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Indiana University Bloomington

Susan B. Klein

Susan B. Klein Assoc. Director, Medical Physics Program
Biophysics and Radiation Biology

B.S., Sonoma State University, Biophysics, 1980
Ph.D., University of California at Berkeley, Biophysics, 1986
Postdoctoral Positions:
University of Michigan, Biophysics Division
University of Michigan Medical School, Department of Radiation Oncology
University of Michigan Medical School, Department of Dermatology

Office: Swain West 306
Phone: (812)855-9687
Email: sbklein at

Group Webpage

Radiation biophysics studies the interactions between ionizing radiation and the complex biological responses to that insult. Particularly interesting is the physics of particle radiation because of the Bragg peak phenomenon that causes charged particles to deposit relatively large amounts of energy within a relatively small biological volumes. This phenomenon is called high linear energy transfer or high LET. High LET radiation causes distinct types of damage within the DNA, cell and tissue. Radiation sensitive genetic mutants can be used to examine the differences in “repairosomes”, large complexes of enzymes that resolve DNA and chromosomal damage, that respond to high LET damage compared with damage caused by low LET particles, such as high energy electrons produced by interactions between biological molecules and x-rays. High LET particles, such as protons and heavier cosmic ray particles, are a particular concern for space travelers. Mission critical considerations in space and on planets such as Mars that do not have a protective magnetosphere depend on physiological responses to unpredictable levels of high LET particle radiation. Because low gravity affects human physiology in a manner similar to excessive radiation, astronauts are more susceptible to radiation during specific periods of adjustment to changing gravitational acceleration. This risk parameter is an important consideration for NASA. Particle radiation biophysics is fundamental to understanding the mechanisms involved in successful cancer radiation therapy and so research in this area is critical to the medical advancement of both x-ray and particle treatments. Over half of all cancer patients receive x-ray radiation therapy. In addition, there are 34 particle therapy facilities in the United States and 110 world-wide. Translational research in radiation biophysics provides opportunities at every level from the laboratory bench to the clinical environment.

Selected Publications

  • Klein, S.B.  SEM and x‑ray microanalysis of cellular differentiation in sea urchin embryos: a frozen hydrated study, Ph.D. Dissertation, University of California, Lawrence Berkeley Laboratory Publication, LBL‑21128 (1985).
  • Klein, S.B., Fisher, G.J., Jensen, T.C., Mendelsohn, J., Voorhees, J.J., Elder, J.T. Regulation of TGF‑a expression in human keratinocytes: PKC‑dependent and ‑independent pathways, J. Cell. Phys., 151:326‑336 (1992).
  • Klein, S.B., Yeivin, A., Becker, G., Taylor, M.W.  IDO mutants cross‑resistant to type I interferon retain p91‑dependent gene induction, J. Interferon Res., 14:333‑341 (1994).
  • Zhang, J‑F., Hu, C., Geng, Y., Selm, J., Klein, S.B., Orazi, A., Taylor, M.W.  Treatment of a human breast cancer xenograft with an adenovirus vector containing an interferon gene results in rapid regression due to viral oncolysis and gene therapy.  Proc. Natl. Acad. Sci. USA, 93:4513‑4518 (1996).
  • Dunham, W.R., Sands, R.H., Klein, S.B., Duell, E.A., Rhodes, L.M., Marcelo, C.L.  EPR measurements showing that plasma membrane viscosity can vary from 30 to 100 cP in human epidermal cell strains. Spectrochimica Acta, Part A, 52:1357‑1368 (1996).
  • Jones, A.Z., Bloch, C.D., Hall, E.R., Hashemian, R., Klein, S.B., Murray, K.M. Foster, C.C.  Comparison of Indiana University Cyclotron Facility Faraday cup proton dosimetry with radiochromic films, a calorimeter, and a calibrated ion chamber. IEEE Transactions on Nuclear Science, 46:6, 1762-1765 (1999).
  • M. A. Miller, S. B. Klein, K. A. Slack, P. I. Rogers, J. L. Solomon, A. P. Mendel, D. Hou, S. C. A. M. Bekkers and K. L. March.  Fast Organ-Motion Gated Dose Delivery to the Myocardium, Particles, 28:3-4 (2001).
  • Ciulla T. A., Danis R. P., Klein S. B., Malinovsky V. E., Soni P. S., Pratt L. M., Pugh N. O., Morphis J. G., Bloch C., Cameron J.  Proton therapy for exudative age-related macular degeneration: a randomized, sham-controlled clinical trial. American Journal of Ophthalmology. 134:905-6 (2002)
  • Klein, S. B. Status of the Proton Therapy Project at IUCF and the Midwest Proton Radiotherapy Institute. Cyclotrons and Their Applications, 680:1081 (2003).
  • Britten, R.A., Nazaryan, V., Davis, L.K., Klein, S.B., Nichiporov, D., Mendonca, M.S., Wolanski, M., Nie, X., George, J, Keppel, C. Variations in the RBE for cell killing along the depth dose profile of a modulated proton therapy beam. Radiat Res. 179:21-8 (2013).