Search results for "heterogeneities"

showing 3 items of 3 documents

A simple analytical method for heterogeneity corrections in low dose rate prostate brachytherapy

2015

In low energy brachytherapy, the presence of tissue heterogeneities contributes significantly to the discrepancies observed between treatment plan and delivered dose. In this work, we present a simplified analytical dose calculation algorithm for heterogeneous tissue. We compare it with Monte Carlo computations and assess its suitability for integration in clinical treatment planning systems. The algorithm, named as RayStretch, is based on the classic equivalent path length method and TG-43 reference data. Analytical and Monte Carlo dose calculations using Penelope2008 are compared for a benchmark case: a prostate patient with calcifications. The results show a remarkable agreement between …

MaleComputer sciencemedicine.medical_treatmentMonte Carlo methodBrachytherapyBrachytherapybrachytherapyDose calculation algorithmProstate:FÍSICA [UNESCO]medicineHumansRadiology Nuclear Medicine and imagingRadiation treatment planningprostateRadiological and Ultrasound Technologybusiness.industryRadiotherapy Planning Computer-AssistedUNESCO::FÍSICAProstatic NeoplasmsRadiotherapy Dosagelow dose rate:CIENCIAS MÉDICAS [UNESCO]medicine.anatomical_structurecalcificationsUNESCO::CIENCIAS MÉDICASBenchmark (computing)Nuclear medicinebusinessAlgorithmProstate brachytherapyAlgorithmsheterogeneities
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Fe-periclase reactivity at Earth's lower mantle conditions: Ab-initio geochemical modelling

2017

Intrinsic and extrinsic stability of the (Mg, Fe) O solid mixture in the Fe-Mg-Si-O system at high P, T conditions relevant to the Earth's mantle is investigated by the combination of quantum mechanical calculations (Hartree-26 Fock/DFT hybrid scheme), cluster expansion techniques and statistical thermodynamics. Iron in the (Mg, Fe) O binary mixture is assumed to be either in the low spin (LS) or in the high spin (HS) state. Un-mixing at solid state is observed only for the LS condition in the 23-42 GPa pressure range, whereas HS does not give rise to un-mixing. LS (Mg, Fe) O un-mixings are shown to be able to incorporate iron by subsolidus reactions with a reservoir of a virtual bridgmanit…

Subsolidus reaction modellingMgO-FeO binary010504 meteorology & atmospheric sciencesSilicate perovskiteLower mantle geochemical heterogeneitiesAnalytical chemistryAb initioLower mantle geochemical heterogeneities MgO-FeO binary Mixing Gibbs energy Pyrolitic geochemical mode Subsolidus reaction modellingMineralogyengineering.material010502 geochemistry & geophysics01 natural sciencesMantle (geology)Geochemistry and PetrologyMixing Gibbs energy0105 earth and related environmental sciencesPyrolitic geochemical modeSettore GEO/06 - MineralogiaPyrolitic geochemical modelAmbientaleDiamondHartreePartition coefficientengineeringPericlaseMgO-FeO binaryPyrolitic geochemical modelLower mantle geochemical heterogeneitiesSubsolidus reaction modellingMixing Gibbs energyGeologyCluster expansion
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Brachytherapy heterogeneity correction algorithm

2011

El objetivo de este trabajo de investigación es el estudio de la influencia de heterogeneidades de los tejidos en la dosimetría de braquiterapia. En concreto, hemos desarrollado un algoritmo que tiene en cuenta las calcificaciones localizadas dentro de la próstata y corrige la dosis de referencia en agua. Este algoritmo está basado en un modelo analítico y es aplicable a Sistemas de Planificación del Tratamiento (TPS) comerciales. El modelo analítico tiene un fundamento teórico consistente, y se basa en los valores de referencia (caso homogéneo) y en la definición de una longitud efectiva, que transforma el recorrido dentro de la calcificación en distancias mayores. La energía depositada en…

brachytherapyUNESCO::FÍSICAprostate calcificationscorrection algorithmheterogeneities
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