Monte Carlo investigation on the effect of air gap under bolus in post-mastectomy radiotherapy.
Phys Med
; 55: 82-87, 2018 Nov.
Article
em En
| MEDLINE
| ID: mdl-30471824
ABSTRACT
OBJECTIVES:
To investigate the dosimetric effect of air gaps under bolus on skin dose for left-sided post-mastectomy radiotherapy with loco regional involvement.METHODS:
Eight patients were planned retrospectively with volume modulated arc therapy (VMAT) and conventional static Field-in-Field (FinF) methods. Three different setups were applied for the 5-mm bolus over the chest wall having 0, 5 or 10â¯mm air gap under the bolus. The dose calculation was performed using Monte Carlo (MC) simulation. In addition, Analytic Anisotropic Algorithm (AAA) was used to demonstrate the differences observed in clinical setting.RESULTS:
The investigated air gaps under the bolus had minimal effect on surface dose for FinF plans (relative differenceâ¯≤â¯2.6%), whereas for VMAT plans the surface dose decreased 13.6% when compared to the case with no air gap. In both FinF and VMAT, the largest differences between AAA and MC were seen at the surface where AAA underestimated the dose by 1.5â¯Gy (pâ¯<â¯0.05) on average; while the dose in the target volume excluding the surface was relatively similar being on average 0.3â¯Gy (pâ¯>â¯0.05) larger with AAA than with MC calculations.CONCLUSIONS:
The surface dose was significantly lower with VMAT technique than with FinF technique. Possible air gaps under the bolus reduced the surface dose significantly further for VMAT but not for FinF treatments, which may have clinical impact on recurrence rate. AAA was shown to underestimate the surface dose when compared to MC calculation.Palavras-chave
Texto completo:
1
Temas:
ECOS
/
Financiamentos_gastos
Bases de dados:
MEDLINE
Assunto principal:
Planejamento da Radioterapia Assistida por Computador
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Método de Monte Carlo
/
Ar
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Radioterapia de Intensidade Modulada
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Mastectomia
Tipo de estudo:
Health_economic_evaluation
Limite:
Humans
Idioma:
En
Revista:
Phys Med
Assunto da revista:
BIOFISICA
/
BIOLOGIA
/
MEDICINA
Ano de publicação:
2018
Tipo de documento:
Article