A neutron track etch detector for electron linear accelerators in radiotherapy

Abstract

BackgroundElectron linear accelerators in medical radiotherapy have replaced cobalt and caesium sources of radiation. However, medical accelerators with photon energies over 10 MeV generate undesired fast neutron contamination in a therapeutic X-ray photon beam. Photons with energies above 10 MeV can interact with the atomic nucleus of a high-Z material, of which the target and the head of an accelerator consist, and lead to the neutron ejection.Results and conclusions.Our neutron dosimeter, composed of the LR-115 track etch detector and boron foil BN-1 converter, was calibrated on thermal neutrons generated in the nuclear reactor of the Josef Stefan Institute (Slovenia), and applied to dosimetry of undesirable neutrons in photon radiotherapy by the linear accelerator 15 MV Siemens Mevatron. Having considered a high dependence of a cross-section between neutron and boron on neutron energy, and broad neutron spectrum in a photon beam, as well as outside the entrance door to maze of the Mevatron, we developed a method for determining the effective neutron detector response. A neutron dose rate in the photon beam was measured to be 1.96 Sv/h. Outside the Mevatron room the neutron dose rate was 0.62 μSv/h. PACS: 87.52. Ga; 87.53.St; 29.40.Wk.

Study of Thermal Neutron Flux and Generated Energy from Linac using CR-39 Detector in Liquid Medium

“…Perkembangan perangkat terapi di bidang radiologi dan kedokteran mengalami kemajuan, salah satunya adalah Linac (linier accelarator) yang biasa digunakan dalam terapi penyakit kanker [1]. Keuntungan perangkat terapi Linac yaitu tidak menggunakan sumber radioaktif secara langsung sehingga aman saat penggunaan dan dijadikan alternatif pengganti alat terapi radiasi kobalt dan cesium [2]. Tetapi penggunaan Linac tidak terlepas dari keberadaan neutron, terutama jika Linac dioperasikan diatas 8 MV.…”

Study of Thermal Neutron Flux and Generated Energy from Linac using CR-39 Detector in Liquid Medium

“…Keuntungan perangkat terapi Linac yaitu tidak menggunakan sumber radioaktif secara langsung sehingga aman saat penggunaan dan dijadikan alternatif pengganti alat terapi radiasi kobalt dan cesium [2]. Tetapi penggunaan Linac tidak terlepas dari keberadaan neutron, terutama jika Linac dioperasikan diatas 8 MV.…”

The influence of shielding reinforcement in a vault with limited dimensions on the neutron dose equivalent in vicinity of medical electron linear accelerator

“…In these beams, fast neutrons are generated, which results in undesired contamination of the therapeutic beam. [1][2][3][4][5][6] Neutr on contamination in high-energy RT implies an increase of secondary radiation-induced cancer risk. 7 It is also well known that an essential requirement for successful radiation therapy is that the discrepancies between dose distributions calculated at the treatment planning stage and those delivered to the patient are minimized.…”

“…Measurements of the neutron flux and dose equivalent that were done in Osijek University Hospital are already published. 2 Measurements were done during all stages of installation, namely before and after lead shielding was added to the walls. It was done using solid state nuclear track detector (SSNTD) LR115.…”

“…Neutron dose equivalents for patients and staff were assessed and compared to the results presented before. 2 Additionally, we investigated the origin of the photoneutrons to show if the steel panels added to the vault walls could be significant sources of photoneutrons. The MC simulations were done for different orientations of the gantry and different points around the accelerator and vault in order to show whether these panels increase total radiation dose to patients and staff.…”