Assessment of portal image resolution improvement using an external aluminum target and polystyrene electron filter.
Radiat Oncol
; 14(1): 70, 2019 Apr 25.
Article
em En
| MEDLINE
| ID: mdl-31023340
ABSTRACT
BACKGROUND:
In this study, an external 8 mm thick aluminum target was installed on the upper accessory tray mount of a medical linear accelerator head. The purpose of this study was to determine the effects of the external aluminum target beam (Al-target beam) on the portal image quality by analyzing the spatial and contrast resolutions. In addition, the image resolutions with the Al-target beams were compared with those of conventional 6 megavoltage (MV) images.METHODS:
The optimized Al-target beam was calculated using Monte Carlo simulations. To validate the simulations, the percentage depth dose and lateral profiles were measured and compared with the modeled dose distributions. A PTW resolution phantom was used for imaging to assess the image resolution. The spatial resolution was quantified by determining the modulation transfer function. The contrast resolution was determined by a fine contrast difference between the 27 measurement areas. The spatial and contrast resolutions were compared with the those of conventional portal images.RESULTS:
The measured and calculated percentage depth dose of the Al-target beam were consistent within 1.6%. The correspondence of measured and modelled profiles was evaluated by gamma analysis (3%, 3 mm) and all gamma values inside the field were less than one. The critical spatial frequencies (f50) of the images obtained with the Al-target beam and conventional imaging beam were 0.745 lp/mm and 0.451 lp/mm, respectively. The limiting spatial frequencies (f10) for the Al-target beam image and the conventional portal image were 2.39 lp/mm and 1.82 lp/mm, respectively. The Al-target beam resolved the smaller and lower contrast objects better than that of the MV photon beam.CONCLUSION:
The Al-target beams generated by the simple target installation method provided better spatial and contrast resolutions than those of the conventional 6 MV imaging beam.Palavras-chave
Texto completo:
1
Base de dados:
MEDLINE
Assunto principal:
Aceleradores de Partículas
/
Poliestirenos
/
Garantia da Qualidade dos Cuidados de Saúde
/
Processamento de Imagem Assistida por Computador
/
Imagens de Fantasmas
/
Elétrons
/
Alumínio
Tipo de estudo:
Health_economic_evaluation
/
Prognostic_studies
Limite:
Humans
Idioma:
En
Revista:
Radiat Oncol
Assunto da revista:
NEOPLASIAS
/
RADIOTERAPIA
Ano de publicação:
2019
Tipo de documento:
Article
País de afiliação:
Coréia do Sul