20.500.12556/DiRROS-15460 A novel approach for the definition of small-field sizes using the concept of superellipse In radiotherapy, field sizes are defined in terms of the dimensions of the irradiation area. However, geometric square fields result in irradiation areas with rounded corners, which become almost elliptical for small fields. Superellipses are a family of curves encompassing shapes lying between ellipses and rectangles. The purpose of this work was to analyze the advantages and disadvantages of a novel approach that describes small-field sizes with superellipses. Square fields with nominal side lengths ranging from 0.5 to 10 cm were irradiated with two different linacs using 6 and 10 MV photon beams with and without flattening filters. Field size dimensions and output factors were measured by employing radiochromic films and the Radiochromic.com software. An alternative definition of equivalent square small-field size based on the superellipse (Sse) was introduced. The degree n of the superellipse for 10 cm nominal fields measured between 14.8 % 1.0 to 27.7 % 1.9. However, it decreased with the field size, down to between 2.26 % 0.10 and 2.64 % 0.15 for 0.5 cm nominal side lengths. A relation between the degree n and the equivalent square small-field size (Sclin) as defined by Cranmer-Sargison et al. [%A methodological approach to reporting corrected small field relative outputs,% Radiotherapy and Oncology 109, 350%355 (2013)] was found. For nominal side lengths of 10 cm, Sse was between 0.34 % 0.04% and 0.10 % 0.01% smaller than Sclin, while for 0.5 cm nominal side length Sse was between 9.5 % 0.6% and 7.4 % 0.7% smaller than Sclin. There was no significant difference in the goodness of the regression between using Sse or Sclin to fit field output factors with the function proposed by Sauer and Wilbert. Small fields were found to be more accurately characterized with superellipses. The advantages and disadvantages of describing field sizes with superellipses were examined. Field output factors can be derived with equivalent square small-field sizes based on the superellipse approach. superellipsa small fields dosimetry radiotherapy superelipsa mala polja dozimetrija radioterapija true false true Angleški jezik Slovenski jezik by Authors Neznano 2022-09-07 03:37:50 2022-09-07 08:05:12 2022-09-08 03:36:07 0000-00-00 00:00:00 2021 0 0 str. 109775-1-109775-6 Vol. 189 2021 0000-00-00 Zaloznikova Objavljeno apc 0000-00-00 0000-00-00 2021-10-07 615.82/.84 0969-806X 10.1016/j.radphyschem.2021.109775 77903363 http://dx.doi.org/10.1016/j.radphyschem.2021.109775 1 ecfb8702-2e3c-11ed-bea5-001a4af901a5 https://dirros.openscience.si/Dokument.php?lang=slv&id=20444 RAZ_Mendez_Carot_Ignasi_2021.pdf RAZ_Mendez_Carot_Ignasi_2021.pdf 1 7BE1C9B6104618C02FD283643D47B9CB 59c4ae89826245aee80cddd2672856ea56e36c89f8b16a8b655b4d31a8626988 516b75cc-2e62-11ed-bea5-001a4af901a5 https://dirros.openscience.si/Dokument.php?lang=slv&id=20447 Onkološki inštitut Ljubljana 0 0 0