JP2016209336A - Magnetic resonance imaging apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an MRI apparatus which enables quantitative comparison/evaluation of quantitative value images taken at different dates and by different apparatuses to be performed simply.SOLUTION: A magnetic resonance imaging apparatus comprises: a magnetic field generation part for generating a uniform static magnetic field and a gradient magnetic field superposing to the static magnetic field in a space accommodating an analyte; a detection part for irradiating the analyte with a high frequency magnetic field and detecting NMR signals generated from the analyte; and a processing part for imaging the detected NMR signals as a quantitative value image. The processing part acquires past examination information from past images acquired at different dates or by different apparatuses (202), determines current examination information using the acquired examination information (204), executes current examination based on the determined examination information (205), and compares acquired current images with the past images (206).SELECTED DRAWING: Figure 2

Description

  The present invention relates to a magnetic resonance imaging apparatus, and more particularly to a technique for comparing and evaluating quantitative value images.

  A magnetic resonance imaging (hereinafter referred to as “MRI”) device measures a nuclear magnetic resonance (hereinafter referred to as NMR) signal generated by a nuclear spin constituting a subject, particularly a human tissue, and the head, abdomen, limbs, etc. This is an apparatus for imaging the form and function of the two-dimensionally or three-dimensionally. 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.

  Unlike the CT value, the signal intensity obtained by the MRI apparatus has no unit and can vary depending on various conditions. Factors affecting the signal intensity include those derived from living tissue, those based on the imaging sequence principle and measurement conditions, and those based on the adjustment state of the apparatus. Proton density, T1 value, T2 value, flow information, diffusion coefficient, etc. of living tissue are derived from living tissue. TE, flip angle, FOV, slice thickness, etc. are based on measurement conditions and can be controlled. Furthermore, the static magnetic field strength and the uniformity thereof, the accuracy of RF pulse transmission, the sensitivity of the coil, and the like are based on the adjustment state of the apparatus. Therefore, the signal strength itself is not evaluated, and visual evaluation is often performed using a relative value given an appropriate window value for each image, and comparison between images is difficult.

  Therefore, the MRI image is quantitatively evaluated by calculating the T1 value, T2 value, T2 * value, etc. (hereinafter referred to as a quantitative value) and imaging (hereinafter referred to as a quantitative value image) of the living tissue. There is an attempt. For example, in a liver examination, a T2 * value image may be used to observe the degree of iron deposition on the liver. When iron deposits in the tissue, the T2 * value decreases compared to normal tissue. In this way, by making the pixel value a quantitative value from the signal intensity, evaluation as an absolute value and comparison between images can be performed.

  As an evaluation method of this quantitative value image, there are a visual evaluation and a quantitative evaluation by calculating a region of interest (ROI) statistic. For visual evaluation, the quantitative value image is often used by being superimposed on the morphological image and displayed in color. This is because the visibility of the distribution of quantitative values is improved by color display. However, even for quantitative value images of the same subject, it is not easy to quantitatively compare examination images acquired at different dates and times.

  As a conventional technique regarding comparison of inspection images acquired at different dates and times, there is Patent Document 1. This is because when the same subject is imaged at different times with the MRI apparatus and the follow-up observation is performed under the same conditions as in the past, even when the fixed angle of the subject is different from the past examination, A technique that enables imaging is disclosed.

JP 2009-28147 A

  The reason why quantitative comparison of examination images acquired at different dates and times is not easy is because the posture of the subject at the time of examination, positioning of imaging, and ROI setting for calculating statistics are manually performed It is. In addition, there may be cases where the devices used are different due to reasons such as second opinion or hospital transfer. In particular, since the quantitative value changes due to the influence of the static magnetic field strength and the magnetic field uniformity, it is also difficult to compare the quantitative image when the apparatuses are different. Patent Document 1 is a technique for imaging at the same position as a past examination, and no examination is made regarding comparison of obtained images.

  An object of the present invention is to provide an MRI apparatus that solves the above-described problems and that enables simple comparison and evaluation of images obtained at different dates and times and with different apparatuses.

  In order to achieve the above object, in the present invention, an MRI apparatus includes a uniform static magnetic field in a space for accommodating a subject, a magnetic field generating unit that generates a gradient magnetic field superimposed on the static magnetic field, and a subject A detection unit that detects an NMR signal generated from a subject by irradiating a high-frequency magnetic field to the subject, and a processing unit that images the detected NMR signal, the processing unit is a past image obtained with a different date and a different device MRI device configured to obtain past examination information from the image, determine the current examination information using the obtained examination information, and display the current image obtained based on the decided examination information and the past image in a comparable state I will provide a.

  According to the present invention, it is possible to simply perform quantitative comparison / evaluation of images taken at different dates and times or by different apparatuses.

It is a figure which shows an example of the whole structure of the MRI apparatus based on each Example. 6 is a flowchart of image group comparison according to Embodiment 1. FIG. 1 is a system configuration diagram of an MRI apparatus according to Embodiment 1. FIG. It is a flowchart figure regarding estimation of the quantitative value calculation method based on Example 1. FIG. It is a figure which shows an example of the user interface based on Example 1. FIG. It is a figure which shows an example of the user interface for the comparison of a measurement condition based on Example 1. FIG. It is a figure which shows an example of the user interface for the comparison of the positioning based on Example 1. FIG. FIG. 3 is a diagram illustrating an example of a user interface for image comparison according to the first embodiment. It is a flowchart regarding the process which excludes the difference of the quantitative value between models based on Example 1. FIG. It is a figure which shows an example of the user interface for ROI statistical comparison based on Example 1. FIG. 1 is a system configuration diagram of an MRI apparatus according to Embodiments 2 and 3. FIG. FIG. 10 is a diagram illustrating an example of a user interface for comparison with statistical data according to the second embodiment.

  Hereinafter, various embodiments of the MRI apparatus of the present invention will be described in detail with reference to the accompanying drawings. Note that components having the same function are denoted by the same reference symbols throughout the drawings for describing the embodiments of the invention, and the repetitive description thereof is omitted.

  First, an overall outline of an example of an MRI apparatus common to all the embodiments will be described with reference to FIG. FIG. 1 is a block diagram showing an example of the overall configuration of the MRI apparatus. This MRI apparatus obtains a tomographic image of a subject using an NMR phenomenon. As shown in FIG. 1, the MRI apparatus includes a static magnetic field generation system 2, a gradient magnetic field generation system 3, and a transmission system 5. A receiving system 6, a signal processing system 7, a sequencer 4, and a central processing unit (CPU) 8. The static magnetic field generation system 2 and the gradient magnetic field generation system 3 form a magnetic field application unit. The transmission system 5 and the reception system 6 form a detection unit.

  The static magnetic field generation system 2 generates a uniform static magnetic field in the direction perpendicular to the body axis in the space around the subject 1 if the vertical magnetic field method is used, and in the direction of the body axis if the horizontal magnetic field method is used. Thus, a permanent magnet type, normal conducting type or superconducting type static magnetic field generating source is arranged around the subject 1.

  The gradient magnetic field generation system 3 includes a gradient magnetic field coil 9 that applies a gradient magnetic field in the three-axis directions of X, Y, and Z, which is a coordinate system (static coordinate system) of the MRI apparatus, and a gradient magnetic field that drives each gradient magnetic field coil. Gradient magnetic fields Gx, Gy, Gz are applied in the three axial directions of X, Y, and Z by driving the gradient magnetic field power supply 10 of each coil according to a command from the sequencer 4 described later. . 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 into an echo signal.

  The sequencer 4 is a control means 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, and operates under the control of the CPU 8 to collect tomographic image data of the subject 1. Various commands necessary for the transmission 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 RF pulses in order to cause nuclear magnetic resonance to occur in the nuclear spins of the atoms constituting the living tissue of the subject 1, and includes a high-frequency oscillator 11, a modulator 12, and a high-frequency amplifier. 13 and a high frequency coil (transmission coil) 14a on the transmission side. The RF 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 the amplitude-modulated RF pulse is amplified by the high-frequency amplifier 13 and then placed 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 nuclear magnetic resonance of nuclear spins constituting the biological tissue of the subject 1, and receives a high-frequency coil (receiving coil) 14b and a signal amplifier 15 on the receiving side. And a quadrature phase detector 16 and an A / D converter 17. After the NMR signal of the response of the subject 1 induced by the electromagnetic wave irradiated from the high frequency coil 14a on the transmission side is detected by the high frequency coil 14b arranged close to the subject 1 and amplified by the signal amplifier 15, The signal is divided into two orthogonal signals by the quadrature phase detector 16 at the timing according to the command from the sequencer 4, and each signal is converted into a digital quantity by the A / D converter 17 to be converted into a signal processing system 7 constituting the processing unit. Sent.
The signal processing system 7 as a processing unit performs various data processing and display and storage of processing results, and includes an external storage device such as an optical disk 19 and a magnetic disk 18 and a display 20 including a CRT or the like. When data from the receiving 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, which is a part of the processing unit, inputs various control information of the MRI apparatus and control information of processing performed by the signal processing system 7, and includes a trackball or mouse 23 and a keyboard 24. The operation unit 25 is disposed close to 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 14a and the gradient magnetic field coil 9 on the transmission side are opposed to the subject 1 in the static magnetic field space of the static magnetic field generation system 2 into which the subject 1 is inserted. If the horizontal magnetic field method is used, the subject 1 is installed so as to surround it. The high-frequency coil 14b on the receiving side is installed so as to face or surround the subject 1.

  Currently, 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 in clinical practice. By imaging information on the spatial distribution of proton density and the spatial distribution of relaxation time in the excited state, the form or function of the human head, abdomen, limbs, etc. is imaged two-dimensionally or three-dimensionally.

  In the following description of various embodiments of the present invention, images obtained by past examinations and combinations thereof are referred to as past images and past image groups, images obtained by current examinations, and combinations thereof are present images, present combinations. This is called an image group.

  The first embodiment is an embodiment of an MRI apparatus that enables simple comparison / evaluation of quantitative value images captured with different dates and times and different apparatuses. That is, an MRI apparatus, which is generated from a subject by irradiating a subject with a high-frequency magnetic field, and a magnetic field generation unit that generates a gradient magnetic field superimposed on the static magnetic field in a space in which the subject is accommodated A detection unit that detects an NMR signal and a processing unit that images the detected NMR signal are provided. The processing unit acquires past examination information from past images obtained with different dates and times and with different devices. This is an embodiment of the MRI apparatus configured to determine the current examination information using the examination information and display the current image acquired based on the decided examination information and the past image in a comparable state.

  The outline of the processing flow in the processing unit of the apparatus according to the first embodiment will be described with reference to FIG. First, in step 201, a past image group is acquired. Here, the past image group is a generic name of the obtained plural types of past images. In step 202, the past image group is analyzed to obtain past examination information. In step 203, the obtained past examination information of the past image group is applied to the current examination. In step 204, the inspection condition which is the current inspection information applied is adjusted and finally determined. In Step 205, after the adjustment, the current inspection is performed using the inspection information finally determined, and a current image group including a plurality of types of current images is obtained. In step 206, the obtained current image group and the past image group are compared. Details of each step will be described later.

  A configuration example of a processing unit that is a main part of the MRI apparatus according to the first embodiment will be described in detail with reference to FIG. This configuration corresponds to the signal processing system 7 and the operation unit 25 in FIG. The console 301 includes a CPU 8, an optical disk 19, a magnetic disk 18, a display 20, an operation unit 25, a ROM 21, and a RAM 22. ROM 21 and RAM 22 are handled as memory 302 without considering both. The console 301 is connected to a hospital network or the Internet 303. Further, it is assumed that an external server 304 is similarly connected to the Internet 303. The CPU 8 executes the processing flow of FIG. 2 by executing a program stored using the ROM 21, RAM 22, and the like.

  Next, steps 201 to 206 in FIG. 2 will be sequentially described. In step 201, a past image group is acquired. The past image group is usually stored in DICOM (Digital Imaging and Communication in Medicine) format on a portable medium such as a DVD, a hospital network, or a server connected via the Internet. When the past image group is stored in the portable medium, the corresponding image group is extracted using the optical disk 19 and stored in the magnetic disk 18. When the past image group is stored in the server 304, the corresponding image group is extracted via the hospital network or the Internet 303, and similarly stored in the magnetic disk 18.

  In step 202, the past image group is analyzed to obtain inspection information. The past image group obtained in step 201 includes images that are not related to calculation of quantitative values such as images that are input of quantitative value images, quantitative value images, positioning images, and T2-weighted images, but are necessary for diagnosis. ing. In step 202, inspection information necessary for performing an inspection under the same conditions as the past image group in the current inspection is extracted. The inspection information includes the measurement conditions and positioning information obtained by capturing each image, the input image for calculating the quantitative value image, the algorithm for calculating the quantitative value, the position of the analysis ROI for calculating the statistic from the quantitative value image, The result of analyzing the shape and ROI can be mentioned.

  Here, the measurement conditions refer to conditions necessary for capturing the image, such as an imaging sequence, FOV, slice thickness, number of slices, and reconstruction matrix size. This is obtained from the DICOM information of each image. The positioning refers to information on how to set the imaging region for the apparatus at the time of imaging, and is acquired from the DICOM information in the same manner as the measurement conditions. Since the past image group includes only candidate images that can be input and the quantitative value image that is the result of the calculation, the input image used for calculating the quantitative value image and the algorithm for calculating the quantitative value are derived from the past image group. Information cannot be obtained directly.

  Therefore, in this embodiment, an input image and a quantitative value calculation algorithm for calculating a quantitative value image are estimated by the method shown in FIG. In the figure, in step 401, the type of quantitative value estimated from the quantitative value image included in the past image group is determined. In step 402, a theoretical function of the signal value corresponding to the quantitative value is obtained. Here, a case where the quantitative value image is a T2 * value image will be described as an example. Assuming that the signal intensity obtained by the imaging method based on the GE (gradient echo) method follows a theoretical function, it becomes a function of Equation 1, and the TR value is fixed and the signal value is expressed with two types of TE values. T2 * value can be calculated by acquiring and substituting into Equation 1 and transforming the equation. As described above, since a theoretical function is determined for each quantitative value, a correspondence table between the quantitative value and the function is stored in the memory 302 in advance.

  However, since the actual signal value includes noise and does not match a value obtained from a theoretical function, a quantitative value must be estimated from a plurality of acquired signal values. Therefore, in step 403, a candidate for a quantitative value estimation technique is acquired. In the case of T2 * value as an example, the TR value is fixed and the TE value is changed to obtain multiple signal values.Equation 1 is logarithmically transformed and estimated by the least squares method. There is a method of estimating by a non-linear least square method. As an evaluation method of the nonlinear least square method, there are a method for evaluating an absolute value of an error, a method for evaluating a least square sum, and the like. In addition, the linear square method can calculate the T2 * value analytically, but the nonlinear square method needs to be calculated by an iterative method, and examples of the iterative method include the steepest descent method and the Newton method. The plurality of estimation candidates are stored in the memory 302 in advance, and are read and used when step 403 is executed.

  Next, in step 404, an image as an input candidate for quantitative value calculation is estimated from the past image group. The signal value used for the quantitative value calculation corresponds to the pixel value of a part of the image of the past image group. The input candidate image can be determined from the imaging sequence. For example, in order to calculate the T2 * value, an image captured by the GE method is necessary. A correspondence between the quantitative value and the input imaging sequence is stored in the memory 302 in advance.

  In step 405, possible combination patterns are detected from a plurality of input candidate images. For example, when calculating the T2 * value as a quantitative value, the possible combination patterns are two or more pairs of images taken at the same position with the same TR value and different TE values among the images extracted in 404. It becomes a combination.

  In step 406, for a certain pixel, a quantitative value is calculated based on the combination of the theoretical function obtained in step 402, the quantitative value estimation method obtained in step 403, and the input obtained in step 404. When the number of estimation methods obtained in step 403 is L and the number of input combinations obtained in step 404 is M, a quantitative value of an L × M pattern is obtained for each pixel.

  In step 407, an error between the calculated quantitative value and the pixel value at the same position in the quantitative value image of the past image group is obtained. In the flow of FIG. 4, the sum of absolute values of errors is adopted as an error evaluation method, but other evaluation methods may be used.

  In step 408, after calculating the absolute value sum of the error between the pixel value of the quantitative value image for each of N pixels and the quantitative value estimated for each pattern, the combination of the input that minimizes the absolute value of the error and the estimation method are quantitatively determined. The input image and the quantitative value calculation algorithm for calculating the value image are determined. Here, the calculation of the T2 * value is taken as an example, but other quantitative values can be estimated by the same method.

  When calculating the T2 value as the quantitative value, the fact that the signal intensity obtained by the imaging method based on the SE (spin echo) method theoretically follows the function of Equation 2 is used. The function in Step 402 is represented by Expression 2, and images picked up by the SE method of two or more types of TE values with TR values fixed in Step 404 are set as input candidates.

  When calculating the T1 value as a quantitative value, the fact that the signal value after 180 ° pulse irradiation theoretically follows Equation 3 is used in an imaging method based on the IR (inversion recovery) method. The inversion time is TI.

  The function in Step 402 is represented by Expression 3, and images captured by a plurality of IR methods in which the TI values are changed in Step 404 are set as input candidates.

  The T1ρ value, which is a quantitative value, utilizes the fact that the signal value after irradiation of the spin lock pulse theoretically follows Equation 4 in the imaging method in which the spin lock pulse is irradiated before imaging. The irradiation time of the spin lock pulse is TSL.

  The function in Step 402 is represented by Equation 4, and a plurality of images captured by changing the TSL value in Step 404 are set as input candidates.

  The position and shape of the analysis ROI are acquired from the DICOM information of the quantitative value image. As a result of ROI analysis, numerical data information may be lost from past image groups. For example, when numerical information is stored as an image in DICOM format so that it can be handled in the same manner as other images. Therefore, ROI analysis is performed from the quantitative value image and ROI information. Statistics obtained by analysis include, for example, area, number of pixels, maximum value, minimum value, average value, standard deviation, and the like of pixel values. The inspection information of the past image group acquired by these methods is stored in the memory 302.

  Next, step 203 in FIG. 2 will be described. In step 203, the inspection information obtained from the past image group and stored in the memory 302 is read out to the CPU 8 and applied to the current inspection. The inspection information to be applied includes measurement conditions, positioning information, an input image and calculation algorithm for calculating a quantitative value image, and the position and shape of the analysis ROI.

  However, some information to be applied cannot be applied as it is. Some measurement conditions as examination information obtained from past image groups are specific to the MRI apparatus (manufacturer), such as an imaging sequence name. The conditions specific to the MRI apparatus cannot be applied to the current examination when the used MRI apparatus is different from that of the past examination. Therefore, for information dependent on the apparatus, a correspondence table for each MRI apparatus is held in advance on the magnetic disk 18. When applying the inspection information of the past image group, this correspondence table is read out to the CPU 8, and converted into inspection information corresponding to the MRI apparatus to be inspected this time and applied. That is, when determining the current inspection information using the inspection information acquired by the processing unit, if the acquired inspection information is not applicable to the device used this time, conversion is performed based on the correspondence table for the inspection information depending on the device. And apply.

  In addition, there may be a case where the same condition of the past image group cannot be applied due to a shortage of a part of the measurement condition as inspection information or restriction of the apparatus. In this case, the recommended conditions of the MRI apparatus used this time shall be applied. That is, when the processing unit uses the acquired inspection information to determine the current inspection information, if the acquired inspection information is insufficient, the optimal condition of the device used this time corresponding to the insufficient inspection information Apply.

  In addition, regarding the positioning information as the examination information and the position of the analysis ROI, if the information obtained from the past image group is applied to the examination as it is, it is set to the same position with respect to the subject who is the subject. Not necessarily. This is because the position information is held in a coordinate system based on the MRI apparatus, so if the patient's posture is different between the previous examination and the current examination, the position of the subject relative to the MRI apparatus is Because it is different. Here, for example, a known technique described in Patent Document 1 is used. Note that the inspection information updated when applied to the current inspection is stored in the memory 302. That is, when determining the current examination information using the examination information acquired by the processing unit, adjustment of the current examination information is performed in consideration of the difference in the position of the subject.

  In step 204, the user adjusts the inspection information applied in step 203. That is, without using a part of the examination information, for example, it is possible to change to the recommended condition of the MRI apparatus used in the examination this time, or to change the combination of the input images for calculating the quantitative value image. The inspection information is adjusted using, for example, the trackball of the operation unit 25, the mouse 23, or the keyboard 24. After the corresponding inspection information is changed by the operation unit 25, the inspection information of the CPU 8 is updated. The inspection information adjusted and finally determined is stored in the memory 302.

  In step 205, an inspection is performed according to the final inspection information determined in step 204, and the current image is acquired. In step 206, after the current image group is obtained by performing the inspection, the current image group is compared with the past image group. For comparison between the past image group and the current image group, for example, the user interface 501 shown in FIG.

  Here, an example of the user interface 501 in FIG. 5 will be described. The user interface 501 is displayed on the screen of the display 20. The user interface 501 includes a past image group list 502 (a) and a current image group list 502 (b), a detailed display unit 503 (a) for displaying a part of past image groups or examination information, and Detail display section 503 (b) that displays a part of the current image or inspection information of the current image group, and which information of “measurement condition”, “positioning”, “image”, and “ROI analysis” is displayed in these detail display sections Information selection section 504, display setting section 505 for setting the display of each information, and external output section 506 for instructing external output for storing the presented information. Each will be described in detail below.

  The past image group list 503 (a) and the current image group list (b) are a list of past images and past images and current images included in the current image group. When the user selects a desired image through the operation unit 25, the selected list, for example, “T2 * Map” is highlighted, and detailed information about the selected image is displayed in the detail display units 503 (a) and 503 (b). . If one of the images in the past image group list 503 (a) or the current image group list 503 (b) is selected, the corresponding images in the other list are selected at the same time.

The detail display sections 503 (a) and 503 (b) display detailed information of the images selected in the past image group list 502 (a) or the current image group list 502 (b). The type of detailed information to be displayed is determined based on selection by the information selection unit 504. Further, detailed information is displayed based on the setting of the display setting unit 505.
The information selection unit 504 determines inspection information to be displayed on the detail display units 503 (a) and 503 (b), and includes “measurement conditions”, “positioning”, “image”, and “ROI analysis”. When the user selects the operation unit 25, the selected item, for example, “image” is highlighted, and the corresponding information is displayed in 503 (a) and 503 (b).

  The display setting unit 505 performs display settings according to the item selected by the information selection unit 504. Each setting item is reflected in the detail display sections 503 (a) and 503 (b) when the user changes the setting by the operation section 25. Each item of the information selection unit 504 and the contents of the display setting unit 505 corresponding to each item will be described later.

  The external output unit 506 has a function of outputting the displayed comparison information externally. When the button 506 is pressed, the data is saved in the magnetic disk 18 or the like. Examples of the output format of the selected image information include DICOM format, HTML format, and text format.

  Next, display examples of the display setting unit 505 and the detail display units 503 (a) and 503 (b) corresponding to items that can be selected by the information selection unit 504 will be described with reference to FIG. FIG. 6 shows a display example relating to the measurement condition which is the inspection information of the present embodiment. The detailed display sections 503 (a) and 503 (b) display the measurement conditions of the past image group and the current image group, respectively. The measurement condition display of the current image group can display the measurement conditions before and after the adjustment changed by the user in step 204, respectively. In FIG. 6, the tab display 601 is realized by switching between before and after adjustment.

  When the difference 603-1 between the apparatuses is selected in the display setting 505, the items converted in step 203 that are conditions unique to MRI, such as 602 (a) -1 and 602 (b) -1, are highlighted. In this example, characters are highlighted by being underlined. When automatic adjustment 603-2 is selected, the current image group is inspected due to lack of conditions in the past image group or restrictions on the devices of the current image group as in 602 (a) -2 and 602 (b) -2. Items that automatically apply the recommended conditions of the MRI apparatus that performed the above are highlighted by a method different from 602 (a) -1 and 602 (b) -1. In this example, highlighting is performed by changing the background color of the item.

  When manual change 603-3 is selected, the item changed by the user in step 204 is different from 602 (a) -1, 602 (b) -1, 602 (a) -2, 602 (b) -2. Highlight with method. In this example, as exemplified by “TR”, items are highlighted by being displayed in bold. Tab display 601 and display settings 505 603-1, 602-2, and 603-3 allow the user to make interactive changes from the operation unit 25. After the change, the changed information is notified to the CPU 8, and the changed state is displayed. Is displayed on the display 20 as a part of the user interface 501.

  FIG. 7 shows a display example relating to positioning, which is an item of the information selection unit 504 of the present embodiment. The detailed display sections 503 (a) and 503 (b) display positioning information as inspection information for the past image group and the current image group. In the positioning display of the current image group, similarly to the measurement condition display, the pre-adjustment and post-adjustment positioning information changed by the user on the tab display 601 in step 204 can be displayed. In the display areas 702 (a) and 702 (b), the positioning images of the images to be displayed are displayed, and the corresponding positions are indicated by solid lines. When the display setting unit 505 displays the difference 703 before and after adjustment, the difference in position of the current image group before and after adjustment is displayed. FIG. 7 shows an example in which the position after adjustment is indicated by a solid line and the position before adjustment is indicated by a broken line. 703 enables an interactive change by the user from the operation unit 25, notifies the changed information to the CPU 8 after the change, and displays the changed state as a part of the user interface 501 on the display 20.

  FIG. 8 shows a display example related to the image of this embodiment. FIG. 8 shows an example in which the past image 801 (a) and the current image 801 (b) and their difference image 802 are displayed in order to facilitate comparison between the past image and the current image of the current examination. When the position correction 803-1 is selected by the display setting unit 505, the position of the current image 801 (b) with respect to the past image 801 (a) is corrected and displayed. If the inspection information of the past image applied in step 203 is used as it is, it can be considered that the positions of both images match, but the positions of both images do not match, such as when the user adjusts the position in step 204. Therefore, a means for correcting the corresponding past image and position after acquisition of the current image group is provided. For the position correction, a known positioning technique such as pattern matching is used.

  When the image to be displayed is a quantitative value image, a difference in the quantitative value of the tissue occurs due to a difference in magnetic field strength or static magnetic field uniformity of the MRI apparatus. Therefore, when 803-2 excluding the influence of the apparatus difference is selected, the past image 801 (a) and the current image 801 (b) are displayed excluding this influence. When it is assumed that the past image group and the current image group are acquired by the same MRI apparatus, the quantitative values can be regarded as matching if there is no organization or the like in the tissue.

FIG. 9 shows a method of using this to exclude the influence of the difference in quantitative values. In step 901, a region of a uniform quantitative value that is not an observation target and is uniform in the past image 801 (a) is extracted manually or semi-automatically. As a method of manually extracting, for example, there is a method of designating an outline of a region to be extracted from the past image 801 (a) by the operation unit 25. As a semi-automatic extraction method, for example, a method of specifying an outline of a region including a region to be extracted from the past image 801 (a) with the operation unit 25 and determining a region equal to or larger than a value within the region as a desired region and so on. In step 902, an area corresponding to the current image 801 (b) of the area extracted in step 901 is determined. In step 903, an average value ave ₉₀₃ of the quantitative values is calculated for a part of the past image 801 (a) extracted in step 901. In step 904, the average value ave ₉₀₄ of the quantitative values is also calculated for some regions of the current image 801 (b) extracted in step 2 as in step 903. In step 905, the ratio S of the average value of the quantitative values calculated in step 903 to the average value of the quantitative values calculated in step 904 is calculated by the following equation.

  In step 906, the ratio S calculated in step 905 is multiplied by the quantitative value for each pixel of the image displayed in the current image 801 (b). In step 907, the image display of the current image 801 (b) is updated with the result obtained in step 906.

  When the difference display 803-3 is selected, a difference image between the past image 801 (a) and the current image 802 (b) is displayed on the difference image 802. For example, when the user manually designates with the operation unit 25, the display may be changed so that the user can easily observe only the region of interest in the image. Further, when the difference display 803-3 is not selected, the display of the difference image 802 disappears to make it easier to observe the past image 801 (a) and the current image 801 (b), and the screen configuration as shown in FIG. It may be changed.

  FIG. 10 shows a display example related to ROI analysis, which is inspection information of this embodiment. As shown in the figure, the past image 1001 (a) and the current image 1001 (b) which is the image of the current examination are displayed, and the ROI 1004-1 and the ROI 1004-2 are superimposed and displayed thereon. FIG. 10 shows an example in which analysis is performed for two ROIs 1004-1 and ROI 1004-2. When the user selects the area 1005 with the operation unit 25 and determines the ROI to display the results, the respective ROI analysis results are displayed in the areas 1002 (a) and 1002 (b). Further, by highlighting the corresponding ROI in the past image 1001 (a) and the current image 1001 (b), the user can easily grasp the correspondence. In the example of FIG. 10, the ROI is displayed with a bold line. As described above, when the processing unit displays the current image and the past image in a comparable state, the user's convenience can be improved by highlighting the difference between the current image and the past image.

  The ROI can be newly added by the user after the inspection is completed. As a method of adding ROI, for example, when the contour of the region to be analyzed of the past image 1001 (a) or the current image 1001 (b) is specified by the operation unit 25, there is a method of adding the ROI at the same position of the other image. . Selecting position correction 1003-1 and 1003-2 excluding the effects of equipment differences to exclude the effects of misalignment between examinations and differences in quantitative values due to differences in MRI equipment will result in position correction 803-1 and equipment differences, respectively. The operation is the same as that of 803-2 excluding the influence of. When the difference display 1003-3 is selected, the ROI statistical result relating to the difference in the quantitative value between examinations is displayed.

  The above is an example when comparing two examinations, but three or more examinations may be compared. At that time, as a method for facilitating comparison between examinations for the user, a cine display in a time series direction for image display, a graph display with time as a horizontal axis and a quantitative value as a vertical axis for ROI statistics, etc. Conceivable.

  By realizing the present embodiment described above, even when acquired by different apparatuses, it is possible to compare and evaluate image groups including quantitative value images acquired by examinations with different dates and times from the same evaluation viewpoint.

  Next, Embodiment 2 in which examination information obtained by analyzing a past image group is used as statistical data will be described with reference to FIG. The difference from the first embodiment is that the examination information obtained by analyzing the past image group is stored in the external server 1101 and can be used as statistical data. Hereinafter, only different portions will be described, and description of the same portions will be omitted.

  In step 202 of FIG. 2, the past image group is analyzed to obtain examination information. In the first embodiment, it is stored in the memory 302, and is used only for the application of the inspection information to the current image group and the comparison of the image group. In the second embodiment, the obtained inspection information and the image group are simultaneously stored in the memory 302. The same is also stored in the mass storage device 1102 in the server B 1101 connected to the hospital network or the Internet 303. All examination information and past image groups are stored in the same mass storage device 1102 so that all information stored in the mass storage device 1102 can be used.

  As a usage method, for example, the ROI statistics of the current image group in step 206 are compared with a part of the data stored in the server B 1101. Extract information such as the age and sex of the subject who is the subject of the test from which the current image group was acquired, the type of the quantitative value image on which the ROI analysis was performed, and at least one of these conditions matches A plurality of examination information and quantitative value images to be acquired are acquired from the server B 1101 and read into the CPU 8 via the hospital network or the Internet 303. The examination information and the quantitative value image stored in the memory 302 are displayed on the display 20 together with the current image group.

  FIG. 12 shows a configuration example of the screen of the apparatus according to the present embodiment. The summary display unit 1201 displays a summary of statistical data extracted from the server B 1101. For example, a quantitative value image extracted from data acquired from an external server is calculated as statistical data. Here, a histogram with the horizontal axis representing the quantitative value obtained by the ROI analysis is illustrated. The statistical data display unit 1202 displays numerical information of statistical data. Examples of numerical information include the average value and standard deviation of quantitative values, and the minimum and maximum values in statistical data. The image display unit 1203 displays an image used for statistical data and corresponding examination information.

  When 1204 excluding the influence of the apparatus difference is selected, the quantitative value of the quantitative value image included in the statistical data is converted by the same method as in FIG. 9, and the influence of the apparatus difference is excluded. However, since there are multiple quantitative value images included in the statistical data, if the area to be extracted in step 901 is determined only for one image, operations such as reflecting the same conditions to other images can be simplified. It can also be done. Also, when the display of the current examination position 1205 is selected, the portion of the statistical data extracted from the server B 1101 and the position corresponding to the quantitative value analyzed in the current examination are as shown in the example of the graph 1206. By displaying, it is possible to easily grasp in which part in the statistical data the quantitative value image of the current current image group is located.

  According to the second embodiment described above, the current image group is obtained by calculating and displaying the position of the quantitative value image of the current image in the statistical data distribution obtained from the quantitative value image acquired by the processing unit from the external server. It is possible to compare the quantitative value image inside with the statistical data.

  Next, the MRI apparatus of Example 3 will be described. The difference from the first and second embodiments is that standard inspection information and image groups prepared in advance are used instead of past image groups. Hereinafter, only different portions will be described, and description of the same portions will be omitted.

  In this embodiment, the standardized examination information and image group are referred to as a standard template. The standard template is the measurement condition and positioning information for each image, the image obtained by applying the condition, the input image for calculating the quantitative value image, the quantitative value calculation algorithm, and the statistical value from the quantitative value image. It shall include the position and shape of the analysis ROI for calculation. A standard template is created for each apparatus and for each examination site. For example, in the configuration of FIG. 11, the standard template is stored in advance in the mass storage device 1102 in the server B 1101 connected to the Internet 303.

  In the first embodiment, the examination information is acquired from the past image group in steps 201 and 203, but in the third embodiment, a standard template corresponding to a desired apparatus and examination site is obtained from a server connected to the Internet 303 and read into the CPU 8. In step 203, the inspection information to be applied to the inspection in the first embodiment is acquired from the past image group, but in the third embodiment, the inspection information attached to the standard template is applied.

  By preparing a standard template for each apparatus and storing it in the server 1101 or the like via the Internet 303, it can be used from any facility.

  That is, according to the present embodiment, from the external server that stores the inspection information and image standardized by the processing unit, the inspection information and image of a desired condition are acquired from the standardized inspection information and image, and the acquired desired condition is acquired. Based on the inspection information and images, the current inspection information can be determined, which reduces the burden of closely examining imaging conditions and inspection details for each facility, and makes it possible to easily perform equivalent inspections at any facility It becomes possible.

  As described above, various implementations of the present invention that can compare a plurality of examinations acquired with different date and time or different apparatuses for MRI examinations including quantitative value images obtained by imaging T1, T2, T2 * values, etc. Although examples have been described, the present invention is not limited to the above-described embodiments, and includes various modifications. For example, the above-described embodiments have been described in detail for better understanding of the present invention, and are not necessarily limited to those having all the configurations described.

  Further, a part of the configuration of one embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of one embodiment. Further, it is possible to add, delete, and replace other configurations for a part of the configuration of each embodiment.

  Further, the above-described configurations, functions, processing units, and the like have been mainly described in the case where they are realized by software by creating a program that realizes part or all of them. Needless to say, it may be realized by hardware.

DESCRIPTION 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 (Transmission Coil)
14b High frequency coil (receiver coil)
15 signal amplifier 16 quadrature detector 17 A / D converter 18 magnetic disk 19 optical disk 20 display 21 ROM
22 RAM
23 Trackball or mouse 24 Keyboard 25 Operation unit 301 Console 302 Memory 303 Hospital network or Internet 501 User interface 502 List of images 503 Detailed display unit 504 Information selection unit 505 Display setting unit 506 External output unit 1101 External server 1102 Large capacity Storage device 1201 Summary display unit 1202 Statistical data display unit 1203 Image display unit

Claims (14)

A magnetic resonance imaging (MRI) apparatus,
A uniform static magnetic field in a space that accommodates the subject, a magnetic field generation unit that generates a gradient magnetic field superimposed on the static magnetic field, and a nuclear magnetic resonance generated from the subject by irradiating the subject with a high-frequency magnetic field ( Hereinafter, a detection unit for detecting the NMR) signal, and a processing unit for imaging the detected NMR signal,
The processor is
Obtain past examination information from past images obtained with different date and time and different devices,
Using the acquired inspection information, determine the current inspection information,
Displaying the current image acquired based on the determined examination information and the past image in a comparable state;
An MRI apparatus characterized by that. The MRI apparatus according to claim 1,
The past image and the current image are quantitative value images,
An MRI apparatus characterized by that. The MRI apparatus according to claim 2,
The inspection information acquired by the processing unit is measurement conditions and positioning information of the past image, a calculation method of the quantitative value image, and a position shape of ROI for analyzing the quantitative value image.
An MRI apparatus characterized by that. The MRI apparatus according to claim 2,
The processor is
In order to acquire the examination information from the acquired past image, an input and a quantitative value calculation algorithm are estimated from the quantitative value image of the past image.
An MRI apparatus characterized by that. The MRI apparatus according to claim 1, wherein the processing unit includes:
When determining the inspection information of this time using the acquired inspection information,
When the acquired inspection information cannot be applied to the device used this time, it is converted and applied based on the correspondence table for the inspection information depending on the device.
An MRI apparatus characterized by that. The MRI apparatus according to claim 1,
The processor is
When determining the inspection information of this time using the acquired inspection information,
When the acquired inspection information lacks information, the optimum condition of the device used this time corresponding to the insufficient inspection information is applied.
An MRI apparatus characterized by that. The MRI apparatus according to claim 1,
The processor is
When determining the inspection information of this time using the acquired inspection information,
Taking into account the difference in the position of the subject, adjusting the examination information this time,
An MRI apparatus characterized by that. The MRI apparatus according to claim 1,
The processor is
When displaying the current image and the past image in a comparable state, the difference between the current image and the past image is highlighted.
An MRI apparatus characterized by that. The MRI apparatus according to claim 2,
The processor is
When displaying the current image and the past image in a comparable state,
Displaying the quantitative value image in a state in which the influence of the difference in apparatus between examinations is removed,
An MRI apparatus characterized by that. The MRI apparatus according to claim 1,
The processor is
From the past examination information and the past image stored in the external server,
Obtain data that matches the conditions of the determined inspection information,
The past image of the acquired data and the current image acquired based on the determined examination information are displayed in a comparable state.
An MRI device characterized by that. The MRI apparatus according to claim 10,
The processor is
As data that matches the conditions of the determined examination information, obtain data that matches at least one of age, sex, examination type and part,
An MRI apparatus characterized by that. The MRI apparatus according to claim 11,
The processor is
Calculating a quantitative value image extracted from the data acquired from the external server as statistical data;
An MRI apparatus characterized by that. The MRI apparatus according to claim 12,
The processor is
In the distribution of the statistical data obtained from the quantitative value image obtained from the external server, the position of the quantitative value image of the current image is calculated and displayed.
An MRI apparatus characterized by that. The MRI apparatus according to claim 1,
The processor is
From the external server that stores the standardized examination information and image, obtain the examination information and image of desired conditions from the standardized examination information and image,
Based on the acquired inspection information and image of the desired condition acquired, the current inspection information is determined.
An MRI device characterized by that.

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