JP2014064700A - Magnetic resonance imaging apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic resonance imaging device capable of assisting setting of parameter values by generating pre-scan images on the basis of a plurality of the parameter values different from one another respectively.SOLUTION: The magnetic resonance imaging apparatus includes: a pre-scan image generating part 43 generating pre-scan images containing images of a plurality of slices by performing a pre-scan sequence using parameter values different from one another to each of the plurality of slices with respect to the predetermined parameters of the pre-scan sequence; a parameter setting part 42 setting parameter values of the predetermined parameters on the basis of the pre-scan images; and a main scan image generating part 44 generating a main scan image by performing a main scan sequence using the parameter values of the predetermined parameters set by the parameter setting part 42.

Description

  Embodiments described herein relate generally to a magnetic resonance imaging apparatus.

  A magnetic resonance imaging (MRI) apparatus generates an image based on an MR signal of a subject obtained by executing a scan sequence.

  There are a plurality of imaging parameters to be set in the scan sequence, and some of these parameters affect the contrast of the image. For this reason, it is preferable to set an appropriate parameter value for this type of parameter so that the user's desired contrast can be obtained.

JP 2009-101133 A

  By the way, the optimum parameter value varies depending on the age and physique of the subject. For example, children have different water content than adults. For this reason, even if the same imaging parameters as those for adults are applied to children, it is difficult to obtain the same contrast as for adults.

  However, for example, in the method in which the user determines the validity of the parameter value set by causing the user to set a parameter value in advance and presenting a sample image corresponding to the set value in advance, the validity is determined based on the sample image. However, the contrast of the image obtained by actually executing the scan sequence is not necessarily the contrast desired by the user.

  In order to solve the above-described problem, a magnetic resonance imaging apparatus according to an embodiment of the present invention performs a prescan sequence using different parameter values for each of a plurality of slices for a predetermined parameter of the prescan sequence. By executing, a pre-scan image generation unit that generates a pre-scan image including images of a plurality of slices, a setting unit that sets parameter values of predetermined parameters based on the pre-scan image, and a setting unit set A main scan image generation unit that generates a main scan image by executing a main scan sequence using parameter values of predetermined parameters.

1 is a block diagram showing a configuration example of an MRI apparatus according to a first embodiment of the present invention. The schematic block diagram which shows the structural example of the function implementation part by CPU of a main control part. Explanatory drawing which shows the relationship between the prescan sequence and 1st scan sequence which concern on 1st Embodiment. Explanatory drawing which shows an example of a mode which changes TE (echo time) of a predetermined number of slices for every slice in the prescan sequence which performs the axial cross-section imaging of a head. Explanatory drawing which shows the structural example of the pre-scan sequence which concerns on 2nd Embodiment. Explanatory drawing which shows the relationship between the pre-scan sequence which concerns on 2nd Embodiment, and this scan sequence. Explanatory drawing which shows the structural example of the pre-scan sequence which concerns on 3rd Embodiment. Explanatory drawing which shows the relationship between the pre-scan sequence which concerns on 3rd Embodiment, and this scan sequence. Explanatory drawing which shows the structural example of the pre-scan sequence which concerns on 4th Embodiment. Explanatory drawing which shows the relationship between the pre-scan sequence which concerns on 4th Embodiment, and this scan sequence.

Embodiments of a magnetic resonance imaging apparatus according to the present invention will be described with reference to the accompanying drawings.
(First embodiment)

  FIG. 1 is a block diagram showing a configuration example of the MRI apparatus 10 according to the first embodiment of the present invention.

  The MRI apparatus 10 includes a cylindrical static magnetic field magnet 11 that forms a static magnetic field, a shim coil 12, a gradient magnetic field coil unit 13, and an RF coil unit 14 provided in the static magnetic field magnet 11 in a gantry. Have

  The MRI apparatus 10 also has a control system 20. The control system 20 includes a static magnetic field power supply 21, a gradient magnetic field power supply 22, a shim coil power supply 23, a transmitter 24, a receiver 25, a sequence controller 26, and an information processing device 30.

  The gradient magnetic field power source 22 of the control system 20 includes an X-axis gradient magnetic field power source 22x, a Y-axis gradient magnetic field power source 22y, and a Z-axis gradient magnetic field power source 22z.

  The information processing apparatus 30 includes an input unit 31, a display unit 32, a storage unit 33, and a main control unit 34.

  The static magnetic field magnet 11 is connected to a static magnetic field power source 21 and forms a static magnetic field in the imaging region by a current supplied from the static magnetic field power source 21. The static magnetic field magnet 11 is composed of a superconducting coil, and is connected to the static magnetic field power source 21 at the time of excitation and supplied with a current. However, after being excited, it may be disconnected. The static magnetic field magnet 11 may be composed of a permanent magnet. In this case, the static magnetic field power source 21 may not be provided.

  A cylindrical shim coil 12 is coaxially provided inside the static magnetic field magnet 11. The shim coil 12 is connected to the shim coil power source 23, and current is supplied from the shim coil power source 23 to the shim coil 12 so that the static magnetic field is made uniform.

  The gradient coil unit 13 includes an X-axis gradient magnetic field coil 13 x, a Y-axis gradient magnetic field coil 13 y, and a Z-axis gradient magnetic field coil 13 z, and is formed in a cylindrical shape inside the static magnetic field magnet 11. A bed 35 is provided inside the gradient magnetic field coil unit 13 as an imaging region, and the subject P is placed on the bed 35. The RF coil unit 14 may not be built in the gantry but may be provided near the bed 35 or the subject P.

  The gradient magnetic field coil unit 13 is connected to a gradient magnetic field power supply 22. The X-axis gradient magnetic field coil 13x, the Y-axis gradient magnetic field coil 13y, and the Z-axis gradient magnetic field coil 13z of the gradient magnetic field coil unit 13 are respectively an X-axis gradient magnetic field power supply 22x, a Y-axis gradient magnetic field power supply 22y, and a Z-axis. It is connected to the gradient magnetic field power source 22z.

  Imaging is performed by current supplied from the X-axis gradient magnetic field power source 22x, the Y-axis gradient magnetic field power source 22y, and the Z-axis gradient magnetic field power source 22z to the X-axis gradient magnetic field coil 13x, the Y-axis gradient magnetic field coil 13y, and the Z-axis gradient magnetic field coil 13z, respectively. A gradient magnetic field Gx in the X-axis direction, a gradient magnetic field Gy in the Y-axis direction, and a gradient magnetic field Gz in the Z-axis direction are formed in each region.

  The RF coil unit 14 is connected to the transmitter 24 and the receiver 25. The RF coil unit 14 receives a high-frequency signal from the transmitter 24 and transmits the high-frequency signal to the subject P, and receives the MR signal generated by the excitation by the high-frequency signal of the nuclear spin inside the subject P and receives the receiver 25. It has the function to give to.

  The sequence controller 26 of the control system 20 is connected to the gradient magnetic field power source 22, the transmitter 24 and the receiver 25. The sequence controller 26 includes a storage medium such as a CPU, a RAM, and a ROM, and stores scan sequence information received from the information processing apparatus 30. The scan sequence information includes control information necessary for driving the gradient magnetic field power source 22, the transmitter 24, and the receiver 25, for example, operations such as the intensity, application time, and application timing of the pulse current to be applied to the gradient magnetic field power source 22. Control information is included.

  The sequence controller 26 controls operations of the gradient magnetic field power source 22, the transmitter 24, and the receiver 25 according to the scan sequence information, for example, an X-axis gradient magnetic field Gx, a Y-axis gradient magnetic field Gy, a Z-axis gradient magnetic field Gz, and a high frequency. Generate a signal. The transmitter 24 gives a high frequency signal to the RF coil unit 14 based on the control information received from the sequence controller 26. The digital data (MR signal) output from the receiver 25 is given to the information processing apparatus 30 via the sequence controller 26.

  The input unit 31 of the information processing apparatus 30 includes a general input device such as a keyboard, a touch panel, a numeric keypad, or a trackball, and outputs an operation input signal corresponding to a user operation to the main control unit 34. For example, the user gives information such as a parameter type, a scan condition, a scan sequence type and its parameters, and a desired image processing method to the main control unit 34 via the input unit 31.

  The display unit 32 is configured by a general display output device such as a liquid crystal display or an OLED (Organic Light Emitting Diode) display, and a pre-scan image or main scan generated by the main control unit 34 according to the control of the main control unit 34. Displays various information such as images.

  The storage unit 33 is configured by a non-volatile storage medium in which data can be read and written by the main control unit 34, and stores various scan sequence information, various image data such as raw image data, pre-scan images, and main scan images. Remember.

  The main control unit 34 is constituted by a storage medium such as a CPU, a RAM, and a ROM, and controls the sequence controller 26 according to a program stored in the storage medium.

  The CPU of the main control unit 34 loads a parameter setting support program stored in a storage medium such as a ROM and data necessary for executing the program into the RAM, and a plurality of parameter values different from each other according to the program. A process for supporting setting of parameter values is executed by generating a pre-scan image based on each of the above.

  The RAM of the main control unit 34 provides a work area for temporarily storing programs and data executed by the CPU.

  The storage medium including the ROM of the main control unit 34 stores a startup program for the information processing apparatus 30, a parameter setting support program, and various data necessary for executing these programs.

  A storage medium such as a ROM has a configuration including a recording medium readable by a CPU, such as a magnetic or optical recording medium or a semiconductor memory, and a part of programs and data in the storage medium. Or you may comprise so that all may be downloaded via an electronic network.

  FIG. 2 is a schematic block diagram illustrating a configuration example of the function realization unit by the CPU of the main control unit 34. In addition, this function realization part may be comprised by hardware logics, such as a circuit, without using CPU.

  As shown in FIG. 2, the CPU of the main control unit 34 functions as at least a scan sequence reading unit 41, a parameter setting unit 42, a pre-scan image generation unit 43, and a main scan image generation unit 44 by a parameter setting support program. Each of the units 41 to 44 uses a required work area of the RAM as a temporary storage location for data.

  The scan sequence reading unit 41 reads the scan sequence information stored in the storage unit 33 and causes the display unit 32 to display an image indicating the content of the scan sequence information as necessary.

  FIG. 3 is an explanatory diagram showing the relationship between the pre-scan sequence and the main scan sequence according to the first embodiment.

  The pre-scan sequence is a scan sequence for generating an image based on each of a plurality of different parameter values before execution of the main scan sequence, and the type of the scan sequence itself is the same as the main scan sequence. Shall.

  In the present embodiment, the pre-scan sequence and the main scan sequence may not include the pre-pulse sequence. FIG. 3 shows an example in which the scan sequence includes only the imaging sequence without including the pre-pulse sequence.

  FIG. 4 is an explanatory diagram showing an example of a state in which the TE (echo time) of a predetermined number of slices is changed for each slice in a pre-scan sequence for performing an axial cross-sectional imaging of the head. FIG. 4 shows an example in which the number of slices NS = 1 at the top and N multi-slice imaging is performed.

  For example, consider a case where a scan sequence for collecting a T2-weighted image, a FLAIR (Fluid Attenuated Inversion Recovery) image, a proton density (PD, Proton Density) weighted image, and the like is executed. In this case, generally, an image for diagnosis of the imaging region is captured using the same TE (echo time) in all slices (execution of the main scan sequence).

  However, the parameter value (TE value) for obtaining the optimal image contrast differs depending on the age and physique of the subject. For example, children have different water content than adults. For this reason, even if the same TE value as an adult is applied to a child, it is difficult to obtain the same contrast as an adult.

  Therefore, the MRI apparatus 10 according to the present embodiment performs TE (echo) one by one for a predetermined number k (for example, five in the example shown in FIG. 4) slices at a predetermined position to be imaged before executing the main scan sequence. The pre-scan sequence is executed using the same parameter values as in the main scan for other parameters.

  For this reason, the prescan image generation unit 43 executes a scan sequence (prescan sequence) using different TE values for each of a plurality of slices with respect to the TE (echo time) of the read scan sequence. Thus, a pre-scan image including a plurality of slice images to which different TE values are applied is generated and displayed on the display unit 32. The TE (echo time) of the scan sequence read by the scan sequence reading unit 41 can be a value designated by the user via the input unit 31 or an initial set value.

  The user confirms images of a plurality of slices to which different TE values are applied included in the pre-scan image displayed on the display unit 32, and inputs an image of a slice that the user thinks has the most preferable contrast. It designates via 31.

  The parameter setting unit 42 sets the TE (echo time) applied to the slice image based on the slice image designated by the user via the input unit 31 as the TE (echo time) used in this scan sequence. To do.

  The main scan image generation unit 44 generates a main scan image by executing the main scan sequence with the TE (echo time) set by the parameter setting unit 42 and displays the main scan image on the display unit 32 (see FIG. 3).

  For example, when the TE (echo time) of the scan sequence read by the scan sequence reading unit 41 is 165 ms, the pre-scan image generation unit 43 has five sheets near the center of the multi-slice number described in the scan sequence information. The TE (echo time) is changed every 30 ms to 105 ms, 135 ms, 165 ms, 195 ms, 225 ms, etc. For other slices, the TE (echo time) is set to 165 ms, and the generated prescan image is displayed. This is displayed on the unit 32.

  Note that the pre-scan sequence is intended to generate an image based on each of a plurality of different parameter values, and is not intended to capture an image for diagnosis of the imaging region. For this reason, it is preferable to increase the speed of the pre-scan sequence by making the image resolution coarser than that of the main scan sequence.

  For example, when this scan sequence is FSE (Fast Spin Echo) method, TR7 seconds, slice thickness 5 mm, FOV 22 cm, PE-Matrix 384, RO-Matrix 384, echo space 15 ms, echo train 21, and the number of integrations are 3 The imaging time of the scan sequence is about 6 minutes 30 seconds. In this case, if the PE-Matrix is set to 128 in the pre-scan sequence and the number of integrations is 1, the SNR (signal noise ratio) can be made substantially equal to that of the main scan and the imaging time is reduced to about 50 seconds. be able to.

  Even if the main scan sequence is a three-dimensional scan, the pre-scan sequence may be speeded up by performing a two-dimensional scan.

  According to the MRI apparatus 10 according to the present embodiment, it is possible to support setting of parameter values by a user by generating a pre-scan image based on each of a plurality of different parameter values. In addition, the user can easily perform the main scan using appropriate parameter values by designating the most preferable slice image from the plurality of slice images to which different parameter values are displayed and displayed on the display unit 32. An image can be obtained.

  Further, in the pre-scan sequence, the MRI apparatus 10 captures substantially the same cross section as the main scan sequence with the same parameters, and only TE (echo time) is automatically based on the TE (echo time) of the scan sequence information for a plurality of central images. ) To change the image. For this reason, it is possible to easily generate a pre-scan image based on each of a plurality of different parameter values.

Further, the MRI apparatus 10 can increase the speed in the pre-scan sequence by simply reducing the number of matrices or the number of integrations compared to the main scan sequence. Therefore, according to the MRI apparatus 10, the pre-scan sequence can be executed at a higher speed than the main scan sequence.
(Second Embodiment)

  Next, a second embodiment of the magnetic resonance imaging apparatus according to the present invention will be described.

  The MRI apparatus 10 shown in the second embodiment is different from the MRI apparatus 10 shown in the first embodiment in that the main control unit 34 executes a scan sequence having a pre-pulse sequence for applying an inversion pulse (Inversion pulse). Since other configurations and operations are not substantially different from those of the MRI apparatus 10 shown in FIG. 1, the same components are denoted by the same reference numerals and description thereof is omitted.

  FIG. 5 is an explanatory diagram showing a configuration example of a pre-scan sequence according to the second embodiment. FIG. 6 is an explanatory diagram showing the relationship between the pre-scan sequence and the main scan sequence according to the second embodiment. FIG. 6 shows an example in which the pre-scan sequence and the main scan sequence are multi-scan imaging.

  As shown in FIG. 5, the pre-scan sequence according to the present embodiment includes a pre-pulse sequence for applying an inversion pulse, an imaging sequence, and a standby time.

  For example, when fat suppression is performed by the STIR method (Short TI inversion Recovery method), the degree of fat suppression changes according to the time TI from the application of the inversion pulse of the pre-pulse sequence to the application of the excitation pulse to start the imaging sequence. To do. Moreover, TI differs depending on TE and TR. In addition, there is an imaging where it is desirable to leave a little fat signal instead of minimizing the fat signal, such as when imaging a part including many bones such as joint imaging.

  Therefore, in order to generate an image with the contrast (fat suppression level) desired by the user, a plurality of pre-scan images are generated by executing the pre-scan sequence by shifting the TI value before executing the main scan sequence. It is recommended that the user confirm an image that is considered to have the optimum contrast (giving the optimum TI).

  Therefore, before executing the main scan sequence, the prescan image generation unit 43 according to the present embodiment changes the TI one by one for a predetermined number k of slices at a predetermined position to be imaged as shown in FIG. For these parameters, a pre-scan sequence is executed using the same parameter values as in the main scan. At this time, the waiting time may be adjusted for each slice so that the time required for the pre-scan sequence of each slice (the total time of the pre-pulse sequence, the imaging sequence, and the waiting time) matches.

  Then, the prescan image generation unit 43 generates a prescan image including images of a plurality of slices to which different TI values are applied, and causes the display unit 32 to display the prescan image.

  The user confirms images of a plurality of slices to which different TI values are applied included in the pre-scan image displayed on the display unit 32, and inputs an image of the slice that the user thinks has the most preferable contrast. It designates via 31.

  The parameter setting unit 42 sets the TI applied to the slice image based on the slice image designated by the user via the input unit 31 as the TI used in the main scan sequence.

  The main scan image generation unit 44 generates a main scan image by executing the main scan sequence with the TI set by the parameter setting unit 42 and causes the display unit 32 to display the main scan image.

  Even if the main scan sequence is a three-dimensional scan, the pre-scan sequence may be speeded up by performing a two-dimensional scan. Further, the pre-scan sequence may be speeded up simply by reducing the matrix or the number of integrations compared to the main scan sequence.

The MRI apparatus 10 according to the present embodiment also has the same effects as the MRI apparatus 10 according to the first embodiment. Further, according to the MRI apparatus 10 according to the present embodiment, the user can easily obtain a diagnostic captured image having a desired degree of fat signal suppression.
(Third embodiment)

  Next, a third embodiment of the magnetic resonance imaging apparatus according to the present invention will be described.

  The MRI apparatus 10 shown in the third embodiment differs from the MRI apparatus 10 shown in the first embodiment in that the main control unit 34 executes a scan sequence having a pre-pulse sequence in which an inversion pulse is applied twice. Since other configurations and operations are not substantially different from those of the MRI apparatus 10 shown in FIG. 1, the same components are denoted by the same reference numerals and description thereof is omitted.

  FIG. 7 is an explanatory diagram showing a configuration example of a pre-scan sequence according to the third embodiment. FIG. 8 is an explanatory diagram showing the relationship between the pre-scan sequence and the main scan sequence according to the third embodiment. FIG. 8 shows an example in which the pre-scan sequence and the main scan sequence are multi-scan imaging.

  As shown in FIG. 7, the pre-scan sequence according to this embodiment includes a pre-pulse sequence in which an inversion pulse is applied twice, an imaging sequence, and a standby time. That is, the so-called double IR method is used in the pre-pulse sequence according to the present embodiment.

  In the doubleIR method, a time Δt1 (for example, 3 s) from application of the first inversion pulse to application of the excitation pulse to start the imaging sequence, and a period from application of the first inversion pulse to application of the excitation pulse. The contrast of the image changes according to the time Δt2 (for example, 200 ms).

  Therefore, in order to generate an image with a contrast desired by the user, a plurality of pre-scan images are generated by performing a pre-scan sequence by shaking at least one of Δt 1 and Δt 2 before executing the main scan sequence. It is recommended that the user confirm an image that is considered to have the optimum contrast.

  Here, since it is known that Δt2 has a greater influence on contrast than Δt1, Δt2 may be changed when only one of them is changed. In the following description, an example in which a pre-scan sequence is executed while changing Δt2 will be described.

  Before executing the main scan sequence, the prescan image generation unit 43 according to the present embodiment changes Δt2 for each of a predetermined number k of slices at a predetermined position to be imaged as shown in FIG. For, a pre-scan sequence is executed using the same parameter values as in the main scan. At this time, the waiting time may be adjusted for each slice so that the time required for the pre-scan sequence of each slice (the total time of the pre-pulse sequence, the imaging sequence, and the waiting time) matches.

  Then, the pre-scan image generation unit 43 generates a pre-scan image including a plurality of slice images to which different Δt2 values are applied, and causes the display unit 32 to display the pre-scan image.

  The user confirms images of a plurality of slices to which different Δt2 values included in the pre-scan image displayed on the display unit 32 are applied, and selects an image of the slice that the user thinks has the most preferable contrast as the input unit. It designates via 31.

  The parameter setting unit 42 sets Δt2 applied to the image of the slice as Δt2 used in the main scan sequence based on the slice image designated by the user via the input unit 31.

  The main scan image generation unit 44 generates a main scan image by executing the main scan sequence at Δt 2 set by the parameter setting unit 42 and causes the display unit 32 to display the main scan image.

  Even if the main scan sequence is a three-dimensional scan, the pre-scan sequence may be speeded up by performing a two-dimensional scan. Further, the pre-scan sequence may be speeded up simply by reducing the matrix or the number of integrations compared to the main scan sequence.

The MRI apparatus 10 according to the present embodiment also has the same effects as the MRI apparatus 10 according to the first embodiment. Further, according to the MRI apparatus 10 according to the present embodiment, a user can easily obtain a diagnostic captured image having a desired contrast for an image obtained by a scan sequence having a pre-pulse sequence by the doubleIR method.
(Fourth embodiment)

  Next, a fourth embodiment of the magnetic resonance imaging apparatus according to the present invention will be described.

  In the MRI apparatus 10 shown in the fourth embodiment, the main control unit 34 executes a scan sequence having a pre-pulse sequence based on a so-called T2 preparation method composed of a series of 90 °, 180 °, and −90 ° series pulses. Different from the MRI apparatus 10 shown in the first embodiment. Since other configurations and operations are not substantially different from those of the MRI apparatus 10 shown in FIG. 1, the same components are denoted by the same reference numerals and description thereof is omitted.

  FIG. 9 is an explanatory diagram showing a configuration example of a pre-scan sequence according to the fourth embodiment. FIG. 10 is an explanatory diagram showing the relationship between the pre-scan sequence and the main scan sequence according to the fourth embodiment.

  In the present embodiment, an example in which the pre-scan sequence and the main scan sequence are three-dimensional scans will be described.

  As shown in FIG. 10, the pre-scan sequence according to the present embodiment includes a pre-pulse sequence composed of a series of 90 °, 180 °, and −90 ° series pulses, an imaging sequence, and a standby time. That is, the so-called T2 preparation method is used in the prepulse sequence according to the present embodiment.

  In the T2 preparation method, the contrast of the image changes according to the time from the first 90 ° pulse to the second 90 ° pulse (hereinafter referred to as TE of T2prep).

  Therefore, in order to generate an image with the contrast desired by the user, the pre-scan sequence is generated by shaking the TE of T2prep before execution of the main scan sequence to generate a plurality of pre-scan images. It is recommended that the user confirm the image that is considered to be.

  Therefore, the prescan image generation unit 43 according to the present embodiment executes the prescan sequence a plurality of times as shown in FIG. 10 before executing the main scan sequence (three-dimensional scan). At this time, for each execution time, different values are used for TE of T2prep, and parameter values similar to those in the main scan are used for other parameters. In addition, the waiting time may be adjusted for each execution time so that the time required for the pre-scan sequence for each execution time (the total time of the pre-pulse sequence, the imaging sequence, and the standby time) matches.

  Then, the prescan image generation unit 43 generates a prescan image corresponding to each execution time to which different TE values of T2prep are applied, and causes the display unit 32 to display the prescan image.

  The user confirms the prescan image corresponding to each execution time displayed on the display unit 32, and designates the prescan image that the user thinks has the most preferable contrast via the input unit 31.

  Based on the prescan image designated by the user via the input unit 31, the parameter setting unit 42 uses the T2prep TE applied in the prescan sequence from which the prescan image is obtained in the main scan sequence. Set as TE.

  The main scan image generation unit 44 generates a main scan image by executing the main scan sequence with the T2prep TE set by the parameter setting unit 42 and causes the display unit 32 to display the main scan image.

  Note that the pre-scan sequence may be speeded up by simply reducing the matrix or the number of integrations compared to the main scan sequence.

  For example, when the T2prep TE of the scan sequence read by the scan sequence reading unit 41 is 80 ms and the prescan sequence is executed four times, the prescan image generation unit 43 sets the T2prep for each execution of the prescan sequence. The prescan sequence is executed by changing TE every 30 ms, 30 ms, 50 ms, 80 ms, 110 ms, etc., and the generated prescan image is displayed on the display unit 32.

  In the case of 3D-T2W imaging with a variable refocusing flip angle (VFA), this scan sequence has a slice thickness of 0.8 mm, a TR of 3 seconds, a number of slices of 300, and a number of shots of 1 (one 90 ° excitation pulse). ), When the parallel imaging in the slice direction is 2, PE-Matrix 256, and RO-Matrix 256, the imaging time of this scan sequence is TR 3 seconds × number of shots 1 × number of slices 300 / parallel imaging 2 = 7 minutes 30 seconds.

  In this case, if the slice thickness is 8 mm and the number of slices is 20 in the pre-scan sequence, the scan time of one pre-scan sequence is TR 3 seconds × number of shots 1 × number of slices 20 / parallel imaging 2 = 30 seconds, Repeat 4 times for a total of 2 minutes. At this time, the waiting time may be adjusted for each execution time so that the time required for the pre-scan sequence for each execution time (the total time of the pre-pulse sequence, the imaging sequence, and the standby time) matches.

  In the above example, when the SNR is matched with the main scan sequence, the number of slices in the prescan sequence should be 30 instead of 20. However, the prescan image for contrast confirmation is used even if the SNR does not completely match. The purpose of generating is considered to be achieved. Therefore, in the above example, an example in which priority is given to speeding up and the number of slices is set to 20 has been described.

  Even if the main scan sequence is a three-dimensional scan, the pre-scan sequence may be speeded up by performing a two-dimensional scan.

  In the above example, when the pre-scan sequence is a single slice two-dimensional scan, the slice thickness may be increased to, for example, about 5 cm in order to ensure SNR, and the scan time of one pre-scan sequence is a single slice. To TR is only 3 seconds, and even if it is repeated 4 times, the total is 12 seconds. If the SNR is insufficient, the number of integrations may be increased. For example, when the number of integrations is 3, the total is 36 seconds.

  When the pre-scan sequence is a single slice two-dimensional scan, the slice position to be scanned in each execution time may be the same.

  The MRI apparatus 10 according to the present embodiment also has the same effects as the MRI apparatus 10 according to the first embodiment. Further, according to the MRI apparatus 10 according to the present embodiment, the user can easily obtain a diagnostic T2-weighted image having an optimum contrast.

  In addition, although some embodiment of this invention was described, these embodiment is shown as an example and is not intending limiting the range of invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

DESCRIPTION OF SYMBOLS 10 MRI apparatus 20 Control system 26 Sequence controller 30 Information processing apparatus 31 Input part 32 Display part 33 Storage part 34 Main control part 41 Scan sequence reading part 42 Parameter setting part 43 Prescan image generation part 44 Main scan image generation part

Claims (7)

A prescan image for generating a prescan image including images of the plurality of slices by executing the prescan sequence using different parameter values for each of the plurality of slices for a predetermined parameter of the prescan sequence A generator,
A setting unit for setting a parameter value of the predetermined parameter based on the pre-scanned image;
A main scan image generation unit that generates a main scan image by executing a main scan sequence using the parameter value of the predetermined parameter set by the setting unit;
A magnetic resonance imaging apparatus comprising: The pre-scan image generation unit
Generating a pre-scan image including images of the plurality of slices by executing the pre-scan sequence using different parameter values for each of the plurality of slices with respect to an echo time of the imaging sequence;
The magnetic resonance imaging apparatus according to claim 1. The pre-scan sequence and the main scan sequence are:
Having a pre-pulse sequence that applies an inversion pulse before the imaging sequence;
The pre-scan image generation unit
Executing the pre-scan sequence using different times for each of the plurality of slices with respect to a time from application of the inversion pulse of the pre-pulse sequence to application of an excitation pulse to start the imaging sequence To generate a pre-scan image including images of the plurality of slices,
The magnetic resonance imaging apparatus according to claim 1 or 2. The pre-scan sequence and the main scan sequence are:
Having a pre-pulse sequence in which an inversion pulse is applied twice before the imaging sequence;
The pre-scan image generation unit
The pre-scan sequence is performed using different times for each of the plurality of slices with respect to the time from the second application of the inversion pulse of the pre-pulse sequence to the application of the excitation pulse to start the imaging sequence. Generating a pre-scan image including images of the plurality of slices by executing,
The magnetic resonance imaging apparatus according to claim 1 or 2. The pre-scan sequence and the main scan sequence are:
Having a pre-pulse sequence consisting of a series of pulses of 90 °, 180 °, -90 ° sequence before the imaging sequence;
The pre-scan image generation unit
By executing the pre-scan sequence using different times for each of the plurality of slices for the time from the first 90 ° pulse to the second 90 ° pulse of the pre-pulse sequence, Generate a pre-scan image including the image,
The magnetic resonance imaging apparatus according to claim 1 or 2. A display unit for displaying the prescan image;
An input unit for receiving a selection instruction by a user for one of the images of the plurality of slices included in the pre-scan image;
With
The setting unit
Setting a parameter value used for one of the images of the plurality of slices selected by the user as a parameter value of the predetermined parameter;
The magnetic resonance imaging apparatus according to claim 1. A magnetic resonance imaging apparatus for executing a scan sequence having a pre-pulse sequence consisting of a series of pulses of a 90 °, 180 °, and −90 ° sequence before an imaging sequence,
The pre-scan sequence is executed a plurality of times, and the time from the first 90 ° pulse of the pre-pulse sequence to the second 90 ° pulse is set to a different time for a plurality of execution times of the pre-scan sequence for a predetermined slice. A pre-scan image generation unit that generates a pre-scan image including the image of the predetermined slice for each of the plurality of execution times,
A setting unit for setting a time from the first 90 ° pulse of the prepulse sequence to the second 90 ° pulse based on the prescan image;
A main scan image generation unit that generates a main scan image by executing a main scan sequence using a time from the first 90 ° pulse to the second 90 ° pulse of the pre-pulse sequence set by the setting unit;
A magnetic resonance imaging apparatus comprising:

Images