Patent Publication Number: US-2016231396-A1

Title: Magnetic resonance imaging apparatus and imaging parameter setting assisting method

Description:
TECHNICAL FIELD 
     The present invention relates to a magnetic resonance imaging (hereinafter, referred to as “MRI”) apparatus. 
     BACKGROUND ART 
     An MRI apparatus two-dimensionally or three-dimensionally measures Nuclear Magnetic Resonance (NMR) signals generated by an atomic nucleus spin that comprises tissues of an object, particularly a human body to image forms and functions of the head, abdomen, extremities, and the like. During imaging, the NMR signals are provided with phase encodings different depending on the gradient magnetic field, frequency-encoded, and measured as time-series data. The measured NMR signals are two-dimensionally or three-dimensionally Fourier-transformed in order to reconstruct an image. 
     Normally, a plurality of pulse sequences are used for an object in a series of imaging operations, and high-frequency magnetic field pulses (hereinafter, referred to as “RF pulse”) are continuously irradiated. Therefore, an MRI apparatus can store pulse sequence combinations and an irradiation order to be used for a series of irradiations. Such pulse sequence combinations are referred to as protocols. 
     Although reconstruction image quality, an imaging time, and a Specific Absorption Rate (SAR) in magnetic resonance imaging are greatly different depending on the pulse sequence to be used for imaging, great differences are caused by differences of the imaging parameter setting values (a field of view (FOV), a pulse repetition time (TR), an echo time (TE), an inversion time (TI), a slice thickness, the number of slices, the number of imaging matrices, the number of signal additions, and the like) even in case of a similar pulse sequence. 
     Therefore, in consideration of a burden on an object, an operator of an MRI apparatus is required to meticulously set imaging parameter values by considering, for example, physical conditions, an imaging time, a disease type, a diagnosis site, and imaging region in order to acquire an image that allows a doctor to perform an accurate diagnosis. 
     In the non-patent literature 1, an apparatus state is divided into three stages, and they are specified as a normal operation mode, a first level controlled operating mode, and a second level controlled operating mode starting from a lower SAR according to a time average SAR value while a gradient magnetic field is being applied. In order to reduce a burden on an object, an object generally has to be imaged in the normal operation mode or the first level controlled operating mode, and a pregnant object and an object having difficulty adjusting the body temperature have to be imaged only in the normal operation mode. 
     There are various interrelationships between each imaging parameter and a SAR. For example, when a pulse repetition time (TR) is shortened, a time-average SAR is increased. An operator is required to search and set an optimal imaging parameter value in an allowable operation mode under restriction based on such an interrelationship. 
     As shown in the non-patent literature 1, it is required to perform imaging when an apparatus state is a normal operation mode or a first level controlled operating mode in order to reduce a burden on an object. Therefore, if a SAR in each pulse sequence or a magnetic field variation rate (dB/dt) per unit time t of a magnetic flux density B exceeds an allowable value in an operation mode capable of imaging, imaging parameters need to be adjusted in order to reduce these rates. 
     Although there is no problem if imaging parameters were adjusted for a stored protocol so that SAR and dB/dt values are within those allowed in an operation mode capable of imaging in a pulse sequence, a SAR particularly varies depending on the physical characteristics (height, weight, and the like) of an object, and there are some cases where the SAR of the stored protocol is a value outside a range of the operation mode capable of imaging. 
     Also, in an examination using a contrast agent, it is necessary to reduce a SAR in each pulse sequence because there are restrictions where a pulse sequence order cannot be changed, where a waiting time cannot be added between pulse sequences, and the like. Additionally, in an examination for examining a plurality of sites such as a contrast examination for lower extremities, it is required to adjust imaging parameters to set conditions capable of imaging so as not to change the contrast of an image to be acquired in each pulse sequence. Therefore, it is required to adjust imaging parameters in a pulse sequence so as not to exceed SAR and dB/dt allowable values and so as to maintain image quality required for the examination. 
     The patent literature 1 discloses an MRI apparatus having a display unit that displays setting values of imaging parameters interrelated with each other and the settable ranges (variable range) and additionally changes and re-displays the settable ranges (variable range) of the other related imaging parameter values according to a change of an imaging parameter value. 
     CITATION LIST 
     Patent Literature 
     
         
         PTL 1: Unexamined Patent Publication No. 6-90926 
       
    
     Non-Patent Literature 
     
         
         NPTL 1: “IEC 60601-2-33 Ed. 3: Medical electrical equipment—Part 2-33: Particular requirements for the basic safety and essential performance of magnetic resonance equipment for medical diagnosis” by International Electrotechnical Commission 
       
    
     SUMMARY OF INVENTION 
     Technical Problem 
     Although the purpose of the technique described in the patent literature 1 is to suggest specific values of imaging parameters at which the imaging parameters become conditions capable of imaging for one pulse sequence, an operator is required to repeatedly check whether or not the imaging parameters become conditions capable of imaging by setting specific parameters in order to reduce a SAR and a dB/dt. 
     Therefore, the purpose of the present invention is to provide an MRI apparatus that can adjust imaging parameters more efficiently. 
     Solution to Problem 
     The magnetic resonance imaging apparatus related to the present invention is comprised of a static magnetic field generation source that generates a static magnetic field in a space accommodating an object, a gradient magnetic field generating unit that generates a gradient magnetic field to be superimposed on the static magnetic field, a high-frequency magnetic field generating unit for irradiating a high-frequency magnetic field pulse to the object, a signal detection unit that detects a nuclear magnetic resonance signal to be generated from the object, a sequencer that controls the static magnetic field generation source; the gradient magnetic field generating unit; the high-frequency magnetic field generating unit; and the signal detection unit according to a pulse sequence, and a control unit that has a storage device; an input device; an output device; and a CPU, when a control subject is input based on an input operation, the control unit displays suggestions of imaging parameters related to the control subject and change directions of the imaging parameters, and when the displayed imaging parameters are changed, the control unit further calculates values of the selected control subjects based on the changed imaging parameter values. 
     Advantageous Effects of Invention 
     According to the present invention, an MRI apparatus that can adjust imaging parameters more efficiently can be obtained. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a view for explaining the overall configuration of the MRI apparatus that is an embodiment of the present invention. 
         FIG. 2  is a view for explaining the procedure before starting imaging in the embodiment described in  FIG. 1 . 
         FIG. 3  is a view for explaining the procedure to adjust parameters in the embodiment described in  FIG. 2 . 
         FIG. 4  is a view for explaining an example of a parameter display window. 
         FIG. 5  is a view for explaining arithmetic expression data that is a database example. 
         FIG. 6  is a view for explaining the procedure to change parameters. 
         FIG. 7  is a view for explaining an example of a parameter change screen of a SAR. 
         FIG. 8  is a view for explaining an example of a parameter change screen of a dB/dt. 
         FIG. 9  is a view for explaining the procedure to re-adjust parameters. 
         FIG. 10  is a view for explaining an example of a parameter change screen. 
         FIG. 11  is a view for explaining an example of a parameter change screen after changing parameters. 
         FIG. 12  is a view for explaining an example of a parameter change screen after changing a target value. 
         FIG. 13  is a view for explaining another embodiment of the parameter change screen described in  FIG. 10 . 
         FIG. 14  is a view for explaining the other embodiment of the parameter change screen described in  FIG. 10 . 
         FIG. 15  is a view for explaining an example of a parameter change screen of a method for selecting a parameter arbitrarily. 
         FIG. 16  is a view for explaining operations of the method described in  FIG. 15 . 
         FIG. 17  is a view for explaining an example of a parameter change screen in case of specifying a change plan. 
         FIG. 18  is a view for explaining the parameter adjustment procedure in a case where a plurality of pulse sequences are selected. 
         FIG. 19  is a view for explaining an example of a parameter change screen in a case where a plurality of pulse sequences are selected. 
         FIG. 20  is a view for explaining an example of a parameter change screen after changing parameters in a case where a plurality of pulse sequences are selected. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Hereinafter, an embodiment of the MRI apparatus related to the present invention (hereinafter, described as an embodiment) will be described in detail using the attached diagrams. Additionally, in the description of embodiments of the present invention, the same numerals are provided for the elements and procedures with the same functions in the diagrams, and the repeated descriptions will be omitted. In the present description, “calculation” includes not only four basic arithmetic operations by an algebra equation but also processes such as acquiring a desired value by retrieving data generated based on results experimented in advance, simulation results, calculation results, and the like. 
     First of all, the overview of the MRI apparatus of an embodiment will be described based on  FIG. 1 . An MRI apparatus  100  is an apparatus that acquires a tomographic image of an object  11  by utilizing the NMR phenomenon. As shown in  FIG. 1 , the MRI apparatus  100  is comprised of a static magnetic field generation source  20 , a gradient magnetic field generating unit  30 , a sequencer  12 , a high-frequency irradiation unit  40 , a signal detection unit  50 , and a control unit  60 . 
     The static magnetic field generation source  20  generates a homogeneous static magnetic field in a direction orthogonal to the body axis of the object  11  in case of a vertical magnetic field method and in the body-axis direction of the object  11  in case of a horizontal magnetic field method in a static magnetic field space accommodating the object  11 . The static magnetic field generation source  20  of a permanent magnet method, normal conducting method, or superconducting method is disposed around the object  11 . 
     The gradient magnetic field generating unit  30  has a gradient magnetic field coil  32  that generates gradient magnetic fields in the three axis directions X, Y, and Z that are a coordinate of the MRI apparatus  100  (stationary coordinate system) by superimposing them on the static magnetic field space and a gradient magnetic field power source  34  that drives the respective gradient magnetic field coils. By driving the gradient magnetic field power source  34  of the respective coils according to the command, i.e. control from the sequencer  12  to be described later, gradient magnetic fields Gx, Gy, and Gz are generated in the three axis directions X, Y, and Z. 
     In imaging, a slice plane (imaging cross section) for the object  11  by applying a slice direction gradient magnetic field pulse (G s ) in a direction orthogonal to the slice plane, a phase encoding direction gradient magnetic field pulse (G p ) and a frequency encoding direction gradient magnetic field pulse (G f ) are applied in the other two directions orthogonal to the slice plane and to each other, and then positional information of the respective direction is encoded to echo signals. 
     The sequencer  12  repeatedly applies a high-frequency magnetic field pulse (RF pulse) and a gradient magnetic field pulse in a predetermined pulse sequence. The sequencer  12  operates based on the control of a central processing unit (hereinafter, described as CPU)  14  and transmits various commands, i.e. control required to collect tomographic image data of the object  11  to the gradient magnetic field generating unit  30 , the high-frequency irradiation unit  40 , and the signal detection unit  50 . 
     The high-frequency irradiation unit  40  irradiates an RF pulse to the object  11  in order to cause nuclear magnetic resonance to atomic nucleus spins of atoms composing living tissue of the object  11 . The high-frequency irradiation unit  40  includes a high-frequency oscillator  42 , a modulator  44 , a high-frequency amplifier  46 , and an irradiation coil  48  that is a high-frequency coil on the transmission side. An RF pulse output from the high-frequency oscillator  42  is amplitude-modulated by the modulator  44  at a timing by a command from the sequencer  12 , the amplitude-modulated RF pulse is amplified using the high-frequency amplifier  46  and supplied to the irradiation coil  48  disposed in the vicinity of the object  11 , and then an electromagnetic wave is irradiated to the object  11 . 
     The signal detection unit  50  detects an echo signal that is an NMR signal to be emitted by nuclear magnetic resonance of atomic nucleus spins composing living tissue of the object  11 . The signal detection unit  50  includes a reception coil  52  that is a high-frequency coil on the reception side, a signal amplifier  54 , a quadrature phase detector  56 , and an analog/digital converter (hereinafter, described as A/D converter)  58 . A response NMR signal excited in the object  11  by electromagnetic waves irradiated from the irradiation coil  48  is detected by the reception coil  52  disposed in the vicinity of the object  11 , is amplified by the signal amplifier  54 , and is divided into two orthogonal system signals by the quadrature phase detector  56  at a timing by a command from the sequencer  12 , and then the respective system signals are converted into digital amounts by the A/D converter  58  and are sent to the control unit  60 . 
     The control unit  60  processes various data and displays and stores the process results. The control unit  60  includes a processor such as the CPU  14 , a storage device such as an internal memory  66 , an external storage device  61  such as an optical disk  62  and a magnetic disk  64 , and an input/output device  90 . When the signal detection unit  50  receives signals and data, the CPU  14  executes processes such as signal processing and image reconstruction using the internal memory  66  as a work area, displays a tomographic image of the object  11  that is the process result on an output device  96 , and stores the image in the external storage device  61  (such as the magnetic disk  64 ). 
     The input/output device  90  inputs and outputs various control information of the MRI apparatus  100  and control information to be processed by the control unit  60 , or specifically receives inputs of and displays imaging parameters of a pulse sequence and the like. The input/output device  90  is comprised of, for example, a pointing device  92  such as a trackball; a mouse; a pad; and a touch panel, input devices  91  including a keyboard  94 , a display  98  such as a cathode-ray tube (hereinafter, described as CRT) and a liquid crystal display (hereinafter, described as LCD), and the output device  96  including a printer  99 . 
     The input devices  91  may be arranged in the vicinity of the output device  96  to control the MRI apparatus  100  interactively by providing a command to execute various processes through the pointing device  92  while an operator checks the display  98 , for example. Also, it may be configured so as to perform inputs by disposing a touch panel operating as the input device  91  on the display surface of the display  98  and selecting or operating displayed contents on the display  98 . 
     Additionally, in  FIG. 1 , the object  11  is placed on the top plate of a bed  82  and accommodated by a bed moving device  80  in a static magnetic field space that is an imaging space. The irradiation coil  48  and the gradient magnetic field coil  32  on the transmission side are installed in the static magnetic field space where the object  11  is accommodated, opposite to the object  11  in case of the vertical magnetic field method or so as to surround the object  11  in case of the horizontal magnetic field method. Also, the reception coil  52  on the reception side is installed opposite to the object  11  or so as to surround the object  11 . 
     A clinically prevalent nuclide to be imaged by the MRI apparatus  100  is currently the hydrogen atomic nucleus (proton) that is a main component of the object  11 . By imaging information about spatial distribution of the proton density and that of a relaxation time in an excited state, forms and functions of the head, abdomen, extremities, and the like are imaged two- or three-dimensionally. 
     Hereinafter, the MRI apparatus and the imaging parameter setting assisting method of the present invention will be described. In the present invention, at least one of a specific absorption rate and a magnetic field variation rate per unit time of a magnetic flux density is set as a control subject, a suggestion of imaging parameters related to the control subject and a suggestion of change directions of the imaging parameters are displayed when the control subject is input based on an input operation, and then a value of the selected control subject is calculated based on a changed imaging parameter value when a displayed imaging parameter is changed. 
     For example, when a control subject input based on an input operation is a specific absorption rate, a suggestion of imaging parameters related to the specific absorption rate is displayed, and information about a suggestion of change directions of the imaging parameters is displayed. Alternatively, when a control subject input based on an input operation is a magnetic field variation rate per unit time of a magnetic flux density, a suggestion of parameters related to the magnetic field variation rate per unit time is displayed, and information about a suggestion of change directions of the imaging parameters for reducing the magnetic field variation rate is further displayed. 
     Hereinafter, the respective embodiments of the present invention will be described. 
     First Embodiment 
     The first embodiment 1 of the present invention will be described. First of all, the flow before starting imaging using the MRI apparatus  100  with the above configuration will be described with  FIG. 2 . For the object  11  to be examined, imaging can be started because imaging conditions are satisfied in a case where values of imaging indexes (a SAR and a dB/dt) are within allowable values in an operation mode capable of imaging when an RF pulse that is an electromagnetic wave is irradiated according to the pulse sequence stored in the internal memory  66  and the like of the MRI apparatus  100 . 
     First, a protocol that is a pair of pulse sequences is loaded to the MRI apparatus  100  (Step S 201 ). Specifically, the CPU  14  loads a protocol corresponding to predetermined conditions (for example, living body information such as a height, weight, and the like of the object  11 ) to the internal memory  66 . The protocol may be stored in the external storage device  61  in advance or may be input by an operator from the input device  91  to generate the protocol. 
     Following the above, imaging parameter adjustment is performed for a pulse sequence in a protocol (Step S 202 ). When an operator selects an arbitrary pulse sequence using the input device  91  to change the imaging parameter values, the CPU  14  identifies a pulse sequence to be changed and obtain change values of the imaging parameters. 
     Following the above, a SAR and a dB/dt are calculated using the change values of the imaging parameters (Step S 203 ). The CPU  14  identifies an arithmetic expression and an imaging parameter to be used, performs calculation, and then outputs the calculation result. Then, the CPU  14  determines whether or not the calculated values of imaging indexes is greater than an allowable value in an operation mode capable of imaging (Step S 204 ). 
     In a case where a SAR or dB/dt value is greater than an allowable value (Step S 204 : Yes), the CPU  14  provides a correcting command such as displaying a window notifying an imaging index exceeds the allowable value on the display  98  to an operator, and then goes back to Step S 202  to change an imaging parameter. In a case where SAR and dB/dt values are less than an allowable value (Step S 204 : No), the CPU  14  can execute a pulse sequence in which the pulse sequence was changed and controls so as to start imaging (Step S 205 ). 
     Here, the processes of the control unit  60  to optimize the Step S 202  process will be described.  FIG. 3  is a functional block diagram showing processing contents of the control unit  60 , and specifically is a diagram showing a flow of the processes to be executed through the input/output device  90  that has the input device  91  and the output device  96 , the types of processes to be executed by the CPU  14 , and the relationship with data to be stored in the external storage device  61  such as a database generated in the magnetic disk  64  (including a case of temporary storage in the internal memory  66 ). 
     Additionally, the CPU  14  functions as a display processing section  15  that displays various data and the like on the output device  96 , an operation reception section  16  that receives operations from the input device  91 , a parameter inquiry section  17  that obtains change values of imaging parameters and checks whether or not an allowable value of an imaging index is satisfied, and a calculation control section  18  that calculates the imaging index and outputs the calculation result according to a processing purpose. 
     Through Step S 201  described in  FIG. 2 , the control unit  60  displays a pulse sequence included in a loaded protocol on the input/output device  90  (Step S 301 ). Because protocol data  67  extracted from a database generated in the external storage device  61  has been loaded in the internal memory  66 , the display processing section  15  of the CPU  14  displays a plurality of pulse sequences included in the protocol data  67  in a format such as a table on the output device  96  so that an operator can select a pulse sequence. Additionally, the protocol data  67  is data identifiably stored in the external storage device  61  and the like by providing identification information each time a pulse sequence or the pair is generated and can be extracted by retrieving based on the identification information. 
     Next, a pulse sequence to change imaging parameters is identified (Step S 302 ). When an operator selects a pulse sequence a pulse sequence to change imaging parameters from among a plurality of pulse sequences displayed on the output device  96  using the input device  91 , the operation reception section  16  of the CPU  14  receives identification information of the pulse sequence from the input device  91  to identify a pulse sequence to be changed. The identification information is also set as conditions to extract parameter data  68  of the pulse sequence from the external storage device  61 . Additionally, a plurality of pulse sequences to be changed may be identified. 
     Next, the imaging parameters of the pulse sequence to be changed are displayed (Step S 303 ). The display processing section  15  of the CPU  14  sets the parameter data  68  extracted from the external storage device  61  for the corresponding items on a parameter display window shown in  FIG. 4  and displays them on the output device  96 . Additionally, the parameter data  68  is imaging parameters comprising a plurality of property information such as imaging conditions of the pulse sequence as shown in  FIG. 4 , may be data associated with the identification information of the pulse sequence, and may be data subordinate to the pulse sequence. 
     As an example of a parameter display window  102  displayed on the display  98 , item fields  112  of the respective parameters, setting value fields  114  that displays current setting values of the respective item parameters, operation fields  116  for operations to increase/decrease or change parameter values, a control subject selection field  132  that specifies whether or not either or both of a SAR and a dB/dt to be reduced, a sequence specifying field  122  for specifying a pulse sequence to be changed from a plurality of pulse sequences, and the like are arranged so as to be listed and displayed as shown in  FIG. 4 . 
     Next, a reduction target is specified to obtain change values of imaging parameters (Step S 304 ). When an operator selects a SAR or dB/dt as the reduction target using the input device  91 , the parameter inquiry section  17  of the CPU  14  identifies the reduction target and temporarily stores it in the internal memory  66 . Furthermore, when an operator changes the setting value fields  114  of imaging parameters displayed on the parameter display window  102  through the input device  91  by operating the operation fields  116 , the parameter inquiry section  17  of the CPU  14  obtains changed setting values and temporarily stores them in the internal memory  66 . Additionally, by identifying a reduction target, imaging parameters, a function that is an arithmetic expression, and the like to be used are identified by arithmetic expression data  69 . 
     The arithmetic expression data  69  is data showing which imaging parameters (variables) and what type of arithmetic expression (not shown in the diagram) are used respectively in SAR and dB/dt calculations as shown in  FIG. 5 . The data also includes data such as information about current values of the respective variables, change values for approximating a SAR and a dB/dt to target values, and increase/decrease suggestions. A region (field) to store each data is provided for a single record when generated as a table in a database. 
     Next, whether or not the changed imaging parameters satisfy allowable values is determined, and then increase/decrease suggestions are displayed for each parameter in case of not satisfying the allowable values (Step S 305 ). The calculation control section  18  of the CPU  14  included in the control unit  60  calculates SAR and dB/dt values using changed values temporarily stored in the internal memory  66  and determines whether or not to satisfy the allowable values respectively. Then, in case of not satisfying the allowable values, this is notified to an operator, and whether or not to increase or decrease each parameter is suggested by a means such as highlighting each parameter. In case of satisfying the allowable values, the procedure proceeds to Step S 203  in order to calculate a SAR and a dB/dt actually. 
       FIG. 5  shows an example of data stored in the internal memory  66  based on the database stored in the external storage device  61 . A database  150  shown in  FIG. 5  includes parameter fields  152  where the respective parameters are stored and setting value fields  154  where setting values for the respective parameters are stored. The database  150  further includes a SAR target value field  160  for storing a set target value of a SAR that is a control subject, SAR change value fields  162  for storing change values of parameters related to SAR target value calculation, imaging parameter fields  164  for storing whether or not the parameters are related to SAR target calculation, and increase/decrease suggestion fields  166  that show whether to increase or decrease setting values in order to achieve SAR targets. 
     Additionally, for dB/dt that is a control subject, the database  150  includes a dB/dt target value field  170  for storing dB/dt target values, dB/dt change value fields  172  for storing change values of parameters related to dB/dt target value calculation, imaging parameter fields  174  for storing whether or not the parameters are related to dB/dt target calculation, and increase/decrease suggestion fields  176  that show whether to increase or decrease setting values in order to achieve dB/dt targets. 
     The increase/decrease suggestion fields  166  of SAR and the increase/decrease suggestions fields  176  of dB/dt are determined based on an arithmetic expression for calculating a SAR or dB/dt that is a control subject. When the target values are relaxed, the increase/decrease directions of the increase/decrease suggestion fields  166  and the increase/decrease suggestion fields  176  are reversed. When one of a case of tightening the target values and a case of relaxing the target values is stored, an increase/decrease direction can be determined by reversing the increase/decrease direction in the opposite case a mentioned above. 
     Furthermore, a specific example of Step S 304  will be described using  FIG. 6 . When the CPU  14  of the control unit  60  identifies a reduction target, a search is performed for imaging parameters to decrease a SAR and a dB/dt or either of them as needed as shown in  FIG. 6  (Step S 601 ). The parameter inquiry section  17  identifies imaging parameters to be used in for SAR and dB/dt calculations from imaging parameters of the database  150  exemplified in arithmetic expression data shown in  FIG. 5 . 
     Next, suggestions to increase or decrease the searched imaging parameters are displayed based on the data of the database exemplified in  FIG. 5  (Step S 602 ). The parameter inquiry section  17  obtains current values for the imaging parameters and calculates SAR and dB/dt values or either of them as needed using the current values in order to determine increase/decrease suggestions for the current values. 
     Then, the increase/decrease suggestions are registered in the arithmetic expression data shown in  FIG. 5  and are highlighted by emphasizing imaging parameters on the parameter display window with a thick frame as shown  FIGS. 7 and 8 . The highlighted display is a display suggesting imaging parameters related to calculating control subject values input by a selection operation in the control subject selection field  132 , which can distinguish the other displayed imaging parameters by the recognizable suggestion. The highlighted display allows an operator to understand a viewpoint that should be checked precisely and can not only improve the workability but also reduce errors such as misrecognition, which leads to reliability improvement consequently. 
     Additionally,  FIG. 7  is an example of the highlighted display in a case where SAR is selected as a reduction target. Variables “TR”, “Multi Slice”, and “FA” are set as imaging parameters, and increase/decrease suggestions are displayed by the increase button for “TR” and by the decrease button for “Multi Slice” and “FA”. 
     Also,  FIG. 8  is an example of the highlighted display in a case where dB/dt is selected as a reduction target. Variables “TE”, “Freq#”, and “Thickness” are set as imaging parameters, and increase/decrease suggestions are displayed by the decrease button for “TE” and “Freq#” and by the increase button for “Thickness”. 
     Next, a value change is received for the searched imaging parameters (Step S 603 ). The parameter inquiry section  17  obtains a change value increased/decreased or input by an operator and temporarily stores it in the internal memory  66 . Additionally, changing imaging parameters other than highlighted parameters may be prohibited, or a change against increase/decrease suggestions may be prohibited. This can reduce influence of operational errors or misunderstanding by an operator. 
     When inputting imaging parameters is not finished (Step S 604 : No), the procedure goes back to Step S 602  to update increase/decrease suggestions by setting the changed imaging parameter values as current values and receives the next input. 
     As described above, according to the first embodiment of the present invention, imaging parameters for reducing either or both of a SAR and a dB/dt are extracted and displayed, and a change plan to increase or decrease the values is presented. Hence, the imaging parameters can be properly changed for the reduction. When an operator inputs at least either one of a SAR or a dB/dt as a reducing item from the control subject selection field  132 , the control unit  60  extracts and displays imaging parameters for reducing the input control subject values. The operator can input the displayed imaging parameters as changing targets. 
     Therefore, appropriate operations can be performed. Additionally, which imaging parameters should be adjusted becomes clear in order to reduce at least either one of a selected SAR or a selected dB/dt. Therefore, the imaging parameter changing method becomes clearly understandable. Additionally, errors are reduced. Particularly in the embodiments shown in  FIGS. 7 and 8 , selected imaging parameters and increase/decrease directions are highlighted, which can achieve clear understanding and further error reduction. 
     Second Embodiment 
     When imaging parameters are changed after setting an allowable value of an imaging index and the like as a target value in advance in a case where an estimated value of a SAR or a dB/dt exceeds the allowable value in the first embodiment, it may be configured so as to avoid exceeding the allowable value by suggestion to approximate to each target value. The other example of Step S 304  that realizes the above will be described using  FIG. 9 . 
     In Step S 901 , as an image for receiving an imaging parameter change, a parameter change window is started in the present embodiment. When an operator selects a control subject to be reduced in the parameter display window shown in  FIG. 4  and the CPU  14  of the control unit  60  identifies the reduction target, the parameter inquiry section  17  separately displays the parameter change window shown in  FIG. 10  on the output device  96 . 
     Additionally,  FIG. 10( a )  is an example of a parameter change window  202  in case of selecting a SAR as a reduction target, and  FIG. 10( b )  is an example of a parameter change window  212  in case of selecting a dB/dt as a reduction target. The change window  202  for SAR shown in  FIG. 10( a )  may be displayed separately from the display of  FIG. 4  and the displays of  FIGS. 7 and 8 , may be displayed with the display of  FIG. 4  and the displays of  FIGS. 7 and 8  on the same screen, or may be displayed using a method of superimposing the display of  FIG. 4  and the displays of  FIGS. 7 and 8  and displaying a selected display on the front. 
     In Step S 902 , a target value of a SAR or a dB/dt is obtained. The parameter inquiry section  17  obtains either target value to be identified as a reduction target. The target value is specified within an allowable value in an operation mode capable of imaging. The setting value may be set for arithmetic expression data shown in  FIG. 5  or the like in advance so as to use the setting value or may be input by an operator from the input device  91 . For example, in a normal operation mode, the allowable value is set as a target value or the like. 
     By disposing a progress bar  204  or the like that is one of graphical user interfaces (hereinafter, described as GUI) showing, for example, a relative position on the parameter change window shown in  FIG. 10 , the obtained target value is displayed with a current value of a SAR or a dB/dt when a reference value (such as 0 to 100%) is set as a standard. 
     For example,  FIG. 10( a )  shows that a SAR current value is 93% (the position specified by the black triangle) and that the target value is 50% (the position specified by the white triangle) in a case where a 6-minute average SAR (whole body) is 3.74 (W/kg) when an allowable value in a first level controlled operating mode is set to 100% and an allowable value in a normal operation mode is set to 50% as the reference values. That is, in this embodiment, a percentage to the maximum value of the reference value is displayed, and additionally, the percentage is displayed in a linear graph. 
     The current value is 93% to the maximum value of the reference value and is displayed with the black triangle mark as an example as shown in the diagram. Also, the target value is displayed with the white triangle mark as shown in the diagram. By describing the current value and the target value with the different marks, a current state can be judged properly, which can reduce misjudgment. The above is also similar to the parameter change window  212  for a dB/dt shown in  FIG. 10( b ) . 
     A current value and a target value are described using a GUI, for example, a progress bar  214 . The current value and the target value are displayed in percentage to the maximum value of the reference value. The current value is displayed with the black triangle mark as an example as shown in the diagram. Also, the target value is displayed with the white triangle mark as shown in the diagram. By describing the current value and the target value with the different marks, a current state can be judged properly, which can reduce misjudgment. 
     Imaging parameters related to changing a SAR or a dB/dt that is a control subject are searched (Step S 903 ) using the database  150  described in  FIG. 5 . The parameter inquiry section  17  identifies imaging parameters similarly to Step S 601 , and the imaging parameters and currently set parameter values are displayed on the parameter change windows  202  and  212  as shown in  FIG. 10 . 
     Next, imaging parameters value are searched so that a current SAR or dB/dt value approximates more to a target value (Step S 904 ). The parameter inquiry section  17  calculates suggestion values of the imaging parameters that should be changed to obtain a target SAR or dB/dt value by increasing or decreasing the respective imaging parameter values. The suggestion values (suggested by the white triangle) are displayed with current values (suggested by the black triangle) of the imaging parameters similarly to the target value by disposing progress bars or the like on the parameter change windows  202  and  212  as shown in  FIG. 10 . In this embodiment, as an example, values are displayed in percentage, and target values are also presented. 
     In an example shown in  FIG. 10( a ) , it is understood that an imaging parameter “TR” should be increased from the current value 300 to the suggestion value 562, that an imaging parameter “Multi Slice” should be decreased from the current value 24 to the suggestion value 12, and that an imaging parameter “FA” should be decreased from the current value 90 to the suggestion value 3 in order to decrease a SAR from the current value 93% to the target value 50%. 
     Also, in an example shown in  FIG. 10( b ) , it is understood that an imaging parameter “TE” should be decreased from the current value 6.3 to the suggestion value 6.1, that an imaging parameter “Freq#” should be decreased from the current value 264 to the suggestion value 248, and that an imaging parameter “Thickness” should be increased from the current value 6.0 to the suggestion value 7.4 in order to decrease a dB/dt from the current value 0.92 to the target value 0.75. 
     Next, inputting parameter values is received for the searched imaging parameters (Step S 905 ). The parameter inquiry section  17  obtains change values based on positions specified using progress bars or the like by an operator and temporarily stores the value in the internal memory  66 . When the operator inputs imaging parameter values, new values may be input in the setting value fields  114  provided corresponding to the item fields  112  of the imaging parameters, or positions corresponding to values to be input may be specified using progress bars  118 . 
     By specifying positions corresponding to values to be input on the progress bars  118  using a touch panel or a pointing device, the control unit  60  calculates the values corresponding to the specified positions and displays the calculation results in the setting value fields  114 . When an operator specifies the positions on the progress bars  118 , numerical values corresponding to the specified positions are displayed in the setting value fields  114 , and the operator moves the specified positions along the progress bars  118  and stops at desired positions so as to display desired values while checking the numerical values displayed in the setting value fields  114 . Thus, the desired values can be input as imaging parameter values. 
     When a position shown by the white triangle is set as a specified position, the position shown by the white triangle should be selected. This method is superior in understanding the current status because imaging parameter values can be specified based on relationships with current values and target values. An operator may input change values for all the imaging parameters related to a SAR or a dB/dt to be specified for which imaging parameters are now being changed. However, in case of showing a SAR to be specified as an example, it may be configured so that the control unit  60  calculate a value of the imaging parameter “FA” based on the fact that values of the imaging parameters “TR” and “Multi slice” have been set. 
     In case of changing target values (Step S 906 : Yes) or in case of continuing input of imaging parameters (Step S 907 : No), change values approximating target values more are searched by going back to Step S 904 , and then the next input is received. 
     That is, when the parameter inquiry section  17  obtains change values of imaging parameters (Step S 907 : No), the calculation control section  18  of the CPU  14  included in the control unit  60  calculates SAR and dB/dt values using the change values temporarily stored in the internal memory  66 , further re-searches imaging parameter values at which a SAR or a dB/dt most approximates a target value for each imaging parameter by going back to Step S 904 , and then updates a parameter change window as shown in  FIG. 11 . 
     For example, when “Multi slice” is changed from the value 24 to the value 18, the SAR is decreased from 93% to 70%, and, in addition to this, the suggestion value of “TR” for approximating the SAR to 50% that is the target value is updated to 420. Additionally, a relative position can be changed for a parameter whose value is not changed. 
     Also, the calculation control section  18  of the CPU  14  calculates SAR and dB/dt values when target values are changed (Step S 906 : Yes), further re-searches imaging parameter values at which a SAR or a dB/dt more approximates a target value for each imaging parameter by going back to Step S 904 , and then updates a parameter change window as shown in  FIG. 12 . 
     For example, in case of decreasing a SAR target value to 25%, the suggestion value of “TR” for approximating the SAR to the target value is updated to 840, and then the suggestion value of “Multi Slice” is updated to 6. 
     As described above, according to the second embodiment of the present invention, recommended parameter values for achieving a SAR or dB/dt target value can be changed with reference to them. This makes a parameter adjustment method for reducing a SAR and a dB/dt understandable, and imaging parameters can be adjusted efficiently so that a SAR and a dB/dt in a pulse sequence enters a state in an operation mode range capable of imaging. 
     The embodiments described in  FIGS. 10( a ), 10( b ) ,  11 , and  12  are contrast to allowable values in a first level controlled operating mode to be specified, current values and target values to be specified are displayed. Particularly, an allowable value in the first level controlled operating mode to be specified is set as 100% and is displayed in a bar graph. Although a general object is imaged in a first level controlled operating mode, an object requiring special care is imaged with a smaller burden by setting the first level controlled operating mode as a standard. 
     In this case, by setting target values at a percentage to allowable values in the first level controlled operating mode to be specified, more appropriate imaging parameters can be set, which can also obtain higher reliability in imaging. In the present embodiment, when target values are set at a percentage to allowable values in the first level controlled operating mode to be specified, the control unit  60  sets and displays setting values of the related imaging parameters from the target values. 
     Using such a method, appropriate imaging parameter values can be set. Some improve a control subject by increasing setting values of imaging parameters, and others improve a control subject by decreasing the setting values of imaging parameters. In the present embodiment, certain criteria are set in an improvement direction of an axis of the progress bar  204  showing a current value and a target value to be specified and in an arrangement direction of axes of the bar progress bars  118  showing current values and target values of the related imaging parameters. 
     As an example, all the left sides of the progress bars  204  and  118  shown in  FIGS. 10( a ), 10( b ) ,  11  and  12  shows the improvement directions of control subjects. Thus, the progress bars  118  are not set based on the magnitudes of numerical values of the axes, but the axis directions of the progress bars  204  and  118  are set based on the improvement directions of control subjects, which effectively enables easy operation. 
     Third Embodiment 
     Although reference values of the progress bars  118  or the like are displayed in percentage (relative display such as an allowable value in the first level controlled operating mode: 100% and allowable value in the normal operation mode: 50%) on the parameter change windows  202  and  212  to be used for changing imaging parameters in the second embodiment, the reference values may be displayed in the other method. 
     For example, as shown in  FIG. 13 , level suggestions such as “NORMAL LEVEL” in a position corresponding to an allowable value in the normal operation mode, “FIRST LEVEL” in a position corresponding to an allowable value in the first level controlled operating mode, and “SECOND LEVEL” in a position corresponding to an allowable value in the second level controlled operating mode may be displayed. 
     As described above, according to the third embodiment of the present invention, it becomes easier to understand whether or not a SAR or a dB/dt to be specified enters a state in a range capable of imaging in imaging based on a pulse sequence, which can adjust imaging parameters effectively. For example, a level of a SAR or dB/dt to be specified is set for imaging, and burdens are considered for a state of the object  11 , which makes determination easier and is also superior in management. 
     As an example, it is difficult to show a state of the object  11  with detailed numbers, and the effect is small even if the state is shown in percentage in detail. When the management is performed with three-stage classification or the like, desired results can be obtained. 
     Fourth Embodiment 
     The second and third embodiments described a method in which an operator changes imaging parameters by displaying the parameter change window  202  or  212  separately from the parameter display window  102 . Although the parameter display window  102  and a parameter change window may be displayed separately, it may be configured so that an operator changes the imaging parameters by displaying the parameter display window  102  and the parameter change windows  202  and  204  of a SAR and a dB/dt on the same display at the same time. 
     For example, as shown in  FIG. 14 , progress bars displayed on a parameter change window or the like are arranged in a free region other than the imaging parameter display regions of a parameter display window, and current values and target values are displayed relatively to reference values (such as 0 to 100%).  FIG. 14  shows the free region with broken-line frames  240  and  242 . 
     Additionally, although regions displaying the progress bar  204  for a SAR and the progress bar  214  for a dB/dt may be respectively provided by providing the broken-line frames  240  and  242  respectively, it may be configured so that the progress bar  204  for a SAR and the progress bar  214  for a dB/dt are displayed by sharing one region. In this case, a control subject selected in the control subject selection field  132 , i.e. the progress bar  204  or  214  selected in the control subject selection field  132  will be displayed. 
     Current and target values may be highlighted in case of selecting reduction targets. That is, it may be configured so that current and target values of a SAR are displayed in case of selecting a SAR as a reduction target and so that current and target values of a dB/dt are displayed in case of selecting a dB/dt as a reduction target based on selection in the control subject selection field  132 . 
     As described above, according to the fourth embodiment of the present invention, it becomes easier to understand whether or not a SAR and a dB/dt in a pulse sequence enter a state in an operation mode range capable of imaging only with a parameter display window, which can adjust imaging parameters effectively. 
     Also, a parameter display region displaying imaging parameters, a target value display region of control subjects shown in the broken-line frames  240  and  242 , and a control subject selecting region for displaying the control subject selection field  132  are provided. At least imaging parameters related to a SAR to be specified, the current values, and the operation fields  116  that suggest the change directions and allow an input operation as needed are arranged and displayed in the parameter display window. 
     In the target value display region of control subjects, for example, target values of the control subjects to allowable values are displayed in percentage as shown with the progress bars  204  and  214 . Although the progress bar  204  for a SAR and the progress bar  214  for a dB/dt may be displayed comparatively as described above, a progress bar selected in the control subject selection field  132  may be displayed selectively. When the progress bar  204  for a SAR and the progress bar  214  for a dB/dt are displayed comparatively, this is effective to easily understand the entire state. On the other hand, when the progress bar  204  for a SAR and the progress bar  214  for a dB/dt are displayed selectively, this has an advantage in that a region required for display is small. 
     Fifth Embodiment 
     Although imaging parameters are set for arithmetic expression data or the like shown in  FIG. 5  and extracted as imaging parameters to be used for SAR and dB/dt calculations in the first to fourth embodiments, it may be configured so that an operator can arbitrarily select imaging parameters to be changed. 
     As shown in  FIG. 15 , check boxes (one of GUIs to be used for selecting a plurality of items) are provided for each imaging parameter in a parameter display window, and an operator specifies whether or not each imaging parameter is set as a change target using the input device  91 . Additionally, when a parameter change is performed in the parameter display window, up and down buttons are enabled only for checked imaging parameters, and it should be set so that the values can be increased and decreased. Also, when a SAR or dB/dt button shown in the lower right of the diagram is pressed down, it should be set so as to display and change only the imaging parameters checked in a parameter change window. That is, the imaging parameters selected by an imaging parameter selection operation such as checking as described above becomes targets whose setting values can be changed. 
     Also, the operation fields  116  suggesting an increase/decrease direction are displayed for the selected imaging parameters. For example, an increase is suggested by an upward triangle for the selected imaging parameter “TR”. A decrease is suggested by a downward triangle for the selected imaging parameters “FA” and “Multi slice”. 
       FIG. 16  shows a flow chart for executing the operation described in  FIG. 15 , and the flow chart is executed by the control unit  60 . In the flow chart shown in  FIG. 16 , a process corresponding to Step S 304  described in  FIG. 3  and STEP S 905  described in  FIG. 9  is performed. When an operator performs an operation of selecting imaging parameters shown in  FIG. 15 , this flow chart is executed by setting the operation as a start condition, and when the operator performs an operation of inputting an imaging parameter value shown in  FIG. 15 , this flow chart is further executed by setting the operation as a start condition. 
     Alternatively, as the other starting method, the process may be performed based on whether or not an operator selects imaging parameters shown in  FIG. 15  or whether or not the operator performs an input operation for imaging parameter values between ending the last flow chart execution and starting the next flow chart execution by repeatedly starting this flow chart at a certain time interval. 
     When the flow chart execution shown in  FIG. 16  starts using the above method, whether or not it is the imaging parameter selection described in  FIG. 15  is determined in Step S 352 . For example, when it is not the imaging parameter selection but the imaging parameter value input, Steps from S 354  to S 358  are not required, and the control unit  60  proceeds to Step S 362 . On the other hand, in case of the imaging parameter selection, the procedure proceeds to Step S 354 , and a display suggesting being selected is performed. For example, when the imaging parameter “TR” is selected, a check suggesting being selected is displayed. 
     Also, Step S 356  is executed in order to suggest change directions of selected imaging parameter values. For example, in case of the imaging parameter “TR”, the upward triangle showing the increase direction displayed in the operation field  116  is changed to a white triangle. Additionally, in order to permit an input operation of numerical values of selected imaging parameters, Step S 358  is executed, and then a reception permission flag of setting values is set. The reception permission flag shows whether or not the numerical value input of the imaging parameter “TR” is permitted. 
     Next, the procedure proceeds to Step S 362 . Additionally, although this flow chart describes Step  352  to be executed following Step S 358 , a target to be processed is different between selecting imaging parameters to change setting values and inputting the selected imaging parameter values, and the selection and input operations may be performed separately under different execution conditions. 
     In this case, the procedure stops in Step S 358 , and Step S 362  may be set so as to start under new starting conditions. When Step S 362  is executed by the control unit  60 , whether or not to input numerical values that are imaging parameter setting values is determined. In case of inputting the numerical values of the imaging parameters, whether or not to permit reception of the numerical values is determined in Step S 364 . When a flag is set in Step S 358  described above, it is determined that receiving the numerical values has been permitted, and the numerical values input in Step S 366  are loaded and stored in a predetermined memory address. 
     The stored numerical values are used for calculating a SAR or a dB/dt in the calculation control section  18  described in  FIG. 3  for example. On the other hand, Step S 362  is different from inputting imaging parameter numerical values, this flow chart ends. Also, when a numerical value change is not permitted in Step S 364  even in case of inputting numerical values for imaging parameters, an error is displayed in Step S 368 , and then this flow chart ends. Even when this flow chart ends, it is repeatedly executed when the starting conditions are satisfied. 
     As described above, because changeable imaging parameters are not fixed according to the fifth embodiment, an operator can arbitrarily set imaging parameters to be changed in case of narrowing the imaging parameters, which makes the parameter adjustment method for reducing a SAR and a dB/dt understandable. 
     Sixth Embodiment 
     In the fifth embodiment, an operator arbitrarily select imaging parameters to be changed and changes them on a parameter display window. In this case, some changing patterns are prepared in accordance with a plan, a changing pattern is selected in accordance with the plan, imaging parameters intercorrelated with each other are automatically selected based on the selected pattern, and then imaging parameters may be automatically determined in accordance with the above plan. 
     There are change plans, for example, that contrast is not changed so that the contrast of an image to be obtained becomes as stable as possible, that a scan time is not changed and, in particular, is not extended, and that the number of images to be obtained is not changed, that is, the number of images to be imaged is maintained, and the like. According to such plans, groups of imaging parameters based on the respective plans are set as the change plans. 
     As shown in  FIG. 17 , a change plan display region  272  displaying a change plan is provided on the parameter display window  102 , and a change plan list  274  listing change plans is disposed on the change plan display region  272 . An operator selects an appropriate change plan from the change plan list  274 . A database in which list contents are described in the external storage device  61  in advance is created for a change plan list, and change plans composing the above list are displayed in order by operating a pull-down display  276  in the change plan display region  272  for example. By selecting a change plan thus, imaging parameters are automatically selected in accordance with the change plan. For example, a check showing that the imaging parameter “TR” is selected is displayed. Off course, the color may be changed instead of displaying a check. 
     Additionally, similarly to the operation of the pull-down display  276  and the like, it may be configured so that an operator can select an appropriate change plan from the change plan list  274  by a change plan selection operation and further increase and decrease imaging parameters to be changed arbitrarily. For example, if a group of imaging parameters is “TR” and “FA” when a change plan is specified in a case where only “TR” should be changed, “FA” may be excluded from the group by an excluding operation. 
     As described above, according to the sixth embodiment of the present invention, a SAR and a dB/dt can be reduced by adjusting parameters in light of a contrast, an imaging time, and a resolution of an image to be obtained. That is, an operator can easily adjust parameters to reduce a SAR or a dB/dt under desired conditions. 
     Seventh Embodiment 
     Although an operator selects a desired pulse sequence from a plurality of pulse sequences in a protocol in the first to sixth embodiments, a specific example of Step  4  in case of selecting a plurality of pulse sequences to be changed will be described using  FIG. 18 . For example, a case where two scans of the imaging sites “Pelvis” and “Knee” are set as targets to be changed and the like are included. 
     A parameter change window is started to receive an imaging parameter change (Step S 1701 ). When the CPU  14  identifies a reduction target selected by an operator in a parameter display window, the parameter inquiry section  17  displays the parameter change window shown in  FIG. 18  on the display  98  of the output device  96 . 
     A target value of a SAR or a dB/dt is obtained (Step S 1702 ). The obtained target value is displayed using a progress bar  282  or the like in a parameter change window  302  shown in  FIG. 19 . The reference value 40% is displayed as a standard in the position shown by the white triangle. Current values of a SAR or a dB/dt are displayed using the progress bars  204  and  214  or the like similarly in the positions, for example, shown by the black triangles for each scan (pulse sequence). 
     The most severely limited scan is searched (Step S 1703 ). The calculation control section  18  calculates a SAR and dB/dt values for all the pulse sequences selected as change targets, further calculates percentages to allowable values, and then stores them in the internal memory  66 . Then, the CPU  14  identifies a calculated highest percentage from among them as the most severely limited scan. 
     Imaging parameters reducing a SAR or a dB/dt are searched for the most strictly limited scan (Step S 1704 ) in order to search imaging parameter values at which the SAR or the dB/dt becomes the closest to a target value (Step S 1705 ). 
     The parameter inquiry section  17  displays imaging parameters and the parameter values (current values) on a parameter change display as shown in  FIG. 19  and displays suggestion values (positions shown by the white triangles) and current values (positions shown by the black triangles) of imaging parameters that should be changed to obtain target values of a SAR or a dB/dt on the progress bars  118  or the like. 
     Next, parameter value input is received (Step S 1706 ). In case of changing target values (Step S 1707 : Yes) or in case of not finishing imaging parameter input (Step S 1708 : No), the procedure goes back to Step S 904  to search change values that are the closest to target values, and a parameter change display is updated to receive the next input as shown in  FIG. 20 .  FIG. 20  is a window showing a state after the imaging parameters are changed, and the imaging parameter “TR” value is changed from 350 to 600. 
     As described above, according to the seventh embodiment, a SAR and a dB/dt of not only the whole body but also each body part are considered, which can adjust efficiently adjust imaging parameters so that a SAR and a dB/dt of a pulse sequence are a state within an operation mode range capable of imaging. 
     Also, parameter adjustment to reduce a SAR or a dB/dt can be performed without changing a contrast between each scan. 
     The present invention is not limited to the above described embodiments. 
     REFERENCE SIGNS LIST 
     
         
           11 : object 
           12 : sequencer 
           14 : CPU 
           15 : display processing section 
           16 : operation reception section 
           17 : parameter inquiry section 
           18 : calculation control section 
           20 : static magnetic field generation source 
           30 : gradient magnetic field generating unit 
           32 : gradient magnetic field coil 
           34 : gradient magnetic field power source 
           40 : high-frequency irradiation unit 
           42 : high-frequency oscillator 
           44 : modulator 
           46 : high-frequency amplifier 
           48 : irradiation coil 
           50 : signal detection unit 
           52 : reception coil 
           54 : signal amplifier 
           56 : quadrature phase detector 
           58 : A/D converter 
           60 : control unit 
           61 : external storage device 
           62 : optical disk 
           64 : magnetic disk 
           66 : internal memory 
           67 : protocol data 
           68 : parameter data 
           69 : arithmetic expression data 
           70 : SAR measurement section 
           80 : bed moving device 
           82 : bed 
           90 : input/output device 
           91 : input device 
           92 : pointing device 
           94 : keyboard 
           96 : output device 
           98 : display 
           99 : printer 
           100 : MRI apparatus