Simulation of phase contrast MRI of turbulent flow

Petersson, Sven; Dyverfeldt, Petter; Gårdhagen, Roland; Karlsson, Matts; Ebbers, Tino

doi:10.1002/mrm.22494

Cited by 50 publications

(42 citation statements)

References 28 publications

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“…Estimation of IVSD from Cartesian PC-MRI has been shown to agree well with CFD simulations, laser Doppler anemometry and particle image velocimetry [65][66][67]137]. Total TKE values in the post-stenotic region of the phantom were obtained by integration of the TKE in the phantom between the center of the stenosis and six diameters downstream.…”

Section: Discussionmentioning

confidence: 97%

Fast and Accurate 4D Flow MRI for Cardiovascular Blood Flow Assessment

Petersson¹

2013

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The study of blood flow is essential in understanding the physiology and pathophysiology of the cardiovascular system. Small disturbances of the blood flow may over time evolve and contribute to cardiovascular pathology. While the blood flow in a healthy human appears to be predominately laminar, turbulent or transitional blood flow is thought to be involved in the pathogenesis of several cardiovascular diseases. Wall shear stress is the frictional force of blood on the vessel wall and has been linked to the pathogenesis of atherosclerosis and aneurysms. Despite the importance of hemodynamic factors, cardiovascular diagnostics largely relies on the indirect estimation of function based on morphological data.Time-resolved three-dimensional (3D) phase-contrast magnetic resonance imaging (MRI), often referred to as 4D flow MRI, is a versatile and non-invasive tool for cardiovascular blood flow assessment. The use of 4D flow MRI permits estimation of flow volumes, pressure losses, wall shear stress, turbulence intensity and many other unique hemodynamic parameters. However, 4D flow MRI suffers from long scan times, sometimes over 40 minutes. Furthermore, the accuracy of the many different 4D flow MRI-based applications and estimates have not been thoroughly examined.In this thesis, the accuracy of 4D flow MRI-based turbulence intensity mapping and wall shear stress estimation was investigated by using numerical simulations of MRI flow measurements. While the results from the turbulence intensity mapping agreed well with reference values from computational fluid dynamics data, the accuracy of the MRI-based wall shear stress estimates was found to be very sensitive to different parameters, especially to spatial resolution, and wall shear stress values over 5 N/m 2 were not well resolved.To reduce the scan time, a 4D flow MRI sequence using spiral k-space trajectories was implemented and validated in-vivo and in-vitro. The scan time of 4D flow MRI was reduced by more than two-fold compared to a conventional Cartesian acquisition already accelerated using SENSE factor 2, and the data quality was maintained. For a 4D flow scan of the human heart, the use of spiral k-space trajectories resulted in a scan time of around 13 min, compared to 30 min for the Cartesian acquisition. By combining parallel imaging and spiral trajectories, the total scan time of a 4D flow measurement of the entire heart may be further reduced. This scan time reduction may also be traded for higher spatial resolution.Numerical simulation of 4D flow MRI may act as an important tool for future optimization and validation of the spiral 4D flow sequence. The scan-time reductions offered by the spiral k-space trajectories can help to cut costs, save time, reduce discomfort for the patient as well as to decrease the risk for motion artifacts. These benefits may facilitate an expanded clinical and investigative use of 4D flow MRI, including larger patient research studies.v Populärvetenskaplig sammanfattningHjärt-och kärlsjukdom är fortfarande den ...

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Section: Discussionmentioning

confidence: 97%

Fast and Accurate 4D Flow MRI for Cardiovascular Blood Flow Assessment

Petersson¹

2013

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“…If future device modifications were to achieve MRI compatibility, quantitative flow mapping and flow velocity measurements might be possible [17]. This type of assessment is important because inhomogeneous flow might not only reduce actual diffusion efficiency relative to the ideal, but may also increase predispose to intra-device thrombus formation in the implanted setting.…”

Section: Discussionmentioning

confidence: 99%

In vivo dielectric measuring instrument using picosecond pulse for detection of oral cancer

Olorunsola¹,

Kim²,

Rs³

et al. 2014

Med Instrum

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BackgroundThe purpose of this study was to investigate the utility and limitations of various imaging modalities in the noninvasive assessment of a novel compact hemodialyzer under development for renal replacement therapy, with specific aim towards monitoring its functional performance.MethodsThe prototype is a 4×3×6 cm aluminum cartridge housing “blood” and “dialysate” flow paths arranged in parallel. A sheet of semipermeable silicon nanopore membranes forms the blood-dialysate interface, allowing passage of small molecules. Blood flow was simulated using a peristaltic pump to instill iodinated contrast through the blood compartment, while de-ionized water was instilled through the dialysate compartment at a matched rate in the countercurrent direction. Images were acquired under these flow conditions using multi-detector computed tomography (MDCT), fluoroscopy, high-resolution quantitative computed tomography (HR-QCT), and magnetic resonance imaging (MRI). MDCT was used to monitor contrast diffusion efficiency by plotting contrast density as a function of position along the path of flow through the cartridge during steady state infusion at 1 and 20 mL/min. Both linear and exponential regressions were used to model contrast decay along the flow path.ResultsBoth linear and exponential models of contrast decay appeared to be reasonable approximations, yielding similar results for contrast diffusion during a single pass through the cartridge. There was no measurable difference in contrast diffusion when comparing 1 mL/min and 20 mL/min flow rates. Fluoroscopy allowed a gross qualitative assessment of flow within the device, and revealed flow inhomogeneity within the corner of the cartridge opposite the blood inlet port. MRI and HR-QCT were both severely limited due to the paramagnetic properties and high atomic number of the target material, respectively. During testing, we encountered several causes of device malfunction, including leak formation, trapped gas, and contrast-mediated nanopore clogging. We illustrate the imaging manifestations of each.ConclusionsDespite the inherent challenges in imaging a predominantly metallic device, some modalities show potential in the non-invasive assessment of a novel compact hemodialyzer. The approaches described here could potentially be translated to device evaluation in the implanted setting.

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“…Contrary to other recently proposed approaches (see for example [14,25]), we did not use CFD data as the input to solve the Bloch equations with a Eulerian-Lagrangian approach in which particle trajectories of virtual spin packets are computed to quantify the intra-voxel phase dispersion (and, hence, to exploit how the presence of multiple spin velocities within a voxel affect the MR signal magnitude). In the same way, we did not check for partial volume artifacts, displacement artifacts and presence of eddy currents, concomitant gradient field effects and nonlinear magnetic gradient fields.…”

Section: Discussionmentioning

confidence: 99%

Synthetic dataset generation for the analysis and the evaluation of image-based hemodynamics of the human aorta

Morbiducci

Ponzini

Rizzo

et al. 2011

Med Biol Eng Comput

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Here, we consider the issue of generating a suitable controlled environment for the evaluation of phase contrast (PC) MRI measurements. The computational framework, tailored to build synthetic datasets, is based on a two-step approach, i.e., define and implement (1) an accurate CFD model and (2) an image generator able to mime the overall outcomes of a PC MRI acquisition starting from datasets retrieved by the computational model. About 20 different datasets were built by changing relevant image parameters (pixel size, slice thickness, time frames per cardiac cycle). Focusing our attention on the thoracic aorta, synthetic images were processed in order to: (1) verify to which extent the fluid dynamics into the aortic arch is influenced by the image parameters; (2) establish the effect of spatial and temporal interpolation. Our study demonstrates that the integral scale of the aortic bulk flow could be described satisfactorily even when using images which are nowadays acquirable with MRI scanners. However, attention must be paid to near-wall velocities that can be affected by large inaccuracy. In detail, in bulk flow regions error values are well bounded (below 5% for most of the analyzed resolutions), while errors greater than 100% are systematically present at the vessel's wall. Moreover, also the data interpolation process can be responsible for large inaccuracies in new data generation, due to the inherent complexity of the flow field in some connected regions.

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Simulation of phase contrast MRI of turbulent flow

Cited by 50 publications

References 28 publications

Fast and Accurate 4D Flow MRI for Cardiovascular Blood Flow Assessment

Fast and Accurate 4D Flow MRI for Cardiovascular Blood Flow Assessment

In vivo dielectric measuring instrument using picosecond pulse for detection of oral cancer

Synthetic dataset generation for the analysis and the evaluation of image-based hemodynamics of the human aorta

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