(Sunday, 7/29/2018) 3:00 PM - 6:00 PM
Room: Exhibit Hall
Purpose: An addition of high Z implants in the treatment vicinity or beam path is unavoidable in certain clinical situation. The current assessment studies about the properties of radiation interaction parameters such as Mass Attenuation Co-efficient (MAC), X-ray Beam Transmission Factor (Indirectly Beam Attenuation), Interface Effects like Backscatter Dose Perturbation Factor (BSDF) and Forward Dose Perturbation Factor (FDPF) for flattened and un-flattened X-ray beam.
Methods: The MAC for Stainless Steel and Titanium alloy is measured with the help of CC13 Chamber having proper build-up with narrow beam geometry. The X-ray beam transmission factors measured for Stainless Steel and Titanium alloy for different field size, off-axis and depths. The profile analysis with the help of Radiation Field Analyzer (RFA) is done for both field size and depth to study the profile variation due to phantom scattering and spectral variation of the beam. The interface effects called BSDF was measured with the help of Gafchromic film at maximum BSDF peak position calculated using Acuros AXB algorithm, the FDPF was measured at exit side of high Z material with the help of PPC40 chamber.
Results: The MAC, in either case, decreases with increase in energy for Stainless Steel (SS) and Titanium (Ti) alloy. The MAC increases with the change in X-ray from flattened to un-flattened beam because of the lower mean energy. The X-ray Beam Transmission factor increases with the increase in energy as the penetration power increases and also increases with field size and depth due to increase in phantom scatter. The BSDF and FDPF are in agreement with AXB algorithm.
Conclusion: The fundamental properties of X-ray photon beam interaction parameters are studied comprehensively in the presence of high Z material like Stainless Steel and Titanium alloy using both flattened and un-flattened beams to understand and incorporate the concept in clinical condition.
Keywords
Flattening Filters, Energy Spectrum, Dosimetry
Taxonomy
TH- External beam- photons: Standard field experimental dosimetry
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