Premium
An improved neutron collimator for brain tumor irradiations in clinical boron neutron capture therapy
Author(s) -
Liu Hungyuan B.,
Greenberg Dennis D.,
Capala Jacek,
Wheeler Floyd J.
Publication year - 1996
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.597772
Subject(s) - collimator , materials science , imaging phantom , dosimetry , neutron capture , neutron , nuclear medicine , monte carlo method , linear particle accelerator , neutron source , neutron radiation , optics , beam (structure) , physics , nuclear physics , medicine , statistics , mathematics
To improve beam penetration into a head allowing the treatment of deeper seated tumors, two neutron collimators were built sequentially and tested for use in the clinical boron neutron capture therapy (BNCT) program at the epithermal neutron irradiation facility of the Brookhaven Medical Research Reactor. The collimators were constructed from lithium‐impregnated polyethylene, which comprises Li 2 CO 3 powder (≊93% enriched isotopic 6 Li) uniformly dispersed in polyethylene to a total 6 Li content of 7.0 wt. %. The first collimator is 7.6 cm thick with a conical cavity 16 cm in diameter on the reactor core side tapering to 8 cm facing the patient's head. The second collimator is 15.2 cm thick with a conical cavity 20 cm in diameter tapering to 12 cm. A clinical trial of BNCT for patients with malignant brain tumors is underway using the first collimator. Results of phantom dosimetry and Monte Carlo computations indicate that the new 15.2 cm thick collimator will improve the neutron beam penetration. Thus, the second collimator was made and will be used in an upcoming clinical trial. In‐air and in‐phantom mixed‐field dosimetric measurements were compared to Monte Carlo computations for both collimators. The deeper penetration is achieved but at a sacrifice in beam intensity. In this report, a performance comparison of both collimators regarding various fluence rate and absorbed dose distributions in a head model is presented and discussed.