatus, and a gradient magnetic field that drives each gradient magnetic field coil. It consists of a power supply 10 and drives gradient magnetic field power supply 10 of each coil according to a command from sequencer 4 to be described later, thereby applying gradient magnetic fields Gx, Gy, Gz in the three axes of X, Y, and Z . 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 “RF pulse”) and a gradient magnetic field pulse in a predetermined pulse sequence, and operates under the control of the CPU 8 to collect tomographic image data of the subject 1. Various commands necessary for the transmission 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 RF pulse output from the high-frequency oscillator 11 is amplitude-modulated by the modulator 12 at the timing according to the command from the sequencer 4, and the amplitude-modulated RF 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 includes an external storage device such as an optical disk 19 and a magnetic disk 18, and a display 20 including a CRT or the like. When data from the receiving system 6 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 an external storage device On the magnetic disk 18 or the like.

  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 into which the subject 1 is inserted, in the case of 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. By imaging information on the spatial distribution of proton density and the spatial distribution of relaxation time in the excited state, the form or function of the human head, abdomen, limbs, etc. is imaged two-dimensionally or three-dimensionally.

  A first embodiment of the present invention will be described with reference to FIGS. FIG. 2 is an image diagram in which an image is loaded on the display 20 in this embodiment. Specifically, a compressed file of the head image is displayed.

  Next, the operation flow of the MRI apparatus according to the first embodiment will be described with reference to FIG.

(Step 101)
First, the operator presses a start button for loading an image, and the MRI apparatus starts loading an image from the magnetic disk 18.

(Step 102)
Next, the MRI apparatus determines whether the image compression file is linked to the image stored on the magnetic disk 18. If it exists, the process proceeds to step 103. If it does not exist, the process proceeds to step 105.

(Step 103)
In step 102, if the image compression file is linked to the image, the image compression file is displayed on the display 20.

(Step 104)
The MRI apparatus displays a warning message on the display 20 that the currently displayed image is a compressed image file, and proceeds to step 110.

(Step 105)
The MRI apparatus determines whether the number of images stored on the magnetic disk 18 is greater than the specified number. That is, the MRI apparatus stores a threshold value for the number of images that can be loaded at a time as the prescribed number, and the MRI apparatus is based on whether the number of images displayed on the magnetic disk 18 is greater or smaller than the threshold value. To determine whether or not to create a compressed image file. If the specified number is exceeded, the process proceeds to step 106, and if it is less than the specified number, the process proceeds to step 113.

(Step 106)
The MRI apparatus creates an image compression file for all of the plurality of images stored on the magnetic disk 18.

(Step 107)
The MRI apparatus stores the compressed image file created in step 106 on the magnetic disk 18.

(Step 108)
The compressed image file stored in step 107 is displayed on the display 20.

(Step 109)
The MRI apparatus displays a warning message on the display 20 that the currently displayed image is an image compression file.

(Step 110)
The MRI apparatus determines whether the image loading process is completed. If completed, go to step 111. If not completed, wait for a while and repeat step 110.

(Step 111)
The MRI apparatus switches the image compressed file to a pixel image (an uncompressed file).

(Step 112)
The warning message displayed on the display 20 is closed.

(Step 113)
The image stored in the magnetic disk 18 is displayed as it is.

  According to the above embodiment, when it takes time to display the image stored in the magnetic disk 18 as it is, the compressed file is displayed earlier, so that the irritation felt by the operator can be reduced.

  Next, Example 2 will be described with reference to FIG. Next, the operation flow of the MRI apparatus according to the second embodiment will be described with reference to FIG.

(Step 201)
The MRI apparatus starts imaging.

(Step 202)
The MRI apparatus uses the echo signal obtained in step 201 to create a pixel image.

(Step 203)
The MRI apparatus checks the number of images generated in step 202, and determines whether the number is the specified number or more.

(Step 204)
The MRI apparatus creates an image compression file if the number is greater than the prescribed number in step 203.

(Step 205)
The MRI apparatus stores the compressed image file created in step 204 on the magnetic disk 18.

  According to the above-described embodiment, since the image compression file is created simultaneously with the imaging, it is possible to provide an MRI apparatus that can display the image compression file immediately when the operator loads the image.

  2 Static magnetic field generation system, 3 Gradient magnetic field generation system, 5 Transmission system, 6 Reception system, 7 Signal processing system, 4 Sequencer, 8 Central processing unit (CPU)

Claims (1)

  A static magnetic field generating means for generating a uniform static magnetic field in a space for accommodating a subject, a gradient magnetic field generating means for generating a gradient magnetic field by superimposing the static magnetic fields, and a high frequency for generating a high-frequency magnetic field for irradiating the subject In a magnetic resonance imaging apparatus comprising a magnetic field generating means, a detecting means for detecting an NMR signal generated from the subject, and an imaging means for imaging the detected NMR signal, a plurality of images are loaded. When displaying on the display, if a plurality of images are a predetermined number or more, displaying at least a part of the compressed images of the plurality of images on the display until all the images are loaded. Features.

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