Electron beam collimation with a photon MLC for standard electron treatments
| Autor: | S. Mueller, K. Loessl, Daniel Frei, D. Henzen, Peter Manser, Marco Stampanoni, Michael K. Fix, D. Frauchiger |
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| Rok vydání: | 2017 |
| Předmět: |
Organs at Risk
Photon Materials science Monte Carlo method Electrons Electron Collimated light 030218 nuclear medicine & medical imaging 03 medical and health sciences 0302 clinical medicine Optics Mixed beam Neoplasms Humans Radiology Nuclear Medicine and imaging Radiometry Photons Radiological and Ultrasound Technology business.industry Phantoms Imaging Radiotherapy Planning Computer-Assisted Radiotherapy Dosage Multileaf collimator 030220 oncology & carcinogenesis Cathode ray business Monte Carlo Method Beam (structure) |
| Zdroj: | Physics in medicine and biology. 63(2) |
| ISSN: | 1361-6560 |
| Popis: | Standard electron treatments are currently still performed using standard or molded patient-specific cut-outs placed in the electron applicator. Replacing cut-outs and electron applicators with a photon multileaf collimator (pMLC) for electron beam collimation would make standard electron treatments more efficient and would facilitate advanced treatment techniques like modulated electron radiotherapy (MERT) and mixed beam radiotherapy (MBRT). In this work, a multiple source Monte Carlo beam model for pMLC shaped electron beams commissioned at a source-to-surface distance (SSD) of 70 cm is extended for SSDs of up to 100 cm and validated for several Varian treatment units with field sizes typically used for standard electron treatments. Measurements and dose calculations agree generally within 3% of the maximal dose or 2 mm distance to agreement. To evaluate the dosimetric consequences of using pMLC collimated electron beams for standard electron treatments, pMLC-based and cut-out-based treatment plans are created for a left and a right breast boost, a sternum, a testis and a parotid gland case. The treatment plans consist of a single electron field, either alone (1E) or in combination with two 3D conformal tangential photon fields (1E2X). For each case, a pMLC plan with similar treatment plan quality in terms of dose homogeneity to the target and absolute mean dose values to the organs at risk (OARs) compared to a cut-out plan is found. The absolute mean dose to an OAR is slightly increased for pMLC-based compared to cut-out-based 1E plans if the OAR is located laterally close to the target with respect to beam direction, or if a 6 MeV electron beam is used at an extended SSD. In conclusion, treatment plans using cut-out collimation can be replaced by plans of similar treatment plan quality using pMLC collimation with accurately calculated dose distributions. |
| Databáze: | OpenAIRE |
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