JP2001161660A - Magnetic resonance imaging system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To display the position of an appliance at the time of displaying of the image in real time without a delay and in full size without letting the image of the appliance disappear from a display for an interventional magnetic resonance imaging(IMR) for doing an operation by using the appliance such as a paracentesis needle inserted in a subject. SOLUTION: A means for finding the position is provided on two points of the appliance to be inserted in the subject. A means for determining the subject's cross section specified by the object of IMR and the direction of the appliance is provided. A means for switching a displayed cross section following the direction that the appliance is heading for is provided. The cross section including the inserted appliance is continuously displayed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic resonance imaging (hereinafter, referred to as "MRI") apparatus for obtaining a tomographic image of a subject using a nuclear magnetic resonance phenomenon, and more particularly, to a real-time based on an image obtained by MRI. The so-called interventional MR (hereinafter referred to as “IM
R ”).

[0002]

2. Description of the Related Art In MRI, a gradient magnetic field and an RF pulse are applied to a subject in a static magnetic field to select and excite a cross section of a specific portion, and the position information of the cross section in one axial direction is converted to the RF pulse. The phase and other axial position information are encoded into the frequency of the RF pulse, and the obtained NMR signal, which is an echo signal of magnetic resonance from the nucleus of the living tissue at a specific site, is decoded by Fourier transform and the above is decoded. By performing reconstruction using the position information, imaging is performed to obtain a tomographic image representing a cross section of the site.

[0003] On the basis of the image thus obtained, a device such as a puncture needle, a biopsy needle, or a laparoscope to be inserted into a subject (hereinafter, collectively referred to as a "puncture needle or the like" in the present specification) is inserted. The IMR performing the treatment checks the target site of the target to be treated based on the following procedure, a multi-slice image photographed in advance, and determines the position and angle for inserting a puncture needle or the like according to the position of the target site and surrounding conditions. The position of the cross section to be imaged by MRI is set so as to include the position where the puncture needle is inserted and the target site, and the IMR is started by inserting the puncture needle while continuously photographing the cross section. Immediately before arriving at the target site, the imaging section is changed to a puncture needle or the like whose position in the depth direction can be determined and photographed. After confirming that there is no displacement of the puncture needle or the like, the puncture needle or the like is moved to the target site. And take necessary measures. It is done in.

In the IMR, it is necessary to display an image of a puncture needle or the like on a display together with a cross-sectional image of a subject. However, a puncture needle or the like made of a non-magnetic material does not react to magnetism and is not displayed on the display at all. Therefore, a receiving coil is attached to a nonmagnetic puncture needle or the like as disclosed in, for example, Japanese Patent Application Laid-Open No. 6-22938 to recognize the position of the puncture needle or the like in the subject, and to display the position on the image of the subject. The display has been performed using a graphic symbol or the like. Similarly, a puncture needle or the like is formed of a magnetic material, emits magnetism from itself, is detected by an MRI apparatus, and a puncture needle or the like in the subject is displayed together with an image of the subject.

[0005]

However, in the IMR using the conventionally known MRI apparatus, there is no relation between the progress of the puncture needle and the displayed cross section. It is necessary to stop the progress of the puncture needle or the like immediately before reaching the target site, change the display to a cross section where the position in the depth direction can be confirmed, and confirm the current position of the puncture needle or the like. Confirmation image settings,
Procedures such as confirmation image shooting and current position confirmation are required.
The time required for R is lengthened. If the puncture needle deviates from the initially set cross-section, the puncture needle or the like is not displayed on the display until the cross-section that seems to include the puncture needle is estimated and found, and it is newly displayed. There was a problem that it was not possible to grasp the correctness. This is different from the conventional MRI in which the operator of the IMR and the input person who designates the imaging section are different, and the designation of the imaging section desired by the operator at each time is not transmitted in real time, so that it is not reflected on the display image. Further, even if the designation of a specific image section is transmitted, it is difficult to quickly display the section.

In the case of a puncture needle or the like made of a magnetic material, the magnetic force of the puncture needle or the like disturbs the magnetic force of the puncture needle or the like and causes the NMR from the tissue of the subject to be surrounded.
The signal is lost, and the puncture needle or the like is displayed on the display as if it were larger and thicker than it actually is. For this reason, for example, JP-A-11-2
As disclosed in US Pat. No. 25994, a locus of the center of gravity of an image of a puncture needle or the like obtained by calculation on a large and thick image obtained by a puncture needle or the like formed of a magnetic material It has been performed to superimpose and display color-coded graph symbols and the like.

[0007] However, regardless of whether the puncture needle or the like inserted into the subject to be used as required for the treatment is made of a non-magnetic material or a magnetic material, the puncture needle or the like is displayed. There is no MRI system in which the used puncture needle etc. is displayed on the display together with the tomographic image of the subject in the shape and size of the actual device and the size occupied by the device actually inserted inside the subject There is no objective indication to the operator.

The position of the puncture needle or the like displayed in the photographed image is the position where the puncture needle or the like is detected when the image is photographed, and a certain cross section is photographed and completely displayed. It takes time in seconds, so that the display of the tomographic image is completed unless the puncture needle or the like is stopped. There was also the problem of time delays, which did not exist.

SUMMARY OF THE INVENTION An object of the present invention is to improve the above-mentioned disadvantages, and to always display a puncture needle or the like on a display, thereby omitting the procedure for confirming the current position of the puncture needle or the like and shortening the treatment time. It is in. Another object of the present invention is to display an instrument such as a puncture needle to be inserted into a subject in a predetermined shape and a predetermined size on an MRI image.

Still another object of the present invention is to estimate a real-time arrival position of a puncture needle or the like at the time of completion of display and to display the estimated position on a display without delay (hereinafter, referred to as "real-time display" in this specification). It is in.

[0011]

In order to solve the above-mentioned problems, an MRI apparatus according to the present invention causes a static magnetic field generating means, a gradient magnetic field generating means, and magnetic resonance to be generated in nuclei constituting a tissue of a subject. A transmitting system that generates a high-frequency pulse, a receiving system that detects an NMR signal from a subject by magnetic resonance, a signal processing system that reconstructs and displays an image using the signal detected by the receiving system, and a puncture needle. In an imaging apparatus having means for detecting the position and direction of an instrument for performing a treatment by inserting it into a subject, the gradient magnetic field generating means based on insertion information of the instrument determined in advance, various parameters of a transmission system Is provided.

With this configuration, the MRI apparatus according to the present invention can change the imaging parameters based on the displacement of the puncture needle or the like, so that the displayed cross-section is switched following the progress of the puncture needle or the like and the puncture needle or the like is displayed on the display. This is always displayed, thereby omitting the procedure for confirming the current position of the puncture needle or the like, thereby shortening the treatment time.

[0013] Further, means for displaying an instrument to be inserted into the subject with a predetermined cursor (hereinafter referred to as "cursor display means"), and disposing the cursor at a position detected by the instrument position / direction detecting means. Means (hereinafter referred to as "cursor arranging means"). With such a configuration, in the MRI apparatus, regardless of whether the material of the instrument such as the puncture needle used for the IMR is magnetic or non-magnetic, a cursor that defines a puncture needle or the like to be used according to a necessary treatment is predetermined. Therefore, an instrument such as a puncture needle inserted into the subject is displayed on the MRI image in a predetermined shape and a predetermined size.

[0014] In the magnetic resonance imaging apparatus, the signal processing system may display one or both of insertion information of a predetermined instrument and information based on a difference between the insertion information and actual insertion information on the same screen as the image. It is a magnetic resonance imaging apparatus displayed above. With this configuration, the displacement of the puncture needle or the like can be visually recognized, so that it is possible to easily determine whether or not to perform puncture again.

Further, the amount of movement is calculated from the position detected by the position / direction detecting means of the device and an arbitrary position of the device already detected, and the time required to complete the display is calculated based on the time required for the movement. Means for calculating and estimating the arrival position of the appliance at the time of display (hereinafter, referred to as "arrival position estimating means") is provided. With such a configuration, the position at which the puncture needle or the like is displayed on the display is not the position at the time when the image is actually captured, but is based on the speed of the puncture needle or the like at the time when the displayed image information is obtained. Is calculated and the arrival position of the instrument at the time of display is estimated, so that the real-time arrival position of the puncture needle or the like at the time of display completion is estimated and displayed on the display without delay.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an MRI apparatus according to the present invention will be described below in detail with reference to the drawings. FIG. 1 is a block diagram schematically showing the overall configuration of an MRI apparatus to which the present invention is applied, FIG. 2 is a flowchart for explaining the operation of the MRI apparatus of the present invention, and FIGS.
It is a tomographic image of the subject displayed on the display during the treatment of R. FIG. 1 is a block diagram showing a schematic overall configuration of an MRI apparatus to which the present invention is applied. This MRI apparatus is for obtaining a tomographic image of a subject using a magnetic resonance phenomenon, and includes a static magnetic field generating means 1, a gradient magnetic field generating means 2, a transmission system 3, a reception system 4, a signal processing system 5, a sequencer 6, a central processing unit 7 and an operation unit (not shown).

The static magnetic field generating means 1 is composed of any one of a permanent magnet, a normal conducting magnet, and a superconducting magnet arranged in a certain space around the subject 8. A uniform static magnetic field is generated in a direction or a direction perpendicular to the body axis of the subject. The gradient magnetic field generating means 2
A gradient magnetic field coil 9 wound in three directions of X, Y, and Z, and a gradient magnetic field power supply 10 for magnetizing each of these coils. Each coil of the gradient magnetic field power supply 10 is magnetized according to a command from the sequencer 6. X, Y, Z
The gradient magnetic fields Gs, Gp, Gf in the three axial directions are applied to the subject 8. Depending on how the gradient magnetic field is applied, a cross section of the subject 8 to be imaged and displayed is set.

The transmission system 3 includes a high-frequency oscillator 11, a modulator 1
2. A high-frequency oscillator comprising a high-frequency amplifier 13 and a high-frequency irradiation coil 14 for causing nuclear magnetic resonance in the nuclei of the atoms constituting the living tissue on the imaging section of the subject 8 set by the gradient magnetic field generating means 2 After a high-frequency pulse output from 11 is amplified by a high-frequency amplifier 13, the high-frequency pulse is supplied to a high-frequency irradiation coil 14 installed close to the subject 8 to irradiate the subject.

The receiving system 4 includes a high-frequency receiving coil 15, a receiving circuit 16, and an analog / digital (hereinafter, "A / D").
NM which is an echo signal by nuclear magnetic resonance of the nucleus of the living tissue of the subject 8 due to the electromagnetic wave irradiated from the high frequency irradiation coil 14 of the transmission system 3
The R signal is detected by the high-frequency receiving coil 15 arranged close to the subject 8, input to the A / D converter 17 via the receiving circuit 16, converted into a digital signal, and further converted from the sequencer 6. The signal is sent to the signal processing system 5 as collected data sampled at the timing according to the command.

The signal processing system 5 includes a CPU 7 for performing processing such as Fourier transform / correction coefficient calculation on the collected data and controlling the sequencer 6, and a signal processing device for performing processing necessary for reconstructing the collected data into a tomographic image. 18. A program for a sequence of image analysis processing over time and a designated measurement, a parameter used for the execution thereof, and the like are stored, and a measurement parameter and a receiving system 4 obtained by a previous measurement performed on the subject are stored. A memory 19 for temporarily storing collected data from the NMR signal detected in step 1 and an image used for setting a region of interest, and for storing parameters for setting the region of interest, and a data storage for storing image data reconstructed by the CPU 7. The magnetic disk 20 and the optical disk 21 serving as a unit and image data read from these disks are visualized and cut off. Display 2 to be displayed as an image
2, the image reconstruction is performed using the NMR signal detected by the receiving system 4 and the image is displayed.

The sequencer 6 operates under the control of the CPU 7 and repeatedly applies a high-frequency magnetic field pulse for causing nuclear magnetic resonance to the nuclei of the atoms constituting the living tissue of the subject 8 in a predetermined pulse sequence. Various commands necessary for data collection of a tomographic image of the subject 8 are sent to the gradient magnetic field generation means 2, the transmission system 3 and the reception system 4. The operation unit includes a trackball, a mouse, a keyboard, and the like, and inputs control information of processing performed by the signal processing system 5.

As will be described in detail below, the MR of this embodiment
In the I device, the device position / direction detecting means is provided on a device such as a puncture needle, the cursor display means is provided in the memory 19, and the follow-up display means / cursor arranging means / arrival position estimating means are provided in cooperation with the memory 19 and the CPU 7. ,It is configured.

The operation of the MRI apparatus proceeds according to the flow shown in FIG. 2 and produces the display shown in FIGS. 3 to 7. Therefore, in the following, each step is performed based on the flow shown in FIG. The operation will be described and reference will be made to other drawings whenever necessary. FIG. 2 is a flowchart showing an example of the IMR in the MRI apparatus of the present invention, and FIGS. 3 to 7 are examples of the display on that occasion.

Here, the devices generally referred to as puncture needles and the like to be inserted into the subject are devices generally used for IMR such as puncture needles, biopsy needles, laparoscopic devices, endoscopes, catheters, and guide wires. In this embodiment, the instruments represent, in this embodiment, their actual shapes specified in advance by type, such as a puncture needle type, a biopsy needle type, a laparoscopic type, an endoscope type, a catheter type,
It is stored in a cursor display means as a cursor of a guide wire type or the like. They are selected in advance according to the device to be actually used as necessary for the IMR treatment, and the position of the device inside the subject is set at the position specified by the position / direction detecting means of the device provided on the puncture needle or the like. The position of the tip and the direction are aligned by the cursor positioning means so as to be substantially the same size as the subject and at the same position and direction as the subject, and are superimposed by the CPU 7 on the image of the subject actually photographed. And displayed on the display 22 in the manner described below.

The puncture needle or the like in the case of FIG. 3 is made of a non-magnetic material, and the portion for performing treatment by being inserted into the subject is the same as the conventional one. This puncture needle or the like is provided with a device position / direction detecting means including pickup coils arranged at two places separated by a distance that is not inserted into the subject.
The two pickup coils detect the surrounding magnetic field and recognize as a signal indicating their own position in the space.
The transfer to PU 7 allows CPU 7 to detect the position and orientation of the appliance. Since the two pickup coils are arranged at positions of a predetermined length from the tip of the puncture needle or the like, their directions and positions with respect to the surrounding magnetic field obtained by this position / direction detection means, and the puncture needles calculated therefrom Similarly, the position of the tip is always grasped similarly as the relative direction and relative position with respect to the subject existing in the magnetic field.

When the MRI apparatus is activated and the IMR is started, in step 101 shown in FIG. 2, the IMR is performed using a positioning image taken in advance to insert the puncture needle or the like into the subject. The position of the target site requiring treatment and its surroundings are grasped, a region of interest is set for the target site on the positioning image, and the insertion position and insertion direction of the puncture needle and the like are determined. Then, the imaging section is determined so as to include the target site and the puncture needle.

When the photographing section is determined, step 103
To 105 are executed. In step 103, parameters for imaging this section (hereinafter referred to as "section parameters") are selected. Next, in step 105, an RF pulse and a gradient magnetic field that excite the atomic nuclei of the living tissue of the imaging section determined by the sequencer 6 in the subject. Is applied to start imaging, and a puncture needle or the like is inserted from the determined insertion position in the determined insertion direction. At this time, the cursor in the shape of the instrument actually used in the IMR displayed by the cursor display means is arranged by the cursor arrangement means at the latest position of the puncture needle or the like detected by the instrument position / direction detection means, And display it.

In steps 107 and 109, the position and direction of the puncture needle and the like are detected by the position / direction detecting means of the instrument, and the position and direction of the puncture needle and the like are always checked to see if they are on the initially designated cross section. When a puncture needle or the like is inserted out of the determined predetermined cross section or deviates from the predetermined cross section while the inside of the subject is in progress, it is recognized and step 21 is performed.
1 notifies the image on the display. At this time, notification by voice is also possible. At this time, as shown in FIG. 3, since the initially determined directions are simultaneously combined and displayed on a display in a straight line, the degree of deviation of the puncture needle or the like from the initially determined direction can be easily known.

When the deviation is notified, the follow-up display means selects the direction of the puncture needle detected by the instrument position / direction detecting means and the cross-sectional parameters of the cross-section including the target part in steps 213 to 217, and performs the puncture. The RF pulse is switched so that the cross section including the needle is imaged following the progress of the needle or the like. Therefore, the puncture needle or the like is not lost and disappears from the display 22. Unless otherwise changed, the display 22 selects and switches the cross-sectional parameter of the cross-section including the current puncture needle or the like by the follow-up display means. Therefore, the operator can easily grasp the progress of the puncture needle or the like and determine whether to repeat the insertion or change the insertion angle to continue the treatment.

The memory 19 accumulates and stores the position of the puncture needle and the like at each photographing time of the image detected by the position / direction detecting means of the instrument in steps 107 and 109 and the time. In step 201, one of the previously detected arbitrary positions of the puncture needle or the like stored in the memory 19 is selected, and a moving distance which is a difference from the position at each time and a time required for the movement are obtained. The speed of the puncture needle or the like is calculated and stored in the memory 19. In this embodiment, the latest position of the puncture needle and the like detected by the position / direction detecting means of the device and the time required for completing one shot and updating the image (hereinafter referred to as “one display required time”) The latest speed of the puncture needle or the like is obtained by comparing the position of the previous puncture needle or the like with the position of the previous puncture needle or the like, dividing by the required display time and storing it in the memory 19. Here, 1.0 mm is calculated as the movement amount, and is calculated as 1.0 second, which is the time required for one display. As a result, 1.0 mm per second is obtained.

Next, an inquiry is made as to whether the display of the puncture needle or the like on the display 22 should be a real-time display mode with no time difference. In this embodiment, a real-time display mode is selected and input to an operation unit (not shown). Step 301
The arrival position estimating means is based on the one display required time, and the position at the time of image capture of the puncture needle or the like is multiplied by the speed and the one display required time, that is, 1.0 mm in this case. CPU 7 calculates the estimated position of the display
Transfer to The cursor arranging means is arranged on the extension in the same direction so that the position of the tip of the cursor such as the puncture needle output from the cursor display means coincides with the position calculated by the arrival position estimating means, and transferred to the CPU 7. 22
To be displayed.

In this case, as long as the operator does not input the cancellation of the real-time display mode on the keyboard or the like, the arrival position estimating means determines the length that the puncture needle or the like advances within one display required time which is a display switching period for each display. Calculated from the latest speed, the cursor is positioned so that the point of display of the cross section and the position of the puncture needle etc. match in real time, so that unless the operator changes the insertion speed of the puncture needle or the like extremely, the cursor is selected. The position of the puncture needle or the like at the time of displaying the cut section is displayed without delay. The above procedure is repeated until the completion of the IMR, and the procedure ends. If the real-time display mode is not selected, the display becomes the conventional display in which the cursor such as the puncture needle output from the cursor display means is arranged by the cursor arrangement means at the detection position of the instrument position / direction detection means in step 311. It is not described in detail in this specification.

FIGS. 4 and 5 are explanatory views showing another embodiment of the present invention. In this case, the puncture needle or the like is formed of a magnetic material. The NMR signal from the subject tissue around the puncture needle or the like becomes deficient due to the interference of the magnetic material, and the puncture needle or the like is displayed larger and thicker than the real thing in the display image of FIG. For this reason, the IMR is shown on the missing image shown in black in FIG.
A cursor which is approximately the same size as the actual shape of the instrument to be used for the treatment selected before the start is displayed by the cursor display means, and the cursor arrangement means is provided in the same size as the cross-section of the subject at a substantially full size. And are displayed in white. The signal-deficient portion of the magnetic substance detected by the MRI apparatus due to interference with the puncture needle or the like may be displayed as it is in black as described above, or the portion may be blank and the cursor such as the puncture needle may be displayed in black. Alternatively, a part of an image photographed before the required number of display times and having no puncture needle or the like, that is, an image having no signal loss may be used. In the case of the substitute, if the imaging section is switched due to a deviation of the puncture needle or the like, the display cannot be performed.
It is desirable that this alternative selection of images can be changed at will during the implementation of the IMR. Others are the same as the IMR of FIG.

FIG. 6 is an explanatory diagram showing another embodiment of the present invention. In this example, both the insertion direction of the puncture needle and the like determined at the beginning and the current progress moved by the progress of the puncture needle and the like are displayed in a straight line, and the deviation between them is simultaneously displayed by a number on the display. The degree of deviation from the planned orbit can be easily grasped. In FIG. 6, when a deviation occurs in the IMR of FIG. 3, the amount of deviation from the original insertion direction is quantified from the current position and direction detected by the position / direction detection means of the instrument. The values are obtained and displayed on the display 22.

FIG. 7 shows that the direction detected by the device position / direction detecting means is extended and displayed because a deviation occurs in the IMR of FIG. 3, and if the procedure is continued as it is, the puncture needle or the like reaches the target site. An example will be described in which the CPU 7 issues a warning on the display 22 when it is determined that it cannot be performed.

In the above-described embodiment, as the position / direction detecting means of the device for detecting the position and direction of the puncture needle, an example of a pickup coil provided at two places, such as a puncture needle, which is not inserted into the subject is used. Although described with reference to the above, known means for causing the MRI apparatus to recognize the position and direction of the puncture needle or the like can be optionally employed.

In this embodiment, the cursor display means is described as a memory of hardware, but the function can be similarly achieved by software by a known method. Similarly, the first and fifth means are constituted by a memory and an arithmetic unit. However, the first and fifth means may be constituted by software including an arithmetic expression, stored in the memory 19 and operated by the CPU 7.

[0038]

As described above, according to the MRI apparatus of the first aspect, since the direction of the puncture needle and the target region are always determined, the cross-section to be imaged is obtained from the cross-section of the puncture needle and the like. The target section of the IMR and the device inserted into the subject, such as the puncture needle, do not disappear, and the section to be displayed is switched by following the progress of the puncture needle so that the puncture needle and the like are always displayed. An MRI apparatus is provided which can always grasp the presence or absence of a deviation, thereby omitting the procedure for confirming the current position and shortening the treatment time. M according to claim 2
According to the RI apparatus, there is provided an MRI apparatus that displays an instrument such as a puncture needle inserted into a subject in a predetermined shape and a predetermined size on an MRI image. Further, according to the MRI apparatus of the third aspect, there is provided an MRI apparatus which estimates a real-time arrival position of a puncture needle or the like at the time of display completion and displays the estimated position on a display without time delay.

[Brief description of the drawings]

FIG. 1 is a block diagram of an MRI apparatus.

FIG. 2 is an operation flowchart of the MRI apparatus.

FIG. 3 is a display example of an IMR display by the MRI apparatus.

FIG. 4 is another display example of the IMR by the MRI apparatus.

FIG. 5 is another display example of the IMR by the MRI apparatus.

FIG. 6 is another display example of the IMR by the MRI apparatus.

FIG. 7 is another display example of the IMR by the MRI apparatus.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 static magnetic field generation magnetic circuit 2 gradient magnetic field generation system 3 transmission system 4 reception system 5 signal processing system 6 sequencer 7 CPU 8 subject 9 gradient magnetic field coil 10 gradient magnetic field power supply 11 high frequency oscillator 12 modulator 13 high frequency amplifier 14 high frequency irradiation coil 15 High frequency receiving coil 16 Receiving circuit 17 A / D converter 18 Signal processing device 19 Memory 20 Magnetic disk 21 Magneto-optical disk 22 Display

Claims (3)

[Claims] 1. A static magnetic field generating means, a gradient magnetic field generating means, a transmission system for generating a high-frequency pulse for generating magnetic resonance in nuclei constituting a tissue of a subject, and an NMR signal from the subject by magnetic resonance. A receiving system for detection, a signal processing system for reconstructing and displaying an image using signals detected by the receiving system, and detecting a position and a direction of an instrument such as a puncture needle for performing treatment by being inserted into a subject. A magnetic resonance imaging apparatus comprising: a gradient magnetic field generating unit; and a unit that changes various parameters of a transmission system based on predetermined insertion information of the instrument. 2. The apparatus according to claim 1, further comprising means for displaying an instrument to be inserted into the subject with a predetermined cursor, and means for arranging the cursor at a position detected by means for detecting the position and direction of the instrument. 7. The magnetic resonance imaging apparatus according to item 1. 3. The magnetic resonance imaging apparatus, wherein the signal processing system displays one or both of predetermined information on insertion of the instrument and information based on a difference between the insertion information and actual insertion information on the same screen as the image. Magnetic resonance imaging device displayed above.