ESTRO 2024 - Abstract Book

S4652

Physics - Optimisation, algorithms and applications for ion beam treatment planning

ESTR0 2024

[3] Eriksson O, Zhang T. Robust automated radiation therapy treatment planning using scenario-specific dose prediction and robust dose mimicking. Med Phys. 2022 Jun 1;49(6):3564–73.

[4] Kouwenberg J, Penninkhof J, Habraken S, Zindler J, Hoogeman M, Heijmen B. Model based patient pre-selection for intensity-modulated proton therapy (IMPT) using automated treatment planning and machine learning. Radiotherapy and Oncology. 2021 May 1;158:224–9.

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Digital Poster

Collimated active spot-scanning IMPT vs VMAT for lung SBRT: Dosimetric and robustness comparison

Luca Trombetta 1 , Valeria Faccenda 2 , Giuseppe Magro 1 , Denis Panizza 2 , Stefania\ Russo 1 , Sofia Paola Bianchi 3,4 , Stefano Arcangeli 3,4 , Elena De Ponti 2,3 , Ester Orlandi 5 , Mario Ciocca 1 1 Fondazione CNAO, Medical Physics Department, Pavia, Italy. 2 Fondazione IRCCS San Gerardo dei Tintori, Medical Physics Department, Monza, Italy. 3 Università di Milano Bicocca, Faculty of Medicine and Surgery, Milano, Italy. 4 Fondazione IRCCS San Gerardo dei Tintori, Radiotherapy Department, Monza, Italy. 5 Fondazione CNAO, Radiotherapy Department, Pavia, Italy

Purpose/Objective:

The study aimed to compare the dosimetric effects of photon volumetric modulated arc therapy (VMAT) and intensity modulated proton therapy (IMPT) on lung stereotactic body radiation therapy (SBRT) plans. Target coverage and OAR sparing were compared along with conformity and gradient indeces. Finally, a robust evaluation was conducted.

Material/Methods:

A set of 20 4DCT DICOM sets of peripherally located lung lesions (CTV volume ranging from 0.4cm3 – 37.4cm3) were contoured on maximum inhale and exhale phases as a standard for gated treatments in both techniques. An internal target volume (ITV) was created as CTV convolution using the two closest contiguous phases. The respiratory gated VMAT plans were optimized using the maximum inhale phase, on a PTV 3 mm isotropically expanded from the ITV. IMPT plans were instead robustly optimized on CTV contoured on maximum exhale phase, by modeling systematic isotropic shifts of 3mm, a 5% density uncertainty, and accounting for the two closest concurrent respiratory phase anatomies. VMAT plans were optimized with Monaco TPS and Versa HD FFF linac (Elekta, Sweden), using two partial and coplanar arcs. IMPT plans were optimized on RayStation TPS (Raysearch, Sweden) using an active spot-scanning ProBeat Proton Beam Therapy delivery system (Hitachi, Japan) equipped with a rotating gantry and a patient specific collimator opened with an isotropic 4mm margin from ITV. Two up to four static coplanar fields were adopted. Prescription dose ranged from 48 to 60 Gy(Relative Biologically Effectiveness) delivered in 4 up to 8 fractions, depending on lesion anatomy. Comparison analysis included CTV coverage, chest wall, ribs, and lungs-less-ITV dose contraints, conformity index (CI), gradient index (GI). A robust evaluation of CTV coverage was achieved by creating various scenarios with 3 mm shifts and 3.5% density uncertainties. In order to determine statistical significance of the observed differences, the Wilcoxon-Mann-Whitney test (alpha=0.05) was performed.