JP2004141269A - Magnetic resonance imaging apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an MRI apparatus having a function automatically providing an orthogonal image by a simple operation in a transdermal therapy and a surgical operation mainly requiring an imaging diagnosis and an orthogonal cross section. <P>SOLUTION: This MRI apparatus executes imaging sequence impressing a static magnetic field, a high frequency pulse and a gradient magnetic field on a subject, receives a magnetic resonance signal generated from the subject and creates a tomogram image based on the received magnetic resonance signal. This apparatus introduces a means specifying a point of a part of an imaging object on a displayed tomogram image and calculating two-cross-sectional or three-cross-sectional position information including the point and the present displayed image and a means automatically setting the imaging sequence by the calculated position information. This constitution allows an operator to obtain three-cross-sectional image information by just specifying the point on the displayed image and improves the usability of the MRI apparatus. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a magnetic resonance imaging apparatus (hereinafter, referred to as an MRI apparatus), and in particular, facilitates positioning of an imaging section desired by an operator, and automatically captures 2 to 3 sections by setting points and lines. The present invention relates to an MRI apparatus having a function of performing an operation.
[0002]
[Prior art]
In recent years, as a new use of MRI, interventional MRI / intraoperative MRI (I-MRI) has begun to spread. Comparing I-MRI with an intraoperative monitor using other imaging modalities, I-MRI has (1) superior soft tissue delineation ability, (2) no radiation exposure, (3) imaging of any cross section, ( 4) It is an advantage that the temperature can be monitored. Treatment methods performed by I-MRI include laser treatment, injection of drugs such as ethanol, radiofrequency ablation, ultrasonic treatment, percutaneous treatment such as bass treatment, and surgical craniotomy / laparotomy such as tumor resection. There are surgery performed. In these treatments, the role of MRI is to guide the puncture needle or tubule to the affected area by real-time imaging, visualize tissue changes during treatment, and monitor local temperature during heating / cooling treatment. In particular, by performing MRI imaging during surgery, it is possible to grasp the deformation of the organ caused by craniotomy or laparotomy. For example, when the pressure in the brain changes due to craniotomy, the shape of the brain changes before and after the craniotomy. This is called a brain shift. The information of a detailed surgical plan obtained by acquiring images by MRI or other modalities before the operation slightly changes. Therefore, the surgeon can obtain more accurate information by measuring an image showing the influence of the brain shift by MRI during the operation. Furthermore, when the tumor and the healthy tissue are sometimes indistinguishable with the naked eye, surgery was conventionally performed based on the images measured before the operation and the experience of the operator, but by performing MRI imaging during the operation, In addition, since the state of the tissue at the time of tumor resection, which has been unobservable until now, can be confirmed on the image, the tumor resection rate can be improved. Intraoperative MRI imaging can be said to be very effective because an increase in the tumor resection rate leads to an increase in the postoperative patient survival rate.
[0003]
However, it is difficult to perform the entire operation of the operation over many hours in an MRI apparatus. This is because, in addition to the problem of the working space, a large number of MRI-compatible instruments are required as compared with the percutaneous treatment. In the vertical magnetic field method in which the magnets are positioned vertically, the working space in the vertical direction is limited, so that the surgical instrument cannot be handled as desired, and the posture of the operator becomes unnatural, so it is difficult to maintain the same posture for a long time.
[0004]
Therefore, in image diagnosis using an MRI apparatus and in a surgery support system using an MRI apparatus, there is a strong demand to shorten the time required for MRI imaging in order to shorten the operation time. As one of the means, it is required to easily set a tomographic plane including a target part to be photographed.
[0005]
In general, when imaging is performed by an MRI apparatus, it is necessary to position the surface in order to image a tomographic plane having a desired position and inclination, and conventionally, the following method is used.
[0006]
The first technique is to image a reference tomographic plane and display it as a two-dimensional image. Then, using this as a reference image, a method of setting an orthogonal cross section including the region of interest of the reference image is set. One or two cross sections are mainly used for the reference image in many cases. For example, first, a transversal (hereinafter, TRS) section of the subject is imaged at the center of the magnetic field, and then, using this as a reference image, a sagittal (hereinafter, SAG) section including the region of interest is imaged. Finally, the oblique section inclined from the coronal (Coron) section is imaged using the TRS section and the SAG section as reference images. Alternatively, first, a multi-slice tomographic image of the TRS section of the subject is captured at the center of the magnetic field, and an oblique section tilted from the COR section is captured using any two sections as reference images from the multi-slice tomographic image. Such a method is disclosed in, for example, JP-A-06-217958 and JP-A-2002-34949.
[0007]
A second method is to use a Graphical User Interface (hereinafter, GUI) to rotate and move an imaging section by clicking a button provided on the GUI. This method is effective mainly for perspective imaging. For example, A. B. Kerr et al., "Real-Time Interactive MRI on a Conventional Scanner" (Magnetic Resonance in Medicine, 38, pp. 355-367 (1997)).
[0008]
The third method is a method using a three-dimensional mouse or the like, which is used to rotate or move the imaging section. This method is effective mainly for perspective imaging. For example, it is disclosed in US Pat. No. 5,512,827.
[0009]
The fourth method is a method of determining an imaging section by a tomographic plane indicating device operated by an operator, and is particularly suitable when a tomographic image including a puncture needle or a surgical instrument is to be perspectively imaged. For example, there is a method as proposed in USP-5365927 and USP-6026315. In USP-5365927, a light emitting diode is provided on a pointer which is a tomographic plane indicating device, and a position indicated by an operator with a pointer is detected by an infrared camera, or a pointer is provided on a tip end of an arm provided with a sensor at a joint. The position of the pointer is detected based on the angle of the joint of the arm and the like, and the position of the imaging surface is automatically adjusted based on the detected position. USP-6026315 is for automatically determining and photographing a designated tomographic plane using two infrared cameras and a pointer having three reflecting spheres.
[0010]
According to the first to third methods, the position and the direction of the section to be photographed must be adjusted and set by an input means such as a mouse, and the determination of the section is very complicated. The fourth method is excellent in that the position and direction of the cross section to be imaged can be adjusted and set more easily, but it is excellent in image diagnosis using a general MRI apparatus, percutaneous treatment, surgery, and the like. Considering the use of this method, this method requires tools and devices for setting, and in consideration of their preparation, the efficiency is low, and there are many restrictions on device installation and detection.
[0011]
[Problems to be solved by the invention]
When considering image diagnosis using an MRI apparatus or percutaneous treatment or surgery that mainly requires images of orthogonal cross sections, it is necessary to provide a function that can automatically obtain orthogonal images with simple operations. It contributes to improvement, that is, shortening of operation time.
[0012]
An object of the present invention is to realize an MRI apparatus having a function of obtaining two or three cross sections related to a desired imaging region by a simple operation.
[0013]
[Means for Solving the Problems]
The above problem can be solved by introducing the following means.
[0014]
That is, an imaging sequence in which a static magnetic field, a high-frequency pulse, and a gradient magnetic field are applied to the subject is executed, a magnetic resonance signal generated from the subject is received, and a tomographic image is generated based on the received magnetic resonance signal. In an MRI apparatus that displays
It has a display means for displaying the photographed image, and further has an input means for specifying and specifying the position of the target region on the displayed MR image, and passes through one point specified on the display screen by the input means. This is achieved by making it possible to photograph two or three sections.
[0015]
Thus, the operator can obtain image information of three cross sections simply by specifying one point on the display image, and can improve the usability of the MRI apparatus.
[0016]
Alternatively, image information of two cross sections can be obtained simply by specifying a line on the display screen, and image information of three cross sections can be obtained by specifying one point.
[0017]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
[0018]
(1st Embodiment)
FIG. 1 is a schematic diagram showing the overall configuration of the MRI apparatus according to the first embodiment of the present invention. The MRI apparatus generates a static magnetic field generating magnetic circuit 102 for generating a uniform static magnetic field B0 inside the subject 101, and gradient magnetic fields Gx, Gy, and Gz whose intensities linearly change in three directions of X, Y, and Z. The generated gradient magnetic field coils 109a and 109b, the transmission coil 114a for applying a high-frequency magnetic field toward the subject 101, the detection coil 114b for detecting a magnetic resonance signal generated from the subject 101, the gradient magnetic field, and a high-frequency pulse having a predetermined intensity 107, a computer 108 for performing various processes such as sequencer control and image processing, and a signal including a ROM 124, a RAM 125, a magnetic disk 126, a magneto-optical disk 127, and a display 128 for displaying and storing images. A processing system 106, a keyboard 12 for performing operations such as setting various parameters and imaging cross sections And configured to have an operation unit 121 or the like including a mouse 123. The shim coil 118 and the shim power supply 119 for driving the shim coil 118 are for finely adjusting the uniformity of the uniform static magnetic field space generated by the static magnetic field generating magnetic circuit 102.
[0019]
Next, an outline of the operation will be described. The high frequency generated by the synthesizer 111 is modulated by the modulator 112, amplified by the power amplifier 113, and supplied to the transmission coil 114a to generate a high frequency magnetic field inside the subject 101 to excite nuclear spins. The magnetic resonance signal emitted from the subject 101 is received by the detection coil 114b, passes through the amplifier 115, is subjected to quadrature phase detection by the detector 116, and is input to the computer 108 via the A / D converter 117. In this embodiment, the transmission coil 114a and the detection coil 114b are provided separately, but may be used for both transmission and reception. After signal processing by the computer 108, images corresponding to the nuclear spin density distribution, relaxation time distribution, spectrum distribution, and the like are displayed on a display 128 such as a CRT. The gradient magnetic field generation system 103 and the transmission system 104 are controlled by a sequencer 107, and the sequencer 107 and the detection system 105 are controlled by a computer 108. The computer 108 is controlled by a command from the operation unit 121.
[0020]
The position and angle of the imaging section are controlled by the static magnetic field strength B0 applied toward the subject, the gradient magnetic field strengths Gx, Gy, Gz, and the frequency f0 of the transmitted high frequency. For example, the resonance frequency of a proton nucleus at a static magnetic field strength of 0.3 T is 12.8 MHz, and if a gradient magnetic field having a strength of 5 mT / m is generated in the slice direction at this time, if the frequency of the high frequency is 12.8 MHz, A cross section at the position of the center of the magnetic field can be imaged, and when the frequency is shifted from 12.8 MHz to 1067 Hz, a cross section at a position shifted by 5 mm from the center of the magnetic field can be obtained as determined by the following equation.
(1067 [Hz] /12.8 [MHz] * 0.3 [T]) / 5 [mT / m] = 5 mm (1)
[0021]
FIG. 2 is a flowchart illustrating the operation of the MRI apparatus according to the present embodiment. First, MR imaging is performed (step 200), and the measured MR image is displayed (step 201).
The imaging position in step 200 may be a position determined by any conventional method, or may be a magnetic field center. Next, one point of interest is designated for the displayed image (step 202).
[0022]
The point of interest is, for example, a tumor to be imaged, or a tip region of a puncture needle or a surgical instrument, and two or three cross sections orthogonal to each other including this one point are imaged (step 203).
[0023]
Specifically, as shown in FIG. 3, when a point of interest 301 on the TRS cross section 300 imaged in step 200 is specified, three cross sections orthogonal to the point are imaging axes x ′, y ′, z of the TRS cross section 300. The SAG section 302 and the COR section 303 which are orthogonal to ′, and the TRS section at the same position as the reference image. Alternatively, a SAG section, a COR section, and a TRS section that are orthogonal to the device axes x, y, and z may be used (not shown).
[0024]
In FIG. 3, when it is desired to image a cross section including the puncture needle 304, the TRS cross section 300 and the COR cross section 303 have high importance, and the SAG cross section 302 may be determined to have low importance. There is also a method of performing puncturing mainly with the image of the TRS section 300 and occasionally checking with the images of the COR section 303 and the SAG section 302. In such a case, any one of the three orthogonal cross sections may be imaged in order to improve the time resolution.
[0025]
As a method of selecting an imaging section, a section selection button 305 is provided next to the display image, and an image of the section selected here is taken. The cross-section selection button 305 can be visually recognized, for example, by highlighting the selected cross-section, and selecting and changing the cross-section, such as selecting with one click and releasing with two clicks. It is configured to be easily implemented.
[0026]
In this manner, two or three orthogonal sections are imaged, and a point of interest is further designated in any of the two or three images displayed as a result, and two orthogonal sections or three sections including the one point are designated. Steps 201 to 203 are repeated so that a cross section is imaged.
[0027]
Thereby, even when the subject moves or the positions of the puncture needle and the surgical instrument change, this position can be easily followed.
[0028]
This embodiment is particularly effective during fluoroscopic imaging, and repeats steps 201 to 203 without interrupting imaging. When the point of interest is designated, the computer 108 calculates the position, calculates the high frequency and the gradient magnetic field strengths Gx, Gy, Gz according to the position, and controls the sequencer 107. The control timing is after the end of the image measurement before the point of interest is designated, that is, at the start of the next image capturing, and the sequencer 107 applies a high frequency and a gradient magnetic field corresponding to a new position to the subject 101.
[0029]
(Second embodiment)
A second embodiment of the present invention will be described with reference to FIGS. In the following embodiments, the overall configuration and operation of the MRI apparatus according to the present invention are the same as those described in the first embodiment.
[0030]
FIG. 4 is a flowchart illustrating the operation of the MRI apparatus according to the present embodiment. First, MR imaging as a first reference image is performed (step 400), and the measured MR image is displayed (step 401). The imaging position in step 400 may be a position determined by a conventional method or a magnetic field center. Next, an attention part is designated by a line in the displayed image (step 402).
[0031]
The site of interest is, for example, a tumor to be imaged, or a puncture needle or a surgical instrument, and a line may be drawn as required, for example, to image a planned puncture path from the tumor to the puncture needle, or to image a cross section including the puncture needle. Then, two cross sections which include this line and are orthogonal to each other are imaged (step 403).
[0032]
The method of drawing a line depends on a general method. For example, a free hand may be used by using a mouse, a pen tablet, a touch panel, or the like as input means, or a straight line may be automatically generated by designating two points. . However, in the case of freehand, it is necessary to interpolate linearly.
[0033]
Specifically, when a straight line 501 is drawn with respect to the TRS section 500 imaged in step 400 as shown in FIG. 5, two sections including the same are a COR section 502 orthogonal to the TRS section 500 and a reference image. It is a TRS cross section at the same position.
[0034]
Steps 401 to 403 are repeated such that imaging of two orthogonal sections is performed in this way, a line is designated again in one of the two images displayed as a result, and two sections including the line are imaged. .
[0035]
Thereby, even when the subject moves or the positions of the puncture needle and the surgical instrument change, this position can be easily followed.
[0036]
This embodiment is particularly effective during fluoroscopic imaging, and repeats steps 401 to 403 without interrupting imaging. When a line is designated, the computer 108 calculates the position, calculates the frequency of the high frequency and the gradient magnetic field strengths Gx, Gy, Gz according to the position, and controls the sequencer 107. The control timing is after the end of the image measurement before designating the target part, that is, at the start of the next image capturing.
[0037]
This embodiment is effective when the COR section to be imaged is not orthogonal to the imaging axes x ′ and y ′ and the apparatus axes x and y of the TRS section 500 as compared with the first embodiment.
[0038]
(Third embodiment)
A third embodiment of the present invention will be described with reference to FIGS. FIG. 6 is a flowchart illustrating the operation of the MRI apparatus according to the present embodiment. First, MR imaging is performed (step 600), and the measured MR image is displayed (step 601). The imaging position in step 600 may be a position determined by a conventional method or a magnetic field center. Next, a point of interest is designated by dots and lines in the displayed image (step 602).
[0039]
For example, the point of interest may be designated by a point and a line by indicating a tumor to be imaged, or a tip of a puncture needle or a surgical instrument, a planned puncture needle path from the tumor to the puncture needle, or a position including the puncture needle by a line. Then, one cross section including the point and the line and two cross sections including the target point orthogonal to the cross section are imaged, that is, a total of three cross sections (step 603).
[0040]
The line is drawn in the same manner as in the second embodiment.
[0041]
Specifically, when a point 701 and a straight line 702 are designated for the TRS section 700 imaged in step 600 as shown in FIG. 7, three sections including this are called a COR section 703 orthogonal to the TRS section 700. A TRS section at the same position as the reference image, and a SAG section 704 including the point 701 and orthogonal to the line 702. Alternatively, the SAG section may be a section 705 orthogonal to the imaging axis x ′ of the TRS section 700.
[0042]
In this manner, three cross sections are imaged, and a point and a line are designated again in any of the three images displayed as a result. Steps 601 to 603 are repeated so as to image two sections, that is, three sections in total.
[0043]
Thereby, even when the subject moves or the positions of the puncture needle and the surgical instrument change, this position can be easily followed.
[0044]
This embodiment is particularly effective during fluoroscopic imaging, and repeats steps 601 to 603 without interrupting imaging. When a point and a line are designated, the computer 108 calculates the position, calculates the frequency of the high frequency and the gradient magnetic field strength Gx, Gy, Gz according to the position, and the sequencer 107 calculates the high frequency and the gradient according to the new position. A magnetic field is applied to the subject 101.
[0045]
This embodiment is different from the second embodiment in that three points can be imaged by specifying points and lines. Since the number of imaging sections is changed from two to three, the time resolution is reduced.
[0046]
【The invention's effect】
According to the present invention, two or three imaging sections can be set by a simple operation, and the usability of the MRI apparatus can be improved and the operation time can be reduced.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing an overall configuration of an MRI apparatus according to the present invention.
FIG. 2 is a flowchart of an operation according to the first embodiment of the present invention.
FIG. 3 is an explanatory view of an orthogonal sectional view obtained by the first embodiment of the present invention.
FIG. 4 is a flowchart of an operation according to the second embodiment of the present invention.
FIG. 5 is an explanatory diagram of an orthogonal cross-sectional view obtained by a second embodiment of the present invention.
FIG. 6 is a flowchart of an operation according to the third embodiment of the present invention.
FIG. 7 is an explanatory diagram of an orthogonal cross-sectional view obtained by a third embodiment of the present invention.
[Explanation of symbols]
101 Subject 102 Static magnetic field generation magnetic circuit 103 Gradient magnetic field generation system 104 Transmission system 105 Detection system 106 Signal processing system 107 Sequencer 108 Computer 109a, b Gradient magnetic field coil 111 Synthesizer 112 Modulator 113 Power amplifier 114a Transmission coil 114b Detection coil 115 Amplifier 116 Detector 117 A / D converter 121 Operation unit 128 Display

Claims (2)

An imaging sequence for applying a static magnetic field, a high-frequency pulse, and a gradient magnetic field to the subject is executed, a magnetic resonance signal generated from the subject is received, and a magnetic resonance tomography of the subject is performed based on the received magnetic resonance signal. In a magnetic resonance imaging apparatus for generating an image and displaying the image on a display device, a point or a straight line or a point and a straight line of a portion to be further photographed on the tomographic image currently displayed on the display device is further displayed. Input means for specifying a combination;
Means for calculating position information of two orthogonal to three cross sections including the tomographic image currently displayed based on the designation by the input means;
and,
A magnetic resonance imaging apparatus comprising: means for generating an imaging sequence of the two or three cross sections based on the position information calculated by the calculation means. 2. The magnetic resonance imaging apparatus according to claim 1, wherein the input means is a mouse, a pen tablet, a touch panel, or a combination thereof.

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