JP2004248683A - Magnetic resonance imaging apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To continuously indicate and display a puncture needle position in an MR image on a display even outside the body by attaching markers which emit an MR signal, to a puncture needle or a puncture needle fixing appliance. <P>SOLUTION: In this magnetic resonance imaging apparatus constituted so as to repeatedly perform measurement for collecting the measuring data of the region to be measured of a subject at every predetermined measuring cycle, the position and direction of the puncture needle are indicated even outside the body before puncturing by attaching the small markers 401 and 402 emitting the MR signals to the puncture needle 400 or the puncture needle fixing appliance to display a surface including the attached markers on an MR image. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a magnetic resonance imaging apparatus (hereinafter, referred to as an MRI apparatus) for obtaining a tomographic image of a desired site of a subject by utilizing a nuclear magnetic resonance (hereinafter, referred to as an NMR) phenomenon, and particularly to a device such as a puncture needle. The present invention relates to an MRI apparatus having a function of delineating its position and direction with respect to a subject on a magnetic resonance image (hereinafter, referred to as an MR image) even when the device is outside the subject.
[0002]
[Prior art]
The MRI apparatus measures a nuclear spin (hereinafter simply referred to as spin) density distribution, relaxation time distribution, and the like at a desired examination site in the subject by utilizing the NMR phenomenon, and uses the measured data to determine the inspection site of the subject. Are displayed as images.
[0003]
As an imaging sequence in the MRI apparatus, in addition to a basic imaging sequence such as a spin echo method and a gradient echo method, an echo planar (EPI: Echo Planar Imaging) method and a fast spin echo (FSE: Fast Spin Echo) method For example, higher-speed imaging sequences are known.
[0004]
As one application of these high-speed imaging sequences, a real-time dynamic imaging method called fluoroscopy (fluoroscopic imaging) is being clinically applied. In this fluoroscopy, a dynamic image of a body tissue is generated and displayed as if by X-ray fluoroscopy by repeating imaging and image reconstruction at a cycle of about 1 second or less. Such fluoroscopy has recently been applied to intraoperative imaging, which is collectively referred to as interventional MRI (hereinafter, referred to as “IVMR”) for the purpose of minimum invasiveness (Minimum Invasive). The most promising use of fluoroscopy in IVMR is monitoring when guiding devices and tools such as puncture needles and catheters to the affected area. In such a fluoroscopy, in order to depict the puncture start position and the cross section including the tumor, conventionally, the position of the tumor in the subject is first checked by changing the slice position or angle, and then attached to a puncture needle or the like. A puncture start position is confirmed while monitoring a puncture needle with a display of an optical position detection system of an MRI apparatus having a detected optical position detection pointer and a device position tracking device such as a camera, and then an MR tomogram including a puncture start position and a tumor The image was taken and this operation was repeated until an MR tomogram containing the information necessary for puncturing was obtained. This is necessary for determining the puncture direction even though the position of the puncture needle is monitored by the display of the optical position detection system because the puncture needle does not appear in the MR tomographic image when it is outside the subject. There has been a problem that it takes time to obtain an MR tomographic image and its accuracy is not sufficient.
[0005]
In order to solve such a problem, for example, in US Pat. No. 6,026,315, a phantom in which a light emitter and an MR signal generator are provided at a plurality of predetermined positions in an imaging space of an MRI apparatus is arranged. Then, it is proposed to calibrate in advance the deviation between the coordinate systems of the optical system image and the MR image.
[0006]
[Problems to be solved by the invention]
Therefore, an object of the present invention is to provide an MRI apparatus having a function of continuously drawing an arbitrary imaging section (position and angle) including a marker attached to a puncture needle or a fixture thereof.
[0007]
[Means for Solving the Problems]
The present invention for achieving the above object is an MRI apparatus that repeatedly performs measurement for collecting measurement data of a measurement target region of a subject every predetermined measurement cycle,
By attaching a marker (a substance having a relatively short TI, for example, a contrast medium, fat, etc.) drawn with a high signal on the MR image to a puncture needle or a fixing device as a movable and detachable structure, the puncture needle can be used outside the body. The position can be drawn.
[0008]
In the MRI apparatus configured as described above, for example, after acquiring and reconstructing a multi-echo signal by the EPI method, an arbitrary MR tomographic image including a marker can be continuously acquired in each measurement cycle. Guidance up to puncturing can be performed in a shorter time as compared with measuring the puncturing start position and the tumor position separately and finding a punctuable cross section.
[0009]
The measurement in the present invention may be either two-dimensional measurement or three-dimensional measurement.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
[0011]
FIG. 1 is a block diagram showing the overall configuration of the MRI apparatus according to the present invention. This MRI apparatus includes a static magnetic field generating magnet 2, a gradient magnetic field generating system 3, a transmitting system 5, a receiving system 6, a signal processing system 7, a sequencer 4, and a central processing unit (CPU) 8. I have.
[0012]
The static magnetic field generating magnet 2 generates a uniform static magnetic field around the subject 1 in the body axis direction or in a direction orthogonal to the body axis. The static magnetic field generating magnet 2 uses a permanent magnet type, a normal conduction type, or a superconducting type magnetic field generating means. Become. In the magnetic field space surrounded by the static magnetic field generating magnet 2, a gradient magnetic field coil 9 of the gradient magnetic field generating system 3, a high frequency coil 14a of the transmitting system 5, and a high frequency coil 14b of the receiving system 6, which will be described later, are installed.
[0013]
The gradient magnetic field generating system 3 includes a gradient magnetic field coil 9 wound in three axes of X, Y and Z, and a gradient magnetic field power supply 10 for driving the respective gradient magnetic field coils 9. By driving the gradient magnetic field power supplies 10 of the respective coils in accordance with the following formulas, gradient magnetic fields G _X , G _Y , and G _Z in three axes of X, Y, and Z are applied to the subject 1. The slice plane with respect to the subject 1 can be set by how to apply the gradient magnetic field.
[0014]
The sequencer 4 repeatedly generates a high-frequency magnetic field pulse for causing nuclear magnetic resonance in the nuclei of the atoms constituting the living tissue of the subject 1 in a predetermined pulse sequence. Various commands necessary for data collection of the tomographic image are transmitted to the transmission system 5, the gradient magnetic field generation system 3 and the reception system 6.
[0015]
The transmission system 5 irradiates a high-frequency magnetic field to cause the nuclei of the atoms constituting the living tissue of the subject 1 to cause an NMR phenomenon under the control of the sequencer 4, and includes a high-frequency oscillator 11, a modulator 12, and a high-frequency amplifier 13 And a transmission-side high-frequency coil 14a. The high-frequency pulse output from the high-frequency oscillator 11 is amplitude-modulated by the modulator 12 in accordance with a command of the sequencer 4, and the high-frequency pulse subjected to the amplitude modulation is amplified by the high-frequency amplifier 13, and thereafter, the high-frequency pulse is disposed close to the subject 1. By supplying the electromagnetic wave to the coil 14a, the subject 1 is irradiated with the electromagnetic wave.
[0016]
The receiving system 6 detects an echo signal (NMR signal) emitted by the NMR phenomenon of the nucleus of the living tissue of the subject 1, and includes a high-frequency coil 14 b on the receiving side, which is disposed close to the subject 1, and an amplifier. 15, a quadrature detector 16 and an A / D converter 17. The echo signal detected by the high-frequency coil 14b is input to an A / D converter 17 via an amplifier 15 and a quadrature detector 16 and is converted into a digital quantity, and is further converted into a digital signal at a timing according to a command from the sequencer 4. The sampled data is converted into two series of collected data by the sampling unit 16, and the signal is sent to the signal processing system 7.
[0017]
The signal processing system 7 includes a CPU 8, a recording device such as a magnetic disk 18 and a magnetic tape 19, and a display 20 such as a CRT. The signal from the receiving system 6 is subjected to Fourier transform, correction coefficient calculation, image reconstruction by the CPU 8. The arithmetic processing is performed, and a signal intensity distribution of an arbitrary cross section, a density distribution obtained by performing an appropriate operation on a plurality of signals, and the like are imaged and displayed on the display 20.
[0018]
As the optical position detecting device system 22, for example, POLARIS manufactured by Northern Digital Instrument can be used. The device position tracking device 23 is an infrared camera, and simultaneously detects the position detection optical pointer 21 and the reference pointer attached to a device such as a puncture needle. The position detecting system includes an active type and a passive type. The active type attaches at least three infrared light emitting diodes to a medical device or tool, detects them with two cameras, and displays the six-dimensional movement of the tool in real time. Display speed is a 20~60H _Z. Position accuracy is 0.35mm. In the passive type, a light emitting diode is provided on the camera side, and three reflecting spheres having a diameter of about 10 mm are attached to the tool (position detection optical pointer 21). The camera detects the reflected light of the sphere. The measurement accuracy is the same as that of the active type, and the power supply line is not required for the tool, so that the usability in the IVMR is good. The passive type has 3-4 infrared reflecting spheres attached. The diameter of the reflecting sphere is, for example, 10 mm. The reference pointer is set at a specific fixed position with respect to the center of the static magnetic field. The optical camera is suspended by an arm at a distance of 1 m to 1.5 m from the center of the static magnetic field generation region of the MRI apparatus, and can be freely changed in direction and position.
The operator can move the position detection optical pointer 21 while holding it in his hand. The reference pointer is attached, for example, to the upper surface of the gantry of the MRI apparatus. The position and inclination of the position detection optical pointer 21 with respect to the reference pointer are photographed by a camera, and the personal computer 26 always calculates the position using the image signal. The data update rate is preferably about 2-20 images / s. The position data is sent to the personal computer 26 via, for example, an RS232C cable. In order to prevent noise from being mixed into the MR image, an optical fiber cable 27 is preferably used. The position data is reflected on an imaging section of the MRI fluoroscopy sequence within 0.5 seconds. The imaging sequence is a fluoroscopy sequence such as a gradient echo sequence or a multi-shot EPI. In these sequences, the image can be updated every 0.5s-4s.
[0019]
Next, a method for continuously drawing an arbitrary imaging section (position and angle) including a marker attached to a puncture needle or a fixture thereof by the MRI apparatus will be described. First, a subject is placed in a measurement space in a static magnetic field magnet, and continuous imaging is performed on a target imaging area.
[0020]
In the above continuous imaging, as a method of rapidly delineating a puncture start position and a cross section including a tumor, markers 401 and 402 that emit an MR signal to a puncture needle 400 as shown in FIG. The optical device tracking device 405 and the device detection optical marker 404 are used to grasp the current position, and the position information acquired by the optical device tracking device 405 is transmitted to the MRI apparatus. By performing the feedback, an arbitrary imaging cross section (position and angle) including the puncture needle or the marker attached to the fixing tool can be continuously drawn. Thus, even when the puncture needle is outside the body, it is easy to search for the tumor 403 while confirming the puncture needle position on the screen (image). The markers 401 and 402 that emit MR signals can be freely moved and removed, and when puncturing is started, they can be removed according to the situation.
[0021]
As a second embodiment of the present invention, an example in which a substance that emits an MR signal is incorporated in a sheath as shown in FIG. The puncture needle 500 is passed through a sheath 501 manufactured using a substance that emits an MR signal. Further, the current position is grasped by using the optical device tracking device 504 and the device optical marker 503, and the position information obtained by the optical device tracking device 504 is fed back to the MRI device, so that the device can be attached to the puncture needle or its fixing device. It is possible to continuously depict any imaging cross section (position and angle) including the marker. This makes it easy to search for the tumor 502 while confirming the puncture needle position on the screen (image). Compared with the first embodiment, there is no need to remove the marker 501 that emits the MR signal, and there is an advantage that the presence position can be confirmed from the contrast difference even in the body.
[0022]
In addition, the marker and the sheath that emit the MR signal are made of a relatively short substance of T1 and T2 (for example, contrast agent, fat, silicon) or a relatively long substance of T1 and T2 (for example, water). Since the image contrast varies depending on the region, the imaging sequence, and the like, it is possible to use the image contrast properly depending on the conditions.
[0023]
In addition, in the above description, the case where two-dimensional measurement data is used as the basic measurement data has been described. However, it is possible to obtain any kind of data even with three-dimensional measurement data, and obtain the same effect. Can be.
[0024]
【The invention's effect】
By attaching the marker that emits the MR signal described above to the puncture needle or its fixture and using the optical device following device attached to the puncture needle, the cross section (position and angle) including the marker and the puncture needle can be MR outside the body. It can be confirmed on the image.
[Brief description of the drawings]
FIG. 1 is a block diagram showing an overall configuration of an MRI apparatus to which the present invention is applied.
FIG. 2 is a view for explaining the relationship between an extracorporeal puncture needle and a tumor according to the first embodiment of the present invention.
FIG. 3 is a view for explaining the relationship between an extracorporeal puncture needle and a tumor according to a second embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Subject 2 ... Static magnetic field generating magnet 3 ... Gradient magnetic field generating system 4 ... Sequencer 5 ... Transmission system 6 ... Receiving system 7 ... Signal processing system 8 ... CPU
9 Gradient magnetic field coil 10 Gradient magnetic field power supply 14a High frequency coil 14b on the transmitting side High frequency coil 16 on the receiving side Quadrature detector 17 A / D converter 18 ··· Magnetic disk 19 ··· Magnetic tape 20 ··· Display 21 ··· Device position detecting optical pointer 22 ··· Optical position detecting device system 23 ··· Optical device position tracking device 24 ··· Modem 25 · ..Modem 26 Personal computer (PC)
27 optical fiber cables 400, 500 puncture needles 401, 402, 501 MR signal emission markers 403, 502 tumors 404, 503 device optical markers 405, 504 optical camera

Claims (4)

A static magnetic field generating means for applying a static magnetic field to the subject; a gradient magnetic field generating means for applying a gradient magnetic field to the subject; and a high-frequency pulse for causing nuclear magnetic resonance in nuclei of atoms constituting the living tissue of the subject. A sequencer that is repeatedly generated in a predetermined pulse sequence, a transmission system that irradiates a high-frequency magnetic field to cause nuclear magnetic resonance in an atomic nucleus of a living tissue of a subject by a high-frequency pulse from the sequencer, and emits by the above-described nuclear magnetic resonance A magnetic resonance imaging apparatus comprising: a reception system that detects an echo signal to be obtained; a signal processing system that performs image reconstruction operation using the obtained echo signal; and a unit that displays an obtained image. A plurality of markers that emit the puncture are attached to the puncture needle or its fixture, and the surface including the attached marker is drawn on the magnetic resonance image. In, also recognizes the puncture needle position and direction in the outer subject, the magnetic resonance imaging apparatus characterized by having a function that allows visualization of a section including a puncture needle on the magnetic resonance image. The magnetic resonance imaging apparatus according to claim 1, wherein the marker is configured to be movable and detachable with respect to the puncture needle or a fixture thereof. 2. The magnetic resonance imaging apparatus according to claim 1, wherein the marker comprises a sheath for guiding the puncture needle or a puncture needle fixture itself made of a substance that emits a magnetic resonance signal. 2. The magnetic resonance imaging apparatus according to claim 1, wherein the position of the puncture needle to which the marker is attached or the fixture thereof is tracked by an optical position detection system.

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