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. 2017 Jan-Mar;42(1):18-24.
doi: 10.4103/jmp.JMP_99_16.

Structural Shielding Design of a 6 MV Flattening Filter Free Linear Accelerator: Indian Scenario

Bibekananda Mishra  1 , T Palani Selvam  2 , P K Dash Sharma  1
Affiliations

Structural Shielding Design of a 6 MV Flattening Filter Free Linear Accelerator: Indian Scenario

Bibekananda Mishra et al. J Med Phys. 2017 Jan-Mar.

Abstract

Detailed structural shielding of primary and secondary barriers for a 6 MV medical linear accelerator (LINAC) operated with flattening filter (FF) and flattening filter free (FFF) modes are calculated. The calculations have been carried out by two methods, one using the approach given in National Council on Radiation Protection (NCRP) Report No. 151 and the other based on the monitor units (MUs) delivered in clinical practice. Radiation survey of the installations was also carried out. NCRP approach suggests that the primary and secondary barrier thicknesses are higher by 24% and 26%. respectively, for a LINAC operated in FF mode to that of a LINAC operated in both FF and FFF modes with an assumption that only 20% of the workload is shared in FFF mode. Primary and secondary barrier thicknesses calculated from MUs delivered on clinical practice method also show the same trend and are higher by 20% and 19%, respectively, for a LINAC operated in FF mode to that of a LINAC operated in both FF and FFF modes. Overall, the barrier thickness for a LINAC operated in FF mode is higher about 20% to that of a LINAC operated in both FF and FFF modes.

Keywords: Flattening filter; flattening filter free; medical linear accelerator; monitor units; primary barrier; secondary barrier.

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Conflict of interest statement

There are no conflicts of interest.

Figures

Figure 1
Figure 1
Standard layout of a 6 MV medical linear accelerator bunker.
Figure 2
Figure 2
Layout of a 6 MV medical linear accelerator bunker indicating leakage radiation scattered down the maze.
See this image and copyright information in PMC

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