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A novel technique to optimise the length of a linear accelerator treatment room maze without compromising radiation protection / Ihsan Al-affan; Simon C Evans; Mohammed Qutub; Richard Hugtenburg
Journal of Radiological Protection
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Simulations with the FLUKA Monte Carlo code were used to establish the possibility of using lead to cover the existing concrete walls of a linear accelerator treatment room maze, in order to reduce the dose of the scattered photons at the maze entrance. In the present work, a pilot study performed a...
|Published in:||Journal of Radiological Protection|
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Simulations with the FLUKA Monte Carlo code were used to establish the possibility of using lead to cover the existing concrete walls of a linear accelerator treatment room maze, in order to reduce the dose of the scattered photons at the maze entrance. In the present work, a pilot study performed at Singleton Hospital in Swansea was used to pioneer the use of lead sheets of various thicknesses to absorb scattered low energy photons in the maze. The dose reduction was considered to be due to the strong effect of the photoelectric interaction in lead resulting in attenuation of the back-scattered photons. Calculations with FLUKA with mono-energetic photons were used to represent the main components of the X-ray spectrum up to 10 MV. The reason for using mono-energetic photons was to study the behaviour of each energy component from associated interaction processes. The results showed that adding lead of 1 to 4 mm thickness to the walls and floor of the maze reduced the dose at the maze entrance by up to 80%. Subsequent scatter dose measurements performed at the maze entrance of an existing treatment room with 1.3 mm thickness of lead sheets added to the maze walls and floor supported the results from the simulations. The dose reduction at the maze entrance with the lead in place was up to 50%. The variation between simulation and measurement was attributed to the fact that insufficient lead was available to completely cover the maze walls and floor. This novel proposal of covering part or the entire maze walls with a few millimetres thickness of lead has implications for the design of linear accelerator treatment rooms since it has potential to provide savings, in terms of space and costs, when an existing maze requires upgrading in an environment where space is limited and the maze length cannot be extended sufficiently to reduce the dose.
Swansea University Medical School