JP5378149B2 - MRI apparatus and imaging area setting control program - Google Patents

Description

  The present invention relates to an MRI apparatus and an imaging area setting control program, and in particular, an MRI apparatus and an imaging area for setting an imaging area and an imaging section of image data in the imaging mode based on image data obtained in a pilot imaging mode. The present invention relates to a setting control program.

  Magnetic resonance imaging (MRI) excites nuclear spins in a subject tissue placed in a strong static magnetic field with a high-frequency signal (RF pulse) having the Larmor frequency, and magnetic resonance generated by the excitation. This is an imaging method for generating image data by reconstructing a signal (MR signal).

  An MRI apparatus is an image diagnostic apparatus that generates image data based on MR signals detected from within a living body, and can obtain a lot of diagnostic information such as functional diagnostic information and biochemical information as well as anatomical diagnostic information. As a result, it is indispensable in the field of diagnostic imaging today.

  In such an MRI apparatus, a strong static magnetic field and three gradient magnetic fields orthogonal to each other are applied to the subject in order to give positional information to MR signals generated from the biological tissue of the subject. Magnetic field such as inhomogeneity and non-linearity in static magnetic field and gradient magnetic field applied to subject due to performance limitations of main magnet and static magnetic field power source and gradient magnetic field coil and gradient magnetic field power source that generate static magnetic field An error occurs. And the image data obtained by MRI imaging using such a static magnetic field or a gradient magnetic field has the image distortion resulting from the above-mentioned magnetic field error.

  In order to reduce the image distortion due to such a magnetic field error, intensity distribution data of a static magnetic field and a gradient magnetic field is collected in advance by simulation and measurement, and the pixel of the image data generated by the MRI imaging is used as the intensity distribution described above. There has been proposed a method of collecting high-quality image data in which image distortion is reduced by performing correction based on the data (see, for example, Patent Document 1).

  On the other hand, in MRI imaging, image data (hereinafter referred to as positioning image data) for the purpose of setting the imaging section and imaging area of image data (hereinafter referred to as diagnostic image data) generated in the main imaging mode. Is collected in the pilot shooting mode preceding the main shooting mode. For example, when collecting image data on an axial section perpendicular to the body axis direction of the subject as diagnostic image data in the main imaging mode, the image data is parallel to the body axis direction in the pilot imaging mode performed prior to the main imaging mode. Image data of a sagittal section or coronal section is collected as positioning image data for setting an imaging section, and image data of an axial section is collected as positioning image data for setting an imaging area.

  However, when the imaging section in the main imaging mode is set using the positioning image data in which the image distortion due to the magnetic field error is corrected by the method described in Patent Document 1, the RF pulse corresponding to the position of the imaging section Since the center frequency of MR and the magnetic resonance frequency of the MR signal generated by the biological tissue in which the imaging section is set do not match, it is not possible to accurately set the imaging section for the subject. For this reason, when setting the imaging section in the main imaging mode using the positioning image data in the pilot imaging mode, the imaging in the main imaging mode is performed based on the positioning image data before the image distortion due to the magnetic field error is corrected. A method of setting a cross section has been proposed (see, for example, Patent Document 2).

JP 2007-159718 A JP 2005-118461 A

  As described above, when collecting diagnostic image data in the main imaging mode, it is necessary to set an imaging region in addition to the above-described imaging cross section based on positioning image data in the pilot imaging mode. When image data of a sagittal section approximately parallel to the body axis direction is collected as diagnostic image data in the main imaging mode, imaging is performed using image data for positioning before image distortion correction in the sagittal section acquired in the pilot imaging mode. The conventional method for setting the area has a problem that the imaging area cannot be set accurately due to the image distortion of the positioning image data.

  The present invention has been made in view of the above-described problems, and its purpose is to obtain positioning image data before correction of image distortion caused by magnetic field inhomogeneity or non-linearity. Use this to set the imaging section of the diagnostic image data, and to set the imaging area of the diagnostic image data using the positioning image data corrected for image distortion. An object of the present invention is to provide an MRI apparatus and an imaging region setting control program that can be set.

  In order to solve the above problems, the MRI apparatus of the present invention according to claim 1 collects the subject to which a static magnetic field and a gradient magnetic field are applied by performing MRI imaging in a pilot imaging mode preceding the main imaging mode. In an MRI apparatus that sets an imaging section and an imaging area in the main imaging mode based on positioning image data in a plurality of cross sections that intersect each other, the MR data collected by the MRI imaging is reconstructed and the plurality of sections The first positioning image data for at least one of the reconstruction processing means for generating the first positioning image data and the plurality of first positioning image data generated in the plurality of cross sections. Image distortion correcting means for generating image data for second positioning by correcting image distortion caused by magnetic field error of data Imaging area setting means for setting an imaging area in the main imaging mode based on the second positioning image data generated in a desired section, and the first generated in a section different from the desired section. An imaging section setting means for setting an imaging section in the main imaging mode based on the positioning image data is provided.

  According to a seventh aspect of the present invention, there is provided an imaging region setting control program according to the present invention, which is obtained by performing MRI imaging in a pilot imaging mode preceding a main imaging mode on a subject to which a static magnetic field and a gradient magnetic field are applied. For the MRI apparatus that sets the imaging section and the imaging area in the main imaging mode based on the positioning image data in the plurality of sections, the MR data collected by the MRI imaging is reconstructed and processed in the plurality of sections. For at least one of the reconstruction processing function for generating the first positioning image data and the plurality of first positioning image data generated in the plurality of cross sections, the first positioning image data An image distortion correction function for correcting image distortion caused by a magnetic field error of the image and generating second positioning image data; A shooting area setting function for setting a shooting area in the main shooting mode based on the second positioning image data generated in the cross section, and the first positioning for generation generated in a cross section different from the desired cross section. A photographing section setting function for setting a photographing section in the main photographing mode based on image data is executed.

  According to the present invention, an imaging cross section of diagnostic image data is set using image data for positioning before image distortion generated due to non-uniformity or non-linearity of a magnetic field is corrected, and image distortion By setting the imaging region of the diagnostic image data using the positioning image data corrected in the above, a desired imaging section and imaging region can be set with high accuracy. For this reason, it is possible to collect image data effective for diagnosis without being significantly affected by the error of the magnetic field.

The figure for demonstrating the sagittal cross section with respect to a test object, and a coronal cross section. 1 is a block diagram showing the overall configuration of an MRI apparatus in an embodiment of the present invention. In the same embodiment, when the image data of the sagittal section is collected as diagnostic image data, it is based on the sagittal image data for positioning after image distortion correction and the coronal image data for positioning before image distortion correction collected in the pilot imaging mode. The figure which shows the imaging | photography area | region and imaging | photography cross section of the said diagnostic image data set by this. FIG. 6 is a diagram for explaining the effectiveness in the case where the setting of the imaging section in the main imaging mode of the embodiment is performed using the positioning image data before image distortion correction. 7 is a flowchart showing a procedure for setting a photographing section and a photographing region performed for positioning image data in pilot photographing mode in the embodiment. As a modification of the embodiment, when coronal cross-sectional image data is collected as diagnostic image data, positioning coronal image data after image distortion correction and positioning sagittal image before image distortion correction collected in the pilot imaging mode The figure which shows the imaging | photography area | region and imaging | photography cross section of the said diagnostic image data set based on data.

  Embodiments of the present invention will be described below with reference to the drawings.

  In the MRI apparatus of the present embodiment described below, for example, in the pilot imaging mode for setting the imaging section and the imaging area when generating the image data of the sagittal section as diagnostic image data in the main imaging mode, the image distortion Sagittal image data for positioning before correction (sagittal image data before correction) and coronal image data for positioning before image distortion correction (coronal image data before correction) are generated, and magnetic field errors (for example, static image data) of the sagittal image data before correction are generated. New sagittal image data for positioning (corrected sagittal image data) is generated by correcting image distortion caused by magnetic field inhomogeneity and gradient magnetic field non-linearity. Then, an imaging region of diagnostic image data is set based on the corrected sagittal image data, and an imaging cross section of the diagnostic image data is set based on the pre-correction coronal image data.

  In the following description, as shown in FIG. 1, the imaging region for the sagittal image data in the main imaging mode based on the corrected sagittal image data Dsc and the pre-correction coronal image data Dcx of the subject 150 acquired in the pilot imaging mode, and Although the case of setting an imaging section is described, the present invention is not limited to this. For example, an imaging area and an imaging section for coronal image data in the main imaging mode are set based on corrected coronal image data and sagittal image data before correction. Alternatively, the photographing region and the photographing section for the axial image data in the main photographing mode may be set based on the corrected axial image data and the sagittal image data before correction or the coronal image data before correction.

(Device configuration)
The configuration and functions of the MRI apparatus in the embodiment of the present invention will be described with reference to FIGS. However, FIG. 2 is a block diagram showing the overall configuration of the MRI apparatus in the present embodiment.

  An MRI apparatus 200 shown in FIG. 2 includes an MR unit 1 and a gradient magnetic field generating unit 2 that generate a magnetic field with respect to the subject 150, and an MR pulse generated by irradiating the subject 150 with RF pulses. A transmission / reception unit 3 that detects a signal, a top plate 4 on which the subject 150 is placed, and a top plate moving mechanism unit 5 that moves the top plate 4 in the body axis direction (z-axis direction) of the subject 150 are provided. .

  In addition, the MRI apparatus 200 transmits and receives the transmission / reception unit 3 in the pilot imaging mode for collecting positioning image data performed on the subject 150 and the MRI imaging in the main imaging mode for collecting diagnostic image data. Is reconstructed to generate positioning image data before image distortion correction (hereinafter referred to as pre-correction image data), and magnetic field inhomogeneities generated in the pre-correction image data. And image data generation unit 6 that generates positioning image data (hereinafter referred to as corrected image data) in which image distortion due to nonlinearity is corrected, and correction of the pilot imaging mode generated by image data generation unit 6 The display unit 8 for displaying the previous image data and the corrected image data, as well as the diagnostic image data in the main imaging mode, input of object information, and selection of the imaging mode. , MR signal acquisition conditions including pulse sequence, setting of image data generation conditions and image data display conditions, setting of imaging section for uncorrected image data, setting of imaging area for corrected image data, input of various command signals A magnetic field information storage unit 10 in which magnetic field information (that is, magnetic field strength distribution data or magnetic field error distribution data) of a static magnetic field and a gradient magnetic field applied to the subject 150 is stored in advance, and an MRI The control part 15 which controls each unit mentioned above in the apparatus 200 is provided.

  The static magnetic field generation unit 1 includes a main magnet 11 composed of a normal conducting magnet or a superconducting magnet, and a static magnetic field power source 12 for supplying current to the main magnet 11, and is disposed in a photographing field in the center of the gantry (not shown). A strong static magnetic field is formed on the subject 150. The main magnet 11 may be constituted by a permanent magnet.

  On the other hand, the gradient magnetic field generator 2 is a gradient magnetic field coil that forms a gradient magnetic field in the body axis direction (z-axis direction in FIG. 1) of the subject 150 and the x-axis direction and the y-axis direction orthogonal to the body axis direction. 21 and a gradient magnetic field power supply 22 for supplying a pulse current to each of the gradient magnetic field coils 21.

  The gradient magnetic field coil 21 and the gradient magnetic field power source 22 add position information to the imaging field in which the subject 150 is placed based on the sequence control signal supplied from the control unit 15. That is, the gradient magnetic field power supply 22 controls the pulse current supplied to the gradient magnetic field coil 21 in the x-axis direction, the y-axis direction, and the z-axis direction based on the sequence control signal supplied from the control unit 15 to thereby change the direction of each direction. To form a gradient magnetic field. The gradient magnetic fields in the x-axis direction, the y-axis direction, and the z-axis direction are combined to form slice selection gradient magnetic fields, phase encode gradient magnetic fields, and frequency encode (read) gradient magnetic fields that are orthogonal to each other. The gradient magnetic field is applied to the subject 150 while being superimposed on the static magnetic field formed by the main magnet 11.

  Next, the transmission / reception unit 3 irradiates the subject 150 with an RF pulse and detects the MR signal generated from the subject 150, and the transmission unit 32 and the reception unit 33 connected to the transmission / reception coil 31. I have.

  The transmission unit 32 has a function of supplying a pulse current to the transmission / reception coil 31 in a pilot imaging mode for collecting positioning image data and a main imaging mode for collecting diagnostic image data. It has a reference signal generator, a modulator, a power amplifier, and the like. The reference signal generator generates a reference signal having the same frequency as the magnetic resonance frequency (Larmor frequency) determined by the static magnetic field strength of the main magnet 11, and the modulator generates a predetermined selective excitation of the reference signal. A pulse current is generated by modulating the waveform. The obtained pulse current is supplied to the transmission / reception coil 31 via the power amplifier, and the subject 150 is irradiated with RF pulses.

  On the other hand, the receiving unit 33 performs intermediate frequency conversion, phase detection, low frequency amplification, filtering, A / D conversion, and the like on the MR signal generated in the subject 150 irradiated with the RF pulse and detected by the transmission / reception coil 31. Signal processing.

  Next, the top plate 4 is slidably attached in the body axis direction (z-axis direction) of the subject 150 on the upper surface of a bed (not shown), and the subject 150 placed on the top plate 4 is moved in the z-axis direction. By moving it, the imaging target region is set at a desired position in the imaging field. On the other hand, the top plate moving mechanism unit 5 is attached to, for example, an end portion or a lower portion of the bed, and generates a drive signal for moving the top plate 4 based on a top plate movement control signal supplied from the control unit 15. To do. Further, a wide range of positioning image data and diagnostic image data can be collected by performing MRI imaging at predetermined intervals while sequentially moving the top 4 in the body axis direction of the subject 150.

  On the other hand, the image data generation unit 6 includes a data storage unit 61 and a high-speed calculation unit 62. The data storage unit 61 includes an MR data storage unit 611 that stores a plurality of MR signals collected in time series as MR data by sequentially updating the phase encoding of the gradient magnetic field. 62 pre-correction image data generated by the reconstruction processing unit 621 reconstructing the MR data, and corrected image data newly generated by correcting the image distortion of the pre-correction image data by the image distortion correction unit 622. An image data storage unit 612 for storing is provided.

  In the image data storage unit 612, the pre-correction image data in the pilot imaging mode generated by the reconstruction processing unit 621 of the high-speed calculation unit 62 and the MR data supplied from the MR data storage unit 611 are generated and the main imaging. The pre-correction diagnostic image data of the mode is stored, and the image distortion correction unit 622 of the high-speed calculation unit 62 supplies the image data before correction and the pre-correction diagnostic image data supplied from the reconstruction processing unit 621. The correction image data in the pilot imaging mode newly generated by correcting the distortion and the image data for correction diagnosis in the main imaging mode are stored.

  On the other hand, the high-speed calculation unit 62 of the image data generation unit 6 includes a reconstruction processing unit 621 and an image distortion correction unit 622. The reconstruction processing unit 621 reads MR data collected in the pilot imaging mode or the main imaging mode and stored in the MR signal storage unit 611, performs image reconstruction processing by two-dimensional Fourier transform, and performs pre-correction image data and image data. Image data for diagnosis before distortion correction is generated. The obtained pre-correction image data and pre-correction diagnostic image data are supplied to the image distortion correction unit 622, and the pre-correction image data is stored in the image data storage unit 612.

  Next, the image distortion correction unit 622 performs image distortion caused by a magnetic field error included in the pre-correction image data in the pilot imaging mode and the pre-correction diagnostic image data in the main imaging mode generated by the reconstruction processing unit 621, which will be described later. It has a function of correcting based on magnetic field information (that is, magnetic field intensity distribution data or magnetic field error distribution data) supplied from the magnetic field information storage unit 10, and includes an arithmetic processing unit (not shown).

  An image distortion correction method performed by the arithmetic processing unit of the image distortion correction unit 622 will be described. When correcting the image distortion, the arithmetic processing unit first calculates an image distortion amount corresponding to the magnetic field information supplied from the magnetic field information storage unit 10 for each pixel of the pre-correction image data, for example, a magnetic field error in the z direction. Is generated, the image distortion amount Δz in the z direction is calculated based on the error amount and the gradient angle of the gradient magnetic field with respect to the z direction. Next, based on the obtained image distortion amount Δz, the pixel value of the pixel of the pre-correction image data is replaced with the pixel value of a pixel that is separated from the pixel by Δz in the z direction. Then, the image distortion caused by the magnetic field error can be corrected by performing such pixel value replacement on all the pixels constituting the uncorrected image data.

  Next, the display unit 8 includes a display data generation unit, a data conversion unit, and a monitor (not shown), and displays various image data generated by the image data generation unit 6. That is, when displaying the positioning image data collected by the MRI imaging in the pilot imaging mode, the display data generation unit supplies the pre-correction image data and the correction image data supplied from the image data storage unit 612 of the image data generation unit 6. Is converted into a predetermined display format to generate display data, and the data conversion unit performs a conversion process such as D / A conversion or television format conversion on the display data generated by the display data generation unit and outputs the display data to the monitor. indicate.

  On the other hand, when displaying diagnostic image data in the main imaging mode, the display data generation unit performs main imaging for the imaging region set based on the above-described corrected image data and the imaging cross section set based on the pre-correction image data. Diagnostic image data (corrected diagnostic image data) after image distortion correction obtained by reconstructing MR signals obtained by MRI imaging in the mode is converted into a predetermined display format and then supplemented with subject information and the like Display data is generated by adding information. The data conversion unit performs a predetermined conversion process on the display data and displays it on the monitor.

  Next, the input unit 9 is connected to the display unit 8 via the control unit 15 to form an interactive interface. Then, various input devices such as a display panel, a switch, a keyboard, and a mouse are provided on the console, and a shooting region in the main shooting mode is set based on the corrected image data displayed on the monitor of the display unit 8 in the pilot shooting mode. An imaging area setting function 91 and an imaging section setting function 92 for setting an imaging section in the main imaging mode based on pre-correction image data displayed on the monitor are provided. Also, input of subject information, selection of imaging mode, setting of MR signal acquisition conditions in pilot imaging mode and main imaging mode, setting of image data generation conditions and image data display conditions, and input of various command signals, etc. This is performed using the display panel or the input device described above.

  Next, the setting of the photographing area for the corrected image data and the setting of the photographing section for the pre-correction image data will be described with reference to FIG. FIG. 3A shows image data (diagnostic sagittal image data) Ds collected in the sagittal section of the subject 150 as diagnostic image data in the main imaging mode. On the other hand, FIG. 3B shows the imaging region As of the diagnostic sagittal image data set for the corrected sagittal image data Dsc collected in the pilot imaging mode, and FIG. 3C shows the pilot imaging. The imaging | photography cross section Sc of the sagittal image data for a diagnosis set with respect to the coronal image data Dcx before correction | amendment collected in the mode is shown. That is, the imaging region of the diagnostic image data is performed using the corrected image data collected in the same cross section as the diagnostic image data, and the imaging cross section of the diagnostic image data is orthogonal to the diagnostic image data. This is performed using pre-correction image data collected at the cross section.

  Next, with reference to FIG. 4, description will be given of the effectiveness of setting the imaging section when generating diagnostic image data in the main imaging mode using the pre-correction image data.

  In the following, for the sake of easy understanding, the subject 150 is simulated by a plurality of cylinders having a radius a arranged at intervals d in the y-axis direction and the z-axis direction. FIG. 4A shows a sagittal cross section of the subject 150 parallel to the yz plane in which a cylindrical cross section is two-dimensionally arranged in the y-axis direction and the z-axis direction, for example. FIG. 4C shows pre-correction image data and corrected image data collected by MRI imaging of this sagittal section.

  However, the uncorrected image data in FIG. 4B shows image distortion when a magnetic field error occurs in the y-axis direction (that is, the original image information indicated by the broken line is shifted in the y direction by the magnetic field error). Have. Then, corrected image data having a true shape as shown in FIG. 4C can be obtained by correcting the image distortion of the image data before correction.

  Yz obtained when the photographing section in the main photographing mode is set based on the image information shown in the pre-correction image data (FIG. 4B) and the corrected image data (FIG. 4C). The diagnostic image data perpendicular to the plane is shown in FIGS. 4 (d) and 4 (e).

  For example, the seven cylinders shown in the uppermost part of FIG. 4A are taken as imaging target parts and displayed in a distorted state (that is, shifted in the y-axis direction) in the pre-correction image data of FIG. 4B. When the imaging section Pxa in the main imaging mode is set along the arrangement direction of the circular cylinder cross section, the diagnostic image data in the main imaging mode generated in the imaging section Pxa is as shown in FIG. In addition, it is possible to accurately observe the vertical cross sections of all the cylinders included in the imaging target region (that is, the vertical cross section of the imaging target region).

  In this case, the shift amount in the y-axis direction of the cylindrical cross section in the pre-correction image data corresponds to the magnitude of the magnetic field error, and the position of the imaging cross section corresponds to the center frequency of the RF pulse radiated from the transmission / reception coil 31. . Therefore, as shown in FIG. 4B, the center frequency of the PF pulse and the magnetic resonance in the cylinder are set by setting the imaging section Pxa based on the imaging target portion of the pre-correction image data shifted in the y-axis direction due to the magnetic field error. Since the frequencies can be matched, diagnostic image data in the imaging target region can be collected.

  On the other hand, when the imaging section Pxb in the main imaging mode is set along the cylindrical cross section shown in the corrected image data of FIG. 4C, the center frequency of the PF pulse and the magnetic resonance frequency of the cylinder do not match. Therefore, the image data generated in the imaging section Pxb cannot accurately observe the longitudinal sections of all the cylinders included in the imaging target part as shown in FIG. Therefore, it is desirable to set the imaging section when collecting diagnostic image data in the main imaging mode using the pre-correction image data collected in the pilot imaging mode.

  Next, the magnetic field information storage unit 10 stores the magnetic field information of the static magnetic field and the gradient magnetic field applied to the subject 150 in advance. The magnetic field information in this case may be magnetic field intensity distribution data of the static magnetic field and the gradient magnetic field that the static magnetic field generation unit 1 and the gradient magnetic field generation unit 2 of the MRI apparatus 200 form with respect to the imaging field of the gantry (not shown). Further, magnetic field error distribution data indicating the difference between the actual intensity distribution of the static magnetic field and the gradient magnetic field and the ideal intensity distribution may be used. As a method for generating the magnetic field information, there are a method based on computer simulation and a method based on prior magnetic field measurement using the phantom or the subject 150. In particular, the latter specific method is described in Patent Document 1 already shown. Therefore, detailed description is omitted.

  On the other hand, the control unit 15 includes a main control unit 151, a sequence control unit 152, and a top board movement control unit 153. The main control unit 151 includes a CPU and a storage circuit (not shown) and has a function of controlling the MRI apparatus 200 in an integrated manner. In the storage circuit of the main control unit 151, the subject information input / set / selected in the input unit 9, the MR mode in the imaging mode, the pilot imaging mode, and the main imaging mode, the image data generation condition, and the image Information such as data display conditions, a photographing section for the pre-correction image data, and a photographing region for the corrected image data is stored. On the other hand, the CPU of the main control unit 151, in particular, the magnitude of the pulse current supplied to the gradient magnetic field coil 21 and the transmission / reception coil 31 based on the MR signal collection conditions of the pilot imaging mode and the main imaging mode set in the input unit 9; MR signals are collected by setting the polarity, supply time, supply timing, and the like and supplying them to the sequence control unit 152.

  The sequence control unit 152 includes a CPU and a storage circuit (not shown), temporarily stores the setting information supplied from the main control unit 151 in the storage circuit, and then generates a sequence control signal based on the setting information. The gradient magnetic field power source 22 of the gradient magnetic field generation unit 2 and the transmission unit 32 of the transmission / reception unit 3 are controlled. The top plate movement control unit 153 generates a top plate movement control signal based on the top plate movement instruction signal supplied from the input unit 9 via the main control unit 151 and supplies it to the top plate movement mechanism unit 5.

(Procedure for setting the shooting section and shooting area)
Next, a procedure for setting an imaging section and an imaging area performed in the pilot imaging mode will be described with reference to the flowchart of FIG.

  Prior to pilot imaging of the subject 150, the operator of the MRI apparatus 200 places the subject 150 on the top 4 and then inputs subject information at the input unit 9 and collects MR signals in the pilot imaging mode and the main imaging mode. Conditions, image data generation conditions, image data display conditions, etc. are set. And these input information and setting information are preserve | saved at the memory | storage circuit with which the main control part 151 was equipped (step S1 of FIG. 5).

  Next, the operator selects a pilot shooting mode at the input unit 9 and then inputs a shooting start command (step S2 in FIG. 5). Then, the main control unit 151 of the control unit 15 that has received this command signal supplies sequence information applied to the pilot shooting mode to the sequence control unit 152, and the sequence control unit 152 is based on this sequence information. The generated sequence control signal is supplied to the gradient magnetic field power source 22 of the gradient magnetic field generator 2 and the transmitter 32 of the transmitter / receiver 3 to collect MR signals for the subject 150. The obtained MR signal is stored in the MR data storage unit 611 of the data storage unit 61 as MR data.

  Next, the reconstruction processing unit 621 of the high-speed computing unit 62 reconstructs the above-described MR data read from the MR data storage unit 611 to generate uncorrected image data, and the obtained uncorrected image data is subjected to image distortion. The image data is supplied to the correction unit 622 and stored in the image data storage unit 612 (step S3 in FIG. 5).

  On the other hand, the image distortion correction unit 622 of the high-speed calculation unit 62 receives the pre-correction image data supplied from the reconstruction processing unit 621 and corrects the pre-correction image data based on the magnetic field information read from the magnetic field information storage unit 10. Thus, corrected image data is generated (step S4 in FIG. 5). The obtained corrected image data is stored in the image data storage unit 612 (step S5 in FIG. 5). That is, the image data storage unit 612 stores the pre-correction image data and the corrected image data.

  When the collection and storage of the pre-correction image data and the corrected image data are completed, the display data generation unit of the display unit 8 reads the above-described corrected image data temporarily stored in the display data storage unit 612, and performs a predetermined conversion process. Is displayed on its own monitor (step S6 in FIG. 5).

  On the other hand, the operator who has observed the corrected image data in the pilot shooting mode displayed on the display unit 8 is diagnostic image data in the main shooting mode (that is, substantially parallel to the corrected image data) with respect to the corrected image data. An imaging region for collecting the diagnostic image data in the cross section) is set using the imaging region setting function 91 provided in the input unit 9 (step S7 in FIG. 5).

  Further, the display data generation unit reads out the pre-correction image data stored in the display data storage unit 612 and displays it on its own monitor (step S8 in FIG. 5). The operator observing the pre-correction image data displayed on the display unit 8 performs setting of the imaging cross section in the main imaging mode for the pre-correction image data using the imaging cross-section setting function 92 provided in the input unit 9 ( Step S9 in FIG.

  When the setting of the imaging area and the imaging section in the pilot imaging mode is completed by the procedure described above, the operator performs pilot imaging by selecting the actual imaging mode and inputting the actual imaging mode start command at the input unit 9. End the mode.

  According to the embodiment of the present invention described above, the imaging cross section of the diagnostic image data using the positioning image data before the image distortion generated due to the non-uniformity or non-linearity of the magnetic field is corrected. And setting the imaging area of the diagnostic image data using the positioning image data whose image distortion has been corrected, so that a suitable imaging section and imaging area when collecting diagnostic image data can be obtained with high accuracy. Can be set. For this reason, it is possible to collect image data effective for diagnosis without being significantly affected by the error of the magnetic field.

  In particular, the imaging region of the diagnostic image data is performed using corrected image data collected in the same cross section as the diagnostic image data, and the imaging cross section of the diagnostic image data is orthogonal to the diagnostic image data. By using the pre-correction image data collected in the cross section, it is possible to easily and accurately set the imaging region and the imaging cross section.

  Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments and may be modified. For example, in the above-described embodiment, as shown in FIG. 3, the imaging region and the imaging section for the sagittal image data in the main imaging mode are set based on the corrected sagittal image data and the pre-correction coronal image data collected in the pilot imaging mode. However, the present invention is not limited to this. That is, the shooting area and the shooting section for the coronal image data in the main shooting mode may be set based on the corrected coronal image data and the sagittal image data before correction. Based on the axial image data, a shooting area and a shooting section for the axial image data in the main shooting mode may be set.

  For example, as a modification of the present embodiment, a case where a shooting area and a shooting cross section for the coronal image data in the main shooting mode are set based on the corrected coronal image data and the sagittal image data before correction will be described with reference to FIG.

  FIG. 6A shows diagnostic coronal image data Dc collected for the coronal section of the subject 150 as diagnostic image data in the main imaging mode. On the other hand, FIG. 6B shows the imaging region Ac of diagnostic coronal image data set for the corrected coronal image data Dcc, and FIG. 6C shows the sagittal image data Dsx before correction. The imaging | photography cross section Ss of the diagnostic coronal image data set is shown. That is, the imaging region of the diagnostic coronal image data is performed using the corrected coronal image data collected in the same cross section as the diagnostic coronal image data. This is performed using the uncorrected sagittal image data collected at a sagittal section orthogonal to the coronal image data.

  On the other hand, magnetic field information such as magnetic field intensity distribution data and magnetic field error distribution data used for image distortion correction has been described as being stored in advance in the magnetic field information storage unit 10, but a simulation or magnetic field performed prior to the MRI imaging is described. You may collect by measurement. In this case, by measuring the magnetic field information in a state where the imaging target part of the subject 150 is arranged in the imaging field of the gantry, it is possible to correct image distortion caused by the insertion of the subject 150 together.

  Furthermore, in the above-described embodiment, the case where the imaging region and the imaging cross section in the main imaging mode are set based on one corrected image data and pre-correction image data collected in cross sections orthogonal to each other has been described. When 150 imaging target parts exist in a relatively wide range with respect to the body axis direction, a plurality of correction image data collected at different positions in the body axis direction by the movement of the top plate 4 is combined to wide range correction image data. May be generated, and the shooting region of the main shooting mode may be set based on the wide-range corrected image data.

  In the above-described embodiment, the case where MRI imaging is performed using a coil for both transmission and reception that enables irradiation of an RF pulse to the subject 150 and reception of an MR signal generated by the subject 150 has been described. Alternatively, a receiving coil and a receiving-only coil may be used.

DESCRIPTION OF SYMBOLS 1 ... Static magnetic field generation part 11 ... Main magnet 12 ... Static magnetic field power supply 2 ... Gradient magnetic field generation part 21 ... Gradient magnetic field coil 22 ... Gradient magnetic field power supply 3 ... Transmission / reception part 31 ... Transmission / reception coil 32 ... Transmission part 33 ... Reception part 4 ... Heaven Plate 5 ... Top plate moving mechanism unit 6 ... Image data generation unit 61 ... Data storage unit 611 ... MR data storage unit 612 ... Image data storage unit 62 ... High-speed calculation unit 621 ... Reconstruction processing unit 622 ... Image distortion correction unit 8 ... Display unit 9 ... Input unit 91 ... Imaging region setting function 92 ... Imaging section setting function 10 ... Magnetic field information storage unit 15 ... Control unit 151 ... Main control unit 152 ... Sequence control unit 153 ... Top plate movement control unit 200 ... MRI apparatus

Claims (7)

Imaging in the main imaging mode based on positioning image data in a plurality of crossing sections acquired by performing MRI imaging in a pilot imaging mode preceding the main imaging mode on a subject to which a static magnetic field and a gradient magnetic field are applied. In an MRI apparatus for setting a cross section and an imaging region,
Reconstruction processing means for reconstructing MR data collected by the MRI imaging and generating first positioning image data in the plurality of cross sections;
The image distortion caused by the magnetic field error of the first positioning image data is corrected for at least one of the plurality of first positioning image data generated in the plurality of cross sections to obtain a second Image distortion correction means for generating positioning image data;
Shooting area setting means for setting a shooting area in the main shooting mode based on the second positioning image data generated in a desired section;
An MRI apparatus, comprising: an imaging section setting means for setting an imaging section in the main imaging mode based on the first positioning image data generated in a section different from the desired section.   The imaging region setting means sets the imaging region based on the second positioning image data generated in a section substantially parallel to a section of diagnostic image data generated in the main imaging mode, and the imaging 2. The MRI apparatus according to claim 1, wherein the section setting unit sets the imaging section based on the first positioning image data generated in a section substantially perpendicular to the section of the diagnostic image data. .   When collecting the diagnostic image data in the sagittal section of the subject in the main imaging mode, the imaging region setting means is based on the second positioning image data generated in the sagittal section of the subject. The imaging section is set, and the imaging section setting means sets the imaging section based on the first positioning image data generated in a coronal section or an axial section of the subject. Item 3. The MRI apparatus according to Item 2.   When acquiring the diagnostic image data in the coronal section of the subject in the main imaging mode, the imaging region setting means is based on the second positioning image data generated in the coronal section of the subject. The imaging section is set, and the imaging section setting means sets the imaging section based on the first positioning image data generated in a sagittal section or an axial section of the subject. Item 3. The MRI apparatus according to Item 2.   When collecting the diagnostic image data in the axial section of the subject in the main imaging mode, the imaging area setting means is based on the second positioning image data generated in the axial section of the subject. The imaging section is set, and the imaging section setting means sets the imaging section based on the first positioning image data generated in the sagittal section or coronal section of the subject. Item 3. The MRI apparatus according to Item 2.   The image distortion correction unit corrects the first positioning image data generated by the reconstruction processing unit based on magnetic field intensity distribution data or magnetic field error distribution data of the static magnetic field and gradient magnetic field collected in advance. The MRI apparatus according to claim 1. Imaging in the main imaging mode based on positioning image data in a plurality of crossing sections acquired by performing MRI imaging in a pilot imaging mode preceding the main imaging mode on a subject to which a static magnetic field and a gradient magnetic field are applied. For the MRI device that sets the cross-section and imaging area,
A reconstruction processing function for reconstructing MR data collected by the MRI imaging to generate first positioning image data in the plurality of cross sections;
The image distortion caused by the magnetic field error of the first positioning image data is corrected for at least one of the plurality of first positioning image data generated in the plurality of cross sections to obtain a second An image distortion correction function for generating positioning image data;
A shooting area setting function for setting a shooting area in the main shooting mode based on the second positioning image data generated in a desired section;
An imaging area setting control program for executing an imaging section setting function for setting an imaging section in the main imaging mode based on the first positioning image data generated in a section different from the desired section. .

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