A patient immobilization device for prone breast radiotherapy: Dosimetric effects and inclusion in the treatment planning system

被引：12

作者：

De Puysseleyr, A. ^{[1
]}

De Neve, W. ^{[1
]}

De Wagter, C. ^{[1
]}

机构：

[1] Univ Ghent, Dept Radiat Oncol & Expt Canc Res, B-9000 Ghent, Belgium

来源：

PHYSICA MEDICA-EUROPEAN JOURNAL OF MEDICAL PHYSICS | 2016年 / 32卷 / 06期

关键词：

Radiotherapy; Patient positioning device; Treatment planning system; Build-up dose; CARBON-FIBER COUCH; RANDOMIZED-TRIAL; CANCER; WHOLE; IMRT;

D O I：

10.1016/j.ejmp.2016.04.013

中图分类号：

R8 [特种医学]; R445 [影像诊断学];

学科分类号：

1002 ; 100207 ; 1009 ;

摘要：

Purpose: To assess the dosimetric impact of a patient positioning device for prone breast radiotherapy and assess the accuracy of a treatment planning system (TPS) in predicting this impact. Methods: Beam attenuation and build-up dose perturbations, quantified by ionization chamber and radiochromic film dosimetry, were evaluated for 3 components of the patient positioning device: the carbon fiber baseplate, the support cushions and the support wedge for the contralateral breast. Dose calculations were performed using the XVMC dose engine implemented in the Monaco TPS. All components were included during planning CT acquisition. Results: Beam attenuation amounted to 7.57% (6 MV) and 5.33% (15 MV) for beams obliquely intersecting the couchtop-baseplate combination. Beams traversing large sections of the support wedge were attenuated by 12.28% (6 MV) and 9.37% (15 MV). For the support cushion foam, beam attenuation remained limited to 0.11% (6 MV) and 0.08% (15 MV) per centimeter thickness. A substantial loss of dose buildup was detected when irradiating through any of the investigated components. TPS dose calculations accurately predicted beam attenuation by the baseplate and support wedge. A manual density overwrite was needed to model attenuation by the support cushion foam. TPS dose calculations in build-up regions differed considerably from measurements for both open beams and beams traversing the device components. Conclusions: Irradiating through the components of the positioning device resulted in a considerable degradation of skin sparing. Inclusion of the device components in the treatment planning CT allowed to accurately model the most important attenuation effect, but failed to accurately predict build-up doses. (C) 2016 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.

引用

页码：758 / 766

页数：9

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