JP2000237160A - Magnetic resonance image diagnostic system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately obtain the temperature distribution of a treatment part, and to improve safety of an IVR operation in an MRI (magnetic resonance image diagnostic system) monitor by providing a means for displaying the temperature distribution together with a reconstituted tissue image in a display means. SOLUTION: A nuclear magnetic resonance signal radiated from an examinee 401 is received by a coil 414b, and after passing through an amplifier 415, a transverse phase is detected by a wave detector 416 to be inputted to a computer 408 through an A/D converter 417 to correct the phase distribution using a resonance frequency of a water proton determined from phase distribution measurement, frequency spectrum measurement of a desired area and a frequency spectrum as a reference. The computer 408 displays an image corresponding to the density distribution of a nuclear spin, the density distribution by imparting contrast by relaxation and the spectrum distribution on a CRT display 428 after processing a signal. Besides a tissue image being the density distribution of the nuclear spin, information showing the temperature distribution of a tissue is displayed, for example, in color.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a magnetic resonance diagnostic apparatus.
(MRI), and particularly to a medical magnetic resonance diagnostic apparatus for measuring temperature distribution.

[0002]

2. Description of the Related Art In recent years, MRI has become an important diagnostic means for diseases as well as X-ray CT as an image diagnostic apparatus having excellent tissue delineating ability. More recently, MRI has not only been diagnosed,
The technology (Interventional MR: IVMR) applied to guide catheters and laser fibers during minimally invasive treatment has been developed. One of its applications is detection of tissue temperature distribution, such as laser ablation of tumors and hernias,
At the time of focused ultrasound ablation, it is receiving attention as a means for monitoring the treatment state of an affected part in real time.

Among the parameters defining the MRI signal, parameters showing temperature dependency include spin density ρ, longitudinal relaxation time T1, transverse relaxation time T2, diffusion coefficient of water, chemical shift δ of water proton (JCHindman, J .Chem.Phys.44.4582,1966)
Etc. Among them, it is said that the reliability of the chemical shift of water protons is high because there is little dependence on factors other than temperature. As a temperature measurement method using a chemical shift, a method using a phase map is effective because the spatial resolution is high and the measurement time is short (Japanese Unexamined Patent Publication No.
No. 5257, “A precise and fast temperature mapping using chemical shifts of water protons (A precise and Fast
Temperature Mapping Method Using Water prot
on Chemical Shift) ", Y. Ishihara, A. Calderon
et al., Abstracts of the Society of Magneti
c Resonance Medicine, 11th annual Meeting, B
erlin, p. 4803 (1992)).

This method uses a gradient echo (Gr.
Using a chemical shift sensitive sequence such as the E) method, the change in the chemical shift before and after the temperature change is detected as the phase difference of the MR signal. The frequency shift of water protons due to temperature is 0.01 ppm / ° C., and the phase difference Δφ is expressed by the following equation (1).

(Equation 1) Here, Δφ is the phase difference at the pixel of interest, Δδ is the change in the chemical shift of water protons at the pixel, γ is the nuclear magnetic rotation ratio, Bo is the static magnetic field strength, and TE is the echo time. The accuracy of the temperature measurement by this method depends on the S / N ratio of the signal and the stability of the hardware, but is about ± 1 ° C.

[0005]

In the method of obtaining the temperature distribution from the phase map, when the phase is rotated by 2π radians or more in the visual field, a jump of the phase value occurs (aliasing). No. But,
For example, in the case of IVR ablation, the area from 1 cm to several cm is heated to a temperature of about 50 ° C. to 200 ° C., so the temperature gradient is large, and complicated aliasing occurs in the phase map,
Aliasing removal becomes difficult.

[0006] In alias removal, the phases of adjacent pixels are sequentially compared under the assumption that the phase of adjacent pixels normally changes smoothly and that there is no rapid change of 2π radians or more. 2 if the change is greater than 2π radians
This is performed by adjusting π. With such an algorithm, when there is a low signal region where the phase is uncertain, it is difficult to perform accurate phase connection across the region. Furthermore, as a basic problem of aliasing removal,
When the phase changes by an integral multiple of 2π, there is a problem that the true phase cannot be known. This occurs when the temperature difference between the treatment site and the surrounding tissue is large.

[0007]

In order to solve the above-mentioned problems, in the present invention, together with a phase map, a spectrum of water protons is measured in a region where temperature is to be measured, and the chemical shift Δδ of the water protons is used to calculate the equation. The phase Δφ is obtained from 1 and is used as a reference value for the aliasing removal processing. Where Δδ is the reference temperature (the temperature of the subject before surgery)
Is the difference between the peak position of the water proton and the peak position at the time of measurement, and the peak position of the water proton at the reference temperature can use a previously measured value.

That is, the MRI apparatus of the present invention comprises a magnetic field generating means for generating a static magnetic field, a gradient magnetic field, and a high-frequency magnetic field, a detecting means for detecting a magnetic resonance signal generated in a subject by applying each magnetic field, and a magnetic field generating means. And control means for controlling the detection means, means for reconstructing an image based on the detected magnetic resonance signal, and display means for displaying the reconstructed image, wherein the control means outputs a high-frequency magnetic field pulse. A means for applying a voltage to excite hydrogen nuclei, performing phase encoding and frequency encoding, collecting a magnetic resonance signal including a change in temperature of a chemical shift of water protons due to temperature as a phase change, and measuring a spatial distribution of a phase of the magnetic resonance signal. And means for measuring the resonance frequency of water protons in one or more small regions, and correcting the phase distribution with the measured resonance frequency as a reference. And means for calculating the temperature distribution in the object from the phase distribution display means is one comprising means for displaying the temperature distribution together with the tissue image, which is reconstructed.

In addition to the phase map, the spectrum of water protons is measured, and the phase Δφ obtained from the chemical shift difference Δδ of the water spectrum by the equation 1 is used as a reference value for the aliasing removal processing of the phase map. (n is an integer), and the true temperature can be obtained.

Here, the number of small regions (for example, voxels) for measuring water protons may be one or more.
At least one is included in the area where the temperature is to be measured. If the temperature change in the region where the temperature is to be measured is relatively monotonous, the number of small regions may be small. In this case, as a method of measuring the spectrum of water proton,
Advantageously, a single voxel method of selecting one voxel and measuring the spectrum is used. The single voxel method can perform measurement with high spatial resolution in a short measurement time.

On the other hand, when the temperature distribution is complicated or there is a region where the signal intensity is low and the phase is indefinite,
Requires many reference points. In this case, a spectroscopic imaging method that can measure many voxels at once is effective as a spectrum measurement method.

Although spectroscopic imaging usually requires a long time for measurement, an echo planar spectroscopic imaging method (hereinafter abbreviated as EPSI; P.Mansf) in which a gradient magnetic field that continuously reverses in the readout direction is applied.
ield's dissertation "High-SpeedSpatially Resolved High
-Resolution NMR Spectroscopy ", J.Am. Chem. So
c., 107, 2817-2818, (1985)), the measurement time can be reduced. Here, unlike normal EPSI, it measures water that exists in large amounts in tissues, not metabolites,
A sufficient signal intensity can be obtained even if the flip angle of the excitation RF pulse is reduced and continuous excitation is performed with a short TR (period of magnetization excitation).

If EPSI is used as a means for measuring water protons, a large number of phase reference points can be obtained, and accurate phase connection can be made across a low signal region having an indeterminate phase. Further EP
Using SI, reduce the flip angle of the excitation RF pulse,
By continuously exciting with a short TR (period of magnetization excitation), a large number of phase reference points can be obtained in a short time.

In the spectrum measurement by the single voxel method, the MRI apparatus of the present invention can be an interactive setting means for setting a measurement area (hereinafter, referred to as an ROI). In this case, the phase map is measured and displayed in the first step, and as a second step, by referring to the displayed phase map, into a region having a large phase change,
Set the measurement area interactively. As a result, the phase reference point can be accurately specified in the surgical site. The ROI setting means can automatically extract a region where the phase map changes greatly. If the ROI is set based on the gradient of the phase map, the process of obtaining an accurate temperature map can be automated.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the MR of the present invention will be described with reference to examples.
The device I will be described in detail. FIG. 4 is an MRI to which the present invention is applied.
It is a schematic structure figure of an apparatus. This MRI apparatus includes an electromagnet or a permanent magnet 402 for generating a uniform static magnetic field Bo inside a subject 401 as a magnetic field generating means, a transmission coil 414a for generating a high-frequency magnetic field, and orthogonal x, y, and z. A gradient magnetic field coil 409 that generates gradient magnetic fields Gx, Gy, Gz whose intensity changes linearly in three directions is provided. The gradient coil 409 is connected to a power supply 410 for supplying a current. Also, a detection coil 414b for detecting a nuclear magnetic resonance signal generated from the subject 401 as a detecting means, a computer 408 for performing various calculations for image reconstruction on the nuclear magnetic resonance signal, and a storage device for storing the calculation results A signal processing system 406 provided with a display 428 for displaying images and an operation unit 421 for inputting to the computer 408 and the like. Although the coils 414a and 414b may be separated for transmission and reception as shown in the figure, they may be coils for both uses.

The computer 408 is also a control means for controlling each magnetic field generating means and detecting means, and a gradient magnetic field generating system 403, a transmitting system 404 and a detecting system 405 via a sequencer 407.
Control the operation of. Next, an outline of the operation of the present apparatus will be described. The high frequency generated by the synthesizer 411 is modulated by the modulator 412 at the timing controlled by the sequencer 407, amplified by the power amplifier 413, and supplied to the transmission coil 414a. As a result, a high-frequency magnetic field is generated inside the subject 401 to excite nuclear spins. The target nucleus is ¹ H
And ³¹ C, ¹² C, etc., but water protons are targeted in the temperature measurement of the present invention.

On the other hand, a gradient magnetic field coil 410 is driven via a gradient magnetic field power supply 410 to apply gradient magnetic fields in a slice direction, a phase encoding direction, and a frequency encoding direction, to select a region for exciting nuclear spins, and to generate a magnetic field. Phase encoding and / or frequency encoding the nuclear magnetic resonance signal to be performed.

The nuclear magnetic resonance signal emitted from the subject 401 is received by the coil 414b, passes through the amplifier 415,
Quadrature phase detection is performed by a detector 416, and input to a computer 408 via an A / D converter 417. After the signal processing, the computer 408 converts the images corresponding to the density distribution of the nuclear spin, the density distribution to which contrast is imparted by relaxation, the spectrum distribution, etc.
Display on the T display 428. In the present invention, information indicating the temperature distribution of the tissue is displayed by, for example, color display in addition to the tissue image which is the density distribution of nuclear spins. Data in the middle of calculation or final data is stored in the memories 424 and 425.

The above-described gradient magnetic field generation system 403, transmission system 404,
The detection system 405 is controlled by a sequencer 407 according to a pulse sequence according to the purpose of measurement.
07 is controlled by the computer 408. In the present invention, the computer 408 performs phase distribution measurement, frequency spectrum measurement for a desired region, and correction of the phase distribution based on the resonance frequency of water protons obtained from the frequency spectrum. An embodiment of temperature measurement in such an apparatus will be described in detail below. Here, it is assumed that a laser ablation of a tumor is performed as an IVR to monitor the temperature of an affected part.

FIG. 1A is a diagram showing a flow of temperature measurement according to one embodiment of the present invention. In this embodiment, a phase map (phase distribution) is created (step 1) after a temperature change (after a temperature rise).
The steps from 1) to the phase unwrapping process (Step 14) are performed, and a corrected phase difference map is obtained (Step 1).
5) Create a temperature difference map from the phase difference map (Step 1)
6). The temperature difference in this case is a temperature difference when the temperature before the temperature rise is set as the reference temperature.

The phase map can be created by executing a sequence of the high-speed GrE method as shown in FIG. 3 (step 11). That is, first, an excitation pulse 31 is applied simultaneously with a slice selection gradient magnetic field 32 for selecting a slice to be subjected to temperature measurement, then, a phase encoding gradient magnetic field pulse 34 and a readout gradient magnetic field pulse 34 are applied, and readout with different polarities is performed. Out gradient pulse 37
While measuring the echo signal 39. After the echo signal measurement, a rewind gradient magnetic field pulse 35 and a spoiler gradient magnetic field 38 in the readout direction are applied in the phase direction.

Such a sequence is repeated for a repetition time TR while changing the magnitude of the phase encoding gradient magnetic field pulse 34. Perform quadrature detection on each of the collected echo signals 39 sequentially, assign them to the real and imaginary parts, arrange them on grid points in k-space, apply two-dimensional Fourier transform, and calculate the arctan of the resulting complex pixel values I do. As a result, a spatial distribution of phases, that is, a phase map is obtained. It is preferable that the fat tissue having no temperature dependency in the phase map measurement sequence is saturated in advance as necessary.

The obtained phase map is displayed on the display 428. This phase image is, for example, an image schematically shown in FIG. 2, and in a region 27 where the temperature has increased, for example, if the static magnetic field is 1.5 T and TE = 80 ms, a phase difference of 920 degrees with respect to a temperature increase of 50 ° C. Occurs. Two or three phase discontinuities 26 between the tissue with no temperature change and the tissue with increased temperature 26
(Three phase discontinuities are shown in FIG. 2).

In such a region, accurate phase correction cannot be performed by ordinary phase unwrapping processing (processing for removing phase aliasing) as described above. Therefore, in the present invention, a reference point is set in this region, and the phase of this reference point is obtained from the spectrum of water protons. Therefore, the next process
In 12, first, an ROI (region of interest) 29 is set inside a region 27 where the temperature has risen (the center is set to (x ₀ , y ₀ )), and a proton spectrum 21 of a single voxel is measured (step
13).

The setting of the ROI is performed by the operator identifying the part 27 where the temperature change has occurred from the phase map 28 displayed on the display monitor in the first step 11 and inputting it with a cursor or the like. The size of the ROI is usually about 1 cm x 1 cm.
As a single voxel spectrum measurement method, STEAM
A known technique such as the PRESS method or the PRESS method can be used. From the water peak value δ1 (x ₀ , y ₀ ) 23 of this spectrum, equation (2)
To calculate the phase Δφ (x ₀ , y ₀ ) at the ROI. Add signals as needed.

[0026]

(Equation 2) Here, [delta] ₀ 22 a chemical shift of water at a reference temperature (temperature before treatment), may be a value measured in advance. Peak position of water proton in spectrum
24 is automatically detected by a computer. As a peak detection method, there is a method of fitting a Lorentz curve and adjusting its position, width, and height. Also, phase correction is used together as necessary.

As described above, the center point (x ₀ ,
After obtaining the phase of (y ₀ ), aliasing removal (phase unwrapping) of the entire image is performed based on the phase (step 1).
Four). As an unwrapping method, first, an offset is removed so that the phase at the reference point (x ₀ , y ₀ ) of the phase map matches Δφ (x ₀ , y ₀ ). Next, the processing is started from the phase reference point, and when there is a change of 2π or more in adjacent pixels, the change is reduced by adding or subtracting 2π. The phase map Δφ (x, y) obtained in this way is accurately phase-unwrapped. According to equation (3), the temperature map ΔT (x, y)
Get.

[0028]

(Equation 3) Where α is the temperature dependence of the chemical shift of the water proton
[0.0 lppm / ° C]. ΔT (x, y) represents the temperature change of the tissue from the reference temperature.

The temperature difference thus obtained is superimposed and displayed on a previously obtained tissue image or a tissue image reconstructed from a signal obtained by executing a sequence for obtaining a phase map. As a temperature display method, for example, a color bar created with an arbitrary temperature width is prepared, and the temperature of a certain pixel is displayed in a color corresponding to the temperature of the color bar. That is,
For example, a temperature of 30 ° C. to 200 ° C. is assigned to the color bar in which the hue sequentially changes in the order of blue-green-yellow-orange-red, and if the temperature of a certain pixel is 100 ° C., it corresponds to the temperature. The color of the color bar (for example, orange) is displayed so as to overlap the luminance of the pixel.

In the temperature measurement of this embodiment, except for the input of the ROI, it can be automatically executed by the computer, and the ROI can be surely set in the area where the temperature change occurs while the operator checks the monitor. it can. In this embodiment,
Although the case where the ROI is set interactively has been described, it is also possible to automatically set 27 in a region where the gradient of the phase map is maximum. In this case, the gradient of the phase is calculated for each pixel by equation (4), a portion where the gradient is maximized is determined, and the ROI of the single voxel spectrum is set in this portion.

[0031]

(Equation 4)

As a result, the temperature distribution can be automatically measured without operator intervention. In this case, the phase image shown in FIG. 2 does not necessarily need to be displayed on the monitor, and only the resulting temperature distribution (the image displayed superimposed on the tissue image) may be displayed. still,
The number of reference points of the phase in the phase unwrapping process may be one or two or more. When there are a plurality of reference points, a plurality of the single voxel spectrum measurement methods described above may be performed. However, if the temperature change in the temperature rising area is complicated or the temperature dependence is low, that is, if a low signal area having an indefinite phase is included, a multi-voxel spectrum can be obtained by spectrum-scope imaging. It is suitable. As a result, water proton spectra can be obtained for many reference points.

As a second embodiment of the temperature measurement of the present invention, E
A case where a multi-voxel spectrum is obtained by a spectroscopic imaging method using PSI will be described. In this embodiment, the peak of the water proton or the shift of the center of gravity is determined for each voxel from the multi-voxel spectrum, and the phase change is calculated from this.

Also in this embodiment, the first step 11 shown in FIG.
This is the same as the above-described embodiment, but here, in the next step 13, an EPSI sequence as shown in FIG. 5 or FIG. 7 is executed. FIGS. 5 and 7 are similar except that the former is an SE type using an inversion pulse 52, while the latter is a GrE type not using an inversion pulse. 7 indicate the reference numerals in FIG. 7) indicate the slice selection gradient magnetic field 53 (7
2) Excitation pulse applied with 52, inversion pulse, 5
4 (73) is the phase encoding gradient magnetic field pulse, 56, 57 (7
5, 76) are readout gradient magnetic field pulses. The readout gradient magnetic field pulse 57 (76) is applied while reversing its polarity a plurality of times, and measures the echo signal 59 (78) for each reversal. After the echo signal measurement, a rewind 55 (74) is added in the phase direction and a spoiler 58 (77) is added in the readout direction to remove coherence of the residual transverse magnetization.

Such a sequence is repeated for each TR while changing the magnitude of the phase encoding gradient magnetic field pulse. For example, when the matrix is 32 × 32, measurement data for obtaining a multi-voxel spectrum is collected with 32 repetitions and 32 inversions of the readout gradient magnetic field pulse 57 (76).

The collected measurement data is subjected to a three-dimensional FFT for kx, ky, and kδ to obtain a proton spectrum 61 for each pixel as shown in FIG. From this spectrum 61, the peak value 63 of the water proton is automatically detected by a computer. still,
In FIG. 6, 66 is a phase discontinuity line, 67 is a temperature rise region, 68
Is a matrix of multi-voxels, and 69 is a phase image.
As a peak detection method, there is a method of fitting a Lorentz curve around a standard water position 64 and finely adjusting the position, width, and height. Also, phase correction is used together as necessary. In this case, if the EPSI method is changed to the GrE type shown in FIG. 7, the signal in the low frequency region is sacrificed, and the swelling of the spectrum baseline occurs, but this does not become a major obstacle to the detection of the water peak. If the EPSI method is the SE type shown in FIG. 5, data at the center of the echo can be acquired, so that swelling of the baseline can be prevented, but the measurement time is longer than that of the GrE type.

From the peak value 63 of the water proton obtained for each pixel as described above, the phase can be obtained for each pixel by the equation (2). The phase map created in the first step 11 is corrected based on the phase of each of these reference points (phase unwrap: step 14). As a result, even if there is a region with a low signal and an indefinite phase, it is possible to jump over the region and accurately remove aliasing.

The calculation of the temperature difference from the phase difference map corrected in this way by the equation (3) and the display of the temperature difference map are the same as in the above-described embodiment. In the sequence shown in FIG. 5 or FIG. 7, the excitation pulse of EPSI (FIG.
The flip angle in (51) can be, for example, 90 ° / n (n is the number of repetitions of excitation). In the above example, n = 32. Excitation due to a small flip angle, that is, partial excitation of longitudinal magnetization, causes a decrease in signal strength.However, unlike ordinary EPSI, the purpose is to detect water present in a large amount in a living body. It does not become.

As an example, when the flip angle is 10 ° and TR = 160 ms, the photographing time is 160 ms × 32 = 5.12 s, and the spectral resolution is 10 Hz from the reciprocal thereof, assuming that the data acquisition time is 100 ms. This is equivalent to 0.16 ppm at 1.5 T, and the temperature resolution is about 16 ° C. In addition, the flip angle may be determined by increasing the order of excitation to make the generated transverse magnetization component constant.

In the above embodiments, the EPSI method is exemplified as the spectroscopic imaging method. However, the present invention is not limited to this, and the 3D-CSI method and the EBI method (PMJakob, A. Ziegler
et.al, "Echo-Time-Encoded Burst Imaging (E
BI): A Novel Technique for Spectroscopic Imagi
ng ", Magn. Reso. Med., 33, 573, 1995). However, the 3D-CSI method has a high spectral resolution but a long measurement time, IV
For temperature measurement in R, high-speed EPSI or EBI is suitable.

Depending on the spectrum measurement method, the spectrum axis may be turned back due to the limitation of the measurement band. For example, if the echo interval (sampling interval in the time axis direction) is 4.0 ms in EPSI, the measurement bandwidth is 1 / 4.0 ms = 250H
z and 3.9 ppm at 1.5T. On the other hand, since water and metabolites in a living body exist in a range of about 5 ppm, there is a possibility that a water peak jumps from one end to another end with a change in temperature. In this case, water is previously arranged at the center of the measurement band, and the frequency jump of water due to temperature can be prevented. Also,
As a method for obtaining a phase map, various known methods other than FIG. 3 can be used.

As described above, in the temperature measurement of the present invention, the phase at that point is determined from the chemical shift of water protons in a small area (voxel), and the aliasing correction of the phase map is performed based on the phase. So
Without finding the difference in the phase map before and after the temperature change (see Figure
Temperature measurement can be performed in the flows 11 to 16 shown in 1 (a).

Accordingly, in the conventional method, the temperature change cannot be calculated when the subject shifts due to body movement before and after the temperature change, but the temperature can be calculated even when the subject shifts. Also, a true temperature can be obtained even when there is no change in temperature in the image and therefore there is no pixel that can be used as a phase reference point. The temperature measurement of the present invention is particularly effective when the temperature changes significantly during the treatment and the phase changes by 2π or more. In such a case, the distribution of the absolute temperature cannot be obtained only by the conventional differential phase map. In particular, a problem arises when an enlarged image is taken and the temperature changes over the entire visual field and a reference temperature region cannot be obtained in the image. In the present invention, the temperature can be measured even in such a case.

Although the chemical shift has been described so far on the assumption that it has a low dependence on factors other than temperature, it is actually affected by other factors. For example, in practice, there is non-uniformity of the static magnetic field due to the magnetic susceptibility distribution of the magnet and the subject, and such non-uniformity of the static magnetic field can also affect the chemical shift. However, when the shimming is performed with high accuracy and the temperature rise is large, only the temperature can be approximately regarded as the cause of the phase change. For example, assuming that the static magnetic field non-uniformity is 0.3 ppm, if the temperature rise is 30 ° C. or more, the temperature-dependent term becomes dominant in the frequency change. As another factor, a phase change caused by a chemical shift of fat may be mixed into the phase map.However, since the lateral relaxation T2 of fat is as short as about 20 ms to 50 ms, the effect can be removed by increasing TE. .

However, in addition to the phase change due to temperature,
When a phase change due to static magnetic field inhomogeneity or the like is included in the phase map, it is also effective to obtain a phase map before and after the temperature change and obtain a temperature difference map from the difference. Thus, only the phase change due to the temperature can be extracted.

FIG. 1B shows such an embodiment. In this embodiment, one of the above-described embodiments is performed twice before and after the temperature change (steps 17 to 19 and 101 are added), and the difference between the corrected phase maps obtained by the two measurements is obtained. (Preparation of phase difference map, step 15), a temperature difference is obtained from this phase difference map by equation (3) and displayed (step 16).
Also in this case, the temperature distribution can be displayed with high accuracy.

[0047]

As described above, according to the present invention, the temperature distribution at the treatment site can be accurately obtained, and the safety of the IVR operation under the MRI monitor can be improved.

[Brief description of the drawings]

FIG. 1 is a diagram showing a temperature distribution measurement procedure executed by an MRI apparatus of the present invention.

FIG. 2 is a view for explaining temperature distribution measurement by using both a spectrum and a phase map.

FIG. 3 is a diagram showing an example of a sequence for phase map measurement.

FIG. 4 is a diagram showing an entire configuration of an MRI apparatus to which the present invention is applied.

FIG. 5 is a view showing a sequence of the SE type high-speed MRSI method.

FIG. 6 is a view for explaining temperature distribution measurement by using both a multi-voxel spectrum and a phase map.

FIG. 7 is a diagram showing a sequence of a GrE-type high-speed MRSI method.

[Description of Signs] 401 Subject 402 Static magnetic field generation magnetic circuit (magnetic field generation means) 408 Computer (image reconstruction means, control means) 409 Gradient magnetic field coil (magnetic field generation means) 414a Transmission RF coil (magnetic field generation means) 414b Detection RF Coil (detection means) 428 Display (display means)

Claims (1)

[Claims] A magnetic field generating means for respectively generating a static magnetic field, a gradient magnetic field, and a high-frequency magnetic field; a detecting means for detecting a magnetic resonance signal generated in a subject by applying each of the magnetic fields;
A magnetic resonance image comprising: a control unit that controls the magnetic field generation unit and the detection unit; a unit that reconstructs an image based on the detected magnetic resonance signal; and a display unit that displays the reconstructed image. In the diagnostic apparatus, the control unit applies a high-frequency magnetic field pulse to excite hydrogen nuclei, performs phase encoding and frequency encoding, and collects a magnetic resonance signal including a change in the chemical shift of water protons due to temperature as a phase change. Means for measuring the spatial distribution of the phase of the magnetic resonance signal; means for measuring the resonance frequency of water protons in one or more small regions; and correcting the phase distribution with reference to the resonance frequency. Means for calculating a temperature distribution in the subject from the phase distribution, wherein the display means displays the temperature distribution together with a reconstructed tissue image. Magnetic resonance imaging apparatus characterized by comprising a stage.