Method and system for non-invasive assessment of coronary artery disease
In order to assess coronary artery disease from medical image data, an anatomical model of a coronary artery is generated from the medical image data. A velocity of blood in the coronary artery is estimated based on a spatio-temporal representation of contrast agent propagation in the medical image data. Blood flow is simulated in the anatomical model of the coronary artery using a computational fluid dynamics (CFD) simulation using the estimated velocity of the blood in the coronary artery as a boundary condition.
1. A method of non-invasive assessment
coronary flow reserve (CFR) using medical image data, comprising:
receiving a first sequence of medical image data acquired during a resting state using a computed tomography (CT) scanner or an X-ray image acquisition device and a second sequence of medical image data acquired during hyperemia using a computed tomography (CT) scanner or an X-ray image acquisition device;
generating a first anatomical model of a coronary artery from the first sequence of medical image data and a second anatomical model of the coronary artery from the second sequence of medical image data;
estimating a maximum velocity of blood on a cross-section of the coronary artery during the resting state based on a spatio-temporal representation of contrast agent propagation over a length of the coronary artery in the first sequence of medical image data and estimating a maximum velocity of blood on the cross-section of the coronary artery during hyperemia based on a spatio-temporal representation of contrast agent propagation over the length of the coronary artery in the second sequence of medical image data;
mapping the maximum velocity of the blood on the cross-section of the coronary artery during the resting state to an average rest velocity representing a spatial average of a velocity profile over the cross-section of the coronary artery during the resting state using patient-specific mapping parameters, and mapping the maximum velocity of the blood on the cross-section of the coronary artery during hyperemia to an average hyperemia velocity representing a spatial average of a velocity profile over the cross-section of the coronary artery during hyperemia using patient-specific mapping parameters; and
calculating the coronary flow reserve for the coronary artery based on the average rest velocity and the average hyperemia velocity.
2. The method of claim 1 , wherein the step of estimating a maximum velocity of blood on a cross-section of the coronary artery during the resting state based on a spatio-temporal representation of contrast agent propagation over a length of the coronary artery in the first sequence of medical image data and estimating a maximum velocity of blood on the cross-section of the coronary artery during hyperemia based on a spatio-temporal representation of contrast agent propagation over the length of the coronary artery in the second sequence of medical image data comprises, for each of the first and second sequences of medical image data:
generating the spatio-temporal representation of contrast agent propagation based on time-intensity curves extracted from the respective sequence of medical image data; and
estimating a slope of the spatio-temporal representation of contrast agent propagation.
3. The method of claim 2 , wherein the step of generating the spatio-temporal representation of contrast agent propagation based on time-intensity curves extracted from the respective sequence of medical image data comprises:
mapping an inverted intensity magnitude of points in the respective sequence of medical image data over the length of the coronary artery over time.
4. The method of claim 1 , wherein the step of mapping the maximum velocity of the blood on the cross-section of the coronary artery during the resting state to an average rest velocity representing a spatial average of a velocity profile over the cross-section of the coronary artery during the resting state using patient-specific mapping parameters, and mapping the maximum velocity of the blood on the cross-section of the coronary artery during hyperemia to an average hyperemia velocity representing a spatial average of a velocity profile over the cross-section of the coronary artery during hyperemia using the patient-specific mapping parameters comprises:
mapping the maximum velocity during the resting state to the average rest velocity and the maximum velocity during hyperemia to the average hyperemia velocity based on a Womersley number based procedure and the patient-specific mapping parameters.
5. The method of claim 1 , wherein the step of mapping the velocity of the blood on the cross-section of the coronary artery during the resting state to an average rest velocity representing a spatial average of a velocity profile over the cross-section of the coronary artery during the resting state using patient-specific mapping parameters, and mapping the maximum velocity of the blood on the cross-section of the coronary artery during hyperemia to an average hyperemia velocity representing a spatial average of a velocity profile over the cross-section of the coronary artery during hyperemia using patient-specific mapping parameters comprises, for each of the maximum velocity during the resting state and the maximum velocity during hyperemia:
mapping a maximum velocity to an average velocity as
V
avg
=
V
max
(
1
+
p
W
q
)
2
,
where V max is the maximum velocity, V avg is the average velocity, W is the Womersley number, defined as
W
=
R
f
ρ
μ
,
where f is a frequency of a pulsatile flow, R is a cross-sectional area of the coronary artery, ρ is the density of blood, and μ the dynamic viscosity of blood, and p and q are the patient-specific mapping parameters determined using a series of computational fluid dynamics (CFD) simulations.
6. The method of claim 5 , wherein the step of mapping a maximum velocity to an average velocity further comprises:
performing a series of computational fluid dynamics (CFD) simulations on the respective anatomical model of the coronary artery having various prescribed flow values and varying values for at least one of W, f, R, ρ, or μ, resulting in various simulated values for the maximum velocity and the average velocity; and
determining values for the patient-specific mapping parameters p and q by fitting the mapping parameters to the simulated values for the maximum velocity and the average velocity.
7. The method of claim 1 , wherein the step of calculating the coronary flow reserve for the coronary artery based on the average rest velocity and the average hyperemia velocity comprises:
calculating the coronary flow reserve (CFR) as
CFR
=
ρ
A
hyp
V
hyp
ρ
A
rest
V
rest
,
where V hyp is the average hyperemia velocity, V rest is the average rest velocity, p is the density of blood, A hyp is the cross-sectional area of the second anatomical model, and A rest is the cross-sectional area of the first anatomical model.
8. An apparatus for non-invasive assessment coronary flow reserve (CFR) using medical image data, comprising:
a processor; and
a memory storing computer program instructions, which when executed by the processor cause the processor to perform operations comprising:
receiving a first sequence of medical image data acquired during a resting state using a computed tomography (CT) scanner or an X-ray image acquisition device and a second sequence of medical image data acquired during hyperemia using a computed tomography (CT) scanner or an X-ray image acquisition device;
generating a first anatomical model of a coronary artery from the first sequence of medical image data and a second anatomical model of the coronary artery from the second sequence of medical image data;
estimating a maximum velocity of blood on a cross-section of the coronary artery during the resting state based on a spatio-temporal representation of contrast agent propagation over a length of the coronary artery in the first sequence of medical image data and estimating a maximum velocity of blood on the cross-section of the coronary artery during hyperemia based on a spatio-temporal representation of contrast agent propagation over the length of the coronary artery in the second sequence of medical image data;
mapping the maximum velocity of the blood on the cross-section of the coronary artery during the resting state to an average rest velocity representing a spatial average of a velocity profile over the cross-section of the coronary artery during the resting state using patient-specific mapping parameters and mapping the maximum velocity of the blood on the cross-section of the coronary artery during hyperemia to an average hyperemia velocity representing a spatial average of a velocity profile over the cross-section of the coronary artery during hyperemia using patient-specific mapping parameters; and
calculating the coronary flow reserve for the coronary artery based on the average rest velocity and the average hyperemia velocity.
9. The apparatus of claim 8 , wherein estimating a maximum velocity of blood on a cross-section of the coronary artery during the resting state based on a spatio-temporal representation of contrast agent propagation over a length of the coronary artery in the first sequence of medical image data and estimating a maximum velocity of blood on the cross-section of the coronary artery during hyperemia based on a spatio-temporal representation of contrast agent propagation over the length of the coronary artery in the second sequence of medical image data comprises:
generating a spatio-temporal representation of contrast agent propagation based on time-intensity curves extracted from a sequence of medical image data; and
estimating a slope of the spatio-temporal representation of contrast agent propagation.
10. The apparatus of claim 9 , wherein generating the spatio-temporal representation of contrast agent propagation based on time-intensity curves extracted from a sequence of medical image data comprises:
mapping an inverted intensity magnitude of points in the respective sequence of medical image data over the length of the coronary artery over time.
11. The apparatus of claim 8 , wherein mapping the velocity of the blood on the cross-section of the coronary artery during the resting state to an average rest velocity representing a spatial average of a velocity profile over the cross-section of the coronary artery during the resting state using patient-specific mapping parameters and mapping the maximum velocity of the blood on the cross-section of the coronary artery during hyperemia to an average hyperemia velocity representing a spatial average of a velocity profile over the cross-section of the coronary artery during hyperemia using patient-specific mapping parameters comprises:
mapping a maximum velocity to an average velocity as
V
avg
=
V
max
(
1
+
p
W
q
)
2
,
where V max is the maximum velocity, V avg is the average velocity, W is the Womersley number, defined as
W
=
R
f
ρ
μ
,
where f is a frequency of a pulsatile flow, R is a cross-sectional area of the coronary artery, ρ is the density of blood, and μ the dynamic viscosity of blood, and p and q are the patient-specific mapping parameters determined using a series of computational fluid dynamics (CFD) simulations.
12. The apparatus of claim 11 , wherein mapping a maximum velocity to an average velocity further comprises:
performing a series of computational fluid dynamics (CFD) simulations on the respective anatomical model of the coronary artery having various prescribed flow values and varying values for at least one of W, f, R, ρ, and/or μ, resulting in various simulated values for the maximum velocity and the average velocity; and
determining values for the patient-specific mapping parameters p and q by fitting the mapping parameters to the simulated values for the maximum velocity and the average velocity.
13. The apparatus of claim 8 , wherein calculating the coronary flow reserve for the coronary artery based on the average rest velocity and the average hyperemia velocity comprises:
means for calculating the coronary flow reserve (CFR) as
CFR
=
ρ
A
hyp
V
hyp
ρ
A
rest
V
rest
,
where v hyp is the average hyperemia velocity, v rest is the average rest velocity, p is the density of blood, A hyp is the cross-sectional area of the second anatomical model, and A rest is the cross-sectional area of the first anatomical model.
14. A non-transitory computer readable medium comprising computer executable instructions for performing non-invasive assessment coronary flow reserve (CFR) using medical image data, the computer executable instructions performing steps comprising:
receiving a first sequence of medical image data acquired during a resting state using a computed tomography (CT) scanner or an X-ray image acquisition device and a second sequence of medical image data acquired during hyperemia using a computed tomography (CT) scanner or an X-ray image acquisition device;
generating a first anatomical model of a coronary artery from the first sequence of medical image data and a second anatomical model of the coronary artery from the second sequence of medical image data;
estimating a maximum velocity of blood on a cross-section of the coronary artery during the resting state based on a spatio-temporal representation of contrast agent propagation over a length of the coronary artery in the first sequence of medical image data and estimating a maximum velocity of blood on the cross-section of the coronary artery during hyperemia based on a spatio-temporal representation of contrast agent propagation over the length of the coronary artery in the second sequence of medical image data;
mapping the maximum velocity of the blood on the cross-section of the coronary artery during the resting state to an average rest velocity representing a spatial average of a velocity profile over the cross-section of the coronary artery during the resting state using patient-specific mapping parameters, and mapping the maximum velocity of the blood on the cross-section of the coronary artery during hyperemia to an average hyperemia velocity representing a spatial average of a velocity profile over the cross-section of the coronary artery during hyperemia using patient-specific mapping parameters; and
calculating the coronary flow reserve for the coronary artery based on the average rest velocity and the average hyperemia velocity.
15. The non-transitory computer readable medium of claim 14 , wherein the computer executable instructions defining the step of estimating a maximum velocity of blood on a cross-section of the coronary artery during the resting state based on a spatio-temporal representation of contrast agent propagation over a length of the coronary artery in the first sequence of medical image data and estimating a maximum velocity of blood on the cross-section of the coronary artery during hyperemia based on a spatio-temporal representation of contrast agent propagation over the length of the coronary artery in the second sequence of medical image data comprise computer executable instructions defining, for each of the first and second sequences of medical image data, the steps of:
generating the spatio-temporal representation of contrast agent propagation based on time-intensity curves extracted from the respective sequence of medical image data; and
estimating a slope of the spatio-temporal representation of contrast agent propagation.
16. The non-transitory computer readable medium of claim 15 , wherein the computer executable instructions defining the step of generating the spatio-temporal representation of contrast agent propagation based on time-intensity curves extracted from the respective sequence of medical image data comprise computer executable instructions defining the step of:
mapping an inverted intensity magnitude of points in the respective sequence of medical image data over the length of the coronary artery over time.
17. The non-transitory computer readable medium of claim 14 , wherein the computer executable instructions defining the step of mapping the velocity of the blood on the cross-section of the coronary artery during the resting state to an average rest velocity representing a spatial average of a velocity profile over the cross-section of the coronary artery during the resting state using patient-specific mapping parameters, and mapping the maximum velocity of the blood on the cross-section of the coronary artery during hyperemia to an average hyperemia velocity representing a spatial average of a velocity profile over the cross-section of the coronary artery during hyperemia using patient-specific mapping parameters comprise computer executable instructions defining, for each of the maximum velocity at rest and the maximum velocity at hyperemia, the step of:
mapping a maximum velocity to an average velocity as
V
avg
=
V
max
(
1
+
p
W
q
)
2
,
where V max is the maximum velocity, V avg is the average velocity, W is the Womersley number, defined as
W
=
R
f
ρ
μ
,
where f is a frequency of a pulsatile flow, R is a cross-sectional area of the coronary artery, ρ is the density of blood, and μ the dynamic viscosity of blood, and p and q are the patient-specific mapping parameters determined using a series of computational fluid dynamics (CFD) simulations.
18. The non-transitory computer readable medium of claim 17 , wherein the computer executable instructions defining the step of mapping a maximum velocity to an average velocity further comprise computer executable instructions defining the steps of:
performing a series of computational fluid dynamics (CFD) simulations on the respective anatomical model of the coronary artery having various prescribed flow values and varying values for at least one of W, f, R, ρ, and/or μ, resulting in various simulated values for the maximum velocity and the average velocity; and
determining values for the patient-specific mapping parameters p and q by fitting the mapping parameters to the simulated values for the maximum velocity and the average velocity.
19. The non-transitory computer readable medium of claim 14 , wherein the computer executable instructions defining the step of calculating the coronary flow reserve for the coronary artery based on the average rest velocity and the average hyperemia velocity comprise computer executable instructions defining the step of:
calculating the coronary flow reserve (CFR) as
CFR
=
ρ
A
hyp
V
hyp
ρ
A
rest
V
rest
,
where V hyp is the average hyperemia velocity, V rest is the average rest velocity, p is the density of blood, A hyp is the cross-sectional area of the second anatomical model, and A rest is the cross-sectional area of the first anatomical model.