KR101486777B1 - Method and apparatus for acquiring b1 information - Google Patents

Abstract

Generates an RF pulse sequence including a plurality of RF pulses having different flip angles, transmits the generated RF pulse sequence to the object, receives response signals corresponding to the plurality of RF pulses from the object, , And acquires information about the magnetic field (B1) generated by an RF (Radio Frequency) pulse in the MRI system, which obtains B1 information using the received response signals.

Description

METHOD AND APPARATUS FOR ACQUIRING B1 INFORMATION

The present invention relates to a method and apparatus for acquiring information about a magnetic field (B1) generated by an RF pulse in an MRI system, and more particularly, to a method and apparatus for acquiring information about a magnetic field B1 mapping. ≪ / RTI >

The MRI (Magnetic Resonance Imaging) device is noninvasive, has superior contrast of the tissue as compared with the CT device, and has no advantage of artifact caused by the bone tissue. In addition, the MRI system is widely used because it can capture various cross sections according to a desired direction without changing the position of the object.

The MRI apparatus generates an MR image (Magnetic Resonance image) by using a characteristic difference between tissues of an object. That is, the MRI apparatus reflects a difference in magnetic resonance characteristics between tissues of a subject to the MR image, thereby enabling the examinee to easily distinguish the tissues from the MR image.

The uniformity of the magnetic field B1 generated by the RF (Radio Frequency) pulse in the MRI apparatus affects the uniformity of the MR image. Therefore, a technique called B1 shimming is used to increase the uniformity of the magnetic field B1 formed by the RF pulse. The B1 shimming may include a technique of increasing the uniformity of B1 by driving each coil element included in the RF transmission coil including a plurality of coil elements not in one circuit structure with driving signals having different sizes and phases . In order to perform the B1 shimming, the spatial distribution of B1 must be measured in advance, which is generally referred to as B1 mapping.

There are various methods for the B1 mapping method for determining whether the magnetic field B1 generated by the RF pulse is homogeneous or inhomogeneous or the degree of nonuniformity.

Among the B1 mapping methods, the DAM (Double Angle Method) acquires two MR images using RF pulses of different sizes, and calculates a ratio of the signal sizes of the two images to obtain the B1 map. In this case, a long repetition time (TR) corresponding to five times of T1 is required in order to minimize the dependency of the spin lattice relaxation time (T1) of the MR image signal. Therefore, according to the DAM, the B1 mapping takes a long time.

The B1 mapping is not a main shot for diagnosis but an auxiliary shot for obtaining the information necessary to correct the RF pulse. In addition, since the spatial distribution of B1 changes every time the object of MR imaging is changed, it is required to perform the B1 mapping at a high speed because the B1 mapping must be performed every time a new object is photographed.

In order to speed up the B1 mapping, the TR of the RF pulse sequence must be shortened. However, if the TR is shortened, the magnitude of the MR image signal is also affected by T1. Since T1 depends on the type of human tissue, the efficiency of the B1 shimming using the B1 map may be degraded unless the error due to the spin lattice relaxation phenomenon in the B1 mapping is compensated.

An object of the present invention is to provide a B1 information acquisition method and apparatus capable of compensating an error caused by a spin lattice relaxation phenomenon while reducing the time required by B1 mapping.

A method of acquiring information on a magnetic field B1 generated by an RF (Radio Frequency) pulse in an MRI system according to an embodiment of the present invention includes a plurality of RF pulses having different flip angles Generating a sequence of RF pulses; Transmitting the generated RF pulse sequence to a target object; Receiving response signals corresponding to the plurality of RF pulses from the object; And obtaining the B1 information using the received response signals.

The RF pulse sequence according to an embodiment of the present invention may be generated such that a plurality of RF pulses are interleaved in a predetermined time interval.

Also, the RF pulse sequence according to an embodiment of the present invention may include at least three RF pulses. At this time, among the at least three RF pulses, the first RF pulse has a first reclining angle?, The second RF pulse has a second reclining angle?, The third RF pulse has a third reclining angle? The second and third tilt angles [beta] and [gamma] may be different values of a real multiple of the first tilt angle [alpha].

The obtaining of B1 information according to an embodiment of the present invention may include obtaining a first ratio of a ratio of a magnitude S1 of a response signal of the first RF pulse to a magnitude S2 of a response signal of the second RF pulse, Acquiring information; Obtaining second ratio information on a ratio of a magnitude (S2) of a response signal of the second RF pulse and a magnitude (S3) of a response signal of the third RF pulse; And obtaining the first tilt angle alpha of the first RF pulse using the first ratio information and the second ratio information.

The first rate information according to an embodiment of the present invention is obtained by equations (1) and (3), and the second rate information can be obtained by equations (2) and (3).

(1)

(One)

(2)

(2)

(3)

(3)

In the above equations (1) to (3), T1 is the spin lattice relaxation time, and TR may be a predetermined time interval in which the first RF pulse, the second RF pulse, and the third RF pulse are alternately arranged .

In the B1 information acquisition method according to an embodiment of the present invention, the obtained B1 information may include a B1 map (B1 map) indicating the spatial distribution of B1 with respect to the object.

In an MRI system according to an embodiment of the present invention, an apparatus for acquiring information on a magnetic field B1 generated by an RF pulse includes a pulse generating a RF pulse sequence including a plurality of RF pulses having different angle of inclinations A sequence generator; An RF coil for transmitting the generated RF pulse sequence to a target object and receiving response signals corresponding to the plurality of RF pulses from the target object; And a controller for obtaining the B1 information using the received response signals.

The pulse sequence generator according to an embodiment of the present invention may generate an RF pulse sequence such that a plurality of RF pulses are alternately arranged at predetermined time intervals.

Of the at least three RF pulses included in the RF pulse sequence according to an exemplary embodiment of the present invention, the first RF pulse has a first reclining angle alpha, the second RF pulse has a second reclining angle beta, The third RF pulse may have a third reclining angle?, And the second and third reclining angles? And? May be different values of a real multiple of the first reclining angle?.

The controller according to the embodiment of the present invention obtains the first ratio information on the ratio of the magnitude S1 of the response signal of the first RF pulse and the magnitude S2 of the response signal of the second RF pulse A first rate information obtaining unit; A second ratio information obtaining unit for obtaining second ratio information on a ratio of a magnitude (S2) of a response signal of the second RF pulse and a magnitude (S3) of a response signal of the third RF pulse; And a tilt angle acquiring unit that acquires the first tilt angle alpha of the first RF pulse using the first ratio information and the second ratio information.

At this time, the control unit may obtain the first ratio information according to the equations (1) and (3) and obtain the second ratio information according to equations (2) and (3) .

The control unit according to an embodiment of the present invention may include a B1 map showing the spatial distribution of B1 with respect to the object.

Meanwhile, a computer-readable recording medium according to an embodiment of the present invention may record a program for implementing the above-described B1 information acquisition method.

According to the present invention, it is possible to quickly acquire the B1 map while eliminating the problem that an error occurs due to the spin lattice relaxation phenomenon.

The present invention may be readily understood by reference to the following detailed description and the accompanying drawings, in which reference numerals refer to structural elements.
1 is a view for explaining a magnetic resonance imaging system.
2 is a block diagram of a B1 information acquisition apparatus according to an embodiment of the present invention.
3 is a block diagram of an exemplary B1 information acquisition apparatus according to the present invention.
4 is a flowchart of a method for acquiring B1 information according to an embodiment of the present invention.
5 is a flowchart for explaining a step of acquiring B1 information using received response signals in a B1 information acquiring method according to an embodiment of the present invention.
6 is a schematic diagram of an RF pulse sequence transmitted to a subject according to an embodiment of the present invention.
7 is a diagram for explaining a step of acquiring B1 information using received response signals in the B1 information acquiring method according to an embodiment of the present invention.

While the present invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not limited to the disclosed embodiments. Also, in some cases, there is a term arbitrarily selected by the applicant, and in this case, the meaning will be described in detail in the description of the relevant invention. Therefore, the term used in the present invention should be defined based on the meaning of the term, not on the name of a simple term, but on the entire contents of the present invention.

When an element is referred to as "including" an element throughout the specification, it is to be understood that the element may include other elements, without departing from the spirit or scope of the present invention. Furthermore, the term "part" or the like described in the specification means a unit for processing at least one function or operation, which may be implemented by hardware or software, or a combination of hardware and software.

Throughout the specification, the term "subject" may be any entity within a body or animal, including any organ, body or animal. In addition, the object may be a phantom, and a phantom means a material having a volume very close to the biological density and the effective atomic number. For example, a phantom can be a sphere-like water phantom with a body-like nature.

Throughout the specification, the term "user" may be a physician, nurse, clinician, medical imaging expert, etc. as a medical professional and may be, but not limited to, a technician repairing a medical device.

Throughout the specification, the term "pulse sequence" means a series of signals repeatedly applied in an MRI system. The pulse sequence may include a time parameter of the RF pulse, for example, a Repetition Time (TR) and a Time to Echo (TE).

Throughout the specification, the "pulse sequence diagram" describes the sequence of events occurring within the MRI system. For example, the pulse sequence schematic diagram may be a schematic diagram showing at least one of an RF pulse, a gradient magnetic field, and an echo RF signal over time.

FIG. 1 is a view for explaining an MRI system 100. FIG.

Referring to FIG. 1, the object 105 is inspected by a cylindrical gantry in a shielded room where an external RF signal is shielded. In the gantry, a main magnetic field 10 is applied to a main magnetic field B0, And a magnetic field gradient pulse is transmitted by a gradient coil 20 to form a magnetic gradient field.

When the main magnetic field B0 is formed outside the object, atomic nuclei in the object undergo car wash motion along the direction of the main magnetic field B0. The frequency of this oscillatory motion, that is, the resonance frequency, is proportional to the intensity of the main magnetic field B0 according to the Lamor equation. At this time, the proportional constant is called a gyromagnetic ratio.

When an electromagnetic wave having the same frequency as that of the resonance frequency is applied to an atomic nucleus performing a car wash motion, the atomic nucleus causes a resonance phenomenon so that the magnetization vector of the atomic nucleus lies in a direction perpendicular to the main magnetic field (B0) . That is, if an RF pulse having the same frequency as the resonance frequency is transmitted toward an atomic nucleus that carries out a kinetic motion at a resonance frequency, and then the transmission of the RF pulse is stopped, the atomic nucleus emits the energy absorbed from the RF pulse to the outside, A voltage signal is induced in the adjacent RF coil. This voltage signal is called a normal magnetic resonance signal.

Since the magnitude of the magnetic resonance signal is proportional to the magnitude of the magnetization vector and the magnitude of the magnetization vector is proportional to the intensity of the main magnetic field B0, the signal-to-noise ratio of the MR image increases as the intensity of the main magnetic field B0 increases. The MRI system 100 can acquire an MR image using an RF signal emitted from an atomic nucleus.

The RF coil 30 may be used to apply an electromagnetic wave to the object 105 to resonate the magnetization vector in the object 105 and to receive a magnetic resonance signal made by the lying magnetization vector in the vertical plane due to the resonance.

One RF coil may perform both transmission and reception of an RF signal, and an RF coil for transmission only and an RF coil for reception may perform transmission and reception of RF signals, respectively. It is also possible to perform the transmission mode and the reception mode separately using the RF coil for transmission only and the RF coil for reception only.

Since the transmitting coil is generally installed in the gantry of the MRI system 100, it can be made on a cylindrical frame of a size that allows the human body to enter. On the other hand, in many cases, the receiving coil is attached to the object 105 and used. Therefore, when the target object 105 is a human body, it is generally made according to the shape of a human body such as a head coil, a neck coil, and a waist coil.

The RF coil 30 receives an RF signal generated from a predetermined portion of the object 105 and transmits the RF signal to a central control unit 50 of an operating room separate from the shield room. To the MR image. At this time, a weak magnetic field generated by the RF pulse, for example, a magnetic field having an intensity of about 25 mu T is referred to as B1.

Three types of magnetic fields are needed to create magnetic resonance imaging. First, the main magnetic field is needed to magnetize atoms such as hydrogen, phosphorus, and sodium, which cause magnetic resonance among the elements distributed in the human body. Secondly, a spatially linear oblique magnetic field is required. Third, an RF magnetic field, B1, is required to lay down the magnetization vector of the atomized nucleus magnetized to produce the MR image signal on the transverse plane. RF coil 30 can be used to make this B1.

The RF coil 30 used in the MRI system 100 may include a bird-cage RF coil. Cage-type RF coils can produce very uniform B1. However, in a high magnetic field of 3T or more, the uniformity of B1 may be deteriorated by the imaging object of the MR image. Therefore, in a high-field MRI system of 3T or more, B1 shimming may be required to increase the uniformity of B1.

After the MRI system 100 applies the RF pulse to the object through the RF coil 30, the size of the received MR image signal is affected by various physical parameters. For example, there are spin density, spin lattice relaxation time T1, spin spin relaxation time T2, flip angle, and receiving sensitivity of the receiving RF coil. In particular, the ratio between the MR image signals obtained by making the echo time (TE) constant in the pulse sequence to obtain the MR image can be affected by the T1 and the tilt angle.

The pulse sequence used for the B1 mapping may include a spin echo (SE) pulse sequence and a gradient echo (GE) pulse sequence. The present invention is applicable to GE pulse sequences. The GE pulse sequence has the advantage that the TR and TE can be made shorter than the SE pulse sequence and the effect of temperature rise in the human body due to the RF magnetic field is further reduced.

The angle of inclination Θ of the RF pulse in one pixel in the MR image is proportional to the magnitude of B1 in the pixel. Therefore, the spatial distribution of B1, that is, the B1 map, can be obtained from the spatial distribution of the angle of inclination?.

2 is a block diagram of a B1 information acquisition apparatus according to an embodiment of the present invention.

The B1 information acquisition apparatus according to an embodiment of the present invention may be physically separated from the MRI system 100 capable of providing an MR image for a target object using a magnetic resonance principle, or may be an integrated device.

2, the B1 information obtaining apparatus 200 according to an embodiment of the present invention may include a pulse sequence generator 210, an RF coil 220, and a controller 230. However, the B1 information obtaining apparatus 200 may be implemented by a larger number of components than the illustrated components, and the B1 information obtaining apparatus 200 may be implemented by fewer components.

The pulse sequence generator 210 may generate an RF pulse sequence including a plurality of RF pulses having different flip angles. The pulse sequence generation section 210 may generate an RF pulse sequence based on a user's input or based on pulse sequence information stored in a memory (not shown). At this time, the generated RF pulse sequence may include at least three RF pulses.

The RF coil 220 can transmit the RF pulse sequence generated by the pulse sequence generation unit 210 to the object and receive response signals corresponding to a plurality of RF pulses included in the RF pulse sequence from the object. The RF coil 220 may be a single phase or quadrature coil, a surface coil, a volume coil (Helmholtz or solenoid type), or a phased-array coil, for example. Can be implemented.

The control unit 230 can control the overall operation of the B1 information obtaining apparatus 200. [ For example, the control unit 230 can control the pulse sequence generation unit 210, the RF coil 220, and the like by executing programs stored in a memory (not shown). Further, the control unit 230 can control the overall operation of the MRI system 100. In addition, the controller 230 may obtain the B1 information using the response signals received from the RF coil 220. [ On the other hand, the control unit 230 may generate and provide a B1 map indicating the spatial distribution of B1 with respect to the object based on the obtained B1 information. The B1 map may include an image in which the magnitude or phase distribution of the magnetic field formed in the object by the RF pulse is expressed in hue or contrast.

3 is a block diagram of an exemplary B1 information acquisition apparatus according to the present invention.

3, the B1 information obtaining apparatus 200 may include a transmitting unit 322 and a receiving unit 324 in the RF coil 220. As shown in FIG. The B1 information obtaining apparatus 200 may include a first rate information obtaining unit 332, a second rate information obtaining unit 334 and a tilting angle obtaining unit 336 in the control unit 230.

The transmitting unit 322 transmits the RF pulse sequence generated by the pulse sequence generating unit 210 to the object and the receiving unit 324 can receive the response signal corresponding to the RF pulse sequence from the object.

The first ratio information obtaining unit 332 calculates a ratio S1 of the first RF pulse of the at least three RF pulses included in the RF pulse sequence generated by the pulse sequence generating unit 210, The first ratio information on the ratio of the magnitude (S2) of the response signal of the two RF pulses can be obtained. The second ratio information obtaining unit 334 can obtain second ratio information on the ratio of the magnitude (S2) of the response signal of the second RF pulse and the magnitude (S3) of the response signal of the third RF pulse.

The reclining angle obtaining unit 338 may obtain the reclining angle for the first RF pulse using the first rate information and the second rate information.

Hereinafter, a method of acquiring B1 information using the above-described configuration of the B1 information acquiring apparatus 200 shown in FIG. 2 will be described in detail with reference to FIG.

4 is a flowchart of a method for acquiring B1 information according to an embodiment of the present invention.

In step S410, the B1 information obtaining apparatus 200 may generate an RF pulse sequence including a plurality of RF pulses having different flip angles. In this case, the generated RF pulse sequence may be a pulse sequence generated so that a plurality of RF pulses are interleaved and arranged at a predetermined time interval. For example, the RF pulse sequence may include at least three RF pulses. Step S410 may be performed in the pulse sequence generator 210 of FIG.

In step S420, the B1 information obtaining apparatus 200 can transmit the RF pulse sequence generated in step 210 to the object. Step S420 may be performed in the RF coil 220 of FIG. 2 or the transmitter 322 of FIG.

In step S430, the B1 information obtaining apparatus 200 may receive response signals corresponding to the plurality of RF pulses from the object to which the RF pulse sequence is applied. For example, the received response signals may include at least three different RF response signals, each corresponding to at least three different RF pulses included in the RF pulse sequence. Step S430 may be performed in the RF coil 220 of FIG. 2 or in the receiver 324 of FIG.

In step S440, the B1 information obtaining apparatus 200 can obtain B1 information using the response signals received in step S430. Step S440 may be performed in the control unit 230 of FIG. The B1 information obtaining apparatus 200 can acquire MR images based on the received response signals, and obtain B1 map from the obtained MR images.

Hereinafter, the step S440 of obtaining the B1 information by using the response signals received by the B1 information obtaining apparatus 200 according to an embodiment of the present invention will be described in detail with reference to FIG. 5 to FIG.

5 is a flowchart illustrating a step of acquiring B1 information using received response signals in the B1 information acquiring method according to an embodiment of the present invention.

The RF pulse sequence generated in step S410 may include at least a first RF pulse, a second RF pulse, and a third RF pulse.

In step S542, the B1 information obtaining apparatus 200 can obtain the first ratio information on the ratio of the magnitude (S1) of the response signal of the first RF pulse and the magnitude (S2) of the response signal of the second RF pulse.

In step S544, the B1 information obtaining apparatus 200 can obtain the second ratio information on the ratio of the magnitude (S2) of the response signal of the second RF pulse and the magnitude (S3) of the response signal of the third RF pulse.

In step S546, the B1 information obtaining apparatus 200 may obtain the first reclining angle of the first RF pulse using the first rate information and the second rate information. When the second and third RF pulses of the second RF pulse and the third RF pulse have different values of real magnification with respect to the first angle of inclination, the first angle of inclination is the first ratio information and the second ratio information As shown in FIG.

 FIG. 6 is a pulse sequence diagram illustrating an RF pulse sequence transmitted to an object according to an exemplary embodiment of the present invention. Referring to FIG. 6 shows an example of an RF pulse sequence 600 for use in the B1 mapping suggested by the present invention.

Referring to FIG. 6, three RF pulses of different sizes included in an RF pulse sequence transmitted to a target object according to an exemplary embodiment of the present invention may be periodically interleaved with TR intervals.

The tilt angle of the first RF pulse is α, the tilt angle of the second RF pulse is β, and the tilt angle of the third RF pulse is γ. In this case, the angle of the tilt means the angle of the tilt at the position on the object corresponding to the predetermined pixel of the MR image. A size of a signal received corresponding to a predetermined pixel after the first RF pulse is applied to the object is S1, a size of a signal received corresponding to a predetermined pixel after the second RF pulse is applied is S2, The magnitude of a signal received corresponding to a predetermined pixel after the pulse is applied can be expressed by S3. The relative ratios of S1, S2 and S3 in the steady state of the magnetic resonance phenomenon can be determined by the following equations (1) to (3).

In the above equations, T1 may represent the spin lattice relaxation time.

Here, the steady state means a state in which the magnitude of the MR image signal does not change after a sufficiently long period of time while periodically applying the RF pulse sequence and is constantly output. In general, when the RF pulse sequence is applied several tens times, the MR image signal can reach the steady state.

In Equations (1) to (3), the ratio R1 between S1 and S2 and the ratio R2 between S2 and S3 are a function of three reclining angles alpha, beta, gamma and T1. When the second and third reclining angles? And? Satisfy the following formula (4), R1 and R2 are bivariate functions of? And T1.

In the above equations, c1 and c2 may be experimentally predetermined constants.

E1 can be approximated to 1 by approximating E1 to 0 or using very short TR by using a very long TR relative to T1 to exclude the error of the MR image signal by T1.

For example, if B1 mapping is performed by the Double Angle Method (DAM), a long TR corresponding to approximately five times T1 is required to minimize the T1 dependency of the signal. However, in the B1 mapping, there is a problem that the photographing time becomes very long if the TR is lengthened, and there is a limit to shortening the TR by limiting the size of the oblique magnetic field and the rise time.

According to the B1 information acquisition method according to the embodiment of the present invention, R1 and R2 in the equations (1) to (3) can be represented by a nonlinear function of? And T1. Therefore, by solving the two-variable nonlinear simultaneous equations for R1 and R2 irrespective of the long and short TR, the values of α and T1 in a given pixel can be obtained. Therefore, not only in the case of TR < T1 but also in the case of setting TR to 5 to 20% of T1, very fast B1 mapping is possible and consequently MR imaging time can be reduced.

7 is a view for explaining a step of acquiring B1 related information using received response signals in the B1 related information acquiring method according to an embodiment of the present invention.

For example, the ratio R1 and R2 of the magnitude of the response signal obtained by applying the RF pulse sequence including the three RF pulses having the tilt angle?,? = 2?,? = 4? Can be expressed as

In Fig. 7, the abscissa axis represents the value of T1, and the ordinate axis represents the alpha value. The point at which the two curves represented by the R1 value and the R2 value obtained according to an embodiment of the present invention meet can represent the tilt angle and T1 value in a predetermined pixel. Since R1 and R2 are in a nonlinear relationship as shown in Fig. 7, a numerical method can be used to obtain the solution, that is, a and T1.

To create the B1 map, we need to calculate R1 and R2 for all the pixels and obtain the tilt angle based on the calculation result.

 As suggested in the present invention, the B1 information acquisition apparatus 200 has various advantages in that a plurality of RF pulses of different sizes are alternately and periodically applied within a single RF pulse sequence. For example, when three independent pulse sequences composed of three RF pulses are sequentially applied, three elapsed periods are required until each pulse sequence enters a steady state. On the other hand, when three RF pulses are alternately applied in one RF pulse sequence as in the present invention, since only one elapsed period is required, the imaging time can be reduced.

Also, when three RF pulses are alternately applied in one RF pulse sequence as in the present invention, the response signals for the respective RF pulses are received at the same time as they are, compared to sequentially applying three independent pulse sequences, The error due to the movement of the target object, the drift of the offset current of the oblique magnetic field, and the output fluctuation of the amplifier during shooting is reduced, and artifacts in the resultant image can be reduced.

The method according to an embodiment of the present invention can be implemented in the form of a program command which can be executed through various computer means and recorded in a computer-readable medium. The computer-readable medium may include program instructions, data files, data structures, and the like, alone or in combination. The program instructions recorded on the medium may be those specially designed and constructed for the present invention or may be available to those skilled in the art of computer software. Examples of computer-readable media include magnetic media such as hard disks, floppy disks and magnetic tape; optical media such as CD-ROMs and DVDs; magnetic media such as floppy disks; Magneto-optical media, and hardware devices specifically configured to store and execute program instructions such as ROM, RAM, flash memory, and the like. Examples of program instructions include machine language code such as those produced by a compiler, as well as high-level language code that can be executed by a computer using an interpreter or the like.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, It belongs to the scope of right.

Claims (15)

A method for acquiring information on a magnetic field (B1) generated by an RF (Radio Frequency) pulse in an MRI system,
Generating an RF pulse sequence comprising a plurality of RF pulses having different flip angles;
Transmitting the generated RF pulse sequence to a target object;
Receiving response signals corresponding to the plurality of RF pulses from the object; And
And obtaining the B1 information using the received response signals,
Wherein the RF pulse sequence comprises at least three RF pulses,
Wherein the first RF pulse has a first tilt angle?, The second RF pulse has a second tilt angle?, The third RF pulse has a third tilt angle?
The step of acquiring the B1 information comprises:
Obtaining a first ratio information on a ratio of a magnitude (S1) of a response signal of the first RF pulse and a magnitude (S2) of a response signal of the second RF pulse;
Obtaining second ratio information on a ratio of a magnitude (S2) of a response signal of the second RF pulse and a magnitude (S3) of a response signal of the third RF pulse; And
And obtaining the first tilt angle alpha of the first RF pulse using the first ratio information and the second ratio information. The method according to claim 1,
Wherein the RF pulse sequence is generated such that the at least three RF pulses are interleaved at predetermined time intervals. delete The method according to claim 1,
And the third and third reclining angles? Are different values of a real multiple of the first reclining angle?. The method according to claim 1,
The first rate information is obtained by equations (1) and (3)
The second rate information is obtained by equations (2) and (3)

(One)

(2)

(3)
In the above equations (1) to (3), T1 is the spin lattice relaxation time, TR is a predetermined time interval in which the first RF pulse, the second RF pulse, and the third RF pulse are alternately arranged, B1 Information acquisition method. 6. The method of claim 5,
The step of obtaining the first &lt; RTI ID = 0.0 &gt;
And obtaining the first tilt angle alpha and the spin lattice relaxation time T1 as the solutions of the equations (1) to (3) above. The method according to claim 1,
Wherein the obtained B1 information includes a B1 map (B1 map) indicating a spatial distribution of B1 with respect to the object. 1. An apparatus for acquiring magnetic field (B1) information generated by an RF (Radio Frequency) pulse in an MRI system,
A pulse sequence generator for generating an RF pulse sequence including a plurality of RF pulses having different flip angles;
An RF coil for transmitting the generated RF pulse sequence to a target object and receiving response signals corresponding to the plurality of RF pulses from the target object; And
And a control unit for obtaining the B1 information using the received response signals,
Wherein the RF pulse sequence comprises at least three RF pulses,
Wherein the first RF pulse has a first tilt angle?, The second RF pulse has a second tilt angle?, The third RF pulse has a third tilt angle?
Wherein,
A first ratio information obtaining unit for obtaining first ratio information on a ratio of a magnitude (S1) of a response signal of the first RF pulse to a magnitude (S2) of a response signal of the second RF pulse;
A second ratio information obtaining unit for obtaining second ratio information on a ratio of a magnitude (S2) of a response signal of the second RF pulse and a magnitude (S3) of a response signal of the third RF pulse; And
And a tilt angle acquiring unit that acquires the first tilt angle alpha of the first RF pulse using the first ratio information and the second ratio information. 9. The method of claim 8,
Wherein the pulse sequence generator comprises:
Wherein the RF pulse sequence is generated such that the at least three RF pulses are interleaved at predetermined time intervals. delete 9. The method of claim 8,
Wherein the second and third reclining angles? And? Are different from each other with respect to the first reclining angle?. 9. The method of claim 8,
Wherein,
Obtaining the first ratio information by means of equations (1) and (3), acquiring the second ratio information by means of equations (2) and (3)

(One)

(2)

(3)
In the above equations (1) to (3), T1 is the spin lattice relaxation time, TR is a predetermined time interval in which the first RF pulse, the second RF pulse, and the third RF pulse are alternately arranged, B1 Information acquisition device. 13. The method of claim 12,
Wherein,
And obtains the first tilt angle alpha and the spin lattice relaxation time T1 as the solutions of the equations (1) to (3). 9. The method of claim 8,
Wherein the control unit obtains the B1 information including the B1 map (B1 map) indicating the spatial distribution of B1 with respect to the object. A computer-readable recording medium on which a program for implementing the B1 information obtaining method of claim 1 is recorded.

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