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Flow Measurements in Turbulent Flow Fields with Magnetic Resonance Phase Velovity Mapping

Lakkadi, Navneeth Sagar Reddy

Abstract Details

2009, Master of Science in Chemical Engineering, Cleveland State University, Fenn College of Engineering.
Arterial stenosis (narrowing) is due to vascular disease that, if untreated, leads to death. The stenosis causes the development of complex flow which results in high energy losses and great forces between blood and tissue. Traditionally, turbulent flows lead to signal loss in magnetic resonance (MR) image acquisitions, resulting in loss of diagnostic information. With the advancement in MR hardware and software, some of the limitations of MR in turbulent flow fields may have been reduced or eliminated. This study evaluated the potential of MR phase velocity mapping (MRPVM), a clinical velocimetry technique, under turbulent flow conditions such as those developed in arterial stenosis. Specifically, the goal of this study was to determine how accurately MRPVM can quantify the flow rate in experimental models of arterial stenosis under a variety of flow conditions, ranging from laminar to turbulent. Three models were used: a non-occluded straight tube; an occluded tube with a 75% area reduction stenosis; and an occluded tube with a 94% area reduction stenosis. Flow experiments were conducted under steady-state flow conditions (flow rates of 1.4-10.4 L/min) inside a 1.5 Tesla whole-body clinical Siemens MR scanner. Of interest was to vary several imaging parameters which control the time of the acquisitions and the spatial resolution of the acquired images. Therefore, five different echo times (TE) (2.65-6.0 ms) and three different combinations of the field of view and matrix size, resulting in three different spatial resolutions, were studied. Axial MRPVM acquisitions were performed in all models upstream, at the throat, and downstream of the stenosis. The acquired phase images provided the velocity from which the flow rate was calculated. The MR-measured flow rates were compared with the true flow rates from rotameters to determine the accuracy of MRPVM. The results confirmed that MRPVM can measure the flow rate accurately under laminar flow conditions. In turbulent flow, the accuracy was reduced due to signal loss. Underestimation of the flow rate was observed in the most severe stenosis model, downstream of the throat, at the highest flow rate (and thus highest Reynolds number). Overall, the lower the TE was, the more accurate the flow rate measurement was. The effect of spatial resolution seemed to be much weaker than that of TE on the accuracy of the results. Additional experimental studies covering a larger range of Reynolds numbers and geometric features and clinical studies in healthy subjects and patients are necessary to provide information about the clinical potential of MRPVM to measure flow under pathologic flow conditions.
George Chatzimavroudis, Ph.D. (Committee Chair)
Randolph Setser, D.Sc. (Committee Member)
Sridhar Ungarala, Ph.D. (Committee Member)
246 p.

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Citations

  • Lakkadi, N. S. R. (2009). Flow Measurements in Turbulent Flow Fields with Magnetic Resonance Phase Velovity Mapping [Master's thesis, Cleveland State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=csu1251412647

    APA Style (7th edition)

  • Lakkadi, Navneeth Sagar Reddy. Flow Measurements in Turbulent Flow Fields with Magnetic Resonance Phase Velovity Mapping. 2009. Cleveland State University, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=csu1251412647.

    MLA Style (8th edition)

  • Lakkadi, Navneeth Sagar Reddy. "Flow Measurements in Turbulent Flow Fields with Magnetic Resonance Phase Velovity Mapping." Master's thesis, Cleveland State University, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=csu1251412647

    Chicago Manual of Style (17th edition)