Measurement and Correction for the Magnetic Susceptibility Effects of Fat in Venous Oximetry: Application in the Quantification of Muscle Oxygen Consumption (VO2) with Plantar Flexion Exercise

• Author / Creator

  Yang, Hyun Joo E

• Measuring venous oxygen saturation (SvO2) provides direct assessment of the upstream muscle or organ's ability to extract and metabolize oxygen. Previously, measurement of venous oxygen saturation has been performed in most studies by intravenous catheterization. This approach has the advantage of continuous monitoring at the bedside, but the catheter insertion is an invasive method and has risks including venous infection and thrombosis. Magnetic Resonance Imaging (MRI) has the potential to estimate the blood oxygen saturation level based on the difference of the magnetic properties of oxygenated and deoxygenated hemoglobin in the blood. While oxyhemoglobin is diamagnetic, deoxyhemoglobin is paramagnetic relative to the surrounding tissue which makes it possible to estimate venous oxygen saturation levels, which is termed oximetry. In magnetic susceptometry-based oximetry, the vessel is modeled as a long paramagnetic cylinder immersed in an external uniform magnetic field. The resulting magnetic field shift within cylindrical blood vessels can be used to estimate venous oxygen saturation, based on the known magnetic susceptibility of deoxyhemoglobin. However, conduit veins in the periphery are often surrounded by fat, which has a different magnetic susceptibility than water and the venous blood pool. The potentially complex magnetic field perturbation from the fat may extend into the vein and the surrounding muscle reference tissue, potentially confounding estimation of the venous oxygen saturation. In this thesis, new methods for the measurement and correction of the unwanted magnetic susceptibility effects of fat are explored, to enable magnetic susceptometry-based venous oximetry in the presence of large fat pools around the targeted veins. Compatibility with dynamic imaging in associated with plantar flexion (calf) exercise is evaluated. The addition of flow-encoding gradients enable phase-contrast evaluation of venous blood flow in the same acquisition, which allow for direct calculation of the volume of muscle oxygen consumption, VO2, which is the product of oxygen extraction and blood flow.

• Subjects / Keywords

  • Magnetic Resonance Imaging
  • Exercise
  • Magnetic Susceptibility
  • Fat
  • Oxygen Consumption
  • Venous Oximetry

• Graduation date

  Spring 2018

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/R3WP9TN6K

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.