JP4180936B2 - Magnetic resonance imaging device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a magnetic resonance imaging apparatus, and more particularly to a magnetic resonance imaging apparatus using a contrast agent.
[0002]
[Prior art]
In the magnetic resonance imaging apparatus, angiography (MRA: Magnetic Resonance Angiography) using a contrast agent is performed. When imaging the blood vessels of the aortic system to the peripheral part, divide the entire imaging range into multiple areas along the body axis of the target, and sequentially capture the multiple areas while moving the target in the body axis direction (For example, refer to Patent Document 1).
[0003]
[Patent Document 1]
JP 2002-315735 A (7th and 8th pages, FIG. 2)
[0004]
[Problems to be solved by the invention]
In order to optimize the contrast agent concentration in any imaging region, it is necessary to inject an appropriate amount of contrast agent in a timely manner as the imaging progresses, but this requires manual skill to do this manually. .
[0005]
Therefore, an object of the present invention is to realize a magnetic resonance imaging apparatus in which an appropriate amount of contrast medium is injected into a plurality of imaging regions.
[0006]
[Means for Solving the Problems]
The invention according to one aspect for solving the above-described problem is an imaging unit that sequentially moves an object in the body axis direction and sequentially images a plurality of imaging regions set along the body axis using magnetic resonance. Injection means for injecting contrast medium into the target, sequence creation means for creating a contrast medium injection sequence based on the imaging protocol of the imaging means, and control means for controlling the injection means based on the sequence; And a magnetic resonance imaging apparatus.
[0007]
In the present invention, the sequence creation means creates the contrast medium injection sequence based on the imaging protocol, and the control means controls the injection means based on the sequence. The appropriate amount of injection is automated.
[0008]
The movement is preferably movement from the upstream side to the downstream side of the blood flow in terms of the flow of the contrast agent. The movement is preferably movement from the trunk to the lower limbs in terms of photographing the aortic system.
[0009]
It is preferable that the protocol includes information related to the imaging time and the moving time of the target for the imaging region in terms of appropriately creating a sequence. The sequence preferably includes information on the contrast medium injection amount and the injection speed for each imaging region from the viewpoint of appropriately performing injection control. It is preferable that the sequence includes information regarding the timing of contrast medium injection for each imaging region in that the contrast medium is injected in a timely manner.
[0010]
It is preferable that the total amount of contrast medium injected into the plurality of imaging regions is constant in that the injection amount is fixed regardless of the number of imaging regions. The total amount of the contrast agent is preferably determined according to the body weight of the subject from the viewpoint of optimizing the injection amount.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The present invention is not limited to the embodiment. FIG. 1 shows a block diagram of the magnetic resonance imaging apparatus. An example of an embodiment relating to the apparatus of the present invention is shown by the configuration of the apparatus.
[0012]
As shown in the figure, this apparatus has a magnet system 100. The magnet system 100 includes a main magnetic field coil unit 102, a gradient coil unit 106, and an RF coil unit 108. Each of these coil portions has a substantially cylindrical shape and is arranged coaxially with each other. A subject 1 to be imaged is loaded into a cradle 500 and carried into a generally cylindrical internal space (bore) of the magnet system 100.
[0013]
A contrast medium is injected into the object 1 by the contrast medium injection unit 110. As the contrast medium, for example, a contrast medium mainly composed of gadolinium (Gd) is used. The contrast agent is injected into the subject 1 by, for example, intravenous injection.
[0014]
The cradle 500 is driven by the cradle driving unit 120. Thereby, the object 1 can be moved in the body axis direction in the internal space of the magnet system. The movement in the body axis direction is performed when the imaging area of the target 1 is changed as will be described later.
[0015]
The main magnetic field coil unit 102 forms a static magnetic field in the internal space of the magnet system 100. The direction of the static magnetic field is generally parallel to the direction of the body axis of the object 1. That is, a so-called horizontal magnetic field is formed. The main magnetic field coil unit 102 is configured using, for example, a superconducting coil. In addition, you may comprise using not only a superconductive coil but a normal conductive coil.
[0016]
The gradient coil section 106 generates three gradient magnetic fields for giving gradients to the static magnetic field strength in the directions of three axes perpendicular to each other, that is, the slice axis, the phase axis, and the frequency axis.
[0017]
When the coordinate axes perpendicular to each other in the static magnetic field space are x, y, and z, any of the axes can be a slice axis. In that case, one of the remaining two axes is a phase axis, and the other is a frequency axis. In addition, the slice axis, the phase axis, and the frequency axis can have arbitrary inclinations with respect to the x, y, and z axes while maintaining the perpendicularity therebetween. This is also referred to as an oblique. In this device, the direction of the body axis of the target 1 is the z-axis direction.
[0018]
The gradient magnetic field in the slice axis direction is also called a slice gradient magnetic field. The gradient magnetic field in the phase axis direction is also referred to as a phase encode gradient magnetic field or a phase encode gradient magnetic field. The gradient magnetic field in the frequency axis direction is also referred to as a read out gradient magnetic field. The readout gradient magnetic field is synonymous with the frequency encoding gradient magnetic field. In order to make it possible to generate such a gradient magnetic field, the gradient coil unit 106 has three gradient coils (not shown). Hereinafter, the gradient magnetic field is also simply referred to as a gradient.
[0019]
The RF coil unit 108 forms a high-frequency magnetic field for exciting spins in the body of the target 1 in the static magnetic field space. Hereinafter, the formation of a high-frequency magnetic field is also referred to as transmission of an RF excitation signal. The RF excitation signal is also referred to as an RF pulse. An electromagnetic wave generated by the excited spin, that is, a magnetic resonance signal is received by the RF coil unit 108.
[0020]
The magnetic resonance signal is a signal in the frequency domain (Fourier) space. Since the magnetic resonance signal is encoded in two axes by the gradient in the phase axis direction and the frequency axis direction, the magnetic resonance signal is obtained as a signal in a two-dimensional Fourier space. The phase encoding gradient and readout gradient determine the sampling position of the signal in two-dimensional Fourier space. Hereinafter, the two-dimensional Fourier space is also referred to as k-space.
[0021]
A gradient driving unit 130 is connected to the gradient coil unit 106. The gradient driving unit 130 gives a driving signal to the gradient coil unit 106 to generate a gradient magnetic field. The gradient drive unit 130 has three systems of drive circuits (not shown) corresponding to the three systems of gradient coils in the gradient coil unit 106.
[0022]
An RF drive unit 140 is connected to the RF coil unit 108. The RF drive unit 140 gives a drive signal to the RF coil unit 108 and transmits an RF pulse to excite spins in the body of the subject 1.
[0023]
A data collection unit 150 is connected to the RF coil unit 108. The data collection unit 150 collects reception signals received by the RF coil unit 108 as digital data.
[0024]
A sequence control unit 160 is connected to the contrast medium injection unit 110, the cradle driving unit 120, the gradient driving unit 130, the RF driving unit 140, and the data collection unit 150. The sequence control unit 160 controls the contrast medium injection unit 110 to the data collection unit 150 to perform contrast medium injection, cradle movement, and magnetic resonance signal collection.
[0025]
The sequence control unit 160 is configured using, for example, a computer. The sequence control unit 160 has a memory (not shown). The memory stores a program for the sequence control unit 160 and various data. The function of the sequence control unit 160 is realized by the computer executing a program stored in the memory.
[0026]
The output side of the data collection unit 150 is connected to the data processing unit 170. Data collected by the data collection unit 150 is input to the data processing unit 170. The data processing unit 170 is configured using, for example, a computer. The data processing unit 170 has a memory (not shown). The memory stores a program for the data processing unit 170 and various data.
[0027]
The data processing unit 170 is connected to the sequence control unit 160. The data processing unit 170 is above the sequence control unit 160 and controls it. The function of this apparatus is realized by the data processing unit 170 executing a program stored in the memory.
[0028]
The data processing unit 170 stores the data collected by the data collection unit 150 in a memory. A data space is formed in the memory. This data space corresponds to k-space. The data processing unit 170 reconstructs an image by performing two-dimensional inverse Fourier transform on k-space data.
[0029]
A display unit 180 and an operation unit 190 are connected to the data processing unit 170. The display unit 180 is configured by a graphic display or the like. The operation unit 190 includes a keyboard having a pointing device.
[0030]
The display unit 180 displays the reconstructed image and various information output from the data processing unit 170. The operation unit 190 is operated by the user and inputs various commands and information to the data processing unit 170. The user operates the apparatus interactively through the display unit 180 and the operation unit 190.
[0031]
FIG. 2 shows a block diagram of another type of magnetic resonance imaging apparatus. The magnetic resonance imaging apparatus shown in the figure is an example of an embodiment of the present invention. An example of an embodiment relating to the apparatus of the present invention is shown by the configuration of the apparatus.
[0032]
This apparatus has a magnet system 100 ′ having a different system from the apparatus shown in FIG. Except for the magnet system 100 ′, the configuration is the same as that of the apparatus shown in FIG.
[0033]
The magnet system 100 ′ includes a main magnetic field magnet unit 102 ′, a gradient coil unit 106 ′, and an RF coil unit 108 ′. Each of the main magnetic field magnet section 102 'and each coil section is composed of a pair of facing each other across a space. Moreover, all have a substantially disk shape and are arranged sharing a central axis. The object 1 is mounted on the cradle 500 and carried into and out of the internal space (bore) of the magnet system 100 ′ by a conveying means (not shown).
[0034]
The main magnetic field magnet unit 102 ′ forms a static magnetic field in the internal space of the magnet system 100 ′. The direction of the static magnetic field is substantially orthogonal to the body axis direction of the target 1. That is, a so-called vertical magnetic field is formed. The main magnetic field magnet section 102 ′ is configured using, for example, a permanent magnet. In addition, you may comprise using not only a permanent magnet but a superconductive electromagnet or a normal electromagnet.
[0035]
The gradient coil section 106 ′ generates three gradient magnetic fields for giving a gradient to the static magnetic field strength in the directions of three axes perpendicular to each other, that is, the slice axis, the phase axis, and the frequency axis.
[0036]
When the coordinate axes perpendicular to each other in the static magnetic field space are x, y, and z, any of the axes can be a slice axis. In that case, one of the remaining two axes is a phase axis, and the other is a frequency axis. In addition, the slice axis, the phase axis, and the frequency axis can have an arbitrary inclination with respect to the x, y, and z axes while maintaining the perpendicularity therebetween, that is, oblique. Also in this apparatus, the direction of the body axis of the target 1 is the z-axis direction. In order to enable generation of gradient magnetic fields in the three-axis directions, the gradient coil unit 106 'has three gradient coils (not shown).
[0037]
The RF coil unit 108 ′ transmits an RF pulse for exciting the spin in the body of the subject 1 to the static magnetic field space. The electromagnetic wave generated by the excited spin, that is, the magnetic resonance signal is received by the RF coil unit 108 ′. A reception signal of the RF coil unit 108 ′ is input to the data collection unit 150.
[0038]
FIG. 3 shows an example of a pulse sequence used for magnetic resonance imaging. This pulse sequence is a pulse sequence of the spin echo (SE: SpinEcho) method.
[0039]
That is, (1) is a sequence of 90 ° pulses and 180 ° pulses for RF excitation in the SE method, and (2), (3), (4) and (5) are respectively the slice gradient Gs and the lead. This is a sequence of an out gradient Gr, a phase encode gradient Gp, and a spin echo MR. The 90 ° pulse and the 180 ° pulse are represented by center signals. The pulse sequence proceeds from left to right along the time axis t.
[0040]
As shown in the figure, 90 ° excitation of spin is performed by a 90 ° pulse. At this time, the slice gradient Gs is applied, and selective excitation for a predetermined slice is performed. After a predetermined time from the 90 ° excitation, 180 ° excitation by a 180 ° pulse, that is, spin inversion is performed. At this time, the slice gradient Gs is applied, and selective inversion is performed for the same slice.
[0041]
In the period between 90 ° excitation and spin reversal, a readout gradient Gr and a phase encode gradient Gp are applied. Spin dephase is performed by the lead-out gradient Gr. Spin phase encoding is performed by the phase encoding gradient Gp.
[0042]
After the spin inversion, the spin is rephased at the readout gradient Gr to generate the spin echo MR. The spin echo MR is collected as view data by the data collecting unit 150. Such a pulse sequence is repeated 64 to 512 times with a period TR (repetition time). The phase encoding gradient Gp is changed every time it is repeated, and a different phase encoding is performed each time. Thereby, view data of 64 to 512 views is obtained.
[0043]
Another example of a pulse sequence for magnetic resonance imaging is shown in FIG. This pulse sequence is a pulse sequence of a gradient echo (GRE) method.
[0044]
That is, (1) is a sequence of α ° pulses for RF excitation in the GRE method, and (2), (3), (4), and (5) are slice gradient Gs, readout gradient Gr, It is a sequence of a phase encoding gradient Gp and a gradient echo MR. The α ° pulse is represented by a center signal. The pulse sequence proceeds from left to right along the time axis t.
[0045]
As shown in the figure, the α ° excitation of the spin is performed by the α ° pulse. α is 90 or less. At this time, the slice gradient Gs is applied, and selective excitation for a predetermined slice is performed.
[0046]
After the α ° excitation, spin phase encoding is performed by the phase encoding gradient Gp. Next, the spin is first dephased by the readout gradient Gr, and then the spin is rephased to generate a gradient echo MR. The gradient echo MR is collected as view data by the data collection unit 150. Such a pulse sequence is repeated 64 to 512 times with a period TR. The phase encoding gradient Gp is changed every time it is repeated, and a different phase encoding is performed each time. Thereby, view data of 64 to 512 views is obtained.
[0047]
View data obtained by the pulse sequence of FIG. 3 or 4 is collected in the memory of the data processing unit 170. Note that the pulse sequence is not limited to the SE method or the GRE method. For example, the pulse sequence may be one of other appropriate techniques such as a fast spin echo (FSE) method and an echo planar imaging (EPI). Needless to say, it is good. The data processing unit 170 reconstructs an image based on the view data collected in the memory.
[0048]
When imaging an aortic blood vessel from the main trunk to the distal part, the entire imaging range is divided into a plurality of regions along the body axis of the subject 1, and the regions are sequentially moved while moving the subject in the body axis direction. Take a picture.
[0049]
FIG. 5 shows an example of a plurality of imaging regions. (A) of the same figure is the figure seen from the front side of the object 1, (b) is the figure seen from the side surface side. As shown in the figure, the entire photographing range is divided into three regions, namely photographing regions 12, 14, and 16. The imaging region 12 is an abdominal region. The imaging region 14 is a region for the pelvis. The imaging region 16 is a region for the lower limbs.
[0050]
The size of each area is such that the apparatus can shoot at once. That is, the size is equal to or smaller than the effective photographing space of the magnet system 100 (100 ′). Each region has a different size in the thickness direction of the body of the object 1. That is, the imaging region 12 for the abdomen is the largest, the imaging region 14 for the pelvis is next to it, and the imaging region 16 for the lower limbs is the smallest. Note that the number and size of the imaging regions are not limited to this and may be appropriate. Moreover, you may overlap partially.
[0051]
FIG. 6 shows a flow diagram of the operation of this apparatus. As shown in the figure, in step 601, a photographing protocol (protocol) is set. The shooting protocol is set through the display unit 180 and the operation unit 190 by the user. Thereby, for example, the positions and sizes of the imaging regions 12 to 16 and the moving time between the imaging regions are set. In addition, shooting conditions for each shooting area are set.
[0052]
Next, in step 603, data regarding the contrast agent is input. This is also performed by the user through the display unit 180 and the operation unit 190. As a result, data relating to the type of contrast agent to be used and the total injection amount are input. For example, 20 cc is input as the total injection amount data.
[0053]
Since the total injection amount has a predetermined relationship with the weight of the subject, when the data processing unit 170 stores the relationship, the weight of the subject 1 may be input instead of the total injection amount. By using the body weight as a reference, it becomes easy to optimize the injection amount for each subject.
[0054]
Next, in step 605, a contrast agent injection sequence is created. The creation of the contrast agent injection sequence is performed by the data processing unit 170 based on the imaging protocol. From the imaging protocol, the respective imaging times and moving times between the imaging regions 12 to 16 are known, and the blood flow in each imaging region is known by prior measurement or the like. It is possible to obtain the injection amount and the injection speed for setting the contrast medium concentration at a predetermined value together with the timing.
[0055]
As a result, for example, when the imaging region 12 has an imaging time of 30 sec, a sequence in which the injection amount and the injection speed are 10 cc and 4 cc / sec, respectively, is created. When the imaging time is 15 sec, the injection amount and the injection speed are set to 5 cc and 2 cc / sec, respectively. Sequences of 5 cc and 1 cc / sec are created. As a result, an injection sequence for the imaging region is maintained while maintaining the total injection amount of 20 cc.
[0056]
Next, in step 607, an injection sequence is set in the control unit. Thereby, the contrast agent injection sequence is set from the data processing unit 170 to the sequence control unit 160.
[0057]
Next, contrast imaging is executed in step 609. Contrast imaging is performed under the control of the sequence control unit 160 in parallel with the contrast medium injection by the contrast medium injection unit 110, the magnet system 100 (100 ′), the cradle driving unit 120, the data collection unit 150, and the data processing unit 170. It is performed by the photographing unit consisting of
[0058]
Contrast imaging is performed in the order of the imaging areas 12, 14, and 16. That is, it is performed while moving the imaging region sequentially from the upstream side to the downstream side along the flow of arterial blood. Thereby, it is possible to perform imaging along the flow of the contrast agent. Since this movement is also a movement from the trunk to the lower limbs, an aortic blood vessel can be appropriately imaged.
[0059]
The injection of the contrast agent is automatically controlled by the sequence control unit 160 according to the injection sequence. As a result, the injection amount, the injection speed, and the injection timing at each stage are automatically controlled, so that manual operation requiring skill is not required.
[0060]
In addition, since the injection sequence is automatically created in accordance with the imaging protocol under a predetermined total injection volume, the total injection volume can be correctly injected as specified. Further, since the total injection amount is constant regardless of the number of imaging regions, the consumption amount does not increase even if the number of imaging regions increases.
[0061]
FIG. 7 shows a functional block diagram of the apparatus focusing on contrast imaging. As shown in the figure, the apparatus includes an imaging unit 702, a sequence creation unit 704, a control unit 706, and an injection unit 708. Based on the imaging protocol of the imaging unit 702, a contrast medium injection sequence is generated by the sequence generation unit 704 and supplied to the control unit 706. The control unit 706 controls the injection unit according to the contrast agent injection sequence.
[0062]
The imaging unit 702 is an example of an embodiment of an imaging unit in the present invention. This corresponds to a function of a part including the magnet system 100 (100 ′), the cradle driving unit 120, the data collecting unit 150, and the data processing unit 170.
[0063]
The sequence creation unit 704 is an example of an embodiment of sequence creation means in the present invention. This corresponds to the function of the data processing unit 170 that performs the processing in step 605.
[0064]
The control unit 706 is an example of an embodiment of control means in the present invention. This corresponds to the function of the sequence control unit 160 when performing contrast imaging in step 609. Injection unit 708 is an example of an embodiment of the injection means in the present invention. This corresponds to the function of the contrast medium injection unit 110.
[0065]
【The invention's effect】
As described in detail above, according to the present invention, it is possible to realize a magnetic resonance imaging apparatus in which an appropriate amount of contrast medium is injected into a plurality of imaging regions.
[Brief description of the drawings]
FIG. 1 is a block diagram of an exemplary apparatus according to an embodiment of the present invention.
FIG. 2 is a block diagram of an exemplary apparatus according to an embodiment of the present invention.
FIG. 3 is a diagram showing an example of a pulse sequence executed by an example apparatus according to an embodiment of the present invention.
FIG. 4 is a diagram showing an example of a pulse sequence executed by an example apparatus according to an embodiment of the present invention.
FIG. 5 is a diagram illustrating a plurality of imaging regions.
FIG. 6 is a flowchart of the operation of the apparatus according to the embodiment of the present invention.
FIG. 7 is a functional block diagram of an apparatus according to an example of an embodiment of the present invention.
[Explanation of symbols]
1 Target 100, 100 'Magnet system 102 Main magnetic field coil unit 102' Main magnetic field magnet unit 106, 106 'Gradient coil unit 108, 108' RF coil unit 130 Gradient drive unit 140 RF drive unit 160 Data collection unit 160 Sequence control unit 170 Data processing unit 180 Display unit 190 Operation unit 500 Cradle 12-16 Imaging region 702 Imaging unit 704 Sequence creation unit 706 Control unit 708 Injection unit

Claims (5)

An imaging means for moving the object in the body axis direction and sequentially imaging a plurality of imaging regions set along the body axis using magnetic resonance;
Shooting protocol setting means for setting the position and size of the plurality of shooting areas and the movement time between the shooting areas;
Injection means for injecting a contrast agent into the object;
Contrast medium data input means for inputting the total injection amount of the contrast medium;
Sequence creation means for creating a contrast agent injection sequence by obtaining the contrast agent injection amount, injection speed and injection timing in each of the imaging regions based on the setting of the imaging protocol setting means and the input of the contrast agent data input means When,
A magnetic resonance imaging apparatus comprising: a control unit that controls the imaging unit based on a setting of the imaging protocol setting unit and controls the injection unit based on a sequence created by the sequence creation unit .   The magnetic resonance imaging apparatus according to claim 1, wherein the movement in the body axis direction of the object is movement from an upstream side to a downstream side of a blood flow.   The magnetic resonance imaging apparatus according to claim 1, wherein the movement of the object in the body axis direction is movement from the trunk to the lower limbs.   The magnetic resonance imaging apparatus according to any one of claims 1 to 3, wherein a total injection amount of the contrast medium injected into the object is constant.   The magnetic resonance imaging apparatus according to claim 4, wherein the total injection amount of the contrast agent is determined according to the weight of the subject.

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