Optimization of a general‐purpose, actively scanned proton beamline for ocular treatments: Geant4 simulations

Abstract

The Italian National Center for Hadrontherapy (CNAO, Centro Nazionale di Adroterapia Oncologica), a synchrotron‐based hospital facility, started the treatment of patients within selected clinical trials in late 2011 and 2012 with actively scanned proton and carbon ion beams, respectively. The activation of a new clinical protocol for the irradiation of uveal melanoma using the existing general‐purpose proton beamline is foreseen for late 2014. Beam characteristics and patient treatment setup need to be tuned to meet the specific requirements for such a type of treatment technique. The aim of this study is to optimize the CNAO transport beamline by adding passive components and minimizing air gap to achieve the optimal conditions for ocular tumor irradiation. The CNAO setup with the active and passive components along the transport beamline, as well as a human eye‐modeled detector also including a realistic target volume, were simulated using the Monte Carlo Geant4 toolkit. The strong reduction of the air gap between the nozzle and patient skin, as well as the insertion of a range shifter plus a patient‐specific brass collimator at a short distance from the eye, were found to be effective tools to be implemented. In perspective, this simulation toolkit could also be used as a benchmark for future developments and testing purposes on commercial treatment planning systems.PACS numbers: 21.30Fe, 24.10.Lx, 29.20.dk, 29.27.Eg, 29.85.Fj

Characterization of the HollandPTC proton therapy beamline dedicated to uveal melanoma treatment and an interinstitutional comparison

“… 57 Another alternative could be the use of synchrotron‐based facilities. 15 , 58 , 59 , 60 Ciocca et al 15 reported that a constant pulsed proton beam with energy set to around 70 MeV without degrading the beam has led to LPs between 1.40 and 1.70 mm for various geometry‐shaped FSs between 6 and 25 mm. However, the reported treatment time was up to 3 min.…”

“…Even a small gain has a clinical impact, as the LP is still the primary parameter to spare organs‐at‐risk 57 . Another alternative could be the use of synchrotron‐based facilities 15,58‐60 . Ciocca et al 15 reported that a constant pulsed proton beam with energy set to around 70 MeV without degrading the beam has led to LPs between 1.40 and 1.70 mm for various geometry‐shaped FSs between 6 and 25 mm.…”

Clinical commissioning of intensity‐modulated proton therapy systems: Report of AAPM Task Group 185

“…The use of scanning systems for ocular applications is a developing application, 3 as are scanned proton mini-beams, 4 and both are outside the scope of this report. Also, the The non-attenuating opening in a collimator, shaped irregularly according to the shape of the target, that allows radiation to reach a target Collimator Beam A group of particles or rays traveling in the same direction in parallel or diverging from a point Beam energy…”

“…The use of scanning systems for ocular applications is a developing application, 3 as are scanned proton mini‐beams, 4 and both are outside the scope of this report. Also, the radiobiological aspects of proton therapy are covered by the dedicated TG‐256 5 …”

Design and commissioning of the non‐dedicated scanning proton beamline for ocular treatment at the synchrotron‐based CNAO facility

“…A preliminary study based on Monte Carlo (MC) simulations showed that the starting strategy of minimizing air gaps among patient skin (ocular globe), range shifter (RS) and nozzle, which is commonly valid for conventional proton therapy, lead to very poor results, in terms of unacceptable lateral beam penumbra width, even in the presence of a field‐specific ocular collimator . That finding led us to investigate completely different approaches, as reported in this work.…”