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4.
Z Med Phys ; 25(1): 36-47, 2015 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-24973309

RESUMO

The track length estimator (TLE) method, an "on-the-fly" fluence tally in Monte Carlo (MC) simulations, recently implemented in GATE 6.2, is known as a powerful tool to accelerate dose calculations in the domain of low-energy X-ray irradiations using the kerma approximation. Overall efficiency gains of the TLE with respect to analogous MC were reported in the literature for regions of interest in various applications (photon beam radiation therapy, X-ray imaging). The behaviour of the TLE method in terms of statistical properties, dose deposition patterns, and computational efficiency compared to analogous MC simulations was investigated. The statistical properties of the dose deposition were first assessed. Derivations of the variance reduction factor of TLE versus analogous MC were carried out, starting from the expression of the dose estimate variance in the TLE and analogous MC schemes. Two test cases were chosen to benchmark the TLE performance in comparison with analogous MC: (i) a small animal irradiation under stereotactic synchrotron radiation therapy conditions and (ii) the irradiation of a human pelvis during a cone beam computed tomography acquisition. Dose distribution patterns and efficiency gain maps were analysed. The efficiency gain exhibits strong variations within a given irradiation case, depending on the geometrical (voxel size, ballistics) and physical (material and beam properties) parameters on the voxel scale. Typical values lie between 10 and 10(3), with lower levels in dense regions (bone) outside the irradiated channels (scattered dose only), and higher levels in soft tissues directly exposed to the beams.


Assuntos
Algoritmos , Modelos Estatísticos , Método de Monte Carlo , Doses de Radiação , Radiometria/métodos , Raios X , Animais , Carga Corporal (Radioterapia) , Simulação por Computador , Humanos , Transferência Linear de Energia , Reprodutibilidade dos Testes , Sensibilidade e Especificidade , Software
9.
Cephalalgia ; 28(3): 300-1, 2008 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-18254899

RESUMO

Hemicrania continua (HC) is an indomethacin-responsive headache characterized by a chronic, strictly unilateral, side-locked without side-shifting, persistent headache. We report three cases of HC with atypical features in which an acute administration of indomethacin 50 mg IM (INDOTEST) was performed. In all three cases INDOTEST predicted chronic responsiveness to indomethacin. Thus, in cases of HC with atypical features, INDOTEST could help for a correct diagnosis and therapy.


Assuntos
Cefaleia/diagnóstico , Cefaleia/tratamento farmacológico , Indometacina/administração & dosagem , Adulto , Idoso , Doença Crônica , Método Duplo-Cego , Feminino , Humanos , Valor Preditivo dos Testes
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