Before arriving at Harvard, I worked on biomedical signal and image processing problems. My undergraduate thesis at Penn State University dealt with the graphical analysis of three-dimensional coronary angiograms. I developed an improved method for estimating the central axes of the various coronary arteries. This work was one portion of a larger effort by the laboratory of Prof. William Higgins to create "fly-throughs" of the coronary arteries for stenosis detection. These movies can be viewed at the Penn State Bioengineering website. At Northeastern University, I worked with Prof. Dana Brooks to examine heart sound signals during general anesthesia. It was hypothesized that the condition of hypovolemia (low blood volume) could be automatically detected during surgery to eliminate the guesswork involved to determine when the patient needs additional fluid. Members of Cohen's class of time frequency transforms were analyzed to distinguish between low, normal, and high blood volume levels.
	Griebel, S., "Time-Frequency Analysis of Heart Sound Signals to Detect Hypovolemia During General Anesthesia," M.S. Thesis, Northeastern University, 1996.
	Griebel, S., "Improved methods for three-dimensional coronary angiographic analysis," Senior Honors Thesis, Penn State University, 1994.