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Verification of a pencil beam based treatment planning system: output factors for open photon beams shaped with MLC or blocks

Hansson, H; Bjork, P; Knöös, Tommy LU and Nilsson, Per LU (1999) In Physics in Medicine and Biology 44(9). p.201-207
Abstract
The accuracy of monitor unit calculations from a pencil beam based, three-dimensional treatment planning system (3D TPS) has been evaluated for open irregularly shaped photon fields. The dose per monitor unit was measured in water and in air for x-ray beam qualities from 6 to 15 MV. The fields were shaped either with a multileaf collimator (MLC) or with customized alloy blocks. Calculations from the 3D TPS were compared with measurements. The agreement between calculated and measured dose per monitor unit depended on field size and the amount of blocking and was within 3% for the MLC-shaped fields. The deviation could be traced to limitations in head scatter modelling for the MLC. For fields shaped with alloy blocks, the dose per monitor... (More)
The accuracy of monitor unit calculations from a pencil beam based, three-dimensional treatment planning system (3D TPS) has been evaluated for open irregularly shaped photon fields. The dose per monitor unit was measured in water and in air for x-ray beam qualities from 6 to 15 MV. The fields were shaped either with a multileaf collimator (MLC) or with customized alloy blocks. Calculations from the 3D TPS were compared with measurements. The agreement between calculated and measured dose per monitor unit depended on field size and the amount of blocking and was within 3% for the MLC-shaped fields. The deviation could be traced to limitations in head scatter modelling for the MLC. For fields shaped with alloy blocks, the dose per monitor unit was calculated to be within 1.6% of measured values for all fields studied. The measured and calculated relative phantom scatter for fields with the same equivalent field size were identical for MLC and alloy shaped fields. These results indicate that the accuracy in the TPS calculations for open irregular fields, shaped with MLC or blocks, is satisfactory for clinical situations. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Physics in Medicine and Biology
volume
44
issue
9
pages
201 - 207
publisher
IOP Publishing
external identifiers
  • pmid:10495127
  • scopus:18144453521
ISSN
1361-6560
language
English
LU publication?
yes
id
8e58dd6c-3292-43eb-9009-75dc8bb9171f (old id 1114534)
alternative location
http://www.iop.org/EJ/article/0031-9155/44/9/402/m909n2.pdf
date added to LUP
2008-07-04 12:25:57
date last changed
2017-07-23 03:46:57
@article{8e58dd6c-3292-43eb-9009-75dc8bb9171f,
  abstract     = {The accuracy of monitor unit calculations from a pencil beam based, three-dimensional treatment planning system (3D TPS) has been evaluated for open irregularly shaped photon fields. The dose per monitor unit was measured in water and in air for x-ray beam qualities from 6 to 15 MV. The fields were shaped either with a multileaf collimator (MLC) or with customized alloy blocks. Calculations from the 3D TPS were compared with measurements. The agreement between calculated and measured dose per monitor unit depended on field size and the amount of blocking and was within 3% for the MLC-shaped fields. The deviation could be traced to limitations in head scatter modelling for the MLC. For fields shaped with alloy blocks, the dose per monitor unit was calculated to be within 1.6% of measured values for all fields studied. The measured and calculated relative phantom scatter for fields with the same equivalent field size were identical for MLC and alloy shaped fields. These results indicate that the accuracy in the TPS calculations for open irregular fields, shaped with MLC or blocks, is satisfactory for clinical situations.},
  author       = {Hansson, H and Bjork, P and Knöös, Tommy and Nilsson, Per},
  issn         = {1361-6560},
  language     = {eng},
  number       = {9},
  pages        = {201--207},
  publisher    = {IOP Publishing},
  series       = {Physics in Medicine and Biology},
  title        = {Verification of a pencil beam based treatment planning system: output factors for open photon beams shaped with MLC or blocks},
  volume       = {44},
  year         = {1999},
}