JP6912341B2 - Magnetic resonance imaging device, device position detection method using it, and image-guided intervention support device - Google Patents

Description

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

In recent years, attention has been paid to minimally invasive treatment that minimizes the invasion of living organisms. Specifically, puncture treatment that percutaneously punctures a needle-shaped treatment device such as freeze treatment, radio wave treatment, and microwave treatment to treat cancer, biopsy (biopsy) to collect tissue, or There are intravascular treatments typified by catheter treatment, and in treatment using these treatment devices, in order to accurately guide the treatment device (needle or catheter) to the treatment target such as the target tumor tissue in the living body. , Biological images taken in real time using ultrasonic waves or X-rays are used. In addition, MRI, which visualizes internal organs and tissues in detail using static magnetic fields and radio frequency (Radio Frequency: RF) electromagnetic waves, has the advantage of being excellent in visualizing the contrast of living tissues and the therapeutic area (tissue degeneration). Guided treatment is also one of the 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, the gradient magnetic field coil of the MRI apparatus is activated, a signal induced by the induction coil is detected, and the position and orientation of the object are estimated. The technology to be used is disclosed. Further, Patent Document 2 discloses a technique in which three optical markers (bright spots) are attached to a portion of the device that is not inserted into a subject, and the position and inclination of the tip of the device are detected from the positions of the bright spots. .. In Patent Document 3, the guide wire used when inserting the catheter is also used as an RF receiving coil, a three-dimensional image is created using the RF signal detected by the RF receiving coil, and the guide wire is provided on the catheter from the central projection image. A technique for detecting the position and orientation of a marker is disclosed. Further, Non-Patent Document 1 proposes a method of attaching a magnetic material to the tip of a catheter to generate a low signal region on an MR image and detecting the position of a therapeutic device on a three-dimensional MR image.

Japanese Patent Application Laid-Open No. 2011-509109 Patent No. 4377645 Japanese Unexamined Patent Publication No. 2003-24298

F. Settecase et al. "Magnetic Resonance-Guided Passive Catheter Tracking for Endovascular Therapy" Magn Reson Imaging Clin N Am 23, pp. 591-605 (2015)

However, the method described in Patent Document 1 needs to include a signal processing unit in addition to the MRI apparatus in order to process the signal from the magnetic sensor. Since 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 inside the body is constant, the shape changes inside the body. Not compatible with therapeutic devices. Further, since the methods described in Patent Document 3 and Non-Patent Document 1 create a three-dimensional image, there is a limit to the real-time property of position detection. In addition, any of the above-mentioned methods has problems in accuracy and time resolution in detecting the position of the treatment device.

In order to solve the above-mentioned problems of the prior art, the present invention uses a device in which markers that can be detected by an MRI apparatus are provided at a plurality of positions, and uniaxially projected nuclear magnetic resonance signals of a plurality of markers are transmitted in three axes during device insertion. By acquiring about, the marker position is detected in an extremely short time. In particular, the accuracy of position detection can be improved by taking the difference between the case where the marker is not reflected in the nuclear magnetic resonance signal (for example, the device does not exist) and the case where the marker is reflected.

That is, one aspect of the present invention is an MRI apparatus having a device position detection function, an imaging unit that executes a predetermined pulse sequence and collects a nuclear magnetic resonance signal generated from a subject, and an imaging unit that collects the nuclear magnetic resonance signal. The pulse sequence executed by the imaging unit includes a signal processing unit that performs an operation using the nuclear magnetic resonance signal, and includes a device sequence for imaging a device inserted inside the subject. The signal processing unit executes a step of acquiring a nuclear magnetic resonance signal projected on one axis for each of the three axes orthogonal to each other, and the signal processing unit projects the three axes acquired in the device sequence. A device position detecting unit for detecting the position of the device by 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, which is the first of three orthogonal axes after irradiation with a non-selective excitation RF pulse by the magnetic resonance imaging apparatus. A step of applying a read gradient magnetic field to the axis of 1 to acquire a nuclear magnetic resonance signal projected on the first axis, and a read gradient magnetic field on a second axis different from the first axis among the three axes. And the step of acquiring the nuclear magnetic resonance signal projected on the second axis, and the read gradient magnetic field is applied to the third axis different from the first and second axes among the three axes. Then, using the step of acquiring the nuclear magnetic resonance signal projected on the third axis and the projected nuclear magnetic resonance signal acquired for each of the first, second, and third axes, the positions of the plurality of markers can be determined. Includes steps to detect.

A device to which the method for detecting the position of a device of the present invention is applied has markers that can be detected by a magnetic resonance imaging device arranged at a plurality of different positions along the longitudinal direction thereof. That is, the device of the present invention is a device inserted inside a subject, and markers detectable by a magnetic resonance imaging device are arranged at a plurality of different positions along the longitudinal direction thereof, and the magnetic resonance imaging is performed. It is a device in which the nuclear magnetic resonance signal caused by each marker detected by the device can be identified for each marker.
Furthermore, the present invention provides an image-guided intervention support device that combines the above-mentioned device and a magnetic resonance imaging device.

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 projected nuclear magnetic resonance signal. As a result, the accuracy of image-guided intervention can be improved.

The figure which shows the appearance of the MRI apparatus to which this invention is applied. The figure which shows the whole structure of the MRI apparatus. Functional block diagram of the signal processing unit. The figure explaining the MRI guided treatment. The figure which shows an example of the treatment device. The figure which shows the procedure of the MRI-guided treatment of 1st Embodiment. The figure which shows an example of the imaging sequence. The figure which shows an example of the sequence for a device. (A) to (c) are diagrams showing one-dimensional projection images of each axis obtained from the pulse sequence of FIG. The figure which shows an example of the navigation screen in the MRI guided treatment. (A) and (b) are diagrams showing other examples of the navigation screen, respectively. (A) to (c) are diagrams showing still another example of the navigation screen. The figure which shows still another example of a navigation screen. The figure which shows the procedure of the MRI-guided treatment of the 2nd Embodiment. In the second embodiment, the figure for explaining the case where the body movement time phase is detected from the one-dimensional projection image, (a) is a diagram showing the imaging direction, and (b) is the body movement appearing in the one-dimensional projection image in the y direction. The figure which shows. (A) to (c) are diagrams showing the difference between the one-dimensional projection images.

Hereinafter, embodiments of the MRI apparatus of the present invention will be described.
First, the overall configuration of the 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 device is an MRI device provided with a magnet 11 that generates a static magnetic field in the vertical direction, and a subject laid on the 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 a procedure such as surgery, treatment, or examination can directly access the subject 1 placed in the imaging space. Has been done. Therefore, the open MRI apparatus is suitable for interventional MRI in which the procedure is performed in parallel with imaging. However, the present invention is not limited to open MRI.

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

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 method shown in FIG. 1 and substantially parallel to the body axis of the subject. There is a horizontal magnetic field method that generates a magnetic field in various directions. Further, depending on the source of the static magnetic field, there are a permanent magnet method, a normal conduction method, and a superconducting method. In the present embodiment, the method of the static magnetic field generating magnet 11 is not particularly limited.

The gradient magnetic field generating unit drives three sets of gradient magnetic field coils 21 that generate gradient magnetic fields in the three axes of X, Y, and Z, which are the coordinate systems (stationary coordinate systems) of the MRI apparatus, and the gradient magnetic field coils 21, respectively. The gradient magnetic field power supply 22 is provided, and the gradient magnetic field Gx, Gy, and Gz are applied in the three axial directions of X, Y, and Z by driving the gradient magnetic field power supply 22 of each coil according to a command from the sequencer 15. At the time of imaging, a slicing direction gradient magnetic field (Gs) is applied in a direction orthogonal to the slicing surface (imaging cross section) to set the slicing surface with respect to the subject 1, and the rest substantially orthogonal to the slicing surface and orthogonal to each other. A phase encoding direction gradient magnetic field (Gp) and a frequency encoding direction gradient magnetic field (Gf) are applied in the two directions of, and the position information in each direction is encoded in the echo signal.

The RF transmitter 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 biological tissue of the subject 1, and is an RF oscillator 31, a modulator 32, and an RF amplifier 33. And the RF transmission coil 34 on the transmitting side. The RF magnetic field output from the RF oscillator 31 was amplitude-modulated by the modulator 32 at the timing commanded by the sequencer 15, and the amplitude-modulated RF magnetic field was amplified by the RF amplifier 33 and then placed close to the subject. By supplying the RF transmission coil 34, an RF magnetic field is applied to the subject 1.

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

The sequencer 15 is a control means that repeatedly applies an RF magnetic field and a gradient magnetic field in a predetermined pulse sequence, operates under the control of the CPU 51, and issues various commands necessary for data collection of a tomographic image of a subject to the RF transmission unit 30 and It is sent to the gradient magnetic field generator 20.

The receiving unit 40 receives the nuclear magnetic resonance signal emitted by the nuclear magnetic resonance of the nuclear spins of the atoms constituting the biological tissue of the subject 1 as an echo signal, and includes the RF receiving coil 41, the signal amplifier 42, and the signal amplifier 42. It includes a phase detector 43 and an A / D converter 44. The NMR signal of the response of the subject 1 induced by the RF magnetic field emitted from the RF transmission coil 34 of the transmission system is detected by the RF receiving coil 41 arranged close to the subject 1 and amplified by the signal amplifier 42. After that, it is divided into two orthogonal systems of signals by the phase detector 43 at the timing according to the command from the sequencer 15, each of which 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 is composed of 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 a magnetic disk 61 and an optical disk 62, a liquid crystal display, and the like as an accompanying device. It includes 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. Record on a magnetic disk 61 or the like.

The operation unit 64 inputs 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 and a keyboard. The operation unit 64 is arranged 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.

Various pulse sequences, which differ depending on the imaging method, are stored in the signal processing unit 50 as programs in advance. In the present embodiment, in addition to the pulse sequence for imaging the subject, the position of the device inserted in the subject is detected during the intervention procedure in which the device is inserted into the body of the subject for imaging. The pulse sequence (sequence for the device) is stored. The 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 the image. In the intervention procedure, the device sequence is executed, and the device position is calculated or displayed using the signal obtained by executing the device sequence. That is, the signal processing unit 50 of the MRI apparatus functions as an image-guided intervention support apparatus together with the device described later.

FIG. 3 shows an example of the function of the signal processing unit 50 that realizes such a function. As shown in FIG. 3, the signal processing unit 50 is a sequence control unit 51 that controls the execution of the imaging pulse sequence and, if necessary, the sequence for the device, and the Fourier transform on the nuclear magnetic resonance signal collected by the execution of the pulse sequence. The image reconstruction unit 52 that creates an image by performing calculations such as, the device position detection unit 54 that detects the device position using the signal collected by executing the device sequence, and the display image to be displayed on the display device 63 are generated. A display control unit 55 for controlling the display is provided. These functions of the signal processing unit 50 can be realized as software executed by the CPU 51, but a part or all of them may be realized by hardware such as ASIC or FPGA.

Based on the above-described configuration, 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 how the treatment device 403 such as a needle is guided to the treatment target 402 such as a tumor existing inside the human body 401 placed in the imaging space of the MRI apparatus 100. The MRI-guided treatment targets the treatment device 403 by simultaneously displaying the treatment target 402 and the treatment device 403 or the markers 404 to 406 attached to the treatment departure on the MRI image displayed on the display device 63. Induce to 402.

The therapeutic device 403 includes (1) a biopsy needle used for biopsy, (2) a therapeutic needle used for cryotherapy, radiowave therapy, microwave therapy, etc., and (3) a catheter or guide wire used for intravascular therapy. There are various devices that function in vivo, such as devices for intravascular treatment such as (4) gastrointestinal endoscopes, laparoscopes, bronchial endoscopes, and endoscopes such as neuroendoscopes.

This embodiment can be applied to any treatment device, but here, a puncture treatment in which a needle-shaped device is percutaneously punctured to treat cancer will be described as an example. The puncture treatment includes cryotherapy in which the cancer tissue is frozen and treated, radiofrequency treatment and microwave treatment in which the cancer tissue is heated and treated, and laser treatment. In puncture treatment, it is important to accurately guide the tip of the treatment device to the tumor to be treated. 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 has a first marker (M1) 404, a second marker (M2) 405, and a third marker (M3) 406 that serve as markers for the treatment device 403 at a plurality of positions along the longitudinal direction. It is fixed. Each marker is composed of a magnetic material or magnetic field generating coil that locally induces a decrease in signal strength in MRI, or a material that locally induces an increase in signal strength in MRI, such as a vitamin preparation. A marker can be constructed by applying a paint composed of such a material to a device or fixing a member. It is preferable that the markers are distinguishable from each other, such that the change in signal strength, the degree of decrease or the degree of increase differs depending on the marker. As a method for making the change in signal strength identifiable, for example, in the case of a marker made of magnetic paint or a member made of magnetic material, the size or shape is changed, and in the case of a magnetic field generating coil, the magnitude of the generated magnetic field is determined. You can make it different.

FIG. 5 shows an example of a device using the magnetic field generation coil as a marker. The treatment device 501 provided with this marker is a configuration in which the conventional treatment device 502 is provided with the first marker (M1) 503, the second marker (M2) 504, and the third marker (M3) 505. These markers consist of coils wound around the device at predetermined intervals d along the longitudinal direction of the treatment device 502. The interval d is not particularly limited, but is preferably a distance at which each marker can be identified, for example, 10 mm or more. Even if the device is bent, it is preferable that the distance in which the direction of the device can be estimated from the distance between them is, for example, 100 mm or less. 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, each of which is connected in series. Since each of these coils has a different self-inductance, the magnetic field generated by each coil when a current is applied to these coils is different. That is, since each marker locally induces a decrease in signal strength in MRI and the degree thereof varies from marker to marker, the position of each marker can be specified.

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

First, the subject is placed in the 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. The conditions and parameters required for imaging are set after acquiring a positioning image with low spatial resolution when positioning the subject 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 the device, the sequence control unit 51 executes a preset imaging sequence and starts imaging (S101, S102). .. The imaging sequence is not particularly limited, but when it is expected that multiple imagings will be repeated as in intervention MRI, a pulse sequence with a short measurement time, a gradient echo (GrE) system as shown in FIG. 7 The pulse sequence is selected. That is, after applying the RF pulse 701 and the slice selection gradient magnetic field 702 to excite a predetermined region (slice) of the subject, the phase encode gradient magnetic field 703 is applied and the read gradient gradient magnetic field 704 is applied, and the RF pulse is applied. The echo signal 705 is measured after a predetermined echo time TE after the application of 701. The series of sequences described above is repeated at a predetermined repetition time TR, and the number of echo signals required for image reconstruction is measured. Although FIG. 7 shows a two-dimensional GrE pulse sequence, it may be three-dimensional.

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

After starting the insertion of the device, when the device position detection instruction is received via the operation unit 64 (S103), the sequence control unit 51 executes the device sequence (S104). As shown in FIG. 8, the device sequence is for applying the non-selective RF pulse 801 and measuring the echo signal 803 with the read gradient magnetic field 802 of one axis for each of the three orthogonal axes. It is an extremely short sequence of several tens of milliseconds until the echo signal measurement. 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 lead-out gradient magnetic field 802a in the x direction. The image reconstruction unit 52 Fourier transforms the echo signal 803a to obtain a one-dimensional magnetic resonance signal distribution (one-dimensional projected image) projected on the x-axis. Similarly, the entire region of interest is excited by irradiating the RF pulse 801b, the echo signal 803b is measured by the lead-out gradient magnetic field 802b in the y direction, Fourier transformed, and the one-dimensional magnetic resonance signal projected on the y-axis. Get the distribution. Further, the entire region of interest is excited by irradiating the RF pulse 801c, the echo signal 803c is measured by the lead-out gradient magnetic field 802c in the z direction, Fourier transformed, and the one-dimensional magnetic resonance signal distribution projected on the z-axis. To 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 the position and the vertical axis is the signal strength. In this example, the marker shows a case where two markers M1 and M2 for locally reducing the signal intensity are provided, and the degree of signal reduction is assumed that the marker M2 is larger than the marker M1. FIG. 9A is a one-dimensional magnetic resonance signal distribution 901 projected on the x-axis, where it is projected on the x-axis at the coordinates x1 where the marker M1 exists and the coordinates x2 where the marker M2 exists. The one-dimensional magnetic resonance signal is locally reduced. Further, the degree of signal reduction is larger in x2 than in x1. Therefore, from the distribution of the one-dimensional magnetic resonance signal projected on 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. Further, the one-dimensional magnetic resonance signal distribution 902 (FIG. 9 (b)) projected on the y-axis and the one-dimensional magnetic resonance signal distribution 903 (FIG. 9 (b)) projected on the z-axis shown in FIG. 9 (c). From c)), 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, as in the case of FIG. 9A. Can be determined to be. 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 the markers M1 and M2 can be calculated, and the angle of this line can be regarded as the traveling direction of the device in a pseudo manner.

In the example of FIG. 9, a case where a marker that locally induces a decrease in signal strength is used in MRI is shown, but in the case of a marker that locally induces an increase in signal strength, the signal is locally localized. The position of the marker can be detected from the increase.

The device position detection unit 54 detects the positions of the markers appearing in the one-dimensional projection images of these three axes, and calculates the orientation (traveling direction) of the device using the positions of the plurality of markers (S105). If the device is made of a material that does not deform or hardly deforms, the device tip position and orientation can be calculated from the geometry of the device itself. When the device is bendable and deformable, each marker can be identified (the degree of change in signal strength differs depending on the marker), so that each marker can be identified on the projection data. The position and direction can be calculated.

The display control unit 55 receives the device position from the device position calculation unit 54, and displays the device position superimposed on the image of the subject reconstructed by the image reconstruction unit 52 (S106). As the subject image displaying the device position, there are various modes such as a tomographic image and a projection image obtained by processing 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 positions 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 acquired three-dimensional subject image, and the cross section thereof. The marker positions are superimposed and displayed on the image with black circles 1004 to 1006.

The image 1000 may be an image of a cross section including the insertion position (puncture point) S of the device and, for example, the first marker M1904, or an image obtained by performing MIP processing or the like as shown in FIG. 11A. In addition to displaying the marker position, the line connecting the markers is displayed as the device shape 1003, or as shown in FIG. 11B, an extension line of the line 1003 indicating the device is shown to display the traveling direction of the device. You may. This allows the surgeon to intuitively know whether the device is heading towards or off the treatment target 1002. In the case of the cross-sectional image of FIG. 10, not all marker positions are necessarily included in the cross section, but the marker positions are projected onto the cross section of the image 1000 and displayed, and the black circles are displayed according to the distance from the cross section of the marker positions. Brightness differences 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, Sattital) 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 a MIP image of a plane passing through the marker M1 provided at the tip of the device and orthogonal to the traveling direction of the device is displayed, and an image obtained by projecting the treatment target 1002 on the plane and the position of the tip of the device are displayed. May be superimposed and displayed. As the device traveling direction, for example, the direction of the line connecting the two markers M1 and M2 is set as the device traveling direction. The images of the various aspects described above may be displayed individually or in combination as appropriate and displayed in parallel.

While checking such a navigation screen (image 900), the operator determines whether to advance the device further (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 to perform position detection by an instruction via the operation unit 64. For example, when the device tip position approaches the target portion, it is automatically determined. The device position superimposed on the display image may be updated with the newly acquired position information by repeating at intervals.

Further, although not shown in FIG. 6, after the device reaches the target position, for example, when performing biopsy, freezing, or hyperthermia using the device, imaging is performed before and after the start to confirm the therapeutic effect. It is also possible to do.

According to the present embodiment, a device having a plurality of positions in the longitudinal direction with markers that can be identified by MRI is used, and when detecting the position of the device inserted inside the subject, the imaging unit is aligned with one axis. Imaging is performed by a device sequence that executes the step of acquiring the projected nuclear magnetic resonance signal for three axes orthogonal to each other, and the arithmetic unit uses the three-axis projected nuclear magnetic resonance signal acquired in the device sequence to perform imaging. Detect the location of the device. Since the device sequence does not involve the application of a phase-encoded gradient magnetic field, the information required for device position detection can be obtained in an extremely short time. For example, it is difficult to capture a three-dimensional MRI image in real time (0.1 seconds or less), but according to this embodiment, the magnetic resonance signal projected on one axis is detected three times (for three axes). Then, the position and shape of the device in the living body can be specified from the position of the marker at high speed (in 0.1 seconds or less). Furthermore, by displaying an MRI image including each marker and further estimating the shape of the device from the position of each marker and superimposing it, the operator can intuitively confirm the position of the treatment device and the direction of travel. The treatment device can be manipulated to guide to the treatment target 402 (FIG. 4). In addition, as a device, a device with a plurality of markers having different degrees of signal change is used, and by using a three-axis projected nuclear magnetic resonance signal of the subject including such a device, the position of the device can be accurately determined. Can be detected.

<Second embodiment>
In the first embodiment, the imaging unit directly detects the marker position from the one-dimensional magnetic resonance signal distribution (projected image) in the three-axis direction acquired by the device sequence, but in the present embodiment, the marker is an inactive projection. The image is used as a reference image, and the marker position is detected from the difference between the projected image in which the marker is active 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 an image in which the marker is inactive and the device is inserted into the subject. The image including the device captured in this state is an image in which the marker is active. When the magnetic field generating coil as shown in FIG. 5 is used as a marker, the state in which the coil is not energized and the magnetic field is not generated is inactive, and the state in which the coil is energized and the magnetic field is generated is active.

The procedure for MRI-guided treatment in this embodiment will be described with reference to FIG. In FIG. 14, the same procedure as in FIG. 6 is indicated by the same reference numerals, and redundant description will be omitted. The procedure of this embodiment is almost the same as the procedure shown in FIG. 6, but the step S111 of acquiring the one-dimensional projection image (reference image) when the marker is inactive is performed prior to the device sequence (S104). It is different in that it includes step S112 to obtain the distribution of the signal obtained by subtracting the one-dimensional projection image when the marker is active from the reference image prior to the device position calculation (S105).

In step S111, the same device sequence as in S104 is executed. At this time, if the vicinity of the treatment target is a part affected by body movement, it is necessary to minimize the influence of body movement with the difference image (one-dimensional projection image acquired in S104). be. Step S111 may be executed before or after the imaging steps S101 and S102 surrounded by the dotted line. When the marker is a magnetic field generating coil, it is possible to switch between active and inactive simply by switching the magnetic field generating coil on and off. Therefore, by performing step S111 and step S104 in succession, 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, the reference image when the marker is inactive needs to be acquired before inserting the device into the body, so step S111 and step S104 are continuously performed. It is not possible. Here, when the body movement is caused by respiration, since the respiration movement is periodic, a plurality of reference images corresponding to the respiration fluctuation within one cycle are acquired in advance and a storage device (external storage device 61, etc.). Store in. Then, in step S112, among the reference images acquired in advance, an image whose body movement phase (time phase) matches the one-dimensional projection image acquired in step S104 is selected and differentiated. As a result, the influence of body movement can be minimized. 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 (time phase) caused by respiration. Specifically, the region orthogonal to the diaphragm is irradiated with a pencil beam-shaped RF pulse, and an additional echo called a navigator echo is acquired to monitor the fluctuation of the diaphragm and measure the fluctuation caused by respiration. Respiratory variability can also be monitored using a one-dimensional projected image. Taking abdominal imaging, which is greatly affected by respiratory fluctuations, as an example, as shown in FIG. 15 (a), if the anterior-posterior direction (Antial-Poster: AP direction) of the body is the y direction, 1 in FIG. 15 (b). Both ends of the dimensional projection image correspond to the abdominal surface b and the back surface a, respectively. In the periodic respiratory fluctuation, as shown by the dotted line and the solid line in FIG. 15B, the position of the abdominal surface (yb2 to yb1) also changes periodically, so that the shape of the one-dimensional projected image or the end portion The time phase of respiratory fluctuation can be specified from the coordinate y. Therefore, by identifying the time phase of respiratory fluctuation from the one-dimensional projection image in the AP direction and using the reference image of the corresponding time phase, the influence of body movement can be minimized. When the marker is a magnetic field generation coil, the body is formed by executing step S111 for acquiring a reference image in which the marker is inactive and step S104 for acquiring a one-dimensional projection image in which the marker is active with almost no time difference. As described above, the influence of motion can be minimized, but it goes without saying that in this case as well, a plurality of reference images corresponding to respiratory fluctuations within one cycle may be obtained in advance.

FIG. 16 shows a signal distribution (difference obtained in step S112 of FIG. 14) obtained by subtracting the one-dimensional projected image when the marker is active from the projected image (reference image) when the marker is inactive. In the figure, (a) shows an x-axis projection image 1601, (b) shows a y-axis projection image 1602, and (c) shows a z-axis projection image 1603. In this way, by subtracting the one-dimensional projection image when the marker is active from the one-dimensional projection image when the marker is inactive, the change in signal intensity due to the marker can be clearly captured. In addition, the type of marker can be accurately determined from 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 from FIG. 16C, the z-coordinate of the marker M1 is z1 and the marker M2. 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 marker position is detected (S105), as shown in FIGS. 10 to 13, displaying the position on the tomographic image of the subject including the treatment target and the puncture point (S106) is the same as in the first embodiment. There are various forms of display.

According to the present embodiment, by taking the difference between the image in which the marker is inactive and the image in which the marker is active, the signal change due to the marker can be detected more clearly, and the marker position, that is, the device position can be detected. The accuracy can be improved. In addition, by acquiring a projection image for each time phase of the periodic body movement of the subject as a projection image (reference image) in the inactive state, the influence of the body movement when taking a difference is minimized. It is possible to improve the accuracy of device position detection. Further, when the magnetic field generation coil is used as the marker of the device, the acquisition of the reference image and the acquisition of the projected image in the active state of the marker can be performed almost at the same time (with a time difference of about 0.1 second). The effect of not only periodic body movements but also careless body movements can be minimized.

10: Imaging unit, 11: Static magnetic field generating magnet, 15: Sequencer, 20: Diagonal magnetic field generating unit, 30: RF transmitting unit, 34: RF transmitting coil, 40: Receiving unit, 41: RF receiving 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 device, 403: Treatment Devices, 404-406: markers, 501: therapeutic devices, 504-506: markers, 100: MRI devices.

Claims (15)

It is provided with an imaging unit that executes a predetermined pulse sequence and collects a nuclear magnetic resonance signal generated from a subject, and a signal processing unit that performs an operation using the nuclear magnetic resonance signal 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 includes the nuclear magnetic resonance signal at a plurality of different positions along the longitudinal direction thereof. A device in which markers that induce a local decrease or increase in the signal strength of the above are arranged, and the increase or decrease of the nuclear magnetic resonance signal caused by each marker can be identified for each marker.
The device sequence executes a step of acquiring a nuclear magnetic resonance signal projected onto one axis for each of the three axes orthogonal to each other.
The signal processing unit is a magnetic resonance imaging apparatus including a device position detection unit that detects the position of the device by using a three-axis projected nuclear magnetic resonance signal acquired in the device sequence. The magnetic resonance imaging apparatus according to claim 1.
The marker includes a material that locally increases or decreases the nuclear magnetic resonance signal, and the magnetic resonance imaging apparatus is characterized in that the degree of increase or decrease of the nuclear magnetic resonance signal is different for each marker. The magnetic resonance imaging apparatus according to claim 1.
The marker is a magnetic resonance imaging apparatus comprising a magnetic field generating coil, wherein the magnitude of the magnetic field generated by the magnetic field generating coil is different for each marker. The magnetic resonance imaging apparatus according to claim 1.
The device is a magnetic resonance imaging device that is either a catheter, a puncture needle, or forceps. The magnetic resonance imaging apparatus according to claim 1.
The device position detecting 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 has an image reconstruction unit that creates a subject image using the nuclear magnetic resonance signal, and a device position that the device position detection unit detects the subject image created by the image reconstruction unit. It also has a display control unit that displays information on the display device.
The display control unit is a magnetic resonance imaging device that controls a cross section of the subject image to be displayed on the display device by using the device position detected by the device position detection unit. The magnetic resonance imaging apparatus according to claim 6.
The display control unit is a magnetic resonance imaging device characterized in that the display device displays a cross section including the device as a cross section of the subject image. The magnetic resonance imaging apparatus according to claim 6.
The display control unit is a magnetic resonance imaging device that displays, as a cross section of the subject image, a cross section including the tip of the device and intersecting in the insertion direction on the display device. The magnetic resonance imaging apparatus according to claim 1.
The device position detection unit has the 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 the device in a state where the device has an influence on the nuclear magnetic resonance signal. A magnetic resonance imaging apparatus characterized in that the device position is detected by 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 includes a reference nuclear magnetic resonance signal acquired in advance by the device sequence before inserting the device into the subject, and a nuclear magnetic resonance signal acquired by the device sequence when the device is inserted. A magnetic resonance imaging apparatus characterized in that the device position is detected using a difference. The magnetic resonance imaging apparatus according to claim 10.
The imaging unit executes the device sequence over a plurality of time phases of the body movement of the subject to acquire a plurality of reference nuclear magnetic resonance signals.
The device position detection unit selects a reference nuclear magnetic resonance signal having the same time phase as the nuclear magnetic resonance signal acquired at the time of inserting the device from the plurality of reference nuclear magnetic resonance signals, and the difference. A magnetic resonance imaging apparatus characterized in that A method of detecting the position of a device inserted in a subject.
The device has markers arranged at a plurality of different positions along its longitudinal direction to induce a local decrease or increase in the signal intensity of the nuclear magnetic resonance signal received by the magnetic resonance imaging apparatus, and the nucleus resulting from each marker. It is a device that can identify the increase or decrease of the magnetic resonance signal for each marker.
After irradiating a non-selective excitation RF pulse with the magnetic resonance imaging device, a read gradient magnetic field is applied to the first of the three orthogonal axes to acquire a nuclear magnetic resonance signal projected on the first axis. Steps and
A step of applying a read gradient magnetic field to a second axis different from the first axis of the three axes to acquire a nuclear magnetic resonance signal projected on the second axis.
A step of applying a read gradient magnetic field to a third axis different from the first and second axes among the three axes to acquire a nuclear magnetic resonance signal projected on the third axis.
Includes a step of detecting the position of the plurality of markers using the projected nuclear magnetic resonance signals obtained for the first, second and third axes, respectively.
A device position detection method comprising detecting the position of the device based on the positions of the plurality of markers. The device position detection method according to claim 12.
In the detection of the positions of the plurality of markers, the projected nuclear magnetic resonance signal acquired for each of the three axes while the marker is not detected in the magnetic resonance imaging apparatus is used as a reference nuclear magnetic resonance signal, and the device is being inserted. A device position detection method, characterized in that the difference between the projected nuclear magnetic resonance signal and the reference nuclear magnetic resonance signal acquired for each of the three axes is used. The device position detection method according to claim 12.
A device position detection method further comprising a step of displaying the detected position of the device together with an image of the subject. An image-guided intervention support device that includes a device inserted into a subject and a magnetic resonance imaging device.
The device has markers arranged at a plurality of different positions along its longitudinal direction to induce a local decrease or increase in the signal intensity of the nuclear magnetic resonance signal received by the magnetic resonance imaging apparatus, resulting from each marker. It is a device that can identify the increase or decrease of the nuclear magnetic resonance signal for each marker.
The magnetic resonance imaging apparatus has an imaging unit that executes a predetermined pulse sequence and collects a nuclear magnetic resonance signal generated from a subject, and a signal processing unit that performs an operation using the nuclear magnetic resonance signal collected by the imaging unit. And with
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 onto one axis for each of three axes orthogonal to each other. It performs the steps of acquiring a magnetic resonance signal.
The signal processing unit uses the three-axis projected nuclear magnetic resonance signal acquired in the device sequence to display the device position detection unit that detects the position of the device and the detected position of the device on the display device. The device position detection unit includes a display control unit, and the device position detection unit includes 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 the device for the nuclear magnetic resonance signal. An image-guided intervention support device characterized in that the device position is detected by using the difference from the nuclear magnetic resonance signal acquired by the device sequence under the influence of.

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