title: Simple empirical formula for predicting range variation of central-axis parameters in small electron fields.
abstract: The depth of central-axis percent dose Rx (except R100) and practical range, Rp, for small field electron beams can be calculated by the proposed empirical formula: Rx = Rxo x [1 - (1 - r/Rpo)m], where Rxo and Rpo are the broad beam percentage dose depth and practical range respectively; r is the small field cutout side when it is less than the maximum lateral scatter equivalent range, and m is the exponent term relative to the decreasing curvature. Five electron beams from a Varian CL-2100CD linear accelerator were used to verify this formula. The difference between measured and calculated depth dose range is within +/- 1 mm when cutout side reduced to 2 x 2 cm2. This formula offers a simple and time-saving method to quickly determine the useful treatment percentage dose depth of small field electron beams.
authors.affiliation: School of Technology for Medical Sciences, College of Health Science, Kaohsiung Medical University, No. 100, Shih-Chuan 1st Road, Kaohsiung, Taiwan. inmihw@cc.kmu.edu.tw
authors.forename: I M
authors.initials: IM
authors.lastname: Hwang
authors.forename: K S
authors.initials: KS
authors.lastname: Chuang
mesh_terms: D004583:Electrons; D006801:Humans; D008433:Mathematics; D011874:Radiometry / Q000379:methods*; D011879:Radiotherapy Dosage