# US 10,502,804 B2 · Magnetic resonance imaging apparatus and method of controlling the same

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- Number: US 10,502,804 B2
- Document ID: US10502804B2
- Status: Granted
- Kind: B2
- Application number: 15/680,978
- Filed: 2017-08-18
- Published: 2018-07-26
- Granted: 2019-12-10
- Earliest claimed: 2017-01-20
- Assignees: Samsung Electronics Co., Ltd.; Korea Advanced Institute of Science and Technology
- Applicants: Samsung Electronics Co., Ltd.; Korea Advanced Institute of Science and Technology
- Inventors: Hyun Wook Park; Jae Jin Cho; Dongchan Kim; Hyunseok Seo; Kinam Kwon; Seohee So
- Web page: https://patentgrep.com/patent/US10502804B2

## CPC

- G01R 33/56527: {due to chemical shift effects}
- G01R 33/4835: {of multiple slices}
- G01R 33/5608: {Data processing and visualization specially adapted for MR, e.g. for feature analysis and pattern recognition on the basis of measured MR data, segmentation of measured MR data, edge contour detection on the basis of measured MR data, for enhancing measured MR data in terms of signal-to-noise ratio by means of noise filtering or apodization, for enhancing measured MR data in terms of resolution by means for deblurring, windowing, zero filling, or generation of gray-scaled images, colour-coded images or images displaying vectors instead of pixels (image data processing or generation, in general G06T)}
- G01R 33/5611: {Parallel magnetic resonance imaging, e.g. sensitivity encoding [SENSE], simultaneous acquisition of spatial harmonics [SMASH], unaliasing by Fourier encoding of the overlaps using the temporal dimension [UNFOLD], k-t-broad-use linear acquisition speed-up technique [k-t-BLAST], k-t-SENSE (structural details of arrays of sub-coils G01R33/3415)}
- G01R: MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES (indicating correct tuning of resonant circuits H03J3/12)

## Abstract

A method of controlling a magnetic resonance imaging (MRI) apparatus including performing, by the MRI apparatus, blipped-controlled aliasing parallel imaging (blipped-CAIPI) obtaining k-space data on a subject determining a phase error of a chemical shift component, wherein the phase error of the chemical shift component is proportional to a geometric error based on a resonant frequency difference between a main component and the chemical shift component in the subject comparing the k-space data with data in which the phase error of the chemical shift component is reflected, wherein the data in which the phase error of the chemical shift component is reflected is associated with data on the main component and data on the chemical shift component and determining final data for image restoration based on a result of the comparison.

## Claims

### Claim 1

A method of controlling a magnetic resonance imaging (MRI) apparatus, the method comprising:
performing, by the MRI apparatus, blipped-controlled aliasing parallel imaging (blipped-CAIPI);
obtaining k-space data on a subject;
determining a phase error of a chemical shift component, wherein the phase error of the chemical shift component is proportional to a geometric error based on a resonant frequency difference between a main component and the chemical shift component in the subject;
comparing the k-space data with data in which the phase error of the chemical shift component is reflected, wherein the data in which the phase error of the chemical shift component is reflected is associated with data on the main component and data on the chemical shift component; and
determining final data for image restoration based on a result of the comparison.

### Claim 2 (depends on 1)

The method according to claim 1, wherein the geometric error is determined in proportion to the resonant frequency difference between the main component and the chemical shift component in the subject.

### Claim 3 (depends on 2)

The method according to claim 2, wherein the geometric error is further determined using a gyromagnetic ratio and a size of a gradient magnetic field applied to the subject.

### Claim 4 (depends on 1)

The method according to claim 1, wherein the phase error of the chemical shift component is determined in proportion to the geometric error, a size of a blip of a gradient magnetic field, and a time at which the blip of the gradient magnetic field is applied to the subject.

### Claim 5 (depends on 1)

The method according to claim 1, wherein the comparing includes:
calculating the data in which the phase error of the chemical shift component is reflected by the phase error of the chemical shift component being reflected in Fourier transform data of the data on the main component and the data on the chemical shift component;
calculating a difference between the data in which the phase error of the chemical shift component is reflected and the k-space data; and
wherein the determining includes determining the final data on based on a result of the calculation of the difference.

### Claim 6 (depends on 5)

The method according to claim 5, wherein the calculating of the data in which the phase error of the chemical shift component is reflected includes:
calculating the data in which the phase error of the chemical shift component is reflected using at least one from among a gradient magnetic field phase reflection operator for reinforcing a phase due to a gradient magnetic field when the blipped-CAIPI is performed, a chemical shift phase reflection operator for reinforcing a phase error caused by chemical shift, and a coil sensitivity reflector for coil sensitivity being reflected in the data, which is further reflected in the Fourier transform data by the MRI apparatus.

### Claim 7 (depends on 6)

The method according to claim 6, wherein the determining includes determining the final data in which an amount of change of the data on the main component and the data on the chemical shift component are further reflected.

### Claim 8 (depends on 1)

The method according to claim 1, wherein the comparing is calculated as follows,
ρ
=
arg
⁢
⁢
min
ρ
⁢

s
-
ΘΦΨ
⁢
⁢
FC
⁢
⁢
ρ

2
2
+
λ
⁢

∇
ρ

1
wherein, ρ represents target data, s represents the obtained k-space data, Θ represents a phase error operator for applying the phase error of the chemical shift component, ϕ represents a gradient magnetic field phase reflection operator, ψ represents a chemical shift phase reflection operator, F represents a Fourier transform operator for performing a Fourier transform on each of the main component and the chemical shift component, C represents a generalized coil sensitivity reflector, ρ represents the data on the main component and the data on the chemical shift component, λ represents a normalization coefficient, and ∇ is a gradient operator.

### Claim 9 (depends on 8)

The method according to claim 8, wherein Θ is defined as follows,
Θ=exp(−jα)
wherein j represents a predefined constant and α represents the phase error of the chemical shift component.

### Claim 10 (depends on 9)

The method according to claim 9, wherein the phase error (α) is calculated as follows:
α
=
2
⁢
⁢
π
⁢
⁢
γ
⁢
⁢
G
b
⁢
T
b
⁢
z
f
and
z
f
=
f
f
γ
⁢
⁢
G
ss
wherein, γ represents a gyromagnetic ratio, Gb represents a size of a blip of a gradient magnetic field, Tb represents a gradient magnetic field application time, zf represents the geometric error, ff represents a resonant frequency difference between the main component and the chemical shift component, and Gss represents a size of the gradient magnetic field.

### Claim 11

An MRI apparatus comprising:
a static magnetic field generator configured to apply a static magnetic field to a subject;
a gradient magnetic field generator configured to apply a gradient magnetic field to the subject the gradient magnetic field generator including a slice-select gradient magnetic field application part, a frequency-encoding gradient magnetic field application part, and a phase-encoding gradient magnetic field application part;
a radio frequency (RF) coil configured to apply an RF pulse to the subject and receive a signal generated by the subject; and
a processor configured to obtain k-space data on the subject,
wherein the slice-select gradient magnetic field application part is configured to further apply a slice-select gradient magnetic field to the subject and perform blipped-CAIPI,
wherein the processor is further configured to determine a phase error of a chemical shift component, compare the k-space data to data in which the phase error of the chemical shift component is reflected, wherein the data in which the phase error of the chemical shift component is reflected is associated with data on a main component and data on a chemical shift component, and determine final data for image restoration based on a result of the comparison, and
wherein the phase error of the chemical shift component is proportional to a geometric error based on a resonant frequency difference between the main component and chemical shift component in the subject.

### Claim 12 (depends on 11)

The MRI apparatus according to claim 11, wherein the geometric error is determined in proportion to the resonant frequency difference between the main component and the chemical shift component in the subject.

### Claim 13 (depends on 12)

The MRI apparatus according to claim 12, wherein the geometric error is further determined using a gyromagnetic ratio and a size of a gradient magnetic field applied to the subject.

### Claim 14 (depends on 11)

The MRI apparatus according to claim 11, wherein the phase error of the chemical shift component is determined in proportion to the geometric error, a size of a blip of the gradient magnetic field, and a time at which the blip of the gradient magnetic field is applied.

### Claim 15 (depends on 11)

The MRI apparatus according to claim 11, wherein the processor is further configured to calculate the data in which the phase error of the chemical shift component is reflected by the phase error of the chemical shift component being reflected in Fourier transform data of the data on the main component and the data on the chemical shift component, to calculate a difference between the data in which the phase error of the chemical shift component is reflected and the k-space data, and to determine final data based on a result of the calculation of the difference.

### Claim 16 (depends on 15)

The MRI apparatus according to claim 15, wherein the processor is further configured to calculate the data in which the phase error of the chemical shift component is reflected using at least one from among a gradient magnetic field phase reflection operator for reinforcing a phase due to the gradient magnetic field when the blipped-CAIPI is performed, a chemical shift phase reflection operator for reinforcing a phase error caused by chemical shift, and a coil sensitivity reflector for coil sensitivity being reflected in the data, which is further reflected in the Fourier transform data by the MRI apparatus.

### Claim 17 (depends on 16)

The MRI apparatus according to claim 16, wherein the processor is further configured to determine the final data in which an amount of change of the data on the main component and the data on the chemical shift component are further reflected.

### Claim 18 (depends on 11)

The MRI apparatus according to claim 11, wherein the phase error (α) is calculated as follows:
α
=
2
⁢
⁢
π
⁢
⁢
γ
⁢
⁢
G
b
⁢
T
b
⁢
z
f
and
z
f
=
f
f
γ
⁢
⁢
G
ss
wherein, γ represents a gyromagnetic ratio, Gb represents a size of a blip of a gradient magnetic field, Tb represents a gradient magnetic field application time, zf represents the geometric error, ff represents the resonant frequency difference between the main component and the chemical shift component, and Gss represents a size of the gradient magnetic field.