Fabrication of inhouse phantom to study the dosimetric accuracy of FF & FFF beam in for high energy photon beam

Aim: Present study was under taken to evaluate the performance of different algorithms for Flattening Filter Free (FFF) photon beams and flattening filter (FF) beams in three inhomogeneous mediums. Materials and Method: Three Computed Tomography (CT) image sets of the CIRS phantom, containing ionisation chamber respectively in lung, bone and tissue regions, maintained in SAD setup were acquired. The corresponding Treatment Planning System (TPS) calculated and ionisation chamber measured doses at the centre of chamber (in the three mediums) were compared for flattened and non-flattened photon beams. Results: The results was reported for photon energies 6MV, 10MV, 15MV, 6FFF and 10FFF at field sizes of 10x10 cm2, and 15x15 cm2. In Monte carlo algorithm the lung inhomogeneity shows the maximum dose variation was -3.6% of measured chamber dose in 10MVFFF photon energy for the field size 10X10 cm2. In Collapse cone algorithm the lung inhomogeneity shows the maximum dose variation was 4.36% of measured chamber dose in 10MV photon energy for the field size 10X10 cm2 whereas Pencil beam also shows highest dose variation in lung inhomogeneity was 4.99% of measured chamber dose in 10MV photon energy for the field size 15X15 cm2. In lung structure, higher deviation was recorded by all the three algorithms. Conclusion: Both, FF and FFF beams performed differently in Lung, water and bone mediums. The assessment of algorithms were conducted using the anthropomorphic phantom, therefore these finding may help in selection of appropriate algorithm for particular clinical settings in radiation delivery.