Neutron contamination of 10 MV X-rays: its relevance to treatment room door and maze design

Rudd, P. J.; Prior, DV; Austin-Smith, S

doi:10.1259/bjr/17350806

Cited by 10 publications

(6 citation statements)

References 5 publications

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“…It also prompted a change in routine radiation protection measurements to include a neutron dose assessment at 10MV energies. Similar conclusions were found by Rudd, Prior and Austin-Smith (2007) from measurements of an Elekta Precise linac with an NM2B meter. Their measurements outside mazes of 7 m or less indicated that the neutron ambient dose rate should be considered for 10 MV in order to keep within annual dose limits.…”

Section: Discussionsupporting

confidence: 85%

A relative comparison of neutron production between conventional and energy-matched flattening-filter-free (FFF) 10MV modes for an elekta linear accelerator

Delany¹,

Tudor²

2019

Biomed. Phys. Eng. Express

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Flattening Filter Free (FFF) Intensity Modulated Radiotherapy (IMRT) has become a widespread modality in radiotherapy treatments. Linac vendors have taken different approaches to implementing this technique. Elekta match the depth dose characteristics of FFF beams to their Conventional Flattening Filter (cFF) beams, increasing the maximum photon energy . At higher energies, greater than 10MV, there is the potential for increased unwanted neutron production . This study investigated the neutron production from an Elekta linac for 10MV FFF and cFF beams for various machine geometries.

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Section: Discussionsupporting

confidence: 85%

A relative comparison of neutron production between conventional and energy-matched flattening-filter-free (FFF) 10MV modes for an elekta linear accelerator

Delany¹,

Tudor²

2019

Biomed. Phys. Eng. Express

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“…This study used a Berthold neutron area survey meter based on a 3He gas proportional counter. Besides this study, various authors have reported the use of neutron survey meters for dose rate measurements in radiotherapy treatment rooms [ 15 , 29 ]. Survey meters based on 10 BF3 or 3 He proportional counters are highly stable, have large sensitive areas leading to high signal amplification and tissue equivalence, and exhibit excellent gamma discrimination.…”

Section: Resultsmentioning

confidence: 99%

Photoneutrons and Gamma Capture Dose Rates at the Maze Entrance of Varian TrueBeam and Elekta Versa HD Medical Linear Accelerators

Suliman

Khouqeer

Mayhoub

2023

Toxics

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Herein, we evaluated the neutron and gamma capture dose equivalent rates at the maze entrance of Varian TrueBeam and Elekta Versa HD™ medical linear accelerators (linacs) using experimental measurements as well as empirical calculations. Dose rates were measured using calibrated neutron and gamma area survey meters placed side-by-side at the measurement point of interest. Measurements were performed at a source-to-detector distance of 100 cm, with a 10 × 10 cm2 field size therapeutic X-ray beam, and a 30 × 30 × 15 cm3 solid water patient equivalent phantom, with a linac operating at 15, 10 MV, and 10 MV flattened filter-free (FFF). Dose rates were also measured at different points at the centerline along the maze towards the maze entrance. The measured dose equivalent rates at the maze entrance were comparable to those reported in the literature. The dose rates along the maze decreased exponentially towards the maze entrance and were significant for short maze lengths. The evaluated empirical methods for estimating neutron dose rates at the maze entrance of a linac proposed by Kersey, the modified Kersey method and Falcão method, agree by a factor of two from the experimental measurements. The results revealed vital radiation protection considerations owing to neutron contamination in external beam therapy.

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“…Thermal-neutron (n) tagging in gaseous proportional counters is achieved with the following reaction: n + 3 He ® p (573 keV) + 3 H (191 keV); Q=764 keV (1) where p and 3 H ionize the gas molecules and create a track of ion-electron pairs, whose number is proportional to the energy deposited in it. During the detection of thermal neutrons, 3 He acts as the stopping medium for them with reaction (1); meanwhile, with a higher stopping power than that of 3 He, tritium and protons are stopped by the filling gas.…”

Section: Experimental Partmentioning

confidence: 99%

“…Despite the fact that when compared with low-energy accelerators, high-energy accelerators exhibit some advantages (i.e., a lower skin dose, a larger depth dose and a lower scattered-radiation dose outside the field), the production of unwanted neutrons is the key issue in the use of high-energy accelerators. [1][2][3] The unwanted neutrons are produced due to the interaction of high-energy photons with high-Z metals, especially W and Pb used in the head of an accelerator. The threshold-energy values of a photoneutron production for Pb and W are 6.19 MeV and 6.17 MeV, respectively, while the respective values for Fe and Cu are 7.65 MeV and 9.91 MeV.…”

Section: Introductionmentioning

confidence: 99%

Investigation of photoneutron contamination from the 18-MV photon beam in a medical linear accelerator

Karaman¹,

Tanir²,

Karaman³

2019

Mater. Tehnol.

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In medical applications, high-energy linear accelerators are increasingly used. However, during a cancer treatment, unwanted photoneutrons caused by high-energy photon beams (>10 MV) increase the secondary cancer risk. This study aimed to investigate the effects of the square field size and distance to the isocenter on the neutron contamination emitted by an Elekta Versa HD medical linear accelerator using a Thermo Scientific RadEye neutron detector. The measurements were carried out for 18-MV photons with different square field sizes and different distances from the isocenter. It was clearly seen that the neutron dose equivalent decreases with both the increasing distance from the isocenter and square field size. Also, in order to analyze the neutron dose equivalent variation with field sizes and distances, Monte Carlo code Fluka was used. It was shown that MC-Fluka modeling and experimental results were consistent with each other. It was concluded that it is crucial to take into consideration the unwanted neutron dose in the radiation treatment.

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Neutron contamination of 10 MV X-rays: its relevance to treatment room door and maze design

Cited by 10 publications

References 5 publications

A relative comparison of neutron production between conventional and energy-matched flattening-filter-free (FFF) 10MV modes for an elekta linear accelerator

A relative comparison of neutron production between conventional and energy-matched flattening-filter-free (FFF) 10MV modes for an elekta linear accelerator

Photoneutrons and Gamma Capture Dose Rates at the Maze Entrance of Varian TrueBeam and Elekta Versa HD Medical Linear Accelerators

Investigation of photoneutron contamination from the 18-MV photon beam in a medical linear accelerator

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