Water equivalence study of some phantoms based on effective photon energy, effective atomic numbers and electron densities for clinical MV X-ray and Co-60 γ-ray beams

A previously proposed procedure has been applied to some water equivalent phantoms namely PMMA, Polystyrene, Solid Water (WT1), RW3 and ABS for the first time to compute effective photon energy (E-eff), effective atomic numbers (Z(eff)) and electron densities (ne(eff)) for different MV X-ray beams and Co-60 gamma beam which are heterogeneous in energy. For the purpose of the present investigation, effective atomic cross-sections of the given materials have been determined first to obtain effective photon energies which were further used for calculation of Z(eff) and ne(eff). Similar procedure was adopted for Co-60 gamma-rays to check the validity of the present method. Results were found to be quite satisfactory. When it comes to the water equivalence, the E-eff results showed that the RW3 and ABS phantoms are more effective for 6 MV beam whereas RW3 and Polystyrene are more effective for 15 MV and Co-60 beams, respectively. The ABS and WT1 phantoms have better water equivalences than the others according to the Z(eff) and ne(eff) results, respectively. (C) 2012 Elsevier B.V. All rights reserved.