Study and evaluation of the Siemens virtual wedge factor: dosimetric monitor system and variable field effects.
Phys Med Biol
; 53(5): 1313-23, 2008 Mar 07.
Article
in En
| MEDLINE
| ID: mdl-18296764
ABSTRACT
In the year 1997 Siemens introduced the virtual wedge in its accelerators. The idea was that a dose profile similar to that of a physical wedge can be obtained by moving one of the accelerator jaws at a constant speed while the dose rate is changing. This work explores the observed behaviour of virtual wedge factors. A model is suggested which takes into account that at any point in time, when the jaw moves, the dose at a point of interest in the phantom is not only due to the direct beam. It also depends on the scattered radiation in the phantom, the head scatter and the behaviour of the monitoring system of the accelerator. Measurements are performed in a Siemens Primus accelerator and compared to the model predictions. It is shown that the model agrees reasonably well with measurements spanning a wide range of conditions. A strong dependence of virtual wedge factors on the dosimetric board has been confirmed and an explanation has been given on how the balance between different contributions is responsible for virtual wedge factors values.
Full text:
1
Collection:
01-internacional
Database:
MEDLINE
Main subject:
Radiometry
/
Artifacts
Type of study:
Prognostic_studies
Language:
En
Journal:
Phys Med Biol
Year:
2008
Document type:
Article
Affiliation country:
Spain
Country of publication:
ENGLAND
/
ESCOCIA
/
GB
/
GREAT BRITAIN
/
INGLATERRA
/
REINO UNIDO
/
SCOTLAND
/
UK
/
UNITED KINGDOM