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Transmission measurements in air using the ESTRO mini-phantom

Johnsson, Stefan LU ; Ceberg, Crister LU ; Knöös, Tommy LU and Nilsson, Per LU (1999) In Physics in Medicine and Biology 44(10). p.2445-2450
Abstract
The aim of this work is to study the possibility of using the ESTRO mini-phantom for transmission measurements of primary kerma in water at a point free in air. We discuss in-air measurements in general, with special attention given to in-air equivalent measurements using a water equivalent mini-phantom. The study includes four different photon energies (4, 6, 10 and 18 MV), where scoring of dose and primary kerma inside a mini-phantom in narrow beam geometry is performed with the Monte Carlo code EGS4. The results reveal that relative measurements (i.e. with and without a water absorber present) at 10 cm depth in a mini-phantom do not represent the variation of primary kerma in water at a point free in air (deviations as large as 7% at 4... (More)
The aim of this work is to study the possibility of using the ESTRO mini-phantom for transmission measurements of primary kerma in water at a point free in air. We discuss in-air measurements in general, with special attention given to in-air equivalent measurements using a water equivalent mini-phantom. The study includes four different photon energies (4, 6, 10 and 18 MV), where scoring of dose and primary kerma inside a mini-phantom in narrow beam geometry is performed with the Monte Carlo code EGS4. The results reveal that relative measurements (i.e. with and without a water absorber present) at 10 cm depth in a mini-phantom do not represent the variation of primary kerma in water at a point free in air (deviations as large as 7% at 4 MV are observed). Minimum deviations are obtained at depths somewhat larger than the depth of dose maximum. The observed deviations are due to a considerable beam hardening in the water absorber, which changes the amount of attenuation and scatter inside the mini-phantom. (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
44
issue
10
pages
2445 - 2450
publisher
IOP Publishing
external identifiers
  • pmid:10533921
  • scopus:0032850295
ISSN
1361-6560
language
English
LU publication?
yes
id
b7291190-1f0c-43cf-a572-fceaebb41638 (old id 1114532)
alternative location
http://www.iop.org/EJ/article/0031-9155/44/10/306/m91006.pdf
date added to LUP
2008-07-04 12:17:11
date last changed
2017-01-01 04:51:38
@article{b7291190-1f0c-43cf-a572-fceaebb41638,
  abstract     = {The aim of this work is to study the possibility of using the ESTRO mini-phantom for transmission measurements of primary kerma in water at a point free in air. We discuss in-air measurements in general, with special attention given to in-air equivalent measurements using a water equivalent mini-phantom. The study includes four different photon energies (4, 6, 10 and 18 MV), where scoring of dose and primary kerma inside a mini-phantom in narrow beam geometry is performed with the Monte Carlo code EGS4. The results reveal that relative measurements (i.e. with and without a water absorber present) at 10 cm depth in a mini-phantom do not represent the variation of primary kerma in water at a point free in air (deviations as large as 7% at 4 MV are observed). Minimum deviations are obtained at depths somewhat larger than the depth of dose maximum. The observed deviations are due to a considerable beam hardening in the water absorber, which changes the amount of attenuation and scatter inside the mini-phantom.},
  author       = {Johnsson, Stefan and Ceberg, Crister and Knöös, Tommy and Nilsson, Per},
  issn         = {1361-6560},
  language     = {eng},
  number       = {10},
  pages        = {2445--2450},
  publisher    = {IOP Publishing},
  series       = {Physics in Medicine and Biology},
  title        = {Transmission measurements in air using the ESTRO mini-phantom},
  volume       = {44},
  year         = {1999},
}