KR20160056271A - Method and apparatus for quantifying properties of object through magnetic resonance imaging - Google Patents

Abstract

Disclosed are a method and an apparatus for processing a magnetic resonance image of an object including a first material and a second material through a magnetic resonance imaging apparatus by using multi-parameter mapping (magnetic resonance fingerprinting). According to the present invention, the apparatus comprises: an RF control unit applying a plurality of RF pulses to the object; a data acquisition unit under-sampling first and second magnetic resonance signals; and an imaging processing unit configured to determine a property value for the first and second materials. The present invention provides a magnetic resonance imaging device capable of effectively dividing magnetic resonance signals of different materials.

Description

[0001] METHOD AND APPARATUS FOR QUANTIFYING PROPERTIES OF OBJECT THROUGH MAGNETIC RESONANCE IMAGING [0002]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic resonance imaging apparatus and an image processing method of a magnetic resonance imaging apparatus, and more particularly, to a method and apparatus for distinguishing and quantifying attributes of a target object through a magnetic resonance imaging.

A magnetic resonance imaging (MRI) imaging device is a device that photographs a subject using a magnetic field. It is widely used for diagnosing accurate diseases because it displays the bone, disk, joints, and nerve ligament in three dimensions at a desired angle have.

A magnetic resonance imaging apparatus acquires a magnetic resonance (MR) signal, reconstructs the acquired magnetic resonance signal into an image, and outputs the reconstructed image. Specifically, a magnetic resonance imaging apparatus acquires a magnetic resonance signal using a high-frequency multi-coil including RF coils, a permanent magnet, and a gradient coil.

Specifically, a pulse sequence for generating a radio frequency signal is applied to apply a high-frequency signal to a target through a high-frequency multi-coil, and a magnetic resonance signal (MR signal) generated corresponding to the applied high- And reconstructs the magnetic resonance image by sampling.

Currently, magnetic resonance imaging (MRI) takes about 30 minutes. Generally, a magnetic resonance imaging (MRI) imaging apparatus is formed by a long and narrow barrel (hereinafter referred to as an 'MRI imaging tube'). Therefore, the patient who wants to take a magnetic resonance image should go into the MRI tube and not move during the shooting time. Therefore, it is difficult to take magnetic resonance imaging in patients with ICU or claustrophobia, and even in the case of general patients, as the time taken for imaging becomes longer, the user feels boredom and inconvenience.

Therefore, there is a need for an image processing apparatus and method that can shorten the imaging time of the magnetic resonance imaging.

In order to shorten the imaging time of magnetic resonance imaging, many methods have been tried. For example, without sampling the MR signal for all lines of K-space, the MR signal is undersampled for a constant interval line in K-space and the undersampled K-space data is calibrated to image the final magnetic resonance image Can be used.

For example, GRAPPA (generalized autocalibrating partially parallel acquisitions) is one of the K-space-based imaging methods. It uses self-calibration to measure the spatial interaction value between the calibration signal and the adjacent measured source signal correlations or convolution kernels), and the non-measured signal is estimated using the calculated spatial correlation coefficient, thereby shortening the imaging time of the magnetic resonance image.

Specifically, the Grafu technique uses the measured line data, which is undersampled data, and the additionally obtained ACS line (ACOC line) data, to restore the unrecorded K-space lines by channel do.

As a method for shortening the imaging time of the magnetic resonance imaging and further quantifying a plurality of parameters, multi-parameter mapping can be used. Instead of the classical method of iteratively obtaining data to quantify the parameters of the object, the multi-parameter mapping method is a method in which the magnetic resonance signal of a substance or tissue is physically converted to a physiological signal having a unique signal evolution such as fingerprinting A method of obtaining a pseudorandomized number can be used. For example, as a multi-parameter mapping method, a magnetic resonance fingerprinting method can be used.

The obtained magnetic resonance signal can be converted into a quantitative map by matching the predicted signal development with a pre-recorded signal model.

In multi-parameter mapping, for example, a flip angle and repetition time (TR) of pseudorandom numbers may be used so that the magnetic resonance signal of a material or tissue has a unique signal development.

However, when the flip angle of the pseudo random number and the repetition time (TR) are used, a loss of signal-to-noise ratio (SNR) occurs, and in the case of a signal having a large fat signal or off- there is a problem. Furthermore, problems may arise in which the magnetic resonance signals of different materials are not clearly distinguished. If the magnetic resonance signals are not clearly distinguished, there is a problem that the probability of occurrence of errors in the process of matching with the signal model increases and the reliability of the quantized parameters also falls.

The disclosed embodiments provide a magnetic resonance imaging apparatus and a magnetic resonance imaging apparatus capable of suppressing the occurrence of a signal-to-noise ratio (SNR) loss and effectively quantifying parameters even in the case of a fat signal or a signal having a large off- To provide an image processing method of the present invention.

The disclosed embodiments provide a magnetic resonance imaging apparatus and an image processing method of a magnetic resonance imaging apparatus capable of effectively separating magnetic resonance signals of different materials.

As a technical means for achieving the above-mentioned technical object, a first aspect of the present disclosure relates to a magnetic resonance imaging apparatus, wherein a magnetic resonance imaging apparatus comprises a first object and a second object, A method for processing a resonance image, the method comprising: applying a plurality of RF pulses separated by a first repetition time (TR) and a second repetition time determined on the basis of the first substance and the second substance Sub-sampling the first magnetic resonance signals corresponding to the first material and the second magnetic resonance signals corresponding to the second material in K space, and applying the undersampled first and second magnetic resonance signals, Matching the resonance signals with a signal model for multi-parameter mapping to determine at least one point in the magnetic resonance image for the object, And determining an attribute value corresponding to the second substance.

And wherein the first iteration time and the second iteration time are determined to increase orthogonality between the first magnetic resonance signals and the second magnetic resonance signals .

Further, the first repetition time and the second repetition time may be determined based on a resonance frequency difference between the first substance and the second substance.

The first repetition time is determined so that the first magnetic resonance signals and the second magnetic resonance signals are in-phase, and the second repetition time is determined by the first magnetic resonance signals and the second magnetic resonance signals. Characterized in that the magnetic resonance signals are determined to be out-of-phase.

In addition, the plurality of RF pulses are divided into n repetition times including the first repetition time and the second repetition time, and the n repetition times are defined by the first magnetic resonance signals and the second magnetic repetition time, Characterized in that it is determined to increase the orthogonality between the resonance signals.

Further, the n repetition times may be determined so that the first magnetic resonance signals and the second magnetic resonance signals have a phase difference of (2? K) / n with respect to each other. (k = 1, 2, 3, ..., n)

The plurality of RF pulses may be divided into a first period in which the first repetition time is repeated a plurality of times and a second period in which the second repetition time is repeated a plurality of times.

In addition, the first section and the second section are alternately repeated.

In addition, the number of times the first repetition time is repeated in the first section and the number of times the second repetition time is repeated in the second section are equal to each other.

In addition, an attribute value corresponding to the first substance and the second substance at at least one point in the magnetic resonance image for the subject may be a ratio of the first and the second substance, T1 and T2 of the first substance , T1 and T2 of the second material, and off-resonance between the first material and the second material.

Also, a second aspect of the present disclosure provides an apparatus for processing a magnetic resonance imaging of a subject comprising a first material and a second material, via a multi-parameter mapping, An RF controller configured to apply a plurality of RF pulses to the object, the RF pulse being divided into a first repetition time (TR) and a second repetition time determined based on the first material and the second material; A data acquisition unit configured to undersample the first magnetic resonance signals corresponding to the second material and the second magnetic resonance signals corresponding to the second material in the K space, and a data acquiring unit configured to derive the undersampled first and second magnetic resonance signals and the multi- Matching the signal model for parameter mapping to match the first material and the second material at at least one point in the magnetic resonance image for the object It may provide an apparatus comprising: a video processor configured to determine the attribute value.

And wherein the first iteration time and the second iteration time are determined to increase orthogonality between the first magnetic resonance signals and the second magnetic resonance signals. .

Further, the first repetition time and the second repetition time are determined based on a resonance frequency difference between the first substance and the second substance.

The first repetition time is determined so that the first magnetic resonance signals and the second magnetic resonance signals are in-phase, and the second repetition time is determined by the first magnetic resonance signals and the second magnetic resonance signals. Characterized in that the magnetic resonance signals are determined to be out-of-phase.

In addition, the plurality of RF pulses are divided into n repetition times including the first repetition time and the second repetition time, and the n repetition times are defined by the first magnetic resonance signals and the second magnetic repetition time, Characterized in that it is determined to increase the orthogonality between the resonance signals.

Further, the n repetition times may be determined so that the first magnetic resonance signals and the second magnetic resonance signals have a phase difference of (2? K) / n from each other. (k = 1, 2, 3, ..., n)

The plurality of RF pulses may be divided into a first period in which the first repetition time is repeated a plurality of times and a second period in which the second repetition time is repeated a plurality of times.

In addition, the first section and the second section are alternately repeated.

In addition, the number of times the first repetition time is repeated in the first section and the number of times the second repetition time is repeated in the second section are the same.

In addition, the third aspect of the present disclosure can provide a computer-readable medium having recorded thereon a program for causing a computer to execute the method of the first aspect.

1 is a schematic diagram of a general MRI system.
2 is a detailed view of a communication unit included in the MRI system of FIG.
3 is a block diagram illustrating a magnetic resonance imaging apparatus according to one embodiment.
4 is a view for explaining a voxel and a sub-voxel.
5 is a diagram for explaining a steady state.
6 is a schematic diagram of a pulse sequence according to an embodiment.
7 is a diagram for explaining sampling of a magnetic resonance signal on a three-dimensional K-space.
8 is a diagram for explaining the chemical shift between water and lipid.
FIG. 9 is a flowchart of a method of quantifying an attribute of a target object through a magnetic resonance image according to an exemplary embodiment of the present invention.
10 is a side view of the phantom according to the first experiment and the second experiment.
11A shows an example of a pattern of repetition time (TR).
Fig. 11B shows an example of a pattern of flip angles.
12A to 12D are graphs of signals obtained according to the first experiment.
13A is a proton density map of water and fat for the phantom, obtained according to the first experiment.
13B is a T1 map of water versus phantom and T1 map of fat, obtained according to the first experiment.
13C is a T2 map of water versus phantom and T2 map of fat, obtained according to the first experiment.
13D is an off-resonance map and a B1 phase map of the phantom, obtained according to the first experiment.
14A is a proton density map of water and fat for a living body object obtained according to the first experiment.
14B is a T1 map of water and a T1 map of fat for a living body object obtained according to the first experiment.
14C is a T2 map of water and a T2 map of fat for a living body object obtained according to the first experiment.
14D is an off-resonance map and a B1 phase map for a living body object obtained according to the first experiment.
14E is a table showing T1 and T2 of tissues for a living body object obtained according to the first experiment.
15A shows another example of a pattern of repetition time (TR).
15B shows another example of the pattern of the flip angle.
16A to 16C are graphs of signals obtained according to the second experiment.
17A is a proton density map of water and fat for the phantom, obtained according to the second experiment.
17B is a T1 map of water versus phantom and a T1 map of fat, obtained according to the second experiment.
17C is a T2 map of water versus phantom and T2 map of fat, obtained according to the second experiment.
18A is a proton density map of water and fat for a living body object obtained according to the second experiment.
18B is a T1 map of water and a T1 map of fat for a living body object obtained according to the second experiment.
18C is a T2 map of water and a T2 map of fat for a living body object obtained according to the second experiment.

Brief Description of the Drawings The advantages and features of the present invention, and how to accomplish them, will become apparent with reference to the embodiments described hereinafter with reference to the accompanying drawings. However, it is to be understood that the present invention is not limited to the disclosed embodiments, but may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. It is intended that the disclosure of the present invention be limited only by the terms of the appended claims.

The terms used in this specification will be briefly described and the present invention will be described in detail.

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 certain cases, there may be a term selected arbitrarily by the applicant, in which case the meaning thereof will be described in detail in the description of the corresponding 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 as well, without departing from the spirit or scope of the present invention. Also, as used herein, the term "part " refers to a hardware component such as software, FPGA or ASIC, and" part " However, "part" is not meant to be limited to software or hardware. "Part" may be configured to reside on an addressable storage medium and may be configured to play back one or more processors. Thus, by way of example, and not limitation, "part (s) " refers to components such as software components, object oriented software components, class components and task components, and processes, Subroutines, segments of program code, drivers, firmware, microcode, circuitry, data, databases, data structures, tables, arrays and variables. The functions provided in the components and "parts " may be combined into a smaller number of components and" parts " or further separated into additional components and "parts ".

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily carry out the present invention. In order to clearly explain the present invention in the drawings, portions which are not related to the description will be omitted.

As used herein, an "image" may refer to multi-dimensional data composed of discrete image elements (e.g., pixels in a two-dimensional image and voxels in a three-dimensional image). For example, the image may include an X-ray device, a CT device, an MRI device, an ultrasound diagnostic device, and a medical image of an object acquired by another medical imaging device.

Also, in this specification, an "object" may include a person or an animal, or a part of a person or an animal. For example, the subject may include a liver, a heart, a uterus, a brain, a breast, an organ such as the abdomen, or a blood vessel. The "object" may also include a phantom. A phantom is a material that has a volume that is very close to the density of the organism and the effective atomic number, and can include a spheric phantom that has body-like properties.

In this specification, the term "user" may be a doctor, a nurse, a clinical pathologist, a medical imaging expert or the like as a medical professional and may be a technician repairing a medical device, but is not limited thereto.

In the present specification, the term "MR image (Magnetic Resonance image) " means an image of a target object obtained using the nuclear magnetic resonance principle.

In the present specification, the term "pulse sequence" means a series of signals repeatedly applied in the 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).

In addition, the term " pulse sequence diagram "in this specification describes the order of events occurring in the MRI system. For example, the pulse sequence schematic diagram may be a schematic diagram showing an RF pulse, a gradient magnetic field, an MR signal, and the like over time.

In the present specification, "TR (Repetition Time)" may mean a repetition time of an RF pulse. For example, the repetition time may refer to the time from when the RF pulse of a predetermined size is transmitted to when the RF pulse of the same size is transmitted again.

Further, in the present specification, "TE (Time to Echo)" may mean time until the RF signal is measured after the RF pulse is transmitted.

In addition, in the present specification, the term "spatial encoding" refers to a method of acquiring spatial information along an axis (direction) of an oblique magnetic field by applying a linear oblique magnetic field that causes additional decoupling of a proton spindle, in addition to deconfiguration of a proton spindle by an RF signal It can mean to do.

The MRI system is a device for acquiring an image of a single-layer region of a target object by expressing intensity of an MR (Magnetic Resonance) signal for a RF (Radio Frequency) signal generated in a magnetic field of a specific intensity in contrast. For example, when an object is instantaneously examined and discontinued after an RF signal that lies in a strong magnetic field and resonates only with a specific nucleus (eg, a hydrogen nucleus), the MR signal is emitted from the particular nucleus. MR signals can be received to obtain an MR image. The MR signal means an RF signal radiated from the object. The magnitude of the MR signal can be determined by the concentration of a predetermined atom (e.g., hydrogen) included in the object, the relaxation time T1, the relaxation time T2, and the flow of blood.

Since the hydrogen atom constitutes a water molecule that occupies more than 70% of the human body, the intensity of magnetic resonance signals derived from hydrogen nuclei is greater than the intensity of magnetic resonance signals derived from other kinds of nuclei in the human body. Generally, magnetic resonance imaging is generated using magnetic resonance signals derived from hydrogen nuclei.

The MRI system includes features different from other imaging devices. Unlike imaging devices, such as CT, where acquisitions of images are dependent on the direction of the detecting hardware, the MRI system can acquire oriented 2D images or 3D volume images at any point. Further, unlike CT, X-ray, PET, and SPECT, the MRI system does not expose radiation to the subject and the examiner, and it is possible to acquire images having a high soft tissue contrast, The neurological image, the intravascular image, the musculoskeletal image and the oncologic image can be acquired.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily carry out the present invention. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. In order to clearly illustrate the present invention, parts not related to the description are omitted, and like parts are denoted by similar reference numerals throughout the specification.

1 is a schematic diagram of a general MRI system. Referring to FIG. 1, the MRI system may include a gantry 20, a signal transceiver 30, a monitoring unit 40, a system controller 50, and an operating unit 60.

The gantry 20 blocks electromagnetic waves generated by the main magnet 22, the gradient coil 24, the RF coil 26 and the like from being radiated to the outside. A static magnetic field and an oblique magnetic field are formed in the bore in the gantry 20, and an RF signal is radiated toward the object 10.

The main magnet 22, the gradient coil 24, and the RF coil 26 may be disposed along a predetermined direction of the gantry 20. The predetermined direction may include a coaxial cylindrical direction or the like. The object 10 can be placed on a table 28 insertable into the cylinder along the horizontal axis of the cylinder.

The main magnet 22 generates a static magnetic field or a static magnetic field for aligning the magnetic dipole moment of the nuclei included in the object 10 in a predetermined direction. As the magnetic field generated by the main magnet is strong and uniform, a relatively precise and accurate MR image of the object 10 can be obtained.

Magnets for generating a magnetic field include a permanent magnet, a room temperature electromagnet, and a superconducting electromagnet. The superconducting electromagnet has strong magnetic field and excellent uniformity, and the superconducting electromagnet is mainly used as the main magnet 22. [ For example, if the hydrogen atoms inside the human body are placed in the static field created by the main magnet 22, the direction of the magnetic dipole moment of the hydrogen nuclei becomes aligned in the direction of this static field to go to a lower energy state. Indeed, in order to maintain thermal equilibrium, atomic nuclei in a low energy state are slightly more than atomic nuclei in a high energy state. Here, the energy difference between the atomic nuclei in different energy states is proportional to the intensity of the magnetic field generated by the main magnet 22, and has a unique Larmor frequency. For example, if the intensity of the magnetic field generated by the main magnet 22 is 1 tesla, then the Lambertian frequency of the hydrogen nucleus in this magnetic field is about 42.58 MHz.

The gradient coil 24 includes X, Y, and Z coils that generate a gradient magnetic field in the X-axis, Y-axis, and Z-axis directions orthogonal to each other. The gradient coil 24 can provide position information of each part of the object 10 by inducing resonance frequencies differently for each part of the object 10.

The RF coil 26 can irradiate the RF signal to the patient and receive the MR signal emitted from the patient. Specifically, the RF coil 26 transmits an RF signal having the same frequency as the frequency of the car motions to the nucleus existing in the patient who carries out the car wash motion, stops the transmission of the RF signal, And can receive the MR signal emitted.

For example, the RF coil 26 generates an electromagnetic wave signal having a radio frequency corresponding to the kind of the atomic nucleus, for example, an RF signal, to convert a certain atomic nucleus from a low energy state to a high energy state, 10). When an electromagnetic wave signal generated by the RF coil 26 is applied to an atomic nucleus, the atomic nucleus can be transited from a low energy state to a high energy state. Thereafter, when the electromagnetic wave generated by the RF coil 26 disappears, the atomic nucleus to which the electromagnetic wave has been applied can emit electromagnetic waves having a Lamor frequency while transiting from a high energy state to a low energy state. In other words, when the application of the electromagnetic wave signal to the atomic nucleus is interrupted, the energy level from the high energy to the low energy is generated in the atomic nucleus where the electromagnetic wave is applied, and the electromagnetic wave having the Lamor frequency can be emitted. The RF coil 26 can receive an electromagnetic wave signal radiated from the nuclei inside the object 10. Here, the received electromagnetic wave signal may be referred to as a free induction decay (FID) signal.

The RF coil 26 may be implemented as a single RF transmitting and receiving coil having both a function of generating an electromagnetic wave having a radio frequency corresponding to the type of an atomic nucleus and a function of receiving electromagnetic waves radiated from the atomic nucleus. It may also be implemented as a receiving RF coil having a function of generating an electromagnetic wave having a radio frequency corresponding to the type of an atomic nucleus and a receiving RF coil having a function of receiving electromagnetic waves radiated from the atomic nucleus.

In addition, the RF coil 26 may be fixed to the gantry 20 and may be removable. The removable RF coil 26 may include an RF coil for a portion of the object including a head RF coil, a thorax RF coil, a bridge RF coil, a neck RF coil, a shoulder RF coil, a wrist RF coil, and an ankle RF coil. have.

Also, the RF coil 26 can communicate with an external device by wire and / or wireless, and can perform dual tune communication according to a communication frequency band.

The RF coil 26 may include a birdcage coil, a surface coil, and a transverse electromagnetic coil (TEM coil) according to the structure of the coil.

In addition, the RF coil 26 may include a transmission-only coil, a reception-only coil, and a transmission / reception-use coil according to an RF signal transmitting / receiving method.

In addition, the RF coil 26 may include RF coils of various channels such as 16 channels, 32 channels, 72 channels, and 144 channels.

The gantry 20 may further include a display 29 located outside the gantry 20 and a display (not shown) located inside the gantry 20. It is possible to provide predetermined information to a user or an object through a display located inside and outside the gantry 20.

The signal transmitting and receiving unit 30 controls the inclined magnetic field formed in the gantry 20, that is, the bore, according to a predetermined MR sequence, and can control transmission and reception of the RF signal and the MR signal.

The signal transmitting and receiving unit 30 may include a gradient magnetic field amplifier 32, a transmitting and receiving switch 34, an RF transmitting unit 36, and an RF receiving unit 38.

The gradient magnetic field amplifier 32 drives the gradient coil 24 included in the gantry 20 and generates a pulse signal for generating a gradient magnetic field under the control of the gradient magnetic field control unit 54, . By controlling the pulse signals supplied from the oblique magnetic field amplifier 32 to the gradient coil 24, gradient magnetic fields in the X-axis, Y-axis, and Z-axis directions can be synthesized.

The RF transmitter 36 and the RF receiver 38 can drive the RF coil 26. The RF transmitting unit 36 supplies RF pulses of the Ramore frequency to the RF coil 26 and the RF receiving unit 38 can receive the MR signals received by the RF coil 26.

The transmission / reception switch 34 can adjust the transmission / reception direction of the RF signal and the MR signal. For example, an RF signal may be irradiated to the object 10 through the RF coil 26 during a transmission mode, and an MR signal from the object 10 may be received via the RF coil 26 during a reception mode . The transmission / reception switch 34 can be controlled by a control signal from the RF control unit 56. [

The monitoring unit 40 can monitor or control devices mounted on the gantry 20 or the gantry 20. The monitoring unit 40 may include a system monitoring unit 42, an object monitoring unit 44, a table control unit 46, and a display control unit 48.

The system monitoring unit 42 monitors the state of the static magnetic field, the state of the gradient magnetic field, the state of the RF signal, the state of the RF coil, the state of the table, the state of the device for measuring the body information of the object, You can monitor and control the state of the compressor.

The object monitoring unit 44 monitors the state of the object 10. Specifically, the object monitoring unit 44 includes a camera for observing the movement or position of the object 10, a respiration measuring unit for measuring respiration of the object 10, an ECG measuring unit for measuring the electrocardiogram of the object 10, Or a body temperature measuring device for measuring the body temperature of the object 10. [

The table control unit 46 controls the movement of the table 28 on which the object 10 is located. The table control unit 46 may control the movement of the table 28 in accordance with the sequence control of the sequence control unit 50. [ For example, in moving imaging of a subject, the table control unit 46 may move the table 28 continuously or intermittently according to the sequence control by the sequence control unit 50, , The object can be photographed with a FOV larger than the field of view (FOV) of the gantry.

The display control unit 48 controls the displays located outside and inside the gantry 20. Specifically, the display control unit 48 can control on / off of a display located outside and inside of the gantry 20, a screen to be output to the display, and the like. Further, when a speaker is located inside or outside the gantry 20, the display control unit 48 may control on / off of the speaker, sound to be output through the speaker, and the like.

The system control unit 50 includes a sequence control unit 52 for controlling a sequence of signals formed in the gantry 20 and a gantry control unit 58 for controlling gantry 20 and devices mounted on the gantry 20 can do.

The sequence control section 52 includes an inclination magnetic field control section 54 for controlling the gradient magnetic field amplifier 32 and an RF control section 56 for controlling the RF transmission section 36, the RF reception section 38 and the transmission / reception switch 34 can do. The sequence control unit 52 can control the gradient magnetic field amplifier 32, the RF transmission unit 36, the RF reception unit 38 and the transmission / reception switch 34 in accordance with the pulse sequence received from the operating unit 60. [ Here, the pulse sequence includes all information necessary for controlling the oblique magnetic field amplifier 32, the RF transmitter 36, the RF receiver 38, and the transmitter / receiver switch 34. For example, Information on the intensity of the pulse signal applied to the coil 24, the application time, the application timing, and the like.

The operating unit 60 can instruct the system control unit 50 of the pulse sequence information and can control the operation of the entire MRI system.

The operating unit 60 may include an image processing unit 62, an output unit 64, and an input unit 66 that receive and process the MR signal received by the RF receiving unit 38.

The image processing unit 62 can process the MR signal received from the RF receiving unit 38 to generate MR image data for the object 10.

The image processing unit 62 receives the MR signal received by the RF receiving unit 38 and applies various signal processing such as amplification, frequency conversion, phase detection, low frequency amplification, filtering, and the like to the received MR signal.

The image processing unit 62 arranges digital data in a K-space (for example, a Fourier space or a frequency space) of a memory and performs two-dimensional or three-dimensional Fourier transform on the data The image data can be reconstructed.

If necessary, the image processing unit 62 performs synthesis processing or difference calculation processing (K3 answer-latter processing) on the reconstructed image data (data), and performs synthesis processing or difference processing processing on the reconstructed image data ) Can be performed. The combining process may be an adding process on a pixel, a maximum projection (MIP) process, and the like. Further, the image processing unit 62 can store not only the image data to be reconstructed but also the image data on which the combining process and the difference calculating process have been performed in a memory (not shown) or an external server.

In addition, various signal processes applied to the MR signal by the image processing unit 62 may be performed in parallel. For example, a plurality of MR signals may be reconstructed into image data by applying signal processing to a plurality of MR signals received by the multi-channel RF coil in parallel.

The output unit 64 can output the image data or the reconstructed image data generated by the image processing unit 62 to the user. The output unit 64 may output information necessary for a user to operate the MRI system, such as a UI (user interface), user information, or object information. The output unit 64 may be a speaker, a printer, a CRT display, an LCD display, a PDP display, an OLED display, an FED display, an LED display, a VFD display, a DLP (Digital Light Processing) display, a flat panel display (PFD) Display, transparent display, and the like, and may include various output devices within a range that is obvious to those skilled in the art.

The user can input object information, parameter information, scan conditions, pulse sequence, information on image synthesis and calculation of difference, etc., by using the input unit 66. [ Examples of the input unit 66 may include a keyboard, a mouse, a trackball, a voice recognition unit, a gesture recognition unit, a touch screen, and the like, and may include various input devices within a range obvious to those skilled in the art.

1, the signal transmission / reception unit 30, the monitoring unit 40, the system control unit 50, and the operating unit 60 are shown as separate objects. However, the signal transmission / reception unit 30, the monitoring unit 40, Those skilled in the art will appreciate that the functions performed by the control unit 50 and the operating unit 60, respectively, may be performed in different objects. For example, the image processor 62 described above converts the MR signal received by the RF receiver 38 into a digital signal, but the RF receiver 38 or the RF coil 26 directly converts the MR signal received by the RF receiver 38 into a digital signal. .

The gantry 20, the RF coil 26, the signal transmitting and receiving unit 30, the monitoring unit 40, the system control unit 50 and the operating unit 60 may be connected to each other wirelessly or wired, And a device (not shown) for synchronizing clocks with each other. Communication between the gantry 20, the RF coil 26, the signal transmitting and receiving unit 30, the monitoring unit 40, the system control unit 50 and the operating unit 60 can be performed at a high speed such as LVDS (Low Voltage Differential Signaling) A digital interface, an asynchronous serial communication such as a universal asynchronous receiver transmitter (UART), a hypo-synchronous serial communication, or a CAN (Controller Area Network) can be used. Various communication methods can be used.

The MRI system may further include a communication unit.

2 is a diagram showing a configuration of a communication unit 70 according to an embodiment. The communication unit 70 may be connected to at least one of the gantry 20, the signal transmission / reception unit 30, the monitoring unit 40, the system control unit 50, and the operating unit 60 shown in FIG.

The communication unit 70 can exchange data with other medical devices in a hospital server or a hospital connected through a PACS (Picture Archiving and Communication System), and can transmit and receive data in a digital image and communication (DICOM) Medicine) standards.

2, the communication unit 70 may be connected to the network 80 by wired or wireless communication with the server 92, the medical device 94, or the portable device 96. [

Specifically, the communication unit 70 can transmit and receive data related to the diagnosis of the object through the network 80, and can transmit and receive the medical image captured by the medical device 94 such as CT, MRI, X-ray and the like. Further, the communication unit 70 may receive the diagnosis history of the patient, the treatment schedule, and the like from the server 92 and utilize it for diagnosis of the target object. The communication unit 70 may perform data communication with not only the server 92 in the hospital or the medical device 94 but also the portable device 96 such as a doctor, a customer's mobile phone, a PDA, or a notebook computer.

Also, the communication unit 70 may transmit the abnormality of the MRI system or the medical image quality information to the user via the network 80, and may receive the feedback from the user.

The communication unit 70 may include one or more components that enable communication with an external device and may include, for example, a short range communication module 72, a wired communication module 74 and a wireless communication module 76 have.

The short-range communication module 72 refers to a module for performing short-range communication with a device located within a predetermined distance. The local communication technology according to an exemplary embodiment may include a wireless LAN, a Wi-Fi, a Bluetooth, a zigbee, a Wi-Fi direct, an ultra wideband (UWB) Data Association, Bluetooth Low Energy (BLE), Near Field Communication (NFC), and the like.

The wired communication module 74 is a module for performing communication using an electrical signal or an optical signal. In the wired communication technology according to an exemplary embodiment, wired communication using a pair cable, a coaxial cable, an optical fiber cable, Techniques may be included, as well as wired communication technologies that would be apparent to those skilled in the art.

The wireless communication module 76 transmits and receives a wireless signal to at least one of a base station, an external device, and a server on the mobile communication network. Here, the wireless signal may include various types of data depending on a voice call signal, a video call signal, or a text / multimedia message transmission / reception.

3 is a block diagram illustrating a magnetic resonance imaging apparatus according to one embodiment.

The magnetic resonance imaging apparatus 100 may be any device capable of restoring and / or processing a magnetic resonance image. Specifically, the magnetic resonance imaging apparatus 100 applies RF pulses to a target object through a plurality of channel coils included in a radio frequency multi-coil (not shown), and generates magnetic resonance signals And may be a device for imaging a magnetic resonance image using a signal (MR signal). Further, the MRI apparatus 100 may be a magnetic computing apparatus capable of controlling the acquisition of a magnetic resonance signal in magnetic resonance imaging.

Referring to FIG. 3, a MRI apparatus 100 according to an embodiment of the present invention may include an RF controller 110, a data acquiring unit 120, and an image processor 130.

The magnetic resonance imaging apparatus 100 may be included in the MRI system described with reference to FIGS. 1, the RF control unit 110 of the magnetic resonance imaging apparatus 100 includes an RF control unit 56 or an RF control unit 56 of the MRI system. The data acquisition unit 120 corresponds to the signal transmission and reception unit 30 including the RF reception unit 38 or the RF reception unit 38 of the MRI system and the image processing unit 130 corresponds to the sequence control unit 52, And may correspond to the image processing unit 62 of the MRI system.

The RF control unit 110 measures the signal strength (or signal strength) of the RF pulse applied through the high frequency multi-coil (not shown), the application time, the timing And the like can be controlled. Here, the high frequency multi-coil (not shown) may correspond to the RF coil 26 of the MRI system shown in FIG.

The RF control unit 110 may be connected to the operating unit 60 shown in FIG. 1 or may receive an RF pulse sequence from the operating unit 60 to control the RF pulse.

The magnetic resonance imaging apparatus 100 may further include a gradient magnetic field control unit (not shown). When the magnetic resonance imaging apparatus 100 is included in the MRI system described with reference to FIGS. 1 and 2, the gradient magnetic field control unit (not shown) of the magnetic resonance imaging apparatus 100 controls the gradient magnetic field control unit 54 of the MRI system, Or a sequence controller 50 including a gradient magnetic field control unit 54. [

The magnetic resonance imaging apparatus 100 may apply a spatial encoding gradient to the object through a gradient magnetic field control unit (not shown).

The spatial encoding gradient magnetic field is applied to the object and different resonance frequencies are induced depending on the region of the object, so that the MRI apparatus 100 can acquire position information of each region. The magnetic resonance signal corresponding to the object may include position information that can be expressed in a three-dimensional coordinate system.

Here, the spatial encoding gradient magnetic field may include a slice gradient in the slice direction, a frequency gradient in the frequency direction, and a gradient phase in the phase direction.

The data acquisition unit 120 of the magnetic resonance imaging apparatus 100 may acquire a magnetic resonance signal for reconstructing a magnetic resonance image by taking a magnetic resonance imaging (MRI) image of the object. Here, the magnetic resonance signal may have a form of a radio frequency signal received at each of a plurality of channel coils included in a high frequency multi-coil (not shown) through magnetic resonance imaging.

The data acquisition unit 120 under-samples the magnetic resonance signal in K-space to acquire an undersampled magnetic resonance signal.

The data acquisition unit 120 under-samples a magnetic resonance signal received from each of a plurality of channel coils included in a high frequency multi-coil (not shown) in a regular or non-uniform pattern, It is possible to obtain an undersampled magnetic resonance signal corresponding to each of the channel coils.

The data acquisition unit 120 may transmit the undersampled magnetic resonance signal to the image processing unit 130.

The image processor 130 of the MRI apparatus 100 matches the undersampled MRI signals obtained through the data acquisition unit 120 with a signal model for multi-parameter mapping to determine an attribute value corresponding to the object at at least one point in the magnetic resonance image for the object. Here, the attribute value may be a parameter.

The signal model for the multi-parameter mapping may be referred to as a data model, a magnetic resonance fingerprinting DB (DB), a dictionary, or the like, and may be stored in a memory (not shown) or an external server.

When a signal model for multi-parameter mapping is stored in an external server, the magnetic resonance imaging apparatus 100 may further include a communication unit (not shown) for communicating with an external server, The communication unit 70 described in FIG.

The image processor 130 may generate K-space data using the received magnetic resonance signal. The K-space data can be two-dimensional K-space data or three-dimensional K-space data. For example, the two-dimensional K-space data has a spatial frequency domain of a two-dimensional space, and is represented by a Kx axis corresponding to a frequency encoding and a ky axis corresponding to a phase encoding . The three-dimensional K-space data is formed by the Kx-axis, the Ky-axis, and the Kz-axis corresponding to the traveling direction in space. Here, the Kz axis corresponds to a slice selection gradient.

The magnetic resonance imaging apparatus 100 may be a computing device that operates in conjunction with the MRI system described in FIG. 1 and can control magnetic resonance imaging in the MRI system. In this case, the magnetic resonance imaging apparatus 100 may be connected to the RF coil 26 and the gradient coil 24 included in the MRI system by wire or wireless. The RF control unit 110 of the MRI apparatus 100 may control the RF control unit 56, the gradient magnetic field control unit 54 and the RF coil 26 of the MRI system.

The magnetic resonance imaging apparatus 100 may be a server apparatus that provides a pulse sequence to be applied to a target object, receives a magnetic resonance signal acquired by magnetic resonance imaging, and restores a magnetic resonance image using the received magnetic resonance signal . Here, the server device may be a medical server device in a hospital or other hospital where a patient performs magnetic resonance imaging.

The magnetic resonance imaging apparatus 100 may be a server, a medical apparatus, or a portable apparatus connected to the MRI system described with reference to FIGS. 1 and 2. The magnetic resonance imaging apparatus 100 receives a magnetic resonance signal obtained from the MRI system, Can be performed.

According to one embodiment, the object may be composed of a plurality of materials. For example, a subject may comprise a first material and a second material. Here, the first material may be water, and the second material may be fat, but is not limited thereto.

The RF controller 110 may apply a plurality of RF pulses to the target object, the first and second repetition times being determined based on the first material and the second material. At this time, the first repetition time and the second repetition time may be alternately repeated.

The nuclei contained in the object are excited by RF pulses and then emit magnetic resonance signals. Here, the nuclei contained in the first material are excited by RF pulses and then emit a first magnetic resonance signal, and the nuclei contained in the second material are excited by RF pulses and then emit a second magnetic resonance signal .

The first repetition time and the second repetition time are determined based on the first material and the second material so that the first magnetic resonance signals corresponding to the first material and the second magnetic resonance signals corresponding to the second material The orthogonality can be increased.

When the first magnetic resonance signals corresponding to the first substance and the second magnetic resonance signals corresponding to the second substance are emitted, the data obtaining section 120 receives the first magnetic resonance signals and the second magnetic resonance signals It can be undersampled.

When the undersampled MR signals are obtained, the image processor 130 matches the obtained undersampled MR signals to the signal model for the multi-parameter mapping, so that the MR imaging signals for at least one point in the magnetic resonance image for the object The attribute values corresponding to one substance and the second substance can be determined. Here, one point in the magnetic resonance image may be one voxel. Here, the matching may be template matching.

For example, the attribute value corresponding to the first material and the second material may be a ratio of the first and second materials, T1 and T2 of the first material, T1 and T2 of the second material, Off-resonance between materials, and the like.

The attribute values corresponding to the first substance and the second substance are determined in each voxel in the magnetic resonance image, whereby the magnetic resonance image can be shown as a map according to the attribute value. For example, a magnetic resonance imaging may include a fraction map between the first and second materials, a T1 map and a T2 map of the first material, a T1 map and a T2 map of the second material, An off-resonance map, a B1 phase map of the object, and the like.

According to an embodiment, attribute values corresponding to a plurality of substances included in a target object in each voxel in a magnetic resonance image are determined simultaneously, thereby effectively quantizing various parameters by one scan.

According to one embodiment, the first repetition time and the second repetition time are determined based on the first substance and the second substance included in the object, thereby effectively separating magnetic resonance signals of different substances.

4 is a view for explaining a voxel and a sub-voxel.

As described above, the magnetic resonance image for the object can be composed of voxels. Here, the voxel is graphical information defining one point of the three-dimensional space, and one point may be one volume 200 included in the object.

As shown in FIG. 4, various materials may be included in one volume 200, for example, when the object is a living subject, the volume 200 may include water, fat, blood, muscle, bone, . According to the conventional MRI, when various materials are contained in one volume 200, only one attribute value in which voxels corresponding to the volume 200 complexly interacts with various materials is calculated.

According to the multi-parameter mapping, however, even if various materials are contained in one volume 200, property values corresponding to the respective materials in the voxel corresponding to the volume 200 can be calculated. That is, conceptually, a voxel includes a plurality of sub-voxels, and each substance included in one volume 200 may correspond to each sub-voxel. Therefore, all of the image characteristic values of the sub-voxels included in the voxel can correspond to one voxel.

According to an embodiment, attribute values corresponding to a plurality of substances included in a target object in each voxel in a magnetic resonance image are determined simultaneously, thereby effectively quantizing various parameters by one scan.

5 is a diagram for explaining a steady state.

Here, the steady state may be a state in which the transverse magnetization of the nuclear spindle to which electromagnetic waves have been applied is not completely attenuated.

Referring to FIG. 5, the steady state can be generated according to the relationship between the T2 relaxation time 310 of the nucleus and the repetition time 320. [ Here, the relaxation time T2 is the time from when the RF pulse is transmitted until the time when the transverse magnetization of the nuclear spindle disappears to about 37%, and TR (repetition time) is the time from when the RF pulse of a predetermined size is transmitted Time until the RF pulse is transmitted again.

For example, as shown in FIG. 5A, when the RF control unit 110 applies an RF pulse to a target at intervals of 320 repetition times larger than the T2 relaxation time 310, when a second RF pulse is applied A transverse magnetization of the same magnitude as when the first RF pulse is applied can be generated.

5 (b), when the RF controller 110 applies an RF pulse to the object at a repetition time 340 shorter than that of the T2 330, the transverse magnetization generated by the first RF pulse is completely A second RF pulse is applied in a non-attenuated state, and a magnetic resonance signal generated by the first RF pulse may affect a magnetic resonance signal by the second RF pulse. Thus, the non-fully attenuated transverse magnetization remains a constant size as the RF pulse is repeatedly applied. This state is referred to as a steady state 350. [ The steady state may also be referred to as an equilibrium state or a steady state.

In addition, the remaining transverse magnetization in the steady state can increase the magnitude of the newly generated transverse magnetization by combining with the transverse magnetization that is newly generated (i.e., generated by the next RF pulse).

6 is a schematic diagram of a pulse sequence according to an embodiment.

Referring to FIG. 6, a plurality of RF pulses 411, 412, 413, 421, 422, and 423 included in a pulse sequence according to an exemplary embodiment includes a first repetition time TR1 and a second repetition time TR2. .

At this time, the pulse sequence is applied with RF pulses 411, 412, 413 at intervals of the first repetition time TR1, and when the predetermined condition is reached, the RF pulses 421, 422, 423 may be applied. Although a limited number of RF pulses are shown in FIG. 6, more RF pulses than the number shown may be applied at a first repetition time TR1 interval and a second repetition time TR2 interval.

Here, the pulse sequence diagram is based on the RF pulse 520, the readout gradient (RO), the phase encoding gradient (PE), and the slice selection based on the steady state free wash sequence (SSFP sequence) And a slice selection gradient (SS). Here, the read gradient magnetic field RO may be referred to as a frequency encoding gradient.

According to one embodiment, the magnetic resonance imaging apparatus 100 can control the gradient coil according to a steady state free process (SSFP) technique. Here, the steady state free frequency (SSFP) technique is a technique of acquiring a magnetic resonance image using a steady state, and refocusing a dephased magnetic resonance signal after an RF pulse is transmitted. And a gradient magnetic field sequence.

At this time, the magnetic resonance imaging apparatus 100 can control so that the moment sum of the gradient magnetic field applied to the object is constant during one repetition time. For example, the magnetic resonance imaging apparatus 100 can control the sum of the moments of the gradient magnetic field applied to the object to a value approximate to '0' or '0' during one repetition time. For example, referring to FIG. 6, the gradient magnetic field shown as '+' in each readout gradient magnetic field RO, phase encoding gradient magnetic field PE, and slice selection gradient magnetic field SS and '-' The sum of moments of the gradient magnetic field may be '0'.

Therefore, the oblique magnetic field control unit can apply the oblique magnetic field sequence according to the steady state free wash (SSFP) or the balanced steady state free wash (bSSFP) technique to the object.

Although a pulse sequence of a balanced SSFP (balanced SSFP) technique is shown in FIG. 6, a pulse sequence of various techniques can be used according to an embodiment. For example, gradient echo (GE), spin echo (SE), inversion recovery (IR), short inversion recovery (STIR), fast spin echo (FSE), turbo spin echo (TSE), spoiled gradient recalled echo ), Fast Low Angle Shot (FLASH), Gradient Recalled Acquisition in the Steady State (GRASS), Fast Imaging with Steady State Precession (FISP), REVERSE Fast Imaging with Steady-state Precession (PSIF) Two or more pulse sequences may be used in combination.

The data acquisition unit 120 can receive the magnetic resonance signal emitted from the object through the RF coil (26 in FIG. 1).

The magnetic resonance signal acquired by the data acquisition unit 120 may include a free induction decay (FID) signal and an echo signal. If an oblique magnetic field is applied based on the steady state free car wash (SSFP) sequence, an echo signal may be generated at a TE (Time to Echo) interval equal to or similar to the repetition time.

The data acquisition unit 120 may under-sample the received magnetic resonance signal to obtain an undersampled magnetic resonance signal. Also, the image processing unit 130 can generate the K-space data using the under-sampled magnetic resonance signal and generate the MRI image of the object by performing the Fourier transform on the k-space data.

7 is a diagram for explaining sampling of a magnetic resonance signal on a three-dimensional K-space.

The data acquisition unit 120 of the magnetic resonance imaging apparatus 100 includes eight spokes on a radial trajectory of k-space as shown in Fig. 7 And can acquire magnetic resonance signals corresponding to eight flesh. According to the embodiment, the number of fingers on the radial orbit of the k-space is not limited to eight, and may be implemented in various numbers, and further, the interval between the fingers may be implemented in various ranges.

Although it has been shown that magnetic resonance signals are obtained only for points on a radial orbit in FIG. 7, it is not limited thereto, but various orbits such as spiral trajectory, variable density spiral trajectory, Can be used.

8 is a diagram for explaining the chemical shift between water and lipid.

The resonance frequency of the nuclear magnetic resonance spectrum is changed according to the chemical environment of the atomic nucleus, and this phenomenon is referred to as a chemical shift even in the same atomic nucleus. Can be influenced by the bonding state between atoms and the anisotropy (nonisotropy) of the susceptibility of the surrounding substituent.

For example, referring to FIG. 8, both water and fat contain hydrogen atoms, but their resonant frequencies differ by about 3.5 ppm (parts per million). When the magnetic field strength is 3T, the resonance frequency of water and fat is about 440 Hz. If the magnetic field strength is 1.5T, the resonance frequency of water and fat is about 220 Hz.

Here, φ _off is the phase difference between the magnetic resonance signal frequency of water and fat, Δ f _off is the resonance frequency difference between water and fat, and TE is the echo time. Since the resonance frequency difference? F _off between water and fat is determined according to the intensity of the magnetic field, the phase difference? _Off between the water and fat magnetic resonance signals can be determined by adjusting the echo time.

For example, when the magnetic field strength is 3T, the resonance frequency difference (Δf _off ) between water and fat is about 440 Hz. At this time, when the echo time (TE) is about 1.13 ms, the phase difference (? _Off ) between the water and fat magnetic resonance signals is?. Thus, every 1.13 ms, the magnetic resonance signals of water and fat alternate between in-phase and out-of-phase.

When the oblique magnetic field sequence according to the balanced steady state free car wash (bSSFP: balanced SSFP) technique is applied, the repetition time TR is twice the echo time TE. Therefore, in the odd multiple of the repetition time (TR) of about 2.3 ms, the magnetic resonance signals of water and fat are reversed and the water and fat magnetic resonance signals are in phase.

Thus, in order to increase the orthogonality between water and fat magnetic resonance signals when the subject includes water and fat, the repetition time determined so that the magnetic resonance signals of water and fat are in phase, A plurality of RF pulses separated by the repetition time can be applied to the object.

For example, to increase the orthogonality of water and fat when the subject includes water and fat, the first repeat time (TR1) is about 4.6ms, 9.2ms, 13.8ms, ... , 2.3ms * (2n) (where n is a natural number), and the second repetition time TR2 may be at least 6.9ms, 11.5ms, 16.1ms, ... , 2.3ms * (2n + 1) (where n is a natural number).

For example, the first repetition time TR1 may be about 4.6 ms and the second repetition time TR2 may be about 6.9 ms.

According to an embodiment, a plurality of RF pulses applied to a target object may be divided into first, second, and third repetition times.

For example, the first repetition time may be 4.6 ms, the second repetition time may be 6.9 ms, and the third repetition time may be 9.2 ms.

According to an embodiment, a plurality of RF pulses applied to a target object may be divided into first, second, and fourth repetition times.

For example, the first repetition time may be 4.6 ms, the second repetition time may be 6.9 ms, and the fourth repetition time may be 11.5 ms.

According to an embodiment, the plurality of RF pulses applied to the object may be divided into first, second, third, and fourth repetition times. For example, the first repetition time may be 4.6 ms, the second repetition time may be 6.9 ms, the third repetition time may be 9.2 ms, and the fourth repetition time may be 11.5 ms.

Although water and fat have been described as examples, it is possible to increase the orthogonality between magnetic resonance signals of various materials through the method described above.

In one embodiment, the plurality of RF pulses applied to the object may be divided into n repetition times including first and second repetition times. Here, the n repetition times may be determined to increase the orthogonality between the first magnetic resonance signals and the second magnetic resonance signals. For example, n repetition times may be determined so that the first magnetic resonance signals and the second magnetic resonance signals have a phase difference of (2? K) / n with respect to each other. Here, (k = 1, 2, 3, ..., n). If the plurality of RF pulses are divided into three repetition times, the first and second magnetic resonance signals have a phase difference of (2?) / 3, (4?) / 3, or 2? . If the plurality of RF pulses are divided into two repetition times, that is, as described above, the first and second magnetic resonance signals are divided into first and second repetition times by? Or 2? Respectively.

A plurality of RF pulses, which are divided into a repetition time determined to be in phase with the magnetic resonance signals of the two substances and a repetition time determined to be opposite phase, are applied to the object, thereby increasing the orthogonality between the magnetic resonance signals of the two substances, There is an effect that the magnetic resonance signals of the two substances can be separated and processed easily.

FIG. 9 is a flowchart of a method of quantifying an attribute of a target object through a magnetic resonance image according to an exemplary embodiment of the present invention.

In step S100, the magnetic resonance imaging apparatus 100 applies a plurality of RF pulses, which are divided into a first repetition time and a second repetition time, to the object.

The quanta contained in the object are excited by an applied RF pulse and then emit a magnetic resonance signal while moving in a low energy state. The object comprises a first material and a second material, wherein the quantities included in the first material and the second material are excited by an applied RF pulse and then emit magnetic resonance signals while moving in a low energy state.

The first repetition time and the second repetition time are determined based on the first material and the second material included in the object.

The first repetition time and the second repetition time are determined based on the first material and the second material so that the first magnetic resonance signals corresponding to the first material and the second magnetic resonance signals corresponding to the second material The orthogonality can be increased.

In order to increase the orthogonality between the first magnetic resonance signals and the second magnetic resonance signals, the first repetition time is determined such that the first magnetic resonance signals and the second magnetic resonance signals are in phase, The first magnetic resonance signals and the second magnetic resonance signals may be determined to be in opposite phases.

The magnetic resonance imaging apparatus 100 can receive emitted magnetic resonance signals.

In step S110, the magnetic resonance imaging apparatus 100 under-samples the first magnetic resonance signals corresponding to the first substance and the second magnetic resonance signals corresponding to the second substance, thereby generating undersampled first and second magnetic resonance signals ≪ / RTI >

The magnetic resonance imaging apparatus 100 may acquire magnetic resonance signals corresponding to points shown by dots on a radial trajectory in k-space.

In step S120, the magnetic resonance imaging apparatus 100 matches the obtained undersampled magnetic resonance signals and the signal model for magnetic resonance printing to obtain the first and second materials at at least one point in the magnetic resonance image for the object The corresponding attribute value is determined.

The signal model for magnetic resonance printing stores the predicted signal developments. An undersampled magnetic resonance signal and a signal model for magnetic resonance printing are matched based on pattern recognition to select an entry most similar to an undersampled magnetic resonance signal among the signal developments stored in the signal model, The attribute values corresponding to the entry are determined as attribute values corresponding to the first and second substances at one point in the magnetic resonance image for the subject.

For example, the matching may be performed based on Equation (2).

Where wT1 and wT2 are the T1 and T2 values corresponding to the water contained in the voxel and fT1 and fT2 are the T1 and T2 values corresponding to the fats contained in the voxel , ΔB is the off-resonance value between the first material and the second material in the voxel, and coilphase is a value according to the coil phase effect.

Sig is the acquired magnetic resonance signal, wD (x, B) is the water signal model, and fD (x, B + 440Hz) is the fat signal model. The signal model of water is a model simulated by the Bloch equation, which is a function of wT1, wT2, and ΔB. The local signal model is a model simulated by a block equation functioning as a chemical shift of fT1, fT2, ΔB, and 440 Hz.

That is, when the variables such as F, wT1, wT2, fT1, fT2,? B, and coilphase are changed through the equation (2), the sum of the signal model of the water and the signal of the local signal in the signal model, An entry in which the difference becomes minimum can be determined.

For example, the attribute value corresponding to the first material and the second material may be a ratio of the first and second materials, T1 and T2 of the first material, T1 and T2 of the second material, Off-resonance between materials, and the like.

The attribute values corresponding to the first substance and the second substance are determined in each voxel in the magnetic resonance image, whereby the magnetic resonance image can be shown as a map according to the attribute value. For example, a magnetic resonance imaging may include a fraction map between the first and second materials, a T1 map and a T2 map of the first material, a T1 map and a T2 map of the second material, An off-resonance map, a B1 phase map of the object, and the like.

The attribute values corresponding to the plurality of substances included in the object in each voxel in the magnetic resonance image are determined simultaneously, thereby effectively quantizing various parameters by one scan.

As such, the predicted signal developments are matched to the pre-stored signal model and determined as attribute values corresponding to the first and second materials at points in the magnetic resonance image for the target object, whereby the magnetic resonance imaging apparatus 100 It can be created as a quantitative map.

- First experiment -

Hereinafter, experimental data derived according to the first experiment will be described.

10 is a side view of the phantom according to the first experiment and the second experiment.

The phantom used in the experiment consists of soybean oil, water containing 1% agarose and 0.01% copper sulfate (CuSo4) as shown in Fig. As shown in FIG. 10, as the boundary between water and soybean oil is inclined, the gradient of water and soybean oil in the selected slice changes according to the horizontal axis.

11A shows an example of a pattern of repetition time (TR).

Fig. 11B shows an example of a pattern of flip angles.

11A, in the first experiment, the plurality of RF pulses are divided into a first period 511, 512, 513, 514 and a second repeated period TR2 in which the first repetition time TR1 is repeated a plurality of times And may be divided into a second section 521, 522, 523, and 524 repeated a plurality of times.

Here, the first section and the second section may be alternately repeated, as shown in FIG. 11A.

As described above, to increase the orthogonality of water and fat when the subject includes water and fat, the first repetition time TR1 is about 4.6ms, 9.2ms, 13.8ms, ... , 2.3ms * (2n) (where n is a natural number), and the second repetition time TR2 may be at least 6.9ms, 11.5ms, 16.1ms, ... , 2.3ms * (2n + 1) (where n is a natural number).

Referring to FIG. 11A, in the first experiment, the first repetition time TR1 is about 4.6 ms, and the second repetition time TR2 is about 6.9 ms.

In the first experiment, the first interval 511 is a period in which the first repetition time TR1 is repeated 150 times, and the remaining first intervals 512, 513, and 514 are repeated 50 times And the second intervals 521, 522, 523, and 524 are intervals in which the second repeat time TR2 is repeated 50 times. The number of times the first repetition time TR1 is repeated in the first intervals 512, 513 and 514 and the number of times the second repetition time TR2 is repeated in the second intervals 521, 522, 523 and 524 is The repetition time TR1 may be repeated more than the second intervals 521, 522, 523 and 524, as in the first interval 511. However,

In a first experiment, RF pulses are applied based on a pulse sequence according to the balanced steady state free wash (bSSFP) technique, resulting in a flip angle pattern as shown in Fig. 11B.

On the other hand, banding artifacts occur at 1 / TR (Hz) when a pulse sequence according to the balanced SSFP scheme is used.

However, when the repetition time (TR) pattern shown in FIG. 11A is used, the signal profile is repeated every 1 / TR (Hz) to raise the signal level.

12A to 12D are graphs of signals obtained according to the first experiment.

As shown in FIG. 12A, the evolution of the acquired magnetic resonance signal and the development of the signal that is most similar to its magnetic resonance signal in the signal model is similar.

As described above, by increasing the orthogonality between water and fat, as shown in FIG. 12B, the water and fat signals selected in the signal model exhibit the greatest difference in the case of a reversed phase and the smallest difference in the case of a frost.

FIG. 12C shows the real part of the signals, and FIG. 12D shows the imaginary part of the signals.

The attribute values corresponding to the first substance and the second substance are determined in each voxel in the magnetic resonance image, whereby the magnetic resonance image can be shown as a map according to the attribute value. For example, a magnetic resonance image may be shown as a proton density map of water and fat for the phantom, as shown in FIG. 13A, or as a T1 map of water for the phantom and a T1 map of the fat, Or the off-resonance map? B and the B1 phase map for the phantom as shown in Fig. 13 (c) or T2 map of the water for the phantom and fat T2 map, Lt; / RTI >

14A to 14D, a map based on various attribute values can also be generated for a living body object. 14E is a table showing various attribute values determined for the living body target.

Experiment 1 took 24 seconds per slice when scanning on a 2x2 mm ² , 128x128 matrix, a slice thickness of 5 mm, and a radial locus of k space described in Fig.

As described above, according to the embodiment, it is possible to simultaneously quantize various parameters as shown in Figs. 13A to 13D and Figs. 14A to 14E at a time shorter than that of the conventional technique through multi-parameter mapping have.

- Second experiment -

Hereinafter, experimental data derived according to the second experiment will be described. In the second experiment, the phantom of Fig. 10 was used.

15A shows another example of a pattern of repetition time (TR).

15B shows another example of the pattern of the flip angle.

15A, in the second experiment, the plurality of RF pulses are divided into a first period 611, 612, 613, 614, and 615 in which a first repetition time TR1 is repeated a plurality of times, and a second repetition time TR2 622, 623, and 624 that are repeated a plurality of times.

Here, the first section and the second section may be alternately repeated as shown in FIG. 15A.

As described above, to increase the orthogonality of water and fat when the subject includes water and fat, the first repetition time TR1 is about 4.6ms, 9.2ms, 13.8ms, ... , 2.3ms * (2n) (where n is a natural number), and the second repetition time TR2 may be at least 6.9ms, 11.5ms, 16.1ms, ... , 2.3ms * (2n + 1) (where n is a natural number).

Referring to FIG. 15A, in the second experiment, the first repetition time TR1 is about 4.6 ms, and the second repetition time TR2 is about 6.9 ms.

In the second experiment, the number of times of the first repetition time repeated in each of the first sections 611, 612, 613, 614, and 615 is different from each other. Also, the number of times of the second repetition time repeated in each of the second sections 621, 622, 623, and 624 is also different from each other.

In a second experiment, RF pulses are applied based on a pulse sequence according to the balanced steady state free wash (bSSFP) technique, resulting in a flip angle pattern as shown in Figure 15B.

On the other hand, banding artifacts occur at 1 / TR (Hz) when a pulse sequence according to the balanced SSFP scheme is used.

However, when the repetition time (TR) pattern shown in FIG. 15A is used, the signal profile is repeated every 1 / TR (Hz) to raise the signal level.

16A to 16C are graphs of signals obtained according to the second experiment.

As shown in Fig. 16A, the evolution of the acquired magnetic resonance signal and the development of the signal that is most similar to its magnetic resonance signal in the signal model is similar.

As described above, an increase in the orthogonality of water and fat results in an in-phase effect and an out-of-phase effect, resulting in an increase in the water selected in the signal model And fat signals show the greatest gap in the case of reversals and the smallest difference in the case of frosts.

16C shows the real part of the signals.

The attribute values corresponding to the first substance and the second substance are determined in each voxel in the magnetic resonance image, whereby the magnetic resonance image can be shown as a map according to the attribute value. For example, a magnetic resonance image may be shown as a proton density map of water and fat for the phantom, as shown in FIG. 17A, or as a T1 map of water for the phantom and a T1 map of the fat, Or as a T2 map of water for the phantom and a T2 map of the fat, as shown in Figure 17c.

18A to 18C, a map based on various attribute values can also be generated for a living body object.

As shown in FIGS. 17A to 17C and FIGS. 18A to 18C, according to an embodiment, various parameters can be quantified with a time shorter than that of the conventional technique through multi-parameter mapping.

Experiment 2 required 25 seconds (phantom) per slice and 27 seconds (biomaterial) for 2x2 mm ² , 128x128 matrix, 5 mm slice thickness, and radial locus of k space described in Fig.

The embodiments of the present invention described above can be embodied in a general-purpose digital computer that can be created as a program that can be executed by a computer and operates the program using a computer-readable recording medium.

The computer readable recording medium may be a magnetic storage medium (e.g., a ROM, a floppy disk, a hard disk, etc.), an optical reading medium (e.g., a CD ROM, a DVD or the like), and a carrier wave Transmission).

While the present invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, It will be understood. Therefore, it should be understood that the above-described embodiments are illustrative in all aspects and not restrictive.

Claims (20)

A method for processing a magnetic resonance image of a subject comprising a first material and a second material through a multi-parameter mapping, the magnetic resonance imaging apparatus comprising:
Applying a plurality of RF pulses to a target object, the RF pulses being divided into a first repetition time (TR) and a second repetition time determined based on the first material and the second material;
Undersampling the first magnetic resonance signals corresponding to the first material and the second magnetic resonance signals corresponding to the second material in K space; And
Matching the undersampled first and second magnetic resonance signals with a signal model for multi-parameter mapping to determine at least one location within the magnetic resonance image for the object of the first material and the second material Determining an attribute value corresponding to the attribute value; ≪ / RTI > The method according to claim 1,
Wherein the first iteration time and the second iteration time are determined to increase orthogonality between the first magnetic resonance signals and the second magnetic resonance signals. 3. The method of claim 2,
Wherein the first repetition time and the second repetition time are determined based on a resonant frequency difference between the first material and the second material. The method of claim 3,
Wherein the first repetition time is determined so that the first magnetic resonance signals and the second magnetic resonance signals are in-phase,
Wherein the second repetition time is determined such that the first magnetic resonance signals and the second magnetic resonance signals are out-of-phase. The method according to claim 1,
Wherein the plurality of RF pulses are divided into n repetition times including the first repetition time and the second repetition time,
Wherein the n repetition times are determined to increase orthogonality between the first magnetic resonance signals and the second magnetic resonance signals. 6. The method of claim 5,
Wherein the n repetition times are determined so that the first magnetic resonance signals and the second magnetic resonance signals have a phase difference of (2? K) / n from each other, and k = 1, 2, 3, ... , n. < / RTI >
The method according to claim 1,
Wherein the plurality of RF pulses are divided into a first section in which the first repetition time is repeated a plurality of times and a second section in which the second repetition time is repeated a plurality of times. 8. The method of claim 7,
Wherein the first section and the second section are alternately repeated. 8. The method of claim 7,
Wherein the number of times the first repetition time is repeated in the first section and the number of times the second repetition time is repeated in the second section are the same. The method according to claim 1,
Wherein an attribute value corresponding to the first substance and the second substance at at least one point in the magnetic resonance image for the subject is determined by a ratio of the first and second substances, T1 and T2 of the first substance, Wherein the second material comprises at least one of T1 and T2 of the second material, and off-resonance between the first material and the second material. An apparatus for processing magnetic resonance imaging of a subject comprising a first material and a second material, wherein the magnetic resonance imaging apparatus, via multi-parameter mapping,
An RF controller configured to apply a plurality of RF pulses to a target object, the RF pulses being divided into a first repetition time (TR) and a second repetition time determined based on the first material and the second material;
A data obtaining unit configured to undersample the first magnetic resonance signals corresponding to the first material and the second magnetic resonance signals corresponding to the second material in K space; And
Matching the undersampled first and second magnetic resonance signals with a signal model for multi-parameter mapping to determine at least one location within the magnetic resonance image for the object of the first material and the second material An image processing unit configured to determine an attribute value corresponding to the attribute value; ≪ / RTI > 12. The method of claim 11,
Wherein the first iteration time and the second iteration time are determined to increase orthogonality between the first magnetic resonance signals and the second magnetic resonance signals. 13. The method of claim 12,
Wherein the first repetition time and the second repetition time are determined based on a resonant frequency difference between the first material and the second material. 14. The method of claim 13,
Wherein the first repetition time is determined so that the first magnetic resonance signals and the second magnetic resonance signals are in-phase,
Wherein the second repetition time is determined such that the first magnetic resonance signals and the second magnetic resonance signals are out-of-phase. 12. The method of claim 11,
Wherein the plurality of RF pulses are divided into n repetition times including the first repetition time and the second repetition time,
Wherein the n repetition times are determined to increase orthogonality between the first magnetic resonance signals and the second magnetic resonance signals. 16. The method of claim 15,
Wherein the n repetition times are determined so that the first magnetic resonance signals and the second magnetic resonance signals have a phase difference of (2? K) / n from each other, and k = 1, 2, 3, ... , n. < / RTI >
12. The method of claim 11,
Wherein the plurality of RF pulses are divided into a first period in which the first repetition time is repeated a plurality of times and a second period in which the second repetition time is repeated a plurality of times. 18. The method of claim 17,
Wherein the first section and the second section are alternately repeated. 18. The method of claim 17,
Wherein the number of times the first repetition time is repeated in the first section and the number of times the second repetition time is repeated in the second section are the same. A computer-readable recording medium recording a program for causing a computer to execute the method according to any one of claims 1 to 10.

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