JP2019058461A - Magnetic resonance imaging apparatus, device position detection method using the same, device, and image-guided intervention support apparatus - Google Patents

Abstract

To detect a device position in real time and with accuracy and present it, in image-guided intervention using MRI.SOLUTION: A device provided with markers detectable with an MRI apparatus at plural positions is used and monoaxial projection nuclear magnetic-resonance signals of plural markers are acquired with respect to three axes during device insertion. A marker position is detected from a triaxial projection image to identify a device position. The detected marker position or the device position are superimposed and displayed on an image obtained by imaging an analyte.SELECTED DRAWING: Figure 8

Description

  The present invention relates to image-guided intervention techniques using Magnetic Resonance Imaging (MRI).

  In recent years, minimally invasive treatment for treating with minimal invasion to the living body has attracted attention. Specifically, puncturing treatment to treat cancer by percutaneously piercing a needle-shaped treatment device such as cryotherapy, radio wave treatment, microwave treatment, etc., biopsy (biopsy) to collect tissue, or There is intravascular treatment represented by catheter treatment, etc., and in treatment using these treatment devices, in order to accurately guide the treatment device (needle or catheter) to a treatment target such as tumor tissue to be treated in vivo , And living body images captured in real time using ultrasound and X-rays. In addition, MRI, which visualizes organs and tissues in the body in detail using static magnetic fields and electromagnetic waves (Radio Frequency: RF), has the advantage of being excellent in visualization of the contrast of living tissue and the treatment area (tissue degeneration). Guided treatment is also one of effective treatment means, and various MRI guided intervention techniques have been developed.

  For example, in Patent Document 1, a magnetic sensor is attached to an object to be tracked, and a gradient magnetic field coil of an MRI apparatus is activated, thereby detecting a signal induced to an induction coil and estimating a position or an orientation of the object Technology is disclosed. Further, Patent Document 2 discloses a technique for attaching three optical markers (bright spots) to a portion of the device which is not inserted into a subject, and detecting the position and inclination of the tip of the device from the position of the bright spots. . In Patent Document 3, a guide wire used at the time of catheter insertion is also used as an RF receiving coil, and a three-dimensional image is created using an RF signal detected by this RF receiving coil, and provided on the catheter from its central projection image. Techniques for detecting the position and orientation of a marker are disclosed. Further, Non-Patent Document 1 proposes a method of attaching a magnetic body to the tip of a catheter to generate a low signal area on an MR image and detect a treatment device position on a three-dimensional MR image.

JP 2011-509109 gazette Patent No. 4377645 Japanese Patent Application Publication No. 2003-24298

F. Settecase et al. "Magnetic Resonance-Guided Passive Catheter Tracking for Endovascular Therapy" Magn Reson Imaging Clin N Am 23 559-605 (2015)

  However, the method described in Patent Document 1 needs to include a signal processing unit separately from the MRI apparatus to process the signal from the magnetic sensor. The method described in Patent Document 2 estimates the position of the treatment device on the premise that the geometry of the marker located outside the body and the treatment device inserted in the body is constant, so the shape changes in the body It can not cope with the treatment device. Further, the methods described in Patent Document 3 and Non-Patent Document 1 have a limit in the real-time property of position detection in order to create a three-dimensional image. Further, in any of the above-described methods, there are problems in accuracy and time resolution in detecting the position of the treatment device.

  In order to solve the problems of the prior art described above, the present invention uses a device provided with markers that can be detected by an MRI apparatus at a plurality of positions, and performs uniaxial projection nuclear magnetic resonance signals of a plurality of markers in three axes during device insertion. The marker position is detected in a very short time by acquiring about. The accuracy of position detection can be enhanced by taking the difference between the case where the marker does not reflect the nuclear magnetic resonance signal (for example, the absence of the device) and the case where the marker reflects it.

  That is, one aspect of the present invention is an MRI apparatus provided with a device position detection function, which executes a predetermined pulse sequence and acquires an imaging unit that collects nuclear magnetic resonance signals generated from a subject, and the imaging unit collects And a signal processing unit for performing an operation using a nuclear magnetic resonance signal, wherein the pulse sequence executed by the imaging unit includes a device sequence for imaging a device inserted inside the subject, and the device The sequence for performing executes a step of acquiring nuclear magnetic resonance signals projected on one axis for each of three axes orthogonal to each other, and the signal processing unit performs projection of the three axes acquired for the device sequence. A device position detection unit that detects the position of the device using a nuclear magnetic resonance signal is provided.

  Another aspect of the present invention is a method of detecting the position of a device inserted in a subject, wherein the magnetic resonance imaging apparatus emits a non-selective excitation RF pulse, and then the first of three orthogonal axes is irradiated. Applying a readout gradient magnetic field to the first axis to obtain a nuclear magnetic resonance signal projected onto the first axis, and reading out the second gradient axis to the second axis different from the first axis among the three axes. To obtain a nuclear magnetic resonance signal projected onto the second axis, and applying a readout gradient magnetic field to a third of the three axes different from the first and second axes. And acquiring the nuclear magnetic resonance signal projected on the third axis, and the projected nuclear magnetic resonance signal acquired on each of the first, second and third axes to obtain the positions of the plurality of markers. Including the step of detecting.

In the device to which the method of detecting the position of the device of the present invention is applied, markers detectable by a magnetic resonance imaging apparatus are arranged at a plurality of different positions along the longitudinal direction. That is, the device of the present invention is a device inserted into the inside of a subject, wherein markers detectable by a magnetic resonance imaging apparatus are arranged at a plurality of different positions along the longitudinal direction, and the magnetic resonance imaging described above A nuclear magnetic resonance signal attributable to each marker detected by the device is a device that can be identified for each marker.
Furthermore, the present invention provides an image-guided intervention support device combining the above-described device and a magnetic resonance imaging apparatus.

  According to the present invention, the device position can be presented in real time and with high accuracy by detecting the device position from the three-axis projection nuclear magnetic resonance signal. This can increase the accuracy of the image-guided intervention.

The figure which shows the external appearance of the MRI apparatus to which this invention is applied. The figure which shows the whole structure of a MRI apparatus. The functional block diagram of a signal processing part. A figure explaining MRI guided treatment. The figure which shows an example of a treatment device. The figure which shows the procedure of the MRI guided treatment of 1st embodiment. The figure which shows an example of an imaging sequence. The figure which shows an example of the sequence for devices. (A)-(c) is a figure which shows the one-dimensional projection image of each axis obtained from the pulse sequence of FIG. The figure which shows an example of the navigation screen in a MRI guided treatment. (A), (b) is a figure which shows the other example of a navigation screen, respectively. (A)-(c) is a figure which shows another example of a navigation screen. The figure which shows another example of a navigation screen. The figure which shows the procedure of the MRI guided treatment of 2nd embodiment. FIG. 7 is a view for explaining the case of detecting a body movement phase from a one-dimensional projection image in the second embodiment, wherein (a) shows an imaging direction and (b) shows a body movement appearing in a one-dimensional projection image in the y direction Figure showing. (A)-(c) is a figure which shows the difference of a one-dimensional projection image.

Hereinafter, an embodiment of the MRI apparatus of the present invention will be described.
First, the entire configuration of an MRI apparatus to which the present invention is applied will be described. FIG. 1 is an external view of an MRI apparatus. The illustrated MRI apparatus is an MRI apparatus provided with a magnet 11 that generates a static magnetic field in the vertical direction, and a subject laid on a table 12 is inserted into an imaging space in the bore of the static magnetic field generating magnet 11 and imaged. This MRI apparatus is called an open type, and the periphery of the subject 1 is open to the outside of the imaging space so that a doctor who performs procedures such as surgery, treatment, and examination can directly access the subject 1 placed in the imaging space. It is done. For this reason, the open type MRI apparatus is suitable for interventional MRI in which a procedure is performed in parallel with imaging. However, the present invention is not limited to the open type MRI.

  Next, the general outline of the MRI apparatus of the present embodiment will be described with reference to FIG. The MRI apparatus 100 roughly includes an imaging unit 10 and a signal processing unit (arithmetic unit) 50. The imaging unit 10 includes a static magnetic field generating magnet 11, gradient magnetic field generating units (21, 22), RF transmitting units (31 to 34), receiving units (41 to 44), and a sequencer 15. The signal processing unit 50 includes a CPU 51 which also serves as a control system, and an input / output device and a storage device that accompany it.

  The static magnetic field generating magnet 11 generates a uniform static magnetic field in the space around the subject 1, and depending on the direction of the generated static magnetic field, the vertical magnetic field shown in FIG. There is a horizontal magnetic field system that generates a magnetic field in any direction. Further, depending on the static magnetic field generation source, there are a permanent magnet system, a normal conduction system, and a superconducting system. In the present embodiment, the system of the static magnetic field generating magnet 11 is not particularly limited.

  The gradient magnetic field generating unit drives the gradient magnetic field coils 21 and the three sets of gradient magnetic field coils 21 that generate gradient magnetic fields in three axial directions of X, Y and Z, which are coordinate systems (static coordinate systems) of the MRI apparatus. The gradient magnetic field power supply 22 is provided, and the gradient magnetic field power supply 22 of each coil is driven according to an instruction from the sequencer 15 to apply gradient magnetic fields Gx, Gy, Gz in three axial directions of X, Y, Z. At the time of imaging, the slice direction gradient magnetic field (Gs) is applied in the direction orthogonal to the slice plane (the imaging cross section) to set the slice plane with respect to the subject 1, and the rest substantially orthogonal to the slice plane and orthogonal to each other The phase encoding direction gradient magnetic field (Gp) and the frequency encoding direction gradient magnetic field (Gf) are applied in two directions, to encode position information of each direction in the echo signal.

  The RF transmission unit is for irradiating the subject 1 with an RF magnetic field that causes nuclear magnetic resonance of the nuclear spins of the atoms constituting the living tissue of the subject 1, and includes an RF oscillator 31, a modulator 32 and an RF amplifier 33. And an RF transmitter coil 34 on the transmitter side. The RF magnetic field output from the RF oscillator 31 is amplitude-modulated by the modulator 32 at a timing according to a command from the sequencer 15, and the amplitude-modulated RF magnetic field is amplified by the RF amplifier 33 and placed close to the object. By supplying the RF transmission coil 34, the RF magnetic field is irradiated to the subject 1.

  The RF transmission coil 34 of the transmission system and the gradient magnetic field coil 21 face the subject 1 in the static magnetic field space generated by the static magnetic field generating magnet 11 in the case of the vertical magnetic field method and in the horizontal magnetic field method. It is installed so as to surround the subject 1.

  The sequencer 15 is a control means for repeatedly applying an RF magnetic field and a gradient magnetic field in a predetermined pulse sequence, operates under the control of the CPU 51, and transmits various commands necessary for data acquisition of tomographic images of the object to the RF transmitter 30 and It is sent to the gradient magnetic field generator 20.

  The receiving unit 40 receives, as an echo signal, a nuclear magnetic resonance signal emitted by nuclear magnetic resonance of nuclear spins of atoms constituting the living tissue of the subject 1, and includes an RF receiving coil 41, a signal amplifier 42, A phase detector 43 and an A / D converter 44 are provided. The NMR signal of the response of the subject 1 induced by the RF magnetic field irradiated from the RF transmission coil 34 of the transmission system is detected by the RF receiving coil 41 arranged in proximity to the subject 1 and amplified by the signal amplifier 42. After that, the signal is divided into two orthogonal signals by the phase detector 43 at a timing according to a command from the sequencer 15. Each signal is converted into a digital signal by the A / D converter 44 and sent to the signal processing unit 50.

  The signal processing unit 50 includes a CPU 51 that controls the device and processes various data, and an internal memory, and further includes a display device including an external storage device such as the magnetic disk 61 and the optical disk 62, a liquid crystal display, etc. 63 and an operation unit 64. When the data from the receiving unit 40 is input to the CPU 51, the CPU 51 executes processing such as signal processing and image reconstruction, and displays the tomographic image of the subject 1 as a result on the display 63 and an external storage device. Recording on the magnetic disk 61 of FIG.

  The operation unit 64 is for inputting various control information of the MRI apparatus and control information of processing performed by the signal processing unit 50, and includes, for example, a mouse, a keyboard, and the like. The operation unit 64 is disposed close to the display 63, and the operator interactively controls various processes of the MRI apparatus through the operation unit 64 while looking at the display 63.

  In the signal processing unit 50, various pulse sequences which differ depending on the imaging method are stored in advance as a program. In this embodiment, in addition to the pulse sequence for imaging the subject, the position of the device inserted in the subject is detected during an intervention procedure in which the imaging is performed while inserting the device into the subject's body. A pulse sequence (sequence for device) for storing is stored. Details of the device sequence will be described later.

  When the pulse sequence and its parameters are set via the operation unit 64, the signal processing unit 50 (CPU 51) controls each unit of the imaging unit 10 via the sequencer 15 to perform imaging and reconstruct an image. In the intervention procedure, the device sequence is executed, and the device position is calculated or displayed using the signal obtained by the execution of the device sequence. That is, the signal processing unit 50 of the MRI apparatus functions as an image-guided intervention support device together with a device described later.

  An example of the function of the signal processing unit 50 for realizing such a function is shown in FIG. As shown in FIG. 3, the signal processing unit 50 performs a Fourier transform on the nuclear magnetic resonance signal acquired by the execution of the imaging pulse sequence and the sequence for the device sequence control 51 that controls the execution of the device sequence as needed. , Etc., and an image reconstruction unit 52 that generates an image, a device position detection unit 54 that detects a device position using a signal acquired by execution of a device sequence, and a display image to be displayed on a display device 63 And a display control unit 55 that controls display. The functions of the signal processing unit 50 may be realized as software executed by the CPU 51, but part or all of them may be realized by hardware such as an ASIC or an FPGA.

  Based on the configuration described above, an embodiment of the operation of the MRI apparatus of the present embodiment in the MRI-guided treatment will be described.

First Embodiment
First, MRI-guided treatment will be described with reference to FIG.
FIG. 4 shows a state in which a treatment device 403 such as a needle is guided to a treatment target 402 such as a tumor existing inside a human body 401 placed in an imaging space of the MRI apparatus 100. The MRI-guided treatment targets the treatment device 403 as a treatment target by simultaneously displaying the treatment target 402 and the treatment device 403 or the markers 404 to 406 attached to the treatment deviation on the MRI image displayed on the display device 63. Induce to 402.

  The treatment device 403 includes (1) a biopsy needle used for biopsy, (2) a treatment needle used for cryotherapy, radio wave treatment, microwave treatment and the like, and (3) catheters and guide wires used for endovascular treatment There are various devices that function in vivo, such as endovascular treatment devices such as (4) digestive endoscopes, laparoscopes, bronchoscopes, endoscopes such as neuroendoscopes, and the like.

  Although the present embodiment can be applied to any treatment device, here, a puncturing treatment in which a needle-shaped device is punctured percutaneously to treat cancer is described as an example. Puncture treatments include cryotherapy where cancer tissues are frozen and treated, or radio wave treatment, microwave treatment, laser treatment, etc., where heat treatment is performed. In puncture therapy, it is important to accurately guide the tip of the treatment device to the tumor to be the treatment target. Therefore, it is necessary to monitor the position of the treatment device and the position of the treatment target by MRI.

  The treatment device 403 includes a first marker (M1) 404, a second marker (M2) 405, and a third marker (M3) 406, which are marks of the treatment device 403, at a plurality of positions along the longitudinal direction. It is fixed. Each marker is composed of a magnetic body or a magnetic field generating coil that induces a decrease in signal intensity locally in MRI, or a material that induces an increase in signal intensity locally in MRI, such as a vitamin agent. The marker can be configured by applying a paint composed of such a material to the device or fixing a member. The markers are preferably distinguishable from each other, such as the degree of change, decrease or increase of the signal strength being different depending on the markers. As a method for making it possible to distinguish changes in signal strength, for example, the marker is made different in size or shape in the case of a member made of magnetic paint or magnetic material, and in the case of a magnetic field generating coil, the magnitude of the generated magnetic field Different, etc. can be taken.

  An example of a device using a magnetic field generating coil as a marker is shown in FIG. The therapeutic device 501 provided with this marker is configured to include a first marker (M1) 503, a second marker (M2) 504, and a third marker (M3) 505 in the conventional therapeutic device 502. These markers consist of a coil wound on the device at a predetermined distance d along the longitudinal direction of the treatment device 502. The distance d is not particularly limited, but it is preferable that the distance d be, for example, 10 mm or more, which can identify each marker. Further, even if the device is bent, it is preferable that the distance be, for example, 100 mm or less, which allows the direction of the device to be estimated from the distance between them. Here, the first marker 503 is a one-turn coil, the second marker 504 is a two-turn coil, and the third marker 505 is a three-turn coil, which are connected in series. Since these coils have different self-inductances, the magnetic fields generated by the respective coils are different when current is applied to these coils. That is, since each marker locally causes a decrease in signal intensity in MRI, and the degree of the change differs for each marker, the position of each marker can be specified.

  An example of the procedure of the MRI guided treatment using such a device will be described with reference to FIG.

  First, a subject is placed in an imaging space, and a device such as a biopsy needle or a catheter is inserted into the subject while performing imaging with an MRI apparatus as necessary. Conditions and parameters necessary for imaging are set after acquiring a positioning image of low spatial resolution when positioning the object in the imaging space.

  For example, when an instruction to start imaging is received via the operation unit 64 prior to insertion or progress of a device, the sequence control unit 51 executes a preset imaging sequence and starts imaging (S101, S102). . The imaging sequence is not particularly limited. However, when it is expected to repeat multiple imaging as in interventional MRI, a pulse sequence with a short measurement time, such as a gradient echo (GrE) system as shown in FIG. A pulse sequence is selected. That is, after applying a RF pulse 701 and a slice selection gradient magnetic field 702 to excite a predetermined region (slice) of the subject, a phase encoding gradient magnetic field 703 is applied and a readout gradient magnetic field 704 is applied, and an RF pulse is generated. An echo signal 705 is measured after a predetermined echo time TE from the application of the voltage 701. The above-described series of sequences are repeated at a predetermined repetition time TR to measure the number of echo signals necessary for image reconstruction. Although FIG. 7 shows a two-dimensional GrE system pulse sequence, it may be three-dimensional.

  The image reconstruction unit 52 performs an operation such as Fourier transform on the acquired echo signal to reconstruct an image, and generates image data. The image data is stored in the storage device and displayed on the display device 63 as necessary.

  After starting insertion of a device, when an instruction for device position detection is received through the operation unit 64 (S103), the sequence control unit 51 executes a device sequence (S104). As shown in FIG. 8, the sequence for the device performs the application of the non-selective RF pulse 801 and the measurement of the echo signal 803 by the readout gradient magnetic field 802 of one axis for each of three orthogonal axes. The echo signal measurement is a very short sequence of several tens of milliseconds. That is, the RF pulse 801a is irradiated to excite the entire region of interest in the body including the marker, and the echo signal 803a is measured by the readout gradient magnetic field 802a in the x direction. The image reconstruction unit 52 Fourier-transforms the echo signal 803 a to obtain a one-dimensional magnetic resonance signal distribution (one-dimensional projection image) projected on the x-axis. Similarly, an RF pulse 801b is irradiated to excite the entire region of interest, the echo signal 803b is measured by the readout gradient magnetic field 802b in the y direction, Fourier transformed, and a one-dimensional magnetic resonance signal projected on the y axis Get the distribution. Furthermore, the whole area of interest is excited by irradiating the RF pulse 801c, the echo signal 803c is measured by the readout gradient magnetic field 802c in the z direction, Fourier transformed, and the one-dimensional magnetic resonance signal distribution projected on the z axis Get

  In the magnetic resonance signal distribution of each axis, the position on each axis where the marker of the device is present appears as a high signal or a low signal. A one-dimensional projection image obtained from the pulse sequence of FIG. 8 is schematically shown in FIG. In the figure, the horizontal axis is position, and the vertical axis is signal strength. In this example, the marker shows the case where two markers M1 and M2 for locally reducing the signal intensity are provided, and the degree of signal reduction is such that the marker M2 is larger than the marker M1. FIG. 9 (a) is a one-dimensional magnetic resonance signal distribution 901 projected on the x-axis, where it is projected on the x-axis at the coordinate x1 at which the marker M1 is present and at the coordinate x2 at which the marker M2 is present. The one-dimensional magnetic resonance signal is locally reduced. Furthermore, the degree of signal degradation is larger at x2 than at x1. Therefore, from the distribution of one-dimensional magnetic resonance signals projected onto the x-axis, it can be determined that the x-coordinate of the marker M1 is x1 and the x-coordinate of the marker M2 is x2. Also, the one-dimensional magnetic resonance signal distribution 902 (FIG. 9B) projected on the y-axis and the one-dimensional magnetic resonance signal distribution 903 projected on the z-axis shown in FIG. c), as in the case of FIG. 9A, the y-coordinate of the marker M1 is y1, the y-coordinate of the marker M2 is y2, the z-coordinate of the marker M1 is z1, and the z-coordinate of the marker M2 is z2 It can be determined that That is, it can be detected that the coordinates of the marker M1 are (x1, y1, z1) and the coordinates of the marker M2 are (x2, y2, z2). Further, the angle of the line connecting these can be calculated from the coordinates of the markers M1 and M2, and the angle of this line can be regarded as the traveling direction of the device in a pseudo manner.

  Although the example of FIG. 9 shows the case of using a marker that induces a decrease in signal intensity locally in MRI, in the case of a marker that induces an increase in signal intensity locally, The position of the marker can be detected from the increase.

  The device position detection unit 54 detects the positions of markers appearing in these three-axis one-dimensional projected images, and calculates the orientation (traveling direction) of the device using the positions of a plurality of markers (S105). From the geometry of the device itself, the device tip location and orientation can be calculated if the device is made of a material that deforms or hardly deforms. In addition, when the device is bendable and deformable, each marker can be identified by making each marker distinguishable (the change degree of the signal intensity differs depending on the marker), thereby identifying each on projection data, The position and the direction can be calculated.

  The display control unit 55 receives the device position from the device position calculation unit 54, and superimposes and displays the device position on the image of the subject reconstructed by the image reconstruction unit 52 (S106). As an object image for displaying a device position, there are various modes such as a projection image obtained by processing a tomographic image or three-dimensional image data by MIP (maximum value projection) or MinIP (minimum value projection). An example of the navigation screen is shown in FIG. In this example, from the position of each of the markers (M1 to M3) 404 to 406 (FIG. 4) calculated in step S105, an image 1000 of a cross section including these markers is cut out from a previously obtained three-dimensional object image The marker position is superimposed and displayed on the image by black circles 1004 to 1006.

  The image 1000 may be an image obtained by MIP processing or the like of an image of a cross section including a device insertion position (puncture point) S and, for example, the first marker M 1904 or a three-dimensional image as shown in FIG. Also, along with the display of the marker position, a line connecting the markers is displayed as the device shape 1003 or, as shown in FIG. 11B, an extension of the line 1003 indicating the device is shown to indicate the traveling direction of the device. May be This allows the operator to intuitively grasp whether the device is moving toward or away from the treatment target 1002. In the case of the cross-sectional image of FIG. 10, all the marker positions are not necessarily included in the cross section, but the marker positions are projected and displayed on the cross section of the image 1000, and black circles are displayed according to the distance from the cross section of the marker positions. A luminance difference may be provided in 1004 to 1006.

  As another aspect of the display, as shown in FIG. 12, the marker position and the device shape may be displayed on three cross sections (Axial, Colonal, Sattittal) including the puncture point S and the treatment target 1002. In this case, the operator can intuitively grasp the three-dimensional traveling direction of the device. Further, as shown in FIG. 13, a tomographic image or MIP image of a plane passing a marker M1 provided at the tip of the device and orthogonal to the device advancing direction is displayed, and an image obtained by projecting the treatment target 1002 on that surface and the position of the device tip May be displayed superimposed. In the device traveling direction, for example, the direction of a line connecting two markers M1 and M2 is taken as the device traveling direction. The images of the various aspects described above may be displayed alone or in combination as appropriate.

  While checking the navigation screen (image 900), the operator judges whether to further advance the device (S107), and performs imaging (S102) and device position detection (S104 to S106) until the target position is reached. repeat.

  In the above description, step S103 determines whether or not position detection is to be performed according to an instruction via the operation unit 64. For example, when the device tip position approaches the target site, it is automatically determined. The device position to be superimposed on the display image may be updated with the newly acquired position information repeatedly at intervals.

  Also, although not shown in FIG. 6, when, for example, a biopsy using a device, freezing or thermal treatment is performed after the device reaches a target position, imaging is performed before and after the start to confirm the treatment effect It is also possible.

  According to the present embodiment, the imaging unit has one axis when detecting the position of the device inserted in the inside of the subject while using a device in which MRI distinguishable markers are attached to a plurality of longitudinal positions as the device. The step of acquiring the projected nuclear magnetic resonance signal is performed by imaging for a device sequence which is executed with respect to three axes orthogonal to each other, and the operation unit uses the three-axis projection nuclear magnetic resonance signal acquired in the device sequence. Detect device location. Since the device sequence does not involve application of a phase encoding gradient magnetic field, information required for device position detection can be obtained in a very short time. For example, although it is difficult to capture a three-dimensional MRI image in real time (0.1 seconds or less), according to this embodiment, the magnetic resonance signal projected onto one axis is detected three times (for three axes) The position and shape of the device in vivo can be identified quickly from the position of the marker (in less than 0.1 second). Furthermore, by displaying an MRI image including each marker, and estimating the shape of the device from the position of each marker and superimposing the display, the operator can intuitively confirm the treatment device position and the advancing direction. The treatment device can be manipulated to direct treatment target 402 (FIG. 4). Moreover, while using the device which attached several markers in which each signal variation degree differs as a device, using the three-axis projection nuclear magnetic resonance signal of the subject containing such a device, the position of the device can be accurately performed. It can be detected.

Second Embodiment
In the first embodiment, the marker position is detected directly from the one-dimensional magnetic resonance signal distribution (projected image) in the three axial directions acquired by the device sequence by the imaging unit. However, in this embodiment, the projection of the inactive marker The image is used as a reference image, and the marker position is detected from the difference between the projected image of the active marker and the reference image. "Marker is inactive" means that the effect of the marker does not appear in the image, for example, the image before inserting the device into the subject is the image with the marker inactive, and the device is inserted into the subject The image including the device captured in the state as described above is an image in which the marker is active. When a magnetic field generating coil as shown in FIG. 5 is used as a marker, the state in which the coil is not energized and no magnetic field is generated is inactive, and the state in which the coil is energized to generate a magnetic field is active.

  The procedure of the MRI-guided treatment in this embodiment will be described with reference to FIG. In FIG. 14, the same steps as those in FIG. The procedure of this embodiment is also substantially the same as the procedure shown in FIG. 6, but prior to the device sequence (S104), step S111 of acquiring a one-dimensional projection image (reference image) when the marker is inactive is used. The difference is that prior to the device position calculation (S105), the step of S112 for obtaining the distribution of the signal obtained by subtracting the one-dimensional projection image when the marker is active from the reference image is included.

  In step S111, the same device sequence as in step S104 is executed. At this time, if the vicinity of the treatment target is a site affected by body movement, it is necessary to minimize the influence of body movement with the image to be subtracted (one-dimensional projection image acquired in S104). is there. Step S111 may be performed either before or after the imaging steps S101 and S102 surrounded by a dotted line. When the marker is a magnetic field generating coil, active and inactive can be switched only by switching on and off the magnetic field generating coil. Therefore, by continuously performing steps S111 and S104, the influence of body movement is minimized. Can be limited.

  On the other hand, when the marker is a magnetic substance or a high concentration substance, step S111 and step S104 are sequentially performed because it is necessary to acquire a reference image when the marker is inactive before inserting the device into the body. It is not possible. Here, if the body movement is a body movement caused by respiration, the respiratory movement is periodic, so a plurality of reference images corresponding to the respiratory fluctuation in one cycle are acquired in advance and the storage device (external storage device 61 etc.) Store inside. Then, in step S112, an image whose phase (temporal phase) of body movement matches the one-dimensional projection image acquired in step S104 is selected from the reference images acquired in advance, and the difference is made. This makes it possible to minimize the effects of body movement. In the device position detection step S105, the marker position is detected based on this difference.

  In steps S111 and S104, there is a method of monitoring the fluctuation of the diaphragm as a method of measuring the fluctuation (temporal phase) caused by the respiration. Specifically, an area perpendicular to the diaphragm is irradiated with a pencil beam shaped RF pulse, an additional echo called a navigator echo is acquired to monitor the fluctuation of the diaphragm, and a change due to respiration is measured. One-dimensional projection images can also be used to monitor respiratory variability. Taking an example of abdominal imaging where the influence of respiratory fluctuation is large, as shown in FIG. 15 (a), if the anteroposterior direction (Anterior-Posterio: AP direction) of the body is the y direction, 1 in FIG. 15 (b) Both ends of the two-dimensional projection correspond to the abdominal surface b and the back surface a, respectively. In the periodic breathing fluctuation, as shown by the dotted and solid lines in FIG. 15B, the position (yb2 to yb1) of the abdominal surface also periodically fluctuates, so the shape or edge of the one-dimensional projection image is From the coordinate y, it is possible to identify the phase of respiratory fluctuation. Therefore, it is possible to minimize the influence of body movement by specifying the phase of respiratory fluctuation from the one-dimensional projection image in the AP direction and using the reference image of the corresponding phase. In the case where the marker is a magnetic field generating coil, the body is performed with almost no time difference between step S111 of acquiring a reference image in which the marker is inactive and step S104 of acquiring a one-dimensional projection image in which the marker is active. Although the effect of motion can be minimized as described above, it is needless to say that also in this case, a plurality of reference images corresponding to respiratory fluctuation in one cycle may be obtained in advance.

  FIG. 16 shows the distribution of the signal obtained by subtracting the one-dimensional projection image when the marker is active from the projection image (reference image) when the marker is inactive (difference obtained in step S112 in FIG. 14). It is a figure, (a) is x-axis projection image 1601, (b) is y-axis projection image 1602, (c) has shown z-axis projection image 1603. FIG. Thus, by subtracting the one-dimensional projection image when the marker is active from the one-dimensional projection image when the marker is inactive, it is possible to clearly capture the signal intensity change due to the marker. Also, the type of marker can be accurately determined by the height of the peak. In FIG. 16A, there are two peaks at x = x1 and x = x2, and the peak at x = x2 is larger than the peak at x = x1. Therefore, it can be determined that the x-coordinate of the marker M1 is x1, and the x-coordinate of the marker M2 is x2. Similarly, it can be determined from FIG. 16B that the y-coordinate of the marker M1 is y1 and the y-coordinate of the marker M2 is y2, and the z-coordinate of the marker M1 is z1 and the marker M2 from FIG. It can be determined that the z coordinate is z2. That is, it can be determined that the coordinates of the marker M1 are (x1, y1, z1) and the coordinates of the marker M2 are (x2, y2, z2).

  After the detection of the marker position (S105), as shown in FIGS. 10 to 13, displaying the position superimposed on the tomogram of the subject including the treatment target and the puncture point (S106) is the same as in the first embodiment There are also various forms of display.

  According to the present embodiment, by taking the difference between the image in the inactive state and the image in the active state, the signal change due to the marker can be detected more clearly, and the marker position, ie, the device position is detected. Accuracy can be improved. Also, by obtaining a projection image for each phase of periodic body movement of the subject as a projection image (reference image) in an inactive state, the influence of body movement is minimized when taking a difference. Can improve the accuracy of device position detection. When a magnetic field generating coil is used as a marker of the device, acquisition of a reference image and projection image acquisition in a state in which the marker is active can be performed almost simultaneously (with a time difference of about 0.1 seconds). It is possible to minimize the influence not only on cyclic movements but also on careless movements.

10: imaging unit, 11: static magnetic field generation magnet, 15: sequencer, 20: gradient magnetic field generation unit, 30: RF transmission unit, 34: RF transmission coil, 40: reception unit, 41: RF reception coil, 50: signal processing Unit 51: CPU 51: sequence control unit 52: image reconstruction unit 54: device position detection unit 55: display control unit 63: display device 64: operation unit 100: MRI apparatus 403: treatment Device, 404-406: marker, 501: therapeutic device, 504-506: marker, 100: MRI apparatus.

Claims (16)

An imaging unit that executes a predetermined pulse sequence and collects nuclear magnetic resonance signals generated from a subject; and a signal processing unit that performs computation using the nuclear magnetic resonance signals collected by the imaging unit.
The pulse sequence executed by the imaging unit includes a device sequence for imaging a device inserted inside the subject, and the device sequence is a nucleus projected on one axis for each of three mutually orthogonal axes. Performing the step of acquiring magnetic resonance signals;
The magnetic resonance imaging apparatus, wherein the signal processing unit includes a device position detection unit that detects the position of the device using the three-axis projection nuclear magnetic resonance signal acquired by the device sequence. The magnetic resonance imaging apparatus according to claim 1,
The device comprises markers distinguishable by the magnetic resonance imaging apparatus at a plurality of positions along its longitudinal direction,
The device position detection unit detects the positions of a plurality of the markers from the projected nuclear magnetic resonance signals of the three axes, and calculates the position and the insertion direction of the device based on the positions of the markers. Resonance imaging device. The magnetic resonance imaging apparatus according to claim 1,
The signal processing unit includes an image reconstruction unit that creates an object image using the nuclear magnetic resonance signal, and a device position at which the device position detection unit detects the object image created by the image reconstruction unit. And a display control unit that causes the display device to display information together with the information.
The magnetic resonance imaging apparatus, wherein the display control unit controls a cross section of the subject image to be displayed on the display device using the device position detected by the device position detection unit. The magnetic resonance imaging apparatus according to claim 3,
The magnetic resonance imaging apparatus, wherein the display control unit causes the display device to display a cross section including the device as a cross section of the subject image. The magnetic resonance imaging apparatus according to claim 3,
The magnetic resonance imaging apparatus, wherein the display control unit causes the display device to display a cross section including the tip of the device and intersecting the insertion direction as a cross section of the subject image. The magnetic resonance imaging apparatus according to claim 1,
The device position detection unit is configured to have a reference nuclear magnetic resonance signal acquired by the device sequence in a state where the device does not affect the nuclear magnetic resonance signal and a state in which the device affects the nuclear magnetic resonance signal. A magnetic resonance imaging apparatus, which detects the position of the device using a difference from a nuclear magnetic resonance signal acquired by a device sequence. The magnetic resonance imaging apparatus according to claim 1,
The device position detection unit is configured to compare a reference nuclear magnetic resonance signal previously acquired by the device sequence before inserting the device into the subject, and a nuclear magnetic resonance signal acquired by the device sequence at the time of the device insertion. A magnetic resonance imaging apparatus which detects the device position using a difference. The magnetic resonance imaging apparatus according to claim 7,
The imaging unit executes the device sequence over a plurality of phases of body movement of the subject to acquire a plurality of reference nuclear magnetic resonance signals.
The device position detection unit selects, from among the plurality of reference nuclear magnetic resonance signals, a reference nuclear magnetic resonance signal of a phase identical to that of the nuclear magnetic resonance signal acquired at the time of inserting the device and the phase of body movement. A magnetic resonance imaging apparatus characterized by: A device inserted inside a subject, wherein
Markers detectable by the magnetic resonance imaging apparatus are arranged at a plurality of different positions along the longitudinal direction, and nuclear magnetic resonance signals originating from the respective markers detected by the magnetic resonance imaging apparatus are distinguishable for each marker device. The device according to claim 9, wherein
The device is characterized in that the marker includes a material that locally increases or decreases a nuclear magnetic resonance signal, and the degree of increase or decrease of the nuclear magnetic resonance signal is different for each marker. The device according to claim 9, wherein
The device, wherein the marker comprises a magnetic field generating coil, and the magnitude of the magnetic field generated by the magnetic field generating coil is different for each marker. A device according to any one of claims 9-11, wherein
A device that is any of a catheter, a puncture needle, and a forceps. A method of detecting the position of a device inserted into a subject, comprising:
In the device, markers detectable by a magnetic resonance imaging apparatus are arranged at a plurality of different positions along the longitudinal direction thereof,
After irradiating a non-selective excitation RF pulse by the magnetic resonance imaging apparatus, a readout gradient magnetic field is applied to a first of three orthogonal axes to acquire a nuclear magnetic resonance signal projected on the first axis. Step and
Applying a readout gradient magnetic field to a second axis different from the first axis among the three axes to obtain a nuclear magnetic resonance signal projected on the second axis;
Applying a readout gradient magnetic field to a third axis different from the first and second axes among the three axes to obtain a nuclear magnetic resonance signal projected on the third axis;
Detecting the positions of the plurality of markers using projected nuclear magnetic resonance signals obtained for the first, second and third axes, respectively;
And detecting the position of the device based on the positions of the plurality of markers. The device position detection method according to claim 13, wherein
In the detection of the positions of the plurality of markers, in the state where the markers are not detected in the magnetic resonance imaging apparatus, projected nuclear magnetic resonance signals acquired for each of the three axes are used as reference nuclear magnetic resonance signals, and the device is being inserted Using a difference between the projected nuclear magnetic resonance signal acquired for each of the three axes and the reference nuclear magnetic resonance signal. The device position detection method according to claim 13, wherein
Displaying the detected position of the device together with the image of the subject. An image-guided intervention support device including a device inserted into a subject and a magnetic resonance imaging device, comprising:
In the device, markers detectable by a magnetic resonance imaging apparatus are arranged at a plurality of different positions along the longitudinal direction, and nuclear magnetic resonance signals originating from the respective markers detected by the magnetic resonance imaging apparatus are provided for each marker. A device that can be identified,
The magnetic resonance imaging apparatus executes a predetermined pulse sequence, an imaging unit that collects nuclear magnetic resonance signals generated from a subject, and a signal processing unit that performs an operation using the nuclear magnetic resonance signals collected by the imaging unit. And
The pulse sequence executed by the imaging unit includes a device sequence for imaging a device inserted inside the subject, and the device sequence is a nucleus projected on one axis for each of three mutually orthogonal axes. Performing the step of acquiring magnetic resonance signals;
The signal processing unit causes a display device to display a device position detection unit that detects the position of the device and a detected position of the device using the three-axis projection nuclear magnetic resonance signals acquired by the device sequence. An image-guided intervention support device comprising: a display control unit.

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