title: Improved apparatus for neutron capture therapy of rat brain tumors.
abstract: OBJECTIVE
  The assembly for irradiating tumors in the rat brain at the thermal neutron beam port of the Brookhaven Medical Research Reactor was redesigned to lower the average whole-body dose from different components of concomitant radiation without changing the thermal neutron fluence at the brain tumor.
  
  
  METHODS
  At present, the tumor-bearing rat is positioned in a rat holder that functions as a whole-body radiation shield. A 2.54 cm-thick collimator with a centered conical aperture, 6 cm diameter tapering to 2 cm diameter, is used to restrict the size of the thermal neutron field. Using the present holder and collimator as a baseline design, Monte Carlo calculations and mixed-field dosimetry were used to assess new designs.
  
  
  RESULTS
  The computations indicate that a 0.5 cm-thick plate, made of 6Li2CO3 dispersed in polyethylene (Li-poly), instead of the existing rat holder, will reduce the whole-body radiation dose. Other computations show that a 10.16 cm-thick (4 inches) Li-poly collimator, having a centered conical aperture of 12 cm diameter tapering to 2 cm diameter, would further reduce the whole-body dose.
  
  
  CONCLUSIONS
  The proposed irradiation apparatus of tumors in the rat brain, although requiring a 2.3-fold longer irradiation time, would reduce the average whole-body dose to less than half of that from the existing irradiation assembly.
authors.affiliation: Medical Department, Brookhaven National Laboratory, Upton, NY 11973.
authors.forename: H B
authors.initials: HB
authors.lastname: Liu
authors.forename: D D
authors.initials: DD
authors.lastname: Joel
authors.forename: D N
authors.initials: DN
authors.lastname: Slatkin
authors.forename: J A
authors.initials: JA
authors.lastname: Coderre
mesh_terms: D000818:Animals; D001932:Brain Neoplasms / Q000532:radiotherapy*; D017247:Neutron Capture Therapy / Q000295:instrumentation*; D051381:Rats