Shepp, Larry A2023-05-232023-05-2319862016-07-27https://repository.upenn.edu/handle/20.500.14332/47785I survey the present status of three subfields of reconstruction tomography, X-ray CT, emission CT, and magnetic resonance CT, and mention some new results and insights, as well as open problems. This is for my Frontier in Imaging Science lecture at the IEEE Nuclear Science International Workshop on Physics and Engineering of Computerized Multidimensional Imaging and Processing, April 2-4, 1986, Irvine, CA.Copyright 1986 Society of Photo Optical Instrumentation Engineers. One print or electronic copy may be made for personal use only. Systematic reproduction and distribution, duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper are prohibited.Computer SciencesStatistics and ProbabilityPresentation