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| 2. |
- García Balcaza, V, et al.
(författare)
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Fast Monte Carlo codes for occupational dosimetry in interventional radiology
- 2021
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Ingår i: Physica Medica. - : Elsevier BV. - 1120-1797. ; 85, s. 166-174
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Tidskriftsartikel (refereegranskat)abstract
- PURPOSE: Interventional radiology techniques cause radiation exposure both to patient and personnel. The radiation dose to the operator is usually measured with dosimeters located at specific points above or below the lead aprons. The aim of this study is to develop and validate two fast Monte Carlo (MC) codes for radiation transport in order to improve the assessment of individual doses in interventional radiology. The proposed methodology reduces the number of required dosemeters and provides immediate dose results.METHODS: Two fast MC simulation codes, PENELOPE/penEasyIR and MCGPU-IR, have been developed. Both codes have been validated by comparing fast MC calculations with the multipurpose PENELOPE MC code and with measurements during a realistic interventional procedure.RESULTS: The new codes were tested with a computation time of about 120 s to estimate operator doses while a standard simulation needs several days to obtain similar uncertainties. When compared with the standard calculation in simple set-ups, MCGPU-IR tends to underestimate doses (up to 5%), while PENELOPE/penEasyIR overestimates them (up to 18%). When comparing both fast MC codes with experimental values in realistic set-ups, differences are within 25%. These differences are within accepted uncertainties in individual monitoring.CONCLUSION: The study highlights the fact that computational dosimetry based on the use of fast MC codes can provide good estimates of the personal dose equivalent and overcome some of the limitations of occupational monitoring in interventional radiology. Notably, MCGPU-IR calculates both organ doses and effective dose, providing a better estimate of radiation risk.
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| 3. |
- O'Connor, U, et al.
(författare)
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Feasibility study of computational occupational dosimetry : evaluating a proof-of-concept in an endovascular and interventional cardiology setting
- 2022
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Ingår i: Journal of Radiological Protection. - : IOP Publishing. - 1361-6498 .- 0952-4746. ; 42:4
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Tidskriftsartikel (refereegranskat)abstract
- Individual monitoring of radiation workers is essential to ensure compliance with legal dose limits and to ensure that doses are As Low As Reasonably Achievable. However, large uncertainties still exist in personal dosimetry and there are issues with compliance and incorrect wearing of dosimeters. The objective of the PODIUM (Personal Online Dosimetry Using Computational Methods) project was to improve personal dosimetry by an innovative approach: the development of an online dosimetry application based on computer simulations without the use of physical dosimeters. Occupational doses were calculated based on the use of camera tracking devices, flexible individualised phantoms and data from the radiation source. When combined with fast Monte Carlo simulation codes, the aim was to perform personal dosimetry in real-time. A key component of the PODIUM project was to assess and validate the methodology in interventional radiology workplaces where improvements in dosimetry are needed. This paper describes the feasibility of implementing the PODIUM approach in a clinical setting. Validation was carried out using dosimeters worn by Vascular Surgeons and Interventional Cardiologists during patient procedures at a hospital in Ireland. Our preliminary results from this feasibility study show acceptable differences of the order of 40% between calculated and measured staff doses, in terms of the personal dose equivalent quantity Hp(10), however there is a greater deviation for more complex cases and improvements are needed. The challenges of using the system in busy interventional rooms have informed the future needs and applicability of PODIUM. The availability of an online personal dosimetry application has the potential to overcome problems that arise from the use of current dosimeters. In addition, it should increase awareness of radiation protection among staff. Some limitations remain and a second phase of development would be required to bring the PODIUM method into operation in a hospital setting. However, an early prototype system has been tested in a clinical setting and the results from this two-year proof-of-concept PODIUM project are very promising for future development.
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| 4. |
- Almén, A, et al.
(författare)
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Personal Dosimetry Using Monte-Carlo Simulations For Occupational Dose Monitoring In Interventional Radiology : The Results Of A Proof Of Concept In A Clinical Setting
- 2021
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Ingår i: Radiation Protection Dosimetry. - : Oxford University Press (OUP). - 1742-3406 .- 0144-8420. ; 195:44624, s. 391-398
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Tidskriftsartikel (refereegranskat)abstract
- Exposure levels to staff in interventional radiology (IR) may be significant and appropriate assessment of radiation doses is needed. Issues regarding measurements using physical dosemeters in the clinical environment still exist. The objective of this work was to explore the prerequisites for assessing staff radiation dose, based on simulations only. Personal dose equivalent, Hp(10), was assessed using simulations based on Monte Carlo methods. The position of the operator was defined using a 3D motion tracking system. X-ray system exposure parameters were extracted from the x-ray equipment. The methodology was investigated and the simulations compared to measurements during IR procedures. The results indicate that the differences between simulated and measured staff radiation doses, in terms of the personal dose equivalent quantity Hp(10), are in the order of 30-70 %. The results are promising but some issues remain to be solved, e.g. an automated tracking of movable parts such as the ceiling-mounted protection shield.
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| 5. |
- Almén, Markus Sällman, et al.
(författare)
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The obesity gene, TMEM18, is of ancient origin, found in majority of neuronal cells in all major brain regions and associated with obesity in severely obese children
- 2010
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Ingår i: BMC Medical Genetics. - : Springer Science and Business Media LLC. - 1471-2350. ; 11, s. 58-
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: TMEM18 is a hypothalamic gene that has recently been linked to obesity and BMI in genome wide association studies. However, the functional properties of TMEM18 are obscure. METHODS: The evolutionary history of TMEM18 was inferred using phylogenetic and bioinformatic methods. The gene's expression profile was investigated with real-time PCR in a panel of rat and mouse tissues and with immunohistochemistry in the mouse brain. Also, gene expression changes were analyzed in three feeding-related mouse models: food deprivation, reward and diet-induced increase in body weight. Finally, we genotyped 502 severely obese and 527 healthy Swedish children for two SNPs near TMEM18 (rs6548238 and rs756131). RESULTS: TMEM18 was found to be remarkably conserved and present in species that diverged from the human lineage over 1500 million years ago. The TMEM18 gene was widely expressed and detected in the majority of cells in all major brain regions, but was more abundant in neurons than other cell types. We found no significant changes in the hypothalamic and brainstem expression in the feeding-related mouse models. There was a strong association for two SNPs (rs6548238 and rs756131) of the TMEM18 locus with an increased risk for obesity (p = 0.001 and p = 0.002). CONCLUSION: We conclude that TMEM18 is involved in both adult and childhood obesity. It is one of the most conserved human obesity genes and it is found in the majority of all brain sites, including the hypothalamus and the brain stem, but it is not regulated in these regions in classical energy homeostatic models.
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| 6. |
- Jacobsson, Josefin A., et al.
(författare)
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Detailed Analysis of Variants in FTO in Association with Body Composition in a Cohort of 70-Year-Olds Suggests a Weakened Effect among Elderly
- 2011
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Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 6:5, s. e20158-
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Tidskriftsartikel (refereegranskat)abstract
- Background: The rs9939609 single-nucleotide polymorphism (SNP) in the fat mass and obesity (FTO) gene has previously been associated with higher BMI levels in children and young adults. In contrast, this association was not found in elderly men. BMI is a measure of overweight in relation to the individuals' height, but offers no insight into the regional body fat composition or distribution. Objective: To examine whether the FTO gene is associated with overweight and body composition-related phenotypes rather than BMI, we measured waist circumference, total fat mass, trunk fat mass, leg fat mass, visceral and subcutaneous adipose tissue, and daily energy intake in 985 humans (493 women) at the age of 70 years. In total, 733 SNPs located in the FTO gene were genotyped in order to examine whether rs9939609 alone or the other SNPs, or their combinations, are linked to obesity-related measures in elderly humans. Design: Cross-sectional analysis of the Prospective Investigation of the Vasculature in Uppsala Seniors (PIVUS) cohort. Results: Neither a single SNP, such as rs9939609, nor a SNP combination was significantly linked to overweight, body composition-related measures, or daily energy intake in elderly humans. Of note, these observations hold both among men and women. Conclusions: Due to the diversity of measurements included in the study, our findings strengthen the view that the effect of FTO on body composition appears to be less profound in later life compared to younger ages and that this is seemingly independent of gender.
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| 7. |
- Morcos, Sameh K., et al.
(författare)
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Reducing the risk of iodine-based and MRI contrast media administration : recommendation for a questionnaire at the time of booking
- 2008
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Ingår i: European Journal of Radiology. - : Elsevier BV. - 0720-048X .- 1872-7727. ; 66:2, s. 225-229
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents a practical questionnaire to be used when a contrast medium examination is requested. The questionnaire is based on the guidelines from the European Society of Urogenital Radiology. Its aim is to identify patients at increased risk of clinically relevant renal and non-renal adverse reactions to iodine-based and MRI contrast agents. The questionnaire should be completed by the referring physician when the examination is requested.
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| 8. |
- Sällman Almén, Markus, et al.
(författare)
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Determination of the obesity-associated gene variants within the entire FTO gene by ultra-deep targeted sequencing in obese and lean children.
- 2013
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Ingår i: International Journal of Obesity. - : Springer Science and Business Media LLC. - 0307-0565 .- 1476-5497. ; 37:3, s. 424-431
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Tidskriftsartikel (refereegranskat)abstract
- Background:The Fat mass and obesity-associated gene (FTO) was the first gene reliably associated with body mass index in genome-wide association studies on a population level. At present, the genetic variations within the FTO gene are still the common variants that have the largest influence on body mass index.Methods:In the current study, we amplified the entire FTO gene, in total 412 Kbp, in over 200 long-range PCR fragments from each individual, from 524 severely obese and 527 lean Swedish children, and sequenced the products as two DNA pools using massive parallel sequencing (SOLiD).Results:The sequencing achieved very high coverage (median 18 000 reads) and we detected and estimated allele frequencies for 705 single nucleotide polymorphisms (SNPs) (19 novel) and 40 indels (24 novel) using a sophisticated statistical approach to remove false-positive SNPs. We identified 19 obesity-associated SNPs within intron one of the FTO gene, and validated our findings with genotyping. Ten of the validated obesity-associated SNPs have a stronger obesity association (P<0.007) than the commonly studied rs9939609 SNP (P<0.012).Conclusions:This study provides a comprehensive obesity-associated variation map of FTO, identifies novel lead SNPs and evaluates putative causative variants. We conclude that intron one is the only region within the FTO gene associated with obesity, and finally, we establish next generation sequencing of pooled DNA as a powerful method to investigate genetic association with complex diseases and traits.
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| 9. |
- Almén, A., et al.
(författare)
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Radiological protection of foetuses and breast-fed children of occupationally exposed women in nuclear medicine - Challenges for hospitals
- 2017
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Ingår i: Physica Medica. - : Elsevier BV. - 1120-1797. ; 43, s. 172-177
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Tidskriftsartikel (refereegranskat)abstract
- This paper describes issues of concern for protecting foetuses and breast-fed children of occupationally exposed women in nuclear medicine from unnecessary exposure of ionising radiation. The protection principle is to ensure the same level of protection for the foetus and child as for the general public. Therefore international radiation protection standards recommend a dose constraint of 1. mSv to a foetus during the remaining time of pregnancy after it is known/declared and a yearly dose constraint of 1. mSv to a breast-fed child. It is not self-evident how to guarantee this level of radiation protection.The exposure situation in nuclear medicine is complex. Exploring existing reported occupational exposure levels suggests great variability between work tasks and facilities. The standards and guidelines found give no detailed advice. Therefore each facility needs to systematically review external and internal exposure levels in order to plan appropriate protection measures and issue their own guidelines and rules. One strategy might be that each facility defines tasks that do not require any restrictions and lists such duties that are not suitable to do when pregnant or breastfeeding, taking also potential exposure levels into consideration. This paper gives examples of such types of work.Information to the staff about the necessity of declaring pregnancy or breastfeeding is of fundamental importance. The internal policies issued by the hospital management should make clear the basis for taking care of pregnant and breastfeeding employees.
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| 10. |
- Almén, A, et al.
(författare)
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The radiation dose to children from X-ray examinations of the pelvis and the urinary tract
- 1995
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Ingår i: British Journal of Radiology. - : British Institute of Radiology. - 0007-1285 .- 1748-880X. ; 68:810, s. 13-604
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Tidskriftsartikel (refereegranskat)abstract
- X-ray examinations of the pelvis and the urinary tract are frequent examinations of children, in which a large part of the trunk is irradiated. The irradiated volume contains many of the most radiation sensitive organs and tissues. The absorbed dose to children during the examination was estimated from measurements with a dose-area product meter and thermoluminescent dosemeters (TLDs). Entrance surface dose and the dose-area product results are presented. Conversion factors between the entrance surface dose and the organ dose were derived. The energy imparted, organ dose and effective dose were determined. The entrance surface dose for one single exposure varied between 0.32 mGy and 8.6 mGy for the urinary tract examination and between 0.26 mGy and 2.89 mGy per exposure for the pelvis examination. These variations are mainly influenced by the body size of the patient. The number of images taken during one examination varied. For the urinary tract investigation, the average number of exposures was six, while the corresponding number for the pelvis examination was two. The average effective dose for a typical urinary tract investigation ranged from 0.9 mSv to 8.5 mSv and from 0.3 mSv to 1.4 mSv for the pelvis examination. The radiation dose depends greatly on the body size. The recommendations to present the results in relation to age have been followed; however, the variation of body size even within each specified age range is significant. It is suggested that doses should be quoted in relation to a more critical parameter than age.
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