Document Type : Research Articles
Department of Radiation Oncology, Sri Shankara Cancer Hospital and Research Centre, Bengaluru, Karnataka, 560004, India.
Department of Physics, SAS, Vellore Institute of Technology, Vellore, Tamil Nadu, India.
Centre for Biomaterials, Cellular and Molecular Theranostics, Vellore Institute of Technology, Vellore, Tamil Nadu, India.
Purpose: This work presents the measure of fundamental interaction parameters like mass attenuation coefficient
(μ/ρ), mean energy, total atomic (σa) and electronic (σe) cross section, effective atomic number (Zeff), electron density
(Nel) and mean free path (mfp) using FF and UF megavoltage x-ray beam for high Z implants. Methods: Narrow beam
geometry is used to find out mass attenuation coefficient (μ/ρ) (MAC) which is then used to calculate mean energy (using
NIST data), total atomic (σa) and electronic cross section (σe) for different energies. The effective atomic number (Zeff),
Electron density (Nel), mean free path (mfp) for both flattened and unflattened x-ray beams for high Z material stainless
steel (SS316) and titanium alloy (Grade 5) are studied. Results: The mean energies calculated from NIST data against
mass attenuation coefficient were in good agreement with Monte Carlo value. 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 compared to direct method for both high Z materials. The mean free path (mfp)
is higher along the central axis than off-axis for flattened beam in comparison to unflattened beam for both of the high
Z materials studied because of the variation in energy spectrum for both FF and UF x-ray beams. Conclusion: This
study elaborated the fundamental interaction parameters of different energies of flattened and unflattened x-ray beam
interactions with high Z materials such as Stainless Steel (SS316) and Titanium (Grade5) relevant in a clinical scenario.