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Dustin Ragan - PhD Research

Dustin Ragan
Dustin.Ragan@mdanderson.org

BA, 2003, Mathematics, Trinity University
MS, 2006, Medical Physics, University of Texas HSC - Houston 


Project: Dynamic 19F Spectroscopy 

Dustin works on quantitatively imaging the mouse heart really really fast.  Long version:  Mice are commonly used by researchers to study disease processes and the responses of tumors to experimental therapies.  One tool used to assess the mice is dynamic contrast enhanced (DCE) magnetic resonance imaging (MRI), which involves injecting contrast agent into the mice and rapidly acquiring images to observe the contrast as it gets taken up into tissue.  Generally, tumors will show more rapid uptake than healthy tissue.  The signal changes of the tumor tissue over time can be converted into an expression of the tumor physiology, i.e., from the uptake curves we can calculate estimates of the blood vessel wall’s permeability and the amount of local blood flow, however, this requires a measurement in blood to serve as a calibration.  This is rather difficult to accomplish because it requires imaging very small structures (mouse blood vessels) very rapidly (a mouse’s heart beats 300 times a minute, and that’s under anesthesia), and also because blood flow can substantially alter signals measured in blood.  This is where my research comes in.  First, we make our lives easier by including the heart in the area we image.  This resolves the size issue.  To address the problem of inflow enhancement, we have developed a technique for forcing the blood that is coming into the heart to be in equilibrium with the blood that is already there, and to do so simultaneously with other parts of the MR acquisition, so that it does not require additional time.  To improve the temporal resolution of the heart measurement, we have developed a reconstruction approach that takes advantage of that fact that once you know what shapes are present in an image, it requires much less data to figure out how the images is changing.  This lets us reduce our sampling time from about 4 seconds to about 80 milliseconds.  We’ve used these techniques to show that our measurements in the blood are considerably more reproducible than we could previously achieve, which should reduce the uncertainty when we make measurements of flow and perfusion in mice.

Advisor: James Bankson, PhD 
Career Goal:  Academic Medical Physics

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