JP2007289344A - Magnetic resonance imaging apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a magnetic resonance imaging apparatus which efficiently carries out image diagnoses. <P>SOLUTION: A map image generating part 133 generates a map image MI(x, y) which shows that a SN ratio of a main scan image AI(x, y) generated under the conditions of a main scan is mapped before the main scan is carried out. Here, the map image MI(x, y) is generated from reception sensitivity distribution S(x, y) calculated by a reception distribution calculating part 231 and transmission sensitivity distribution f(x, y) calculated by a transmission sensitivity distribution calculating part 232. A displaying part 33 displays the map image MI(x, y) generated by the part 133 on a display screen. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a magnetic resonance imaging apparatus, and in particular, an RF coil unit transmits an RF pulse to an imaging region of a subject in a static magnetic field space, and an RF signal generated in the imaging region to which the RF pulse is transmitted is RF. The present invention relates to a magnetic resonance imaging apparatus that generates a main scan image of an imaging region based on a magnetic resonance signal obtained by performing a scan received by a coil unit.

  2. Description of the Related Art Magnetic resonance imaging (MRI) apparatuses are often used particularly in medical applications as apparatuses that take an image of a tomographic plane of a subject by using a nuclear magnetic resonance (NMR) phenomenon. ing.

  In a magnetic resonance imaging apparatus, a subject is accommodated in a static magnetic field space, so that proton spins of the subject are aligned in the direction of the static magnetic field to generate a magnetization vector. Then, the magnetic vector of the proton is changed by generating a nuclear magnetic resonance phenomenon by irradiating an RF pulse having a resonance frequency. Thereafter, the magnetic resonance imaging apparatus receives a magnetic resonance (MR) signal generated when the proton returns to the state of the original magnetization vector, and determines the tomographic plane of the subject based on the received magnetic resonance signal. Tomographic images are generated (see, for example, Patent Document 1).

JP 2005-177240 A

  In the magnetic resonance imaging apparatus, a surface coil such as a phased array coil is often used as an RF receiving coil for receiving a magnetic resonance signal. However, this surface coil has a characteristic that the sensitivity of reception decreases as the distance from the magnetic resonance signal generation source in the subject increases, and the sensitivity distribution in the entire imaging region is spatial. It is not uniform.

  For example, when imaging a subject in a high static magnetic field space with a magnetic field strength of 3 Tesla or higher, a high-frequency magnetic field formed by an RF transmission coil such as a body coil transmitting RF pulses. However, it may become non-uniform due to the dielectric constant effect.

  For this reason, noise may occur in an image such as a tomographic image generated on the tomographic plane of the subject, the SN ratio (signal / noise ratio) may decrease, and the image quality may deteriorate.

  In particular, when micro imaging (micro imaging) for capturing an image with a spatial resolution of about 100 μm is performed by using a small coil or by setting the magnetic field strength of the static magnetic field space to 7 Tesla, this problem occurs. May manifest. In addition, since this micro-imaging has a long imaging time, it is often difficult to perform imaging again when a lot of noise occurs.

  As described above, noise may occur in an image generated by magnetic resonance imaging, and the image quality may be deteriorated. Therefore, it may be difficult to efficiently perform image diagnosis.

  Accordingly, an object of the present invention is to provide a magnetic resonance imaging apparatus capable of efficiently performing image diagnosis.

  In order to achieve the above object, in the magnetic resonance imaging apparatus of the present invention, an RF coil unit transmits an RF pulse to an imaging region of a subject in a static magnetic field space, and is generated in the imaging region where the RF pulse is transmitted. After performing a main scan in which the RF coil unit receives a magnetic resonance signal based on the main scan condition, a main scan image for the imaging region is generated based on the magnetic resonance signal obtained by performing the main scan. A magnetic resonance imaging apparatus comprising: a map image generation unit configured to generate a map image in which an SN ratio of a main scan image generated under the main scan condition is mapped before the main scan is performed; The map image generator generates a transmission sensitivity distribution when the RF coil unit transmits the RF pulse in the imaging region. A transmission sensitivity distribution calculation unit that outputs, and a reception sensitivity distribution calculation unit that calculates a reception sensitivity distribution when the RF coil unit receives the magnetic resonance signal in the imaging region, and is calculated by the transmission sensitivity distribution calculation unit. The map image is generated based on the transmission sensitivity distribution and the reception sensitivity distribution calculated by the reception distribution calculation unit.

  As described above, according to the present invention, a magnetic resonance imaging apparatus capable of efficiently performing image diagnosis can be provided.

  Hereinafter, an example of an embodiment according to the present invention will be described with reference to the drawings.

(Device configuration)
FIG. 1 is a configuration diagram showing a configuration of a magnetic resonance imaging apparatus 1 in an embodiment according to the present invention.

  As shown in FIG. 1, the magnetic resonance imaging apparatus 1 of the present embodiment includes a scanning unit 2 and an operation console unit 3, transmits an RF pulse to an imaging region of a subject in a static magnetic field space, After performing the main scan for receiving the magnetic resonance signal generated in the imaging region to which the RF pulse is transmitted based on the main scanning condition, the imaging region is calculated based on the magnetic resonance signal obtained by performing the main scan. A main scan image of the tomographic plane is generated.

  The scanning unit 2 will be described.

  As shown in FIG. 1, the scanning unit 2 includes a static magnetic field magnet unit 12, a gradient coil unit 13, an RF coil unit 14, a cradle 15, an RF drive unit 22, a gradient drive unit 23, and a data collection unit. 24. The scanning unit 2 transmits an RF pulse to the subject SU so as to excite the spin of the subject SU in the imaging space B where the static magnetic field is formed, and a gradient to the subject SU to which the RF pulse is transmitted. The main scan AS for obtaining the magnetic resonance signal generated in the subject SU as the main scan data by transmitting the pulse is performed. The scan unit 2 performs the main scan AS, performs the reference scan RS for the subject SU before the execution of the main scan AS, and uses the magnetic resonance signal generated in the reference scan RS as reference scan data. Get as.

  Each component of the scanning unit 2 will be described sequentially.

  The static magnetic field magnet unit 12 is composed of, for example, a superconducting magnet (not shown), and forms a static magnetic field in the imaging space B in which the subject SU is accommodated. Here, the static magnetic field magnet unit 12 forms a static magnetic field along the body axis direction (z direction) of the subject SU placed on the cradle 15. The static magnetic field magnet unit 12 may be composed of a pair of permanent magnets.

  The gradient coil unit 13 forms a gradient magnetic field in the imaging space B in which a static magnetic field is formed, and adds spatial position information to the magnetic resonance signal received by the RF coil unit 14. Here, the gradient coil unit 13 includes three systems of gradient coils so as to correspond to three axial directions orthogonal to each other in the z direction along the static magnetic field direction, the x direction, and the y direction. These transmit gradient pulses so as to form gradient magnetic fields in the frequency encoding direction, the phase encoding direction, and the slice selection direction in accordance with the scanning conditions. Specifically, the gradient coil unit 13 applies a gradient magnetic field in the slice selection direction of the subject SU, and selects a slice of the subject SU to be excited when the RF coil unit 14 transmits an RF pulse. The gradient coil unit 13 applies a gradient magnetic field in the phase encoding direction of the subject SU, and phase encodes the magnetic resonance signal from the slice excited by the RF pulse. The gradient coil unit 13 applies a gradient magnetic field in the frequency encoding direction of the subject SU, and frequency encodes the magnetic resonance signal from the slice excited by the RF pulse.

  In the imaging space B where the static magnetic field is formed by the static magnetic field magnet unit 12, the RF coil unit 14 transmits an RF pulse, which is an electromagnetic wave, to the imaging region of the subject SU to form a high-frequency magnetic field, and the subject SU Excites proton spin in the imaging region. Then, the RF coil unit 14 receives an electromagnetic wave generated from protons in the imaging region of the excited subject SU as a magnetic resonance signal. In the present embodiment, the RF coil unit 14 includes a first RF coil 14a and a second RF coil 14b as shown in FIG. Here, the first RF coil 14a is, for example, a bird gauge type body coil, and is arranged so as to surround the imaging region of the subject SU. On the other hand, the second RF coil 14b is a coil whose reception sensitivity distribution is more non-uniform than that of the first RF coil 14a in the imaging region, and is a phased array coil, and includes a plurality of surface coils along the surface of the imaging region of the subject SU. Is arranged.

  The cradle 15 has a table on which the subject SU is placed. The cradle 15 moves the table between the inside and outside of the imaging space B based on a control signal from the control unit 30.

  The RF drive unit 22 drives the RF coil unit 14 to transmit an RF pulse in the imaging space B, thereby forming a high frequency magnetic field in the imaging space B. Based on the control signal from the control unit 30, the RF drive unit 22 uses a gate modulator (not shown) to modulate a signal from the RF oscillator (not shown) into a signal having a predetermined timing and a predetermined envelope. Later, the signal modulated by the gate modulator is amplified by an RF power amplifier (not shown) and output to the RF coil unit 14 to transmit an RF pulse.

  Based on a control signal from the control unit 30, the gradient driving unit 23 applies a gradient pulse to the gradient coil unit 13 to drive the gradient coil unit 13, thereby generating a gradient magnetic field in the imaging space B in which a static magnetic field is formed. The gradient drive unit 23 includes three systems of drive circuits (not shown) corresponding to the three systems of gradient coil units 13.

  The data collection unit 24 collects magnetic resonance signals received by the RF coil unit 14 based on the control signal from the control unit 30. Here, in the data collection unit 24, the phase detector (not shown) detects the magnetic resonance signal received by the RF coil unit 14 using the output of the RF oscillator (not shown) of the RF drive unit 22 as a reference signal. Thereafter, using an A / D converter (not shown), the magnetic resonance signal, which is an analog signal, is converted into a digital signal and output.

  The operation console unit 3 will be described.

  As shown in FIG. 1, the operation console unit 3 includes a control unit 30, a data processing unit 31, an image correction unit 31 a, an operation unit 32, a display unit 33, and a storage unit 34.

  Each component of the operation console unit 3 will be described sequentially.

  The control unit 30 includes a computer and a program that causes the computer to execute predetermined data processing, and controls each unit. Here, the control unit 30 receives operation data from the operation unit 32, and each of the RF drive unit 22, the gradient drive unit 23, and the data collection unit 24 based on the operation data input from the operation unit 32. A control signal is output to a predetermined scan. At the same time, a control signal is output to the data processing unit 31, the display unit 33, and the storage unit 34 to perform control.

  The data processing unit 31 includes a computer and a program that executes predetermined data processing using the computer, and processes data based on a control signal from the control unit 30.

  FIG. 2 is a block diagram showing the data processing unit 31 in the embodiment according to the present invention.

  As illustrated in FIG. 2, the data processing unit 31 includes a main scan image generation unit 131, a reference image generation unit 132, a map image generation unit 133, and an imaging time calculation unit 134.

  Here, the main scan image generation unit 131 generates a main scan image for the imaging region of the subject SU using the magnetic resonance signal obtained by performing the main scan for the imaging region of the subject SU as raw data. To do. In addition, the reference image generation unit 132 uses the magnetic resonance signal obtained by the reference scan performed before the main scan for the imaging region of the subject SU as raw data, for the imaging region of the subject SU. A reference scan image is generated. Further, the map image generation unit 133 generates a map image in which the SN ratio of the image generated under the main scan condition is mapped before the main scan is performed. The imaging time calculation unit 134 corresponds to the set value of the SN ratio based on the set value of the S / N ratio of the main scan image input to the operation unit by the operator and the map image generated by the map image generation unit 133. Then, the imaging time for performing the main scan is calculated so that the main scan image is generated.

  FIG. 3 is a block diagram showing the map image generation unit 133 in the embodiment according to the present invention.

  As illustrated in FIG. 3, the map image generation unit 133 includes a reception sensitivity distribution calculation unit 231 and a transmission sensitivity distribution calculation unit 232. Here, the reception sensitivity distribution calculation unit 231 calculates a reception sensitivity distribution when the RF coil unit 14 receives a magnetic resonance signal in the imaging region of the subject SU. In addition, the transmission sensitivity distribution calculating unit 232 calculates a transmission sensitivity distribution when the RF coil unit 14 transmits an RF pulse in the imaging region of the subject SU.

  Then, the map image generation unit 133 generates a map image based on the reception sensitivity distribution calculated by the reception distribution calculation unit 231 and the transmission sensitivity distribution calculated by the transmission sensitivity distribution calculation unit 232. Further, the map image generation unit 133 generates the map image so as to correspond to the main scan condition input to the operation unit 32.

  The operation unit 32 is configured by operation devices such as a keyboard and a pointing device. The operation unit 32 is input with operation data such as a main scan condition by an operator, and outputs the operation data to the control unit 30. Specifically, in the operation unit 32, a set value of the S / N ratio of the main scan image generated by the main scan is input by the operator.

  The display unit 33 is configured by a display device such as a CRT, and displays an image on the display screen based on a control signal from the control unit 30. For example, the display unit 33 displays a plurality of images of input items for which operation data is input to the operation unit 32 by the operator on the display screen. Further, the display unit 33 receives data about the image of the subject SU generated based on the magnetic resonance signal from the subject SU from each unit of the data processing unit 31 and displays the image on the display screen. Here, the display unit 33 displays the map image generated by the map image generation unit 133 on the display screen before the main scan is performed. Further, the display unit 33 displays the imaging time calculated by the imaging time calculation unit 134 on the display screen before the main scan is performed.

  The storage unit 34 includes a memory and stores various data. The storage device 33 is accessed by the control unit 30 as necessary for the stored data.

(Operation)
Hereinafter, an operation when an imaging region of the subject SU is imaged using the magnetic resonance imaging apparatus 1 according to the embodiment of the present invention will be described.

  FIG. 4 is a flowchart showing an operation when imaging the imaging region of the subject SU in the embodiment according to the present invention. FIG. 5 is a diagram showing a data flow when an imaging region of the subject SU is imaged in the embodiment according to the present invention.

  First, as shown in FIG. 4, the reference scan RS is performed (S11).

  Here, the RF coil unit 14 transmits an RF pulse to the imaging region of the subject SU imaged in the main scan AS, and the RF coil unit 14 receives a magnetic resonance signal generated in the imaging region of the subject SU. The scanning unit 2 performs the reference scan RS to be performed.

  In the present embodiment, the scan unit 2 performs each of the first reference scan RS1, the second reference scan RS2, and the third reference scan RS3 as the reference scan RS. Here, each of the first reference scan RS1, the second reference scan RS2, and the third scan RS3 is performed by the gradient echo method.

Specifically, the first RF coil 14a, which is a body coil, transmits an RF pulse of the first flip angle α1 to the imaging region of the subject SU, and a magnetic resonance signal generated in the imaging region is the body coil. The scan unit 2 performs the first reference scan RS1 so that the first RF coil 14a receives. And the magnetic resonance signal obtained by implementation of this 1st reference scan RS1 is acquired as 1st reference scan data RS _alpha1 .

The first RF coil 14a, which is a body coil, transmits an RF pulse having a first flip angle α1 to the imaging region of the subject SU, and the magnetic resonance signal generated in the imaging region is transmitted to the second RF coil, which is a phased array coil. The scanning unit 2 performs the second reference scan RS2 so that 14b is received. The magnetic resonance signal obtained by the implementation of the second reference scan RS2, is acquired as second reference scan data RS _S.

Further, the RF pulse of the second flip angle α2 different from the first flip angle α1 is transmitted to the imaging region of the subject SU by the first RF coil 14a, which is a body coil, and a magnetic resonance signal generated in the imaging region. So that the first RF coil 14a, which is a body coil, receives the first reference scan RF3. In the present embodiment, when the third reference scan RS3 is performed, the first RF coil 14a is RF-fed to the imaging region so that the second flip angle α2 is half of the first flip angle α1. Send a pulse. Then, the magnetic resonance signal obtained by performing the third reference scan RS3 is acquired as third reference scan data RS _α2 . Since the calculation formula can be simplified as shown in the following formula (2) by setting the second flip angle α2 to half the first flip angle α1, the B1 distribution θ (x, y) It is possible to speed up the data processing when calculating.

Thus, in this step (S11), as shown in FIG. 5, obtaining a first reference scan data RS _{[alpha] 1,} a second reference scan data RS _S, each of the third reference scan data RS _{[alpha] 2} To do.

  Next, as shown in FIG. 2, a reference image RI (x, y) is generated (S21).

Here, the reference image generation unit 132 generates the reference image RI (x, y) for the imaging region based on the magnetic resonance signal obtained by performing the reference scan RS. In the present embodiment, as the reference image RI (x, y), a first reference image RI _α1 (x, y), a second reference image RI _S (x, y), and a third reference image RI _α2 (x , Y).

Specifically, as shown in FIG. 5, based on the first reference scan data RS _α1 obtained by performing the first reference scan RS1, the first reference image RI _α1 (x , Y) is generated by the reference image generation unit 132.

Then, as shown in FIG. 5, on the basis of the second reference scan data RS _S obtained by the execution of the second reference scan RS2, the second reference image _RI S about the imaging area of the subject SU (x, y) Is generated by the reference image generation unit 132.

Then, as shown in FIG. 5, based on the third reference scan data RS _α2 obtained by performing the third reference scan RS3, the third reference image RI _α2 (x, y) for the imaging region of the subject SU. Is generated by the reference image generation unit 132.

  Next, as shown in FIG. 4, the reception sensitivity distribution S (x, y) and the transmission sensitivity distribution f (x, y) are calculated (S31).

Here, the reception sensitivity distribution S (x, y) is based on the first reference image RI _α1 (x, y) and the second reference image RI _S (x, y) as shown in FIG. The reception sensitivity distribution calculation unit 231 calculates.

Specifically, as shown in the following formula (1), each pixel data of the first reference image RI _α1 (x, y) is received by each pixel data of the second reference image RI _S (x, y). The sensitivity distribution calculation unit 231 divides to calculate the reception sensitivity distribution S (x, y).

On the other hand, as shown in FIG. 5, the transmission sensitivity distribution f (x, y) is based on the first reference image RI _α1 (x, y) and the third reference image RI _α2 (x, y). A transmission sensitivity distribution (transmission sensitivity non-uniformity) f (x, y) generated in the main scan image generated by the scan AS is calculated. Here, using the first reference image RI _α1 (x, y) and the third reference image RI _α2 (x, y), the transmission sensitivity distribution calculation unit 232 uses the B1 distribution (flip angle distribution) θ (x, y). ) Is calculated, a transmission sensitivity distribution (transmission sensitivity non-uniformity) f (x, y) generated in the main scan image generated by the main scan AS is calculated based on the B1 distribution.

Specifically, as shown in the following formula (2), imaging of the subject SU is performed using the first reference image RI _α1 (x, y) and the third reference image RI _α2 (x, y). A B1 distribution θ (x, y) for the region is calculated.

  Then, the transmission sensitivity distribution f (x, y) relating to the main scan image generated by performing the main scan AS in the spin echo sequence is calculated as shown in the following formula (3).

  On the other hand, the transmission sensitivity distribution f (x, y) for the main scan image generated by performing the main scan AS with a gradient echo sequence is calculated as shown in the following equation (4).

  In the above formulas (3) and (4), α is a flip angle when the first reference scan is performed, and β is a flip angle when the main scan AS is performed with a gradient echo sequence. It is.

  Next, as shown in FIG. 4, a map image MI (x, y) is generated (S41).

  Here, the S / N ratio of the main scan image AI (x, y) generated under the main scan condition is simulated so as to correspond to the pixel, and the simulated S / N ratio is calculated as the main scan image AI (x, y). The map image generation unit 133 generates a map image MI (x, y) by performing mapping so as to correspond to the pixels. Specifically, as shown in FIG. 5, the reception sensitivity distribution calculated by the reception distribution calculation unit 231, the transmission sensitivity distribution calculated by the transmission sensitivity distribution calculation unit 232, and the main scan input to the operation unit 32. Based on the conditions, the map image generation unit 133 generates a map image MI (x, y).

  In the present embodiment, the map image MI (x, y) is generated as shown in the following formula (5).

  Here, c (x, y) is a term indicating a change in contrast caused by imaging conditions, T1 value, T2 value, and nonuniform transmission sensitivity. For this reason, for example, the transmission / reception sensitivity non-uniformity is set to a fixed value. Note that c (x, y) may be calculated according to the imaging method as follows.

  For example, in the case of the SPGR method, it is expressed as the following formula (6).

  Here, φ indicates an actual flip angle at the pixel position (x, y), and is represented by the following mathematical formula (7).

  Further, in the case of the SE method, it is expressed as the following formula (8).

  Here, ψ represents an actual flip angle at the pixel position (x, y), and is represented by the following formula (9).

  Next, as shown in FIG. 4, the imaging time is calculated (S43).

  Here, the imaging time calculation unit 134 is set based on the set value of the S / N ratio of the main scan image input to the operation unit 32 by the operator and the map image generated by the map image generation unit 133. The imaging time for performing the main scan is calculated so that the main scan image is generated with the SN ratio.

  In the present embodiment, the imaging time ST (x, y) is calculated as shown in the following formula (10).

  Next, as shown in FIG. 4, a map image MI (x, y) and an imaging time are displayed (S45).

  Here, the display unit 33 displays the map image MI (x, y) generated by the map image generation unit 133 and the imaging time calculated by the imaging time calculation unit 134 on the display screen.

  FIG. 6 is a diagram showing a display screen displaying the map image MI (x, y) and the imaging time in the embodiment according to the present invention.

  As shown in FIG. 6, the map image MI (x, y) is displayed superimposed on the slice image SI (x, y) imaged for positioning. For example, the map image MI (x, y) is displayed so that an area where the SN ratio is equal to or larger than a predetermined value is indicated by a red color different from the monochrome-display slice image SI (x, y). Here, the map image MI (x, y) may be displayed so that the color density varies depending on the value of the SN ratio. Further, it may be displayed in a transparent manner. Then, an image ST indicating the imaging time is displayed on the display screen so as to line up with this. For example, in the calculated imaging time ST (x, y), the imaging time at the designated position is displayed in a digital display. Note that the imaging time ST (x, y) may be displayed as a map image.

  Next, as shown in FIG. 4, it is determined whether the map image MI (x, y) and the imaging time are within an allowable range (S47).

  Here, the operator observes the map image MI (x, y) displayed on the display screen of the display unit 33 and the imaging time, and determines whether or not the allowable range is satisfied. For example, in the map image MI (x, y), it is determined whether or not the portion corresponding to the imaging region to be imaged by the main scan has an SN ratio equal to or greater than a predetermined value. Further, it is determined whether or not the imaging time for the portion is equal to or less than a predetermined value.

  If it is not within the allowable range (No), the main scanning condition is changed as shown in FIG. 4 (S50). Then, again, calculation of the reception sensitivity distribution S (x, y) and transmission sensitivity distribution f (x, y) (S31), generation of the map image MI (x, y) (S41), calculation of the imaging time (S43) ), The map image MI (x, y) and the imaging time display (S45) are executed so as to correspond to the changed main scan condition. Similarly, it is determined whether the map image MI (x, y) and the imaging time are within an allowable range (S47).

  On the other hand, if it is within the allowable range (Yes), the main scan AS is performed as shown in FIG. 4 (S51).

  Here, based on the main scanning condition, the RF coil unit 14 transmits an RF pulse to the imaging region of the subject SU in the imaging space B where the static magnetic field is formed, and is generated in the imaging region where the RF pulse is transmitted. When the magnetic resonance signal to be received is received as the main scan data by the RF coil unit 14, the main scan AS is performed. For example, the main scan AS of micro-imaging is performed according to a pulse sequence of a spin echo sequence or a gradient echo sequence.

  Next, as shown in FIG. 4, the main scan image AI (x, y) is generated (S61).

  Here, the magnetic resonance signal obtained as the main scan data by performing the main scan AS is used as raw data, and the main scan image AI (x, y) for the imaging region is generated by the main scan image generation unit 131.

  Next, as shown in FIG. 4, the main scan image AI (x, y) is displayed (S81).

  Here, the display unit 33 displays the main scan image AI (x, y) generated by the main scan image generation unit 131 on the display screen. Then, image diagnosis is performed using the displayed main scan image AI (x, y).

  As described above, in the present embodiment, the map image MI (x, y) in which the SN ratio in the main scan image AI (x, y) generated under the main scan condition is mapped before the main scan is performed. ) Is generated by the map image generation unit 133. Here, based on the reception sensitivity distribution S (x, y) calculated by the reception distribution calculation unit 231 and the transmission sensitivity distribution f (x, y) calculated by the transmission sensitivity distribution calculation unit 232, the map image thereof is displayed. MI (x, y) is generated. Then, the display unit 33 displays the map image MI (x, y) generated by the map image generation unit 133 on the display screen. For this reason, even when the reception sensitivity and the transmission sensitivity are non-uniform, noise is generated in the main scan image AI (x, y) and the image quality is lowered. Since the image quality can be easily confirmed, image diagnosis can be performed efficiently.

  In addition, in this embodiment, the map image generation unit indicates an imaging time required for performing the main scan so that the main scan image AI (x, y) is generated corresponding to the S / N ratio set by the operator. Based on the map image MI (x, y) generated by 133, the imaging time calculation unit 134 calculates. Then, the display unit 33 displays the imaging time calculated by the imaging time calculation unit 134 on the display screen before the main scan is performed. For this reason, since it is possible to easily determine whether or not it is a predetermined imaging time, image diagnosis can be performed efficiently.

  The magnetic resonance imaging apparatus 1 of the above embodiment corresponds to the magnetic resonance imaging apparatus of the present invention. The scanning unit 2 in the above embodiment corresponds to the reference scanning execution unit of the present invention. Moreover, the RF coil part 14 of said embodiment is corresponded to the RF coil part of this invention. The first RF coil 14a of the above embodiment corresponds to the first RF coil of the present invention. Further, the second RF coil 14b of the above embodiment corresponds to the second RF coil of the present invention. The operation unit 32 in the above embodiment corresponds to the SN ratio setting unit of the present invention. Moreover, the display part 33 of said embodiment is corresponded to the display part of this invention. In addition, the reference image generation unit 132 in the above embodiment corresponds to the reference image generation unit of the present invention. Further, the map image generation unit 133 of the above embodiment corresponds to the map image generation unit of the present invention. The imaging time calculation unit 134 of the present embodiment corresponds to the imaging time calculation unit of the present invention. Further, the reception sensitivity distribution calculation unit 231 of the above embodiment corresponds to the reception sensitivity distribution calculation unit of the present invention. Further, the transmission sensitivity distribution calculation unit 232 of the above embodiment corresponds to the transmission sensitivity distribution calculation unit of the present invention. Further, the imaging space B of the above embodiment corresponds to the static magnetic field space of the present invention.

  In implementing the present invention, the present invention is not limited to the above-described embodiment, and various modifications can be employed.

  For example, the present invention may be applied to an imaging method such as single-voxel MRS (magnetic resonance spectroscopy) imaging.

FIG. 1 is a configuration diagram showing a configuration of a magnetic resonance imaging apparatus 1 in an embodiment according to the present invention. FIG. 2 is a block diagram showing the data processing unit 31 in the embodiment according to the present invention. FIG. 3 is a block diagram showing the map image generation unit 133 in the embodiment according to the present invention. FIG. 4 is a flowchart showing an operation when imaging the imaging region of the subject SU in the embodiment according to the present invention. FIG. 5 is a diagram showing a data flow when an imaging region of the subject SU is imaged in the embodiment according to the present invention. FIG. 6 is a diagram showing a display screen displaying the map image MI (x, y) and the imaging time in the embodiment according to the present invention.

Explanation of symbols

1: Magnetic resonance imaging apparatus (magnetic resonance imaging apparatus)
2: Scan unit (reference scan execution unit),
3: Operation console part,
12: Static magnetic field magnet section,
13: Gradient coil part,
14: RF coil part (RF coil part),
14a ... 1st RF coil (1st RF coil),
14b ... 2nd RF coil (2nd RF coil)
15: Cradle,
22: RF drive unit,
23: Gradient drive unit,
24: Data collection unit,
30: control unit,
31: Image generation unit,
32: Operation unit,
33: Display unit (display unit),
34: Storage unit
131: Main scan image generation unit 132: Reference image generation unit (reference image generation unit)
133 ... Map image generation unit (map image generation unit),
134: Imaging time calculation unit (imaging time calculation unit),
231... Reception sensitivity distribution calculation unit (reception sensitivity distribution calculation unit),
232 ... Transmission sensitivity distribution calculation unit (transmission sensitivity distribution calculation unit),
B: Imaging space (static magnetic field space)

Claims (8)

In the static magnetic field space, the RF coil unit transmits an RF pulse to the imaging region of the subject, and a main scan is performed in which the RF coil unit receives a magnetic resonance signal generated in the imaging region to which the RF pulse is transmitted. A magnetic resonance imaging apparatus that generates a main scan image of the imaging region based on a magnetic resonance signal obtained by performing the main scan after performing based on a condition,
A map image generation unit that generates a map image mapping an SN ratio of the main scan image generated under the main scan condition before the main scan is performed;
The map image generation unit
A transmission sensitivity distribution calculating unit that calculates a transmission sensitivity distribution when the RF coil unit transmits the RF pulse in the imaging region;
A reception sensitivity distribution calculation unit that calculates a reception sensitivity distribution when the RF coil unit receives the magnetic resonance signal in the imaging region;
A magnetic resonance imaging apparatus that generates the map image based on the transmission sensitivity distribution calculated by the transmission sensitivity distribution calculation unit and the reception sensitivity distribution calculated by the reception distribution calculation unit. A reference scan in which the RF coil unit transmits an RF pulse to the imaging region in the static magnetic field space and the RF coil unit receives a magnetic resonance signal generated in the imaging region is performed before the main scan is performed. A reference scan execution unit,
A reference image generation unit that generates a reference image for the imaging region based on a magnetic resonance signal obtained by performing the reference scan; and
The RF coil section is
A first RF coil;
A second RF coil having a non-uniform reception sensitivity distribution than the first RF coil in the imaging region,
The reference scan execution unit
A first reference scan in which the first RF coil transmits an RF pulse to the imaging region at a first flip angle, and the first RF coil receives a magnetic resonance signal generated in the imaging region;
A second reference scan in which the first RF coil transmits an RF pulse to the imaging region at the first flip angle, and the second RF coil receives a magnetic resonance signal generated in the imaging region;
The third reference is such that the first RF coil transmits an RF pulse to the imaging region at a second flip angle different from the first flip angle, and the first RF coil receives a magnetic resonance signal generated in the imaging region. And scan as the reference scan,
The reference image generation unit generates a first reference image based on the magnetic resonance signal obtained by performing the first reference scan, and based on the magnetic resonance signal obtained by performing the second reference scan. Generating a second reference image, and generating a third reference image based on the magnetic resonance signal obtained by performing the third reference scan,
The reception sensitivity distribution calculation unit calculates a reception sensitivity distribution based on the first reference image and the second reference image, and the transmission sensitivity distribution calculation unit includes the first reference image and the third reference image. The magnetic resonance imaging apparatus according to claim 1, wherein a transmission sensitivity distribution is calculated based on The reference scan execution unit
3. When performing the third reference scan, the first RF coil transmits an RF pulse to the imaging region so that the second flip angle is half of the first flip angle. 4. Magnetic resonance imaging equipment. The magnetic resonance imaging apparatus according to claim 3, wherein the reference scan execution unit performs each of the first reference scan, the second reference scan, and the third scan by a gradient echo method. The first RF coil is a body coil;
The magnetic resonance imaging apparatus according to claim 2, wherein the second RF coil is a phased array coil. The magnetic resonance imaging apparatus according to claim 1, wherein the map image is generated based on the main scan condition. The magnetic resonance imaging apparatus according to claim 1, further comprising: a display unit that displays the map image generated by the map image generation unit on a display screen before the main scan is performed. An SN ratio setting unit for setting an SN ratio of the main scan image;
Based on the S / N ratio set by the S / N ratio setting unit and the map image generated by the map image generation unit, the main scan image is generated at the S / N ratio set by the S / N ratio setting unit. And an imaging time calculation unit that calculates imaging time when performing the main scan as described above,
The magnetic resonance imaging apparatus according to claim 7, wherein the display unit displays the imaging time calculated by the imaging time calculation unit on the display screen before a main scan is performed.