The overall objective of this work is to develop a non-invasive MRI based method for mapping of Oxygen Extraction Fraction (OEF). OEF is thought to be a more specific indicator of penumbra (under perfused but salvageable brain tissue) in stroke than other quantities, and is therefore important for prudent decision-making in the management of stroke patients. OEF is also a key factor in the understanding of cerebral metabolism and contrast mechanisms in BOLD functional imaging. In this work, venous T2 will be used as a surrogate for venous oxygenation, as there is known to be a tight relationship between these two quantities. Recent work has shown that whole-brain measurements of OEF can be made using T2 measurements in the major draining veins of the head. We will develop a new approach that will map T2 and thereby OEF throughout the brain, providing regionally specific information. Our approach is comprised of three modules: 1) selective excitation of moving spins using a novel velocity selective excitation scheme;2) nulling of arterial signal using inversion tagging of inflowing arterial blood;and 3) mapping of T2 using flow compensated multi-echo, or T2 prepared imaging. We have proposed technical improvements to each of these components, and will implement, test, and optimize these improvements. We will quantify the sources of residual errors in the OEF measurement so that the accuracy of the method is well characterized. At the conclusion of this work, we expect to have an optimized method for non-invasive OEF measurement in the human brain that provides a solid foundation for further technical development and/or translational research.

Public Health Relevance

This project will produce a new non-invasive MRI based method for mapping of the oxygen extraction fraction (OEF) of the brain. OEF is thought to be the best marker for the detection of salvageable brain tissue in stroke patients, and imaging of this measure may significantly improve decision making in the treatment of these patients. In addition, non-invasive OEF mapping will allow for a better understanding of energy metabolism in the brain, as well as the physiological basis of functional brain imaging using blood oxygenation level dependent (BOLD) contrast.

Agency
National Institute of Health (NIH)
Institute
National Institute of Biomedical Imaging and Bioengineering (NIBIB)
Type
Exploratory/Developmental Grants (R21)
Project #
5R21EB013821-02
Application #
8462974
Study Section
Biomedical Imaging Technology Study Section (BMIT)
Program Officer
Liu, Guoying
Project Start
2012-05-01
Project End
2014-04-30
Budget Start
2013-05-01
Budget End
2014-04-30
Support Year
2
Fiscal Year
2013
Total Cost
$173,419
Indirect Cost
$55,544
Name
University of California San Diego
Department
Radiation-Diagnostic/Oncology
Type
Schools of Medicine
DUNS #
804355790
City
La Jolla
State
CA
Country
United States
Zip Code
92093