Multi-echo length and offset varied saturation (Me-LOVARS) method for chemical exchange saturation transfer (CEST) MR imaging
A novel approach for CEST MR imaging is called Multi-echo Length and Offset VARied Saturation (Me-LOVARS) CEST. This method allows efficient collection of additional CEST data without penalty in scan time, which could be useful for enhancing the contrast, increasing the specificity or improving quantification of exchange. As CEST-MRI has shown promise at both the pre-clinical and clinical levels, including for detecting and grading brain tumors and evaluating ischemia, using either endogenous CEST contrast or through administration of CEST contrast agents. This fast and robust imaging method is suitable for accelerating image collection and widening the scope of applications for CEST-MRI.
1. A method for magnetic resonance imaging of a subject comprising:
generating a magnetization using an magnetic resonance imaging machine;
applying “N” number of iterative modules to achieve multiple readouts;
wherein the “N” number of iterative modules each comprise a saturation preparation component, a readout component, and a flip back component;
processing the multiple readouts into an image of the subject.
2. The method of claim 1 further comprising using N equals approximately 3 to 8 modules.
3. The method of claim 1 further comprising using modules with a length of t sat /N.
4. The method of claim 1 further comprising using modules with a length of approximately 0.3 seconds to 1 second.
5. The method of claim 1 further comprising using the readout component comprising a low flip angle fast gradient echo readout sequence.
6. The method of claim 5 further comprising using a flip angle of α.
7. The method of claim 1 further comprising using a flip back pulse for retaining the magnetization.
8. The method of claim 1 further comprising defining magnetization as longitudinal magnetization:
M
N
z
,
sat
=
x
s
ɛ
k
sw
T
1
,
w
·
M
N
z
·
e
-
T
sat
N
·
T
1
,
w
=
b
·
M
N
z
·
e
-
T
sat
N
·
T
1
,
w
in the absence of saturated protons.
9. The method of claim 8 further comprising defining longitudinal magnetization after the Nth module as
M
N
z
,
-
α
=
M
N
z
,
α
·
cos
α
+
M
N
x
,
α
·
e
-
TE
T
2
*
·
sin
α
=
b
·
M
N
z
·
e
-
T
sat
N
·
T
1
,
w
[
1
-
sin
2
α
(
1
-
e
-
TE
T
2
*
)
]
.
10. The method of claim 1 further comprising defining magnetization as longitudinal and transverse magnetization.
11. The method of claim 1 further comprising defining magnetization as
M N z,α =M N z,sat ·cos α a)
M N x,α =M N z,sat ·sin α b)
when applying the flip angle component.
12. The method of claim 1 further comprising defining an iterative relationship between modules as
M
N
z
,
-
α
=
b
·
M
N
-
1
z
,
-
α
·
e
-
T
sat
N
·
T
1
,
w
[
1
-
sin
2
α
(
1
-
e
-
TE
T
2
*
)
]
=
b
·
M
N
-
2
z
,
-
α
·
e
-
2
T
sat
N
·
T
1
,
w
[
1
-
sin
2
α
(
1
-
e
-
TE
T
2
*
)
]
2
…
…
=
b
·
M
0
z
,
-
α
·
e
-
T
sat
T
1
,
w
[
1
-
sin
2
α
(
1
-
e
-
TE
T
2
*
)
]
N
.
13. The method of claim 1 further comprising using a T 2 decay term.
14. The method of claim 1 further comprising executing the method using a non-transitory computer readable medium.