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- del Risco Norrlid, Lilián, et al.
(författare)
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Capabilities in the Nordic region for assessment of accidental uptake of radioiodine in emergency situations.
- 2014
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Ingår i: The 4th European Regional IRPA Congress.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Introduction The need for quantifying the uptake of radioiodine in thyroids has been repeatedly demonstrated following accidents. The aim of an early stage quick measurement is to identify the people who may have inhaled or ingested I-131 that imply the need for more extensive measurements and subsequent medical assessment. Objectives and methodology This work aims to evaluate the status of thyroid measurements capabilities in the Nordic region. The participating laboratories were offered the possibility of calibrating their systems with known and fully traceable activity of the I-131 simulator mock iodine (Ba133 + Cs137) in neck phantoms of three different sizes, adult, young and child. The laboratories have also received an unknown activity of mock iodine activity in a test neck phantom to measure and an emergency response scenario. The participants are required to report the result quickly, including an analysis regarding the committed organ dose due to the assumed intake and to describe the measurement procedure. Results The present in-vivo thyroid monitoring capabilities in the Nordic region are compiled. Given the variety of instruments calibrated, a guidance for the in-vivo determination of I-131 in thyroids is provided. This guidance is based on the measurement instructions that were circulated with the calibration phantoms and it includes the calibration factors for a list of the most frequent detectors. Among the variety of instruments are gamma cameras at hospitals, gamma spectrometers of different resolutions and handheld instruments of both spectrometric and count/dose rate capability. The detection limits for I131 attainable with the present resources are presented categorized per type of instrument. Also results of the intercomparison of measurements of I-131 activity, the estimated thyroid dose as well as compilation of dose assessment capacities are reported. Conclusions Prompt triage of many people regarding I-131 intake enable both the necessary early stage contamination control and the subsequent estimation of thyroid radiation doses. With proper calibration, many kinds of hand instruments can be used. Gamma cameras available in hospitals can also be an important resource in the context of I-131 measurements.
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- del Risco Norrlid, Lilián, 1969-
(författare)
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Modeling the Performance of a Hybrid Pixel Detector for Digital X-ray Imaging
- 2004
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The development of digital detectors for X-ray imaging in medical diagnostics receives an increasing amount of attention. The detector under development at the Department of Radiation Sciences at Uppsala University is a hybrid pixel detector, which consists of a semiconductor sensor mounted onto a readout chip. The readout chip is capable of performing photon counting and has an externally adjustable threshold.A simulation tool for the detector and a model applying the linear-systems transfer theory to X-ray hybrid pixel detectors have been developed. Also a characterization of the readout chip has been done. In order to estimate the potential of the detector for diagnostic radiology, we investigate the image quality using the spatial frequency dependent detective quantum efficiency (DQE). By means of the detector simulations, the influence of threshold setting, noise sources, level of exposure and charge sharing on the DQE have been studied. By means of the linear-systems theory, a single analytical expression is provided to obtain the DQE of a hybrid pixel detector.The method developed in this thesis will make it possible to optimize a detector design according to a particular medical application. It will also permit modifications and new features to be included without having to construct a full detector system.
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- del Risco Norrlid, Lilian, et al.
(författare)
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Nordic Intercomparison Campaign for Whole Body Counters – Evaluation of the Performance of the Facilities and Inventory of Regional Resources.
- 2012
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Ingår i: 13th International Congress of the International Radiation Protection Association (IRPA) in Glasgow, 13-18 May 2012.
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Konferensbidrag (refereegranskat)abstract
- Results of the regional intercomparison campaign conducted during 2010/2011 are presented and discussed. This activity was promoted in the framework of the Nordic Nuclear Safety Research (NKS) for regional cooperation in nuclear safety, radiation protection and emergency preparedness. The goals were to evaluate the quality status of whole body counting measurements by means of a proficiency test exercise, setting up an on-line library for the management of the use of calibration phantoms in the region and an inventory of the regional resources. The St. Petersburg whole body phantom (also known as IRINA), jointly owned by the Nordic countries, was circulated for the measurements together with two sets of fully traceable radioactive material (Cs137 and K40). This phantom can be built in six sizes and the choice for the phantom size was the adult size with 77,8 kg and 170,5 cm. Twenty one laboratories participated. The phantom circulated first among in-vivo laboratories situated at nuclear facilities, second priority was given to national authorities and laboratories with responsibilities within emergency response and lastly university hospitals or other research laboratories. A web based library for regional phantoms was set up containing the information on every phantom and its ”home” site. The online data updated after the completion of every loan event makes possible for the users to check online regarding availability/waiting time for the phantoms to borrow. The regional inventory of resources for in vivo measurements revealed that the whole body counting assets have been maintained compared to 2004, the last time an inventory of this kind was made. Both the field laboratories as the stationary ones are equipped with sophisticated whole-body counting systems with Ge-, NaI-detectors. The regional competence is good and retains experienced staff but a new generation is coming that needs training and exchange of experiences, which emphazises the importance of keeping the practice of intercomparison exercises.
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- Edling, Fredrik, et al.
(författare)
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Performance of a chip for hybrid pixel detectors with two counters for X-ray imaging
- 2004
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Ingår i: Proceedings of the 5th International Workshop on Radiation Imaging Detectors. - : Elsevier BV. ; , s. 215-220
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Konferensbidrag (refereegranskat)abstract
- A semiconductor hybrid pixel detector for dynamic X-ray imaging is developed. The detector, called DIXI, consists of a semiconductor sensor mounted onto a readout chip. A detector module with a silicon sensor is currently being assembled with the use of anisotropic conductive film as interconnection between the sensor and the readout chip. The basic building block of the detector is in size and consists of 992 square pixel cells arranged in 31 columns and 32 rows. The pixels have a side of . The readout chip is capable of performing photon counting and has an externally adjustable threshold. The readout chip has been characterised by charge injection in the absence of a sensor. The threshold dispersion is measured to 365 e− for hole collection. Even if the chip was not originally designed for electron collection a threshold dispersion of 1650 e− has been achieved. Two counters are implemented in every single pixel cell and the threshold can be changed from one image to the next in order to select different parts of the X-ray spectrum.
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- Norrlid, Lilian del Risco, et al.
(författare)
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Imaging of small children prototype for photon counting tomosynthesis
- 2009
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Ingår i: Medical Imaging 2009. - : SPIE-Intl Soc Optical Eng.
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Konferensbidrag (refereegranskat)abstract
- We present data on a first prototype for photon counting tomosynthesis imaging of small children, which we call photoncounting tomosynthesis (PCT). A photon counting detector can completely eliminate electronic noise, which makes it ideal for tomosynthesis because of the low dose in each projection. Another advantage is that the detector allows for energy sensitivity in later versions, which will further lower the radiation dose. In-plane resolution is high and has been measured to be 5lp/mm, at least 4 times better than in CT, while the depth resolution was significantly lower than typical CT resolution. The image SNR decreased from 30 to 10 for a detail of 10 mm depth in increasing thickness of PMMA from 10 to 80 mm. The air kerma measured for PCT was 5.2 mGy, which leads to an organ dose to the brain of approximately 0.7 mGy. This dose is 96 % lower than a typical CT dose. PCT can be appealing for pediatric imaging since young children have an increased sensitivity to radiation induced cancers. We have acquired post mortem images of a newborn with the new device and with a state-of-the-art CT and compared the diagnostic information and dose levels of the two modalities. The results are promising but more work is needed to provide input to a next generation prototype that would be suitable for clinical trials.
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- Nyander Poulsen, Asser, et al.
(författare)
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Assessment of accidental uptake of iodine-131 in emergency situations
- 2014
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The need for quantifying the uptake of radioiodine (131I) in thyroids in emergency situations has repeatedly been demonstrated. With early stage measurements people who may have inhaled or ingested amounts of 131I can be identified and the need for more extensive measurements and/or subsequent medical assessment can be evaluated. The report presents the outcome from the activity THYROID in which calibrations of thyroid monitoring equipment in the Nordic countries were harmonized. A total of 38 sites in Scandinavia were identified holding equipment usable for screening for thyroid 131I contamination. Different instrument types can be used in an emergency situation as long as they are properly calibrated. The activity enabled to evaluate the regional preparedness regarding thyroid personal monitoring.
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- Poulsen Nyander, A, et al.
(författare)
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Thyroidsem: Assessment of accidential uptake of radioiodine in emergency situation.
- 2014
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- This document constitutes a follow-up report upon the one-day seminar held in Copenhagen at 29. September 2014 about population monitoring of I-131 uptake in the population during emergency situations in the Nordic countries (THYROID). Measurement techniques, dose assessment and preparedness were discussed. A questionnaire was used to collect feedback from participants in order identify needs for future improvements. In conlusion, calibrations with actual I-131 should be considered, and a standard template for reporting and calculations are requested.
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