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An iterative algorithm for reconstructing incident beam distributions from transmission measurements using electronic portal imaging.

L Spies·M Partridge·B A Groh·T Bortfeld
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Abstract

The problem of reconstructing incident radiotherapy beam profiles from electronic portal images recorded behind a phantom is addressed. To this end an iterative algorithm is presented, which is able to extract the input beam profile from a portal image by compensating for the attenuation of the beam and subtracting the amount of scatter emitted by the phantom. The algorithm requires only a thickness map of the phantom. Scatter is estimated using a superposition method based on precalculated Monte Carlo scatter kernels. The method is tested for a homogeneous water-equivalent slab phantom for simple rectangular and complex multileaf collimated fields. It is shown that the method produces a stable result within four iterations yielding an accuracy for the incident beam distribution of better than 3%.

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AlgorithmsElectronicsImage Processing, Computer-AssistedPhantoms, ImagingRadiotherapy Planning, Computer-AssistedRadiotherapy, High-EnergyScattering, RadiationJournal ArticleResearch Support, Non-U.S. Gov't

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L Spies, M Partridge, B A Groh, T Bortfeld. 2001. An iterative algorithm for reconstructing incident beam distributions from transmission measurements using electronic portal imaging.. https://doi.org/10.1088/0031-9155%2F46%2F8%2F402

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