Magnetic resonance imaging device and computer program product

Abstract

The present invention is entitled a magnetic resonance imaging apparatus and a program. In order to provide a technique that can be used to acquire a FLAIR image and a T1-weighted image in a short scanning time, a magnetic resonance imaging apparatus includes: an RF driver unit 121 for driving an RF coil unit 103; a gradient coil driver unit 122 for driving the gradient coil unit 102; and a controller unit 124 connected to the RF coil driver unit 121 and the gradient coil driver unit 122 for controlling these units so that an imaging sequence ISc with a duration of 1TR for generating echoes from a body part being imaged is repeatedly performed, wherein the imaging sequence ISc has a first sequence part SQ1 including an inversion pulse 11 and an FSE sequence 12 and a second sequence part SQ2 including an inversion pulse 21 and a GRE sequence 22.

Description

Technical Field

[0001] The present invention relates to a magnetic resonance imaging apparatus for acquiring a FLAIR image and a T1-weighted image and a program for causing a processor in the magnetic resonance imaging apparatus to perform a predefined operation. Background Art

[0002] One known medical device for non-invasively capturing images of the inside of a patient's body is an MRI (magnetic resonance imaging) device. The MRI device applies a magnetic field to the patient (rather than irradiating the patient with X-rays) to collect image data. Since the MRI device is thus able to collect image data without exposing the patient to radiation, the MRI device is widely used in medical facilities (such as hospitals) as a medical device that provides a high level of safety.

[0003] Recently, a large number of imaging methods have been developed that can provide MR images that are effective for patient diagnosis. For example, a large number of imaging methods have been developed, including methods that can highlight lesions, methods for reducing the signal intensity from tissues that are not necessary for diagnosis, methods suitable for acquiring images at different time phases, etc.; such imaging methods are highly beneficial in enhancing diagnostic accuracy. By scanning a patient with different imaging methods, various MR images that are beneficial for patient diagnosis can be acquired, so that the patient is scanned with different imaging methods when performing an examination on the patient.

[0004] For example, when examining a patient's head, imaging for acquiring multiple types of MR images (including FLAIR images, T1-weighted images, etc.) is generally performed. The physician forms a diagnosis of the patient with reference to the MR images. FLAIR images can highlight the contrast between white matter and gray matter in the head, while T1-weighted images provide better visualization of the shape of the brain, both of which are beneficial for diagnosis. Therefore, when performing an MR examination on a patient's head, a scan for acquiring a FLAIR image and a scan for acquiring a T1-weighted image are generally performed. Japanese Patent Application Publication No. 2017-051483 discloses an example of acquiring a FLAIR image and / or a T1-weighted image.

[0005] However, when examining a patient, attempting to perform a scan for acquiring a FLAIR image and a scan for acquiring a T1-weighted image in a single examination pass for the purpose of obtaining a plurality of MR images useful for diagnosis causes a problem of prolonged scanning time.

[0006] Therefore, there is a need for a technique by which FLAIR images and T1-weighted images can be acquired in a short scanning time. Summary of the invention

[0007] This summary introduces concepts that are described in more detail in the detailed description. It should not be used to identify essential features of the claimed subject matter, nor should it be used to limit the scope of the claimed subject matter.

[0008] In its first aspect, the present invention is a magnetic resonance imaging apparatus comprising:

[0009] a first driver unit, the first driver unit being used to drive the RF coil unit;

[0010] a second driver unit for driving the gradient coil unit; and

[0011] a controller unit for controlling the first driver unit and the second driver unit so that an imaging sequence having a duration of 1TR and for generating echoes from a body part being imaged is repeatedly performed, wherein

[0012] The imaging sequence has a first sequence part for obtaining a FLAIR image and a second sequence part executed after the first sequence part and for obtaining a T1-weighted image, wherein the first sequence part includes:

[0013] (1a) an α° pulse applied to the body part being imaged; and

[0014] (1b) a spin echo sequence for generating a spin echo from the body part being imaged after the α° pulse has been applied to the body part being imaged for obtaining a FLAIR image, and the second sequence portion comprises:

[0015] (2a) a β° pulse applied to the body part being imaged; and

[0016] (2b) A gradient echo sequence for generating gradient echoes from the body part being imaged after the β° pulse has been applied to the body part being imaged for obtaining a T1-weighted image.

[0017] In its second aspect, the present invention is a program for causing one or more processors to generate control signals for controlling a first driver unit for driving an RF coil unit and a second driver unit for driving a gradient coil unit so that a first sequence portion for obtaining a FLAIR image and a second sequence portion for obtaining a T1-weighted image are executed during 1TR, the first sequence portion comprising:

[0018] (1a) an α° pulse which is applied to the body part being imaged; and

[0019] (1b) a spin echo sequence for generating a spin echo from the body part being imaged after the α° pulse has been applied to the body part being imaged for obtaining a FLAIR image, and the second sequence portion comprises:

[0020] (2a) a β° pulse applied to the body part being imaged; and

[0021] (2b) A gradient echo sequence for generating gradient echoes from the body part being imaged after the β° pulse has been applied to the body part being imaged for obtaining a T1-weighted image.

[0022] In its third aspect, the present invention is one or more non-transitory computer-readable recording media storing one or more instructions executable by one or more processors, the one or more instructions causing the one or more processors to execute operations of controlling a first driver unit for driving an RF coil unit and controlling a second driver unit for driving a gradient coil unit so that a first sequence portion for obtaining a FLAIR image and a second sequence portion for obtaining a T1-weighted image are executed during 1TR, the first sequence portion comprising:

[0023] (1a) an α° pulse which is applied to the body part being imaged; and

[0024] (1b) a spin echo sequence for generating a spin echo from the body part being imaged after the α° pulse has been applied to the body part being imaged for obtaining a FLAIR image, and the second sequence portion comprises:

[0025] (2a) a β° pulse applied to the body part being imaged; and

[0026] (2b) A gradient echo sequence for generating gradient echoes from the body part being imaged after the β° pulse has been applied to the body part being imaged for obtaining a T1-weighted image.

[0027] FLAIR images are useful for patient diagnosis because signals from liquid components such as CSF (cerebrospinal fluid) can be suppressed in the image, and further, a wide T2 contrast can be given between multiple tissues of interest. However, a sequence of FLAIR images requires a longer TR in order to be as unaffected as possible by the T1 value, and therefore, the scanning time for acquiring the FLAIR images is prolonged.

[0028] The inventors of the present application focused on the fact that a long waiting time is required in scanning for FLAIR images, and proposed an idea of ​​utilizing the waiting time in a sequence for FLAIR images as the execution time of a sequence for acquiring T1-weighted images, which are generally used for diagnosis.

[0029] According to the present invention, during 1TR, a sequence portion for collecting spin echoes for FLAIR images is performed, and in addition, a sequence portion for collecting gradient echoes for T1-weighted images is performed. Therefore, data of both FLAIR images and T1-weighted images can be collected during the scan time for acquiring FLAIR images, which makes it possible to reduce the scan time required for acquiring multiple types of MR images. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 is a diagram showing an MRI apparatus in one embodiment of the present invention;

[0031] Figure 2 is an explanatory diagram of an example of obtaining a FLAIR image and a T1-weighted image by a conventional method;

[0032] Figure 3 is an explanatory diagram of the concept of reducing examination time by utilizing a long waiting time w1 in scan A for FLAIR images;

[0033] Figure 4 is a diagram showing an example of scanning performed in the present embodiment;

[0034] Figure 5 is a diagram showing an example of a 3D FSE sequence 12 and a 3D GRE sequence 22;

[0035] Figure 6 is an illustrative diagram of the behavior of longitudinal magnetization in white matter, gray matter, and CSF in the head;

[0036] Figure 7 is a diagram showing the workflow of an MR examination;

[0037] Figure 8 is a diagram showing an example of a region RS to be imaged;

[0038] Fig. 9is an illustrative diagram of variant 1;

[0039] Fig.10 is an illustrative diagram of variant 2;

[0040] Fig.11 is an illustrative diagram of variant 3;

[0041] Fig.12 is an illustrative diagram of variant 4;

[0042] Fig.13 is an illustrative diagram of Variant 5; and

[0043] Fig.14 is a diagram showing an example of an image actually acquired by the technique of the present embodiment; DETAILED DESCRIPTION

[0044] Several embodiments for practicing the present invention will now be described below, although the present invention is not limited thereto.

[0045] Figure 1 is a diagram showing an MRI apparatus in one embodiment of the present invention.

[0046] The MRI apparatus has a magnet 100 .

[0047] The magnet 100 has a superconducting coil unit 101, a gradient coil unit 102, and an RF coil unit 103. The magnet 100 also has an inner wall defining a bore 104 through which an object to be imaged can move.

[0048] The superconducting coil unit 101 applies a static magnetic field in the interior of the bore 104. The gradient coil unit 102 has an x-axis coil, a y-axis coil, and a z-axis coil corresponding to three mutually orthogonal spatial axes (x-axis, y-axis, and z-axis), and applies a gradient field in the interior of the bore 104. The RF coil unit 103 applies an RF pulse in the interior of the bore 104.

[0049] The surface coil 105 is disposed around a body part to be imaged in an object 115 being imaged. The surface coil 105 receives MR signals from the object 115 being imaged.

[0050] The MRI apparatus also has a T / R switch 120 , an RF driver unit 121 , a gradient coil driver unit 122 , a data acquisition unit 123 , a controller unit 124 , a data processing unit 125 , and an operation console unit 126 .

[0051] The T / R switch 120 may connect the RF driver unit 121 to the RF coil unit 103 in a transmission mode, and connect the surface coil 105 to the data acquisition unit 123 in a reception mode.

[0052] The RF driver unit 121 is connected to the controller unit 124, and outputs a driving signal for driving the RF coil unit 103 based on a control signal from the controller unit 124. The RF coil unit 103 transmits RF pulses in response to the driving signal from the RF driver unit 121. In addition, the RF coil unit 103 can be used for transmission and reception to transmit RF pulses, and furthermore receive MR signals.

[0053] The gradient coil driver unit 122 is connected to the controller unit 124, and outputs a driving signal for driving the gradient coil unit 102 based on a control signal from the controller unit 124. The gradient coil unit 102 generates a gradient field in response to the driving signal from the gradient coil driver unit 122. The gradient coil driver unit 122 includes a three-channel driving circuit (not shown) corresponding to three gradient coils (x-axis coil, y-axis coil, and z-axis coil) included in the gradient coil unit 102.

[0054] The data acquisition unit 123 includes a preamplifier (not shown), a phase detector (not shown), and an analog-to-digital (A / D) converter (not shown). The surface coil 105 outputs an analog signal corresponding to the received MR signal, and the analog signal is supplied to the preamplifier in the data acquisition unit 123 via the T / R switch 120. The analog signal is amplified at the preamplifier, the amplified analog signal is phase-detected at the phase detector, and the phase-detected analog signal is converted into a digital signal at the A / D converter. The digital signal thus obtained is output by the controller unit 124 to the data processing unit 125.

[0055] The MRI apparatus also has a table 111. By moving the table 111 based on a control signal from the controller unit 124, an object 115 to be imaged can be moved into the bore 104.

[0056] The controller unit 124 includes a computer and a recording medium having a program to be executed by the computer. The program causes the computer to perform various operations required to perform an inspection on the object being imaged. The recording medium may include, for example, a ROM, a floppy disk, a hard disk, an optical disk, a magneto-optical disk, a CD-ROM, a non-volatile memory, etc. The controller unit 124 outputs a control signal to control the console 111, the RF driver unit 121, the gradient coil driver unit 122, and the data acquisition unit 123. The controller unit 124 also controls the data processing unit 125 based on the operation signal received from the operation console unit 126 to acquire a desired image.

[0057] The operation console unit 126 has an input device and a display device. The input device may include, for example, a mouse, a joystick, a keyboard, a trackball, a touch-operated screen, a light pen, and other input devices. The display device displays an image on a display screen of the display device based on a control signal received from the controller unit 124. The display device displays, for example, a two-dimensional (2D) slice image or a three-dimensional (3D) image of the object 115 being imaged generated by the data processing unit 125.

[0058] The operation console unit 126 can communicate with the controller unit 124 via the link 131. The operator can operate the operation console unit 126 to input data of an imaging protocol and the like to the controller unit 124.

[0059] The data processing unit 125 includes a computer and a recording medium having a program recorded thereon for the computer to perform predefined data processing. The data processing unit 125 is connected to the controller unit 124 and performs data processing based on a control signal received from the controller unit 124. The data processing unit 125 generates an MR image based on the digital signal generated at the data acquisition unit 123.

[0060] The MRI apparatus is thus configured as described above.

[0061] Recently, a large number of imaging methods have been developed that can provide MR images that are effective for patient diagnosis, and various MR images that are beneficial to patient diagnosis can be obtained by scanning patients with different imaging methods. Therefore, when performing an examination on a patient, scanning the patient with different imaging methods is adopted. For example, when examining the patient's head, imaging for obtaining multiple types of MR images (including FLAIR images, T1-weighted images, etc.) is usually performed. However, trying to obtain multiple types of MR images in a single examination session will cause the problem of extended scanning time. Therefore, in order to solve the problem, when obtaining multiple types of MR images in a single examination session, the MRI device in this embodiment performs scanning to achieve the shortest possible examination time. Now the following will refer to the example of obtaining FLAIR images and T1-weighted images to describe the scanning performed in this embodiment. In the following description, in order to clarify the effect of this embodiment, an example of obtaining FLAIR images and T1-weighted images by conventional methods will be described first, and then an example of obtaining FLAIR images and T1-weighted images by the technology of this embodiment will be described.

[0062] Figure 2 is an explanatory diagram of an example of acquiring a FLAIR image and a T1-weighted image by a conventional method.

[0063] refer to Figure 2, showing scan A and scan B. Scan A is used to obtain FLAIR images, while scan B is used to obtain T1-weighted images.

[0064] Scan A can be divided into n segments a1 to an. The duration of each segment in segments a1 to an is 1TR (repetition time). Therefore, the scan time of Scan A is n*TR. Scan B can be divided into m segments b1 to bm. The duration of each segment in segments b1 to bm is 1TR. Therefore, the scan time of Scan B is m*TR. It should be noted that the number of segments n in Scan A and the number of segments m in Scan B can be n=m or n≠m.

[0065] First, the scan A will be described. In each of the sections a1 to an, an imaging sequence for acquiring a FLAIR image is performed. Figure 2 The imaging sequence performed in one segment is shown with reference to segment a2 among segments a1 to an. Each segment includes an inversion pulse 11 and a 3D FSE (fast spin echo) sequence 12 for generating fast spin echoes used in reconstructing FLAIR images.

[0066] On the other hand, in scan B, an imaging sequence for acquiring a T1-weighted image is performed in each of the segments b1 to bm. Figure 2 The imaging sequence performed in one segment is shown with reference to segment b2 among segments b1 to bm. Each segment includes an inversion pulse 21 and a 3D GRE (gradient echo) sequence 22 for generating a gradient echo used in reconstructing a T1-weighted image.

[0067] Therefore, by performing the scan A and the scan B as described above, a FLAIR image and a T1-weighted image can be acquired.

[0068] However, scan A needs to have a longer TR so as to be as unaffected as possible by the T1 value. Therefore, in the duration of 1TR, the time period (waiting time) w1 from the completion of the 3D FSE sequence 12 to the start of the next TR must be longer, which leads to a problem of prolonged scan time for scan A. In addition, since scan A and scan B should be performed to acquire FLAIR images and T1-weighted images, attempting to acquire multiple types of MR images causes another problem of prolonged examination time.

[0069] In order to solve these problems, the inventors of the present application conceived an idea of ​​reducing the examination time by utilizing the fact that the waiting time w1 is long in the scan A for the FLAIR image. Figure 3 is an explanatory diagram of the concept of reducing the examination time using a long waiting time w1 in scan A for FLAIR images.

[0070] For example, 1TR in scan A sometimes has a value of 8 seconds or more. Therefore, the inventors of the present application focused on the fact that the waiting time w1 in imaging sequence 1 in scan A for FLAIR images is long, and proposed the following idea: utilizing the waiting time w1 in imaging sequence 1 as the execution time t2 of imaging sequence 2 (inversion pulse 21 and 3D GRE sequence 22) in scan B for T1-weighted images. Since the execution time t2 of imaging sequence 2 for acquiring T1-weighted images is approximately 3 seconds, for example, imaging sequence 2 for acquiring T1-weighted images can be combined with the waiting time w1 in sequence 1 for FLAIR images. This makes it possible to reduce the examination time for an examination in which multiple types of MR images are acquired. An example of a scan performed based on this idea in the present embodiment will be described below (see Figure 4 ).

[0071] Figure 4 is a diagram showing an example of scanning performed in the present embodiment.

[0072] According to the present embodiment, a scan C is performed. In the scan C, an imaging sequence for generating echoes from a body part being imaged is repeatedly performed.

[0073] Scan C is represented by n segments ci (i=1 to n), i.e., segments c1 to cn. In each segment, an imaging sequence for generating echoes from the body part being imaged is performed. Therefore, in scan C, the number of repetitions of the imaging sequence for generating echoes from the body part being imaged is n. The duration of each of the segments c1 to cn is 1TR. Therefore, the duration of scan C is n*TR.

[0074] Next, the imaging sequence performed in sections c1 to cn will be described.

[0075] refer to Figure 4 , the imaging sequence performed in the sections c1 to cn is represented by an imaging sequence ISc, which is performed in the section i=2 (ie, section c2).

[0076] The imaging sequence ISc includes a sequence portion SQ1 for acquiring FLAIR images and a sequence portion SQ2 for acquiring T1-weighted images.

[0077] The sequence portion SQ1 includes an inversion pulse 11 and a 3D FSE sequence 12. The inversion pulse 11 and the 3D FSE sequence 12 in the sequence portion SQ1 may be, for example, Figure 2 The same as those in scan A shown.

[0078] The inversion pulse 11 is used to invert the longitudinal magnetization of the tissue in the body part being imaged. The 3D FSE sequence 12 is executed at a time point after the waiting time w11 has passed from the inversion pulse 11, and is a 3D sequence for generating a spin echo from the body part being imaged, for producing a FLAIR image. For example, the execution time v12 of the 3D FSE sequence 12 can be set to a value of about 1 second. Although the inversion pulse 11 can generally be a non-selective inversion pulse, the inversion pulse can also be a selective inversion pulse within the range that a FLAIR image with image quality suitable for diagnosis can be acquired.

[0079] The sequence portion SQ2 is executed at a point in time after the waiting time w12 has passed from the sequence portion SQ1. The sequence portion SQ2 includes an inversion pulse 21 and a 3D GRE sequence 22. The inversion pulse 21 and the 3D GRE sequence 22 in the sequence portion SQ2 may be, for example, Figure 2 The same as those in scan B shown.

[0080] The inversion pulse 21 is for inverting the longitudinal magnetization of the tissue in the body part being imaged. The 3D GRE sequence 22 is executed at a time point after the waiting time w21 has passed from the inversion pulse 21, and is a 3D sequence for generating a gradient echo from the body part being imaged, for producing a T1-weighted image. For example, the execution time v22 of the 3D GRE sequence 22 can be set to a value of about 1 second. Although the inversion pulse 21 can generally be a non-selective inversion pulse, the inversion pulse can also be a selective inversion pulse within the range that a T1-weighted image with image quality suitable for diagnosis can be acquired.

[0081] Figure 5 is a diagram showing an example of a 3D FSE sequence 12 and a 3D GRE sequence 22 .

[0082] refer to Figure 5 , a 3D RARE (Rapid Acquisition with Relaxation Enhancement) sequence is shown as an example of the 3D FSE sequence 12 .

[0083] The 3D FSE sequence 12 includes an excitation pulse 50 and refocusing pulses r1, r2, r3, r4,… After applying the excitation pulse 50, refocusing pulses r1, r2, r3, r4,… are applied. For example, the excitation pulse 50 may be a 90° pulse. In the sequence 12, the VFA (variable turning angle) technique is adopted, in which the refocusing pulses r1, r2, r3, r4,… are applied with a variable turning angle. Gphase 1 represents the gradient field applied in the ky direction, and Gphase 2 represents the gradient field applied in the kz direction. Greadout represents the readout gradient field. By applying the refocusing pulses r1, r2, r3, r4,…, echoes ec1, ec2, ec3, ec4,… can be acquired. Here, by executing the 3D FSE sequence 12, u (≥1) spin echoes ec1 to ecu can be collected. Figure 5 , five spin echoes ec1, ec2, ec3, ec4, ecu are shown among u spin echoes collected by the 3D FSE sequence 12. For example, the value of u may be u=200. When u=200, the execution time v12 of the 3D FSE sequence 12 may be, for example, v12≈800 milliseconds.

[0084] The 3D GRE sequence 22 includes subsequences 22_1 to 22_s. Figure 5 , a sequence diagram of the first subsequence 22_1 among the s subsequences 22_1 to 22_s is specifically shown. The subsequence 22_1 includes an excitation pulse 51. For example, the excitation pulse 51 may have a rotation angle less than 90°. SS represents a gradient field applied in a slice selection direction, PE represents a gradient field applied in a phase encoding direction, and FE represents a gradient field applied in a frequency encoding direction. By executing the subsequence 22_1, a gradient echo ecg can be collected. Since the 3D GRE sequence 22 here includes s subsequences 22_1 to 22_s, s gradient echoes can be collected. For example, the value of s may be s=200. When s=200, the execution time v22 of the 3D GRE sequence 22 may be, for example, v22≈1200 milliseconds.

[0085] Next, the longitudinal magnetization behavior of the main tissues in the body part being imaged when executing sequence parts SQ1 and SQ2 will be briefly described. Examples of the main tissues in the body part being imaged considered here are white matter, gray matter and cerebrospinal fluid (hereinafter abbreviated as CSF) in the head.

[0086] Figure 6 is an illustrative diagram of the behavior of longitudinal magnetization in white matter, gray matter, and CSF in the head.

[0087] It is assumed that the longitudinal magnetization in the tissue is Mz=1 until immediately before time point p1. Once the inversion pulse 11 has been applied at time point p1, the longitudinal magnetization of the body part being imaged is reversed to result in a longitudinal magnetization of Mz=-1 in the tissue. The tissue with the reversed longitudinal magnetization undergoes recovery of the longitudinal magnetization according to the T1 value of the tissue. Although the longitudinal magnetization of white matter and gray matter recovers relatively quickly because white matter and gray matter have smaller T1 values, the T1 recovery of CSF is more gradual than that of white matter and gray matter because the T1 value of CSF is significantly larger than that of white matter.

[0088] Then, at a time point p2 after the waiting time w11 has passed, the 3D FSE sequence 12 is performed. The waiting time w11 is set to a certain period of time during which the Mz of the CSF changes from Mz=-1 to Mz=0 (zero point) (or close to Mz=0). Therefore, by performing the 3D FSE sequence 12, spin echoes for acquiring FLAIR images can be collected. For example, the waiting time w11 can be set to a value of about 1.5 seconds. In addition, the waiting time w11 can be set so that the Mz of the CSF reaches Mz=0 (zero point) during the period from the start of the 3D FSE sequence 12 to the completion of the sequence (for example, at a time point p20 between the time point p2 at the start of the 3D FSE sequence 12 and the time point p21 at the completion of the sequence).

[0089] After the 3D FSE sequence 12 is performed at the time point p3 after the waiting time w12 has elapsed, the sequence section SQ2 is performed.

[0090] The recovery of the longitudinal magnetization of the tissue in the body part being imaged is advanced during the waiting time w12, and the inversion pulse 21 of the sequence part SQ2 is applied at the time point p3. Thus, the longitudinal magnetization of the sub-part of the body part being imaged is reversed. Then, the tissue having the reversed longitudinal magnetization undergoes longitudinal magnetization recovery according to the T1 value of the tissue during the waiting time w21. Although white matter and gray matter recover relatively quickly because they have smaller T1 values, the T1 recovery of CSF is more gradual than that of white matter and gray matter because the T1 value of CSF is significantly greater than that of white matter and gray matter.

[0091] Then, at a time point p4 after the waiting time w21 has passed, the 3D GRE sequence 22 is performed. The waiting times w12 and w21 are set so that the longitudinal magnetization of the CSF is restored to a point close to zero, and in addition, the T1 contrast between the white matter and the gray matter is as high as possible. Therefore, by performing the 3D GRE sequence 22, gradient echoes for acquiring T1-weighted images can be collected. For example, the waiting times w12 and w21 can both be set to a value of about 1 second. In addition, the waiting time w21 can be set so that the Mz of the CSF reaches Mz=0 (zero point) during the period from the start of the 3D GRE sequence 22 to the completion of the sequence (for example, at a time point p40 between the time point p4 at the start of the 3D GRE sequence 22 and the time point p41 at the completion of the sequence).

[0092] Although the section c2 is described here, the imaging sequence ISc for generating the spin echo for the FLAIR image and the gradient echo for the T1-weighted image is also performed in other sections (such as in the section c2).

[0093] In scanning C (see Figure 4 ), sequences 12 and 22 are performed while changing the magnetic field strength of the phase encoding gradient fields in sequences 12 and 22 on a segment-by-segment basis so that data for filling k-space is collected. Thus, scan C can be performed to provide a series of echoes required for reconstructing a FLAIR image of a body part being imaged and those echoes for reconstructing a T1-weighted image of the same body part being imaged.

[0094] According to the present embodiment, the sequence portion SQ1 includes the inversion pulse 11 before the 3D FSE sequence 12. However, the sequence portion SQ1 may include an RF pulse having a rotation angle different from 180° in place of the inversion pulse 11 within the range that the FLAIR image acquired by the sequence portion SQ1 may have sufficient quality suitable for diagnosis. Therefore, Figure 4 The inversion pulse 11 shown in FIG. 1 can be generalized as an α° pulse so that the sequence portion SQ1 includes an α° pulse and a 3D FSE sequence 12. For example, the value of α° can be determined on the condition that a FLAIR image with acceptable image quality is obtained, a scan C with as short a scan time as possible is achieved, etc. Typically, α° can be α°=180°. In addition, the α° pulse can be a non-selective pulse or a selective pulse.

[0095] According to the present embodiment, the sequence portion SQ2 includes the inversion pulse 21 before the 3D GRE sequence 22. However, the sequence portion SQ2 may include an RF pulse having a rotation angle different from 180° in place of the inversion pulse 21 within the range that the T1-weighted image acquired by the sequence portion SQ2 may have sufficient quality suitable for diagnosis. Therefore, Figure 5The inversion pulse 21 shown in FIG. 2 can be generalized as a β° pulse so that the sequence portion SQ2 includes a β° pulse and a 3D GRE sequence 22. For example, the value of β° can be determined on the condition that a T1-weighted image with acceptable image quality is obtained, a scan C with as short a scan time as possible is achieved, etc. Typically, β° can be β°=180°. In addition, the β° pulse can be a non-selective pulse or a selective pulse.

[0096] Controller unit 124 (see Figure 1 ) controls the RF driver unit 121 and the gradient coil driver unit 122 so that the above-mentioned imaging sequence ISc is repeatedly performed. In order to control the RF driver unit 121 and the gradient coil driver unit 122, a program is stored in a storage segment in the controller unit 124. The program is used to cause one or more processors to generate control signals, which are used to control the RF driver unit 121 and the gradient coil driver unit 122 so that the above-mentioned imaging sequence ISc is repeatedly performed. The storage segment may include one or more non-transitory computer-readable recording media, in which one or more instructions executable by one or more processors are stored. When the one or more instructions are executed by the processor, the RF driver unit 121 and the gradient coil driver unit 122 are controlled so that the first sequence part SQ1 and the second sequence part SQ2 are performed during 1TR. The first sequence part SQ1 and the second sequence part SQ2 are as follows.

[0097] (1) The first sequence portion SQ1 is used to obtain FLAIR images and includes:

[0098] (1a) an α° pulse which is applied to the body part being imaged; and

[0099] (1b) A 3D FSE sequence 12 for generating spin echoes from the body part being imaged after an α° pulse has been applied to the body part being imaged for obtaining a FLAIR image.

[0100] (2) The second sequence part SQ2 is performed after the first sequence part SQ1 and is used to obtain a T1-weighted image, which includes:

[0101] (2a) a β° pulse which is applied to the body part being imaged; and

[0102] (2b) A gradient echo sequence 22 for generating gradient echoes from the body part being imaged after the β° pulse has been applied to the body part being imaged for obtaining a T1-weighted image. Typically, the α° pulse may be the inversion pulse 11 and the β° pulse may be the inversion pulse 21.

[0103] The above operations may be performed by one processor or by multiple processors. In addition, although the above operations are suitable for being performed by the processor in the controller unit 124 in the present embodiment, it may be performed by a processor separate from the processor in the controller unit 124.

[0104] According to the present embodiment, the 3D FSE sequence 12 is a sequence using the VFA method. However, the 3D FSE sequence 12 is not limited to a sequence using the VFA method, and the sequence may include, for example, a plurality of refocusing pulses (eg, 180° pulses) having the same turning angle.

[0105] In addition, the 3D FSE sequence 12 may include a FR pulse using the FRFSE (fast recovery FSE) technique. Since the FR pulse forces the transverse magnetization to return to the longitudinal magnetization, the recovery of the longitudinal magnetization after the completion of the 3D FSE sequence 12 can be accelerated. Therefore, by incorporating the FR pulse into the 3D FSE sequence 12, the waiting time w12 can be shortened (see Figure 4 ), thus reducing the scan time of scan C.

[0106] In addition, the number u of echoes collected by one 3D FSE sequence 12 and the number s of echoes collected by one 3D GRE sequence 22 may be set to the same value, that is, u=s. However, within the range that a FLAIR image and a T1-weighted image having sufficient quality suitable for diagnosis can be acquired, the numbers u and s may be u≠s. The numbers u and s may also be set such that u=s for some of the segments c1 to cn, and u≠s for other of the segments.

[0107] Next, we will briefly describe the use of Figure 4 Workflow during MR examination of scan C.

[0108] Figure 7 is a diagram showing the workflow of an MR examination.

[0109] At step ST1, the operator makes a scan plan. In the scan plan, the area to be imaged is defined. Figure 8 is a diagram showing an example of a region RS to be imaged. It is assumed here that the body part to be imaged is the brain. Therefore, the operator defines the region RS to be imaged to include the brain. The operator also defines the scanning conditions for performing the scan C.

[0110] At step ST2 , scan C is performed. Since the region RS to be imaged includes the brain, a FLAIR image and a T1-weighted image of the body part including the brain can be acquired by performing scan C.

[0111] Thus completing the flow.

[0112] In scan C, the waiting time w1 in sequence portion SQ1 for FLAIR images is used (see Figure 4 ) The sequence portion SQ2 for T1-weighted images is executed. Since a FLAIR image and a T1-weighted image can be acquired by executing only scan C, the scanning time and / or examination time can be reduced.

[0113] In addition, the area to be imaged RS (see Figure 8 ) is the area to be imaged for the FLAIR image and for the T1-weighted image at the same time. Since this eliminates the need for the operator to separately define the area to be imaged for the FLAIR image and the area to be imaged for the T1-weighted image, the operator's workload can also be lightened. Figure 8 An example of imaging the brain (head) is shown in , but the body part to be imaged is not limited to the brain (head), and the present invention can also be applied to the case where a body part separate from the brain (head) is to be imaged.

[0114] In addition, although Figure 4 The imaging sequence ISc is performed in the scan C in , but the present invention is not limited to the imaging sequence ISc, and an imaging sequence other than the imaging sequence ISc may be performed. Now, several variations of performing an imaging sequence other than the imaging sequence ISc will be described below.

[0115] Fig. 9 is an explanatory diagram of variation 1.

[0116] Fig. 9 Scan D is shown. In scan D, an imaging sequence ISd is performed. Figure 4 ), the imaging sequence ISd is different from the imaging sequence ISd in that the 3D FSE sequence 10 is added. The 3D FSE sequence 10 is placed before the sequence part SQ1. Therefore, in the example of performing the imaging sequence ISd, one or more instructions stored in the recording medium cause the processor to execute the operation of controlling the RF driver unit 121 and the gradient coil driver unit 122, so that these sequences are performed in this order during 1TR.

[0117] The 3D FSE sequence 10 is used to acquire a T2-weighted image. Therefore, according to variant 1, in addition to the FLAIR image and the T1-weighted image, a T2-weighted image can be acquired by executing a scan D. For example, the execution time v10 of the 3D FSE sequence 10 may be a value of about 1 second. The waiting time w10 is placed between the 3D FSE sequence 10 and the sequence portion SQ1. As the waiting time w10 becomes longer, the duration of 1TR becomes longer, and therefore, the scan time of the scan D is extended. Therefore, when it is desired to avoid the extension of the scan time, it is desirable to reduce the waiting time w10 as much as possible. On the other hand, a too short waiting time w10 causes the sequence portion SQ1 to start too early before the longitudinal magnetization of the white matter, gray matter, and CSF is completely restored, which leads to the following risks: the signal intensity from the white matter and gray matter cannot be enhanced, the CSF may show signal inhomogeneity and / or the signal from the CSF cannot be completely suppressed. Therefore, considering both the scan time and image quality of the FLAIR image, it is desirable to set the waiting time w10. For example, the waiting time w10 may be set to a value of approximately 1 second.

[0118] Additionally, the 3D FSE sequence 10 may include a plurality of refocusing pulses having the same turning angle (eg, 180° pulses), or may include FR pulses.

[0119] Fig.10 is an explanatory diagram of variant 2.

[0120] Fig.10 Scan E is shown. In Scan E, an imaging sequence ISe is performed. Fig. 9 ), the imaging sequence ISe differs therefrom in that the sequence portion SQ1 includes a fat suppression pulse 13. The fat suppression pulse 13 precedes the 3DFSE sequence 12. Therefore, in the example of performing the imaging sequence ISe, one or more instructions stored in the recording medium cause the processor to execute the operation of controlling the RF driver unit 121 and the gradient coil driver unit 122, so that the sequences are performed in this order during 1TR, in the 3DFSE sequence 10, the first sequence portion SQ1 including the fat suppression pulse 13, and the second sequence portion SQ2.

[0121] By means of the sequence portion SQ1 including the fat suppression pulse 13 , a FLAIR image with suppressed fat signals can be acquired.

[0122] In addition, a waiting time w13 is placed between the fat suppression pulse 13 and the 3D FSE sequence 12. It is desirable that the waiting time w13 be as short as possible so that the fat suppression effect of the fat suppression pulse 13 can be fully obtained. For example, the waiting time w13 may be set to a value of about several milliseconds.

[0123] Fig.11is an explanatory diagram of variant 3.

[0124] Fig.11 Scan F is shown. In scan F, an imaging sequence ISf is performed. Fig.10 ), the imaging sequence ISf is different therefrom in that the sequence portion SQ2 includes a DANTE (Dysfunctional Delay Precession Customized Excitation) column 23. The DANTE column 23 is added between the inversion pulse 21 and the 3D GRE sequence 22. Therefore, in the example of performing the imaging sequence ISf, one or more instructions stored in the recording medium cause the processor to execute the operation of controlling the RF driver unit 121 and the gradient coil driver unit 122, so that the sequences are performed in this order during 1TR, in the 3D FSE sequence 10, the first sequence portion SQ1 including the fat suppression pulse 13, and the second sequence portion SQ2 including the DANTE column 23.

[0125] By applying the DANTE train 23, a T1-weighted image can be acquired in which the blood vessel signal is further suppressed. For example, the DANTE train 23 may include about 100 DANTE pulses. The DANTE pulses may be non-selective pulses or selective pulses.

[0126] The waiting time w23 is placed between the inversion pulse 21 and the DANTE train 23. Since the blood vessel signal suppression effect of the DANTE train 23 decreases with a longer waiting time w23, it is desirable to set the waiting time w23 as long as possible in consideration of the duration of the DANTE train 23. For example, the waiting time w23 may be set to a value of approximately 800 milliseconds.

[0127] Fig.12 is an explanatory diagram of variation 4.

[0128] Fig.12 Scan G is shown. In Scan G, an imaging sequence ISg is performed. Fig.11 ), the imaging sequence ISg is different therefrom in that the fat suppression pulse 9 is placed before the 3D FSE sequence 10. Therefore, in the example of performing the imaging sequence ISg, one or more instructions stored in the recording medium cause the processor to execute the operation of controlling the RF driver unit 121 and the gradient coil driver unit 122, so that during 1TR, these pulses and sequences are performed in this order: the fat suppression pulse 9, the 3D FSE sequence 10, the first sequence part SQ1 including the fat suppression pulse 13, and the second sequence part SQ2 including the DANTE train 23.

[0129] By applying the fat suppression pulse 9, a T2-weighted image with suppressed fat signals can be acquired.

[0130] In addition, a waiting time w9 is interposed between the fat suppression pulse 9 and the 3D FSE sequence 10. It is desirable that the waiting time w9 be as short as possible so that the fat suppression effect of the fat suppression pulse 9 can be fully obtained. For example, the waiting time w9 may be set to a value of about several milliseconds.

[0131] Fig.13 is an explanatory diagram of variation 5.

[0132] Fig.13 Scan H is shown. In scan H, an imaging sequence ISh is performed. Fig. 9 ), the imaging sequence ISc is different therefrom in that q (≥1) 3D GRE sequences 31, 32, ..., 3q are added after the sequence portion SQ2. Therefore, in the example of performing the imaging sequence ISc, one or more instructions stored in the recording medium cause the processor to execute the operation of controlling the RF driver unit 121 and the gradient coil driver unit 122, so that the sequences are performed in this order during 1TR, namely, the 3D FSE sequence 10, the first sequence portion SQ1, the second sequence portion SQ2, and the q 3D GRE sequences 31 to 3q.

[0133] By adding q 3D GRE sequences 31, 32, ..., 3q, the 3D GRE sequence 22 and the additional q 3D GRE sequences 31, 32, ..., 3q can be performed during 1TR. Since the plurality of 3D GRE sequences are thus performed at different times during 1TR, in addition to the T1-weighted image, an MR image (e.g., a T2* image) and / or a mapping image can be acquired. In addition, the data processing unit 125 (see Figure 1 ) It is possible to obtain various calculated images by using known MR image calculation techniques based on a data set of at least a portion of the overall data collected by the 3D GRE sequence 22 and the 3D GRE sequences 31, 32, ..., 3q.

[0134] In addition, although Fig.13 The imaging sequence ISh in does not include a fat suppression pulse, but the imaging sequence may include a fat suppression pulse as required, such as Figures 10 to 12 shown.

[0135] In the imaging sequences ISc to ISh described previously, the FSE sequence 12 is used to acquire the FLAIR image, and the FSE sequence 10 is used to acquire the T2-weighted image. However, an SE sequence may be used instead of the FSE sequence for collecting a single echo.

[0136] Furthermore, although the above-described FSE sequence 10, FSE sequence 12, GRE sequence 22, and GRE sequences 31 to 3q are 3D sequences, the present invention can be applied to a case where these sequences 10, 12, 22, and 31 to 3q are 2D sequences.

[0137] Next, an image actually acquired by the technique of the present embodiment will be described.

[0138] Fig.14 : is a diagram showing an example of an image actually acquired by the technique of this embodiment.

[0139] Fig.14 The images shown in the upper row of are T2-weighted images, FLAIR images, and T1-weighted images actually acquired by the technique of this embodiment. Fig.10 The scan E shown in FIG. 1 acquires T2-weighted images, FLAIR images, and T1-weighted images. The scan time is 3 minutes.

[0140] As a comparative example, Fig.14 The lower row of shows a T2-weighted image, a FLAIR image, and a T1-weighted image acquired by separate scans. The number of data samples and the image spatial resolution in the comparative example are the same as those in the technology of the present embodiment. In the comparative example, the scanning time of the T2-weighted image is 1 minute 40 seconds, the scanning time of the FLAIR image is 2 minutes 47 seconds, and the scanning time of the T1-weighted image is 1 minute 56 seconds. Therefore, in the comparative example, the scanning time required to acquire these images is a total of 6 minutes 23 seconds.

[0141] Comparing the T2-weighted images, FLAIR images, and T1-weighted images acquired by the technique of the present embodiment with those in the comparative example, the former has image quality comparable to that of the latter. Therefore, it can be seen that by using the technique of the present embodiment, images having image quality equivalent to those in the comparative example can be acquired in half the scanning time in the comparative example.

[0142] The embodiments of the present disclosure shown in the drawings and described above are exemplary embodiments only and are not intended to limit the scope of the appended claims, including any equivalents included within the scope of the claims. Various modifications are possible and will be apparent to those skilled in the art. It is intended that any combination of non-mutually exclusive features described herein is within the scope of the invention. That is, the features of the embodiments may be combined with any appropriate aspect described above, and the optional features of any one aspect may be combined with any other appropriate aspect. Similarly, the features listed in the dependent claims may be combined with non-mutually exclusive features of other dependent claims, particularly where the dependent claims are dependent on the same independent claim. In some jurisdictions that require single claim dependencies, these dependencies may have been used as a practice, but this should not be taken to mean that the features in the dependent claims are mutually exclusive.

Claims

1. A magnetic resonance imaging device, comprising: a first driver unit, the first driver unit being used to drive the RF coil unit; a second driver unit, the second driver unit being used to drive the gradient coil unit; and a controller unit for controlling the first driver unit and the second driver unit so that an imaging sequence having a duration of 1TR and for generating echoes from a body part being imaged is repeatedly performed, wherein The imaging sequence has a first sequence part for obtaining a FLAIR image and a second sequence part executed after the first sequence part and for obtaining a T1-weighted image, wherein the first sequence part includes: (1a) an α° pulse applied to the body part being imaged; and (1b) a spin echo sequence for generating a spin echo from the body part being imaged after the α° pulse has been applied to the body part being imaged for obtaining a FLAIR image, and the second sequence portion comprises: (2a) a β° pulse applied to the body part being imaged; and (2b) A gradient echo sequence for generating gradient echoes from the body part being imaged after the β° pulse has been applied to the body part being imaged for obtaining a T1-weighted image.

2. The magnetic resonance imaging apparatus according to claim 1, wherein: The imaging sequence comprises a further spin echo sequence which is performed before the first sequence part and which is used to generate spin echoes from the body part being imaged for obtaining a T2-weighted image.

3. The magnetic resonance imaging apparatus according to claim 1, wherein: The first sequence portion includes a fat suppression pulse between the α° pulse and the spin echo sequence.

4. The magnetic resonance imaging apparatus according to claim 1, wherein: The second sequence portion includes a DANTE train between the β° pulse and the gradient echo sequence.

5. The magnetic resonance imaging apparatus according to claim 2, wherein: The imaging sequence comprises a fat suppression pulse prior to the further spin echo sequence.

6. The magnetic resonance imaging apparatus according to claim 1, wherein: The imaging sequence includes q gradient echo sequences performed after the second sequence portion.

7. The magnetic resonance imaging apparatus according to claim 6, comprising: a data processing unit for obtaining a calculated image based on a data set of at least a part of the overall data collected by the gradient echo sequence and the q gradient echo sequences.

8. The magnetic resonance imaging apparatus according to claim 1, wherein: The spin echo sequence is a fast spin echo sequence.

9. The magnetic resonance imaging apparatus according to claim 8, wherein: The fast spin echo sequence has multiple refocusing pulses, and The plurality of refocusing pulses are applied to have varying slew angles.

10. The magnetic resonance imaging apparatus according to claim 1, wherein: The number of echoes collected by the spin echo sequence and the number of echoes collected by the gradient echo sequence are equal.

11. The magnetic resonance imaging apparatus according to claim 1, wherein: The α° pulse or the β° pulse is a non-selective pulse.

12. The magnetic resonance imaging apparatus according to claim 1, wherein: The α° pulse or the β° pulse is an inversion pulse.

13. The magnetic resonance imaging apparatus according to claim 1, wherein: The spin echo sequence includes FR pulses.

14. The magnetic resonance imaging apparatus according to claim 5, wherein: The further spin echo sequence comprises FR pulses.

15. A computer program product for causing one or more processors to generate control signals for controlling a first driver unit for driving an RF coil unit and a second driver unit for driving a gradient coil unit so that a first sequence portion for obtaining a FLAIR image and a second sequence portion for obtaining a T1-weighted image are executed during 1TR, the first sequence portion comprising: (1a) an α° pulse which is applied to the body part being imaged; and (1b) a spin echo sequence for generating a spin echo from the body part being imaged after the α° pulse has been applied to the body part being imaged for obtaining a FLAIR image, and the second sequence portion comprises: (2a) a β° pulse, the β° pulse being applied to the body part being imaged; and (2b) A gradient echo sequence for generating gradient echoes from the body part being imaged after the β° pulse has been applied to the body part being imaged for obtaining a T1-weighted image.

Images