[1] E Carolina Univ, Dept Biol, Thomas Harriot Coll Arts & Sci, Greenville, NC 27858 USA
[2] Johns Hopkins Univ, Sch Med, Sidney Kimmel Comprehens Canc Ctr, Dept Radiat Oncol & Mol Radiat Sci, Baltimore, MD 21231 USA
[3] Vanderbilt Univ, Vanderbilt Ingram Canc Ctr, Sch Med, Dept Radiat Oncol, Nashville, TN 37232 USA
[4] Univ Alabama Birmingham, Hazelrig Salter Radiat Oncol Ctr, Dept Radiat Oncol, Birmingham, AL 35294 USA
[5] Natl Tech Univ Athens, Dept Phys, GR-15773 Zografos, Greece