JPH06304153A - Image pickup device using mri device - Google Patents

Abstract

PURPOSE:To pick up an image by the MRI device while successively shifting an examinee. CONSTITUTION:A section 11 which executes the movement and the image pickup at the same time controls a belt conveyor 20 at the speed Gv smaller than or equal to the (Mw-Gw)/Mt, (where, the length in the movement direction of the image pickup range of an MRI device 10 is taken as Mw, the length in the movement direction at the image pickup range as Gw, and the time required to collect one image of data as Mt), and the movement by the belt conveyor 20 and the image pickup by the MRI device 10 are executed at the same time. Thus, the efficiency of picking up the image can be improved.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art An image pickup apparatus including an MRI apparatus and a moving apparatus for moving a subject so as to pass through the bore of the MRI apparatus is disclosed, for example, in Japanese Patent Laid-Open No. 63-272335. When the imaging surface is parallel to the movement direction, this conventional imaging device first stops the movement of the subject G and takes an image to obtain a first image having a length T in the movement direction. next,
After moving by the distance T, the image is stopped and captured again to obtain a second image having a length T in the moving direction. This is repeated n times, and the obtained n images from the 1st to the n-th are stitched together to obtain an image of length nT. FIG. 11 shows a conceptual diagram of the configuration of the conventional image pickup 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 at the time of imaging, and the MRI apparatus 5
It is a part of 0.

[0003]

In the above conventional image pickup apparatus, the MRI apparatus and the moving apparatus do not operate at the same time. That is, the mobile device is stopped when the MRI device takes an image, and the MRI device is stopped when the mobile device moves. Therefore, there is a problem that the imaging efficiency is not good. Therefore, an object of the present invention is to provide an image pickup apparatus capable of picking up an image with an MRI apparatus while continuously moving a subject.

[0004]

An image pickup apparatus using an MRI apparatus of the present invention is an image pickup apparatus which comprises an MRI apparatus and a moving apparatus which relatively moves an object and the MRI apparatus so as to pass through a bore of the MRI apparatus. In the apparatus, the MRI
When the length in the moving direction of the imageable area of the device is Mw and the length in the moving direction of the imaging target range is Gw, the difference between them (Mw-Gw) is the time Mt for collecting data for one image.
A moving / imaging simultaneous executing means for controlling the moving device so as to move at a speed Gv smaller than or equal to the quotient (Mw-Gw) / Mt divided by and moving the imaging by the MRI device simultaneously with the moving. This is a structural feature. In the image pickup apparatus having the above-mentioned configuration, it is preferable to include an excitation region tracking movement unit that moves the position of the excitation region for each view so as to follow the relative movement amount when the image pickup surface is orthogonal to the relative movement direction. In addition, it is preferable that the image pickup apparatus having the above-described configuration includes a phase correction unit that performs a phase correction corresponding to the relative movement amount on the data for each view when the image pickup surface is parallel to the relative movement direction.

[0005]

In the image pickup apparatus using the MRI apparatus of the present invention,
When the moving / imaging simultaneous executing means sets the moving direction length of the imageable area of the MRI apparatus to Mw and the moving direction length of the imaging target range to Gw, the difference (Mw-Gw) between them is 1.
The quotient (Mw) divided by the time Mt for collecting data for the image
Control the moving device to move at a velocity Gv that is less than or equal to −Gw) / Mt. Further, the movement by the moving device and the imaging by the MRI apparatus are simultaneously executed. With the speed Gv of the above condition, data for one image can be collected while the subject is in the imageable region. Further, if the MRI apparatus performs ultra-high-speed imaging within, for example, Mt = several 100 ms, 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, the subject can be imaged while moving continuously without any special correction, and the imaging efficiency can be improved.

Further, when the excitation area tracking movement means is provided and the imaging surface is orthogonal to the relative movement direction, the excitation area tracking movement means moves the position of the excitation area for each view so as to follow the relative movement amount. , It is equivalent to the subject being stationary and does not cause motion artifacts. Therefore, the subject can be imaged with high image quality while continuously moving.

When the image pickup surface 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 is stationary. Is equivalent to the above, and does not cause motion artifacts. Therefore, the subject can be imaged with high image quality while continuously moving.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in more detail based on the embodiments shown in the drawings. The present invention is not limited to this. FIG. 1 is a structural conceptual diagram of an image pickup apparatus 1 using an MRI apparatus according to an embodiment of the present invention. G
Is a subject (not limited to a patient), 20 is a moving device that continuously moves 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,
An axial view interlocking slice moving section 13, a sagittal / coronal SAT applying section 14, a sagittal / coronal phase correcting section 15, and an oblique / 3-dimensional time integrated control section 16 are provided.

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

As shown in FIG. 4, the correction necessity determination unit 12
Is the moving distance G during the acquisition of data for one image.
It is determined whether v · Mt is sufficiently small (12A). If the motion artifact is small enough to be ignored, it is determined that no correction is necessary, and the axial view interlocking slice moving unit 13 and the sagittal / coronal SAT applying unit 14 are determined.
And sagittal / coronal phase corrector 15 and oblique /
The control is returned to the system without starting the three-dimensional time integrated control unit 16 (EXIT1). When control is returned at EXIT1, the system reconstructs the image from the collected data. If it is not sufficiently small, it is determined whether the image pickup surface is an axial image which is orthogonal to the relative movement direction (12B). If it is axial, view-related slice moving unit 13 at the time of axial
Is activated (12C). If it is not axial, it is determined whether the image pickup surface is a sagittal image or a coronal image parallel to the relative movement direction (12D). If it is sagittal or coronal, the sagittal / coronal SAT applying section 14 and the sagittal / coronal phase correcting section 15 are activated (12E).
If it is neither sagittal nor coronal, it is determined whether the imaging surface is oblique with respect to the relative movement direction or three-dimensional imaging (12F). If it is oblique or three-dimensional, the oblique / 3-dimensional time integrated control unit 16 is activated (12G).
If it is neither oblique nor three-dimensional, the view interlocking slice moving unit 13 at the time of axial and the SA at sagittal / coronal
Without activating the T application section 14, the sagittal / coronal phase correction section 15, and the oblique / 3D integration control section 16,
Return control to the system (EXIT2). When control is returned with EXIT2, the system performs error handling.

As shown in FIG. 5, the axial inter-view slice moving unit 13 moves the RF excitation / reversal position so as to follow the movement of the subject G for each view, and collects the data of each view. (13A). The axial view interlocking slice moving unit 13 corresponds to the excitation region tracking moving unit. As shown in FIG. 6, the subject G is G between the views.
Since only v · TR moves, the RF excitation region Ms is also Gv ·
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. Note that the movement of the RF excitation region Ms can be specifically realized by changing the RF frequency for each view, for example.

As shown in FIG. 7, the sagittal / coronal SAT applying unit 14 adds a spatial saturation pulse (spatial SAT pulse) before the normal pulse sequence as necessary, and the subject G for each view is added. MR according to the position of
Limit the signal generation area. Then, the data of each view is collected (14A). As shown in FIG. 8, the subject G is moving in the RF excitation region Ms. Therefore, with respect to the axis that matches the moving direction of the frequency axis direction or the phase axis direction, even the MR signal from the same portion of the subject G has a phase shift for each view. Therefore, the sagittal / coronal phase correction unit 15 uses the data D ′ (f, p) of each view.
On the other hand, 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 the gradient Fw: Imageable area in the frequency axis direction or exp {-j2πpΔy / Pw} p: Data number in the phase axis direction , "(-M / 2) +1"
To “M / 2”. Δy: amount of displacement from the center of the gradient Pw: imageable area in the phase axis direction is multiplied to obtain data D (f, p) of that view (15
A).

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

[0014]

[Equation 1]

Assuming that the x coordinate of the gradient center is x'and the displacement from the gradient center is Δx, x = Δx + x '
It becomes like the formula (2).

[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 center of the gradient. The same applies when moving in the phase axis direction, and the positional deviation Δy from the gradient center
To 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 phase encoding is not in the order of magnitude, correction is performed according to the positional deviations Δx and Δy at each position.
No problem. Further, if the subject G is displaced by a constant distance, linear phase correction may be performed and shift after reconstruction may be performed. However, in the present method, the position of the subject shifts for each phase encoding, so the square of It becomes a phase correction and cannot be corrected after reconstruction.

As shown in FIG. 10, the oblique / 3-dimensional time integrated control unit 16 decides the sharing of each of the axial view interlocking slice moving unit 13 and the sagittal / coronal SAT applying unit 14, and activates them. Data D '(f,
p) is collected (16A). That is, RF excitation / inversion is performed in the same manner as in the axial time, the spatial saturation pulse is performed in the same manner as in the sagittal / coronal time, and the data D ′ (f, p) is collected. Next, the oblique / 3-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 sagittal / coronal phase correction unit 15 performs phase correction for each component to obtain data D (f, p). In the case of three dimensions, the subject G
Is divided into each component in one frequency axis direction and two phase axis directions, and the phase is corrected by the sagittal / coronal phase correction unit 15 to obtain data D (f, p). After this, control is passed to the system. The system is 2 at the time of oblique
Reconstruct the image by performing a dimensional Fourier transform. In the case of 3D, an image is reconstructed by performing 3D Fourier transform.

As can be understood from the above description, according to the image pickup apparatus 1 of the above-mentioned embodiment, the MRI apparatus 10 continuously moves the subject G while the axial image, the sagittal image, and the coronal image are obtained. However, it is possible to take an oblique image or a three-dimensional image. Further, if it is a dedicated machine for capturing only an axial image, the bore 10a may be very short.

For an imaging method that does not use Fourier transform such as spiral scan or 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 a straight line drawn from the origin in space to the echo data point)
This can be dealt with by performing the above-mentioned phase correction corresponding to each data point. In addition, when the moving speed Gv is fast or the echo time TE
Is long, "G
It is preferable to perform motion compensation such as "radient moment nulling." In addition, even in the case of ultra-high-speed imaging, in the case of multi-shot in which RF excitation is divided into several times, the compensation according to the present invention is performed for each shot. Is preferably performed.

[0021]

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

[Brief description of drawings]

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

FIG. 2 is a flowchart of an operation of a moving / 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 of the operation of a correction necessity determination unit.

FIG. 5 is a flowchart showing the operation of the axial-view-related slice moving unit.

FIG. 6 is an explanatory diagram of slice movement during axial movement.

[Fig. 7] Sagittal / SA application section and sagittal at coronal /
It is a flowchart of operation | movement of the phase correction part at the time of coronal.

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

FIG. 9 is an explanatory view of the principle of phase correction at the time of sagittal / coronal.

FIG. 10 is a flowchart of the operation of the oblique / 3-dimensional time integrated control unit.

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

[Description of Reference Signs] 1 Imaging device using MRI device 10 MRI device 10a Bore 11 Moving / imaging simultaneous execution unit 12 Correction necessity determination unit 13 Axial view interlocking slice moving unit 14 Sagittal / coronal SA applying unit 15 Sagittal / Coronal phase correction unit 16 Oblique / 3-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 Repeat time Ms Slice

Claims (3)

[Claims] 1. An image pickup apparatus comprising an MRI apparatus and a moving apparatus which relatively moves an object and the MRI apparatus so as to pass through a bore of the MRI apparatus, wherein a length in a moving direction of an imageable region of the MRI apparatus. Is Mw and the length of the imaging target range in the moving direction is Gw, the difference (M
w-Gw) is divided by the time Mt for collecting data for one image, and the moving device is controlled so as to move at a velocity Gv that is less than or equal to (Mw-Gw) / Mt and M
An image pickup apparatus using an MRI apparatus, which is provided with a movement / imaging simultaneous execution means for executing image pickup by the RI apparatus simultaneously with the movement. 2. The imaging device according to claim 1, further comprising an excitation region tracking movement unit that moves the position of the excitation region for each view in accordance with the relative movement amount when the imaging surface is orthogonal to the relative movement direction. An imaging device using an MRI device characterized by the above. 3. The image pickup device according to claim 1, further comprising phase correction means for performing a phase correction corresponding to the relative movement amount on the data for each view when the image pickup surface is parallel to the relative movement direction. An imaging device using the MRI device.