Monte Carlo simulations of stray neutron radiation exposures in proton therapy

• Published in: Journal of nuclear materials Vol. 361; no. 2-3; pp. 289 - 297
• Main Authors: Zheng, Yuanshui, Newhauser, Wayne, Fontenot, Jonas, Koch, Nicholas, Mohan, Radhe
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Amsterdam Elsevier B.V 15-04-2007; Elsevier
• Subjects: Biological and medical sciences; Investigative techniques, diagnostic techniques (general aspects); Medical sciences; Radionuclide investigations; 87.53.Pb,Qc; T0100; P1400; 87.56.−v; D0600; N0100; 87.50.−a; Monte Carlo method; Absorbed dose; Proton beam; Simulation; Patient; Radiation exposure(person); Dose equivalent; Neutron therapy; Radiotherapy
• ISSN: 0022-3115; 1873-4820
• DOI: 10.1016/j.jnucmat.2006.12.016

Proton radiotherapy patients receive unwanted stray neutron radiation generated in the treatment apparatus. The literature on this neutron radiation is sparse and disparate and pertains mainly to unique or antiquated systems. The present work reports on neutron dose equivalent per therapeutic absorbed dose (H/D) in a contemporary proton therapy system. We applied the Monte Carlo method to predict neutron exposure as a function of treatment field size and location in the treatment room. For a 250-MeV proton beam, H/D values at isocenter increased from 13 to 20mSvGy−1 as the collimating aperture was decreased from 18×18 to 0×0cm2. H/D values generally decreased with distance from isocenter (20mSvGy−1 at isocenter versus 0.9mSvGy−1 at a distance of 150cm). Neutron spectral fluence calculations revealed that >50% of the dose equivalent at all locations considered was from neutrons >10MeV.