Characterisation of neutron fields around high-energy x-ray radiotherapy machines

Abstract

Photoneutron spectra around the treatment bed of a Varian Clinac 2100C machine were measured using a Bonner sphere spectrometer. To overcome problems with pulse pile-up and detection of non-neutron-induced events, the active detector of thermal neutrons normally used at the centre of the spheres was replaced by a sandwich of four CR-39 track detectors interleaved with 10B radiators. Track densities measured for the CR-39 detectors in Bonner spheres were used for the unfolding of neutron spectra. Neutron fluence and ambient dose equivalent for the whole energy range and partial energy intervals were derived from the neutron spectra.

Photoneutron intensity variation with field size around radiotherapy linear accelerator 18-MeV X-ray beam

“…NTDs were used to study depth dose equivalent and effective energies of photoneutrons generated by 6-18 MeV X-ray beams for radiotherapy (d 'Errico et al, 2001). Characterization of neutron fields around high energy X-ray radiotherapy machines was carried out using CR-39 etched-track detectors in Bonner Spheres (Kralik and Turek, 2004). Neutron dose measurements from prostheses material during radiotherapy with protons and photons were performed using etched track detectors (Schneider et al, 2004).…”

Photoneutron Flux Measurement via Neutron Activation Analysis in a Radiotherapy Bunker with an 18 MV Linear Accelerator

“…To calculate the dose of the occurring neutrons, characteristics of neutrons in the therapy room (flux, distribution, etc.) must be known [12].…”

Application of recombination chambers for determination of neutron ambient dose equivalent at the door to the maze of linear accelerator vault

“…This concerns practically all the accelerators operating at maximum photon energy of 15 MeV or higher. The photoneutron energy spectrum has a peak around 1 MeV, however, after the transmission through the accelerator head, neutrons have a distribution similar to those of the heavy shielded fission source [3,4].…”