نتایج جستجو برای: چشمۀ 252cf at
تعداد نتایج: 3719119 فیلتر نتایج به سال:
زمینه و هدف: امروزه استفاده از شبیهسازی برای تعیین دقیق پارامترهای دزیمتری اجتنابناپذیر است. در این مطالعه پارامترهای دزیمتری 252Cf-AT بهعنوان یک چشمه نوترونی براکی تراپی با استفاده از شبیهسازی مونتکارلو محاسبه میشود که در درمان برخی از سرطانهای رحم و تومورهای مغزی کاربرد دارد. روش بررسی: ویژگیهای فیزیکی و هندسی چشمه کالیفورنیوم-252 مدل AT ب...
AIMS AND BACKGROUND Neutron rays produce high linear energy transfer radiation, which has particular radiobiological characteristics. The aim of the study was to observe the curative effects and complications of external irradiation combined with californium-252 (252Cf) neutron intraluminal brachytherapy for treatment of cervical carcinoma. METHODS AND STUDY DESIGN From December 2000 to Decem...
A novel tissue-equivalent proportional counter (TEPC) based on a gas electron multiplier (GEM) for measuring H*(10) for neutrons was designed and constructed. The pulse height spectra (PHS) of two different neutron sources (a 252Cf source and a AmBe source) were measured using the new TEPC. The measurements were made with the TEPC filled with two different gases (10P gas and a propane-based tis...
Introduction: The commercial 252Cf sources are too large in size and clinical applications of neutron brachytherapy (NBT) are limited to a small number of intracavitary treatments of cervical cancers. Recently, under the Cooperative Research and Development Agreement (CRADA) with Isotron Inc., the Oak Ridge National Laboratory (ORNL) encapsulated a new medical 252Cf sources, c...
Introduction:The commercial 252Cf sources are too large in size and clinical applications of neutronbrachytherapy (NBT) are limited to a small number of intracavitary treatments of cervical cancers. Recently, under the Cooperative Research and Development Agreement (CRADA) with Isotron Inc., the Oak Ridge National Laboratory (ORNL) encapsulated a new medical 252Cf sources, cal...
252Cf plasma desorption mass spectrometry has been used in the characterization of more than 100 synthetic porphyrins ranging in mass from 614 u for tetraphenylporphyrin to over 2000 u for some porphyrin model systems. In virtually every case, 252Cf plasma desorption mass spectrometry yielded an intense ionized molecule ion [M.+ and/or (M+H)+], irrespective of the groups appended to the porphyr...
A Prompt Gamma Ray Neutron Activation Analysis (PGNAA) system, incorporating an isotopic neutron source has been simulated using the MCNPX Monte Carlo code. In order to improve the signal to noise ratio different collimators and a filter were placed between the neutron source and the object. The effect of the positioning of the neutron beam and the detector relative to the object has been studi...
The relative biological effectiveness (RBE) of 252Cf neutrons and synchrotron-generated high-energy charged particles for mutation induction was evaluated as a function of linear energy transfer (LET), using the loss of heterozygosity for wing-hair mutations and the reversion of the mutant white-ivory eye-color in Drosophila melanogaster. Loss of heterozygosity for wing-hair mutations results p...
This study was undertaken to investigate the biological effect of monoenergetic neutrons on human lymphocyte DNA and chromosomes. Monoenergetic neutrons of 2.3, 1.0, 0.79, 0.57, 0.37 and 0.186 MeV were generated, and 252Cf neutrons and 60Co gamma-rays were also used for comparison. Biological effect was evaluated two ways. The RBE values with the comet assay were estimated as 6.3 and 5.4 at 0.3...
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