Surface and build‐up dose comparison between Elekta 6 MV flattening filter and flattening‐filter‐free beams using an advanced Markus ionization chamber and a solid water‐equivalent phantom

• Published in: Journal of applied clinical medical physics Vol. 21; no. 12; pp. 334 - 339
• Main Authors: Imae, Toshikazu, Takenaka, Shigeharu, Watanabe, Yuichi, Aoki, Atsushi, Matsuda, Kanako, Sasaki, Katsutake, Saegusa, Shigeki, Nawa, Kanabu, Nakagawa, Keiichi, Abe, Osamu
• Format: Journal Article
• Language: English
• Published: United States John Wiley & Sons, Inc 01-12-2020; John Wiley and Sons Inc
• Subjects: a solid water‐equivalent phantom; build‐up; Dosimetry; flattening filter (FF) beam; flattening‐filter‐free (FFF) beam; ionization chamber; Polymethyl methacrylate; Standard deviation; surface dose; Technical Note; Technical Notes; Japan; flattening-filter-free (FFF) beam; flattening filter (FF) beam; a solid water-equivalent phantom; surface dose; build-up; ionization chamber
• ISSN: 1526-9914; 1526-9914
• DOI: 10.1002/acm2.13094

Using a plane‐parallel advanced Markus ionization chamber and a stack of water‐equivalent solid phantom blocks, percentage surface and build‐up doses of Elekta 6 MV flattening filter (FF) and flattening‐filter‐free (FFF) beams were measured as a function of the phantom depth for field sizes ranging from 2 × 2 to 10 × 10 cm2. It was found that the dose difference between the FF and the FFF beams was relatively small. The maximum dose difference between the FF and the FFF beams was 4.4% at a depth of 1 mm for a field size of 2 × 2 cm2. The dose difference was gradually decreased while the field size was increased up to 10 × 10 cm2. The measured data were also compared to published Varian FF and FFF data, suggesting that the percentage surface and build‐up doses as well as the percentage dose difference between FF and FFF beams by our Elekta linac were smaller than those by the Varian linac.