Room: Exhibit Hall
Purpose: The present-day treatment methods use flattened and un-flattened X-rays beams in many advanced treatment modalities in the presence of bio compatible high Z materials. This current appraisal studies about the measure of fundamental physics parameters like Mass attenuation coefficient (Âµ/Ï?), Total Atomic (Ïƒa) and Electronic (Ïƒe) cross section, Effective atomic number (Zeff), Electron density (Nel) and Photon mean free path (mfp).
Methods: A good narrow beam geometry condition has been followed to find out mass attenuation coefficient (Âµ/Ï?) (MAC) for flattened and un-flattened X-ray beams. The result from MAC is used to calculate mean energy (using NIST data) total atomic (Ïƒa) and electronic cross section (Ïƒe) for different energies. The effective atomic number (Zeff), Electron density (Nel), photon mean free path (mfp) for both flattened and un-flattened X-ray beams for high Z material Stainless Steel (SS316) and Titanium Alloy (Grade5) are studied.
Results: The mean energy calculated from NIST data against mass attenuation coefficient closely matching with Monte Carlo. It shows that spectral weighted effective atomic number is independent of megavoltage energies in the Compton region. Effective electron density calculated using Zeff and MAC method is lesser compare to direct method for both high Z materials. The photon mean free path (mfp) at central axis is higher than at off-axis for flattened beam compare to un-flattened beam for both high Z material because of variation in energy spectrum for both type of X-ray beams.
Conclusion: A significant spectral variation is observed in flattening filter compare to un-flattened beam that affects the fundamental physics parameters. Itâ€™s well understood that how fundamental physics properties studied here behaves when different energies of flattened and un-flattened X-ray beams are interacting with high Z materials like Stainless Steel (SS316) and Titanium (Grade5) in clinical situation.