Development of a Beam Source Modeling Technique for a Flattening Filter Free (FFF) Beam. - Woong Cho; Jeong-Hoon Park; Won-Gyun Jung; Tae-Suk Suh; Kayla N. Kielar; Ed Mok; Ruijiang Li; Lei Xing 001 (ICMLA (2), 2011)