Dosimetric verification of open asymmetric photon fields calculated with a treatment planning system based on dose-to-energy-fluence concepts
Hurkmans, Coen ; Knöös, Tommy LU
and Nilsson, Per
LU
(1996)
In Physics in Medicine and Biology
41(8).
p.1277-1290
- Abstract
- Output normalized dose profiles for asymmetric open photon fields has been calculated using a commercial treatment planning system (TPS) based on a dose-to-energy-fluence concept. The model does not require any additional measurements for off-axis fields. Calculations are compared with measurements for quadratic fields of 5 cm x 5 cm up to 20 cm x 20 cm, with their geometric field centre positioned 10 cm off-axis in the in-plane direction. The measurements include depth doses and profiles in-plane as well as cross-plane for nominal photon energies of 4, 6 and 18 MV x-rays. Both calculated and measured doses are normalized with respect to a 10 cm x 10 cm reference field, therefore making it possible to compare not only the relative... (More)
- Output normalized dose profiles for asymmetric open photon fields has been calculated using a commercial treatment planning system (TPS) based on a dose-to-energy-fluence concept. The model does not require any additional measurements for off-axis fields. Calculations are compared with measurements for quadratic fields of 5 cm x 5 cm up to 20 cm x 20 cm, with their geometric field centre positioned 10 cm off-axis in the in-plane direction. The measurements include depth doses and profiles in-plane as well as cross-plane for nominal photon energies of 4, 6 and 18 MV x-rays. Both calculated and measured doses are normalized with respect to a 10 cm x 10 cm reference field, therefore making it possible to compare not only the relative distributions but also the absolute dose levels; that is, calculation of monitor units is included. The calculated depth-dose curves are generally in good agreement with measured data with an accuracy at the absolute dose level of 2% at depths beyond the dose maximum. The cross-plane profiles are calculated with an accuracy better than 3% within the field. The 'tilt' towards the collimator central axis of the in-plane profiles is predicted by the model, but is somewhat overestimated at large depths. The system provides the possibility to separate the primary and scattered parts of the dose and the cause of this tilting was studied by comparing calculated phantom-scattering and head-scattering dose profiles for a symmetric 40 cm x 20 cm field to dose profiles for an asymmetric 20 cm x 20 cm field. The tilting is shown to originate from a change both in phantom scattering and in head scattering compared to the case of symmetrical fields. The results indicate that the investigated TPS can calculate dose distributions in open asymmetric fields with a high degree of accuracy, typically better than 2-3%. (Less)
Please use this url to cite or link to this publication:
https://lup.lub.lu.se/record/1110183
- author
- Hurkmans, Coen
; Knöös, Tommy
LU
and Nilsson, Per
LU
- organization
- publishing date
- 1996
- type
- Contribution to journal
- publication status
- published
- subject
- in
- Physics in Medicine and Biology
- volume
- 41
- issue
- 8
- pages
- 1277 - 1290
- publisher
- IOP Publishing
- external identifiers
-
- pmid:8858720
- scopus:0029902094
- ISSN
- 1361-6560
- DOI
- 10.1088/0031-9155/41/8/003
- language
- English
- LU publication?
- yes
- id
- 87954b62-7d13-43ca-b43a-ad94e2f24490 (old id 1110183)
- date added to LUP
- 2016-04-01 11:56:41
- date last changed
- 2022-01-26 20:32:50
@article{87954b62-7d13-43ca-b43a-ad94e2f24490,
abstract = {{Output normalized dose profiles for asymmetric open photon fields has been calculated using a commercial treatment planning system (TPS) based on a dose-to-energy-fluence concept. The model does not require any additional measurements for off-axis fields. Calculations are compared with measurements for quadratic fields of 5 cm x 5 cm up to 20 cm x 20 cm, with their geometric field centre positioned 10 cm off-axis in the in-plane direction. The measurements include depth doses and profiles in-plane as well as cross-plane for nominal photon energies of 4, 6 and 18 MV x-rays. Both calculated and measured doses are normalized with respect to a 10 cm x 10 cm reference field, therefore making it possible to compare not only the relative distributions but also the absolute dose levels; that is, calculation of monitor units is included. The calculated depth-dose curves are generally in good agreement with measured data with an accuracy at the absolute dose level of 2% at depths beyond the dose maximum. The cross-plane profiles are calculated with an accuracy better than 3% within the field. The 'tilt' towards the collimator central axis of the in-plane profiles is predicted by the model, but is somewhat overestimated at large depths. The system provides the possibility to separate the primary and scattered parts of the dose and the cause of this tilting was studied by comparing calculated phantom-scattering and head-scattering dose profiles for a symmetric 40 cm x 20 cm field to dose profiles for an asymmetric 20 cm x 20 cm field. The tilting is shown to originate from a change both in phantom scattering and in head scattering compared to the case of symmetrical fields. The results indicate that the investigated TPS can calculate dose distributions in open asymmetric fields with a high degree of accuracy, typically better than 2-3%.}},
author = {{Hurkmans, Coen and Knöös, Tommy and Nilsson, Per}},
issn = {{1361-6560}},
language = {{eng}},
number = {{8}},
pages = {{1277--1290}},
publisher = {{IOP Publishing}},
series = {{Physics in Medicine and Biology}},
title = {{Dosimetric verification of open asymmetric photon fields calculated with a treatment planning system based on dose-to-energy-fluence concepts}},
url = {{http://dx.doi.org/10.1088/0031-9155/41/8/003}},
doi = {{10.1088/0031-9155/41/8/003}},
volume = {{41}},
year = {{1996}},
}