Estimation of the measurement uncertainty in magnetic resonance velocimetry based on statistical models

Bruschewski, Martin; Freudenhammer, Daniel; Buchenberg, Waltraud B.; Schiffer, Heinz-Peter; Grundmann, Sven

doi:10.1007/s00348-016-2163-3

Cited by 37 publications

(18 citation statements)

References 38 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In the first time step, a length scale for the velocity amplitudes is given an inverse Fourier transformation, this will lead to image artifacts along the entire phase encoding direction. Random motion as well as random velocity fluctuations during image acquisition therefore results in an additional noise distribution, which are referred to as turbulence artifacts (Bruschewski et al 2016).…”

Section: Turbulence and Velocity Fluctuationsmentioning

confidence: 99%

See 1 more Smart Citation

Analysis of the wall shear stress in a generic aneurysm under pulsating and transitional flow conditions

et al. 2020

View full text Add to dashboard Cite

In this study, the flow through a generic abdominal aneurysm under realistic pulsating flow conditions is examined with magnetic resonance velocimetry (MRV), laser Doppler velocimetry (LDV) and computational fluid dynamics (CFD). The influence of flow phenomena on the wall shear stress (WSS) is examined. It is seen that a strong vortex ring develops during systole at the proximal end of the aneurysm and subsequently travels downstream and decays. The vortex formation plays a major role in the temporal and spatial distribution of the WSS, which is analyzed in detail. A peak of the WSS is observed for a very limited time and in a very localized region where the vortex ring initially develops. The intrinsic temporal averaging during the acquisition of the MRV data is found to significantly decrease this peak. CFD and LDV results, which are averaged in the same manner, show a similar behavior. This indicates that besides the spatial resolution, the temporal resolution is a crucial factor, which needs to be considered especially in flows where vortex rings are observed. Results from LDV and CFD show excellent agreement for the velocity field obtained by MRV. While the flow is found to be laminar in the undilated diameter, results show laminar-turbulent transitional behavior for specific phases of the cycle within the aneurysm bulk. Although MRV is not capable of measuring instantaneous velocity fluctuations, we show that the periodic increase in turbulence intensity can be observed from image artifacts in the MRV data. These artifacts increase the velocity uncertainty, which correlates well with the velocity fluctuations measured with LDV. Although the flow encounters laminar and transitional conditions as well as multiple vortices and stagnation and reattachment points, the improved instabilitysensitive Reynolds stress model, which is used for the numerical simulations of this work, shows very good agreement with the measurements. Significant effort has been expended by numerous research groups in recent years in improving the estimation of WSS from MRV data. However, an assessment of these various post-processing methods is only possible if the true values of the WSS are known. The present study is therefore aimed at providing such ground truth WSS values as well as the corresponding MRV data, allowing also other research groups to validate their WSS estimation methods using the experimental data set presented in this work.

show abstract

Section: Turbulence and Velocity Fluctuationsmentioning

confidence: 99%

“…For the MRV data, the velocity uncertainty is calculated according to Constantinides et al (1997) and Bruschewski et al (2016)…”

Section: Turbulence and Velocity Fluctuationsmentioning

confidence: 99%

Analysis of the wall shear stress in a generic aneurysm under pulsating and transitional flow conditions

et al. 2020

View full text Add to dashboard Cite

show abstract

“…One of the most important sources of noise in an MRI measurement is the thermal noise of the receiver chain. Bruschewski et al [3] presented a robust calculation of the measurement uncertainty from the variance (Var) of two equally measured images A and B…”

Section: Velocity Measurementmentioning

confidence: 99%

“…An inherent feature of MRI is the comparatively fast two-or three-dimensional data acquisition inside opaque systems. Various studies demonstrated that MRI is capable of estimating values of different flow properties quantitatively, such as velocity, temperature, Reynolds stresses, and species concentrations in technical fluid systems [3,7].…”

Section: Introductionmentioning

confidence: 99%

Towards Analyzing the Influence of Measurement Errors in Magnetic Resonance Imaging of Fluid Flows

et al. 2020

Self Cite

View full text Add to dashboard Cite

Magnetic Resonance Imaging (MRI) provides an insight into opaque structures and does not only have a large number of applications in the field of medical examinations but also in the field of engineering. In technical applications, MRI enables a contactless measurement of the two-or threedimensional velocity field within minutes. However, various measurement methods would benefit from an acceleration of the measurement procedure. Compressed Sensing is a promising method to fit this need. A random undersampling of the sampled data points enables a significant reduction of acquisition time. As this method requires a nonlinear iterative reconstruction of unmeasured data to obtain the same data quality as for a conventional fully sampled measurement, it is essential to estimate the influence of uncertainty on the quantitative result. This paper investigates the implementation of interval arithmetic approaches with a focus on the applicability in the frame of compressed sensing techniques. These approaches are able to handle bounded uncertainty not only in the case of linear relationships between measured data and the computed outputs but also allow for solving the necessary optimality criteria for the fluid velocity reconstruction in an iterative manner under the assumption of set-valued measurement errors and bounded representations of noise.

show abstract

“…Effective quantitative details such as in-cylinder flow velocity, velocity root-mean-square (rms), circulation, and turbulent length and time scales are being made possible from such advanced measurement techniques. Magnetic resonance imaging is yet another technique, majorly used in medical field, which has been recently employed for engine flow studies in the form of magnetic resonance velocimetry (MRV) [17][18][19]. A major advantage of MRV is that optical access is not needed for data acquisition, allowing it to be used for flow imaging in highly complex geometries.…”

Section: Introductionmentioning

confidence: 99%

Parametric Study to Improve Subpixel Accuracy of Nitric Oxide Tagging Velocimetry with Image Preprocessing

Vedula

Mittal

Schock

2017

Journal of Combustion

View full text Add to dashboard Cite

Biacetyl phosphorescence has been the commonly used molecular tagging velocimetry (MTV) technique to investigate in-cylinder flow evolution and cycle-to-cycle variations in an optical engine. As the phosphorescence of biacetyl tracer deteriorates in the presence of oxygen, nitrogen was adopted as the working medium in the past. Recently, nitrous oxide MTV technique was employed to measure the velocity profile of an air jet. The authors here plan to investigate the potential application of this technique for engine flow studies. A possible experimental setup for this task indicated different permutations of image signal-to-noise ratio (SNR) and laser line width. In the current work, a numerical analysis is performed to study the effect of these two factors on displacement error in MTV image processing. Also, several image filtering techniques were evaluated and the performance of selected filters was analyzed in terms of enhancing the image quality and minimizing displacement errors. The flow displacement error without image preprocessing was observed to be inversely proportional to SNR and directly proportional to laser line width. The mean filter resulted in the smallest errors for line widths smaller than 9 pixels. The effect of filter size on subpixel accuracy showed that error levels increased as the filter size increased.

show abstract

Estimation of the measurement uncertainty in magnetic resonance velocimetry based on statistical models

Cited by 37 publications

References 38 publications

Analysis of the wall shear stress in a generic aneurysm under pulsating and transitional flow conditions

Analysis of the wall shear stress in a generic aneurysm under pulsating and transitional flow conditions

Towards Analyzing the Influence of Measurement Errors in Magnetic Resonance Imaging of Fluid Flows

Parametric Study to Improve Subpixel Accuracy of Nitric Oxide Tagging Velocimetry with Image Preprocessing

Contact Info

Product

Resources

About