High throughput film dosimetry in homogeneous and heterogeneous media for a small animal irradiator
| Autor: | Ross Berbeco, Jürgen Hesser, SK Ng, L. Wack, Erik Tryggestad, Panagiotis Tsiamas, Piotr Zygmanski, Wilfred Ngwa |
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| Rok vydání: | 2014 |
| Předmět: |
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Film Dosimetry Time Factors Materials science Phantoms Imaging business.industry Monte Carlo method Biophysics Water General Physics and Astronomy General Medicine Models Theoretical Signal Article Characterization (materials science) Optics Homogeneous Animals Dosimetry Radiology Nuclear Medicine and imaging business Monte Carlo Method Throughput (business) Beam (structure) |
| Zdroj: | Physica Medica. 30:36-46 |
| ISSN: | 1120-1797 |
| Popis: | Purpose We have established a high-throughput Gafchromic film dosimetry protocol for narrow kilovoltage beams in homogeneous and heterogeneous media for small-animal radiotherapy applications. The kV beam characterization is based on extensive Gafchromic film dosimetry data acquired in homogeneous and heterogeneous media. An empirical model is used for parameterization of depth and off-axis dependence of measured data. Methods We have modified previously published methods of film dosimetry to suit the specific tasks of the study. Unlike film protocols used in previous studies, our protocol employs simultaneous multi-channel scanning and analysis of up to nine Gafchromic films per scan. A scanner and background correction were implemented to improve accuracy of the measurements. Measurements were taken in homogeneous and inhomogeneous phantoms at 220 kVp and a field size of 5 × 5 mm 2 . The results were compared against Monte Carlo simulations. Results Dose differences caused by variations in background signal were effectively removed by the corrections applied. Measurements in homogeneous phantoms were used to empirically characterize beam data in homogeneous and heterogeneous media. Film measurements in inhomogeneous phantoms and their empirical parameterization differed by about 2%–3%. The model differed from MC by about 1% (water, lung) to 7% (bone). Good agreement was found for measured and modelled off-axis ratios. Conclusions EBT2 films are a valuable tool for characterization of narrow kV beams, though care must be taken to eliminate disturbances caused by varying background signals. The usefulness of the empirical beam model in interpretation and parameterization of film data was demonstrated. |
| Databáze: | OpenAIRE |
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