Simulation of organ-specific patient effective dose due to secondary neutrons in proton radiation treatment

Abstract

Cancer patients undergoing radiation treatment are exposed to high doses to the target (tumour), intermediate doses to adjacent tissues and low doses from scattered radiation to all parts of the body. In the case of proton therapy, secondary neutrons generated in the accelerator head and inside the patient reach many areas in the patient body. Due to the improved efficacy of management of cancer patients, the number of long term survivors post-radiation treatment is increasing substantially. This results in concern about the risk of radiation-induced cancer appearing at late post-treatment times. This paper presents a case study to determine the effective dose from secondary neutrons in patients undergoing proton treatment. A whole-body patient model, VIP-Man, was employed as the patient model. The geometry dataset generated from studies made on VIP-Man was implemented into the GEANT4 Monte Carlo code. Two proton treatment plans for tumours in the lung and paranasal sinus were simulated. The organ doses and ICRP-60 radiation and tissue weighting factors were used to calculate the effective dose. Results show whole body effective doses for the two proton plans of 0.162 Sv and 0.0266 Sv, respectively, to which the major contributor is due to neutrons from the proton treatment nozzle. There is a substantial difference among organs depending on the treatment site.

Late radiation toxicity in Hodgkin lymphoma patients: proton therapy's potential

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Monte Carlo simulation of a proton therapy beamline for intracranial treatments

“…Monte Carlo methods also turn out to be powerful in complex situations where measurements are difficult to achieve. They also have many other applications in proton therapy: verification of shielding design efficiency (Newhauser et al, 2002), assessment of secondary doses received by proton therapy patients (Agosteo et al, 1998;Jiang et al, 2005;Zacharatou Jarlskog and Paganetti 2008) and neutron fluence and ambient dose equivalent calculations (Zheng et al, 2008;Perez-Andujar et al, 2009). It should be noted that each Monte Carlo model must first be carefully validated with experimental data in order to verify the accuracy of results.…”