JPH09122096A - Method of detecting tip of instrument to be inserted into subject in mri apparatus and mri apparatus used in carrying out the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to detect the position of the tip of an instrument in a method of detecting the tip of an instrument to be inserted into a subject in an MRI apparatus without forming an image of the tip of the biopsy instrument inserted into the diagnostic position from outside the subject. SOLUTION: With respect to the concerned area including a biopsy instrument inserted into the diagnostic position from outside the subject, irradiation with high-frequency signals and application of a gradient magnetic field are simultaneously carried out to excite selectively the concerned area, a gradient magnetic field is applied along the direction of the movement of the tip of the biopsy instrument to produce echoes, the received echoes are converted to projected signals by Fourier transformation, the phase distribution of the projected signals is found, and the position and the speed of the tip are determined from the positions of the changes of the phase and the size of the phase caused by the movement of the tip of the biopsy instrument with the gradient magnetic field being applied. Thus, the position of the tip of the biopsy instrument can be detected without forming an image of the tip of the biopsy instrument.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to nuclear magnetic resonance (hereinafter abbreviated as "NMR") generated in a living tissue of a subject.
A method for detecting the tip of a subject insertion instrument for detecting the position of the tip of a biopsy instrument inserted into the diagnosis site from the outside of the subject in an MRI apparatus that obtains a tomographic image of the diagnosis site by utilizing a phenomenon The present invention relates to a method for detecting the tip of an instrument to be inserted into a subject, which can detect the position of the tip of the instrument without imaging the tip, and an MRI apparatus used for implementing the method.

[0002]

2. Description of the Related Art Recently, in an MRI apparatus, not only a tomographic image of a diagnosis site of a subject is simply measured to perform image diagnosis, but also a biopsy instrument such as a biopsy needle or a catheter is directly inserted into the diagnosis site. Interventional treatment for various treatments
A treatment method called radiology (generally abbreviated as "IVR") has been performed. I like this
In the VR procedure, it is necessary to find a target affected area in the measured MRI image and quickly insert a biopsy device such as a catheter into the target affected area. For this purpose, the position of the tip of the biopsy device is determined. It is necessary to detect and guide it to the affected area. In this regard, a conventional method for detecting the tip of a subject insertion instrument in an MRI apparatus is considered to image the biopsy instrument inserted into the subject and detect the position of the tip on the image. However, with this method, imaging of the biopsy instrument is not so fast, and practical application is difficult. In contrast, “MAGNET
IC RESONANCE IN MEDICINE 10 ”(1989), pages 227-240,“ Snapshot Imaging at 0.5T Using Echo-Pl ”
As described in “anar Techniques”, an EPI method capable of measuring one image in 100 ms or less has been proposed. According to such a high-speed measurement by the EPI method, the biopsy instrument It is considered possible to perform real-time monitoring to guide the tip to the affected area.

[0003]

However, the above-mentioned EPI
In order to realize high-speed measurement of one image in 100 ms or less by the method, special hardware is required to achieve high gradient magnetic field strength and fast magnetic field rise time, etc. However, the cost was high. Further, if the measurement time is significantly shortened as described above, the resolution and S / N of the obtained tomographic image of the diagnosis site may be sacrificed, and the image quality deteriorates.

Therefore, the present invention can address such problems and detect the position of the tip of a biopsy instrument inserted into the diagnostic site from outside the subject without imaging the tip. An object of the present invention is to provide a method for detecting the tip of a device for inserting a subject and an MRI apparatus used for carrying out the method.

[0005]

In order to achieve the above object, a method for detecting the tip of a subject insertion instrument in an MRI apparatus according to the present invention comprises a static magnetic field generating means for applying a static magnetic field to the subject, and a tilt to the subject. Gradient magnetic field generating means for applying a magnetic field,
A gradient magnetic field power source for driving the gradient magnetic field generating means, a probe for irradiating a high-frequency signal to the diagnostic region of the subject and receiving a high-frequency signal emitted by nuclear magnetic resonance of the biological tissue of the subject, An image is generated using the high-frequency signal received by the probe while controlling the gradient magnetic field power supply and the high-frequency transmission / reception unit according to the pulse sequence at the time of imaging, by driving the probe to irradiate and receive the high-frequency signal. An MRI apparatus comprising a computer for performing reconstruction calculation and a display for inputting an image signal generated by the computer and displaying the image as a tomographic image. Irradiation of a high-frequency signal and application of a gradient magnetic field are simultaneously performed on a region of interest including the instrument to selectively excite the region of interest, and the tip of the biopsy instrument is A gradient magnetic field is applied along the moving direction to generate an echo, the received echo is converted into a projection signal by Fourier transform, the phase distribution of this projection signal is obtained, and the tip of the biopsy instrument is being applied with the gradient magnetic field. The position and speed of the tip portion are obtained from the position and the magnitude of the phase change caused by the movement of the.

[0006] Further, irradiation of a high frequency signal and application of a gradient magnetic field are simultaneously performed on a region of interest including a biopsy device inserted into the diagnosis region from the outside of the subject to selectively excite the region of interest, thereby activating the biopsy device. A gradient magnetic field is applied along the moving direction of the tip to generate the first echo, and then the region of interest is selectively excited again, and the same direction as that applied to generate the first echo is tilted. A magnetic field is applied to generate a second echo, each received echo is transformed into a projection signal by Fourier transform, the phase distribution of this projection signal is determined, and the phase distribution obtained from the first echo and the The background noise is removed by taking the difference with the phase distribution obtained from the two echoes, and the phase change caused by the movement of the tip of the biopsy instrument during the application of the gradient magnetic field is emphasized. From the position and magnitude of the phase of the may be obtained the position and speed of the tip portion.

Further, irradiation of a high-frequency signal and application of a gradient magnetic field are simultaneously performed on a region of interest including a biopsy instrument inserted from the outside of the subject into a diagnostic site to selectively excite the region of interest, thereby activating the biopsy instrument. A gradient magnetic field was applied along one direction of a plane including the moving tip to generate a first echo, and then the region of interest was selectively excited again and applied to generate the first echo. A second echo is generated by applying a gradient magnetic field along another direction of the moving surface of the tip of the biopsy instrument, which is orthogonal to the above, and converts each received echo into a projection signal by Fourier transform, Even if the phase distribution of the projection signal is obtained, the position and velocity of the tip portion are two-dimensionally obtained from the phase distribution obtained from the first echo and the phase distribution obtained from the second echo. Good.

Furthermore, irradiation of a high-frequency signal and application of a gradient magnetic field are simultaneously performed on a region of interest including a biopsy device inserted into the diagnosis region from the outside of the subject to selectively excite the region of interest, and the biopsy device is then excited. A first magnetic field is generated by applying a gradient magnetic field along one direction of the volume including the moving tip of the first region, and then the region of interest is selectively excited again and applied to generate the first echo. And a gradient magnetic field is applied along the other direction of the moving volume of the tip of the biopsy instrument to generate a second echo, and then the region of interest is selectively excited again, And applied to generate the second echo, a gradient magnetic field is applied along yet another direction of the moving volume of the tip of the biopsy instrument, which is orthogonal to both, to generate the third echo, and then receive Each of the Is transformed into a projection signal by Fourier transform, the phase distribution of this projection signal is obtained, and the first phase distribution obtained from the first echo and the first phase distribution obtained from the second echo are orthogonal to the above first phase distribution. The second phase distribution in the direction, and the third phase distribution in the direction orthogonal to any of the first and second phase distributions obtained from the third echo, the position and velocity of the tip portion in a three-dimensional manner. May be requested.

In any of the above means, the biopsy instrument is made of a non-magnetic substance, and the tip of the biopsy instrument contains a substance that causes nuclear magnetic resonance by irradiation of a high frequency signal in a magnetic field space. There is.

Further, an MRI apparatus as a related invention of the method for detecting the tip of a subject inserting instrument is a static magnetic field generating means for applying a static magnetic field to the subject, and a gradient magnetic field generating means for applying a gradient magnetic field to the subject. A gradient magnetic field power source for driving the gradient magnetic field generating means, a probe for irradiating the diagnostic region of the subject with a high-frequency signal and a high-frequency signal emitted by nuclear magnetic resonance of biological tissue of the subject, A high-frequency transmitting / receiving unit that drives a probe to irradiate and receive the high-frequency signal, controls the gradient magnetic field power supply and the high-frequency transmitting / receiving unit according to a pulse sequence at the time of imaging, and re-images using the high-frequency signal received by the probe. An MRI apparatus including a computer that performs a configuration calculation and a display that inputs an image signal generated by the computer and displays it as a tomographic image The display device displays a tomographic image measured in advance on a region of interest including a biopsy instrument inserted into the diagnosis site from outside the subject, and the subject according to any one of claims 1 to 5 is displayed. The information on the position of the tip of the biopsy instrument, which is obtained by the method for detecting the tip of the sample insertion instrument, is displayed by being superimposed on the tomographic image.

Furthermore, another MR which is also a related invention
In the MRI apparatus similar to the above-mentioned means, the apparatus I is a computer that performs control of the gradient magnetic field power source and the high frequency transmission / reception unit according to a pulse sequence at the time of imaging and performs image reconstruction calculation using the high frequency signal received by the probe. A biopsy instrument insertion guide mechanism for guiding a biopsy instrument to be inserted into the diagnosis site from the outside of the subject is connected, and the biopsy instrument insertion guide mechanism is connected to the biopsy instrument insertion guide mechanism to detect the tip of the subject insertion instrument described in any one of the aforementioned means. While sending information on the position and speed of the tip of the biopsy instrument obtained by the method, feedback control is performed between the tip of the biopsy instrument and the target position of the biopsy instrument, and the biopsy instrument is automatically moved to the target position. It is designed to guide you to.

[0012]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 is a block diagram showing an MRI apparatus used for carrying out the method for detecting the tip of a subject insertion instrument according to the present invention. This MRI apparatus obtains a tomographic image of a diagnostic region by utilizing a nuclear magnetic resonance (hereinafter abbreviated as "NMR") phenomenon occurring in a living body tissue of a subject, and as shown in FIG. The generating unit 1, the gradient magnetic field generating unit 2, the gradient magnetic field power source 3, the probe 4, the high frequency transmitting / receiving unit 5, the calculator 6, and the display 7 are included.

The static magnetic field generating means 1 generates a uniform static magnetic field around the subject 9 placed on the table 8 in a direction orthogonal to the body axis direction. It is arranged in a space with a certain space around the table 8 to be mounted, and is composed of, for example, a permanent magnet or a magnetic field generating coil. The gradient magnetic field generating means 2 applies X, Y, Z to the subject 9.
Which gives gradient magnetic fields Gx, Gy, Gz in the three axial directions of
It is composed of a gradient magnetic field coil wound in three axial directions of X, Y, and Z, and is arranged in a space having a certain space around the table 8. The gradient magnetic field power supply 3 drives the gradient magnetic field generating means 2 and drives the gradient magnetic field coils wound in the three axial directions.

The probe 4 irradiates a high-frequency signal to the diagnostic region of the subject 9 and receives a high-frequency signal emitted by the NMR phenomenon of the living tissue of the subject 9, and has an irradiation coil inside. And a receiving coil. The high frequency transmitter / receiver 5 drives the probe 4 to irradiate and receive a high frequency signal on the subject 9. The computer 6 controls the gradient magnetic field power source 3 and the high frequency transmitting / receiving unit 5 in accordance with a pulse sequence at the time of imaging, and also performs an image reconstruction calculation using the high frequency signal received by the probe 4, and for example, a CPU ( Central processing unit). Further, the display 7 receives the image signal generated by the computer 6 and displays it as a tomographic image, and is composed of, for example, a CRT.

Next, a method for detecting the tip of the subject insertion instrument carried out by using such an MRI apparatus will be described.
FIG. 2 is a timing diagram showing a pulse sequence in the first embodiment of the method of detecting the tip of the subject insertion instrument. In this embodiment, irradiation of a high frequency signal and application of a gradient magnetic field are simultaneously performed on a region of interest including a biopsy device inserted into the diagnosis site from the outside of the subject to selectively excite the region of interest, and the tip of the biopsy device is selected. A gradient magnetic field is applied along the moving direction of the part to generate an echo, the received echo is converted into a projection signal by Fourier transform, the phase distribution of the projection signal is obtained, and the biopsy instrument is applying the gradient magnetic field. The position and speed of the tip portion are obtained from the position and the magnitude of the phase change caused by the movement of the tip portion.

Referring now to FIG. 3, a region of interest including a biopsy instrument inserted from the outside of the subject into the diagnosis site is indicated by reference numeral 10. In the region of interest 10, a biopsy instrument 11 such as a biopsy needle or a catheter is shown. It is assumed that the tip portion 12 is inside and the tip portion 12 is moving in the plane of the region of interest 10 along the X direction at a velocity v. The biopsy instrument 11 is made of a non-magnetic substance, and the tip 12 thereof contains a substance that causes an NMR phenomenon by irradiation of a high frequency signal in a magnetic field space, for example, a substance containing hydrogen, carbon and the like. There is. In such a state, the way, the time t ₀ shown in FIG. 2 2
A high frequency signal (RF) 13 shown in (b) and a gradient magnetic field (Gz) 14 whose magnetic field strength changes in the Z direction shown in FIG. 2 (c) are simultaneously applied to selectively excite the cross section of the region of interest 10. To do. At this time, the distal end portion of the biopsy instrument 11 is denoted by reference numeral 1.
It is in position 2. Next, a gradient magnetic field (Gx) 15 whose magnetic field strength changes in the X direction shown in FIG. 2D is applied for a time T, and the polarity of the amplitude of this gradient magnetic field 15 is inverted and applied for a time 2T. At this time, at time t _{1 two} hours after the application of the gradient magnetic field 15 in the X direction,
Since the time integral value of the amplitude of the gradient magnetic field 15 becomes "0", the echo 16 is generated as shown in FIG. 2 (e). The echo 16 is sampled by the high frequency transmitting / receiving unit 5 via the probe 4 shown in FIG. 1 and stored in the computer 6.

Here, from time t ₀ to t ₁ shown in FIG.
In the meantime, in FIG.
2'to the position 12 ', the phase of the magnetic spin of the substance contained in the tip 12 is as shown in FIG.
When the gradient magnetic field 15 in the X direction shown in (d) is applied, the magnetic field rotates at a magnitude proportional to its moving speed v.
Its magnitude is expressed by equation (1), where γ is the gyromagnetic ratio, G is the amplitude of the gradient magnetic field, and θ is the magnitude of the phase. With this equation (1), the movement of the tip portion 12 of the biopsy instrument 11 shown in FIG. 3 can be replaced by a phase change of the magnetic spin, and the echo 1 obtained as shown in FIG.
By examining the phase of 6, the position and speed of the tip 12 of the biopsy instrument 11 can be detected.

Next, the echo 1 stored in the computer 6
6 is Fourier-transformed along the X direction, and the value of the real part and the value of the imaginary part are used to obtain the phase distribution as shown in the graph in the lower part of FIG. Since this is the result of the Fourier transform along the X direction, it represents the projection in the Y direction. Biopsy instrument 1
The tip of No. 1 moves from the position 12 to the position 12 'between times t ₀ and t ₁ shown in FIG. 2 (a) and receives the application of the gradient magnetic field 15 in the X direction as described above. Causes the phase of the magnetic spin of the substance in the tip 12 to rotate,
A place where the phase changes is found as shown by the reference numeral 17 in the graph in the lower part of FIG. In this case, the region of interest 10
It is assumed that all biological tissue or material in the cross-section is stationary and that only biopsy device 11 is moving and causing a phase change. Therefore, it can be seen that the position indicated by reference numeral 17 in the lower graph of FIG. 3 indicates the position of the tip portion 12 ′ of the biopsy instrument 11. Further, the velocity v of the tip portion 12 of the biopsy instrument 11 at the time t ₁ can be obtained by calculating T = t ₁ in the above-mentioned formula (1). In the graph in the lower part of FIG. 3, the part denoted by reference numeral 18 shows the phase distribution due to the biological tissue or substance in the cross section of the region of interest 10, which is the background noise.

Thus, as shown in FIG. 3, the position of the tip 12 of the biopsy instrument 11 that moves one-dimensionally within the region of interest 10 as a two-dimensional plane does not necessarily obtain a two-dimensional image. , As shown in FIG. 2E, it can be known by measuring only one echo 16. Therefore, the time resolution for detecting the position of the biopsy instrument 11 inserted into the subject is improved, and by repeating the above measurement in a short time, the position of the tip portion 12 of the biopsy instrument 11 that changes from moment to moment can be determined. It is possible to monitor in real time.

FIG. 4 is a timing diagram showing a pulse sequence in the second embodiment of the method for detecting the tip of the subject insertion instrument. In this embodiment, irradiation of a high-frequency signal and application of a gradient magnetic field are simultaneously performed on a region of interest including a biopsy device inserted into the diagnosis site from the outside of the subject to selectively excite the region of interest, and A gradient magnetic field is applied along the moving direction of the tip to generate the first echo, and then the region of interest is selectively excited again, and the same direction as that applied to generate the first echo is tilted. A magnetic field is applied to generate a second echo, each received echo is transformed into a projection signal by Fourier transform, the phase distribution of this projection signal is determined, and the phase distribution obtained from the first echo and the The background noise is removed by taking the difference from the phase distribution obtained from the two echoes, and the phase change caused by the movement of the tip of the biopsy instrument during the application of the gradient magnetic field is emphasized. From the magnitude of the position and phase and requests the position and speed of the tip portion.
This embodiment is different from the first embodiment shown in FIGS. 2 and 3 in that the cross section of the region of interest 10 includes an element that causes rotation of the phase of the magnetic spin, such as blood flow, and the biopsy instrument 11 has the same structure. This is applied when it is difficult to identify the tip portion 12.

In FIG. 5, a region of interest 10 including a biopsy instrument inserted from the outside of the subject into the diagnosis site is indicated by reference numeral 10. In the region of interest 10, a biopsy instrument 11 such as a biopsy needle or a catheter is shown. It is assumed that the tip portion 12 is inside and the tip portion 12 is moving in the plane of the region of interest 10 along the X direction at a velocity v. In this state, as shown in FIG.
At time t ₀ , the high frequency signal (RF) shown in FIG.
13 and a gradient magnetic field (Gz) 14 whose magnetic field strength changes in the Z direction shown in FIG. 4C are simultaneously applied to selectively excite the cross section of the region of interest 10. Next, a gradient magnetic field (Gx) 15 whose magnetic field strength changes in the X direction shown in FIG. 4D is applied for a time T, and the polarity of the amplitude of this gradient magnetic field 15 is inverted and applied for a time 2T. At this time, the above X
Time 2T after the application of the gradient magnetic field 15 in the direction t
_{At 1} , the time integrated value of the amplitude of this gradient magnetic field 15 becomes "0", so as shown in FIG.
Occurs. The echo 16 is sampled by the high frequency transmitting / receiving unit 5 via the probe 4 shown in FIG.
Is stored in At this time, the tip portion of the biopsy instrument 11 is at the position of reference numeral 12 shown in FIG.

Next, at time t ₂ , the high frequency signal (RF) 19 shown in FIG. 4B and the gradient magnetic field (Gz) 20 whose magnetic field strength changes in the Z direction shown in FIG. 4C are applied simultaneously. Then, the cross section of the region of interest 10 is selectively excited again.
Next, a gradient magnetic field (Gx) 21 whose magnetic field strength changes in the X direction shown in FIG. 4D is applied for a time T, and the polarity of the amplitude of the gradient magnetic field 21 is inverted and applied for a time 2T. At this time, the gradient magnetic field 21 is applied at time t ₃ 2T after the application of the gradient magnetic field 21 in the X direction.
Since the time integral value of the amplitude of is 0, the echo 22 is generated as shown in FIG. The echo 22 is sampled by the high frequency transmitting / receiving unit 5 via the probe 4 shown in FIG. 1 and stored in the computer 6. At this time, the tip portion of the biopsy instrument 11 is designated by reference numeral 1 as shown in FIG.
It has moved from position 2 to position 12 '.

Next, the time t ₁ stored in the computer 6
Fourier transform the echo 16 at along the X direction,
Using the value of the real part and the value of the imaginary part, the phase distribution is obtained as shown in the lower graph of FIG. Similarly, the echo 22 at time t ₃ stored in the computer 6 is X
Fourier transform is performed along the direction, and the phase distribution is obtained using the value of the real part and the value of the imaginary part as shown in the graph in the lower part of FIG. Here, in FIG. 5A, the part indicated by the reference numeral 23 indicates the phase change part at time t ₁ ,
In FIG. 5B, the part indicated by reference numeral 24 is the time t ₃
Shows the phase change part at. In addition, in FIG. 5A and FIG. 5B, the portions denoted by reference numeral 18 respectively indicate background noise. Since the time t ₁ to t ₃ is short, it can be considered that the background noises 18, 18 are stationary during that time, and the phase distribution shown in the lower graph of FIG. (b) by taking the difference between the phase distribution shown in the lower part of the graph, the background noise 18 and 18 is removed, only the phase changing portion 24 in the phase change portion 23 and the time t ₃ at time t ₁ is highlighted To be done.

In FIG. 5A, the phase change portion 23 is
The position of the distal end portion 12 of the biopsy instrument 11 at time t ₁ is shown, and the phase change portion 24 in FIG.
The position of the tip 12 'of the biopsy device 11 at ₃ is shown. Therefore, by taking the difference of the above-mentioned phase distribution,
The position change of the distal end portion 12 of the biopsy instrument 11 which changes moment by moment can be obtained and can be monitored in real time. Further, the speed of the tip portion 12 can be obtained from the amount of positional change of the tip portion 12 of the biopsy instrument 11.

FIG. 6 is a timing diagram showing a pulse sequence in the third embodiment of the method for detecting the tip of the subject insertion instrument. In this embodiment, irradiation of a high-frequency signal and application of a gradient magnetic field are simultaneously performed on a region of interest including a biopsy device inserted into the diagnosis site from the outside of the subject to selectively excite the region of interest, and A gradient magnetic field was applied along one direction of a plane including the moving tip to generate a first echo, and then the region of interest was selectively excited again and applied to generate the first echo. A second echo is generated by applying a gradient magnetic field along another direction of the moving surface of the tip of the biopsy instrument, which is orthogonal to the above, and converts each received echo into a projection signal by Fourier transform, The phase distribution of this projection signal is obtained, and the position and velocity of the tip portion are two-dimensionally obtained from the phase distribution obtained from the first echo and the phase distribution obtained from the second echo. And this embodiment is different from the above-mentioned first and second embodiments, and is applied when the biopsy instrument 11 moves two-dimensionally in a two-dimensional plane, for example, in the X and Y directions. Is.

In FIG. 7, a region of interest 10 including a biopsy instrument inserted into the diagnosis site from the outside of the subject is indicated by reference numeral 10. In the region of interest 10, a biopsy instrument 11 such as a biopsy needle or a catheter is shown. It is assumed that the tip portion 12 has entered and is moving in the plane of the region of interest 10 at a velocity vx along the X direction and at a velocity vy along the Y direction. In this state, as shown in FIG. 6, at time t ₀ 6
A high frequency signal (RF) 13 shown in (b) and a gradient magnetic field (Gz) 14 whose magnetic field strength changes in the Z direction shown in FIG. 6C.
And are simultaneously applied to selectively excite the cross section of the region of interest 10. Next, a gradient magnetic field (Gx) 15 whose magnetic field strength changes in the X direction shown in FIG. 6D is applied for a period of time T, and the polarity of the amplitude of this gradient magnetic field 15 is inverted to obtain a period of 2T.
Only apply. At this time, the time integral value of the amplitude of the gradient magnetic field 15 becomes “0” at time t ₁ 2T after the application of the gradient magnetic field 15 in the X direction.
An echo 16 is generated as shown in (f). This echo 16 is transmitted through the probe 4 shown in FIG.
Are sampled in and stored in the computer 6. At this time, the distal end portion of the biopsy instrument 11 has a reference numeral 12 shown in FIG.
In the position.

Next, at time t ₂ , the high frequency signal (RF) 19 shown in FIG. 6B and the gradient magnetic field (Gz) 20 whose magnetic field strength changes in the Z direction shown in FIG. 6C are applied simultaneously. Then, the cross section of the region of interest 10 is selectively excited again.
Next, a gradient magnetic field (Gy) 25 whose magnetic field strength changes in the Y direction shown in FIG. 6E is applied for a time T, and the polarity of the amplitude of this gradient magnetic field 25 is inverted and applied for a time 2T. At this time, the gradient magnetic field 25 is applied at time t _{3 which} is 2T after the application of the gradient magnetic field 25 in the Y direction.
Since the time integrated value of the amplitude of is 0, an echo 26 is generated as shown in FIG. 6 (f). The echo 26 is sampled by the high frequency transmitting / receiving unit 5 via the probe 4 shown in FIG. 1 and stored in the computer 6. At this time, the tip portion of the biopsy instrument 11 has moved from the position 12 to the position 12 'as shown in FIG.

Next, the time t ₁ stored in the computer 6
Fourier transform the echo 16 at along the X direction,
Using the value of the real part and the value of the imaginary part, the phase distribution is obtained as shown in the graph in the X direction at the bottom of FIG. 7. Similarly, the echo 26 at the time t ₃ stored in the computer 6 is Fourier transformed along the Y direction, and the value of the real part and the value of the imaginary part are used to form a graph in the Y direction on the left side of FIG. Obtain the phase distribution as shown. Here, in FIG. 7, the phase change portion denoted by reference numeral 27 is the biopsy instrument 11 at time t ₁ .
The position x and the speed vx of the tip portion 12 of the biopsy instrument 11 at the time t ₃ are indicated by the phase change portion 28.
The position y and the speed vy of the tip portion 12 'of the are shown. In addition, in the two graphs of FIG. 7, the part indicated by reference numeral 18 indicates the background noise in each phase distribution.

Since the time t ₁ to t ₃ is short, it can be considered that the background noises 18 and 18 are stationary and the biopsy instrument 11 is moving at a constant speed during that time. Therefore, the position and velocity at each of the times t ₁ and t ₃ are obtained by the following equations. That is, the time t
_{In 1} , And at time t ₃ , Becomes In this way, the biopsy instrument 11 that moves two-dimensionally
The position of the tip portion 12 can be known only by obtaining the phase distributions in two orthogonal directions without measuring the two-dimensional image.

In the third embodiment described with reference to FIGS. 6 and 7, when the biopsy instrument 11 moves two-dimensionally in a two-dimensional plane, for example, in the X and Y directions, the tip portion 12 of the biopsy instrument 11 is moved. The position and velocity are obtained. If this idea is extended to three dimensions, when the biopsy instrument 11 moves three-dimensionally in, for example, the X, Y, and Z directions, the position of the tip 12 and The speed can be calculated. That is, irradiation of a high-frequency signal and application of a gradient magnetic field are simultaneously performed on a region of interest including a biopsy instrument inserted from the outside of the subject into a diagnostic region to selectively excite the region of interest, and the moving tip of the biopsy instrument is moved. A gradient magnetic field is applied along one direction of the volume containing the part to generate a first echo, and then the region of interest is selectively excited again, and is orthogonal to that applied to generate the first echo. A gradient magnetic field is applied along the other direction of the moving volume of the biopsy instrument tip to generate a second echo, and then the region of interest is selectively excited again, and the first and second Each echo received is generated by applying a gradient magnetic field along one direction of the moving volume of the biopsy instrument tip, which is orthogonal to any of the applied echoes to generate an echo. The Fourier Conversion to a projection signal by this conversion, the phase distribution of this projection signal is obtained, and the first phase distribution obtained from the first echo and the second phase obtained in the direction orthogonal to the first phase distribution obtained from the second echo are obtained. The position and velocity of the tip portion are three-dimensionally determined from the second phase distribution and the third phase distribution in the direction orthogonal to any of the first and second phase distributions obtained from the third echo. You can do this.

FIG. 8 is a timing diagram showing a pulse sequence in the fourth embodiment of the method for detecting the tip of the subject insertion instrument. In the embodiments of FIGS. 2 to 7 described above, the case where the position of the tip 12 is detected from the phase change due to the substance that causes the NMR phenomenon by the irradiation of the high frequency signal contained in the tip 12 of the biopsy instrument 11 will be described. I showed you
In the fourth embodiment, the position of the tip 12 of the biopsy instrument 11 is detected from the phase change caused by the difference in magnetic susceptibility at the boundary between the biopsy instrument 11 itself and the living tissue of the subject. To do.

In FIG. 9, a region of interest including a biopsy instrument inserted into the diagnosis site from the outside of the subject is indicated by reference numeral 10, and in the region of interest 10, a biopsy instrument 11 such as a biopsy needle or a catheter is shown. It is assumed that the tip portion 12 is inside and the tip portion 12 is moving in the plane of the region of interest 10 along the X direction at a velocity v. In this state, as shown in FIG.
At time t ₀ , the high frequency signal (RF) shown in FIG.
13 and a gradient magnetic field (Gz) 14 whose magnetic field strength changes in the Z direction shown in FIG. 8C are simultaneously applied to selectively excite the cross section of the region of interest 10. Next, a gradient magnetic field (Gx) 15 whose magnetic field strength changes in the X direction shown in FIG. 8D is applied for a time T, and the polarity of the amplitude of this gradient magnetic field 15 is inverted and applied for a time 2T. At this time, the above X
Time 2T after the application of the gradient magnetic field 15 in the direction t
_{At 1} , the time integrated value of the amplitude of this gradient magnetic field 15 becomes “0”, so that the echo 16 is generated as shown in FIG.
Occurs. The echo 16 is sampled by the high frequency transmitting / receiving unit 5 via the probe 4 shown in FIG.
Is stored in

Next, the time t ₁ stored in the computer 6 is stored.
Fourier transform the echo 16 at along the X direction,
Using the value of the real part and the value of the imaginary part, the phase distribution is obtained as shown in the graph in the lower part of FIG. Where “Radiology”
(May 1990), pp. 561-565, "Evaluation of
the Susceptibility Effect on the Phase Images ofa
As described in “Simple Gradient Echo”, it is known that the difference in magnetic susceptibility causes a phase change at the boundary of materials having different magnetic susceptibility. Therefore, in this embodiment, the magnetic field is arranged in the X direction. In the phase distribution along the X direction of the cross section (10) including the biopsy instrument 11 shown in FIG.
As shown in FIG. 5, the position with the phase difference as shown by the part with the reference numeral 29 and the part with the reference numeral 30 with the tip 12 of the biopsy instrument 11 as the boundary is the tip 12 of the biopsy instrument 11 to be obtained. It can be seen that it indicates the position of. Note that the method and the three-dimensional measurement method described in the embodiments of FIGS. 2 to 7 can be applied to this embodiment, respectively.

The MRI apparatus used for carrying out the method for detecting the tip of the subject insertion instrument according to each of the embodiments configured as described above is configured as shown in FIG. 1 described above. And in this MRI apparatus, the display 7
The biopsy instrument 1 inserted into the diagnostic site from outside the subject 9
A tomographic image measured in advance for the region of interest 10 including 1 is displayed, and the position information of the tip portion 12 of the biopsy instrument 11 obtained by the method for detecting the tip of the subject insertion instrument according to any of the above-described embodiments is used as the tomographic image. It is designed to be displayed superimposed on the image. That is, as shown in FIG. 10, a tomographic image 31 of the region of interest 10 is displayed on the screen of the display 7, and the detected positional information 32 of the tip 12 of the biopsy instrument 11 is displayed on the tomographic image. It is displayed superimposed on 31. This makes it possible to clearly know the relationship between the position of the distal end portion 12 of the biopsy instrument 11 inserted into the diagnosis site from the outside of the subject 9 and the living tissue at the diagnosis site.

FIG. 12 is a block diagram showing another embodiment of the MRI apparatus according to the present invention. In this embodiment, a biopsy instrument insertion guide mechanism 33 is connected to the computer 6 shown in FIG. This biopsy instrument insertion guide mechanism 33 is
A device for automatically guiding a biopsy instrument 11 such as a biopsy needle or a catheter to be inserted from the outside of the subject 9 into a diagnostic site inside,
As shown in FIG. 11 (a), the internal configuration is such that the target position r ₀ and the target speed v ₀ of the biopsy instrument 11 are input and the current position r and the current speed v are input to perform feedback control of the control device 34. And a drive mechanism 35 for inputting a control signal output by the feedback control of the control device 34 to insert and drive the biopsy instrument 11. Then, the current information (r, v) input to the control device 34.
As the signal of, the information of the current position and speed of the tip portion 12 of the biopsy instrument 11 obtained by the method for detecting the tip of the subject insertion instrument according to any of the above-described embodiments may be sent. As a result, the biopsy instrument insertion guide mechanism 33 as a whole performs feedback control with preset target information (r ₀ , v ₀ ) of the distal end portion 12 of the biopsy instrument 11 to perform the biopsy. The inspection tool 11 is automatically guided to the target position.

The image display in the feedback control of the insertion of the biopsy instrument 11 is as shown in FIG. 11 (b).
A tomographic image measured in advance for the region of interest 10 of the diagnostic region of the subject 9 is displayed, and the target position 36 of the distal end portion 12 of the biopsy instrument 11 and the current position 37 detected momentarily are displayed on the tomographic image 31. . Then, by the feedback control described above, the current position 37 with respect to the target position 36 is
Sequentially approach each other, and the insertion guidance of the biopsy instrument 11 is stopped when they coincide with each other. In addition, although the biopsy instrument 11 is shown by the broken line in FIG. 11B, the biopsy instrument 11 is not displayed in the actual image.

[0037]

Since the method for detecting the tip of the subject insertion instrument in the MRI apparatus according to the present invention is configured as described above,
Irradiation of a high-frequency signal and application of a gradient magnetic field are simultaneously performed on a region of interest including a biopsy instrument inserted from the outside of the subject into a diagnostic region to selectively excite the region of interest, and the tip portion of the biopsy instrument is moved in the moving direction. A gradient magnetic field is applied along it to generate an echo, the received echo is converted into a projection signal by Fourier transform, the phase distribution of this projection signal is obtained, and the tip of the biopsy instrument is moved during the application of the gradient magnetic field. By obtaining the position and speed of the tip from the position and the magnitude of the phase change caused, the position of the tip can be detected without imaging the tip of the biopsy instrument. From this, for example, no special hardware for achieving a high gradient magnetic field strength and a fast magnetic field rise time for applying the EPI method is required, and the device can be realized with the conventional device configuration. It is possible to prevent the cost from becoming high as well as shaping. Further, since the measurement time is not significantly shortened, it is possible to prevent the image quality from deteriorating without sacrificing the resolution and S / N of the tomographic image of the obtained diagnostic region.

Further, according to the MRI apparatus of the present invention,
On the display, while displaying a tomographic image measured in advance for the region of interest including the biopsy instrument inserted into the diagnosis site from the outside of the subject, the biopsy instrument obtained by the above-described subject insertion instrument tip detection method is displayed. The positional information of the tip portion can be displayed by being superimposed on the tomographic image. Therefore, the position of the tip of the biopsy instrument inserted into the diagnostic site from the outside of the subject,
The relationship between the diagnosis site and the living tissue can be clearly known.

Furthermore, in the one in which the biopsy instrument insertion guide mechanism is connected to the computer of the MRI apparatus, the biopsy instrument insertion guide mechanism of the biopsy instrument obtained by the above-described method for detecting the tip of the subject insertion instrument is detected. Automatically guiding the biopsy instrument to the target position by sending information on the position and speed of the tip and performing feedback control with a preset target position of the tip of the biopsy instrument. You can

[Brief description of the drawings]

FIG. 1 is a block diagram showing an MRI apparatus used for carrying out the method for detecting the tip of a subject insertion instrument according to the present invention.

FIG. 2 is a timing diagram showing a pulse sequence in a first embodiment of the method according to the invention.

FIG. 3 is an explanatory diagram showing a change in phase distribution due to a tip portion of the biopsy instrument in the first embodiment.

FIG. 4 is a timing diagram showing a pulse sequence in a second embodiment of the method according to the invention.

FIG. 5 is an explanatory diagram showing a change in phase distribution due to the tip of the biopsy instrument in the second embodiment.

FIG. 6 is a timing diagram showing a pulse sequence in a third embodiment of the method according to the invention.

FIG. 7 is an explanatory diagram showing changes in phase distribution due to the tip of the biopsy instrument in the third embodiment.

FIG. 8 is a timing diagram showing a pulse sequence in a fourth embodiment of the method according to the invention.

FIG. 9 is an explanatory diagram showing changes in the phase distribution due to the tip of the biopsy instrument according to the fourth embodiment.

10 is an explanatory diagram showing an example of a screen display on a display device in the MRI apparatus shown in FIG.

11 is a block diagram showing an internal configuration of a biopsy instrument insertion guide mechanism in the MRI apparatus shown in FIG. 12 and an explanatory diagram showing an example of a screen display on a display by the operation of the biopsy instrument insertion guide mechanism.

FIG. 12 is a block diagram showing another embodiment of the MRI apparatus according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Static magnetic field generation means 2 ... Gradient magnetic field generation means 3 ... Gradient magnetic field power supply 4 ... Probe 5 ... High frequency transmission / reception part 6 ... Computer 7 ... Indicator 8 ... Table 9 ... Subject 10 ... Region of interest 11 ... Biopsy instrument 12, 12 '... Tip 31 ... Tomographic image 32 ... Position information of tip 33 ... Biopsy instrument insertion guide mechanism 36 ... Target position 37 ... Current position

Claims (7)

[Claims] 1. A static magnetic field generating means for applying a static magnetic field to a subject, and a gradient magnetic field generating means for applying a gradient magnetic field to the subject,
A gradient magnetic field power source for driving the gradient magnetic field generating means, a probe for irradiating a high-frequency signal to the diagnostic region of the subject and receiving a high-frequency signal emitted by nuclear magnetic resonance of the biological tissue of the subject, An image is generated using the high-frequency signal received by the probe while controlling the gradient magnetic field power supply and the high-frequency transmission / reception unit according to the pulse sequence at the time of imaging, by driving the probe to irradiate and receive the high-frequency signal. An MRI apparatus comprising a computer for performing reconstruction calculation and a display for inputting an image signal generated by the computer and displaying the image as a tomographic image. Irradiation of a high-frequency signal and application of a gradient magnetic field are simultaneously performed on a region of interest including the instrument to selectively excite the region of interest, and the tip of the biopsy instrument is A gradient magnetic field is applied along the moving direction to generate an echo, the received echo is converted into a projection signal by Fourier transform, the phase distribution of this projection signal is obtained, and the tip of the biopsy instrument is being applied with the gradient magnetic field. The method for detecting the tip of a subject insertion instrument, characterized in that the position and speed of the tip portion are obtained from the position and the magnitude of the phase change caused by the movement of the object. 2. The MRI apparatus according to claim 1,
Irradiation of a high-frequency signal and application of a gradient magnetic field are simultaneously performed on a region of interest including a biopsy instrument inserted from the outside of the subject to a diagnostic site to selectively excite the region of interest, and the moving direction of the distal end portion of the biopsy instrument. By applying a gradient magnetic field along the line to generate a first echo, then selectively exciting the region of interest again, and applying a gradient magnetic field in the same direction as applied to generate the first echo. Generate a second echo, convert each received echo into a projection signal by Fourier transform, determine the phase distribution of this projection signal,
Background noise is removed by taking the difference between the phase distribution obtained from the first echo and the phase distribution obtained from the second echo, which is caused by the movement of the tip of the biopsy instrument during the application of the gradient magnetic field. A method for detecting the tip of a subject insertion instrument, which emphasizes a change in phase and obtains the position and speed of the tip from the position of the phase change and the magnitude of the phase. 3. The MRI apparatus according to claim 1,
Irradiation of a high-frequency signal and application of a gradient magnetic field are simultaneously performed on a region of interest including a biopsy instrument inserted into the diagnosis site from the outside of the subject to selectively excite the region of interest, and the moving tip of the biopsy instrument is fixed. A gradient magnetic field is applied along one direction of the plane including the first echo to generate the first echo, and then the region of interest is selectively excited again, which is orthogonal to that applied to generate the first echo. A gradient magnetic field is applied along another direction of the moving surface of the inspection instrument tip to generate a second echo, and each received echo is transformed into a projection signal by Fourier transform, and the phase of this projection signal is changed. An object insertion device characterized in that the position and velocity of the tip portion are two-dimensionally obtained from the phase distribution obtained from the first echo and the phase distribution obtained from the second echo by obtaining the distribution. Tip detection method. 4. The MRI apparatus according to claim 1,
Irradiation of a high-frequency signal and application of a gradient magnetic field are simultaneously performed on a region of interest including a biopsy instrument inserted into the diagnosis site from the outside of the subject to selectively excite the region of interest, and the moving tip of the biopsy instrument is fixed. A gradient magnetic field is applied along one direction of the containing volume to generate a first echo, and then the region of interest is selectively excited again and orthogonally to that applied to generate the first echo. A gradient magnetic field is applied along the other direction of the moving volume of the inspection instrument tip to generate a second echo, and then the region of interest is selectively excited again to generate the first and second echoes. A gradient magnetic field is applied along one direction of the moving volume of the biopsy instrument tip that is orthogonal to any of the applied echoes to generate a third echo, and each received echo is Fourier-transformed. By conversion Converted to the projection signal, the phase distribution of this projection signal is obtained, the first phase distribution obtained from the first echo, and the second phase in the direction orthogonal to the first phase distribution obtained from the second echo The position and velocity of the tip portion are three-dimensionally obtained from the phase distribution and the third phase distribution in the direction orthogonal to any of the first and second phase distributions obtained from the third echo. The method for detecting the tip of a subject insertion instrument. 5. The biopsy device comprises a non-magnetic material,
5. The method for detecting the tip of a subject insertion instrument according to any one of claims 1 to 4, wherein a substance that causes nuclear magnetic resonance in the magnetic field space by irradiation of a high-frequency signal is built in the tip portion thereof. . 6. A static magnetic field generating means for applying a static magnetic field to the subject, and a gradient magnetic field generating means for applying a gradient magnetic field to the subject,
A gradient magnetic field power source for driving the gradient magnetic field generating means, a probe for irradiating a high-frequency signal to the diagnostic region of the subject and receiving a high-frequency signal emitted by nuclear magnetic resonance of the biological tissue of the subject, An image is generated using the high-frequency signal received by the probe while controlling the gradient magnetic field power supply and the high-frequency transmission / reception unit according to the pulse sequence at the time of imaging, by driving the probe to irradiate and receive the high-frequency signal. In an MRI apparatus having a computer for performing reconstruction calculation and a display for displaying an image signal generated by the computer as a tomographic image, the display is diagnosed from outside the subject. The subject according to claim 1, which displays a tomographic image measured in advance for a region of interest including a biopsy instrument inserted into the site. Information on the position of the tip portion of the biopsy device obtained by the input instrument tip detection method MRI apparatus being characterized in that so as to display superimposed on the tomographic image. 7. A static magnetic field generating means for applying a static magnetic field to the subject, and a gradient magnetic field generating means for applying a gradient magnetic field to the subject,
A gradient magnetic field power source for driving the gradient magnetic field generating means, a probe for irradiating a high-frequency signal to the diagnostic region of the subject and receiving a high-frequency signal emitted by nuclear magnetic resonance of the biological tissue of the subject, An image is generated using the high-frequency signal received by the probe while controlling the gradient magnetic field power supply and the high-frequency transmission / reception unit according to the pulse sequence at the time of imaging, by driving the probe to irradiate and receive the high-frequency signal. In an MRI apparatus comprising a computer for performing reconstruction calculation and a display for displaying an image signal generated by the computer as a tomographic image, in the computer, the computer from outside the subject to a diagnostic site A biopsy instrument insertion guide mechanism for guiding a biopsy instrument to be inserted is connected, and the biopsy instrument insertion guide mechanism is connected to the biopsy instrument insertion guide mechanism.
While sending the information of the position and speed of the tip of the biopsy instrument obtained by the method for detecting the tip of the subject insertion instrument according to any one of 1, the feedback control with the target position of the tip of the biopsy instrument is performed. An MRI apparatus characterized in that the biopsy instrument is automatically guided to a target position.