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Dynamically Scaled Phantom Phase Contrast MRI Compared to True-Scale Computational Modeling of Coronary Artery Flow

Authors:
Susann Beier at UNSW Sydney
Susann Beier
John A Ormiston at Mercy Angiography
John A Ormiston
  • Mercy Angiography
Mark W I Webster at Auckland District Health Board
Mark W I Webster
John Edward Cater at University of Canterbury
John Edward Cater
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Abstract

Purpose: To examine the feasibility of combining computational fluid dynamics (CFD) and dynamically scaled phantom phase-contrast magnetic resonance imaging (PC-MRI) for coronary flow assessment. Materials and methods: Left main coronary bifurcations segmented from computed tomography with bifurcation angles of 33°, 68°, and 117° were scaled-up ∼7× and 3D printed. Steady coronary flow was reproduced in these phantoms using the principle of dynamic similarity to preserve the true-scale Reynolds number, using blood analog fluid and a pump circuit in a 3T MRI scanner. After PC-MRI acquisition, the data were segmented and coregistered to CFD simulations of identical, but true-scale geometries. Velocities at the inlet region were extracted from the PC-MRI to define the CFD inlet boundary condition. Results: The PC-MRI and CFD flow data agreed well, and comparison showed: 1) small velocity magnitude discrepancies (2-8%); 2) with a Spearman's rank correlation ≥0.72; and 3) a velocity vector correlation (including direction) of r(2) ≥ 0.82. The highest agreement was achieved for high velocity regions with discrepancies being located in slow or recirculating zones with low MRI signal-to-noise ratio (SNRv ) in tortuous segments and large bifurcating vessels. Conclusion: Characterization of coronary flow using a dynamically scaled PC-MRI phantom flow is feasible and provides higher resolution than current in vivo or true-scale in vitro methods, and may be used to provide boundary conditions for true-scale CFD simulations. J. Magn. Reson. Imaging 2016.
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POSTER PRESENTATION Open Access
A new method to quantify coronary flow
conditions using dynamically scaled in vitro
phase contrast magnetic resonance imaging
Susann Beier
1*
, John Ormiston
2
, Mark Webster
3
, John Cater
4
, Stuart Norris
4
, Pau Medrano-Gracia
1
, Alistair Young
1
,
Brett R Cowan
1
From 19th Annual SCMR Scientific Sessions
Los Angeles, CA, USA. 27-30 January 2016
Background
Atherosclerotic coronary artery disease remains a major
cause of illness and death, and coronary flow predeter-
mines disease. Limitations in imaging technology pre-
vent coronary flow measurements but computational
fluid dynamics (CFD) need sophisticated boundary con-
ditions for accurate flow predictions. MRI has recently
been combined with CFD for larger calibre vessels, but
small coronary arteries remain inaccessible.
The aim of this study was to assess the feasibility of cor-
onary flow measurement in 3D printed large scale coron-
ary phantoms using phase contrast MRI (PC-MRI).
Methods
1) Three patient bifurcation geometries with 33°, 72° and
110° angle (mean and ± 2SD of the first principal mode
of variation of 300 asymptomatic patients) were 2) 6:1
printed, and their flow was replicated via a dynamically
scaled blood mimicking flow circuit. The PC-MRI
1
Anatomy with Radiology, Auckland University, Auckland, New Zealand
Full list of author information is available at the end of the article
Figure 1 Detailed flow comparison for the 110 degree patient bifurcation with i) velocity norm contours of real-scale CFD (left),
dynamically scalled PC-MRI (middle) and their difference (right) in ii) four planes of the flow field volume.
Beier et al.Journal of Cardiovascular Magnetic
Resonance 2016, 18(Suppl 1):P103
http://www.jcmr-online.com/content/18/S1/P103
© 2016 Beier et al. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://
creativecommons.org/licenses/by/4.0), which permits unr estricted use, distribution, and reproduction in any medium, provided the
original work is properly cited. The Cre ative Commons Public Do main Dedication waiver (http://creativecommons.org/publicdomain/
zero/1.0/) applies to the data made availa ble in this article, unless otherwise stated.
measured flow was measured was semi-automatically
segmented and co-registered to 3) identical, real scale
CFD. Measured velocity inlets profiles were transformed
and prescribed as CFD inlet condition. The data was sta-
tistically compared using a 3D flow field correlation
analysis.
Results
Coronary flow was successfully replicated and measured
with dynamically scaled 3D printed phantom PC-MRI,
where co-registration (s<5e-6) resulted in good to
strong agreement in magnitude (error 2-12%, r≥0.72),
and direction (r
2
≥0.74).
Conclusions
We have successfully developed, validated and applied a
new method to quantify coronary haemodynamics by com-
bining enlarged 3D printed PC-MRI flow with CFD simula-
tions. With this methodology, the PC-MRI measurements
can be used to define accurate boundary conditions to ele-
vate CFD simulations and ultimate improve predictions
about stent design, coronary artery risk assessment and
clinical practice. PC-MRI is non-invasive, accurate imaging
technology and has the potential to become an important
measurement tool to aid early CFD detection of cardiovas-
cular disease, to risk stratify and optimise treatment for
individual patients.
Authors’details
1
Anatomy with Radiology, Auckland University, Auckland, New Zealand.
2
Mercy Angiography, Auckland, New Zealand.
3
ADHB, Auckland, New
Zealand.
4
Engineering Sciences, Faculty of Engineering, Auckland, New
Zealand.
Published: 27 January 2016
doi:10.1186/1532-429X-18-S1-P103
Cite this article as: Beier et al.: A new method to quantify coronary flow
conditions using dynamically scaled in vitro phase contrast magnetic
resonance imaging. Journal of Cardiovascular Magnetic Resonance 2016 18
(Suppl 1):P103.
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Beier et al.Journal of Cardiovascular Magnetic
Resonance 2016, 18(Suppl 1):P103
http://www.jcmr-online.com/content/18/S1/P103
Page 2 of 2
... MRI has not been *This work was financially supported by the Auckland Charitable Heart Trust, the Auckland Medical Research Foundation (AMRF) and the Auckland Academic Health Alliance (AAHA). 1 applied to coronary flow before because of limited temporal and spatial resolution. Previously we successfully used dynamically scaled in vitro coronary blood flow experiments to over-come these imaging limitations [5]. In this study, we explore if the same methodology is sufficiently adequate to capture changes to blood flow on the micro scale that are a result of stents in coronary arteries. ...
... Both a Newtonian and a non-Newtonian fluid was used experimentally. The experimental and numerical methods have been previously described in [5] and [8] and are summarized here briefly. ...
... The lumen was smoothed using Poisson surface reconstruction, cut and rendered and extended in the open-source VMTK software (Vascular modelling tool kit, www.vmtk.org) as detailed in an earlier publication [5]. The virtual geometry was then imported into AutoCAD Inventor (2016, AutoDesk, SanRafael, CA, USA). ...
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... spatial resolution and a 2D rather than 3D standard imaging have hindered the effective capture of complex coronary anatomical characteristics. This is particularly apparent compared to related, more advanced fields such as carotid research, since carotid arteries are comparatively easier to image as they are larger, stagnant, and close to the body surface 7,8 . Consequently, the detection of shape biomarkers for the carotid arteries is further developed and was demonstrated to directly correlate to shape features such as the angle of origin 9 , and vessel curvature 10 , showcasing the distinct relationship between vessel anatomy and adverse flow 11 . ...
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... Device manufacturers and researchers with an interest in cardiovascular modelling, prediction and treatment of coronary artery disease can analyse this data directly or combine it with other available datasets. The smooth surface meshes and centrelines can be directly used for computational modelling 16 , directly 3D printed for experiments [18][19][20][21] , assist in developing and testing medical devices such as stents [22][23][24] , and can be used for Virtual Reality applications for education and training [25][26][27] . Moreover, our dataset allows for the development and benchmarking of new segmentation algorithms aiming to efficiently annotate the coronary arteries automatically as per ASOCA challenge 28 . ...
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... Device manufacturers and researchers with an interest in cardiovascular modelling, prediction and treatment of coronary artery disease can analyse this data directly or combine it with other available datasets. The smooth surface meshes and centrelines can be directly used for computational modelling 17 , directly 3D printed for experiments [19][20][21][22] , assist in developing and testing medical devices such as stents [23][24][25] , and can be used for Virtual Reality applications for education and training [26][27][28] . Moreover, our dataset allows for the development and benchmarking of new segmentation algorithms aiming to efficiently annotate the coronary arteries automatically as per ASOCA challenge 29 . ...
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... A parabolic flow profile was prescribed at the inlet and constant pressure of 0 atm at the outlet 24 . The constant pressure outlet has also been a common assumption in published literature 42,43 and is generally accepted for healthy vessels since realistic outlet conditions are often not available, and because of previous published validation with in vitro data 44 . The velocity-time profile and flow rate were adapted from previous studies 45 , and the flow was scaled according to equation developed by Giessen et al. ( q = 1.43d 1.55 ) 46 using the inlet radii 47 . ...
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Article
  • Apr 2013
Purpose: Coronary plaque has been shown to directly affect the blood parameters, however, haemodynamic variations based on the plaque configuration has not been studied. In this study we investigate the haemodynamic effects of various types of plaques in the left coronary bifurcation. Methods: Eight types of plaque configurations were simulated and located in various positions in the left main stem, the left anterior descending and left circumflex to produce a >50% narrowing of the coronary lumen. We analyse and characterise haemodynamic effects caused by each type of plaque. Computational fluid dynamics was performed to simulate realistic physiological conditions that reveal the in vivo cardiac haemodynamics. Velocity, wall shear stress (WSS) and pressure gradient (PSG) in the left coronary artery were calculated and compared in all plaque configurations during cardiac cycles. Results: Our results showed that the highest velocity and PSG were found in the type of plaque configuration which involved all of the three left coronary branches. Plaques located in the left circumflex branch resulted in highly significant changes of the velocity, WSS and PSG (p<0.001) when compared to the other types of plaque configurations. Conclusion: Our analysis provides an insight into the distribution of plaque at the left bifurcation, and corresponding haemodynamic effects, thus, improving our understanding of atherosclerosis.
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