Experimental determination of peripheral photon dose components for different IMRT techniques and linear accelerators.
Z Med Phys
; 19(2): 120-8, 2009.
Article
em En
| MEDLINE
| ID: mdl-19678527
ABSTRACT
PURPOSE:
To quantify the relative peripheral photon doses (PD) to healthy tissues outside the treated region for different IMRT technologies and linac head designs. MATERIAL ANDMETHODS:
Measurements were performed on an Elekta linac for various energies (6 MV, 10 MV, 25 MV) at different depths at a distance of 29 cm off-axis (vertical measurements) and different distances from the field edge at constant depth of 10 cm (horizontal measurements). These measurements were compared with results obtained on a Siemens linac at 6 MV and 15 MV. TLD-700 detectors were used to quantify the PDs relative to the dose in the volume exposed with the primary beam. Intensity modulated (IM)-beams with identical fluence patterns were generated with a segmental multileaf (sMLC) technique and with lead-containing cerrobend compensators (MCP96). PD values of IM beams were compared with open beam values. All measurement results of the two different linacs, the different IM methods and the different energies were normalized to the same mean dose.RESULTS:
PD values were distinctly higher near the surface (0.5-20 mm) than at larger depth and showed the same trend for all photon beam energies. In comparison with the open field, the photon dose component of PD for IM beams delivered with a segmental MLC technique were increased by a factor varying from 1.2 to 1.8, depending on photon energy and depth. This ratio was around 2 for compensator based IMRT. Depending on depth and distance from the field edge the PD on the Siemens machine was about 30% to 50% higher than on the Elekta machine for the same nominal photon energy.CONCLUSION:
The treatment head design of a linac has a large impact on PD in IMRT as well as for open beams. PD can be minimized by proper selection of treatment delivery method and photon beam energy.
Buscar no Google
Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Fótons
Tipo de estudo:
Health_economic_evaluation
Limite:
Humans
Idioma:
En
Revista:
Z Med Phys
Assunto da revista:
RADIOTERAPIA
Ano de publicação:
2009
Tipo de documento:
Article
País de afiliação:
Alemanha