JP2001170022A - Magnetic resonance imaging instrument - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an MRI instrument capable of diagnostic imaging necessary for the low invasive thermotherapy while monitoring the temperature of a part to be treated. SOLUTION: A control system of the MRI apparatus images figures and control for measuring the temperature at the same time. A figural or functional MRI image and data expressing the temperature at a specific part are displayed on a display screen alternately or at the same time. Therefore, an operator can observe the process of the therapy while monitoring the temperature.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic resonance imaging (hereinafter referred to as "MRI") apparatus, and more particularly to an MRI apparatus suitable for an interventional system for performing a process while monitoring the temperature of the body.

[0002]

2. Description of the Related Art In recent years, attention has been paid to a treatment method that achieves the same effect in a minimally invasive manner, rather than a treatment by a surgical operation of putting a scalpel into a patient. For example, it is a treatment method in which a needle is inserted percutaneously under X-ray fluoroscopy, and the affected area of the herniated disc is transpired by laser irradiation. Similarly, there is a cryosurgery treatment in which the affected part is cryoablated by pouring a cryogen under X-ray fluoroscopy. These minimally invasive treatments under X-ray fluoroscopy are called interventional treatments and have begun to spread because their therapeutic effects are satisfactory.

[0003] Alternatively, a hyperthermia treatment method, which irradiates an affected part with electromagnetic waves or infrared rays to raise the temperature of a part of body tissue and selectively kills tumor cells that are considered to be weak to heat, has also attracted attention. .

[0004]

Since the above-mentioned interventional treatment is performed under X-ray fluoroscopy, there is a problem in that the operator and the patient are exposed to X-rays. In addition, there is a problem that it is not possible to evaluate during the operation how much the transpiration or excision of the affected part has been performed, and it is not possible to grasp a temperature change of normal tissue around the affected part.

In addition, hyperthermia therapy requires extremely precise control of the boundary temperature between the death of normal cells and tumor cells. However, there is no means for non-invasively accurately measuring the temperature and temperature distribution in the body during treatment.

On the other hand, there have been developed several methods for measuring the temperature in the body from the nuclear magnetic resonance (hereinafter referred to as NMR) signal of the body tissue by MRI. The main method is
1) The change time of the NMR signal changes depending on the temperature, and the temperature is calculated from the change amount. 2) The change of the resonance frequency of the NMR signal is measured with the temperature change, and the temperature is calculated from the change frequency and the amount of phase change. 3) There is a method of measuring the diffusion constant depending on the temperature of the NMR signal to obtain the temperature (Japanese Patent Publication No. 6-14911).

However, in the above-mentioned interventional treatment, the measurement of the temperature change at the treatment site must be performed together with the monitoring of the morphology. However, the morphology cannot be described with high spatial resolution by the above-described temperature measurement. These temperature measurements have not been applied to monitor the progress of treatments such as therapy. As an image display means, there has been no MRI apparatus capable of displaying a combination of an MRI image indicating a form and a function and a temperature distribution diagram or a temperature display of an inspection site.

The present invention has been made in view of the above problems, and has as its object to provide an MRI apparatus suitable for performing interventional treatment while monitoring the temperature of a treatment site under MRI imaging. Another object of the present invention is to provide an MRI apparatus capable of substantially displaying a tomographic image and temperature information for judging the progress of a treatment procedure. Further, the present invention provides an MR that can provide information indicating the temperature of a treatment site in a form that can be easily used by a person who performs treatment.
The purpose is to provide I equipment.

[0009]

To achieve the above object, an MRI apparatus according to the present invention comprises: a static magnetic field generating means for generating a constant magnetic field intensity; a gradient magnetic field generating means for generating a magnetic field intensity gradient;
Means for generating a high-frequency magnetic field, means for detecting an NMR signal from the subject, calculation / display means for reconstructing a tomographic image of the subject using the NMR signal and displaying the result, and each of these means Control means for controlling, wherein the calculation / display means calculates an image indicating a numerical value or a temperature distribution indicating a temperature change of the inspection part of the subject, and the calculated temperature information and the tomographic image alternately or simultaneously. Display means.

In the present invention, the term "temperature information" means all information relating to temperature, such as a numerical value indicating a temperature change, a temperature distribution image, a graph obtained by processing a numerical value indicating a temperature change, and an isothermal line.

In a preferred embodiment of the present invention, the control means controls the measurement of the NMR signal for temperature measurement while measuring the NMR signal for the tomographic image of the subject, and converts the NMR signal for the tomographic image. The reconstructed tomographic image and temperature information obtained by calculating the NMR signal for temperature measurement are displayed simultaneously or alternately.

In another preferred embodiment of the present invention, the control means creates signal intensity data for a tomographic image and phase data for calculating temperature information using the NMR signal obtained from the subject, and The reconstructed tomographic image and the temperature information calculated from the phase data are displayed simultaneously or alternately.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an overall configuration diagram of an MRI apparatus to which the present invention is applied. The MRI apparatus shown in FIG. 1 includes a static magnetic field generating magnet 2,
A gradient magnetic field generation system composed of a gradient magnetic field coil 3 and a gradient magnetic field power supply 4; a high frequency magnetic field generation system composed of a high frequency coil 5 and a high frequency power amplifier 6; a detection coil 7 for detecting an NMR signal; Device 8 (signal processing system), a sequencer 9 (control system) for controlling the gradient magnetic field generation system and the high-frequency magnetic field generation system according to a predetermined imaging sequence, and a computer 1
The control system includes an arithmetic processing system including the storage device 11 and the first display 12, an operation system including the first display 12, the second display 13, and the console 14, and a table 15 for transporting the subject 1.

Some units are installed in an electromagnetic shield room 16 so that external electromagnetic noise does not enter the detection coil 7. For this reason, the unit inside the shield room and the external unit are connected via the filter circuit 17.

The static magnetic field generating magnet 2 generates a uniform and stable magnetic field intensity in the space including the examination site of the subject 1. As a means for generating a magnetic field, there are a permanent magnet, a normal conducting coil and a superconducting coil system.In the apparatus shown in FIG. 1, a pair of opposed superconducting coils 18 and an iron yoke which constitutes a magnetic circuit so as to surround the superconducting coils 18 Assembled in 19 With such a configuration, the subject 1 of the static magnetic field generating magnet 2
Can secure a wide space, and the operator can directly perform a treatment such as treatment on the subject 1 disposed in the magnet 2. The spherical space including the inspection site of the subject 1 is adjusted to a uniformity of, for example, 3 ppm or less. The performance of this magnet enables the imaging function of MR fluoroscopy and Echo Planar Imaging (EPI) for taking MRI images in real time.

The static magnetic field generating magnet 2 may be of an open type having a structure in which a pair of permanent magnets are arranged vertically. In this case, since the surroundings of the subject are open, treatment such as treatment can be performed more easily.

The gradient magnetic field generating system has x,
Gradient magnetic field coil 3 wound so as to change the magnetic flux density in the three axial directions of y and z (x, y, and z are shown integrally in the figure)
And a gradient magnetic field power supply 4 for driving the respective gradient magnetic field coils 3 of x, y, and z. The gradient magnetic field power supply 4 is driven according to a control signal from a sequencer 9 to be described later to change a current value flowing through the gradient magnetic field coil 3 so that gradient magnetic field pulses Gx, Gy, and Gz composed of three axes can be inspected in the subject 1 To be applied. This gradient magnetic field is used to grasp the spatial distribution of the NMR signal obtained from the inspection site described later.

The high-frequency magnetic field system includes a high-frequency coil 5 for generating a high-frequency magnetic field for exciting the nuclei at the examination site of the subject 1 for resonance, and a high-frequency power amplifier 6 for supplying a high-frequency current to the high-frequency coil 5. I have. High frequency power amplifier 6
Is also controlled by the control signal of the sequencer 9. The operating frequency of the high-frequency power amplifier 6 is set to the resonance frequency of the inspection target nucleus determined by the magnetic field strength of the device. The inspected nucleus is usually hydrogen.

The detection coil 7 has a function of detecting, as an electric signal, an NMR signal which is a high-frequency magnetic field of the excited hydrogen nucleus in the examination site of the subject 1. This detection coil 7
The space is provided to allow simultaneous treatment during MRI examination. The receiver 8 amplifies and detects the weak NMR signal detected by the detection coil 7, and then a computer 10
Analog / digital conversion to digital signals that can be processed by
It has the function of digital conversion. Receiver 8 is also sequencer 9
The operation timing of the NMR signal is controlled, and the NMR signal converted into a digital signal is connected to the computer 10.

The arithmetic processing system comprises a computer 10, a storage device 11 for storing images and the like, a first display 12 for displaying processed data, a second display 13, and a console 14 for operating the MRI apparatus. I have. Here, the second display is arranged near the magnet 2 so that the operator (not shown in the figure) can check the display content during treatment such as treatment.
The computer 10 processes the NMR signal of the inspection site of the subject 1 and obtains the temperature of the inspection site based on not only the anatomical tomographic image of the inspection site but also the frequency and phase displacement of the NMR signal and the amount of change in relaxation time. Is calculated, the first display 12 and the second display 13
To be displayed.

The computer 10 is connected to the sequencer 9 for controlling the operation of each unit described above, and sends commands necessary for control to the sequencer 9.

In the MRI apparatus of the present invention, the control system including the computer 10 and the sequencer 9 performs the following control. 1) Measure and display continuous morphological or functional images, measure the temperature at desired intervals, and simultaneously display morphological or functional images and temperature information (numerical values, phase images, etc.). Alternatively, continuous temperature measurement and monitoring are performed, and morphological measurement is performed at desired intervals during that time, and temperature information and a morphological image are simultaneously displayed. 2) Using NMR signals obtained by continuous measurement,
Create morphological or functional images in parallel with temperature information,
indicate.

These functions are implemented on a computer as a program.
In accordance with this program, the computer 10 performs calculations such as image reconstruction and temperature calculation using the obtained NMR signals. Selection of functions, setting of a sequencer executed in each function, photographing conditions, display conditions, and the like can be performed through the console 14.

FIG. 2 shows the configuration of the image display portion of the computer 10 that enables simultaneous display of temperature information and morphological images. The image memory 202 and the graphic memory 203 are memories for storing image data and character / numerical data processed by the arithmetic unit. Data is sent to these memories sent via the data bus 201 and written. The image data is data of a tomographic image or a phase image created by Fourier-transforming an NMR signal, and the character / numerical data is a temperature numerical value, a temperature distribution contour, a temperature change graph, and the like.

The data in the image memory 202 is input to the look-up table memory 205 for each image. The data in the graphic memory 203 is input to the table memory 206 for each display unit.

The control circuit 204 sends control signals 209 and 210 relating to the display of these data to the look-up table memory 205 and the table memory 206, respectively. That is,
When the density and gradation of the displayed image are set by the operator's operation, a signal 209 for these processes is sent from the control circuit 204 to the look-up table memory 205.
, Where processing relating to density and gradation is performed. Further, display / non-display of temperature information is selected by a signal 210 from the control circuit 204.

The signals of the look-up table memory 205 and the table memory 206 are added by the synthesizing circuit 207, converted into a video signal by the D / A circuit 208, and input to the first display 12 and the second display 13.

Next, the operation of the MRI apparatus having such a configuration will be described.

FIG. 3 is a flowchart showing an example of a process of performing interventional treatment for treating an affected part while monitoring the temperature of the examination site by using the MRI apparatus shown in FIG. FIG. 4 shows images displayed on the first display and the second display.

First, an examination site of the subject 1, for example, N
The high-frequency coil 7 for detecting the MR signal is mounted and disposed at the center of the magnet 2 (step 301).

Next, a tomographic image is taken along the body axis of the torso as the examination site (step 302). This is, for example, a preliminary measurement for determining a section including a route of a needle and a treatment site, and is performed by a known sequence such as a spin echo method. The captured image 401 is the first image as shown in FIG.
The information is displayed on the display 12 and the second display 13.

The operator specifies a new tomographic plane B including the treatment site based on the displayed image 401 (step 303), and captures an image of the new tomographic plane by the high-speed imaging method (step 30).
Four). This operation is repeated continuously. As the high-speed imaging method, for example, MR fluoroscopy described later is selected.

The image obtained by the continuous photographing is
The information is displayed on the first display 12 and the second display 13. This allows the surgeon to perform biopsy in virtually real time.
The operation of (percutaneous cord) can be performed while observing the image 402.

When it is confirmed from the image 402 that the needle has reached the treatment site, transpiration treatment of the affected part by laser irradiation is performed (step 305). The process of this treatment is confirmed by continuously taking morphological images and displaying them on the first display 12 and the second display 13 (step 306). In this case, a functional image may be taken as needed and displayed. Alternatively, imaging may be performed by changing imaging conditions such as changing the field of view of an image in order to image a treatment site with high resolution. By performing the imaging and the display continuously and repeatedly as described above, a substantially real-time image is provided to the operator.

In the course of such continuous photographing, the temperature of the inspection site is monitored at regular intervals. The time interval of the temperature monitor is set by the operator inputting the value of the time interval suitable for monitoring the temperature to the computer 10 according to the treatment. The value of this time interval can be changed according to the course of treatment. That is, even during treatment,
The monitoring interval can be changed by input from 10.

In the temperature monitor, first, it is determined whether or not a predetermined time has elapsed from the start of the transpiration treatment (step 30).
7). After a certain period of time, the computer 10 instructs the sequencer to execute a temperature measurement sequence. The temperature measurement sequence may be the same as or different from the sequence according to the high-speed imaging method executed in steps 304 and 306.

By executing the temperature measurement sequence, the NMR signals of the surrounding tissues including the treatment site are measured (step 3).
08). The NMR signal measured here is a signal that includes a temperature change as a phase change, and the computer 10 can process the NMR signal to calculate a temperature and configure a temperature distribution chart. The calculation of the temperature change will be described later. The temperature information (temperature change or temperature distribution diagram as a numerical value) thus obtained is displayed on the first display 12 and the second display 13.

Whether the temperature information is displayed alternately with the tomographic image 403 as necessary, or is displayed repeatedly at a constant cycle,
Display of temperature or temperature distribution, for example, as shown in FIG.
405 is displayed as a part of the tomographic image 404.

Such temperature measurement is performed at intervals set in the course of treatment, and each time, the temperature information is updated and displayed on the first display 12 and the second display 13 (steps 306 to 308). .

After confirming the progress of the treatment on the tomographic image, the examination and treatment are terminated, and the subject is removed from the magnet 2 and terminated (steps 309 and 310).

With the above-described configuration, the operator can always observe the progress of the treatment with MRI images during the treatment and can monitor the temperature change relating to the treatment at regular intervals.

Next, steps 304 (306) and step
The photographing sequence of 308 will be described.

As described above, in step 304, continuous high-speed imaging such as MR fluoroscopy is performed. FIG. 5 is a diagram showing a sequence using a gradient echo as an example of the high-speed imaging method, and FIG. 6 is a diagram for explaining MR fluoroscopy.

The sequence by the gradient echo is
Although well-known as a sequence applied to MR fluoroscopy, in brief, in order to selectively excite nuclear spins on a tomographic plane orthogonal to the body axis, a slice selection gradient magnetic field pulse ( Here, a high-frequency pulse 502 is applied while a y-axis gradient magnetic field pulse) 501 is applied.
Is passed through the high-frequency coil 5. Next, a phase encode gradient magnetic field pulse (here, a z-axis gradient magnetic field pulse) 503 is applied, and the phase of the precession of the excited nuclear spin is encoded along the z-axis. Further, while the readout gradient magnetic field pulse (x-axis gradient magnetic field pulse) 504 is applied, the receiving coil 7 detects the precession of the nuclear spin as an NMR signal. The received NMR signal is converted into, for example, 256 digital signals by the receiver 8 and recorded in the memory of the computer 10.

The detection of such an NMR signal is repeated while changing the intensity of the z-axis gradient magnetic field pulse 503. The intensity of the z-axis gradient magnetic field pulse 503 is repeated, for example, from the first value to the 128th value, thereby collecting data necessary for reconstructing one tomographic image.

In the figure, a gradient magnetic field pulse 506 on the y-axis and a gradient magnetic field pulse 507 on the x-axis are used for forcibly relaxing the residual component of the precession of the nuclear spin in the immediately preceding measurement in repeated measurement. . Also, the y-axis gradient magnetic field pulse 508 and the x-axis gradient magnetic field pulse 509 cancel out the phase shift in the y-axis direction and the x-axis direction of the precession of the nuclear spin described above so that it can be detected as an NMR signal at the maximum amplitude. Is used to

FIG. 6 is a diagram for explaining the sequential generation of continuous images 601, 602, 603,... From the repetition of such NMR signal measurement. In FIG. 6, the y-axis gradient magnetic field and the x-axis gradient magnetic field are omitted. However, the sequence from the application of the high-frequency pulse to the measurement of the NMR signal is the same as the sequence shown in FIG. 5, and the measurement of the NMR signal at the first value of the phase encode gradient magnetic field (z-axis gradient magnetic field) pulse 503 is performed. NMR at first view, second value
The measurement of the signal is called the second view. The same applies to the third and lower values.

As described above, the NMR signal of each view is recorded as a digital signal in the memory of the computer 10, and for example, when the measurement of the NMR signal up to the 128th view is completed, the computer
This means that NMR signals of a 128 × 256 matrix are recorded in the memory of 10. Computer 10 calculates the NMR of this matrix.
The signal is subjected to two-dimensional Fourier transform to obtain an xz plane tomographic image. This tomogram 601 is displayed on the first display 12 and the second display 13.

In the continuous imaging, when the NMR signal is measured up to the 128th view, the gradient magnetic field pulse 503 on the z-axis is set to the first value again, and the NMR signal from the first view to the 128th view in the next cycle is obtained. It is measured sequentially.

The computer performs a two-dimensional Fourier transform on the new 128 × 256 matrix data obtained by adding the NMR signal of the first view of the next cycle to the NMR signal of the second view to the 128th view of the first cycle, and performs tomography. FIG. 602 is configured.

Next, NM from the third view to the 128th view
Added the R signal and the NMR signals of the following first and second views12
A tomogram 603 is constructed from 8 × 256 matrix data. By performing image composition processing in this way, a single view NM
A new tomogram is displayed on the first display 12 and the second display 13 at each time interval for measuring the R signal. Assuming that the measurement time of the first view is about 50 milliseconds in the sequence of FIG. 5, 20 images are updated per second, so that the operator can observe changes on the image in real time. can do.

FIG. 7 is a diagram showing a measurement sequence for obtaining the temperature distribution performed in step 308. This sequence is also a sequence based on the same gradient echo method as the sequence shown in FIG. 5, and is set under the same conditions.
That is, the same cross section as the cross section measured in step 304 is excited, the NMR signal 705 is measured as discrete data of, for example, 128 points, the intensity of the phase encoding gradient magnetic field (z-axis) 703 is changed, and the NMR signal is repeated. measure. The matrix data (for example, 128 × 128) thus obtained is recorded in the memory of the computer 10.

The computer 10 performs a two-dimensional Fourier transform on the matrix data to obtain a phase diagram S (t) of the signal of each pixel. In this case, the point of time (time
The NMR signal of the nuclear spin at the temperature of (0) (equivalent to 36 degrees of body temperature) is measured, and the echo time TE (high-frequency pulse) is set so that the phase of the signal of each pixel in the phase diagram S (0) at this time becomes zero. 701
Of the NMR signal 705 until the peak of the NMR signal 705 is detected). By doing so, the phase diagram S
The phase of (t) is the NMR generated by the temperature change during time t.
It can be measured as a phase change of the resonance frequency of the signal.

Here, when the phases of S (0) and S (t) are compared for each pixel, the amount of phase displacement ΔS (t) accompanying the temperature change corresponding to the position can be obtained by calculation. In general, the phase shift ΔS (t)
And the temperature change ΔT (t) is represented by the following equation: ΔT = ΔS / (TE × f × 0.01 × 10−6 × 360) (where f is the resonance frequency, TE is the echo From this equation, the change in temperature during the course of treatment, ie from 36 degrees, can be determined.

As already mentioned, the temperature monitoring step
At 308, the above-described temperature measurement is repeated at regular time intervals Δt while the laser irradiation treatment continues. In this case, the temperature of the body tissue may be obtained from the change between the phase obtained by each temperature measurement and the reference phase diagram S (0), but the phase change is sequentially obtained based on the phase obtained by the immediately preceding measurement. Accordingly, it is possible to obtain the temporal change of the temperature of the body tissue with the error minimized.

FIG. 8 shows an example of such a temperature measurement.
Here, first, the phase diagram S (t) obtained by the temperature measurement sequence (FIG. 7) at time t is used as a reference (801). From this measurement time, the time after Δt set in step 307 (t + Δt)
Next, the temperature measurement sequence is executed again to measure the NMR signals of the 128 × 128 matrix, and the phase diagram S (t + Δt) is calculated (80
2), a phase change φ for each pixel of the phase diagram S (t + Δt) and the reference phase diagram S (t) is obtained (803). From this phase change, a temperature change during Δt is obtained (804). Next, the time (t + Δ
t), the phase diagram S (t + 2Δ
t), and then S (t + Δt) and S (t + Δt) with reference to S (t + Δt).
The phase change of (t + 2Δt) is obtained. As described above, by using the latest phase diagram for the comparison calculation, if Δt is short, an error such as the movement of the subject can be eliminated, and an accurate temperature change amount of the position information can be obtained.

As a method of calculating the temperature change, besides the method of calculating from the above-mentioned phase difference, for example, Japanese Patent Publication No. 6-14
A known method such as a method of measuring a diffusion constant depending on the temperature of an NMR signal and obtaining a temperature described in Japanese Patent Publication No. 911 can be adopted.

Next, a method of displaying the image obtained in step 304 (306) and the temperature information obtained in step 308 will be described.

FIGS. 9A to 9C show the first display 1 respectively.
FIG. 6 is a diagram showing an example of a temperature display by the second and second displays 13. In (a), an image (morphological image or functional image, hereinafter simply referred to as a morphological image) 901 for observing the therapeutic effect taken in step 306 is displayed on the right half of the display, and the temperature distribution calculated from the NMR signal measured in step 308 Figure showing
902 is displayed in the left half. In this case, the temperature distribution may be given a predetermined color so that the temperature can be seen at a glance. For example, the hue may be changed from 30 degrees to 50 degrees in steps of 5 degrees from blue to yellow to red sequentially. With this display, the operator can proceed with the treatment while grasping the progress of the treatment and the temperature around the treatment site.

In (b), the morphological image is displayed on the entire surface of the display, and the temperature distribution chart 903 is reduced so as to be movable to an arbitrary position on the display. According to this display method, a morphological image can be displayed in a large size, and a window screen 903 of the temperature distribution can be displayed on a portion distant from the region of interest.

In (c), the morphological image is displayed on the entire surface of the display, and the temperature calculated from the NMR signal is represented by a contour line 904 or a numerical value.
905 is superimposed and displayed on the corresponding part of the morphological image. By selecting such a display method, it is possible to monitor the treatment process and monitor the temperature with one image.

FIGS. 10 (a) and 10 (b) show still another example of a temperature display method. FIG. 10 (a) shows an inspection part designated by a pointer (cursor) 1002 on a morphological image 1001 and designated. The temperature at the designated position is numerically displayed at a desired position (a position not obstructing the morphological image) 1003 on the screen. With this display method, the temperature of the target portion can be accurately grasped.

FIG. 10B shows a method of displaying a temperature change of a target portion on a time axis. As described above, since the temperature measurement measures a momentary change, this is plotted on a time axis to draw a graph. By employing such a display method, it is possible to predict the time required for the target portion to reach the target temperature from the temperature change curve. Such a temperature change curve can be displayed by providing a window at a position that does not disturb the observation of the region of interest on the screen.

Although the first embodiment of the present invention has been described above, in this embodiment, the measurement of the NMR signal for measuring the temperature is performed at arbitrary time intervals in the process of continuously photographing the image for observing the therapeutic effect. Temperature information, such as temperature distribution charts, temperature values, and graphs, created using the results, is displayed at the same time as images for observing the therapeutic effect, so that temperature changes in cryosurgery, hyperthermia, etc. The accompanying interventional treatment can be effectively performed.

In the above embodiment, step 304 (30
Although the sequence (FIGS. 5 and 7) by the gradient echo method has been exemplified as the sequence of the high-speed imaging method performed in 6) and the temperature measurement sequence performed in step 308, the measurement sequence is not limited thereto, and various changes are possible. is there. For example, the sequence of the spin echo method shown in FIG. 11 may be adopted.

The sequence by the spin echo method is 90
° 180 at a given time TE / 2 after excitation by high-frequency pulse
° Applies a high-frequency pulse to invert the phase of nuclear spin and measure the NMR signal as a spin echo.The phase of nuclear spin diffused by magnetic field distortion other than the applied gradient magnetic field can be matched, so the effect of magnetic field distortion The result is an image with no images.
Therefore, it is preferable to give priority to the depiction of the form.

Also in this spin echo sequence, if the echo time TE is set so that the phase error of the NMR signal is canceled at room temperature (for example, 36 ° C.), the diffusion constant of nuclear spin and When the chemical shift value changes, the phase of the NMR signal in TE changes slightly. Therefore, the temperature change can be calculated by obtaining the phase shift amount of the measured NMR signal.

Next, a second embodiment of the present invention will be described with reference to the flowchart of FIG. In FIG. 12, the same steps as those in the flowchart of FIG. 3 are denoted by the same reference numerals. In this embodiment as well, after placing the subject at the center of the magnet, a tomographic image along the body axis is obtained, a section including the treatment site is set based on the tomographic image, and the section is continuously photographed by the high-speed imaging method. Steps to start treatment (301-3)
04) is similar to the first embodiment shown in FIG.

That is, since the image 402 is displayed on the first display 12 and the second display 13 by continuous imaging (for example, MR fluoroscopy), while observing the image, the operator can perform the biopsy (substantially in real time). The operation of the percutaneous cord is performed, and in the next step 305, transpiration treatment of the affected part by laser irradiation is performed.

At the same time as the start of the transpiration treatment, the NMR signal of the section including the treatment site is measured (311). Calculator 10 uses this NM
The R signal is arithmetically processed to obtain a distribution diagram of the NMR signal intensity and a phase diagram of the NMR signal. As is well known, an NMR signal has intensity information and phase information, so an intensity distribution diagram,
That is, a morphological image and a phase diagram can be obtained. Also in this step 311, a sequence of the gradient echo method may be employed when priority is given to high-speed imaging as an imaging sequence, and a sequence of the spin echo method may be employed when priority is given to a morphological image.

The morphological image is displayed on the first display 12 and the second display 13. At this time, as in the processing shown in FIG. 6, by displaying the absolute value while sequentially replacing the NMR signal of one view, the image is updated every measurement time of one view, and the surgeon can perform real-time image observation. Will be possible.

On the other hand, as for the phase information, the first phase diagram S (t1) is obtained when 128 × 128 matrix data is obtained, and the next phase diagram S (t) is obtained when all the 128 view signals are replaced. Find t2). Next, a temperature change is calculated from the phase change of each pixel in these phase diagrams. The calculation of the temperature is the same as in the embodiment of FIG. As described above, the phase diagram is obtained each time the signal of the 128 views is sequentially exchanged, and the temperature change is sequentially calculated from the phase difference from the immediately preceding phase diagram. An accurate temperature change amount of the position information can be obtained by eliminating an error.

The temperature information thus obtained is displayed on the first display 12 and the second display 13 simultaneously or alternately with the NMR signal intensity distribution chart. As for the display method of the temperature information, an arbitrary display method such as a temperature distribution chart, a numerical display, and a graph can be selected as in the first embodiment.

In the above example, the morphological image (absolute value diagram) is 1
Updated every view measurement (approximately 50 ms), temperature information is 128
Updated every view measurement (approximately 6.4 seconds). After confirming the progress of the treatment on the tomographic image, the operator ends the examination and the treatment, removes the subject 1 from the magnet 2, and ends the procedure (steps 309 and 31).
0). Step 305 and Step 311 for continuation of treatment
Returning to the above, photographing of a tomographic image and display / temperature measurement and display are repeated.

According to the second embodiment of the present invention, a morphological or functional image (absolute value diagram of NMR signal) of a tomographic plane for observing the progress of treatment and a temperature distribution showing a temperature change accompanying the treatment Figure
(Calculated from the phase diagram of the NMR signal) can be obtained in the same measurement sequence, so that the system configuration can be simplified.

In the above embodiment, the case where the temperature is monitored in the process of continuously photographing the morphological image has been described. However, the present invention is not limited to these embodiments, and the photographing of the morphological image and the temperature measurement can be arbitrarily performed. Implementation in combination is also included in the scope of the present invention.

[0078]

According to the present invention, as a function of the control means of the MRI apparatus, a function of arbitrarily combining temperature measurement in one imaging process is provided, and a morphological image and temperature information are displayed as a function of a display means. By providing the function of synthesizing and displaying, it is possible to reliably proceed with the treatment while grasping the temperature of the treatment site, particularly in an interventional treatment involving heat treatment. The temperature display function includes not only a temperature distribution diagram but also a numerical function and a graph function, so that temperature information that can be easily used by an operator can be provided.

[Brief description of the drawings]

FIG. 1 is a diagram showing an overall configuration of an MRI apparatus to which the present invention is applied.

FIG. 2 is a diagram showing a configuration of a display unit of the MRI apparatus.

FIG. 3 is a flowchart showing an embodiment of the examination by the MRI apparatus of the present invention.

FIG. 4 is a view showing a display example of a display in the inspection flow of FIG. 3;

FIG. 5 is a diagram showing an example of a high-speed imaging sequence employed in the MRI apparatus of the present invention.

FIG. 6 is a diagram illustrating continuous imaging and image processing employed in the MRI apparatus of the present invention.

FIG. 7 is a diagram showing an example of a temperature measurement sequence employed in the MRI apparatus of the present invention.

FIG. 8 is a flowchart showing one embodiment of temperature measurement according to the present invention.

FIG. 9 is a view showing a display example of a display by the MRI apparatus of the present invention.

FIG. 10 is a diagram showing another display example of the display by the MRI apparatus of the present invention.

FIG. 11 is a diagram showing another example of the imaging sequence employed in the MRI apparatus of the present invention.

FIG. 12 is a flowchart showing another embodiment of the examination by the MRI apparatus of the present invention.

[Explanation of symbols]

 1 Subject 2 Magnet 3 Gradient magnetic field coil 4 Gradient magnetic field power supply 5 High frequency coil 6 High frequency power amplifier 7 Detection coil 8 Receiver 9 Sequencer 10 Computer 11 Storage device 12 First display 13 Second display 14 Console 15 Table

Claims (3)

[Claims] 1. A static magnetic field generating means for generating a constant magnetic field strength, a gradient magnetic field generating means for generating a magnetic field strength gradient, a means for generating a high frequency magnetic field, and detecting a nuclear magnetic resonance signal from the subject. A magnetic resonance imaging apparatus comprising: means for calculating and displaying a result by reconstructing a tomographic image of the subject using the nuclear magnetic resonance signal; and control means for controlling each of the means. A magnetic resonance imaging apparatus characterized in that the display means includes means for calculating a temperature change of the test part of the subject, and means for displaying the calculated temperature change alternately or simultaneously with the reconstructed image. 2. The nuclear magnetic resonance apparatus according to claim 1, wherein said control means controls to measure a nuclear magnetic resonance signal for temperature measurement while measuring the nuclear magnetic resonance signal for tomographic image of said subject. The magnetic resonance imaging apparatus according to claim 1, wherein a tomographic image obtained by reconstructing a signal and temperature information obtained by calculating a nuclear magnetic resonance signal for temperature measurement are displayed simultaneously or alternately. 3. The control means creates signal intensity data for tomographic images and phase data for calculating temperature information using nuclear magnetic resonance signals obtained from the subject, and reconstructs the signal intensity data. 2. The magnetic resonance imaging apparatus according to claim 1, wherein the displayed tomographic image and the temperature information calculated from the phase data are displayed simultaneously or alternately.