Education

• Ph.D. Candidate in Biomedical Engineering, present, Washington University, St. Louis, MO
  
• M.S. in Biomedical Engineering, 2006, Washington University, St. Louis, MO
  
• B.S. in Electrical Engineering, 2004, Tufts University, Medford, MA
  Undergraduate research advisor: Misha E. Kilmer, Ph.D.
  
• Second Major in Biomedical Engineering, 2004, Tufts University, Medford, MA
  

Current Research Interests

One focus is on making improvements to image reconstruction techniques used in x-ray computed tomography (CT). The two primary classes of algorithms used for image reconstruction are analytical and statistical methods. While analytical methods, such as filtered backprojection (FBP), are routinely used in clinical practice due to their fast performance, they tend not to be as accurate as the statistical methods (such as maximum likelihood estimation) in low-count or other non-ideal situations. Such situations could arise if the patient's arms are partially outside the field of view, if the patient has metal implants, if the patient is obese, or for a wide variety of other reasons. The major downside of most existing statistical reconstruction techniques is that they are iterative and therefore very slow compared to FBP, especially for large 3D clinical datasets. I have implemented a highly optimized parallelized version of an alternating minimization algorithm for fully 3D imaging to help minimize the computation time.

The second focus of my research is to develop fully 3D reconstruction techniques for a novel positron emission tomography (PET) breast/head and neck imaging system. The goal of this system is to enhance the resolution and sensitivity in specific regions of interest relative to a whole-body PET scanner, while still maintaining the field of view of the whole-body PET scanner. This is accomplished by placing a half-ring of high-resolution LSO crystals in the center of the field of view. With this detector geometry, three types of coincidences are simulatenously collected, each of different resolution: insert-insert, insert-scanner, and scanner-scanner. Our reconstruction algorithm accurately models the acquired data, and determines the maximum likelihood emission image estimate based on all three types of data. This approach is expected to yield the highest resolution in the field of view of the half-ring insert, yet maintain a typical whole-body PET scanner resolution in other parts of the image. Many data corrections are necessary for this system, most importantly attenuation correction and normalization.

Conferences

• D. Keesing, D. Pal, J. O’Sullivan, S. Komarov, Y.-C. Tai, "System Modeling of a DOI-Capable PET Insert Device for Breast Imaging," IEEE Medical Imaging Conference, Dresden, Germany, October 19-25, 2008.
• D. Pal, D. Keesing, J. O'Sullivan, S. Komarov, Y.-C. Tai, "Image Reconstruction Algorithm for a Half-Ring PET-Insert System," IEEE Medical Imaging Conference, Honolulu, HI, October 28-November 3, 2007.
• J. Williamson, D. Politte, J. O'Sullivan, D. Keesing, B. Whiting, D. Lazos, J. Evans, "Improving Noise vs. Resolution Tradeoffs in X-Ray CT Imaging by Statistical Image Reconstruction," AAPM, Minneapolis, MN, July 22-26, 2007.
• D. Keesing, J. O'Sullivan, D. Politte, B. Whiting, D. Snyder, "Missing Data Estimation for Fully 3D Spiral CT Image Reconstruction," SPIE Medical Imaging: Physics of Medical Imaging, San Diego, CA, February 17-22, 2007.
• D. Keesing, J. O'Sullivan, D. Politte, B. Whiting, "Parallelization of a Fully 3D CT Iterative Reconstruction Algorithm," IEEE International Symposium on Biomedical Imaging, Arlington, VA, April 6-9, 2006.
• M. Kilmer, D. Keesing, E. Miller, D. Boas, "3D Imaging of Absorption and Scatter for Diffuse Optical Tomography," SIAM Conference on Imaging Science, Salt Lake City, UT, May 3-5, 2004.
• D. Keesing, "A 3D Image Reconstruction Technique for Diffuse Optical Tomography," Research by Undergraduates in Mathematics Boston University Symposium, Boston, MA, April 24, 2004.
• D. Keesing, "A 3D Image Reconstruction Technique for Diffuse Optical Tomography," Tufts University Undergraduate Research & Scholarship Symposium, Medford, MA, March 13, 2004.
• E. Miller, A. Hamdi, D. Keesing, M. Kilmer, M. Franceschini, D. Boas, "Recursive Estimation Methods for Tracking of Localized Perturbations in Absorption and Scattering using Diffuse Optical Tomography," SPIE Electronic Imaging, San Jose, CA, January 18-22, 2004.

Journal Articles

• M. Gerber, B. Hasselblatt, D. Keesing, "The Riccati equation: pinching of forcing and solutions," Experimental Mathematics, 12(2), pp. 129-134, June 2003.

Awards

• National Science Foundation Graduate Research Fellowship, Fall 2005 - Summer 2008

Current Memberships

• IEEE (Institute of Electrical and Electronics Engineers)
• SIAM (Society for Industrial and Applied Mathematics)
• Tau Beta Pi
• Eta Kappa Nu