Secondary neutron doses received by paediatric patients during intracranial proton therapy treatments

• Published in: Journal of radiological protection Vol. 34; no. 2; pp. 279 - 296
• Main Authors: Sayah, R, Farah, J, Donadille, L, Hérault, J, Delacroix, S, De Marzi, L, De Oliveira, A, Vabre, I, Stichelbaut, F, Lee, C, Bolch, W E, Clairand, I
• Format: Journal Article
• Language: English
• Published: Bristol IOP Publishing 01.06.2014; Institute of Physics
• Subjects: Absorption, Radiation; Adolescent; Adult; Biological and medical sciences; Biological effects of radiation; Brain Neoplasms - physiopathology; Brain Neoplasms - radiotherapy; Child; Child, Preschool; Computer Simulation; Female; Fundamental and applied biological sciences. Psychology; Humans; Infant; intracranial treatments; Life Sciences; Linear Energy Transfer; Male; Models, Biological; Neutrons; Organ Specificity; passive scattering; pediatric and adult patients; proton therapy; Proton Therapy - methods; Radiation Dosage; Radioprotection; Radiotherapy Dosage; Scattering, Radiation; stray neutron doses; Tissues, organs and organisms biophysics; Whole-Body Counting - methods; Young Adult; Human; Intracranial; Secondary; Treatment; Hadrontherapy; Neutrons; Proton therapy; Radiotherapy; Dose; Child; Radioprotection
• ISSN: 0952-4746; 1361-6498
• DOI: 10.1088/0952-4746/34/2/279

This paper's goal is to assess secondary neutron doses received by paediatric patients treated for intracranial tumours using a 178 MeV proton beam. The MCNPX Monte Carlo model of the proton therapy facility, previously validated through experimental measurements for both proton and neutron dosimetry, was used. First, absorbed dose was calculated for organs located outside the clinical target volume using a series of hybrid computational phantoms for different ages and considering a realistic treatment plan. In general, secondary neutron dose was found to decrease as the distance to the treatment field increases and as the patient age increases. In addition, secondary neutron doses were studied as a function of the beam incidence. Next, neutron equivalent dose was assessed using organ-specific energy-dependent radiation weighting factors determined from Monte Carlo simulations of neutron spectra at each organ. The equivalent dose was found to reach a maximum value of 155 mSv at the level of the breasts for a delivery of 49 proton Gy to an intracranial tumour of a one-year-old female patient. Finally, a thorough comparison of the calculation results with published data demonstrated the dependence of neutron dose on the treatment configuration and proved the need for facility-specific and treatment-dependent neutron dose calculations.