ESTRO 2024 - Abstract Book

S5945

RTT - Treatment planning, OAR and target definitions

ESTRO 2024

Keywords: Breast cancer, radiotherapy, VMAT

References:

1. P. Virtanen, R. Gommers, T.E. Oliphant, et al. SciPy 1.0: Fundamental Algorithms for Scientific Computing in Python. Nature Methods 2020; 17(3): 261-272.

2. Badakhshi H, Kaul D, Nadobny J, et al. Image-guided volumetric modulated arc therapy for breast cancer: a feasibility study and plan comparison with three-dimensional conformal and intensity-modulated radiotherapy. Br J Radiol. 2013; 86(1032): 20130515. doi: 10.1259/bjr.20130515.

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Dose accuracy between Monte Carlo and Accuros® in lung motion case for CyberKnife® or TrueBeam®.

Pierre-François CLERY, Anas MACHKOUR, Stephane ESTIVALET, Julien VAUTIER

Centre de Cancérologie de la Sarthe, Sarthe, Le Mans, France

Purpose/Objective:

SBRT lung treatment need to have a good confidence for GTV positioning, GTV motion and great dose accuracy[1]. A high-level algorithm is recommended for treatment of patients with two type of LINAC, Accuray® CyberKnife®(Accuray, Sunnyvale, CA, USA) and Varian Truebeam ®(Varian Medical System, Palo-Alto, CA, USA) [2]. Comparison between respectively Monte Carlo in Precision®(Accuray) and Eclipse Accuros®(Varian) seem to be necessary to apply the same prescription [3]. Verifications are based on measurements with simple and anthropomorphic phantoms with air chamber and dosimetric films.

Material/Methods:

With a pinpoint (PTW, Freiburg, Germany) chamber in a simple homogenous phantom Bblue®(Standard Imaging, Middleton, WI, USA) we compared dose calculation and measurement for two types of beam geometry per LINAC. For the C-arm Truebeam® : a fixed squared anterior 10x10 cm2 field and cyclotherapy beam. For the CyberKnife® : 6cm iris collimator at path start and full body path for multiples beams. With the same geometry, we added lung equivalent medium to introduce heterogeneity on the phantom and we measure again. We calculated VMAT plan on the 4D CIRS® phantom (Sun Nuclear, Melbourne, FL, USA) and a Xsight-Lung-Treatment® (XLT) plan for the CyberKnife® to increase plan complexity. We measured without motion on the TrueBeam with gafchromics EBT® films (Ashland, Wilmington, DE).

To move on to a more realistic case we realized the dosimetric optimization on real patient cases. We performed patients QA on the anthropomorphic CIRS 4D phantom with motion. 4D CT scan and a near exhale phase CT scan