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 (TM) 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 x 20 cm(2) than 10 x 10 cm(2) field sizes for both the 60 degrees wedge and open fields of 10 MV and 15 MV beams. In addition, the 60 degrees wedge fields generate higher photoneutron contamination when compared with the 45 degrees, 30 degrees 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 degrees wedge fields than the 10 MV beam, respectively.

Automated summary

This study aimed to measure the photoneutron dose equivalent produced in a motorized wedge field and open field of 10 MV and 15 MV photon beams in Elekta Versa HD (TM) linac. The results showed that the PNDE values were higher in 20 x 20 cm(2) than 10 x 10 cm(2) field sizes, and the 60 degrees wedge fields generated higher photoneutron contamination compared to the 45 degrees, 30 degrees wedge fields, and open fields.