Evaluation of photoneutron dose equivalent in 10 MV and 15 MV beams for wedge and open fields in the Elekta Versa HD linac.

In a high-energy medical linear accelerator (linac), if the interaction of photon energy is higher than the neutron binding energy of high atomic material, it emits a neutron field through a photonuclear reaction. The objective of this current study is to measure the photoneutron dose equivalent produces in a motorized wedge field and open field of 10 MV and 15 MV photon beams in Elekta Versa HD™ linac. The PNDE values were recorded at various positions along the patient plane using the Bubble Detector-Personal Neutron Dosimeter (BD-PND). The results revealed that the PNDE values are higher in 20 × 20 cm2 than 10 × 10 cm2 field sizes for both the 60° wedge and open fields of 10 MV and 15 MV beams. In addition, the 60° wedge fields generate higher photoneutron contamination when compared with the 45°, 30° wedge fields and open field sizes. Hence, on average PNDE values produced by the 15 MV beam were higher by a factor of 1.98 and 2.11 times for open and 60° wedge fields than the 10 MV beam, respectively. • The effect of wedge and open field on photoneutron production in 10 MV and 15 MV beams was measured using Bubble Detector. • Neutrons are generated through photonuclear reactions with high atomic material. • At in-fields, the PNDE values were higher for larger field sizes for both wedge and open fields. • The universal wedge field yields higher photoneutron contamination than the open field. • The 10 MV beam produces a lesser photoneutron dose equivalent than the 15 MV beam. [ABSTRACT FROM AUTHOR]