SANGTAE AHN's web page

I am a postdoctoral research associate in the Signal and Image Processing Institute of the Electrical Engineering Department at the University of Southern California. I joined the Biomedical Imaging Research Lab (director: Prof. Richard Leahy) at USC after completing my Ph.D. program (advisor: Prof. Jeffrey Fessler) in the Electrical Engineering and Computer Science Department at the University of Michigan. My research interests include image reconstruction and analysis in biomedical imaging applications including molecular imaging---PET (positron emission tomography)/SPECT (single photon emission computed tomography) and optical bioluminescence and fluorescence tomography---and also neuroimaging by MEG (magnetoencephalography)/EEG(electroencephalography). I am also interested in computational biology, systems biology and bioinformatics.

Curriculum Vita

• University of Michigan, Ann Arbor, MI
  Ph.D. in Electrical Engineering: Systems, Dec. 2004
  M.S. in Electrical Engineering: Systems, Apr. 2001
  
• Korea Advanced Institute of Science and Technology, Daejeon, Korea
  M.S. in Mechanical Engineering, Feb. 1999
  B.S. in Mechanical Engineering (summa cum laude), Feb. 1997
  
• RMIT University, Melbourne, Australia
  Student exchange program, 1996
  

• Journal papers
  
  
  1. A. J. Chaudhari, S. Ahn, R. Levenson, R. D. Badawi, S. R. Cherry, R. M. Leahy.
     Excitation spectroscopy in multispectral optical fluorescence tomography: methodology, feasibility and computer simulation studies. [PDF] [LINK]
     Physics in Medicine and Biology, 54(15):4687-4704, Aug. 2009.
  2. S. Ahn, R. T. Wang, C. C. Park, A. Lin, R. M. Leahy, K. Lange, D. J. Smith.
     Directed mammalian gene regulatory networks using expression and comparative genomic hybridization microarray data from radiation hybrids. [PDF] [LINK]
     PLoS Computational Biology, 5(6): e1000407, June 2009.
     *Highlighted in "This Week in PLoS" (June 15, 2009) in GenomeWeb
  3. C. Li, G. S. Mitchell, J. Dutta, S. Ahn, R. M. Leahy, S. R. Cherry.
     A three-dimensional multispectral fluorescence optical tomography imaging system for small animals based on a conical mirror design. [PDF] [LINK]
     Optics Express, 17(9):7571-7585, Apr. 2009.
     *Selected in the Virtual Journal of Biomedical Optics (VJBO), 4(6), May 2009.
  4. S. Cho, S. Ahn, Q. Li, R. M. Leahy.
     Exact and approximate Fourier rebinnings of PET data from time-of-fight to non time-of-flight. [PDF] [LINK]
     Physics in Medicine and Biology,, 54(3):467-484, Feb. 2009.
     *Selected in IOP Select (special collection of journal articles from the Institute of Physics)
     *Covered in a research news article (January 30, 2009) in MedicalPhysicsWeb
  5. S. Ahn, A. J. Chaudhari, F. Darvas, C. A. Bouman, R. M. Leahy.
     Fast iterative image reconstruction methods for fully 3D multispectral bioluminescence tomography. [PDF] [LINK]
     Physics in Medicine and Biology, 53(14):3921-3942, July 2008.
  6. S. Cho, S. Ahn, Q. Li, R. M. Leahy.
     Analytical properties of time-of-flight PET data. [PDF] [LINK]
     Physics in Medicine and Biology, 53(11):2809-2821, June 2008.
     *Selected as a featured article in Physics in Medicine and Biology
     *Covered in a research news article (June 12, 2008) in MedicalPhysicsWeb
  7. C. C. Park, S. Ahn, J. S. Bloom, A. Lin, R. T. Wang, T. Wu, A. Sekar, A. H. Khan, C. J. Farr, A. J. Lusis, R. M. Leahy, K. Lange, D. J. Smith.
     Fine mapping of regulatory loci for mammalian gene expression using radiation hybrids. [PDF] [Supplementary information] [LINK]
     Nature Genetics, 40(4):421-429, Apr. 2008.
     *Erratum: Nature Genetics, 40(5):682, May 2008.
  8. S. Ahn, R. M. Leahy.
     Analysis of resolution and noise properties of nonquadratically regularized image reconstruction methods for PET. [PDF] [LINK]
     IEEE Transactions on Medical Imaging, 27(3):413-424, Mar. 2008.
     *Erratum: In equation (53), x_b on the left hand side should be x_s. The correct equation is here.
  9. S. Cho, Q. Li, S. Ahn, B. Bai, R. M. Leahy.
     Iterative image reconstruction using inverse Fourier rebinning for fully 3D PET. [PDF] [LINK]
     IEEE Transactions on Medical Imaging, 26(3):347-358, Mar. 2007.
     *Correction: IEEE Transactions on Medical Imaging, 26(5):745-767, May 2007.
     
  10. Q. Li, E. Asma, S. Ahn, R. M. Leahy.
      A fast fully 4D incremental gradient reconstruction algorithm for list mode PET data. [PDF] [LINK]
      IEEE Transactions on Medical Imaging, 26(1):58-67, Jan. 2007.
      
  11. S. Ahn, J. A. Fessler, D. Blatt, A. O. Hero.
      Convergent incremental optimization transfer algorithms: Application to tomography. [PDF] [LINK]
      IEEE Transactions on Medical Imaging, 25(3):283-296, Mar. 2006.
      *Erratum: On p.287, the broken equation should be "\mathcal{X} = \{ \mathbf{x}\in{\mathbb{R}^p}: 0 \leq x_j \leq U,\ \ \forall j \}. (11)" in latex. The correct equation is here.
  12. S. Ahn, J. A. Fessler.
      Emission image reconstruction for randoms-precorrected PET allowing negative sinogram values. [PDF] [LINK]
      IEEE Transactions on Medical Imaging, 23(5):591-601, May 2004.
  13. S. Ahn, J. A. Fessler.
      Globally convergent image reconstruction for emission tomography using relaxed ordered subsets algorithms. [PDF] [LINK]
      IEEE Transactions on Medical Imaging, 22(5):613-626, May 2003.
  14. S.-H. Cho, S. Ahn, Y.-H. Kim.
      A simple model to estimate the impact force induced by piston slap. [PDF] [LINK]
      Journal of Sound and Vibration, 255(2):229-242, Aug. 2002.
  15. Y.-H. Kim, S. Ahn.
      A reverberation model based on objective parameters of subjective perception. [PDF]
      Journal of the Audio Engineering Society, 49(9):786-794, Sept. 2001.
      *Highlighted in "Scanning the Journals" by T. D. Rossing in Echoes, 12(1):7, 2002.
  
  
• Conference proceedings papers
  
  
  1. J. Dutta, S. Ahn, A. A. Joshi and R. M. Leahy.
     Optimal illumination patterns for fluorescence tomography.
     Proc. IEEE Intl. Symp. Biomedical Imaging, 2009. In press.
  2. C. Li, G. S. Mitchell, J. Dutta, S. Ahn, R. M. Leahy, S. R. Cherry.
     A high sensitivity multi-spectral three-dimensional fluorescence optical tomography system for small animal imaging. [PDF] [LINK]
     Proc. Optical Tomography and Spectroscopy of Tissue VIII, SPIE Biomedical Optics Symposium (BiOS), vol. 7174, 717415, 2009.
  3. J. Dutta, S. Ahn, C. Li, A. J. Chaudhari, S. R. Cherry, R. M. Leahy.
     Computationally efficient perturbative forward modeling for 3D multispectral bioluminescence and fluorescence tomography. [PDF] [LINK]
     Proc. SPIE Medical Imaging: Physics of Medical Imaging, vol. 6913, 6913C, 2008.
  4. S. Ahn, A. J. Chaudhari, F. Darvas, C. A. Bouman, R. M. Leahy.
     Fast image reconstruction methods for fully 3D multispectral bioluminescence tomography. [PDF] [LINK]
     Proc. IEEE Intl. Symp. Biomedical Imaging, pp. 229-232, 2007.
  5. S. Ahn, R. M. Leahy.
     Analysis of region of interest quantification for PET image reconstruction with selective regularization. [PDF] [LINK]
     Proc. IEEE Nuclear Science Symp. Medical Imaging Conf., vol. 3, pp. 1781-1786, 2006.
  6. S. Ahn, R. M. Leahy.
     Spatial resolution properties of nonquadratically regularized image reconstruction for PET. [PDF] [LINK]
     Proc. IEEE Intl. Symp. Biomedical Imaging, pp. 287-290, 2006. Slides from talk.
  7. S. Cho, Q. Li, S. Ahn, R. M. Leahy.
     Fast projectors for iterative 3D PET reconstruction. [PDF] [LINK]
     Proc. IEEE Nuclear Science Symp. Medical Imaging Conf., vol. 4, pp. 1933-1937, 2005.
  8. Q. Li, S. Ahn, R. M. Leahy.
     Fast hybrid algorithms for PET image reconstruction. [PDF] [LINK]
     Proc. IEEE Nuclear Science Symp. Medical Imaging Conf., vol. 4, pp. 1851-1855, 2005.
  9. S. Ahn, J. A. Fessler, D. Blatt, A. O. Hero.
     Incremental optimization transfer algorithms: Application to transmission tomography. [PDF] [LINK]
     Proc. IEEE Nuclear Science Symp. Medical Imaging Conf., vol. 5, pp. 2835-2839, 2004. Slides from talk.
  10. S. Ahn, J. A. Fessler, T. E. Nichols, R. A. Koeppe.
      Covariance of kinetic parameter estimators based on time activity curve reconstructions: Preliminary study on 1D dynamic imaging. [PDF] [LINK]
      Proc. IEEE Intl. Symp. Biomedical Imaging, pp. 368-371, 2004. Slides from talk.
  11. S. Ahn, J. A. Fessler.
      Statistical emission image reconstruction for randoms-precorrected PET scans using negative sinogram values. [PDF] [LINK]
      Proc. IEEE Nuclear Science Symp. Medical Imaging Conf., vol. 5, pp. 3062-3066, 2003. Poster.
  12. S. Ahn, J. A. Fessler.
      Globally convergent ordered subsets algorithms: Application to tomography. [PDF] [LINK]
      Proc. IEEE Nuclear Science Symp. Medical Imaging Conf., vol. 2, pp. 1064-1068, 2001. Slides from talk.

• Dissertation
  
  
  1. S. Ahn, Convergent algorithms for statistical image reconstruction in emission tomography, 2004.