Non-contrast magnetic resonance perfusion imaging
View Patent ↗A magnetic resonance imaging (MRI) system acquires MRI data within one patient breath-hold sufficient to generate (a) at least one tag-off first type non-contrast cardiac perfusion image using a data acquisition sub-sequence including a non-selective IR (inversion recovery) pulse and (b) at least one tag-on second type non-contrast cardiac perfusion image using a data acquisition sub-sequence including a non-selective IR pulse and a spatially selective IR pulse. A set of registered tag-on and tag-off images are differentially combined to produce an accurate cardiac perfusion image.
1. A magnetic resonance imaging (MRI) system comprising:
an MRI gantry including a static magnet, gradient magnet coils and at least one radio frequency (RF) coil defining a patient imaging volume into which a chest region of a patient is located; and
RF receiver and transmitter circuits coupled to said at least one RF coil;
control circuits connected to said gantry and to said RF receiver and transmitter circuits, said control circuits having an operator display and an operator control input port for configuring and operating said MRI system to acquire and process MRI data from said patient,
said control circuits being configured
(i) to acquire first, second and third MRI data sets for a same region within the chest region without use of a contrast-enhancing chemical agent by performing the following three data acquisition sub-sequences within one scan sequence, (A) using a non-selective inversion pulse without a selective inversion pulse, (B) using a non-selective inversion pulse and a selective inversion pulse, and (C) using a selective inversion pulse without a non-selective inversion pulse;
(ii) to repeat the acquisition of said first, second and third MRI data sets for each of plural different black blood time to inversion (BBTI) values, wherein three data acquisition sub-sequences are performed respectively for a same BBTI value;
(iii) image processing circuits configured to generate first, second and third images for the same region for each of plural different BBTI values based on the first, second and third MRI data sets and to generate a processed cardiac perfusion image by differentially combining respectively corresponding pixels of the first, second and third images; and
(iv) an output circuit for outputting said processed cardiac perfusion image for digital storage or digital data transmission.
2. A magnetic resonance imaging (MRI) system comprising:
an MRI gantry including a static magnet, gradient magnet coils and at least one radio frequency (RF) coil defining a patient imaging volume into which the chest region of a patient is located; and
RF receiver and transmitter circuits coupled to said at least one RF coil;
control circuits connected to said gantry and to said RF receiver and transmitter circuits, said control circuits having an operator display and an operator control input port for configuring and operating said MRI system to acquire and process MRI data from said patient,
said control circuits being configured
(i) to acquire MRI data sufficient to generate without use of a contrast-enhancing chemical agent (a) a first type image using a data acquisition sub-sequence including an IR (inversion recovery) pulse and (b) a second type image using a data acquisition sub-sequence including an IR pulse, the first type image being different from the second type image, and
(ii) to repeat the acquisition of said MRI data for each of plural different black blood time to inversion (BBTI) values;
image processing circuits configured to combine respectively corresponding complex-values of the first type image pixels and second type image pixels to produce a resultant cardiac perfusion image I in accordance with the following formula
I i =(θ o −min(θ o ,|A i −B i |)) F (max(| A i |,|B i |), T BBTI )
where:
A i and B i are complex number values of a pixel at pixel location I of a first type image and a second type image, respectively,
θ o is a threshold value, and
F is a continuous threshold function of |A i | and |B i | and T BBTI black blood time to inversion (BBTI),
wherein:
said control circuits are further configured to acquire MRI data within one patient breath-hold sufficient to generate without use of a contrast-enhancing chemical agent (c) at least one tag-on third type cardiac perfusion image using a data acquisition sub-sequence including a spatially selective IR pulse, and
said image processing circuits are further configured to combine respectively corresponding complex-values of the first type image pixels and third type image pixels to produce a resultant cardiac perfusion image I in accordance with the following formula
I i =|A i −B i |F (| C i −A i |,T BBI )
where A i , B i and C i are complex number values of a pixel at pixel location i of a first type image, a second type image and a third type image, respectively, and T BBTI is the black blood time to inversion (BBTI).
3. An MRI system as in claim 2 , wherein said image processing circuits are configured to define the function F as a sigmoid function.
4. A magnetic resonance imaging (MRI) system, comprising:
an MRI gantry including a static magnet, gradient magnet coils and at least one radio frequency (RF) coil defining a patient imaging volume into which the chest region of a patient is located;
RF receiver and transmitter circuits coupled to said at least one RF coil;
control circuits connected to said gantry and to said RF receiver and transmitter circuits, said control circuits having an operator display and an operator control input port for configuring and operating said MRI system to acquire and process MRI data from said patient,
said control circuits being configured to acquire MRI data within one patient breath-hold sufficient to generate without use of a contrast-enhancing chemical agent (a) at least one tag-off first type cardiac perfusion image using a data acquisition sub-sequence including a non-selective IR (inversion recovery) pulse and (b) at least one tag-on second type cardiac perfusion image using a data acquisition sub-sequence including a non-selective IR pulse and a spatially selective IR pulse, and
image processing circuits configured to generate processed cardiac perfusion image pixels by differentially combining respectively corresponding pixels of tag-on and tag-off images acquired for each BBTI value;
wherein said image processing circuits are configured to combine respectively corresponding complex-values of the first type and second type image pixels to produce a resultant cardiac perfusion image I in accordance with the following formula
I i =(θ o −min(θ o ,|A i −B i |)) F (max(| A i |,|B i |), T BBTI )
where:
A i and B i are complex number values of a pixel at pixel location i of a first type image and a second type image, respectively,
θ o is a threshold value, and
F is a continuous threshold function of |A i | and |B i | and T BBTI black blood time to inversion (BBTI);
wherein said image processing circuits are configured to define the function F as a sigmoid function, and
wherein said sigmoid function F is defined as:
F
(
x
,
t
)
=
(
1
1
+
exp
(
-
x
-
g
(
t
)
6
g
(
t
)
)
)
where x represents pixel value and is a function that represents threshold changes depending on BBTI.
5. An MRI system as in claim 4 , wherein g(t) is based at least in part on T 1 recovery time.
6. An MRI system as in claim 5 , wherein:
g
(
t
)
=
C
max
(
ɛ
,
|
1
-
2
exp
(
-
t
T
1
)
|
)
where C and ε are user-adjustable parameters and T 1 is the T 1 recovery constant of myocardium.
7. An MRI system as in claim 1 , wherein tag-on and tag-off MRI data acquisition sub-sequences are interleaved with respect to time within an overall MRI data acquisition sequence within one patient breath-hold.
8. An MRI system as in claim 1 , wherein said sub-sequences are 3D MRI data acquisition sequences encompassing a multi-slice patient volume.
9. An MRI system as in claim 1 , wherein said sub-sequences comprise a plurality of 2D MRI data acquisition sequences encompassing a multi-slice patient volume.
10. An MRI system as in claim 1 , further comprising:
image processing circuits configured to differentially combine respectively corresponding complex-values of the first and second images to produce a resultant image I which is then further combined by color-blending on a pixel by pixel basis with said first image, said resultant image I and said first image having pixels of different color values.
11. An MRI system as in claim 10 , wherein said resultant image I is assigned color-valued pixel values while said first image is assigned monochrome pixel values.
12. An MRI system as in claim 1 , wherein said MRI data acquisition sub-sequences are multi-slice data acquisitions using a range of black blood time to inversion (BBTI) values to generate a data set which images cardiac perfusion as a function of time that can be viewed in cine fashion or otherwise analyzed for perfusion dynamics, with BBTI as a time-dimension variable.
13. An MRI system as in claim 12 , wherein the range of BBTI values is sufficient to plot or otherwise calculate a mean transit time for blood entering the coronary arteries until it later is dissipated in the myocardium.
14. An MRI system as in claim 1 , wherein said MRI data acquisition sub-sequences are multi-slice data acquisitions using a range of black blood time to inversion (BBTI) values to generate a data set which images cardiac perfusion as a function of time, said MRI system further comprising:
image processing circuits configured to perform a pixel minimum value selection between a threshold value and actual pixel value of all acquired images over a range of BBTI values to produce a composite image isolating possible ischemic and/or infarct regions of cardiac myocardium as areas of distinguishable contrast where acquired MRI signals did not change significantly between the first and second images over many BBTI values.
15. A magnetic resonance imaging (MRI) method comprising:
using an MRI gantry including a static magnet, gradient magnet coils and at least one radio frequency (RF) coil defining a patient imaging volume into which the chest region of a patient is located, RF receiver and transmitter circuits coupled to said at least one RF coil
(i) to acquire MRI data sufficient to generate, within one patient breath-hold, without use of a contrast-enhancing chemical agent, (a) a first image using a data acquisition sub-sequence including an IR (inversion recovery) pulse, (b) a second image using a data acquisition sub-sequence including an IR pulse, and (c) a third type image using a data acquisition sub-sequence including a spatially selective IR pulse, the first, second and third type images being different from each other, wherein each of said first, second and third data acquisition sub-sequences is one of the following three types (A) using a non-selective inversion pulse without a selective inversion pulse, (B) using a non-selective inversion pulse and a selective inversion pulse, and (C) using a selective inversion pulse without a non-selective inversion pulse;
(ii) to repeat the acquisition of said MRI data for each of plural different black blood time to inversion (BBTI) values;
(iii) to generate first, second and third images for the same region for each of plural different BBTI values based on the acquired MRI data, and to generate a processed cardiac perfusion image, by differentially combining respectively corresponding pixels of the first, second and third images; and
(iv) to output said processed cardiac perfusion image for digital storage or digital data transmission.
16. An MRI method as in claim 15 , further comprising:
using an image processor to combine respectively corresponding complex-values of the first image pixels and second image pixels to produce a resultant cardiac perfusion image I in accordance with the following formula
I i −min(θ o ,|A i −B i |)) F (max(| A i |,|B i |), T BBTI )
where:
A i and B i are complex number values of a pixel at pixel location i of a first image and a second image, respectively,
θ o is a threshold value, and
F is a continuous threshold function of |A i | and |B i | and T BBTI black blood time to inversion (BBTI).
17. A magnetic resonance imaging (MRI) method using an MRI gantry including a static magnet, gradient magnet coils and at least one radio frequency (RF) coil defining a patient imaging volume into which the chest region of a patient is located, RF receiver and transmitter circuits coupled to said at least one RF coil to acquire MRI data within one patient breath-hold sufficient to generate without use of a contrast-enhancing chemical agent (a) at least one tag-off first type cardiac perfusion image using a data acquisition sub-sequence including a non-selective IR (inversion recovery) pulse and (b) at least one tag-on second type cardiac perfusion image using a data acquisition sub-sequence including a non-selective IR pulse and a spatially selective IR pulse, and
using at least one image processor to generate processed cardiac perfusion image pixels by differentially combining respectively corresponding pixels of tag-on and tag-off images acquired for each BBTI value;
wherein said image processor combines respectively corresponding complex-values of the first type image pixels and second type image pixels to produce a resultant cardiac perfusion image I in accordance with the following formula
I i =(θ o −min(θ o ,|A i −B i |)) F (max(| A i |,|B i |), T BBTI )
where:
A i and B i are complex number values of a pixel at pixel location i of a first type image and a second type image, respectively,
θ o is a threshold value, and
F is a continuous threshold function of |A i | and |B i | and T BBTI black blood time to inversion (BBTI), and
wherein F is defined as:
F
(
x
,
t
)
=
(
1
1
+
exp
(
-
x
-
g
(
t
)
6
g
(
t
)
)
)
where x represents pixel value and g(t) is a function that represents threshold changes depending on BBTI.
18. An MRI method as in claim 17 , wherein:
g
(
t
)
=
C
max
(
ɛ
,
|
1
-
2
exp
(
-
t
T
1
)
|
)
where C and ε are parameters to be adjusted and T 1 is the T 1 recovery constant of myocardium.
19. An MRI system as in claim 1 , wherein:
said MRI data is acquired within one patient breath-hold.
20. An MRI system as in claim 1 , wherein:
the first image is a tag-off image using a data acquisition sub-sequence including a non-selective IR pulse and the second image is a tag-on image using a data acquisition sub-sequence including a non-selective IR pulse and a spatially selective IR pulse.
21. An MRI system as in claim 1 , wherein:
the first, second and third images are perfusion images.
22. An MRI system as in claim 1 , further comprising:
image processing circuits configured to generate processed cardiac perfusion image pixels by differentially combining respectively corresponding pixels of two images acquired for each BBTI value.