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1.
Phys Med Biol ; 59(18): 5305-16, 2014 Sep 21.
Artigo em Inglês | MEDLINE | ID: mdl-25146446

RESUMO

Permanent seed implant brachytherapy is currently used for adjuvant radiotherapy of early stage prostate and breast cancer patients. The current standard for calculation of dose around brachytherapy sources is based on the AAPM TG-43 formalism, which generates the dose in a homogeneous water medium. Recently, AAPM TG-186 emphasized the importance of accounting for tissue heterogeneities. We have previously reported on a methodology where the absorbed dose in tissue can be obtained by multiplying the dose, calculated by the TG-43 formalism, by an inhomogeneity correction factor (ICF). In this work we make use of dual energy CT (DECT) images to extract ICF parameters. The advantage of DECT over conventional CT is that it eliminates the need for tissue segmentation as well as assignment of population based atomic compositions. DECT images of a heterogeneous phantom were acquired and the dose was calculated using both TG-43 and TG-43 [Formula: see text] formalisms. The results were compared to experimental measurements using Gafchromic films in the mid-plane of the phantom. For a seed implant configuration of 8 seeds spaced 1.5 cm apart in a cubic structure, the gamma passing score for 2%/2 mm criteria improved from 40.8% to 90.5% when ICF was applied to TG-43 dose distributions.


Assuntos
Braquiterapia/métodos , Imagens de Fantasmas , Radiometria/métodos , Planejamento da Radioterapia Assistida por Computador/métodos , Tomografia Computadorizada por Raios X/métodos , Algoritmos , Simulação por Computador , Humanos , Método de Monte Carlo , Neoplasias/radioterapia , Dosagem Radioterapêutica
2.
Opt Lett ; 26(14): 1081-3, 2001 Jul 15.
Artigo em Inglês | MEDLINE | ID: mdl-18049526

RESUMO

We report what is to our knowledge a record high value for an intrinsic two-photon absorption (TPA) cross section, sigma(2) = 11 x 10(-47)> cm>(4)> s photon(-1) molecule(-1), measured with femtosecond pulses in a new dendrimer molecule comprising 29 repeat units of 4, 4(?)-bis(diphenylamino)stilbene chromophore. We measure the dependence of TPA on excitation wavelength in three consecutive generations of the dendrimer and show that the maximum sigma(2) value increases faster than the total number of stilbene chromophores. This result indicates that it is possible to obtain even larger sigma(2) values in higher generations of this dendrimer family.

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