title: Implementing the complete beam hardening effect of the bowtie filter versus scaling beam intensities: effects on dosimetric applications in computed tomography.
abstract: The bowtie filter is an essential element of computed tomography scanners. Implementation of this filter in a Monte Carlo dosimetry platform can be based on Turner's method, which describes how to measure the filter thickness and relate the x-ray beam as a function of bowtie angle to the central beam. In that application, the beam hardening is accounted for by means of weighting factors that are associated to the photons according to their position (fan angle) and energy. We assessed an alternative approximation in which the photon spectrum is given a fan angle-dependent scaling factor. The aim of our investigation was to evaluate the effects on dose accuracy estimation when using the gold standard bowtie filter method versus a beam scaling approximation method. In particular, we wanted to assess the percentage dose differences between the two methods for several water thicknesses representative for different patients of different body mass index. The largest percentage differences were found for the thickest part of the bowtie filter and increased with patient size.
authors.affiliation: Katholieke Universiteit Leuven , Division of Medical Physics and Quality Assessment, Department of Imaging and Pathology, Herestraat 49 P.O. Box 7003, 3000 Leuven, Belgium.
authors.forename: Xochitl
authors.initials: X
authors.lastname: Lopez-Rendon
authors.affiliation: University Hospitals Leuven , Department of Radiology, Herestraat 49, Leuven 3000, Belgium.
authors.forename: Guozhi
authors.initials: G
authors.lastname: Zhang
authors.affiliation: Katholieke Universiteit Leuven , Division of Medical Physics and Quality Assessment, Department of Imaging and Pathology, Herestraat 49 P.O. Box 7003, 3000 Leuven, Belgium ; University Hospitals Leuven , Department of Radiology, Herestraat 49, Leuven 3000, Belgium.
authors.forename: Hilde
authors.initials: H
authors.lastname: Bosmans
authors.affiliation: Katholieke Universiteit Leuven , Division of Medical Physics and Quality Assessment, Department of Imaging and Pathology, Herestraat 49 P.O. Box 7003, 3000 Leuven, Belgium ; University Hospitals Leuven , Department of Radiology, Herestraat 49, Leuven 3000, Belgium.
authors.forename: Raymond
authors.initials: R
authors.lastname: Oyen
authors.affiliation: Katholieke Universiteit Leuven , Division of Medical Physics and Quality Assessment, Department of Imaging and Pathology, Herestraat 49 P.O. Box 7003, 3000 Leuven, Belgium.
authors.forename: Federica
authors.initials: F
authors.lastname: Zanca
keywords: Monte Carlo; bowtie filter; computed tomography; dose; patient size