Neutron spectrometry and determination of neutron ambient doses in radiotherapy treatments under different exposure conditions

Domingo, C.; García-Fusté, M.J.; Morales, E.; Amgarou, K.; Terrón, José A.; Roselló, J.; Brualla, L.; Núñez, Luis A.; Colmenares, R.; Gómez, F.; Hartmann, Günther H.; Sánchez‐Doblado, F.; Fernández, F.

doi:10.1007/978-3-642-03902-7_149

Cited by 4 publications

(1 citation statement)

References 9 publications

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“…However, the results obtained were contrary to expectations. Two possible reasons account for this: firstly, delay in gantry rotations between fields interrupted the long irradiation time, and therefore, fewer neutrons were produced, reducing material activation 34,37) . Also, the time delay allowed for decay of radioisotopes with short half-lives 4) .…”

Section: Neutron Production and Activationmentioning

confidence: 99%

Evaluation of Optimum Room Entry Times for Radiation Therapists after High Energy Whole Pelvic Photon Treatments

White

Chan

et al. 2012

Journal of Occupational Health

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High energy photon beams (greater than 10 MV) are routinely employed in clinical use for treatment of deep-seated tumors 1,2) . However, they induce undesirable photonuclear and electronuclear reactions 3) that produce neutrons and radioisotopes. Neutron production increases with photon energy, and the induced radioactivity depends on the neutron radiation level 3,4) . This phenomenon induces potential exposure for radiation therapists due to neutron, gamma and beta radiations emitted from decay of activation products 1, 3) . As occupational doses are of concern, undesirable photoneutrons should be minimized and actions taken to reduce unnecessary exposure. Neutron productionThe minimum energy required to remove a neutron from a nucleus decreases with increase in target atomic number 5) and lies between 6 to 16 MeV for nuclei heavier than carbon 6) . Linear accelerators generate high energy photon beams by accelerating electrons to 6-25 MV and then converting them to therapeutic X-rays. For photon energies below 10 MV, minimal photonuclear reaction occurs, and neutron production is negligible 5) . Neutrons are also produced by photodisintegration processes. However, since these have fewer interactions with the nuclei of the accelerator head components 7) , photonuclear reactions are considered to be the main cause of neutron contamination in external beam radiotherapy.Neutron production takes place inside machinery components of the linear accelerator head and the bodies of patients, as well as in the walls of the treatment room [1][2][3][4][8][9][10][11] . The target, beam collimation systems and multi-leaf collimators (MLCs) are the major sources of neutron production where the photon This study estimated gamma dose contributions to radiation therapists during high energy, whole pelvic, photon beam treatments and determined the optimum room entry times, in terms of safety of radiation therapists. Methods: Two types of technique (anteriorposterior opposing and 3-field technique) were studied. An Elekta Precise treatment system, operating up to 18 MV, was investigated. Measurements with an area monitoring device (a Mini 900R radiation monitor) were performed, to calculate gamma dose rates around the radiotherapy facility. Measurements inside the treatment room were performed when the linear accelerator was in use. The doses received by radiation therapists were estimated, and optimum room entry times were determined. Results: The highest gamma dose rates were approximately 7 μSv/h inside the treatment room, while the doses in the control room were close to background (~0 μSv/h) for all techniques. The highest personal dose received by radiation therapists was estimated at 5 mSv/yr. To optimize protection, radiation therapists should wait for up to11 min after beam-off prior to room entry. Conclusions: The potential risks to radiation therapists with standard safety procedures were well below internationally recommended values, but risks could be further decreased by delaying room entry times. Dependent on the te...

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Section: Neutron Production and Activationmentioning

confidence: 99%