Safe Proton Radiotherapy for Patients with Metallic Spine Stabilization System

K. Kisielewicza, E. Góraa, T. Skóraa, B. Kiełtykab, M. Garbaczc, M. Rydygierc, D. Krzempekc, R. Kopećc aThe Maria Sklodowska - Curie National Research Institute of Oncology in Kraków, Garncarska 11, 31-115 Kraków bUniversity Hospital in Kraków, Jakubowskiego 2, 30-688 Kraków cInstitute of Nuclear Physics PAN, Cyclotron Centre Bronowice, Radzikowskiego 152, 31-342 Kraków

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The brain and the skull base tumors are the most common cases treated in Kraków with proton therapy. Due to the need to deliver a high dose of ionizing radiation (70-74 Gy RBE) and the close presence of critical structures such as the brainstem, optic chiasm, and optic nerves, the use of a proton beam creates better opportunities for dose escalation to the target volume compared to photon radiotherapy. A problem in planning such treatment is the presence of metal stabilizers on the beam path in about 40% of patients, which increases the uncertainty of the planned dose delivery. Acquisition of the computed tomography layers, necessary for treatment planning, was performed with the Siemens Somatom Definition AS apparatus, equipped with the iMAR software, an optimized iterative algorithm for reducing metal artifacts. Then, a dedicated calibration curve for the Varian Eclipse treatment planning system (Hounsfield Units to relative proton stopping power conversion) was prepared. The geometry of the beams is also optimized with respect to the metal element and the critical organs. The presented procedure allowed for the safe proton radiotherapy treatment using a scanning beam in over 50 patients with metallic stabilizers, which was additionally confirmed by Monte Carlo simulations using the FRED tool.

DOI:10.12693/APhysPolA.142.351 topics: proton radiotherapy, skull base tumors, spine stabilization, metallic implants