title: On the choice of material for half-value-layer measurements for megavoltage x rays.
abstract: The relative sensitivity of various materials for the measurement of half-value-layer thickness has been calculated for bremsstrahlung x ray spectra in the energy range 5-40 MeV. It is concluded that low-atomic-number materials such as water are more sensitive to changes in spectral quality of megavoltage x rays than high-atomic-number materials such as lead.
mesh_terms: D000535:Aluminum; D003300:Copper; D007854:Lead; D011854:Radiochemistry; D011879:Radiotherapy Dosage; D011882:Radiotherapy, High-Energy / Q000379:methods*; D013057:Spectrum Analysis; D014001:Tin; D014867:Water
chemical_list: D014867:Water; D007854:Lead; D014001:Tin; D003300:Copper; D000535:Aluminum