941 resultados para Dose de Referência


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To establish an education and training programme for the reduction of CT radiation doses and to assess this programme's efficacy.

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This review summarizes current evidence based on pertinent literature on low-dose computed tomography angiography (CTA) of the body. Various strategies for optimizing CTA protocols with the aim to lower the radiation dose while maintaining the diagnostic accuracy of the examination are summarized. To date, various publications have demonstrated that CTA of the body can be performed at a low radiation dose while providing high quality information. Nevertheless, a number of questions still need to be answered, including the optimal combination of tube voltage and tube current settings, as well as the appropriate protocol parameters in relation to the body physiognomy and the specific body region imaged.

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The rapid technical advances in computed tomography have led to an increased number of clinical indications. Unfortunately, at the same time the radiation exposure to the population has also increased due to the increased total number of CT examinations. In the last few years various publications have demonstrated the feasibility of radiation dose reduction for CT examinations with no compromise in image quality and loss in interpretation accuracy. The majority of the proposed methods for dose optimization are easy to apply and are independent of the detector array configuration. This article reviews indication-dependent principles (e.g. application of reduced tube voltage for CT angiography, selection of the collimation and the pitch, reducing the total number of imaging series, lowering the tube voltage and tube current for non-contrast CT scans), manufacturer-dependent principles (e.g. accurate application of automatic modulation of tube current, use of adaptive image noise filter and use of iterative image reconstruction) and general principles (e.g. appropriate patient-centering in the gantry, avoiding over-ranging of the CT scan, lowering the tube voltage and tube current for survey CT scans) which lead to radiation dose reduction.

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To intraindividually compare a low-tube-voltage (80 kVp), high-tube-current (675 mA) computed tomographic (CT) technique with a high-tube-voltage (140 kVp) CT protocol for the detection of pancreatic tumors, image quality, and radiation dose during the pancreatic parenchymal phase.

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To investigate whether an adaptive statistical iterative reconstruction (ASIR) algorithm improves the image quality at low-tube-voltage (80-kVp), high-tube-current (675-mA) multidetector abdominal computed tomography (CT) during the late hepatic arterial phase.

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The effect of copper (Cu) filtration on image quality and dose in different digital X-ray systems was investigated. Two computed radiography systems and one digital radiography detector were used. Three different polymethylmethacrylate blocks simulated the pediatric body. The effect of Cu filters of 0.1, 0.2, and 0.3 mm thickness on the entrance surface dose (ESD) and the corresponding effective doses (EDs) were measured at tube voltages of 60, 66, and 73 kV. Image quality was evaluated in a contrast-detail phantom with an automated analyzer software. Cu filters of 0.1, 0.2, and 0.3 mm thickness decreased the ESD by 25-32%, 32-39%, and 40-44%, respectively, the ranges depending on the respective tube voltages. There was no consistent decline in image quality due to increasing Cu filtration. The estimated ED of anterior-posterior (AP) chest projections was reduced by up to 23%. No relevant reduction in the ED was noted in AP radiographs of the abdomen and pelvis or in posterior-anterior radiographs of the chest. Cu filtration reduces the ESD, but generally does not reduce the effective dose. Cu filters can help protect radiosensitive superficial organs, such as the mammary glands in AP chest projections.

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CT pulmonary angiography is the currently accepted standard in ruling out acute pulmonary embolism. Issues of radiation dose received by patients via CT have been extensively disputed by radiologists and reported by the media. In recent years there has been considerable research performed to find ways for reducing radiation exposure from CT. Herein, we will discuss specific measures that have been shown to be valuable for CT pulmonary angiography. The limitations and the potential benefits of reduced CT peak tube kilovoltage will be detailed as this method is capable of reducing both radiation exposure and iodine load to the patient simultaneously. We discuss some of the emerging tools, which will hopefully play a significant role in wider acceptance of low-dose CT pulmonary angiography protocols.

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recombinant activated factor VII (rFVIIa) is used off-label for massive bleeding. There is no convincing evidence of the benefits of this practice and the minimal effective dose is unknown. The aim of the study was to evaluate our in-house guideline recommending a low dose of 60 μg/kg for off-label use of rFVIIa.

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The production of epithelial neutrophil activating peptide-78 (NA-78) and the interleukins IL-8 and IL-6 by endometrial stromal cells is stimulated by pro-inflammatory interleukin-1 (IL-1) and tumour necrosis factor-α (TNF-α). IL-8 is suggested to play a role in the pathogenesis of endometriosis, and in these women the peritoneal fluid concentrations of ENA-78 and IL-8 are increased. TNF-α has been tested together with interferon-γ because of their cooperative stimulation of IL-6. The release of IL-8, however, is inhibited with increasing interferon levels. The aim of the study was the analysis of the production of ENA-78, IL-6 and IL-8 by cultured human endometrial stromal cells in the presence of varying concentrations of IL-1β, TNF-α, and interferon-γ.

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Receptors for luteinizing hormone-releasing hormone (LHRH) can be utilized for targeted chemotherapy of cytotoxic LHRH analogs. The compound AEZS-108 (previously AN-152) consists of [D-Lys?]LHRH linked to doxorubicin. The objectives of this first study in humans with AESZ-108 were to determine the maximum tolerated dose and to characterize the dose-limiting toxicity, pharmacokinetics, preliminary efficacy, and hormonal effects.

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The temporal bone is ideal for low-dose CT because of its intrinsic high contrast. The aim of this study was to retrospectively evaluate image quality and radiation doses of a new low-dose versus a standard high-dose pediatric temporal bone CT protocol and to review dosimetric data from the literature.

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The purpose of this experimental study was to investigate the effect of tube tension reduction on image contrast and image quality in pediatric temporal bone computed tomography (CT).