JP6203610B2 - Magnetic resonance imaging system - Google Patents

Description

  The present invention relates to a magnetic resonance imaging (hereinafter referred to as “MRI”) apparatus, and more particularly to an MRI apparatus provided with means for improving the setting efficiency of imaging parameter values.

  The MRI apparatus measures NMR signals generated by nuclear spins constituting a subject, particularly a human tissue, and images the form and function of the head, abdomen, limbs, etc. two-dimensionally or three-dimensionally. Device. In imaging, the NMR signal is given different phase encoding depending on the gradient magnetic field and is frequency-encoded to be measured as time series data. The measured NMR signal is reconstructed into an image by two-dimensional or three-dimensional Fourier transform.

  The image quality and imaging time of the reconstructed image in magnetic resonance imaging vary greatly depending on the pulse sequence used for imaging, but even for the same type of pulse sequence, the setting values of the imaging parameters (field-of-view / pulse repetition time (TR) A large difference occurs due to differences in echo time (TE), inversion recovery time (TI), slice thickness, number of slices, number of imaging matrices, number of signal additions, and the like.

  Therefore, the operator considers the imaging time in order to reduce the burden on the subject, and in order to obtain an image that can be accurately diagnosed by the doctor, the imaging time, disease type, diagnostic site, and imaging for each subject Therefore, it is necessary to set the value of the imaging parameter in detail in consideration of this area.

  Japanese Patent Laid-Open No. 2004-151867 calculates another imaging parameter that can be changed to maintain the input value and a candidate for the value when imaging using the input imaging parameter value is impossible, and the other imaging parameter And an MRI apparatus for displaying the value candidates on the display means.

JP 2006-280820 A

  However, in the prior art described in Patent Document 1, all the imaging parameters need to be calculated even when only a small number of imaging parameter changes are required when the operator finely sets the imaging parameter values. In some cases, other imaging parameters other than the small number of parameters to be changed are automatically changed at the same time. For example, when it is desired to shorten the imaging time, which is one of the imaging parameters, the operator needs to change whether to shorten the pulse repetition time (TR) or reduce the number of measurement points (Phase) in the phase direction. However, in accordance with the change, other imaging parameters may be automatically changed.

  Even when the operator wants to return to the imaging parameters set immediately before the change of the imaging parameters, other imaging parameters may be automatically changed simultaneously by calculation of all imaging parameters, The imaging parameter values could not be returned efficiently as desired by the operator.

  Therefore, an object of the present invention is to provide an MRI apparatus equipped with a function capable of efficiently returning a set imaging parameter to an imaging parameter set before the setting.

  In order to achieve the above object, a magnetic resonance imaging apparatus according to the present invention receives a high frequency irradiation unit that irradiates a subject placed in a static magnetic field space with a high frequency, and a nuclear magnetic resonance signal emitted from the subject. Stores a signal receiving unit, an arithmetic processing unit that performs processing on the received nuclear magnetic resonance signal to reconstruct a tomographic image of a subject, a display unit that displays a tomographic image, and imaging parameters required for imaging the tomographic image A storage unit, and the display unit includes a history display area for displaying an input history of the input imaging parameter, and an imaging parameter setting area for setting the imaging parameter. The initial imaging value and the changed imaging parameters that have changed the initial value are stored, and the changed imaging parameters are listed in the history display area in the order of the changes and displayed in the history display area. From the rear imaging parameters, by selecting the imaging parameters after the desired change by the operator, characterized by having a function to return the setting values of the imaging parameters up to the point of changing the selected after-imaging parameters.

  According to the present invention, it is possible to efficiently return the set imaging parameter to the imaging parameter set before the setting. In particular, it is possible to efficiently set desired imaging parameters by comparing quality parameters.

It is a figure which shows an example of the whole outline | summary of the MRI apparatus which concerns on this invention. 6 is a diagram illustrating initial values of imaging parameters according to Embodiment 1. FIG. 6 is a diagram illustrating an example of a display screen according to Embodiment 1. FIG. 6 is a flowchart illustrating imaging parameter input processing according to the first embodiment. 6 is a flowchart illustrating history display processing according to the first embodiment. 6 is a flowchart illustrating history selection processing according to the first embodiment. 6 is a diagram illustrating an example of a display screen after an item is selected from an imaging parameter input history list according to Embodiment 1. FIG. It is a figure which shows an example of a recommended parameter window. 10 is a flowchart illustrating imaging parameter input processing according to the second embodiment. 12 is a flowchart illustrating history display processing according to the second embodiment. 10 is a diagram illustrating an example of a display screen according to Embodiment 2. FIG. 10 is a flowchart showing a Suggestion button pressing process according to the second embodiment. 12 is a flowchart illustrating history parameter name input processing according to the second embodiment.

  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 the MRI apparatus according to the present invention will be described. FIG. 1 is a diagram showing an example of an overall outline 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 gradient magnetic fields in the three-axis directions of X, Y, and Z, which are coordinate systems (stationary coordinate systems) of the MRI apparatus, and gradient magnetic fields that drive the respective gradient magnetic field coils. The gradient magnetic field Gx, Gy, Gz is applied in the three axial directions of X, Y, and Z by driving the gradient magnetic field power supply 10 of each coil in accordance with 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 unit 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 a timing according to a 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 and a signal amplifier 15 on the receiving side. And a quadrature 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 a timing according to a 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 made up of a CRT or the like. When data from the reception 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 is used to input various control information of the MRI apparatus and control information of processing performed by 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 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.

First, Embodiment 1 of the present invention will be described below with reference to the drawings.
FIG. 2 is a diagram illustrating an example of initial values of imaging parameters according to the first embodiment. In this figure, TR (pulse repetition time) is 30.0, TE (echo time) is 16.5, FOV (imaging field of view) is 250, Multi Slice (number of slices) is 1, Band Width (frequency band of received signal) is 60.0 The initial values of the respective imaging parameters are displayed on the screen of the display 20.

  Next, a case where the initial value is changed as follows will be described. That is, TR is changed from 30.0 to 68.0, TE is changed from 16.5 to 15.3, FOV is changed from 250 to 256, Multi Slice is changed from 1 to 4, and Band Width is changed from 60.0 to 65.5.

FIG. 3 shows a display screen on which data including the imaging parameter after the change is displayed on the screen of the display 20.
The display screen shown in FIG. 3 is shown on the right side of the screen, the captured image 29, the input parameters of the input imaging parameters, and the imaging parameter input history list 31 in which the quality parameters corresponding to the input items are displayed. The input parameter display list 32, and “Start” and “Stop” buttons for starting or stopping the imaging scan.
The imaging parameter input history list 31 may be displayed superimposed on a part of the captured image 29.

The imaging parameter input history list 31 is an example in which the imaging parameter input history is displayed on a single screen and reset (changed) from the input parameter display list 32.
The input items shown in the imaging parameter input history list 31 are displayed from the bottom to the top in the order of changing the imaging parameters. That is, the first change is “Band Width” shown at the bottom, followed by “Multi Slice”. Such a change continues, and the change of “FOV” is the latest change in this table. Indicates that there is.

  From this figure, first, the value obtained by changing the Band Width from the initial value of 60.0 to 65.5 is displayed, and the quality parameter corresponding to the changed Band Width is automatically calculated and displayed. The display is performed in the same procedure until it reaches “FOV” displayed at the top.

  Note that “SNR”, “CNR”, “SAR”, “dB / dt”, and “Scan Time” are displayed as quality parameters. These parameters relate to the image quality of the captured image, the exposure safety to the subject 1, and the imaging time.

  For changing the imaging parameter, the changed numerical value is input to the corresponding part of the imaging parameter shown in the input parameter display list 32.

FIG. 4 is a flowchart showing imaging parameter input processing. With reference to this flowchart and FIG. 3, the flow of imaging parameter input processing when an operator inputs a desired imaging parameter value using the keyboard 24 in the operation unit 25 will be described.
(Step 101): All imaging parameters including the imaging parameters input by the operator immediately before are stored in the magnetic disk 18.
(Step 102): The imaging parameter input items (item name and value) input immediately before by the operator are stored in the magnetic disk 18.
(Step 103): Each quality parameter (SNR (signal-to-noise), CNR (contrast-to-noise), SAR (Specific Absorption Ratio; calorific value per unit mass absorbed by the human body when a high-frequency magnetic field is applied), The values of dB / dt (time change rate of gradient magnetic field) and Scan Time (imaging time) are stored in the magnetic disk 18.
The above is the description of the input processing flow of the imaging parameter input processing.

Next, FIG. 5 shows a flowchart showing the history display process. The flow of the history display process when the operator clicks the display / non-display switching button 30 in FIG. 3 using the trackball or the mouse 23 in the operation unit 25 will be described using this flowchart.
(Step 201): The item name (name of the imaging parameter) and the value of the input item stored in the magnetic disk 18 in Step 102 are loaded into the RAM 22.
(Step 202): It is determined whether the item name of the input item loaded in Step 201 and its value exist. If it does not exist (NO), the process is terminated. If it exists (YES), the process proceeds to step 203.
(Step 203): The item names and values of the input items loaded in Step 201 are displayed as the imaging parameter input history list 31 of FIG.
(Step 204): The values of the quality parameters (SNR, CNR, SAR, dB / dt, Scan Time) stored in the magnetic disk 18 in Step 103 are loaded into the RAM 22.
(Step 205): The values of the quality parameters (SNR, CNR, SAR, dB / dt, Scan Time) loaded in Step 204 are displayed as the imaging parameter input history list 31 in FIG.
(Step 206): The name and value of the imaging parameter of the input item of the next history are loaded into the RAM 22.
(Step 207): It is determined whether the item name and the value of the input item loaded in Step 206 exist. If it does not exist (NO), the process proceeds to step 208.
If it exists (YES), the process proceeds to step 203, and step 203 to step 207 are repeated until the next history does not exist.
(Step 208): In the history of the quality parameters (SNR, CNR, SAR, dB / dt, Scan Time) shown in the imaging parameter input history list 31 of FIG. dB / dt and Scan Time highlight the smallest number. When there are a plurality of values to be highlighted, all the values to be highlighted are highlighted. In this figure, the numbers to be highlighted in the table are displayed in a Gothic character with a large number of points.
The above is the description of the flow of the history display process.

  Next, when the operator wants to return the input items in the imaging parameter input history list 31 in FIG. 3 to the previously input items using the flowchart in FIG. 6 and the display screen in FIG. A history selection processing flow when an item to be returned on the list is selected by double-clicking using the trackball in the operation unit 25 or the mouse 23 will be described.

The configuration of the display screen in FIG. 7 is the same as the configuration shown in FIG.
(Step 301): All the imaging parameters stored in the magnetic disk 18 in Step 101 are loaded into the RAM 22.
(Step 302): All the imaging parameters loaded in Step 301 are displayed in the imaging parameter input area of the input parameter display list 32 of FIG.
(Step 303): The history newer than the item selected by the operator is canceled from the magnetic disk 18.
(Step 304): The contents canceled in step 303 are reflected in the imaging parameter input history list of the imaging parameter input history list 31 of FIG.

  In the example of the flowchart, the item selected by the operator is the input item “FOV” shown at the top of FIG. Accordingly, in FIG. 7, the quality parameter corresponding to the input item “FOV” is canceled. At the same time, it can be seen that the value 256 of “FOV” has returned to the initial value 250 before the change, as shown in the input parameter display list 32.

In this figure, the uppermost part of the imaging parameter input history list 31, that is, the change of the input item that was changed most recently, has been described. For example, when the input item two changes before the latest change is changed, that is, When changing “TE” in the third row from the top row of the imaging parameter input history list 31, the “TR” and “FOV” changed after the change of this item are simultaneously canceled and returned to the initial values.
The above is the description of the history selection process flow.
According to the present embodiment, it is possible to efficiently return the set imaging parameter to the imaging parameter set before the setting. In particular, there is an effect that a desired imaging parameter can be efficiently set by comparing quality parameters.

Next, Embodiment 2 of the present invention will be described below with reference to the drawings.
Similar to the first embodiment, the input history of the imaging parameters is displayed and set on one screen, but the difference from the first embodiment is as follows.

  That is, simultaneously with the input of imaging parameters, the calculation results of all imaging parameters are presented to the operator, and the display and setting of the recommended parameter window shown in FIG. 8 are different. Also, the history of an arbitrary imaging parameter is displayed from the imaging parameter input history list 31 of FIG.

Hereinafter, only different portions will be described, and description of the same portions will be omitted.
The flow of the imaging parameter input process when the operator inputs a desired imaging parameter value using the keyboard 24 in the operation unit 25 will be described with reference to the flowchart of FIG.
(Step 101): The same processing as described in FIG.
(Step 102): The same processing as described in FIG.
(Step 401): It is determined whether or not the recommended parameter window shown in FIG. If the display does not exist (NO), the process proceeds to step 103. If the display exists (YES), the process proceeds to step 402.
(Step 402): The display content of the recommended parameter window is stored in the magnetic disk 18.
(Step 103): The same processing as described in FIG.
The above is the description of the input processing flow of the imaging parameter input processing.

Next, the flow of the history display process when the operator clicks the display / non-display switching button 30 of FIG. 3 using the trackball or the mouse 23 in the operation unit 25 will be described using the flowchart of FIG. .
(Step 201): It is the same as the process described in FIG.
(Step 202): The same processing as described in FIG.
(Step 203): This is the same as the processing described in FIG.
(Step 501): The display content of the recommended parameter window stored in the magnetic disk 18 in Step 402 is loaded into the RAM 22.
(Step 502): It is determined whether or not the display content of the recommended parameter window loaded in Step 501 exists. If it does not exist (NO), the process proceeds to step 204. If it exists (YES), the process proceeds to step 503.
(Step 503): A button indicating that the recommended parameter window has been displayed is displayed (Suggestion button 33 shown in FIG. 11).
(Step 204): This is the same as the processing described in FIG.
(Step 205): This is the same as the processing described in FIG.
(Step 206): The same processing as described in FIG.
(Step 207): Same as the processing described in FIG.
(Step 208): The same processing as described in FIG.
The above is the description of the flow of the history display process.

FIG. 11 is a diagram illustrating an example of a display screen according to the second embodiment.
The configuration of the display screen shown in FIG. 3 is almost the same, except that a Suggestion field is newly provided in the imaging parameter input history list 31 and a Suggestion button 33 is displayed as shown in FIG. Displayed in the Suggestion column. In addition, a column indicating a history parameter (in the drawing, the imaging setting condition 34 is illustrated) is newly provided in the quality parameter column of the imaging parameter input history list 31.

Next, when the operator clicks the Suggestion button 33 in FIG. 11 from the imaging parameter input history list 31 in FIG. 3 using the trackball or mouse 23 in the operation unit 25, using the flowchart in FIG. The flow of the Suggestion button pressing process will be described.
(Step 601): The display contents of Suggestion are loaded into the RAM 22.
(Step 602): Suggestion is displayed.
(Step 603): It is determined whether the operator has selected the Suggestion recommended parameter. If not selected (NO), the process is terminated. If it is selected (YES), the process proceeds to step 604.
(Step 604): All imaging parameters are loaded into the RAM 22.
(Step 605): The recommended parameters selected by the operator in Step 603 are reflected on all the imaging parameters loaded in Step 604.
(Step 606): All the imaging parameters reflecting the recommended parameters in Step 605 are displayed in the imaging parameter input area of the input parameter display list 32 of FIG.
(Step 607): History newer than the item selected by the operator is canceled from the magnetic disk 18.
(Step 608): The contents canceled in Step 607 are reflected in the imaging parameter input history list 31 of FIG.
The above is the description of the flow of the Suggestion button pressing process.

Next, referring to the flowchart of FIG. 13, the operator will explain the flow of input processing for inputting the history parameters of FIG. 11 from the imaging parameter input history list 31 of FIG. 3 using the keyboard 24 in the operation unit 25. To do. In this drawing, the imaging setting condition 34 is exemplified as the history parameter, and “ON” or “OFF” corresponding to each input item is shown. When the imaging setting condition 34 is “ON”, the current condition of the corresponding input item is used, and when it is “OFF”, the initial value of the corresponding input item is used.
(Step 701): The operator determines whether the history parameter of FIG. 11 exists in all the imaging parameters. If it does not exist (NO), the process is terminated. If it exists (YES), the process proceeds to step 702.
(Step 702): The imaging parameter corresponding to the history parameter name is loaded into the RAM 22.
(Step 703): The value of the history parameter loaded in Step 702 is displayed in the imaging parameter input history list 31 of FIG.
(Step 704): The history parameter of the next history is loaded into the RAM 22.
(Step 705): It is determined whether the history parameter loaded in Step 704 exists. If it does not exist (NO), the process is terminated. If it exists (YES), the process proceeds to step 703 and steps 703 to 705 are repeated until the next history does not exist.
The above is the description of the flow of the history parameter name input process.
In this embodiment, there is a Suggestion function. When an inappropriate quality parameter is generated when the imaging parameter is changed, the recommended parameter is presented, so that the operator can respond quickly and the imaging operation can be speeded up.

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 source, 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 detector, 17: A / D converter, 18: magnetic disk, 19: optical disk, 20: display, 21: ROM, 22: RAM, 23: trackball or mouse, 24: keyboard,
29: Captured image,
30: Display / non-display switch button for imaging parameter input history list,
31: Imaging parameter input history list,
32: Imaging parameter setting area,
33: Suggestion button,
34: History parameter name input area,
35: An imaging parameter setting area.

Claims (6)

A high-frequency irradiation unit that irradiates a subject placed in a static magnetic field space with a high frequency;
A signal receiver for receiving a nuclear magnetic resonance signal emitted from the subject;
An arithmetic processing unit that performs processing on the received nuclear magnetic resonance signal to reconstruct a tomographic image of the subject;
A display unit for displaying the tomographic image;
A storage unit that stores imaging parameters required for imaging the tomographic image,
The display unit includes a history display area for displaying an input history of the input imaging parameter, and an imaging parameter setting area for setting the imaging parameter,
The storage unit stores an initial value of the imaging parameter, and a changed imaging parameter after changing the initial value,
In the history display area, the changed imaging parameters are listed in the order of change,
By selecting a desired post-change imaging parameter from among the post-change imaging parameters displayed in a list in the history display area, the setting value of the imaging parameter can be obtained up to the time when the selected post-change imaging parameter is changed. A magnetic resonance imaging apparatus having a returning function.   The function for returning the set value of the imaging parameter returns all of the selected changed imaging parameter and the imaging parameter changed after the changed imaging parameter to an initial value by the arithmetic processing unit. 2. The magnetic resonance imaging apparatus according to 1.   The arithmetic processing unit determines whether or not the input post-change imaging parameter is within a preset changeable range, and can be changed when the post-change imaging parameter exceeds the changeable range. The magnetic resonance imaging apparatus according to claim 1, further comprising means for calculating other imaging parameter and its value candidates and performing a suggestion display in the history display area based on the calculation result.   The item name constituting the imaging parameter, a setting value of the item name, and a quality parameter of the tomographic image calculated based on the setting value are displayed in the history display area. Item 2. The magnetic resonance imaging apparatus according to Item 1.   5. The magnetic resonance imaging apparatus according to claim 4, wherein a value most suitable for an imaging condition is highlighted in the history display area from among quality parameters calculated for each of the changed imaging parameters. .   5. The magnetic resonance imaging apparatus according to claim 4, wherein the change of the imaging parameter is performed by inputting a setting value to be changed corresponding to the item name from the imaging parameter setting area.

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