Model-based prediction of portal dose images during patient treatment.
Med Phys
; 40(3): 031713, 2013 Mar.
Article
em En
| MEDLINE
| ID: mdl-23464308
ABSTRACT
PURPOSE:
Dosimetric verification of radiation therapy is crucial when delivering complex treatments like intensity modulated radiation therapy (IMRT) or volumetric modulated arc therapy (VMAT. Pretreatment verification, characterized by methods applied without the patient present and before the treatment start date, is typically carried out at most centers. In vivo dosimetric verification, characterized by methods applied with the patient present, is not commonly carried out in the clinic. This work presents a novel, model-based EPID dosimetry method that could be used for routine clinical in vivo patient treatment verification.METHODS:
The authors integrated a detailed fluence model with a patient scatter prediction model that uses a superposition of scatter energy fluence kernels, generated via Monte Carlo techniques, to determine patient scatter fluence delivered to the EPID. The total dose to the EPID was calculated using the sum of convolutions of the calculated energy fluence distribution entering the EPID with monoenergetic dose kernels, specific to the a-Si EPID. Measured images with simple, square fields delivered to slab phantoms were validated against predicted images. Measured and predicted images acquired during the delivery of IMRT fields to slabs and an anthropomorphic phantom were compared using the χ-comparison for 3% dose difference and 3 mm distance-to-agreement criteria.RESULTS:
Predicted and measured images of the square fields with slabs in the field agreed within 2.5%. Predicted portal dose images of clinical IMRT fields delivered to slabs and an anthropomorphic phantom agreed with measured images within 3% and 3 mm for an average of at least 97% of the infield pixels (defined as >10% maximum field dose) for each case, over all fields.CONCLUSIONS:
This work presents the first validation of the integration of a comprehensive fluence model with a patient and EPID radiation transport model that accounts for patient transmission, including complex factors such as patient scatter and the energy response of the a-Si detector. The portal dose image prediction model satisfies the 3% and 3 mm criteria for IMRT fields delivered to slab phantoms and could be used for patient treatment verification.
Texto completo:
1
Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Doses de Radiação
/
Radioterapia de Intensidade Modulada
/
Modelos Teóricos
Tipo de estudo:
Health_economic_evaluation
/
Prognostic_studies
/
Risk_factors_studies
Limite:
Humans
Idioma:
En
Revista:
Med Phys
Ano de publicação:
2013
Tipo de documento:
Article
País de afiliação:
Canadá