JP5313636B2 - Magnetic resonance imaging system - Google Patents

Description

  The present invention measures a nuclear magnetic resonance (hereinafter referred to as “NMR”) signal from hydrogen, phosphorus, etc. in an object, and images a nuclear density distribution, relaxation time distribution, etc. In particular, the present invention relates to an MRI apparatus suitable for measuring a plurality of magnetic resonance signals including information on chemical shift.

  The MRI apparatus measures NMR signals generated by nuclear spins constituting a subject, particularly human tissue, and images its head, abdomen, limbs, etc. in two or three dimensions. Device. In imaging, the NMR signal is given different phase encoding depending on the gradient magnetic field, frequency-encoded, and measured as time series data. The measured NMR signal is reconstructed into an image by two-dimensional or three-dimensional Fourier transform.

  In contrast to MRI, a method of separating magnetic resonance signals of substances having protons based on a difference in resonance frequency caused by a difference in chemical structure is called a magnetic resonance spectroscopy method. The method of simultaneously acquiring magnetic resonance spectra of multiple regions and imaging the concentration distribution for each substance in the spatial distribution is called magnetic resonance spectroscopic imaging (MRSI) or chemical shift imaging (CSI). ing.

The MRSI method is described in Patent Document 1 or 2, for example. The use of MRSI is expected to detect changes in metabolites in the brain and diagnose metabolic abnormalities.
JP-A-8-112267 JP 2001-231763 A

  In recent years, there is an increasing demand for metabolic information of the entire brain. By using MRSI, a plurality of regions can be set in the brain and the MRS of the region can be obtained, so that magnetic resonance signal peaks of a plurality of metabolites in each region can be obtained. However, it is not easy to grasp the metabolic information of the entire brain based on MRS, which is spectral information of the local region, and the current situation is that the MRS information has not been fully utilized for differentiation and diagnosis of metabolic abnormalities.

  Specifically, currently, when selecting and displaying a spectrum of a plurality of regions, it is performed by parallel display or switching of display of spectra of a desired region. In these display methods, it is possible to compare the entire shape of two spectra, but it is not easy to compare details or quantitatively. In addition, grasping metabolic information from the result of comparing the spectra of two or more regions depends on the skill of the operator.

  The objective of this invention is providing the MRI apparatus which can grasp | ascertain the state in a biological body based on a chemical shift spectrum.

  In order to achieve the above object, the MRI apparatus of the present invention is configured as follows. That is, a static magnetic field generating means for generating a static magnetic field, a gradient magnetic field generating means for applying a gradient magnetic field to an imaging space in the static magnetic field, and a high-frequency magnetic field generating means for irradiating a subject placed in the imaging space with a high-frequency magnetic field , Detecting means for detecting a nuclear magnetic resonance signal generated from the subject, a gradient magnetic field generating means, a high-frequency magnetic field generating means and a detecting means to execute a predetermined pulse sequence, and from the acquired nuclear magnetic resonance signal, a predetermined pulse sequence is executed. An MRI apparatus having control means for generating information, wherein the control means generates a spectrum including chemical shift information for each of a plurality of measurement regions of the subject and a means for reconstructing a tomographic image of the subject. Means and display control means. A display control unit configured to associate a positional relationship between the tomographic image and the measurement region, generate a corresponding image indicating the tomographic image and the spectrum, and display the corresponding image on the display unit; and one observation target region among the plurality of measurement regions And a means for generating and displaying a spectrum superimposed image in which the spectrum and the spectrum of one or more comparison target regions are superimposed. As a result, it is possible to compare the two spectra in detail or to obtain a quantitative comparison by obtaining the degree of coincidence, so that the state of the subject can be easily grasped based on the chemical shift spectrum.

  For example, the display control unit obtains the degree of coincidence between the spectrum of the observation target region and the spectrum of the comparison target region by calculation, and displays the calculation result on the display unit. Thereby, a spectrum can be compared quantitatively.

  Moreover, selection of the observation target region among the plurality of measurement regions is received from, for example, a user.

  The selection of the comparison target area is received from the user, for example. It is also possible to select the comparison target area automatically or semi-automatically by calculation. When the comparison target region is automatically selected, as an example, a measurement region that is symmetric with respect to the observation target region from the center of the tomographic image is selected as the comparison target region. As another example, a measurement region whose spectrum shows an abnormal value is rejected from a plurality of measurement regions, and the remaining measurement region is set as a comparison target region. In the case of semi-automatic, for example, selection of one or more comparison target regions from a plurality of measurement regions is accepted from the user, and the measurement region whose spectrum shows an abnormal value is rejected from the received one or more comparison target regions. The measured area is set as the comparison target area.

  As the above-mentioned corresponding image, for example, an image obtained by superimposing a tomographic image and a measurement region is displayed, and the spectrum of the measurement region is displayed in the measurement region on the image.

  When there are two or more comparison target regions, it is possible to obtain a spectrum obtained by averaging the spectra of two or more comparison target regions as a spectrum superimposed image and display an image obtained by superimposing the spectrum on the observation target region spectrum.

  As the degree of coincidence described above, it is possible to obtain the degree of coincidence of the entire spectrum of the observation target region and the spectrum of the comparison target region. It is also possible to obtain a degree of coincidence between a specific peak in the spectrum of the observation target region and a corresponding peak of the spectrum of the comparison target region.

  The display control means selects one of the measurement areas as an observation target area, selects a measurement area that is symmetrical to the selected observation target area from the center of the tomographic image, and selects the comparison target area. The operation for calculating the degree of coincidence between the spectrum of the observation target region and the spectrum of the selected comparison target region is repeated until all the measurement regions are set as the observation target region, and the measurement region having the lowest degree of coincidence is determined. It is also possible. Thereby, since the measurement region with the lowest degree of coincidence can be automatically detected, the user can make a diagnosis of a metabolic abnormality or the like with reference to this.

  According to the MRI apparatus of the present invention, since a spectrum to be compared with a spectrum to be observed can be superimposed and displayed, they can be compared easily and appropriately, and information useful for diagnosis can be provided. Therefore, the user can grasp the state in the living body based on the chemical shift spectrum.

  Hereinafter, an embodiment of the MRI apparatus of the present invention will be described.

  First, an overall outline of an example of an MRI apparatus according to the present invention will be described with reference to FIG. FIG. 1 is a block diagram showing the overall configuration of an embodiment of an MRI apparatus according to the present invention. This MRI apparatus uses a NMR phenomenon to obtain a tomographic image and MRS (magnetic resonance spectrum) of a subject. As shown in FIG. 1, the MRI apparatus includes a static magnetic field generation system 2, a gradient magnetic field generation system 3, a transmission system 5, a reception system 6, a signal processing system 7, a sequencer 4, a central processing unit (CPU). ) 8.

  The static magnetic field generation system 2 has a static magnetic field generation source arranged around the subject 1. As the static magnetic field generation source, either a permanent magnet, a normal conducting magnet, or a superconducting magnet can be used. In the case of the vertical magnetic field method, the static magnetic field generation source generates a uniform static magnetic field in a direction perpendicular to the body axis in the space around the subject 1. In the case of the horizontal magnetic field method, a uniform static magnetic field is generated in the body axis direction.

  The gradient magnetic field generation system 3 includes a gradient magnetic field coil 9 wound in the three-axis directions of X, Y, and Z, which is a coordinate system (stationary coordinate system) of the MRI apparatus, and a gradient magnetic field power source 10 that drives each gradient magnetic field coil. And the gradient magnetic field power supply 10 of each gradient magnetic field coil 9 is driven in accordance with a command from the sequencer 4 to apply gradient magnetic fields Gx, Gy, and Gz in the three axial directions of X, Y, and Z. At the time of imaging, a slice direction gradient magnetic field pulse (Gs) is applied in a direction orthogonal to the slice plane (imaging cross section) to set a slice plane for the subject 1, and the remaining two orthogonal to the slice plane and orthogonal to each other. A phase encoding direction gradient magnetic field pulse (Gp) and a frequency encoding direction gradient magnetic field pulse (Gf) are applied in one direction, and position information in each direction is encoded in the echo signal.

  The sequencer 4 is a control unit that repeatedly applies a high-frequency magnetic field pulse (hereinafter referred to as “RF pulse”) and a gradient magnetic field pulse in a predetermined pulse sequence, operates under the control of the CPU 8, and produces tomographic image data of the subject 1. Various commands necessary for collection are sent to the transmission system 5, the gradient magnetic field generation system 3, and the reception system 6.

  The transmission system 5 irradiates the subject 1 with an RF pulse in order to cause magnetic resonance to occur in the nuclear spins of the atoms constituting the living tissue of the subject 1. The high-frequency oscillator 11, the modulator 12, and the high-frequency amplifier 13 And a high frequency coil (transmission coil) 14a on the transmission side. The high-frequency pulse output from the high-frequency oscillator 11 is amplitude-modulated by the modulator 12 at a timing according to a command from the sequencer 4, and after the amplitude-modulated high-frequency pulse is amplified by the high-frequency amplifier 13, the high-frequency pulse is arranged close to the subject 1. By supplying to the high frequency coil 14a, the subject 1 is irradiated with the RF pulse.

  The receiving system 6 detects an echo signal (NMR signal) emitted by magnetic resonance of nuclear spins constituting the biological tissue of the subject 1. The receiving system 6 receives a high-frequency coil (receiving coil) 14 b on the receiving side, a signal amplifier 15, and the like. A quadrature detector 16 and an A / D converter 17 are included. An NMR signal emitted from the subject 1 excited by the RF pulse irradiated from the high-frequency coil 14a on the transmission side is detected by the high-frequency coil 14b disposed in the vicinity of the subject 1. The detection signal is amplified by the signal amplifier 15 and then divided into two orthogonal signals by the quadrature phase detector 16 at a timing according to a command from the sequencer 4, and each is converted into a digital quantity by the A / D converter 17. Then, it is sent to the signal processing system 7.

  The signal processing system 7 performs various data processing and display and storage of processing results, and includes a storage device such as an optical disk 19, a magnetic disk 18, a ROM 21, and a RAM 22, and a display 20 including a CRT. When data from the reception system 6 is input to the CPU 8, the CPU 8 executes processing such as signal processing and image reconstruction, and displays the tomographic image of the subject 1 as a result on the display 20 and an external storage device. On the magnetic disk 18 or the like.

  The operation unit 25 inputs various control information of the MRI apparatus and control information of processing performed by the signal processing system 7, and includes an input unit 23 such as a trackball or a mouse and a keyboard 24. The operation unit 25 is arranged in the vicinity of the display 20, and the operator controls various processes of the MRI apparatus interactively through the operation unit 25 while looking at the display 20.

  In FIG. 1, the high-frequency coil 14 a and the gradient magnetic field coil 9 on the transmission side are arranged in the static magnetic field space of the static magnetic field generation system 2 in which the subject 1 is inserted. Specifically, in the case of the vertical magnetic field method, it is installed facing the subject 1, and in the case of the horizontal magnetic field method, it is installed so as to surround the subject 1. The high-frequency coil 14b on the receiving side is installed so as to face or surround the subject 1.

  At present, the radionuclide to be imaged by the MRI apparatus is a hydrogen nucleus (proton) which is a main constituent material of the subject as widely used clinically. Information on the spatial distribution of the proton density and the spatial distribution of the relaxation time of the excited state is imaged, thereby imaging the form or function of the human head, abdomen, limbs, etc. two-dimensionally or three-dimensionally.

  In the present embodiment, imaging of a cross-sectional image of a subject and magnetic resonance spectroscopic imaging (MRSI) are performed using the MRI apparatus.

  The tomographic image is captured by the CPU 8 by causing the sequencer 4 to execute a known pulse sequence such as a spin echo method or a gradient echo method. The obtained NMR signal is Fourier transformed by the CPU 8 to reconstruct a tomographic image.

  In MRSI, the CPU 8 causes the sequencer 4 to execute the pulse sequence shown in FIG. Thereby, an NMR signal is acquired for the same cross section as the tomographic image. At this time, the slice thickness, the phase encoding amount, and the read encoding amount are set so that an NMR signal is acquired for each measurement region 28 (for example, 1 cm square) having a predetermined size shown in FIG.

  In addition, in the pulse sequence shown in FIG. 2, the RF pulse has a frequency band set to cover the resonance frequency band of protons of a plurality of predetermined metabolites (N-acetylaspartate, creatine, choline, etc.) desired to be measured. To do. Thus, by performing Fourier transform on the NMR signal obtained from each measurement region, chemical shift spectrum data in each measurement region can be obtained as shown in FIG.

  In the present invention, the obtained tomographic image data and spectrum data are displayed as follows.

<First Embodiment>
The first embodiment will be described with reference to FIGS. 3A, 3B, and 4. FIG.
In the first embodiment, a chemical shift spectrum image 28 and a tomographic image 29 in each measurement region are generated, and a superimposed image 26 in which the spectrum image 128 and the tomographic image 29 are superimposed is displayed on the display 20. The spectrum image 128 is divided into regions corresponding to the individual measurement regions 28 on the subject on the tomographic image 29, and the chemical shift spectrum 27 obtained from the measurement regions corresponding to the regions 28 is displayed.

  Thus, by displaying the spectrum 27 in association with the measurement region 28 displayed on the tomographic image 29, the overall tendency of the result can be presented. Further, the tomographic image 29 of the subject is an MR image taken in the same cross section as the measurement region 28, and by displaying the measurement region 28 in a superimposed manner, it is possible to present which part of the subject the spectrum measurement was performed on. it can.

  In addition, when the user selects an arbitrary region such as a left-right symmetric region of the brain from the measurement region 28 as the observation target region 30 and the comparison target region 31, both the regions 30 and 31 as illustrated in FIG. The spectrum is enlarged and superimposed. Further, the degree of coincidence of the entire spectrum 35 of the observation target region 30 and the spectrum 36 of the comparison target region 31 or the degree of coincidence of specific spectra is obtained. This makes it possible to grasp a region with a low degree of coincidence by utilizing the left-right symmetry of the brain, etc., and can be used for determining diseases such as metabolic abnormalities.

  The above operation will be specifically described with reference to FIG.

  The CPU 8 reads and executes a program stored in advance in the program storage area 18a of the magnetic disk 18 to operate each unit as follows.

  First, a correspondence relationship between a plurality of measured spectra and their measurement areas is displayed in a format that can be easily recognized. That is, as in the superimposed image 26 in FIG. 3A, the measurement region 28 and the corresponding spectrum 27 are superimposed on the tomographic image 29 of the subject imaged on the same measurement surface in a state where the positional relationship is matched. The image 128 is displayed (step 131).

  The CPU 8 accepts an operation for selecting the observation target spectrum 35 from the user (step 132). The observation target spectrum 35 is a spectrum of the measurement region 28 (observation target region 30) that the user wants to observe, and is determined by a manual operation by the user. As an operation to select, for example, after selecting the corresponding measurement region 28 from the superimposed image 26 in FIG. 3A by mouse operation, the selection is determined by clicking the observation object selection button 113 or the like. After the reception, the CPU 8 can recognize on the display screen which spectrum has been selected as the observation target region 30. This is realized by, for example, distinguishing the color, line type, line width, and the like of the line that divides the measurement region 28. In the superimposed image 26 in FIG. 3A, the observation target region 30 is displayed with a bold line to distinguish it from the surrounding measurement region 28.

  Next, the CPU 8 accepts an operation for selecting the comparison target spectrum 36 from the user (step 133). The comparison target spectrum 36 is a spectrum of the measurement region 28 (comparison target region 31) to be compared with the observation target spectrum 35. The selection of the comparison target spectrum 36 may be single or plural. Similar to step 132, the user selects the measurement region 28 to be compared on the superimposed image 26 in FIG. 3A by operating the mouse, and then determines the selection by clicking the comparison target selection button 112, etc. Thus, the comparison target area 31 is selected. The comparison target spectrum 36 in the comparison target region 31 is displayed separately from the observation target spectrum 35 and other spectra. This is realized, for example, by changing the color, line type, line width, etc. of the line that divides the measurement area 28 as in step 132. In the superimposed image 26 in FIG. 3A, the comparison target region 30 is displayed with a dotted line to be distinguished from the surrounding measurement region 28.

  When the user designates the spectrum superimposition display button 111 from the input unit 23 such as a mouse in the superimposed image 26 shown in FIG. 3A, the CPU 8 displays a graph image in which the observation target spectrum 35 and the comparison target spectrum 36 are superimposed and displayed. 32 is created and displayed on the display 20 as shown in FIG. 3B (step 134). The vertical axis 33 of the graph in the graph image 32 is the signal intensity, and the horizontal axis 34 is the chemical shift amount. For example, the spectrum color, the line type, and the line width are distinguished and displayed so that the observation target spectrum 35 and the comparison target spectrum 36 can be distinguished from each other. For example, in FIG. 3B, the observation target spectrum 35 is displayed with a solid line, and the comparison target spectrum 36 is displayed with a dotted line.

  When the user selects a plurality of comparison target spectra 36, it is also possible to display a spectrum obtained by averaging the comparison target spectra 36 so that the graph image 32 of the spectrum superposition display in FIG. 3B does not become complicated. is there. When performing spectrum superimposition display, the distinction methods match so that the correspondence between the observation target spectrum 35 and the comparison target spectrum 36 can be easily recognized between the superimposed image 26 and the graph image 32 on which the spectrum is superimposed. It is desirable to have.

  Thereby, the user can compare a plurality of spectra desired to be compared on the graph image 32 of FIG. In addition, since a plurality of spectra are displayed on one graph image 32, the graph can be displayed larger than when the same number of spectra are displayed on the same size display, and the difference between the spectra can be easily recognized. can do.

上式（１）におけるSii、Sjj、Sijは下式（２）〜（４）で求める。式（２）〜（４）においてSi(a)は比較対象スペクトル３６であり、Sj(a)は観察対象スペクトル３５である。ａはケミカルシフト量である。

なお、式（２）〜（４）においてSi−（−は上付きのバーを表す）は、Si(a)の平均値であり、Sj−（−は上付きのバーを表す）、Sj(a)の平均値であり、それぞれ下式（５）で表わされる。

Further, when the user clicks the calculation button 115 of the graph image 32 with the input unit 23 such as a mouse, the CPU 8 performs a predetermined calculation, and calculates the entire graph of the observation target spectrum 35 and the comparison target spectrum 36. The degree of coincidence (%) with the entire graph is calculated, and the calculation result is displayed numerically in the calculation result display area 114 on the screen 32 (step 135). When there are a plurality of comparison target spectra 36, the degree of coincidence with the observation target spectrum 35 can be calculated for each. Alternatively, an average of a plurality of comparison target spectra 36 can be obtained, and the degree of coincidence between the average comparison target spectrum 36 and the observation target spectrum 35 can be calculated. As a method for calculating the degree of coincidence, for example, a calculation for obtaining a correlation coefficient ρ is performed. The correlation coefficient is expressed by the following formula (1).

Sii, Sjj, and Sij in the above equation (1) are obtained by the following equations (2) to (4). In the equations (2) to (4), Si (a) is the comparison target spectrum 36 and Sj (a) is the observation target spectrum 35. a is a chemical shift amount.

In the formulas (2) to (4), Si− (− represents a superscript bar) is an average value of Si (a), Sj− (− represents a superscript bar), Sj ( It is an average value of a) and is represented by the following formula (5).

  On the graph of the observation target spectrum 35, when the user selects a specific peak with the mouse or the like, clicks the peak selection button 116, and then clicks the calculation button 115, the peak corresponds to the comparison target spectrum 36. The degree of coincidence with the peak is calculated. The calculation result is displayed as a numerical value in the calculation result display area 114.

  The user can easily recognize the degree of coincidence between the observation target spectrum 35 and the comparison target spectrum 36 based on the numerical values in the calculation result display area 114.

  The user arbitrarily selects the measurement region 28 to be observed and the measurement region 28 to be compared, and determines the measurement region 28 having a high or low coincidence by obtaining the degree of coincidence of the spectra of these measurement regions 28. Can do. Therefore, for example, by utilizing the left-right symmetry of the brain, it is possible to obtain the measurement region 28 with low left-right symmetry and to diagnose that the region has metabolic abnormalities.

<Second Embodiment>
Next, a second embodiment will be described with reference to FIG. In the first embodiment, the user has selected the measurement region 28 of the observation target spectrum 35 and the measurement region 28 of the comparison target spectrum 36. However, in the second embodiment, the comparison target spectrum 36 is automatically or semiautomatically selected. select. Hereinafter, only portions different from the first embodiment will be described, and description of the same portions will be omitted.

  As shown in FIGS. 5 and 6, the CPU 8 causes the display 20 to display a superimposed image 26 (FIG. 3A) of the spectrum image 128 and the cross-sectional image 29 (step 131). In addition to the superimposed image 26, a setting image 155 and a graph image 132 are simultaneously displayed on the screen of the display 20. The setting image 155 is an image for accepting selection of the coordinates of the observation target region 30, the selection method of the comparison target region 31, and the method of superimposing the comparison target spectrum 36 and the observation target spectrum 35 in the graph image 132.

  The CPU 8 accepts selection of the observation target spectrum 35 when the user clicks the observation target region 30 of the observation target spectrum 35 with the mouse or the like in the superimposed image 26 as in the first embodiment (step 132). Alternatively, the setting of the observation target region 30 is accepted by inputting a numerical value of coordinates from the keyboard 24 to the coordinate input region 150 of the setting image 155. In the example of FIG. 6, the spectrum image 128 is divided into 4 × 4 measurement regions 28, and the fourth measurement region 28 in the x direction and the third measurement region 28 in the y direction are selected as the observation target region 30.

  The comparison target spectrum 36 is automatically or semi-automatically selected by the CPU 8 (step 140). The user can select automatic or semi-automatic selection by clicking Auto / Semi auto among the two items 151 (Auto / Semi auto, Manual) of the setting image 155 with a mouse or the like (step 140). When Manual is selected, the comparison target spectrum is manually selected as in the first embodiment. When automatic or semi-automatic selection is selected, the user determines from the pull-down menu 152 which operation is used to select the comparison target spectrum 36 from the plurality of spectra. In the pull-down menu 152, a method (Symmetric Position) of selecting one measurement region 28 that is symmetrical to the observation target region 30 as the comparison target region 31 and a method of selecting all the measurement regions 28 as the comparison target region 31. There are a method of selecting all the measurement areas 28 excluding outliers as the comparison target area 31, a semi-automatic selection method of excluding the area 31 of the spectrum of outliers from the plurality of comparison target areas 31 selected by the user, and the like. .

  The user may be able to select whether the comparison target spectrum 36 is a single spectrum or a plurality of spectra.

求めた(x',y')を比較対象領域３１の位置p_r(x',y')とする（ステップ５３）。 When the user selects Symmetric Position from the pull-down menu 152, the CPU 8 uses the left-right symmetry of the brain and selects a spectrum at a position symmetrical to the observation target region 30 as the comparison target spectrum 36. This will be specifically described with reference to FIGS. When p (x, y) is the position of the observation target region 30 and p _r (x ′, y ′) is the position of the comparison target region 31, the CPU 8 first detects the coordinates (x, y) of the observation target region 30. (Step 51). Next, coordinates (x ′, y ′) symmetrical with respect to the detected coordinates are obtained by the following equation (6) (step 52). Here, m represents the number of regions 28 in the horizontal direction (x direction).

The obtained (x ′, y ′) is set as the position p _r (x ′, y ′) of the comparison target region 31 (step 53).

  When the user selects a method of selecting all the measurement areas 28 except for abnormal values as the comparison target area 31 in the pull-down menu 152, the spectrum indicating the abnormal values is excluded from the spectra of all measurement areas 28, and the remaining measurement areas are selected. It selects as comparison object field 31. For example, a rejection test is used as a method for determining a spectrum indicating an abnormal value.

  Rejection tests include Dixon's method and Grubbs' method. Here, a processing procedure using the Dixon method will be described with reference to FIG. First, an averaged spectrum S (a) − (− represents a superscript bar) obtained by averaging spectra S (a) (where a is a chemical shift value) of all measurement regions 28 is obtained (step 61). . Next, for each spectrum S (a), a difference spectrum D (a) from the averaged spectrum S (a) − is obtained. (Step 62).

Next, using equation (7), the sum Σ in the a direction (X-axis direction) of the absolute value of the difference spectrum D (a) is obtained, and this is used as the feature amount f of the spectrum S (a) (step 63). ). Note that another means such as a sum of squares may be used as long as the feature amount of the spectrum S (a) can be expressed.

これにより、異常値を除去した残りのスペクトルをすべて比較対象スペクトルとして選択することが可能である。 After obtaining the feature value f for each spectrum S (a), the values of f are rearranged in order of magnitude (step 64). Using the maximum value (f _L ) and minimum value (f ₁ ) of the feature quantity f, the feature quantity f _{i of the} spectrum, the next smallest feature quantity f _i−1, and the rejection limit value Q, the following formula ( the spectrum of _{f i} satisfying 8) determines that an abnormal value is removed (step 65). Here, Q is a known rejection limit value determined in advance by the number of spectra.

Thereby, it is possible to select all remaining spectra from which abnormal values have been removed as comparison target spectra.

  On the other hand, when the user selects a plurality of comparison target regions 31 in the pull-down menu 152 and then selects a semi-automatic selection method that excludes the region 31 of the abnormal value spectrum, the CPU 8 A manual selection of the comparison target spectrum 36 is accepted, and a spectrum showing an abnormal value is automatically removed from the selection. The above-described method of FIG. 8 can be used to determine a spectrum indicating an abnormal value.

  After the comparison target spectrum is automatically or semi-automatically determined as described above, the process proceeds to step 134 in FIG. 5, and the observation target spectrum and one or more comparison target spectra, or two or more comparison target spectra, as in the first embodiment. The average spectrum is superimposed and displayed. Furthermore, the degree of coincidence between the observation target spectrum and the comparison target spectrum can be calculated, and the result can be displayed as a numerical value to the user (step 135).

  Here, the user manually selects the observation target area 28 in step 132, but the CPU 8 sequentially selects all the measurement areas 28 as the observation target area 30, and executes each step of FIG. 5 each time. Thus, for example, the degree of coincidence with the spectrum of the comparison target region 31 that is symmetric with respect to the spectrum of all the measurement regions 28 can be automatically obtained. As a result, for example, it is possible to automatically obtain the measurement region 28 having the lowest left-right symmetry, and it can be used as a judgment material for the user to find a region having the lower left-right symmetry due to metabolic abnormality.

  In the second embodiment, the method of each step in FIG. 7B is used when the comparison target region 31 that is symmetrical with respect to the observation target region 30 is automatically selected. In this method, the comparison target region 31 can be easily selected on the assumption that the right and left center of the measurement region 28 of the spectrum image 128 matches the right center of the tomographic image 29. However, when the left and right center of the measurement region 28 of the spectrum image does not coincide with the left and right center of the tomographic image 29, the distance between the observation target region 30 and the left and right center of the tomographic image 29 is obtained by calculation, and the opposite side from the left and right center. For example, a calculation method such as setting a measurement region separated by the same distance as a comparison target region can be used.

<Third Embodiment>
Next, a third embodiment will be described with reference to FIG. The difference from the first and second embodiments is that a method for displaying a plurality of superimposed spectra can be selected. Hereinafter, only different portions will be described, and description of the same portions will be omitted.

  First, the CPU 8 displays the image 26 (FIG. 3A) obtained by superimposing the spectrum image 28 and the tomographic image 29, and accepts the user's manual selection of the observation target spectrum 35 (steps 131 and 132). Next, the comparison target spectrum 36 is selected manually, automatically, or semi-automatically (step 141). Manual selection is the operation of step 133 of the first embodiment, and automatic or semi-automatic selection is the operation of step 140 of the second embodiment.

  Next, a superimposition method for displaying the comparison target spectrum 36 on the observation target spectrum 35 is received from the user (step 141). As a superimposing method, in addition to a method of displaying the comparison target spectrum 36 as it is, a method of displaying an average of a plurality of comparison target spectra, a method of displaying a difference from the observation target spectrum, a plurality of display methods, and the like. Make selectable. A display example of the difference spectrum 37 between the observation target spectrum 35 and the comparison target spectrum 36 is shown in FIG. When the comparison target spectrum 36 is single, the difference from the observation target spectrum 35 is obtained. When there are a plurality of comparison target spectra 36, first, an averaged spectrum of the comparison target spectrum 36 is obtained, and then a difference from the observation target spectrum 35 is obtained.

  In step 143, the comparison target spectrum 36 is superimposed on the observation target spectrum 35 and displayed according to the display method selected in step 142. At this time, it is also possible to display the comparison target spectrum by two or more kinds of superposition methods. For example, the spectrum obtained by averaging all the spectra and the spectrum of the comparison target region at a position symmetrical to the observation target region are superimposed and displayed. At this time, for example, color display or dotted broken lines are displayed so as to distinguish which spectrum is used to display each spectrum on the graph.

  Thereby, it is possible to display the spectrum in a format that is easier for the user to compare.

1 is a block diagram showing an overall configuration of an MRI apparatus of an embodiment. The block diagram which shows the MRSI pulse sequence for obtaining a chemical shift spectrum in 1st Embodiment. (A) Explanatory drawing which shows the example of a screen of the superimposition image of the spectrum image of chemical shift of 1st Embodiment, and a tomographic image, (b) Explanation which shows the example of a screen of the graph image which superimposed the observation object spectrum and the comparison object spectrum Figure. 3 is a flowchart showing display control of the MRI apparatus of the first embodiment. 6 is a flowchart showing display control of the MRI apparatus of the second embodiment. Explanatory drawing which shows the example of a screen displayed in 2nd Embodiment. (A) In 2nd Embodiment, explanatory drawing which shows detecting the left-right symmetric position of an observation object area | region as a comparison object area | region, (b) The flowchart of a detection process. The flowchart of the process which removes the spectrum which shows an abnormal value in 2nd Embodiment. 10 is a flowchart showing display control of the MRI apparatus of the third embodiment. Explanatory drawing which shows the example of a display of a difference spectrum in 3rd Embodiment.

Explanation of symbols

1 ... subject, 2 ... static magnetic field generation system, 3 ... gradient magnetic field generation system, 4 ... sequencer, 5 ... transmission system, 6 ... reception system, 7 ... signal processing system, 8 ... central processing unit (CPU), 9 ... Gradient magnetic field coil, 10 ... Gradient magnetic field power supply, 11 ... High frequency transmitter, 12 ... Modulator, 13 ... High frequency amplifier, 14a ... High frequency coil (transmitting coil), 14b ... High frequency coil (receiving coil), 15 ... Signal amplifier, 16 ... quadrature detector, 17 ... A / D converter, 18 ... magnetic disk, 19 ... optical disk, 20 ... display, 21 ... ROM, 22 ... RAM, 23 ... input section (trackball or mouse), 24 ... keyboard, 25 ... operation unit, 26 ... superimposed image, 27 ... spectrum, 28 ... measurement region, 29 ... tomographic image of subject, 30 ... observation target region, 31 ... comparison target region, 32 ... graph on which spectrum is superimposed, 33 ... graph vertical axis, 34 ... graph horizontal axis, 35 ... observation target spectrum, 36 ... comparison target spectrum, 37 ... difference Spectral

Claims (13)

A static magnetic field generating means for generating a static magnetic field, a gradient magnetic field generating means for applying a gradient magnetic field to the imaging space in the static magnetic field, and a high-frequency magnetic field generating means for irradiating a subject placed in the imaging space with a high-frequency magnetic field; The detection means for detecting a nuclear magnetic resonance signal generated from the subject, the gradient magnetic field generation means, the high-frequency magnetic field generation means and the detection means are controlled to execute a predetermined pulse sequence, and the acquired nuclear magnetic resonance signal Control means for generating predetermined information from
The control means includes means for reconstructing a tomographic image of the subject, means for generating a spectrum including chemical shift information for each of the plurality of measurement regions of the subject, and display control means,
The display control means associates the positional relationship between the tomographic image and the measurement region, generates a correspondence image indicating the tomographic image and the spectrum, and displays the corresponding image on the display means; and the plurality of measurement regions A magnetic resonance imaging apparatus comprising: means for generating and displaying a spectrum superimposed image in which the spectrum of one observation target region and the spectrum of one or more comparison target regions are superimposed.   2. The magnetic resonance imaging apparatus according to claim 1, wherein the display control unit obtains a degree of coincidence between the spectrum of the observation target region and the spectrum of the comparison target region by calculation, and displays the calculation result on the display unit. A magnetic resonance imaging apparatus.   3. The magnetic resonance imaging apparatus according to claim 1, wherein the display control unit receives selection of the observation target region from the user among the plurality of measurement regions.   3. The magnetic resonance imaging apparatus according to claim 1, wherein the display control unit receives selection of one or more of the comparison target regions from the plurality of measurement regions from a user.   3. The magnetic resonance imaging apparatus according to claim 1, wherein the display control unit performs selection of one or more of the comparison target regions among the plurality of measurement regions by calculation.   6. The magnetic resonance imaging apparatus according to claim 5, wherein the display control unit selects, as the comparison target region, a measurement region that is symmetric with respect to the observation target region from the center of the tomographic image. Magnetic resonance imaging device.   6. The magnetic resonance imaging apparatus according to claim 5, wherein the display unit rejects a measurement region whose spectrum shows an abnormal value from the plurality of measurement regions, and sets the remaining measurement region as the comparison target region. A magnetic resonance imaging apparatus.   3. The magnetic resonance imaging apparatus according to claim 1, wherein the display control unit receives selection of one or more of the comparison target regions from the plurality of measurement regions from a user, and receives the one or more comparison target regions received from the user. A magnetic resonance imaging apparatus characterized in that a measurement region whose spectrum shows an abnormal value is rejected, and the remaining measurement region is set as the comparison target region.   The magnetic resonance imaging apparatus according to claim 1, wherein the display control unit displays an image obtained by superimposing the tomographic image and the measurement region as the corresponding image, and in the measurement region on the image, A magnetic resonance imaging apparatus for displaying the corresponding spectrum.   2. The magnetic resonance imaging apparatus according to claim 1, wherein when the comparison target region is two or more, the display control unit obtains a spectrum obtained by averaging two or more spectra of the comparison target region as the spectrum superimposed image. A magnetic resonance imaging apparatus for displaying an image in which this is superimposed on a spectrum of the observation target region.   3. The magnetic resonance imaging apparatus according to claim 2, wherein the display control unit obtains an overall coincidence between the spectrum of the observation target region and the spectrum of the comparison target region as the coincidence. apparatus.   3. The magnetic resonance imaging apparatus according to claim 2, wherein the display control unit has a degree of coincidence between a specific peak of the spectrum of the observation target region and a corresponding peak of the spectrum of the comparison target region as the degree of coincidence. A magnetic resonance imaging apparatus.   3. The magnetic resonance imaging apparatus according to claim 2, wherein the display control unit selects one of the measurement regions as the observation target region, and from the center of the tomographic image with respect to the selected observation target region. A measurement region at a symmetric position is selected as the comparison target region, and an operation for calculating the degree of coincidence between the spectrum of the selected observation target region and the spectrum of the selected comparison target region is performed on all measurement regions. A magnetic resonance imaging apparatus characterized in that the measurement area having the lowest degree of coincidence is discriminated by repeating the process until the area is obtained.

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