Monte Carlo model of accelerator, couch, vault, and tissue-equivalent phantom for scoring neutrons. Tally locations through the phantom are illustrated with arrows.
Neutron fluence in arbitrary units (A.U.) as a function of depth in tissue with the phantom present or absent. Phantom surface was located at and negative depths refer to the fluence in air above the phantom.
Neutron energy spectra in A.U. from a Varian 2100 accelerator calculated at the same location relative to the treatment head in air and at 0.1 cm depth in tissue.
Neutron energy spectra in A.U. at depths of 0.1, 1.5, 4.5, 9.5, and 19.5 cm in tissue.
Average neutron energy as a function of depth in tissue.
Neutron quality factor as a function of depth in tissue.
Dose equivalent as a function of distance from the central axis calculated at the phantom surface for field sizes of , , and .
Dose equivalent as a function of distance from the central axis calculated at the surface for SSDs of 90, 100, and 110 cm.
Neutron PDDE curves for neutrons incident on a phantom at 100 or 90 cm SSD from a treatment field either or and measured either on the central axis (0), at 25 cm, or at 45 cm away from the central axis. Legend: SSD, field size, distance from the central axis.
Neutron PDDE curves interpolated from D’Errico et al. (Ref. 15) for 0.24 MeV monoenergetic neutrons normally incident on water (“0.24 MeV”) and based on data from the current study for polyenergetic neutrons produced by a medical accelerator and scattered throughout a treatment vault incident at all angles on tissue (“Spectrum”).
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