JP3212751B2 - Imaging device using MRI device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an imaging apparatus using an MRI apparatus, and more particularly, to an imaging apparatus capable of imaging an MRI apparatus while continuously moving a subject.

[0002]

2. Description of the Related Art An imaging apparatus comprising an MRI apparatus and a moving apparatus for moving a subject to pass through the bore of the MRI apparatus is disclosed in, for example, Japanese Patent Application Laid-Open No. 63-272335. When the imaging surface is parallel to the movement direction, the conventional imaging apparatus first stops the movement of the subject G to capture an image, and obtains a first image having a length T in the movement direction. next,
After moving by the distance T, stop again and take an image to obtain a second image having a length T in the moving direction. This is repeated n times, and the obtained first to n-th images are joined to obtain an image of length nT. FIG. 11 shows a conceptual diagram of the configuration of the conventional imaging apparatus. G is the subject (patient), 60
Is a cradle for moving the subject G, 50 is an MRI apparatus, and 50a is a bore. Reference numeral 51 denotes a movement stop control unit that stops the cradle 60 during imaging, and the MRI apparatus 5
Part of zero.

[0003]

In the above-mentioned conventional imaging apparatus, the MRI apparatus and the moving apparatus do not operate at the same time. That is, when imaging is performed by the MRI apparatus, the mobile apparatus is stopped, and when the mobile apparatus is moved, the MRI apparatus is stopped. Therefore, there is a problem that imaging efficiency is not good. Therefore, an object of the present invention is to provide an imaging apparatus capable of imaging an MRI apparatus while continuously moving a subject.

[0004]

An imaging apparatus using an MRI apparatus according to the present invention is an imaging apparatus comprising an MRI apparatus and a moving apparatus for relatively moving a subject and the MRI apparatus so as to pass through the bore of the MRI apparatus. In the apparatus, the MRI
Assuming that the length of the image capturing area of the apparatus in the moving direction is Mw and the length of the imaging target range in the moving direction is Gw, the difference (Mw−Gw) between the two is the time Mt for collecting data for one image.
Moving / imaging simultaneous execution means for controlling the moving device to move at a speed Gv smaller than or equal to the quotient (Mw-Gw) / Mt divided by, and executing imaging by the MRI device simultaneously with the moving. This is a feature of the configuration. In the imaging apparatus having the above-described configuration, it is preferable that the imaging apparatus further includes an excitation area following movement unit that moves the position of the excitation area for each view by following the relative movement amount when the imaging plane is orthogonal to the relative movement direction. In the imaging apparatus having the above-described configuration, it is preferable that the imaging apparatus further includes a phase correction unit that performs a phase correction corresponding to the relative movement amount on the data for each view when the imaging surface is parallel to the relative movement direction.

[0005]

According to the imaging apparatus using the MRI apparatus of the present invention,
The moving / imaging simultaneous execution means sets the difference (Mw-Gw) between the two as 1 when the length of the MRI apparatus in the moving direction of the imageable area is Mw and the length of the MRI apparatus in the moving direction is Gw.
The quotient (Mw) divided by the time Mt for collecting the image data
-Control the mobile device to move at a speed Gv less than or equal to (Gw) / Mt. In addition, the movement by the moving device and the imaging by the MRI device are simultaneously executed. With the speed Gv under the above conditions, data for one image can be collected while the subject is in the imageable area. Also, if ultrahigh-speed imaging of, for example, Mt = several hundreds of ms or less is performed by the MRI apparatus, the movement of the subject is small even if the speed Gv is a practical speed.
There are few virtual images and blurs called motion artifacts, and the image quality does not deteriorate so much. Therefore, it is possible to perform imaging while moving the subject continuously without performing special correction, and it is possible to improve imaging efficiency.

In addition, when an excitation area following movement means is provided and the imaging plane is orthogonal to the relative movement direction, the excitation area following movement means moves the position of the excitation area for each view so as to follow the relative movement amount. This is equivalent to that the subject is stationary, and does not cause motion artifacts. Therefore, high-quality imaging can be performed while continuously moving the subject.

[0007] When the imaging plane is parallel to the relative movement direction and the phase correction means performs a phase correction corresponding to the relative movement amount on the data for each view, the subject becomes stationary. And no motion artifact is generated. Therefore, high-quality imaging can be performed while continuously moving the subject.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in more detail with reference to the embodiment shown in the drawings. It should be noted that the present invention is not limited by this. FIG. 1 is a conceptual diagram of a configuration of an imaging apparatus 1 using an MRI apparatus according to one embodiment of the present invention. G
Is a subject (not limited to a patient), 20 is a moving device for continuously moving the subject G like a belt conveyor, 10 is an MRI device, and 10a is a bore. The MRI apparatus 10
A movement / imaging simultaneous execution unit 11, a correction necessity determination unit 12,
It includes an axial view-linked slice moving unit 13, a sagittal / coronal SAT application unit 14, a sagittal / coronal phase correction unit 15, and an oblique / three-dimensional integrated control unit 16.

As shown in FIG. 2, the simultaneous movement / imaging unit 11 controls the belt conveyor 20 to move the subject G at the moving speed Gv. At the same time, imaging is started at the repetition time TR (11A). When the length of the MRI apparatus 10 in the moving direction of the imageable area is Mw, the length of the imaging target range in the moving direction is Gw, and the time for collecting data for one image is Mt, Gv ≦ (Mw− Gw) / Mt. Thus, data for one image can be collected while the subject G is in the imageable area Mw. FIG. 3 shows a conceptual diagram when the maximum condition Gv = (Mw−Gw) / Mt.
In general, when data for one image is composed of M views, TR = Mt / M.

[0010] As shown in FIG.
Is the moving distance G during the collection of data for one image.
It is determined whether v · Mt is sufficiently small (12A). If the motion artifact is sufficiently small to be negligible, it is determined that no correction is necessary, and the axial-time view-linked slice moving unit 13 and the sagittal / coronal-time SAT applying unit 14 are determined.
And sagittal / coronal phase correction unit 15 and oblique /
Control is returned to the system without activating the three-dimensional integrated control unit 16 (EXIT1). When control returns in EXIT1, the system reconstructs an image from the collected data. If it is not sufficiently small, it is determined whether or not the imaging surface is an axial image orthogonal to the relative movement direction (12B). If axial, the view-linked slice moving unit 13 in the axial direction
Is started (12C). If it is not axial, it is determined whether the imaging surface is to capture a sagittal image or a coronal image parallel to the relative movement direction (12D). If it is sagittal or coronal, the sagittal / coronal SAT application section 14 and the sagittal / coronal phase correction section 15 are activated (12E).
If neither sagittal nor coronal, it is determined whether oblique or three-dimensional imaging is performed on the imaging surface with respect to the relative movement direction (12F). If it is oblique or three-dimensional, the oblique / three-dimensional integrated control unit 16 is started (12G).
If neither oblique nor three-dimensional, the view-linked slice moving unit 13 in the axial direction and the SA in the sagittal / coronal state
Without activating the T application unit 14, the sagittal / coronal phase correction unit 15, and the oblique / three-dimensional time integrated control unit 16,
Control is returned to the system (EXIT2). When control is returned in EXIT2, the system performs error processing.

As shown in FIG. 5, the axial-time view-linked slice moving unit 13 moves the position of RF excitation / inversion so as to follow the movement of the subject G for each view, and collects data of each view. (13A). The axial-time view-linked slice moving unit 13 corresponds to an excitation area tracking moving unit. As shown in FIG. 6, the subject G is G between the views.
Since it moves by v · TR, the RF excitation region Ms is also Gv · TR
Moving by TR is equivalent to the subject G being stationary. Therefore, no motion artifacts occur,
The subject G can be imaged with high image quality while continuously moving. The movement of the RF excitation region Ms can be specifically realized by, for example, changing the RF frequency for each view.

As shown in FIG. 7, the sagittal / coronal SAT applying section 14 adds a spatial SAT pulse before a normal pulse sequence as necessary, and subjects the subject G to each view. MR according to the position of
Restrict the signal generation area. Then, data of each view is collected (14A). As shown in FIG. 8, the subject G is moving in the RF excitation region Ms. For this reason, the phase of the MR signal from the same part of the subject G is shifted from one view to another in the frequency axis direction or the phase axis direction in the moving direction. Therefore, the sagittal / coronal phase correction unit 15 sets the data D ′ (f, p) of each view.
Exp {-j2πfΔx / Fw} f: data number in the frequency axis direction, “(−N / 2) +
It is an integer from 1 ”to“ N / 2. ”Δx: Amount of displacement from the center of gradient Fw: Image-capable area in frequency axis direction or exp ｛−j2πpΔy / Pw｝ p: Data number in phase axis direction , “(−M / 2) +1”
To “M / 2”. Δy: the amount of displacement from the center of gradient Pw: the imageable area in the phase axis direction is multiplied to obtain data D (f, p) of the view (15)
A).

Next, the principle of the phase correction will be described. As shown in FIG. 9, assuming a case of moving in the frequency axis direction, the MR signal D (x, y) from the signal source g (x, y) in the real space
(F, p) can be expressed as in (Equation 1).

[0014]

(Equation 1)

If the x coordinate of the gradient center is x 'and the displacement from the gradient center is Δx, then x = Δx + x',
Equation (2) is obtained.

[0016]

(Equation 2)

Therefore, the phase correction proportional to fΔx may be performed on the echo data D ′ (f, p) measured at the position of the positional deviation Δx from the gradient center. The same applies to the case of moving in the phase axis direction, and the positional deviation Δy from the gradient center
The echo data D ′ (f, p) measured at the position
The phase correction may be performed in proportion to y. Even if the order of the phase encoding is not in the order of the magnitude, the phase is corrected according to the positional deviations Δx and Δy at the respective positions.
No problem. In addition, if the subject G is only displaced by a fixed distance, linear phase correction may be performed, and a shift after reconstruction may be performed. However, in this method, since the position of the subject is displaced for each phase encoding, the square is used. Phase correction is performed, and correction after reconstruction cannot be performed.

As shown in FIG. 10, the oblique / three-dimensional integrated control unit 16 determines the sharing between the axial-view-linked slice moving unit 13 and the sagittal / coronal SAT application unit 14 and activates them. Data D ′ (f,
Collect p) (16A). That is, the RF excitation / inversion is performed in the same manner as in the axial case, the spatial saturation pulse is performed in the same manner as in the sagittal / coronal case, and data D ′ (f, p) is collected. Next, the oblique / three-dimensional integrated control unit 16
At the time of oblique, the movement of the subject G is divided into components in the frequency axis direction and the phase axis direction, and the phase is corrected by the sagittal / coronal phase correction unit 15 to obtain data D (f, p). In the three-dimensional case, the subject G
Is divided into one component in one frequency axis direction and two components in the phase axis direction, and the phase is corrected by the sagittal / coronal phase correction unit 15 to obtain data D (f, p). Thereafter, control is passed to the system. The system is 2
An image is reconstructed by performing a four-dimensional Fourier transform. In the case of three dimensions, the image is reconstructed by performing a three-dimensional Fourier transform.

As will be understood from the above description, according to the imaging apparatus 1 of the above embodiment, the MRI apparatus 10 moves the subject G continuously, and outputs an axial image, a sagittal image, or a coronal image. However, an oblique image or a three-dimensional image can be taken. In addition, if a dedicated machine that captures only an axial image is used, the bore 10a may be very short.

For an imaging method that does not use a Fourier transform such as a spiral scan or a filtered back projection method, the imaging surface changes the RF frequency for each view, and the reading using the gradient magnetic field is performed in the reading direction (k
Direction of the line drawn from the origin in space to the echo data point)
By performing the above-described phase correction according to the above for each data point. Also, when the moving speed Gv is high or when the echo time TE
Is longer, "G
It is preferable to perform motion correction such as "radient moment nulling". Even in the case of the ultra-high-speed imaging method, in the case of a multi-shot in which RF excitation is divided into several times, the correction according to the present invention is performed for each shot. Is preferably performed.

[0021]

According to the imaging apparatus using the MRI apparatus of the present invention, it becomes possible to image the MRI apparatus while continuously moving the subject. Therefore, the imaging efficiency can be improved.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an embodiment of an imaging apparatus using an MRI apparatus of the present invention.

FIG. 2 is a flowchart of an operation of a movement / imaging simultaneous execution unit.

FIG. 3 is an explanatory diagram of a relationship among an imageable area, a data collection time, and a moving speed.

FIG. 4 is a flowchart illustrating the operation of a correction necessity determination unit;

FIG. 5 is a flowchart of the operation of a view-linked slice moving unit at the time of axial.

FIG. 6 is an explanatory diagram of slice movement at the time of axial.

FIG. 7 shows a sagittal / coronal SA applying portion and a sagittal /
It is a flowchart of operation | movement of a phase correction part at the time of a coronal.

FIG. 8 is an explanatory diagram of movement of a subject during sagittal / coronal.

FIG. 9 is a diagram illustrating the principle of phase correction at the time of sagittal / coronal.

FIG. 10 is a flowchart of the operation of the oblique / three-dimensional integrated control unit.

FIG. 11 is a configuration diagram of an example of an imaging apparatus using a conventional MRI apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Imaging apparatus using MRI apparatus 10 MRI apparatus 10a Bore 11 Simultaneous movement / imaging execution part 12 Correction necessity determination part 13 Axial view interlocking slice movement part 14 Sagittal / coronal SA application part 15 Sagittal / coronal phase correction part 16 Oblique / three-dimensional integrated control unit 20 Belt conveyor G Subject Mw Imageable area Gw Imaging target range Mt Time to collect data for one image Gv Moving speed TR Repetition time Ms Slice

Claims (3)

(57) [Claims] 1. An imaging apparatus comprising an MRI apparatus and a moving apparatus for relatively moving a subject and an MRI apparatus to pass through a bore of the MRI apparatus, wherein a length of the MRI apparatus in a moving direction of an imageable area of the MRI apparatus. Is defined as Mw, and the length of the imaging target range in the moving direction is defined as Gw.
w-Gw) divided by the time Mt for collecting data for one image, and controlling the moving device to move at a speed Gv smaller than or equal to (Mw-Gw) / Mt, and controlling the M
An imaging apparatus using an MRI apparatus, comprising a movement / imaging simultaneous execution unit for executing imaging by the RI apparatus simultaneously with the movement. 2. The imaging apparatus according to claim 1, further comprising: an excitation area tracking moving unit that moves the position of the excitation area for each view by following the relative movement amount when the imaging plane is orthogonal to the relative movement direction. An imaging apparatus using an MRI apparatus. 3. The imaging apparatus according to claim 1, further comprising a phase correction unit that performs a phase correction corresponding to the relative movement amount on the data for each view when the imaging surface is parallel to the relative movement direction. An imaging apparatus using an MRI apparatus.