Relative Biologic Effectiveness (RBE) of 50 kV X-rays measured in a phantom for intraoperative tumor-bed irradiation

• Verfasst von: Liu, Qi [VerfasserIn]
• Verfasst von: Schneider, Frank [VerfasserIn]
• Verfasst von: Ma, Lin [VerfasserIn]
• Verfasst von: Wenz, Frederik [VerfasserIn]
• Verfasst von: Herskind, Carsten [VerfasserIn]
• Titel: Relative Biologic Effectiveness (RBE) of 50 kV X-rays measured in a phantom for intraoperative tumor-bed irradiation
• Verf.angabe: Qi Liu, Frank Schneider, Lin Ma, Frederik Wenz, and Carsten Herskind
• E-Jahr: 2013
• Jahr: 15 March 2013
• Umfang: 7 S.
• Fussnoten: Available online: 14 September 2012 ; Gesehen am 21.11.2018
• Titel Quelle: Enthalten in: International journal of radiation oncology, biology, physics
• Ort Quelle: Amsterdam [u.a.] : Elsevier Science, 1975
• Jahr Quelle: 2013
• Band/Heft Quelle: 85(2013), 4, Seite 1127-1133
• ISSN Quelle: 1879-355X
• DOI: doi:10.1016/j.ijrobp.2012.08.005
• Datenträger: Online-Ressource
• Sprache: eng
• Bibliogr. Hinweis: Erscheint auch als : Druck-Ausgabe: Relative Biologic Effectiveness (RBE) of 50 kV X-rays measured in a phantom for intraoperative tumor-bed irradiation. - 2013
• K10plus-PPN: 1583929886

Abstract

Purpose - Intraoperative radiation therapy (IORT) with low-energy x-rays is used to treat the tumor bed during breast-conserving surgery. The purpose was to determine the relative biologic effectiveness (RBE) of 50-kV x-rays for inactivation of cells irradiated in a tumor-bed phantom. - Methods and Materials - The RBE was determined for clonogenic inactivation of human tumor and normal cells (MCF7, human umbilical vein endothelial cells, normal skin fibroblasts), and hamster V79 cells. The 50-kV x-rays from the Intrabeam machine (Carl Zeiss Surgical) with a spherical 4-cm applicator were used. Cells were irradiated in a water-equivalent phantom at defined distances (8.1-22.9 mm) from the applicator surface. The 50-kV x-rays from a surface therapy machine (Dermopan, Siemens) were included for comparison; 6-MV x-rays were used as reference radiation. - Results - At 8.1-mm depth in the phantom (dose rate 15.1 Gy/h), mean RBE values of 50-kV x-rays from Intrabeam were 1.26 to 1.42 for the 4 cell types at doses yielding surviving fractions in the range of 0.01 to 0.5. Confidence intervals were in the range of 1.2 and 1.5. Similar RBE values were found for 50-kV x-rays from Dermopan for V79 (1.30, CI 1.25-1.36, P=.74) and GS4 (1.42, CI 1.30-1.54, P=.67). No significant dependence of RBE on dose was found for Intrabeam, but RBE decreased at a larger distance (12.7 mm; 9.8 Gy/h). - Conclusions - An increased clinically relevant RBE was found for cell irradiation with Intrabeam at depths in the tumor bed targeted by IORT. The reduced RBE values at larger distances may be related to increased repair of sublethal damage during protracted irradiation or to hardening of the photon beam energy.