Premium
Boron self‐shielding effects on dose delivery of neutron capture therapy using epithermal beam and boronophenylalanine
Author(s) -
Ye SungJoon
Publication year - 1999
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 - 10.1118/1.598769
Subject(s) - neutron capture , electromagnetic shielding , neutron , neutron temperature , dosimetry , boron , materials science , radiochemistry , nuclear medicine , neutron radiation , imaging phantom , neutron flux , percentage depth dose curve , nuclear physics , chemistry , ionization chamber , medicine , physics , ion , ionization , organic chemistry , composite material
Previous dosimetry studies for boron neutron capture therapy have often neglected the thermal neutron self‐shielding effects caused by the10 B accumulation in the brain and the tumor. The neglect of thermal neutron flux depression, therefore, results in an overestimation of the actual dose delivery. The relevant errors are expected to be more pronounced when boronophenylalanine is used in conjunction with an epithermal neutron beam. In this paper, the boron self‐shielding effects are calculated in terms of the thermal neutron flux depression across the brain and the dose delivered to the tumors. The degree of boron self‐shielding is indicated by the difference between the thermal neutron fluxes calculated with and without considering a10 B concentration as part of the head phantom composition. The boron self‐shielding effect is found to increase with increasing10 B concentrations and penetration depths from the skin. The calculated differences for10 B concentrations of 7.5–30 ppm are 2.3%–8.3% at 2.3 cm depth (depth of the maximum brain dose) and 4.6%–17% at 7.3 cm depth (the center of the brain). The additional self‐shielding effects by the10 B concentration in a bulky tumor are investigated for a 3‐cm‐diam spherical tumor located either near the surface (3.3 cm depth) or at the center of the brain (7.3 cm depth) along the beam centerline. For 45 ppm of10 B in the tumor and 15 ppm of10 B in the brain, the dose delivered to the tumors is approximately 10% lower at 3.3 cm depth and 20% lower at the center of the brain, compared to the dose neglecting the boron self‐shielding in transport calculations.