JP2018083105A - Magnetic resonance imaging apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic resonance imaging apparatus capable of setting pre-pulse easily and flexibly.SOLUTION: A magnetic resonance imaging apparatus according to the embodiment includes: a reception part; a derivation part; and a sequence control unit. The reception part presents a list of many kinds of tissues included in an imaging region collecting magnetic resonance signals and receives selection of at least one tissue kind out of many kinds of tissues by receiving from an operator a selection about whether or not the tissues desire suppression of a signal value or whether or not the tissues desire emphases on the signal value with respect to the respective many kinds of tissues. The derivation part derives pre-pulse application timing to be applied before magnetic resonance signals are collected according to the kind of tissues to be identified by the selection. The sequence control unit applies the pre-pulse according to the pre-pulse application timing and collects magnetic resonance signals.SELECTED DRAWING: Figure 1

Description

  Embodiments described herein relate generally to a magnetic resonance imaging apparatus.

  Magnetic Resonance Imaging (MRI) magnetically excites a nuclear spin of a subject placed in a static magnetic field by an RF (Radio Frequency) pulse of its Larmor frequency, and accompanying this excitation This is an imaging method for generating an image from generated magnetic resonance signals.

  In the field of magnetic resonance imaging, fluid (for example, blood, cerebrospinal fluid (CSF), lymph fluid, etc.) is labeled by applying a tag pulse, thereby rendering a fluid signal flowing into the imaging region. There are non-contrast imaging methods. For example, in an imaging method called an ASL (Arterial Spin Labeling) method, blood is labeled by applying a tag pulse, and a blood signal flowing into the imaging region is rendered. In addition, the ASL method includes a method of suppressing a background signal other than blood by applying a non-selection pre-pulse that does not select a region after applying a tag pulse and before collecting a magnetic resonance signal. This ASL method is used for perfusion imaging, MRA (Magnetic Resonance Angiography) imaging, and the like.

JP 2009-261517 A JP 2011-183152 A

  The problem to be solved by the present invention is to provide a magnetic resonance imaging apparatus capable of easily and flexibly setting a pre-pulse.

  The magnetic resonance imaging apparatus according to the embodiment includes a reception unit, a derivation unit, and a sequence control unit. The accepting unit presents a list of a plurality of types of tissues included in an imaging region for collecting magnetic resonance signals, and whether each of the plurality of types of tissues is a tissue for which suppression of a signal value is desired, or The selection of whether or not the signal value enhancement is desired is accepted from the operator, thereby accepting selection of at least one of the plurality of types of tissues. The deriving unit derives the application timing of the pre-pulse applied before collecting the magnetic resonance signal according to the tissue type specified by the selection. The sequence controller applies a pre-pulse according to the pre-pulse application timing and collects a magnetic resonance signal.

FIG. 1 is a functional block diagram showing the configuration of the MRI apparatus according to the first embodiment. FIG. 2 is a flowchart showing a processing procedure in the first embodiment. FIG. 3 is a diagram illustrating a protocol selection screen according to the first embodiment. FIG. 4 is a view showing a positioning image in the first embodiment. FIG. 5 is a diagram illustrating an imaging condition setting screen according to the first embodiment. FIG. 6 is a flowchart showing a procedure for setting a non-selected pre-pulse in the first embodiment. FIG. 7 is a diagram showing a graph display of signal value transition in the first embodiment. FIG. 8 is a diagram showing a graph display of signal value transition in the first embodiment. FIG. 9 is a diagram showing a graph display of signal value transition in the first embodiment. FIG. 10 is a flowchart showing a procedure for setting a non-selected pre-pulse in a modification of the first embodiment.

  Hereinafter, a magnetic resonance imaging (MRI) apparatus according to an embodiment will be described with reference to the drawings. Note that the embodiments are not limited to the following embodiments. The contents described in each embodiment can be applied in the same manner to other embodiments in principle.

(First embodiment)
FIG. 1 is a functional block diagram showing the configuration of the MRI apparatus 100 according to the first embodiment. As shown in FIG. 1, the MRI apparatus 100 includes a static magnetic field magnet 101, a static magnetic field power supply 102, a gradient magnetic field coil 103, a gradient magnetic field power supply 104, a bed 105, a bed control unit 106, and a transmission coil 107. , A transmission unit 108, a reception coil 109, a reception unit 110, a sequence control unit 120, and a computer 130. The MRI apparatus 100 does not include a subject P (for example, a human body). Moreover, the structure shown in FIG. 1 is only an example. For example, the sequence control unit 120 and each unit in the computer 130 may be configured to be appropriately integrated or separated.

  The static magnetic field magnet 101 is a magnet formed in a hollow cylindrical shape, and generates a static magnetic field in an internal space. The static magnetic field magnet 101 is, for example, a superconducting magnet or the like, and is excited by receiving a current supplied from the static magnetic field power source 102. The static magnetic field power supply 102 supplies a current to the static magnetic field magnet 101. The static magnetic field magnet 101 may be a permanent magnet. In this case, the MRI apparatus 100 may not include the static magnetic field power source 102. In addition, the static magnetic field power source 102 may be provided separately from the MRI apparatus 100.

  The gradient magnetic field coil 103 is a coil formed in a hollow cylindrical shape, and is disposed inside the static magnetic field magnet 101. The gradient coil 103 is formed by combining three coils corresponding to the X, Y, and Z axes orthogonal to each other, and these three coils individually supply current from the gradient magnetic field power supply 104. In response, a gradient magnetic field is generated in which the magnetic field strength varies along the X, Y, and Z axes. The gradient magnetic field power supply 104 supplies a current to the gradient magnetic field coil 103.

  The couch 105 includes a top plate 105a on which the subject P is placed. Under the control of the couch control unit 106, the couch 105a is placed in a state where the subject P is placed on the cavity ( Insert it into the imaging port. Usually, the bed 105 is installed so that the longitudinal direction is parallel to the central axis of the static magnetic field magnet 101. The couch controller 106 drives the couch 105 under the control of the computer 130 to move the couchtop 105a in the longitudinal direction and the vertical direction.

  The transmission coil 107 is arranged inside the gradient magnetic field coil 103 and receives a supply of RF pulses from the transmission unit 108 to generate a high-frequency magnetic field. The transmission unit 108 supplies an RF pulse corresponding to a Larmor frequency determined by the type of target atom and the magnetic field strength to the transmission coil 107.

  The reception coil 109 is disposed inside the gradient magnetic field coil 103 and receives a magnetic resonance signal emitted from the subject P due to the influence of the high-frequency magnetic field. When receiving the magnetic resonance signal, the reception coil 109 outputs the received magnetic resonance signal to the reception unit 110.

  Note that the transmission coil 107 and the reception coil 109 described above are merely examples. What is necessary is just to comprise by combining one or more among the coil provided only with the transmission function, the coil provided only with the reception function, or the coil provided with the transmission / reception function.

  The receiving unit 110 detects a magnetic resonance signal output from the receiving coil 109, and generates MR (Magnetic Resonance) data based on the detected magnetic resonance signal. Specifically, the receiving unit 110 generates MR data by digitally converting the magnetic resonance signal output from the receiving coil 109. In addition, the reception unit 110 transmits the generated MR data to the sequence control unit 120. The receiving unit 110 may be provided on the gantry device side including the static magnetic field magnet 101, the gradient magnetic field coil 103, and the like.

  Based on the sequence information transmitted from the computer 130, the sequence control unit 120 drives the gradient magnetic field power source 104, the transmission unit 108, and the reception unit 110 to execute a pulse sequence and image the subject P. Here, the sequence information is information defining a procedure for performing imaging. The sequence information includes the strength of the current supplied from the gradient magnetic field power source 104 to the gradient magnetic field coil 103 and the timing of supplying the current, the strength of the RF pulse supplied from the transmission unit 108 to the transmission coil 107, the timing of applying the RF pulse, The timing at which the unit 110 detects a magnetic resonance signal is defined. For example, the sequence control unit 120 is a processor such as a CPU (Central Processing Unit) and an MPU (Micro Processing Unit).

  The sequence control unit 120 drives the gradient magnetic field power source 104, the transmission unit 108, and the reception unit 110 to image the subject P. As a result, when receiving MR data from the reception unit 110, the sequence control unit 120 sends the received MR data to the computer 130. Forward.

  The computer 130 performs overall control of the MRI apparatus 100, generation of MR images, and the like. The computer 130 includes an interface unit 131, a storage unit 132, a control unit 133, an input unit 134, a display unit 135, and an image generation unit 136.

  The interface unit 131 transmits sequence information to the sequence control unit 120 and receives MR data from the sequence control unit 120. Further, when receiving the MR data, the interface unit 131 stores the received MR data in the storage unit 132. The MR data stored in the storage unit 132 is arranged in the k space by the control unit 133. As a result, the storage unit 132 stores k-space data.

  The storage unit 132 stores MR data received by the interface unit 131, k-space data arranged in the k-space by the control unit 133, image data generated by the image generation unit 136, and the like. For example, the storage unit 132 is a RAM (Random Access Memory), a semiconductor memory device such as a flash memory, a hard disk, an optical disk, or the like.

  The input unit 134 receives various instructions and information input from the operator. The input unit 134 is, for example, a pointing device such as a mouse or a trackball, or an input device such as a keyboard. The display unit 135 displays a GUI (Graphical User Interface) for receiving an input of imaging conditions, an MR image generated by the image generation unit 136, and the like under the control of the control unit 133. The display unit 135 is a display device such as a liquid crystal monitor, for example.

  The control unit 133 performs overall control of the MRI apparatus 100 and controls imaging, generation of MR images, display of MR images, and the like. For example, the control unit 133 is a processor such as a CPU or MPU. In addition, the control unit 133 includes an imaging condition setting unit 133a (also referred to as a “derivation unit”) as illustrated in FIG. The imaging condition setting unit 133a accepts input of imaging conditions on the GUI, and generates sequence information according to the accepted imaging conditions. In addition, the imaging condition setting unit 133a transmits the generated sequence information to the sequence control unit 120.

  The image generation unit 136 reads the k-space data from the storage unit 132, and performs an reconstruction process such as Fourier transform on the read k-space data to generate an MR image.

  The MRI apparatus 100 according to the first embodiment assumes a case where the head of the subject is imaged non-contrastly using the ASL method, and in the setting of imaging conditions performed prior to the imaging scan, A GUI for easily and flexibly setting an unselected pre-pulse is provided. In the following, an exemplary embodiment will be described in accordance with an inspection processing procedure performed by the MRI apparatus 100.

  FIG. 2 is a flowchart showing a processing procedure in the first embodiment. When the examination is started, first, the imaging condition setting unit 133a displays a protocol selection screen for accepting selection of a series of protocol groups included in the examination on the display unit 135, and from an operator such as a doctor or an engineer, The selection of the protocol group is accepted (step S1).

  The “protocol” is pulse sequence information including setting information of imaging conditions. The examination by the MRI apparatus 100 includes a series of pulse sequence groups such as various preparation scans and imaging scans. In each pulse sequence, imaging conditions such as TR (Repetition Time), TE (Echo Time), and flip angle FA (Flip Angle) are set. The MRI apparatus 100 manages and provides pulse sequence information including these imaging condition setting information (including preset information set in advance) as a “protocol”. The protocol group includes, for example, one or more of a protocol for collecting positioning images, a protocol for collecting sensitivity maps, a protocol for shimming, a protocol for imaging, and the like.

  FIG. 3 is a diagram illustrating a protocol selection screen according to the first embodiment. For example, as shown in FIG. 3, on the protocol selection screen, in order from the right, an area 1 for displaying protocol groups, an area 2 for displaying generic names of protocol groups displayed in area 1, and a human body model diagram The area 3 for receiving selection for each part to be imaged is displayed. On such a protocol selection screen, the operator can specify a desired protocol group to be executed by performing selection in the order of area 3, area 2, and area 1 in accordance with the hierarchical structure, for example.

  For example, when the operator selects a rectangle corresponding to “head” on area 1, a list of generic names of protocols related to “head” is displayed in area 2. Subsequently, when the operator selects, for example, “Brain1” which is a generic name of the protocol on the area 2, a protocol group corresponding to the generic name is displayed in the area 1. The protocol group includes, for example, one or more of a protocol for collecting positioning images, a protocol for collecting sensitivity maps, a protocol for shimming, a protocol for imaging, and the like. Therefore, the operator selects a desired protocol for the sensitivity map, shimming, imaging, etc. from the protocol group displayed in the area 1, and presses the end button. Thus, the imaging condition setting unit 133a accepts a selection of a series of protocol groups. Note that the protocol selection screen shown in FIG. 3 is merely an example for convenience of explanation, and for example, information displayed in each area can be arbitrarily changed according to the form of operation.

  Returning to FIG. 2, next, the sequence control unit 130 executes various preparation scans such as a preparation scan for collecting positioning images in accordance with a series of protocol groups selected in step S1 (step S2). For example, the sequence control unit 130 collects a sagittal image I1, an axial image I2, and a coronal image I3 as positioning images. Subsequently, the imaging condition setting unit 133a displays a setting screen for accepting the setting of the imaging condition of the imaging scan by the ASL method on the display unit 135, and accepts the setting of the imaging condition (step S3).

  FIG. 4 is a diagram illustrating a positioning image in the first embodiment. The imaging condition setting unit 133a displays the collected sagittal image I1, axial image I2, and coronal image I3 on the display unit 135, and accepts settings of an imaging region and a tag pulse application region from the operator. For example, the imaging condition setting unit 133a determines which positioning image is to be accepted among the sagittal image I1, the axial image I2, and the coronal image I3, and among the imaging region and the tag pulse application region in the image that accepts the operation. The designation of which area to accept and display is accepted by a radio button (not shown). For example, in the example of FIG. 4, the imaging region R1 and the tag pulse application region R2 are displayed on the sagittal image I1, the imaging region R3 is displayed on the axial image I2, and the imaging region R4 is displayed on the coronal image I3. It is displayed. As described above, in the first embodiment, the tag pulse application region R2 is set on the upstream side (the neck side in the example of FIG. 4) of the imaging region R1.

  FIG. 5 is a diagram illustrating an imaging condition setting screen according to the first embodiment. The imaging condition setting unit 133a displays the imaging condition setting screen illustrated in FIG. 5 on the display unit 135 together with the positioning image illustrated in FIG. 4 or separately from the positioning image. In the example of FIG. 5, it is assumed that preset information set in advance is displayed on the initial screen of the setting screen. In FIG. 5, the contents of the setting screen are omitted as appropriate for convenience of explanation. In addition, the setting screen illustrated in FIG. 5 is merely an example, and the embodiment is not limited thereto.

  As shown in FIG. 5, for example, the imaging condition setting unit 133a displays a pull-down menu for selecting a type such as a tag pulse at the top of the setting screen. In the example of FIG. 5, a type called an ASTA (Modified STAR (Signal Targeting Alternating Radio Frequency) Using Asymmetric Inversion Slabs) method is selected as “IR (Inversion Recovery) Pulse Type”.

  In addition, for example, the imaging condition setting unit 133a also has a TI (Inversion Time) that is the time from the tag pulse application timing to the magnetic resonance signal collection timing (for example, the collection timing near the center of the k space) at the top of the setting screen. ) And input items for accepting the setting of the flip angle FA. In the example of FIG. 5, TI = 1800 ms and FA = 180 ° are set. Further, for example, the imaging condition setting unit 133a displays an input item for accepting the setting of the number of non-selected prepulses applied after applying the tag pulse at the bottom of the setting screen. In the example of FIG. 5, for example, “3” is set.

  Further, the imaging condition setting unit 133a displays a time chart on the setting screen. Note that the imaging condition setting unit 133a can accept settings individually for the tag pulse (or control pulse), the first non-selected pre-pulse, the second non-selected pre-pulse, and the third non-selected pre-pulse. The display of the time chart can be switched with a tab so that it can be done. In the example of FIG. 5, the tab of the second non-selected pre-pulse is displayed in a state where the operation by the operator can be accepted.

  In the time chart, the tag pulse is applied so that the mark M1 indicating the imaging timing (that is, the acquisition timing of the magnetic resonance signal, for example, the acquisition timing in the vicinity of the center of the k space) starts from the mark M1 and goes back on the time axis A mark M2 indicating timing, a mark M3 indicating application timing of each of the first unselected prepulse, the second unselected prepulse, and the third unselected prepulse are displayed. In the example of FIG. 5, the tag pulse application timing is indicated by a white oval mark, while the application timing of the non-selected prepulse is indicated by a hatched oval mark. It has been subjected. Of course, the expression of the mark is not limited to this, and can be changed as appropriate, such as distinguishing between single and double ellipse marks or distinguishing between ellipses of different colors. On each mark, the time from the pulse application timing indicated by each mark to the magnetic resonance signal acquisition timing is displayed. In the example of FIG. 5, the TI from the application timing of the tag pulse to the acquisition timing of the magnetic resonance signal is 1800 ms, the TI from the application timing of the first non-selection prepulse to the acquisition timing of the magnetic resonance signal is 1278 ms, and the second non-selection The TI from the pre-pulse application timing to the magnetic resonance signal collection timing is 547 ms, and the TI from the third non-selected pre-pulse application timing to the magnetic resonance signal collection timing is 125 ms.

  Further, the imaging condition setting unit 133a can accept the adjustment of the signal value at the magnetic resonance signal collection timing at the level of the tissue included in the imaging region. For example, when “organization A”, “organization B”, “organization C”, and “organization D” are assumed as the tissues included in the imaging area, the imaging condition setting unit 133a displays the area B1 in FIG. As shown, a check box for accepting selection or non-selection of “Organization A”, “Organization B”, “Organization C”, and “Organization D” is displayed, and selection from the operator is accepted. In the first embodiment, the signal value of the selected tissue is adjusted to be substantially zero at the magnetic resonance signal acquisition timing. In the example of FIG. 5, “organization A”, “organization B”, and “organization D” are selected, and “organization C” is not selected. Examples of the tissue include fat, white matter, gray matter, and cerebrospinal fluid.

  Here, the non-selected pre-pulse will be described. In the ASL method, which is a kind of non-contrast imaging method, it is possible to suppress signal values of tissues other than blood desired to be drawn by using non-selective (NssIR: Non Slice Selective Inversion Recovery) prepulses. . Although not necessarily essential, in the first embodiment, the number of non-selected prepulses and the number of tissues whose signal values are desired to be suppressed are matched.

  This non-selected prepulse is applied at a timing such that the longitudinal magnetization of the tissue whose signal value is to be suppressed becomes substantially zero at the acquisition timing of the magnetic resonance signal. The timing at which the longitudinal magnetization becomes zero is determined by the T1 value of the tissue whose signal value is to be suppressed and the TI (hereinafter referred to as TagTI) from the application timing of the tag pulse to the acquisition timing of the magnetic resonance signal.

When the maximum value of the longitudinal magnetization of the tissue is “1”, the longitudinal magnetization A (n) when n non-selected prepulses are applied at the timing T (n) after applying the tag pulse is It is represented by the formula (1).
A (n) = 1- {1 + A (n-1)} * exp [-{T (n) -T (n-1)} / T1]
... (1)

  At this time, normally, in order to suppress the signal value of the background tissue, a saturation pulse (SAT pulse) is applied to the imaging region immediately before or immediately after the tag pulse application timing, so T (0) immediately after the tag pulse application. The longitudinal magnetization A (0) at that time is assumed to be “0”. When no SAT pulse is applied, the longitudinal magnetization A (0) at T (0) immediately after the tag pulse is applied is “1”.

A calculation example in the case of suppressing the signal value of a tissue (stationary part other than blood) having a T1 value of 250 ms when TagTI = 1000 ms is shown below. First, since the number of tissues whose signal values are to be suppressed is one, the number of non-selected prepulses to be applied is also one. When the timing of applying the non-selected prepulse is TI (1), the longitudinal magnetization A (1) of the tissue whose signal value is to be suppressed at the timing of applying the non-selected prepulse is expressed by the following equations (2) and (3). It is expressed by a formula.
A (1) = 1− {1 + A (0)} * exp [− {TI (1) −T (0)} / 250]
... (2)
A (1) = 1-exp [-{TI (1)}] / 250] (3)

After TagTI = 1000 ms has elapsed, the longitudinal magnetization A (2) of the tissue whose signal value is to be suppressed at the magnetic resonance signal acquisition timing is expressed by the following equation (4).
A (2) = 1- {1 + A (1)} * exp [-{1000-T (1)} / 250]
... (4)

Here, when the longitudinal magnetization A (2) is “0”, it is expressed by the following equations (5) and (6).
0 = 1− {1 + A (1)} * exp [− {1000−T (1)} / 250] (5)
0 = 1− {1+ (1−exp [− {TI (1)} / 250])} * exp [− {1000−TI (1)} / 250] (6)

  Solving this, TI (1) = 831 ms, and the time TInss from the timing of applying the non-selected pre-pulse to the magnetic resonance signal acquisition timing is calculated by TagTI-TI (1), and TInss = 1000-831 = 169 ms. It becomes. The time TInss from the application timing of the non-selected prepulse to the magnetic resonance signal acquisition timing can be calculated by such an algorithm.

  Returning to FIG. 5, the imaging condition setting unit 133 a displays imaging condition setting information as illustrated in FIG. 5 as preset information set in advance, for example. That is, in the example of FIG. 5, three tissues “tissue A”, “tissue B”, and “tissue D” are selected as tissues whose signal values are to be suppressed, and the number of unselected pre-pulses is set to “3”. In addition, each application timing is displayed as a calculation result of the algorithm as described above.

  In the setting screen, the imaging condition setting unit 133a can accept various changing operations from the operator. For example, the imaging condition setting unit 133a can accept an operation of removing a check box that has already been selected in the area B1 of FIG. 5 or an operation of inserting a check box that has not been selected. For example, the operator can make a selection different from the preset information based on his / her preference and prior knowledge. For example, the operator clears the check box of “Organization D” based on prior knowledge that there are few “Organization D” in the region of interest, and selects only “Organization A” and “Organization B” as the organizations whose signal values are to be suppressed. It is possible to select. Note that the setting of the number of unselected pre-pulses may be changed to “2” in conjunction with this operation. When receiving this operation, the imaging condition setting unit 133a can automatically perform the above-described calculation again and update and display the time chart according to the calculation result.

  Further, for example, the imaging condition setting unit 133a can accept an operation for changing TagTI or TIIns itself. For example, the imaging condition setting unit 133a receives an operation for changing the TagTI on the top row of the setting screen or on the time chart. Based on prior knowledge such as the age and blood flow velocity of the subject, the operator changes the TagTI by sliding the mark M2 on the time axis by, for example, a drag and drop operation on the time chart. The number displayed on the mark M2 is updated in conjunction with this drag and drop operation. Further, when receiving this operation, the imaging condition setting unit 133a automatically performs the above-described calculation again, and can update and display the time chart according to the calculation result.

  FIG. 6 is a flowchart showing a procedure for setting a non-selected pre-pulse in the first embodiment. Note that the imaging condition setting unit 133a is not necessarily limited to the case of performing processing according to the processing procedure illustrated in FIG. 6, but the setting of TInss is performed according to the selection of the TagTI or the tissue whose signal value is to be suppressed. It is for explanation.

  The imaging condition setting unit 133a first sets TagTI (step S101) and sets a tissue whose signal value is to be suppressed (step S102). Next, the imaging condition setting unit 133a performs calculation using the above-described algorithm based on the TagTI set in step S101 and the T1 value of the tissue set in step S102, and obtains TInss of the non-selected prepulse. Set (step S103). As described above, in the first embodiment, the number of non-selected pre-pulses is matched with the number of tissues whose signal values are to be suppressed. Therefore, when a plurality of tissues whose signal values are to be suppressed are selected, the imaging condition setting unit 133a creates the number of tissues selected from the above-described formula (1), and the longitudinal magnetization of the selected tissues is “0”. Each TInss is obtained by solving simultaneous equations so that In the first embodiment, the case has been described in which the processing results so far have already been incorporated as protocol preset information.

  Here, the imaging condition setting unit 133a determines whether an operation for changing the TagTI has been received (step S104) and an operation for changing the tissue whose signal value is to be suppressed has been received (step S105). When the imaging condition setting unit 133a receives an operation for changing the TagTI (Yes in step S104), the imaging condition setting unit 133a returns to the process in step S101, and recalculates and resets TInss. If the imaging condition setting unit 133a receives an operation to change the tissue (Yes in step S105), the imaging condition setting unit 133a returns to the process in step S102, and recalculates and resets TInss. This is repeated as appropriate, and the imaging condition setting unit 133a completes the setting of TInss (step S106).

  By the way, for example, the imaging condition setting unit 133a is a graph showing the temporal transition of the signal value in the imaging region for each organization together with the setting screen shown in FIG. 5 or separately from the setting screen shown in FIG. May be displayed. The imaging condition setting unit 133a displays this graph in conjunction with the content set by the imaging condition setting unit 133a (for example, the content corresponding to the preset information or the content that received the change operation). Further, the imaging condition setting unit 133a may simply display this graph as reference information for the operator, or may accept a change operation from the operator on the graph.

  7 to 9 are graphs showing signal value transition graphs in the first embodiment. For example, the imaging condition setting unit 133a displays a graph having the vertical axis as the longitudinal magnetization and the horizontal axis as the time axis. In addition, the imaging condition setting unit 133a displays a plot indicating the transition of longitudinal magnetization for each blood that is desired to be drawn (inflow blood) and each tissue whose signal value is desired to be suppressed. In the examples of FIGS. 7 to 9, the difference between blood and each tissue is expressed by the difference in line type, but the embodiment is not limited to this, and may be displayed by, for example, a difference in color. .

  The longitudinal magnetization of each tissue will be briefly described with reference to FIG. 7. In the first embodiment, the sequence control unit 120 applies a SAT pulse having a flip angle FA = 90 ° to a tag pulse applied to the application region R2. It is applied to the imaging region R1 at a timing immediately before or after the timing. For this reason, the initial value of longitudinal magnetization is “0” for the tissue in the imaging region R1 (excluding blood flowing into the imaging region R1). Further, the sequence control unit 120 applies an IR pulse having a flip angle FA = 180 ° as a tag pulse twice by selecting the application region R2. Since the blood flowing into the imaging region R1 is blood to which the tag pulse is applied twice, the initial value of the longitudinal magnetization is “1”.

  For example, the imaging condition setting unit 133a displays the graph shown in FIG. 7 as a graph corresponding to the preset information. That is, in the example of FIG. 7, three tissues “tissue A”, “tissue B”, and “tissue D” are selected as tissues whose signal values are to be suppressed, and the number of unselected pre-pulses is set to “3”. It is a state that has been. In the example of FIG. 7, in addition to the three tissues “tissue A”, “tissue B”, and “tissue D”, as a result, the longitudinal magnetization of “tissue C” also has a magnetic resonance signal collection timing. It is almost “0”.

  Here, the greater the number of unselected prepulses, the lower the signal value in the collected magnetic resonance signal. Thus, for example, assume that the operator attempts to reduce the number of unselected prepulses. For example, it is assumed that the operator clears the “Organization D” check box in the area B1 on the setting screen illustrated in FIG. 5 and selects only “Organization A” and “Organization B”. Then, the imaging condition setting unit 133a performs recalculation based on the TagTI = 1800 ms, the T1 value 250 ms of the tissue A, and the T1 value 800 ms of the tissue B, and newly obtains TInss1 = 152 ms and TInss2 = 774 ms. The imaging condition setting unit 133a reflects this on the time chart of FIG. 5 and also reflects it on a graph as shown in FIG. 8, for example. Further, as illustrated in FIG. 8, the imaging condition setting unit 133a may display, for example, a signal value at the magnetic resonance signal collection timing as a number under each tissue in the region B1. The operator can confirm how much the longitudinal magnetization of each tissue is suppressed by looking at this graph or by looking at the numbers in the region B1.

  Further, for example, the imaging condition setting unit 133a accepts an operation for changing the application timing of the non-selected prepulse from the operator directly on this graph. The operator changes the application timing of the non-selected prepulse from TInss2 = 774 ms to TInss2 = 790 ms by moving a line plotted by, for example, a drag and drop operation on the graph. The imaging condition setting unit 133a performs calculation as needed according to the operation of the operator, and continuously updates and displays the transition of the longitudinal magnetization of each tissue so as to reflect the calculation result. For this reason, the operator can perform this operation while confirming in real time how the longitudinal magnetization of each tissue changes as a result of his own change operation. As a result, the signal values of “tissue B” slightly increase, but the signal values of “tissue C” and “tissue D” decrease. This can be confirmed not only on the graph but also by looking at the numbers in the region B1. In addition, although the example which the graph displayed sequentially is switched from FIG. 7 to FIG. 9 was demonstrated here, embodiment is not restricted to this. For example, the imaging condition setting unit 133a may display two or three graphs side by side on the display unit 135 in FIGS.

  As described above, the imaging condition setting unit 133a provides a GUI that accepts selection or non-selection of the plurality of types of tissues included in the imaging region, or the number of tissues. The imaging condition setting unit 133a also provides a GUI in the form of a time chart or a graph, and accepts selection or non-selection of an organization, or the number, TagTI, and TInss settings from an operator. In particular, in the case of a GUI in the form of a graph, for example, it is possible to visualize how much a background tissue signal other than blood is likely to remain. The operator can make various settings while confirming how the change operation affects the longitudinal magnetization of each tissue. In the above-described embodiment, the change operation for the preset information has been described. However, the embodiment is not limited thereto, and an operation as an initial setting may be received.

  Thus, the setting of the imaging condition of the imaging scan by the imaging condition setting unit 133a is completed. Returning to FIG. 2, the sequence control unit 120 executes the pulse sequence according to the setting by the imaging condition setting unit 133a (step S4). The sequence control unit 120 applies the tag pulse to the tag pulse application region set in step S3 at a timing of TagTI = 1800 ms. Next, the sequence control unit 120 applies the first non-selected prepulse at a timing of TInss2 = 790 ms without selecting a region. Further, the sequence control unit 120 applies the second non-selected pre-pulse at a timing of TInss1 = 152 ms without selecting a region. Then, the sequence control unit 120 collects magnetic resonance signals in the imaging region. For this collection, for example, SSFP (Steady State Free Precession), GRE (Gradient Echo), FSE (Fast Spin Echo), EPI (Echo Planar Imaging), etc. are used. Note that the sequence control unit 120 controls the application timing of each pulse and the collection timing of the magnetic resonance signal using a biological signal such as an electrocardiogram synchronization signal and a pulse wave synchronization signal, a clock signal of the MRI apparatus 100, and the like as a trigger signal. .

  Thereafter, as necessary, the image generation unit 136 generates an MR image or displays it on the display unit 135 using the magnetic resonance signals collected in step S4 (step S5).

  As described above, according to the first embodiment, a GUI for accepting signal value adjustment at the tissue level is provided, and the application timing of the non-selected pre-pulse is determined according to the setting content accepted on the GUI. Since it is automatically derived, the operator can easily and flexibly set the non-selected pre-pulse. As a result, an optimum timing can be set as the application timing of the non-selection pulse.

  In the first embodiment described above, the imaging condition setting unit 133a performs calculation using the algorithm described above in accordance with the preset information and the setting content received on the GUI, and sets the application timing of the non-selected prepulse. The example to ask was explained. However, the embodiment is not limited to this, and, for example, a combination of TagTI, tissue T1 value, and application timing of the non-selected prepulse may be fixedly determined.

  In this case, for example, when the TagTI is “950 to 1050 ms” and the T1 value of the tissue is “250 ms”, the imaging condition setting unit 133a uses, as preset information, a table that defines that TInss is “169 ms”. Remember. Further, for example, when the TagTI is “950 to 1050 ms” and the T1 values of the tissue are “250 ms” and “800 ms”, the imaging condition setting unit 133a sets the TInss to “130 ms” and “565 ms”. The determined table is stored as preset information. And the imaging condition setting part 133a should just derive | lead TInss based on this table.

  FIG. 10 is a flowchart showing a procedure for setting a non-selected pre-pulse in a modification of the first embodiment. The difference between FIG. 10 and FIG. 6 is step S203 and step S103. That is, in the modification of the first embodiment, the imaging condition setting unit 133a obtains the TInss of the unselected prepulse based on the TagTI set in step S201 and the T1 value of the tissue set in step S202. In addition, the calculation is performed by referring to a preset table instead of performing calculation by an algorithm.

(Other embodiments)
Note that the embodiment is not limited to the above-described embodiment.

(About the organization selection GUI)
In the first embodiment described above, an example in which the imaging condition setting unit 133a displays a check box for accepting selection or non-selection of a tissue included in an imaging region has been described. The type and number of tissues displayed at this time may change according to the imaging target region. For example, the imaging condition setting unit 133a can change at least one of the types and number of tissues displayed on the GUI according to the imaging target region.

  For example, when the imaging target region is the “head”, the imaging condition setting unit 133a assumes that fat, white matter, gray matter, and cerebrospinal fluid are assumed as tissues included in the imaging region. In the case of “abdomen”, the type and number of tissues that can be assumed are stored in advance for each imaging target region, such as fat, liver, and spleen as tissue included in the imaging target region. For example, the imaging condition setting unit 133a changes the type and number of tissues displayed on the setting screen in step S3 according to the imaging target region selected in step S1 in the processing procedure using FIG. To do.

  In the first embodiment described above, the imaging condition setting unit 133a displays, as a GUI, a list of tissues for which suppression of signal values is desired among a plurality of types of tissues included in the imaging region. An example has been described in which selection of a tissue for which suppression of a signal value is desired is directly received on the list. However, the embodiment is not limited to this, and as a result, it is only necessary to know the type and number of tissues for which suppression of the signal value is desired. That is, it is possible to arbitrarily change in which list form the GUI is provided.

  For example, the imaging condition setting unit 133a may select a list of tissues for which enhancement of signal values is desired among a plurality of types of tissues included in the imaging area, instead of a list of tissues for which suppression of signal values is desired. May be displayed as a GUI, and selection of a tissue for which signal value enhancement is desired may be received on the list. In this case, for example, the imaging condition setting unit 133a separately stores a list of tissues that are assumed to be included in the imaging area, and the tissue other than the tissue for which enhancement is desired is desired to suppress the signal value. What is necessary is just to determine that it is an organization. Examples of tissues that are desired to be emphasized include blood, cerebrospinal fluid, liver, and spleen.

  Alternatively, for example, the imaging condition setting unit 133a may classify the object whose signal value is to be suppressed or emphasized at the level of the observation object instead of displaying the GUI by classifying the object at the tissue level. For example, even for “blood” in the same “abdomen”, as the level of the observation target, classification such as “hepatic artery”, “hepatic vein”, “portal vein”, and the like can be assumed. Therefore, the imaging condition setting unit 133a displays a list of observation target levels and accepts selection of the observation target from the operator. And the imaging condition setting part 133a should just determine the structure | tissue in which suppression of a signal value is desired from the selected observation object. For example, when “hepatic artery” or “hepatic vein” is selected, “liver” or “fat” is specified as the tissue whose signal value is desired to be suppressed, but “portal vein” is selected. For example, “liver” or “fat” is removed from the tissue for which suppression of the signal value is desired.

(Imaging method)
Further, the setting of each region in FIG. 4 exemplified in the above-described first embodiment, the number of tag pulses, SAT pulses, the number of unselected pre-pulses, combinations, and the like are merely examples. For example, in the ASL method, “NN difference method” in which a tag image and a control image are collected in pairs for each of a plurality of TIs to generate a differential image of each image, or blood flow using only one image is used. There are “mIR (Multiple IR) difference-less method” for generating an image, “mIR NN difference method” that uses both of them. For example, the above-described embodiments can also be applied to the “NN difference method”, the “mIR difference less method”, or the “mIR NN difference method”. Further, the present invention is not limited to the ASL method, and the above-described embodiments can be similarly applied as long as the imaging method applies a pre-pulse at a set timing before the magnetic resonance signal acquisition timing.

  Further, for example, in the first embodiment described above, the sequence control unit 120 has described the example in which the IR pulse having the flip angle FA = 180 ° is applied twice as the tag pulse by selecting the application region R2. The embodiment is not limited to this. For example, a method in which no tag pulse is applied can be used. For example, the sequence control unit 120 may apply an IR pulse with a flip angle FA = 180 ° as a tag pulse once by selecting the application region R2. In this case, since the blood flowing into the imaging region R1 is blood to which this tag pulse is applied once, the initial value of the longitudinal magnetization is “−1”.

(Specific numerical values, processing order)
In addition, the specific numerical values (for example, 1800 ms) and the processing order (for example, the processing procedures shown in FIGS. 2, 6, and 10) exemplified in the above-described embodiment are merely examples in principle. Further, the setting screen shown in FIG. 5 and the graphical GUI shown in FIGS. 7 to 9 are merely examples. For example, although FIG. 5 illustrates an example in which a check box format GUI is provided as a GUI for accepting selection or non-selection of an organization, the embodiment is not limited thereto. For example, the GUI can be selected arbitrarily in a pull-down menu format, and the format can be arbitrarily changed.

  In the above-described embodiment, the example in which the signal desired to be drawn is the blood signal flowing into the imaging region has been described, but the embodiment is not limited thereto. For example, other fluids such as cerebrospinal fluid and lymph fluid may be used.

(program)
The instructions shown in the processing procedures shown in the above-described embodiments can be executed based on a program that is software. The instructions described in the above-described embodiments are recorded on a magnetic disk, an optical disk, a semiconductor memory, or a similar recording medium as a program that can be executed by a computer. When the computer reads the program from the recording medium and causes the CPU to execute instructions described in the program based on the program, the same operation as the MRI apparatus 100 and the image processing apparatus of the above-described embodiment is realized. be able to. Further, when the computer acquires or reads the program, it may be acquired or read through a network.

  According to the magnetic resonance imaging apparatus according to at least one embodiment described above, the prepulse can be easily and flexibly set.

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

DESCRIPTION OF SYMBOLS 100 MRI apparatus 120 Sequence control part 133 Control part 133a Imaging condition setting part

The magnetic resonance imaging apparatus according to the embodiment includes a reception unit and a derivation unit . The reception unit presents a list of a plurality of types of observation targets included in an imaging region for collecting magnetic resonance signals, and receives selection of at least one observation target from the list . The deriving unit derives the application timing of the pre-pulse applied before collecting the magnetic resonance signal so that the tissue signal corresponding to the observation target received by the receiving unit is suppressed .

Claims (7)

A list of a plurality of types of tissues included in an imaging region for collecting magnetic resonance signals is presented, and for each of the plurality of types of tissues, whether or not the tissue is desired to suppress signal values, or signal value enhancement Accepting a selection as to whether or not a desired organization is received from an operator, and receiving a selection of at least one organization type among the plurality of types of organizations;
A derivation unit for deriving application timing of a pre-pulse applied before acquisition of a magnetic resonance signal according to the tissue type specified by the selection;
A magnetic resonance imaging apparatus, comprising: a sequence control unit that applies a prepulse according to the application timing of the prepulse and collects a magnetic resonance signal.   The derivation unit, when a tissue whose signal value is desired to be suppressed is selected, causes the signal value of the selected tissue among the plurality of types of tissues to be substantially zero at the collection timing of the magnetic resonance signal. The magnetic resonance imaging apparatus according to claim 1, wherein the application timing of the pre-pulse is derived.   When the tissue whose signal value is desired to be emphasized is selected, the derivation unit sets the signal value of the unselected tissue among the plurality of types of tissue to substantially zero at the collection timing of the magnetic resonance signal. The magnetic resonance imaging apparatus according to claim 1, wherein the application timing of the pre-pulse is derived.   The reception unit displays a GUI (Graphical User Interface) for receiving selection or non-selection settings on the imaging condition setting screen by arranging the plurality of types of organizations. The magnetic resonance imaging apparatus according to any one of the above.   The magnetic resonance imaging apparatus according to claim 4, wherein the derivation unit changes at least one of the types and numbers of the tissues displayed on the GUI according to an imaging target region.   The magnetic resonance imaging apparatus according to claim 1, wherein the derivation unit displays a graph representing temporal transition of signal values in the imaging region for each tissue.   The reception unit further receives at least one change instruction among a tag pulse TI (Inversion Time), selection or non-selection or number of the plurality of types of tissue, and application timing of the prepulse, and the derivation unit includes: The magnetic resonance imaging apparatus according to claim 1, wherein the application timing of the pre-pulse after the change is derived.