Search results for "radiation sensitivity"

Spontaneous and Radiation-Induced Chromosome Aberrations in Primary Fibroblasts of Patients With Pediatric First and Second Neoplasms

2020

Frontiers in oncology 10, 1338 (2020). doi:10.3389/fonc.2020.01338

Blood flow and metabolic microenvironment of brain tumors

1994

Summarizing thesein vivo data in the context of brain tumor therapy, the following aspects are of particular importance: Low and heterogeneous tumor blood flow may — in addition to the limiting effects of the blood-brain barrier — result in compromised delivery of drugs from blood to the tissue. Low tumor pO2 reduces sensitivity to standard radiation and ‘O2-dependent’ anticancer drugs. Treatment efficacy may be further altered by changes of tumor pH. Particularly acidosis can decrease radiation sensitivity and modulate the cytotoxicity of anticancer drugs. In the following presentations, these aspects will be discussed regardingin vivo data obtained with positron emission tomography.

Effect of oxygen deficiency on the radiation sensitivity of sol-gel Ge-doped amorphous SiO2

2008

We report experimental investigation by electron paramagnetic resonance (EPR) measurements of room temperature γ-ray irradiation effects in sol-gel Ge doped amorphous SiO2. We used materials with Ge content from 10 up to 104 part per million (ppm) mol obtained with different preparations. These latter gave rise to samples characterized by different extents of oxygen deficiency, estimated from the absorption band at ~5.15 eV of the Ge oxygen deficient centers (GeODC(II)). The irradiation at doses up to ~400 kGy induces the E'-Ge, Ge(1) and Ge(2) paramagnetic centers around g ~ 2 with concentrations depending on Ge and on GeODC(II) content. We found correlation between Ge(2) and GeODC(II) con…

Influence of the manufacturing process on the radiation sensitivity of fluorine-doped silica-based optical fibers

2011

International audience; In this work, we analyze the origins of the observed differences between the radiation sensitivities of fluorine-doped optical fibers made with different fabrication processes. We used several experimental techniques, coupling in situ radiation-induced absorption measurements with post mortem confocal microscopy luminescence measurements. Our data showed that the silica intrinsic defects are generated both from precursor sites and from strained regular Si-O-Si linkages. Our work also provides evidence for the preponderant role of the chlorine in determining the optical losses at about 3.5 eV. The results show that the manufacturing process of these fibers strongly af…

The Role of Oxygen Tension Distribution on the Radiation Response of Human Breast Carcinoma

1994

The response of tumors to radiation is heterogeneous even in animal tumor systems where tumors all originate from the same cell culture, are implanted in genetically similar age-matched animals in a constant anatomic locationl. Hence great heterogeneity of response exists even in situations where intrinsic genetic or epigenetic factors are minimally variable. Several metabolic factors are known to influence the probability of tumor control after radiation. These metabolic factors are also known to vary widely between tumors in humans2,3 and even in animal tumor models. Heterogeneous variables include tumor oxygen tension distribution, glutathione content, glucose delivery and utilization ra…

Radiation hardening techniques for rare-earth-based optical fibers and amplifiers

2012

Er/Yb doped fibers and amplifiers have been shown to be very radiation sensitive, limiting their integration in space. We present an approach including successive hardening techniques to enhance their radiation tolerance. The efficiency of our approach is demonstrated by comparing the radiation responses of optical amplifiers made with same lengths of different rare-earth doped fibers and exposed to gamma-rays. Previous studies indicated that such amplifiers suffered significant degradation for doses exceeding 10 krad. Applying our techniques significantly enhances the amplifier radiation resistance, resulting in a very limited degradation up to 50 krad. Our optimization techniques concern …

Quantification of Radiation Biomarkers in Leukocytes of Breast Cancer Patients Treated with Different Modalities of 3D-CRT or IMRT

2016

The goal of this study was to determine whether the quantification of radiation biomarkers in peripheral leukocytes of 111 breast cancer patients after adjuvant treatment with different modalities of three-dimensional conformal radiation therapy (3D-CRT) or intensity-modulated radiation therapy (IMRT) revealed any difference in the patients' radiation burden by out-of-field doses and an associated risk of second malignancies. Whole-breast radiation therapy was performed by 3D-CRT using either a hard wedge (n = 32) or a virtual wedge (n = 49) at dose rates of 3 and 6 Gy per min each. Patients receiving additional radiotherapy to lymph nodes were treated by 3D-CRT (n = 21) or IMRT (n = 9). DN…

2019

Purpose: To summarize existing knowledge and to understand individual response to radiation exposure, the MELODI Association together with CONCERT European Joint Programme has organized a workshop in March 2018 on radiation sensitivity and susceptibility.Methods: The workshop reviewed the current evidence on this matter, to inform the MELODI Strategic Research Agenda (SRA), to determine social and scientific needs and to come up with recommendations for suitable and feasible future research initiatives to be taken for the benefit of an improved medical diagnosis and treatment as well as for radiation protection.Results: The present paper gives an overview of the current evidence in this fie…

Radiation Response of Ce-Codoped Germanosilicate and Phosphosilicate Optical Fibers

2016

We report an experimental investigation on the effects of Ce-codoping in determining the radiation response of germanosilicate and phosphosilicate Optical Fibers (OFs) in the UV-Visible domain and up to doses of $1~\hbox{MGy}({\rm SiO}_{2})$ . We show that the addition of Ce strongly impacts the Radiation Induced Attenuation (RIA) of both types of fibers. In the first case the radiation induced losses increase, whereas in the second one decrease. By combining the online RIA measurements with the Electron Paramagnetic Resonance (EPR) ones, we are able to infer the basic microscopic mechanisms taking place under irradiation, which involve the cerium codopant and some of the known Ge-related o…