Epid-based in vivo dose verification for lung stereotactic treatments delivered with multiple breath-hold segmented volumetric modulated arc therapy.
J Appl Clin Med Phys
; 20(3): 37-44, 2019 Mar.
Article
en En
| MEDLINE
| ID: mdl-30790439
ABSTRACT
We evaluated an EPID-based in-vivo dosimetry (IVD) method for the dose verification and the treatment reproducibility of lung SBRT-VMAT treatments in clinical routine. Ten patients with lung metastases treated with Elekta VMAT technique were enrolled. All patients were irradiated in five consecutive fractions, with total doses of 50 Gy. Set-up was carried out with the Elekta stereotactic body frame. Eight patients were simulated and treated using the Active Breath Control (ABC) system, a spirometer enabling patients to maintain a breath-hold at a predetermined lung volume. Two patients were simulated and treated in free-breathing using an abdominal compressor. IVD was performed using the SOFTDISO software. IVD tests were evaluated by means of (a) ratio R between daily in-vivo isocenter dose and planned dose and (b) γ-analysis between EPID integral portal images in terms of percentage of points with γ-value smaller than one (γ% ) and mean γ-values (γmean ) using a 3%(global)/3 mm criteria. Alert criteria of ±5% for R ratio, γ% < 90%, and γmean > 0.67 were chosen. 50 transit EPID images were acquired. For the patients treated with ABC spirometer, the results reported a high level of accuracy in dose delivery with 100% of tests within ±5%. The γ-analysis showed a mean value of γmean equal to 0.21 (range 0.04-0.56) and a mean γ% equal to 96.9 (range 78-100). Relevant discrepancies were observed only for the two patients treated without ABC, mainly due to a blurring dose effect due to residual respiratory motion. Our method provided a fast and accurate procedure in clinical routine for verifying delivered dose as well as for detecting errors.
Palabras clave
Texto completo:
1
Colección:
01-internacional
Banco de datos:
MEDLINE
Asunto principal:
Planificación de la Radioterapia Asistida por Computador
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Programas Informáticos
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Electrónica
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Radioterapia de Intensidad Modulada
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Contencion de la Respiración
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Dosimetría in Vivo
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Neoplasias Pulmonares
Límite:
Humans
Idioma:
En
Revista:
J Appl Clin Med Phys
Asunto de la revista:
BIOFISICA
Año:
2019
Tipo del documento:
Article
País de afiliación:
Italia