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Build-up cap materials for measurement of photon head-scatter factors

Weber, Lars LU ; Nilsson, Per LU and Ahnesjö, Anders (1997) In Physics in Medicine and Biology 42(10). p.1875-1886
Abstract
The suitability of high-Z materials as build-up caps for head-scatter measurements has been investigated. Build-up caps are often used to enable characterization of fields too small for a mini-phantom. We have studied lead and brass build-up caps with sufficiently large wall thicknesses, as compared to the range of contaminating electrons originating in the accelerator head, and compared them with build-up caps made of ionization chamber equivalent materials, i.e. graphite. The results were also compared with measurements taken using square and cylindrical polystyrene mini-phantoms. Field sizes ranging from 3 cm x 3 cm up to 40 cm x 40 cm were studied for nominal photon energies of 4, 6, 10 and 18 MV. The results show that the use of lead... (More)
The suitability of high-Z materials as build-up caps for head-scatter measurements has been investigated. Build-up caps are often used to enable characterization of fields too small for a mini-phantom. We have studied lead and brass build-up caps with sufficiently large wall thicknesses, as compared to the range of contaminating electrons originating in the accelerator head, and compared them with build-up caps made of ionization chamber equivalent materials, i.e. graphite. The results were also compared with measurements taken using square and cylindrical polystyrene mini-phantoms. Field sizes ranging from 3 cm x 3 cm up to 40 cm x 40 cm were studied for nominal photon energies of 4, 6, 10 and 18 MV. The results show that the use of lead and brass build-up caps produces normalized head-scatter data slightly different from graphite build-up caps for large fields at high photon energies. At lower energies, however, no significant differences were found. The intercomparison between the two different plastic mini-phantoms and graphite caps showed no differences. (Less)
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author
organization
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type
Contribution to journal
publication status
published
subject
in
Physics in Medicine and Biology
volume
42
issue
10
pages
1875 - 1886
publisher
IOP Publishing
external identifiers
  • pmid:9364584
  • scopus:0030866208
ISSN
1361-6560
language
English
LU publication?
yes
id
b923a84e-d8d3-4f7f-aa1c-1d823206d313 (old id 1111512)
date added to LUP
2008-07-17 14:40:56
date last changed
2017-01-01 04:56:30
@article{b923a84e-d8d3-4f7f-aa1c-1d823206d313,
  abstract     = {The suitability of high-Z materials as build-up caps for head-scatter measurements has been investigated. Build-up caps are often used to enable characterization of fields too small for a mini-phantom. We have studied lead and brass build-up caps with sufficiently large wall thicknesses, as compared to the range of contaminating electrons originating in the accelerator head, and compared them with build-up caps made of ionization chamber equivalent materials, i.e. graphite. The results were also compared with measurements taken using square and cylindrical polystyrene mini-phantoms. Field sizes ranging from 3 cm x 3 cm up to 40 cm x 40 cm were studied for nominal photon energies of 4, 6, 10 and 18 MV. The results show that the use of lead and brass build-up caps produces normalized head-scatter data slightly different from graphite build-up caps for large fields at high photon energies. At lower energies, however, no significant differences were found. The intercomparison between the two different plastic mini-phantoms and graphite caps showed no differences.},
  author       = {Weber, Lars and Nilsson, Per and Ahnesjö, Anders},
  issn         = {1361-6560},
  language     = {eng},
  number       = {10},
  pages        = {1875--1886},
  publisher    = {IOP Publishing},
  series       = {Physics in Medicine and Biology},
  title        = {Build-up cap materials for measurement of photon head-scatter factors},
  volume       = {42},
  year         = {1997},
}