Measurement of photoneutron doses in and out of high-energy X-ray beam of a SATURNE-20 medical linear accelerator by ECE polycarbonate detectors

Sohrabi, Mehdi; Mostofizadeh, Ali

doi:10.1016/s1350-4487(99)00203-6

Cited by 18 publications

(7 citation statements)

References 7 publications

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“…The above conclusions are all in support of the findings that the fast, epithermal and thermal PN dose equivalents increase linearly as field size increases 13 , 31 , 33 , 50 , 52 , 53 .…”

Section: Experimental Findings and Resultssupporting

confidence: 80%

“…It has been recently demonstrated by us that fast, epithermal and thermal PN dose equivalents increase linearly as field size increases for field sizes 10 × 10, 20 × 20, 30 × 30 and 40 × 40 cm 2 studied 33 , 39 , 50 , as also discussed by others 13 , 52 , 53 . This can be due to less attenuation of the PNs by the accelerator head material components as the field size increases, and less scattering from the target, beam flattening filter and primary collimator.…”

Section: Experimental Findings and Resultsmentioning

confidence: 54%

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Photoneutron spectrometry by novel multi-directional spherical neutron spectrometry system

Sohrabi

Hakimi

2021

Sci Rep

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Neutron spectrometry in science and technology applications in general and accurate exotic photoneutron (PN) dosimetry of cancer patients undergoing high-dose high-energy X-rays therapy in medical accelerators in particular is of vital need. In this study, a novel passive multi-directional multi-detector neutron spectrometry system was developed and home-made using 6 polycarbonate/10B detectors on 6 sides of polyethylene (PE) cubes used bare and also embedded at center of PE spheres of 8 different diameters. The system provided well-resolved unfolded directional PN spectra showing thermal and fast PN peaks of 6 sides and mean spectrum in 5 field sizes at isocenter and other locations in 18 MV Siemens ONCOR medical linear accelerator bunker. The neutron spectrometry system developed has unique characteristics such as being simple, efficient, low cost, practical, and insensitive to low-LET radiation with well-resolved directional and mean spectra easily applicable in medicine, health, environment, science and technology in developing and developed laboratories.

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“…The above conclusions are all in support of the findings that the fast, epithermal and thermal PN dose equivalents increase linearly as field size increases 13 , 31 , 33 , 50 , 52 , 53 .…”

Section: Experimental Findings and Resultssupporting

confidence: 80%

Section: Experimental Findings and Resultsmentioning

confidence: 54%

Photoneutron spectrometry by novel multi-directional spherical neutron spectrometry system

Sohrabi

Hakimi

2021

Sci Rep

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“…The results concurred with published estimates of the annual activation dose received by staff during routine procedures, which were in the range of 0.7-5 mSv/yr 27,40,41) . Even though estimated annual doses for all approaches were below maximum permissible dose values, i.e., 20 mSv/yr 20) , radiation therapists should remain alert to protect themselves from unnecessary radiation and limit the equivalent dose to as low as reasonably achievable, especially since the thermoluminescent dosimeter records for most staff at TMH tend to be approximately 2 mSv/yr.…”

Section: Dose Rates Versus Timementioning

confidence: 97%

“…For longer irradiation times, more secondary neutrons are generated, hence increasing the amount of induced radioactivity 18) . In addition, smaller field sizes used for IMRT and MLCs affect neutron production and scatter 1,[17][18][19][20] .…”

Section: Factors Affecting Neutron Productionmentioning

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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“…After several hours of etching in special solution and applying high voltage to polycarbonate, ion tracks can be seen with unaided eyes. This detection method has been being used for more than three decades by Sohrabi et al [1][2][3][4][5]. After etching detector and applying high voltage to etching chamber, ion tracks must be counted and locally determined.…”

Section: Introductionmentioning

confidence: 99%

A Novel Method for Ion Track Counting in Polycarbonate Detector

Roshani

Shama

et al. 2013

Chinese Journal of Engineering

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A computer program for recognizing and counting the track of ions that are detected with polycarbonate detector has been written using MATLAB software. There are different programs for counting the track of ions in different detectors. Algorithm of this program specially has been written for polycarbonate detector and also for low magnification of optical microscope. Thus, with this method as per image of optical microscope, greater numbers of ions are visible and general distribution of ions can be better known. However, the accuracy of counting program is very high.

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Measurement of photoneutron doses in and out of high-energy X-ray beam of a SATURNE-20 medical linear accelerator by ECE polycarbonate detectors

Cited by 18 publications

References 7 publications

Photoneutron spectrometry by novel multi-directional spherical neutron spectrometry system

Photoneutron spectrometry by novel multi-directional spherical neutron spectrometry system

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

A Novel Method for Ion Track Counting in Polycarbonate Detector

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