Search results for "RADIATION"
showing 10 items of 5298 documents
Temperature changes induced by 809-nm GaAlAs laser at the implant-bone interface during simulated surface decontamination
2003
The aim of the study was to investigate temperature changes at the implant-bone interface during simulated implant surface decontamination with a 809-nm gallium-aluminium-arsenid (GaAlAs) semiconductor laser. Stepped cylinder implants with a diameter of 3.8 mm and a length of 11 mm with two different surfaces (sand-blasted and acid etched, and hydroxyapatite-coated) were inserted into bone blocks cut from freshly resected pig femurs. Access holes of 0.5 mm were drilled into the bone, to allow K-type thermocouples to contact periimplant bone in different parts of the cavity. An artificial periimplant bone defect provided access for laser irradiation in the coronal third. A 600-micrometer opt…
Radiation transmission data for radionuclides and materials relevant to brachytherapy facility shielding
2008
To address the limited availability of radiation shielding data for brachytherapy as well as some disparity in existing data, Monte Carlo simulation was used to generate radiation transmission data for 60Co, 137CS, 198Au, 192Ir 169Yb, 170Tm, 131Cs, 125I, and 103pd photons through concrete, stainless steel, lead, as well as lead glass and baryte concrete. Results accounting for the oblique incidence of radiation to the barrier, spectral variation with barrier thickness, and broad beam conditions in a realistic geometry are compared to corresponding data in the literature in terms of the half value layer (HVL) and tenth value layer (TVL) indices. It is also shown that radiation shielding calc…
Determination of chromophore distribution in skin by spectral imaging
2012
Possibilities to determine chromophore distribution in skin by spectral imaging were explored. Simple RGB sensor devices were used for image acquisition. Totally 200 images of 40 different bruises of 20 people were obtained in order to map chromophores bilirubin and haemoglobin. Possibilities to detect water in vitro and in vivo were estimated by using silicon photodetectors and narrow band LEDs. The results show that it is possible to obtain bilirubin and haemoglobin distribution maps and observe changes of chromophore parameter values over time by using a simple RGB imaging device. Water in vitro was detected by using differences in absorption at 450 nm and 950 nm, and 650 nm and 950 nm.
Efficacy of NaOCl/H2O2irrigation and GaAlAs laser in decontamination of root canals in vitro
2003
Background and Objectives To investigate the bactericidal effect of an 809 nm semiconductor laser alone, and in combination with NaOCl/H2O2 irrigation in root canals in vitro. Study Design/Materials and Methods A total of 72 human single-rooted teeth extracted for periodontal reasons were included. The crowns were removed, the roots shortened to a length of 12 mm, and the canals enlarged up to an apical size of #50 file. The specimens were autoclaved and incubated with a suspension of Streptococcus sanguinis (ATCC 10556). Laser irradiation was performed on a PC-controlled XY translation stage. A 200 micron optic fiber was used. Twelve specimens were irradiated at a power output of 1.5, 3.0,…
Broad-beam transmission data for new brachytherapy sources, Tm-170 and Yb-169
2005
The characteristics of the radionuclides (170)Tm and (169)Yb are highly interesting for their use as high dose-rate brachytherapy sources. The introduction of brachytherapy equipment containing these sources will lead to smaller required thicknesses of the materials used in radiation protection barriers compared with the use of conventional sources such as (192)Ir and (137)Cs. The purpose of this study is to determine the required thicknesses of protection material for the design of the protecting walls. Using the Monte Carlo method, transmission data were derived for broad-beam geometries through lead and concrete barriers, from which the first half value layer and tenth value layer are ob…
Bonnes pratiques de radiothérapie guidée par l’image
2015
Image-guided radiotherapy (IGRT) aims to take into account the anatomical variations occurring during the course of radiotherapy, by direct or indirect visualization of the target volume followed by a corrective action. The movements of the target, or at least the set-up errors are corrected by moving the treatment table, corresponding to the simplest and most validated IGRT modality in a standard practice. The deformations of the target volume and organs at risk are however much more common, and unfortunately much more complicated to consider, requiring multiple planning before or during the treatment, corresponding to the adaptive radiotherapy strategies. The planning target volume must b…
Head and Neck Paragangliomas
2016
Head and neck paragangliomas are highly vascularized neuroendocrine tumors derived from the extra-adrenal paraganglia of the autonomic nervous system. These tumors may occur either sporadically or in the context of a hereditary familial tumor syndrome, and multifocal presentations are observed, particularly in hereditary cases. Hereditary paragangliomas are mostly caused by mutations in the succinate dehydrogenase complex genes. Early imaging, with ultrasonography of the neck and magnetic resonance imaging (MRI) of the skull base, is essential for localizing and assessing the extent of the tumor, as well as for precise planning of the treatment approach. Views regarding the treatment of cho…
Prognostic factors on surgically and non-surgically treated oral squamous cell carcinoma: Advances in survival in fifteen years of follow up
2021
Background Retrospectively to evaluate the influence of radiochemotherapy (RCT) in the treatment of surgically and non-surgically treated Oral Squamous Cell Carcinoma (OSCC). Material and Methods We analysed 934 patients treated in Hospital Haroldo Juacaba (2000-2014; 15 years of study) by extraction of data type of cancer, localization of tumour, sex, age, race, education level, risk factors (smoking and alcohol use), year of diagnosis, TNM stage, therapeutic approach, health system used (public or private) and overall survival (OS). Surgically and non-surgically treated OSCC were compared by chi-square and Fisher's exact tests, and their prognostic factors were analysed by log-rank Mantel…
Adjuvant versus Neoadjuvant Radiochemotherapy for Locally Advanced Rectal Cancer A Progress Report of a Phase-III Randomized Trial (Protocol CAO/ARO/…
2001
The standard treatment for patients with clinically resectable rectal cancer is surgery. Postoperative radiochemotherapy is recommended for patients with advanced disease (pT3/4 or pN+). In recent years, encouraging results of preoperative radiotherapy have been reported. This prospective randomized phase-III trial (CAO/ARO/AIO-94) compares the efficacy of neoadjuvant radiochemotherapy to standard postoperative radiochemotherapy. We report on the design of the study and first results with regard to toxicity of radiochemotherapy and postoperative morbidity. Patients and Methods: Patients with locally advanced operable rectal cancer (uT3/4 or uN+, Mason CS III/IV) were randomly assigned to pr…