1. Chief Medical Physicist and RSO Tri-State Regional Cancer Center, Radiation Oncology Department, 706 23rd Street, Ashland, KY 41101;
2. Regulation Directive Medical Physics®, 3312 Forestdale Court, Flatwoods, KY 41139 e-mail:
3. The Phantom Laboratory, P.O. Box 511, Salem, NY 12865 e-mail: