Magnetic resonance imaging method
Provided is a method for compensating for tissue motion during magnetic resonance (MR) imaging, and an apparatus for use thereof. The method includes acquiring a plurality of short-time MR scan images; selecting a reference scan image from the acquired plurality of short-time MR scan images; defining a set of transformation images based on the acquired plurality of short-time MR scan images other than the selected reference scan image; registering the reference scan image and the defined set of transformation images; calculating an average of aligned, registered images of the defined set of transformation images; and generating a motion-corrected image based on the calculated average.
1. A method for compensating for tissue motion during magnetic resonance (MR) imaging, the method comprising:
acquiring a plurality of short-time MR scan images;
selecting a reference scan image from the acquired plurality of short-time MR scan images;
defining a set of transformation images based on the acquired plurality of short-time MR scan images other than the selected reference scan image;
registering the reference scan image and the defined set of transformation images;
calculating an average of aligned, registered images of the defined set of transformation images; and
generating a motion-corrected image based on the calculated average.
2. The method according to claim 1 , wherein registering the reference scan image and the set of defined transformation images includes aligning points in each image of the acquired plurality of short-time MR scan images in the defined set of transformation images to points in the reference scan image.
3. The method according to claim 2 , wherein registering the reference scan image and the set of defined transformation images includes determining a global transformation representing an overall motion of the defined set of transformation images and a local transformation representing a local deformation of the defined set of transformation images.
4. The method according to claim 3 , wherein the global transformation is a twelve parameter affine transformation.
5. The method according to claim 3 , wherein the local transformation is a free form transformation based on B-splines.
6. The method according to claim 5 , wherein the B-splines are one of linear B-splines and cubic B-splines.
7. The method according to claim 1 , wherein registering the reference scan image and the defined set of transformation images includes performing a cost function analysis of the calculated average based on a negative of α-information between the reference scan image and the defined set of transformation images using Equation:
C
(
μ
,
α
)
=
-
1
α
(
α
-
1
)
(
∑
l
,
k
p
(
α
)
(
l
,
k
|
μ
)
p
M
(
l
|
μ
)
p
R
(
k
)
α
-
1
-
1
)
.
8. The method according to claim 7 , further including optimizing the cost function analysis using Equation:
∂
C
∂
μ
i
=
-
1
α
(
α
-
1
)
∑
l
,
k
α
p
α
-
1
(
l
,
k
❘
μ
)
∂
p
(
l
,
k
❘
μ
)
∂
μ
i
-
(
α
-
1
)
p
α
(
l
,
k
❘
μ
)
p
M
-
1
(
l
❘
μ
)
∑
k
∂
p
(
l
,
k
❘
μ
)
∂
μ
i
[
p
M
(
l
❘
μ
)
p
R
(
k
)
]
α
-
1
.
9. The method according to claim 1 , further including calculating a quality of the registration of the reference scan image and the defined set of transformation images using a Squared Sum of intensity Difference (SSD) of:
SSD
=
1
n
∑
(
F
R
-
T
(
F
M
)
)
2
.
10. The method according to claim 9 , wherein calculating the quality of the registration of the reference scan image and the defined set of transformation images includes using a Correlation of Coefficients (CC) of:
CC
=
∑
(
F
R
-
F
_
R
)
(
T
(
F
M
)
-
T
(
F
_
M
)
)
∑
(
F
R
-
F
_
R
)
2
∑
(
T
(
F
M
)
-
T
(
F
_
M
)
)
2
.
11. The method according to claim 1 , further including estimating underlying image intensity distributions of the registered reference scan image and the defined set of transformation images using a Parzen window.
12. The method according to claim 1 , wherein a number of the acquired plurality of short-time MR scan images includes six to eight MR scan images.
13. A method for compensating for tissue motion during magnetic resonance (MR) imaging, the method comprising:
acquiring a plurality of short-time MR scan images;
selecting a reference scan image from the acquired plurality of short-time MR scan images;
defining, using a first registration process, a first set of transformation images based on the acquired plurality of short-time MR scan images other than the selected reference scan image;
defining, using a second registration process, a second set of transformation images based on the acquired plurality of short-time MR scan images other than the selected reference scan image;
registering the reference scan image and the defined first and second sets of transformation images using the first registration process and the second registration process;
calculating an average of aligned, registered images of the defined first and second sets of transformation images;
generating first and second motion-corrected images based on the calculated average; and
comparing the first and second motion-corrected images.
14. The method according to claim 13 , wherein the first registration process is an α-information registration process.
15. The method according to claim 13 , wherein the second registration process is a mutual-information registration process.