Method and apparatus for correcting uniformity of a magnetic resonance image
The present invention provides a method and apparatus for correcting a uniformity of a magnetic resonance image, the method including: acquiring a first uniformity enhancement image by a phased-array uniformity enhancement method; and dividing the first uniformity enhancement image by a receiving sensitivity distribution value of a body coil in a magnetic resonance imaging device, so as to acquire a second uniformity enhancement image. The method further includes: dividing the second uniformity enhancement image by a spatial signal distribution value resulting from a field strength distribution of a transmitting radio-frequency field, so as to acquire a third uniformity enhancement image.
1. A method for correcting a uniformity of a magnetic resonance image, comprising:
acquiring a first uniformity enhancement image by a phased-array uniformity enhancement method comprising:
receiving a body coil image and a surface coil image;
receiving an original image; and
performing correction of the original image according to the body coil image and the surface coil image to derive the first uniformity enhancement image; and
dividing the first uniformity enhancement image by a receiving sensitivity distribution value of a body coil in a magnetic resonance imaging device, so as to acquire a second uniformity enhancement image.
2. The method for correcting a uniformity of a magnetic resonance image according to claim 1 , further comprising:
dividing the second uniformity enhancement image by a spatial signal distribution value resulting from a field strength distribution of a transmitting radio frequency (RF) field, so as to acquire a third uniformity enhancement image.
3. The method for correcting a uniformity of a magnetic resonance image according to claim 1 , before the step of acquiring the first uniformity enhancement image, further comprising:
utilizing prior knowledge to acquire the receiving sensitivity distribution value of the body coil.
4. The method for correcting a uniformity of a magnetic resonance image according to claim 3 , wherein the prior knowledge comprises a receiving sensitivity distribution value of the body coil acquired by performing simulation on the body coil.
5. The method for correcting a uniformity of a magnetic resonance image according to claim 2 , before the step of acquiring the third uniformity enhancement image, further comprising:
acquiring the spatial signal distribution value resulting from the field strength distribution of the transmitting RF field according to a Bloch equation.
6. The method for correcting a uniformity of a magnetic resonance image according to claim 5 , wherein the Bloch equation is described as:
d
M
→
dt
=
γ
M
→
×
B
→
ext
+
1
T
1
(
M
0
-
M
z
)
z
^
-
1
T
2
M
→
⊥
,
wherein {right arrow over (B)} ext represents the field strength distribution of the transmitting RF field;
{right arrow over (M)} represents a magnetization vector of a proton in a specific sample, which comprises M z and {right arrow over (M)} ⊥ , M 0 represents a magnetization vector when proton spins to a balanced state;
M z represents a vertical magnetization vector;
{right arrow over (M)} ⊥ is a horizontal magnetization vector;
{circumflex over (z)} denotes a vertical direction;
γ denotes a gyromagnetic ratio, which is a constant;
T1 is a vertical relaxation time of the specific sample, and T2 is a horizontal relaxation time of the specific sample, wherein M 0 , {right arrow over (B)} ext , T1 and T2 are predicted values, and {right arrow over (M)} is a measured value; and
a steady-state solution of the magnetization vector {right arrow over (M)} in a rotating coordinate system is obtained by solving the Bloch equation, so as to obtain the spatial signal distribution value resulting from the transmitting RF field.
7. The method for correcting a uniformity of a magnetic resonance image according to claim 6 , before the step of acquiring the spatial signal distribution value resulting from the field strength distribution of the transmitting RF field, further comprising:
utilizing prior knowledge to acquire the field strength distribution of the transmitting RF field of the body coil.
8. The method for correcting a uniformity of a magnetic resonance image according to claim 7 , wherein the prior knowledge comprises: a field strength distribution of the transmitting RF field acquired by performing simulation on the body coil.
9. An apparatus for correcting a uniformity of a magnetic resonance image, comprising:
a first uniformity enhancement module for acquiring a first uniformity enhancement image, wherein to acquire the first uniformity enhancement image, the first uniformity enhancement module is configured to:
receiving a body coil image and a surface coil image;
receiving an original image; and
perform correction of the original image according to the body coil image and the surface coil image to derive the first uniformity enhancement image; and
a second uniformity enhancement module for dividing the first uniformity enhancement image by a receiving sensitivity distribution value of a body coil in a magnetic resonance imaging device, so as to acquire a second uniformity enhancement image.
10. The apparatus for correcting a uniformity of a magnetic resonance image according to claim 9 , further comprising a third uniformity enhancement module for dividing the second uniformity enhancement image by a spatial signal distribution value resulting from a field strength distribution of a transmitting radio-frequency (RF) field, so as to acquire a third uniformity enhancement image.
11. The apparatus for correcting a uniformity of a magnetic resonance image according to claim 9 , further comprising a first simulation module for performing simulation on the body coil to acquire a receiving sensitivity distribution value of the body coil.
12. The apparatus for correcting a uniformity of a magnetic resonance image according to claim 9 , further comprising a spatial signal distribution value acquisition module for acquiring the spatial signal distribution value resulting from the field strength distribution of the transmitting RF field according to a Bloch equation.
13. The apparatus for correcting a uniformity of a magnetic resonance image according to claim 12 , wherein the Bloch equation is described as:
d
M
→
dt
=
γ
M
→
×
B
→
ext
+
1
T
1
(
M
0
-
M
z
)
z
^
-
1
T
2
M
→
⊥
,
wherein {right arrow over (B)} ext represents the field strength distribution of the transmitting RF field; {right arrow over (M)} represents a magnetization vector of a proton in a specific sample, which comprises M z and {right arrow over (M)} ⊥ , M 0 represents a magnetization vector when proton spins to a balanced state;
M z represents a vertical magnetization vector;
{right arrow over (M)} ⊥ is a horizontal magnetization vector; {circumflex over (z)} denotes a vertical direction;
γ denotes a gyromagnetic ratio, which is a constant;
T1 is a vertical relaxation time of the specific sample, and T2 is a horizontal relaxation time of the specific sample, wherein M 0 , {right arrow over (B)} ext , T1 and T2 are predicted values, and {right arrow over (M)} is a measured value; and
a steady-state solution of the magnetization vector {right arrow over (M)} in a rotating coordinate system is obtained by solving the Bloch equation, so as to obtain the spatial signal distribution value resulting from the transmitting RF field.
14. The apparatus for correcting a uniformity of a magnetic resonance image according to claim 13 , further comprising a second simulation module for performing simulation on the body coil to acquire the field strength distribution of the transmitting RF field of the body coil.