title: Physical characteristics of the M.D. Anderson Hospital clinical neutron beam.
abstract: The physical characteristics of the M.D. Anderson Hospital (MDAH) clinical neutron beam are presented. The central-axis percent depth-dose values are intermediate between a 4 and 6 MV X-ray beam. The build-up curves reach a depth of maximum dose at 1.2 cm and have surface dose values of approximately 30%. Teflon flattening filters are employed to flatten the beam at the depth of the 75% dose level. Two wedges are available for shaping the beam; they are made of Teflon and produce wedge angles of 31 degrees and 45 degrees as defined by the ICRU. Output factors ranged from 0.88 for a 4 x 4 cm field to 1.12 for a 20 x 20 cm field. Tungsten blocks reduced the dose received at Dmax to 25% of the unblocked value but only 52% of the unblocked value at a depth of 22.8 cm.
mesh_terms: D005374:Filtration / Q000295:instrumentation; D006801:Humans; D009502:Neutrons; D010315:Particle Accelerators; D011138:Polytetrafluoroethylene; D011834:Radiation Monitoring; D011882:Radiotherapy, High-Energy / Q000295:instrumentation*; D014414:Tungsten
chemical_list: D011138:Polytetrafluoroethylene; D014414:Tungsten