| 1. |
- Moberg, Christina, et al.
(författare)
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De unga gör helt rätt när de stämmer staten
- 2022
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Ingår i: Aftonbladet. - 1103-9000.
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Tidskriftsartikel (populärvet., debatt m.m.)abstract
- 1 620 forskare och lärare i forskarvärlden: Vi ställer oss bakom Auroras klimatkrav
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| 2. |
- Bergström, Göran, 1964, et al.
(författare)
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Prevalence of Subclinical Coronary Artery Atherosclerosis in the General Population
- 2021
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Ingår i: Circulation. - Philadelphia : American Heart Association. - 0009-7322 .- 1524-4539. ; 144:12, s. 916-929
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Tidskriftsartikel (refereegranskat)abstract
- Background: Early detection of coronary atherosclerosis using coronary computed tomography angiography (CCTA), in addition to coronary artery calcification (CAC) scoring, may help inform prevention strategies. We used CCTA to determine the prevalence, severity, and characteristics of coronary atherosclerosis and its association with CAC scores in a general population.Methods: We recruited 30 154 randomly invited individuals age 50 to 64 years to SCAPIS (the Swedish Cardiopulmonary Bioimage Study). The study includes individuals without known coronary heart disease (ie, no previous myocardial infarctions or cardiac procedures) and with high-quality results from CCTA and CAC imaging performed using dedicated dual-source CT scanners. Noncontrast images were scored for CAC. CCTA images were visually read and scored for coronary atherosclerosis per segment (defined as no atherosclerosis, 1% to 49% stenosis, or ≥50% stenosis). External validity of prevalence estimates was evaluated using inverse probability for participation weighting and Swedish register data.Results: In total, 25 182 individuals without known coronary heart disease were included (50.6% women). Any CCTA-detected atherosclerosis was found in 42.1%; any significant stenosis (≥50%) in 5.2%; left main, proximal left anterior descending artery, or 3-vessel disease in 1.9%; and any noncalcified plaques in 8.3% of this population. Onset of atherosclerosis was delayed on average by 10 years in women. Atherosclerosis was more prevalent in older individuals and predominantly found in the proximal left anterior descending artery. Prevalence of CCTA-detected atherosclerosis increased with increasing CAC scores. Among those with a CAC score >400, all had atherosclerosis and 45.7% had significant stenosis. In those with 0 CAC, 5.5% had atherosclerosis and 0.4% had significant stenosis. In participants with 0 CAC and intermediate 10-year risk of atherosclerotic cardiovascular disease according to the pooled cohort equation, 9.2% had CCTA-verified atherosclerosis. Prevalence estimates had excellent external validity and changed marginally when adjusted to the age-matched Swedish background population.Conclusions: Using CCTA in a large, random sample of the general population without established disease, we showed that silent coronary atherosclerosis is common in this population. High CAC scores convey a significant probability of substantial stenosis, and 0 CAC does not exclude atherosclerosis, particularly in those at higher baseline risk.
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| 3. |
- Bergström, Göran, et al.
(författare)
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Prevalence of Subclinical Coronary Artery Atherosclerosis in the General Population
- 2021
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Ingår i: Circulation. - : Wolters Kluwer. - 0009-7322 .- 1524-4539. ; 144:12, s. 916-929
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Tidskriftsartikel (refereegranskat)abstract
- Background: Early detection of coronary atherosclerosis using coronary computed tomography angiography (CCTA), in addition to coronary artery calcification (CAC) scoring, may help inform prevention strategies. We used CCTA to determine the prevalence, severity, and characteristics of coronary atherosclerosis and its association with CAC scores in a general population.Methods: We recruited 30 154 randomly invited individuals age 50 to 64 years to SCAPIS (the Swedish Cardiopulmonary Bioimage Study). The study includes individuals without known coronary heart disease (ie, no previous myocardial infarctions or cardiac procedures) and with high-quality results from CCTA and CAC imaging performed using dedicated dual-source CT scanners. Noncontrast images were scored for CAC. CCTA images were visually read and scored for coronary atherosclerosis per segment (defined as no atherosclerosis, 1% to 49% stenosis, or ≥50% stenosis). External validity of prevalence estimates was evaluated using inverse probability for participation weighting and Swedish register data.Results: In total, 25 182 individuals without known coronary heart disease were included (50.6% women). Any CCTA-detected atherosclerosis was found in 42.1%; any significant stenosis (≥50%) in 5.2%; left main, proximal left anterior descending artery, or 3-vessel disease in 1.9%; and any noncalcified plaques in 8.3% of this population. Onset of atherosclerosis was delayed on average by 10 years in women. Atherosclerosis was more prevalent in older individuals and predominantly found in the proximal left anterior descending artery. Prevalence of CCTA-detected atherosclerosis increased with increasing CAC scores. Among those with a CAC score >400, all had atherosclerosis and 45.7% had significant stenosis. In those with 0 CAC, 5.5% had atherosclerosis and 0.4% had significant stenosis. In participants with 0 CAC and intermediate 10-year risk of atherosclerotic cardiovascular disease according to the pooled cohort equation, 9.2% had CCTA-verified atherosclerosis. Prevalence estimates had excellent external validity and changed marginally when adjusted to the age-matched Swedish background population.Conclusions: Using CCTA in a large, random sample of the general population without established disease, we showed that silent coronary atherosclerosis is common in this population. High CAC scores convey a significant probability of substantial stenosis, and 0 CAC does not exclude atherosclerosis, particularly in those at higher baseline risk.
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| 4. |
- Ekblom Bak, Elin, 1981-, et al.
(författare)
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Accelerometer derived physical activity and subclinical coronary and carotid atherosclerosis : cross-sectional analyses in 22 703 middle-aged men and women in the SCAPIS study
- 2023
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Ingår i: BMJ Open. - : BMJ Publishing Group Ltd. - 2044-6055. ; 13:11
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVES: The aim included investigation of the associations between sedentary (SED), low-intensity physical activity (LIPA), moderate-to-vigorous intensity PA (MVPA) and the prevalence of subclinical atherosclerosis in both coronaries and carotids and the estimated difference in prevalence by theoretical reallocation of time in different PA behaviours.DESIGN: Cross-sectional.SETTING: Multisite study at university hospitals.PARTICIPANTS: A total of 22 670 participants without cardiovascular disease (51% women, 57.4 years, SD 4.3) from the population-based Swedish CArdioPulmonary bioImage study were included. SED, LIPA and MVPA were assessed by hip-worn accelerometer.PRIMARY AND SECONDARY OUTCOMES: Any and significant subclinical coronary atherosclerosis (CA), Coronary Artery Calcium Score (CACS) and carotid atherosclerosis (CarA) were derived from imaging data from coronary CT angiography and carotid ultrasound.RESULTS: High daily SED (>70% ≈10.5 hours/day) associated with a higher OR 1.44 (95% CI 1.09 to 1.91), for significant CA, and with lower OR 0.77 (95% CI 0.63 to 0.95), for significant CarA. High LIPA (>55% ≈8 hours/day) associated with lower OR for significant CA 0.70 (95% CI 0.51 to 0.96), and CACS, 0.71 (95% CI 0.51 to 0.97), but with higher OR for CarA 1.41 (95% CI 1.12 to 1.76). MVPA above reference level, >2% ≈20 min/day, associated with lower OR for significant CA (OR range 0.61-0.67), CACS (OR range 0.71-0.75) and CarA (OR range 0.72-0.79). Theoretical replacement of 30 min of SED into an equal amount of MVPA associated with lower OR for significant CA, especially in participants with high SED 0.84 (95% CI 0.76 to 0.96) or low MVPA 0.51 (0.36 to 0.73).CONCLUSIONS: MVPA was associated with a lower risk for significant atherosclerosis in both coronaries and carotids, while the association varied in strength and direction for SED and LIPA, respectively. If causal, clinical implications include avoiding high levels of daily SED and low levels of MVPA to reduce the risk of developing significant subclinical atherosclerosis.
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| 5. |
- Oldgren, Jonas, 1964-, et al.
(författare)
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Systematic Coronary Risk Evaluation estimated risk and prevalent subclinical atherosclerosis in coronary and carotid arteries: A population-based cohort analysis from the Swedish Cardiopulmonary Bioimage Study
- 2021
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Ingår i: European Journal of Preventive Cardiology. - : Oxford University Press (OUP). - 2047-4873 .- 2047-4881. ; 28:3, s. 250-259
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Tidskriftsartikel (refereegranskat)abstract
- Background It is not clear if the European Systematic Coronary Risk Evaluation algorithm is useful for identifying prevalent subclinical atherosclerosis in a population of apparently healthy individuals. Our aim was to explore the association between the risk estimates from Systematic Coronary Risk Evaluation and prevalent subclinical atherosclerosis. Design The design of this study was as a cross-sectional analysis from a population-based study cohort. Methods From the general population, the Swedish Cardiopulmonary Bioimage Study randomly invited individuals aged 50-64 years and enrolled 13,411 participants mean age 57 (standard deviation 4.3) years; 46% males between November 2013-December 2016. Associations between Systematic Coronary Risk Evaluation risk estimates and coronary artery calcification and plaques in the carotid arteries by using imaging data from a computed tomography of the heart and ultrasonography of the carotid arteries were examined. Results Coronary calcification was present in 39.5% and carotid plaque in 56.0%. In men, coronary artery calcium score >0 ranged from 40.7-65.9% and presence of carotid plaques from 54.5% to 72.8% in the age group 50-54 and 60-65 years, respectively. In women, the corresponding difference was from 17.1-38.9% and from 41.0-58.4%. A doubling of Systematic Coronary Risk Evaluation was associated with an increased probability to have coronary artery calcium score >0 (odds ratio: 2.18 (95% confidence interval 2.07-2.30)) and to have >1 carotid plaques (1.67 (1.61-1.74)). Conclusion Systematic Coronary Risk Evaluation estimated risk is associated with prevalent subclinical atherosclerosis in two major vascular beds in a general population sample without established cardiovascular disease or diabetes mellitus. Thus, the Systematic Coronary Risk Evaluation risk chart may be of use for estimating the risk of subclinical atherosclerosis.
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| 6. |
- Persson, Mats, et al.
(författare)
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2014 års Ekonomipris till Jean Tirole
- 2014
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Ingår i: Ekonomisk Debatt. - Stockholm : Nationalekonomiska föreningen. - 0345-2646. ; :8, s. 5-14
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 7. |
- Bornefalk, Hans, 1974-, et al.
(författare)
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Allowable forward model misspecification for accurate basis decomposition in a silicon detector based spectral CT
- 2015
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Ingår i: IEEE Transactions on Medical Imaging. - : IEEE Press. - 0278-0062 .- 1558-254X. ; 34:3, s. 788-795
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Tidskriftsartikel (refereegranskat)abstract
- Material basis decomposition in the sinogram domain requires accurate knowledge of the forward model in spectral computed tomography (CT). Misspecifications over a certain limit will result in biased estimates and make quantum limited (where statistical noise dominates) quantitative CT difficult. We present a method whereby users can determine the degree of allowed misspecification error in a spectral CT forward model and still have quantification errors that are limited by the inherent statistical uncertainty. For a particular silicon detector based spectral CT system, we conclude that threshold determination is the most critical factor and that the bin edges need to be known to within 0.15 keV in order to be able to perform quantum limited material basis decomposition. The method as such is general to all multibin systems.
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| 8. |
- Bornefalk, Hans, et al.
(författare)
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Effect of Temperature Variation on the Energy Response of a Photon Counting Silicon CT Detector
- 2013
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Ingår i: IEEE Transactions on Nuclear Science. - : Institute of Electrical and Electronics Engineers (IEEE). - 0018-9499 .- 1558-1578. ; 60:2, s. 1442-1449
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Tidskriftsartikel (refereegranskat)abstract
- The effect of temperature variation on pulse height determination accuracy is determined for a photon counting multibin silicon detector developed for spectral CT. Theoretical predictions of the temperature coefficient of the gain and offset are similar to values derived from synchrotron radiation measurements in a temperature controlled environment. By means of statistical modeling, we conclude that temperature changes affect all channels equally and with separate effects on gain and threshold offset. The combined effect of a 1 degrees C temperature increase is to decrease the detected energy by 0.1 keV for events depositing 30 keV. For the electronic noise, no statistically significant temperature effect was discernible in the data set, although theory predicts a weak dependence. The method is applicable to all x-ray detectors operating in pulse mode.
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| 9. |
- Bornefalk, Hans, et al.
(författare)
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Necessary forward model specification accuracy for basis material decomposition in spectral CT
- 2014
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Ingår i: Medical Imaging 2014. - : SPIE - International Society for Optical Engineering. - 9780819498267 ; , s. 90332I-
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Konferensbidrag (refereegranskat)abstract
- Material basis decomposition in the sinogram domain requires accurate knowledge of the forward model in spectral CT. Misspecifications over a certain limit will result in biased estimates and make quantum limited quantitative CT difficult. We present a method whereby users can determine the degree of allowed misspecification error in a spectral CT forward model, and still have quantification errors that are quantum limited.
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| 10. |
- Brunskog, Rickard, et al.
(författare)
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Experimental Evaluation of a Micron-Resolution CT Detector
- 2024
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Ingår i: Medical Imaging 2024: Physics of Medical Imaging. - : SPIE-Intl Soc Optical Eng.
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Konferensbidrag (refereegranskat)abstract
- Purpose: Current photon-counting detectors are limited to a pixel size of 0.3 mm-1 mm, as decreasing the pixel size further generally introduces degraded dose efficiency and energy resolution from excessive charge sharing. In this work, we present experimental measurements of the first photon-counting detector prototype designed to leverage the charge sharing to estimate the photon interaction position, where simulations indicate a theoretical resolution of around 1 µm using a similar geometry. The goal of the measurements is to validate our Monte-Carlo simulation for further development. Approach: DAC sweeps are performed with an X-ray beam at specified locations on the sensor front, with the beam at 20 keV and 35 keV, as well as with different sensor biases with the beam at 35 keV. The experimental data are then compared to a Monte Carlo simulation combined with a charge transport model. In this first prototype wire bonds are used, and as such only a few channels are connected. Results: The experimental data agree generally well with the simulated data with the beam close to the electrodes, with the simulated data diverging from the experiments with the beam further away from the electrodes. The induced charge cloud signal exhibits a fairly linear dependency on the beam position, indicating that any estimation techniques will yield more precise position when the photon interacts further away from the electrodes, rather than closer. Conclusions: With the experimental data and the simulations agreeing generally well, together with the same software previously indicating a resolution of around 1 µm, we expect an ultra-high-resolution detector to be in reach, and are encouraged to continue development.
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| 11. |
- Brunskog, Rickard, et al.
(författare)
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First experimental evaluation of a high-resolution deep silicon photon-counting sensor
- 2024
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Ingår i: Journal of Medical Imaging. - : SPIE-Intl Soc Optical Eng. - 2329-4302 .- 2329-4310. ; 11:1
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: Current photon-counting computed tomography detectors are limited to a pixel size of around 0.3 to 0.5 mm due to excessive charge sharing degrading the dose efficiency and energy resolution as the pixels become smaller. In this work, we present measurements of a prototype photon-counting detector that leverages the charge sharing to reach a theoretical sub-pixel resolution in the order of 1 μm. The goal of the study is to validate our Monte-Carlo simulation using measurements, enabling further development. Approach: We measure the channel response at the MAX IV Lab, in the DanMAX beamline, with a 35 keV photon beam, and compare the measurements with a 2D Monte Carlo simulation combined with a charge transport model. Only a few channels on the prototype are connected to keep the number of wire bonds low. Results: The measurements agree generally well with the simulations with the beam close to the electrodes but diverge as the beam is moved further away. The induced charge cloud signals also seem to increase linearly as the beam is moved away from the electrodes. Conclusions: The agreement between measurements and simulations indicates that the Monte-Carlo simulation can accurately model the channel response of the detector with the photon interactions close to the electrodes, which indicates that the unconnected electrodes introduce unwanted effects that need to be further explored. With the same Monte-Carlo simulation previously indicating a resolution of around 1 μm with similar geometry, the results are promising that an ultra-high resolution detector is not far in the future.
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| 12. |
- Bülow-Hübe, Helena, 1964-, et al.
(författare)
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Nuläge termisk komfort : en kunskapssammanställning
- 2022
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Boverket ser ett behov av en kunskapssammanställning kring nuläget inom termisk komfort i Sverige för att ha en så bred och korrekt förståelse som möjligt för vem branschen är, vilka regler som tillämpas, var det finns kunskapscentra och vilka utvecklingsbehov som behöver stödjas för att branschen ska kunna ta större ansvar.Några faktafrågeställningar som vi författare noterat och som kan vara värda att kartlägga ytterligare:Metoder att simuleraKlimatdata för analyser och simuleringarBetydelsen av värmeöarÅtgärder för att minska värmelaster på byggnaderörbereda plats i byggnader för komfortkylaRisker med fukt och påväxt vid komfortkylaPrioriterade rum för termisk komfortUpplåtelseformers inverkan, utsatta grupper och lokala reglerVädring och fläktarPrioritera passiva åtgärderPortabel luftkylning/komfortkylaTillsyn och bygglovKrav som inte är samordnade (energi, dagsljus, buller, etc.)VarningssystemFörhoppningen är att kartläggning av termisk komfort ska bidra till kunskapsspridning om bransch, aktörer, teknik, system, konstruktion, kontroller, drift och underhåll samt forskning och utveckling.
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| 13. |
- Chen, Han, et al.
(författare)
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A photon-counting silicon-strip detector for digital mammography with an ultrafast 0.18-mu m CMOS ASIC
- 2014
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Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier. - 0168-9002 .- 1872-9576. ; 749, s. 1-6
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Tidskriftsartikel (refereegranskat)abstract
- We have evaluated a silicon-strip detector with a 0.18-mu m CMOS application specific integrated circuits (ASIC) containing 160 channels for use in photon-counting digital mammography. Measurements were performed at the Elettra light source using monochromatic X-ray beams with different energies and intensities. Energy resolution, Delta E/E-in, was measured to vary between 0.10 and 0.23 in the energy range of 15-40 keV. Pulse pileup has shown little effect on energy resolution.
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| 14. |
- Chen, Han, 1986-, et al.
(författare)
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Optimization Of Beam Quality For Photon-Counting Spectral Computed Tomography In Head Imaging: Simulation Study
- 2015
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Ingår i: Journal of Medical Imaging. - : SPIE. - 2329-4302 .- 2329-4310. ; 2:4, s. 043504-1-043504-16
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Tidskriftsartikel (refereegranskat)abstract
- Head computed tomography (CT) plays an important role in the comprehensive evaluation of acutestroke. Photon-counting spectral detectors, as promising candidates for use in the next generation of x-ray CTsystems, allow for assigning more weight to low-energy x-rays that generally contain more contrast information.Most importantly, the spectral information can be utilized to decompose the original set of energy-selectiveimages into several basis function images that are inherently free of beam-hardening artifacts, a potential ad-vantage for further improving the diagnosis accuracy. We are developing a photon-counting spectral detector forCT applications. The purpose of this work is to determine the optimal beam quality for material decomposition intwo head imaging cases: nonenhanced imaging and K-edge imaging. A cylindrical brain tissue of 16-cm diam-eter, coated by a 6-mm-thick bone layer and 2-mm-thick skin layer, was used as a head phantom. The imagingtarget was a 5-mm-thick blood vessel centered in the head phantom. In K-edge imaging, two contrast agents,iodine and gadolinium, with the same concentration (5mg∕mL) were studied. Three parameters that affect beamquality were evaluated: kVp settings (50 to 130 kVp), filter materials (Z¼13to 83), and filter thicknesses [0 to 2half-value layer (HVL)]. The image qualities resulting from the varying x-ray beams were compared in terms oftwo figures of merit (FOMs): squared signal-difference-to-noise ratio normalized by brain dose (SDNR2∕BD) andthat normalized by skin dose (SDNR2∕SD). For nonenhanced imaging, the results show that the use of the 120-kVp spectrum filtered by 2 HVL copper (Z¼29) provides the best performance in both FOMs. When iodine isused in K-edge imaging, the optimal filter is 2 HVL iodine (Z¼53) and the optimal kVps are 60 kVp in terms ofSDNR2∕BD and 75 kVp in terms of SDNR2∕SD. A tradeoff of 65 kVp was proposed to lower the potential riskof skin injuries if a relatively long exposure time is necessarily performed in the iodinated imaging. In the case ofgadolinium imaging, both SD and BD can be minimized at 120 kVp filtered with 2 HVL thulium (Z¼69). Theresults also indicate that with the same concentration and their respective optimal spectrum, the values ofSDNR2∕BD and SDNR2∕SD in gadolinium imaging are, respectively, around 3 and 10 times larger thanthose in iodine imaging. However, since gadolinium is used in much lower concentrations than iodine in theclinic, iodine may be a preferable candidate for K-edge imaging.
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| 15. |
- da Silva, Joakim, et al.
(författare)
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Resolution characterization of a silicon-based, photon-counting computed tomography prototype capable of patient scanning
- 2019
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Ingår i: Journal of Medical Imaging. - USA : SPIE - International Society for Optical Engineering. - 2329-4302 .- 2329-4310. ; 6:4
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Tidskriftsartikel (refereegranskat)abstract
- Photon-counting detectors are expected to bring a range of improvements to patient imaging with x-ray computed tomography (CT). One is higher spatial resolution. We demonstrate the resolution obtained using a commercial CT scanner where the original energy-integrating detector has been replaced by a single-slice, silicon-based, photon-counting detector. This prototype constitutes the first full-field-of-view silicon-based CT scanner capable of patient scanning. First, the pixel response function and focal spot profile are measured and, combining the two, the system modulation transfer function is calculated. Second, the prototype is used to scan a resolution phantom and a skull phantom. The resolution images are compared to images from a state-of-the-art CT scanner. The comparison shows that for the prototype 19 lp∕cm are detectable with the same clarity as 14 lp∕cm on the reference scanner at equal dose and reconstruction grid, with more line pairs visible with increasing dose and decreasing image pixel size. The high spatial resolution remains evident in the anatomy of the skull phantom and is comparable to that of other photon-counting CT prototypes present in the literature. We conclude that the deep silicon-based detector used in our study could provide improved spatial resolution in patient imaging without increasing the x-ray dose.
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| 16. |
- Daniel, Maxime, et al.
(författare)
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Charge collection efficiency of CdTe detectors : Impact of charge collection time and polarisation
- 2023
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Ingår i: Medical Imaging 2023. - : SPIE-Intl Soc Optical Eng.
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Konferensbidrag (refereegranskat)abstract
- Cadmium telluride (CdTe) is one of the materials used in photon-counting detectors for x-ray computed tomography. One challenge with this material is that it is susceptible to polarisation due to holes being trapped in impurities in the material. This can potentially lead to the buildup of bulk charge in the semiconductor, causing decreased charge collection efficiency and degraded energy resolution. In this work, we develop a simulation model of CdTe detectors with polarisation and use it to study the effect of polarisation on the measured energy spectrum for different charge collection times. To this end, we use a theoretical model of charge buildup to find the critical charge in the detector's bulk above which the detector can be considered completely polarised. We then simulate a 320-by-270-by-1600 μm CdTe detector used in CT clinical imaging, for varying degrees of polarisation (ratio between the actual charge and the critical charge) and charge collection time. Our results show that the measured spectrum gets heavily distorted for large degrees of polarisation or for short charge collection time. We also put these results in context by discussing how they relate to the critical fluence rate and the time of flight of the charge carriers. These results can lead to improved simulation models of CdTe detectors and a better understanding the factors affecting their imaging performance.
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| 17. |
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| 18. |
- Danielsson, Mats, Professor, et al.
(författare)
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Photon-counting x-ray detectors for CT
- 2021
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Ingår i: Physics in Medicine and Biology. - : IOP Publishing. - 0031-9155 .- 1361-6560. ; 66:3, s. 03TR01-
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Forskningsöversikt (refereegranskat)abstract
- The introduction of photon-counting detectors is expected to be the next major breakthrough in clinical x-ray CT. During the last decade, there has been considerable research activity in the field of photon-counting CT, in terms of both hardware development and theoretical understanding of the factors affecting image quality. In this article, we review the recent progress in this field with the intent of highlighting the relationship between detector design considerations and the resulting image quality. We discuss detector design choices such as converter material, pixel size, and readout electronics design, and then elucidate their impact on detector performance in terms of dose efficiency, spatial resolution, and energy resolution. Furthermore, we give an overview of data processing, reconstruction methods and metrics of imaging performance; outline clinical applications; and discuss potential future developments.
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| 19. |
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| 20. |
- Engström, Gunnar, et al.
(författare)
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The Swedish CArdioPulmonary BioImage Study : objectives and design
- 2015
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Ingår i: Journal of Internal Medicine. - : Wiley. - 0954-6820 .- 1365-2796. ; 278:6, s. 645-659
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Tidskriftsartikel (refereegranskat)abstract
- Cardiopulmonary diseases are major causes of death worldwide, but currently recommended strategies for diagnosis and prevention may be outdated because of recent changes in risk factor patterns. The Swedish CArdioPulmonarybioImage Study (SCAPIS) combines the use of new imaging technologies, advances in large-scale 'omics' and epidemiological analyses to extensively characterize a Swedish cohort of 30 000 men and women aged between 50 and 64 years. The information obtained will be used to improve risk prediction of cardiopulmonary diseases and optimize the ability to study disease mechanisms. A comprehensive pilot study in 1111 individuals, which was completed in 2012, demonstrated the feasibility and financial and ethical consequences of SCAPIS. Recruitment to the national, multicentre study has recently started.
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| 21. |
- Grönberg, Fredrik
(författare)
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Spectral Photon-Counting Computed Tomography with Silicon Detectors: New Models and Applications
- 2022
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- X-ray computed tomography (CT) is a widely used imaging modality that enables visualization of nearly every part of the human body. It is used for diagnosis of disease and injury as well as medical treatment planning. The vast majority of CT scanners in clinical use today have energy-integrating x-ray detectors, which measure the total incident energy in a given measurement.Spectral photon-counting detectors operate by counting individual photons and measuring their energy, and are expected to yield the next major advance in CT, with improvements in spatial resolution, dose efficiency, material differentiation and quantitative imaging capabilities compared to the current state-of-the-art.In this Thesis, a set of new models and applications for a spectral photon-counting silicon detector developed for CT is investigated. The first part of the Thesis is dedicated to the modeling of spectral photon-counting silicon detectors. A new statistical model for the effects of pulse pileup is presented. Also, the effects on image quality from intra-detector Compton scatter in silicon detectors are investigated via spatio-energetic modeling. In the second part of the Thesis, potential applications for spectral photon-counting detectors are investigated. An experimental study of ex vivo CT imaging of an excised human heart with calcified plaque is presented. It demonstrates the feasibility of unconstrained projection-based three-material decomposition with iodine as a third basis material and explores the potential improvements in spatial resolution and material differentiation that can be achieved with a spectral photon-counting silicon detector compared to a conventional dual-energy CTsystem. Two other applications are investigated with simulations: a method for reconstructing CT images from spectral photon-counting CT data that accurately mimic conventional CT images; and a method for estimating iron concentration in mixtures of liver and adipose tissue when using three basis functions instead of only two to describe the linear attenuation coefficient of tissues in the human body. Although the methods presented in this Thesis have been specifically developed for a spectral photon-counting silicon detector, they are also applicable for other types of photon-counting detectors.
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| 22. |
- Hansson, Bengt, et al.
(författare)
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Byggledning : produktion
- 2017
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Bok (övrigt vetenskapligt/konstnärligt)abstract
- Lärobok för ingenjörsutbildningar som inriktas på produktionsskedet av ett byggporjekt
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| 23. |
- Hansson, Karna, et al.
(författare)
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Carbon and nitrogen pools and fluxes above and below ground in spruce, pine and birch stands in southern Sweden
- 2013
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Ingår i: Forest Ecology and Management. - : Elsevier BV. - 0378-1127 .- 1872-7042. ; 309, s. 28-35
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Tidskriftsartikel (refereegranskat)abstract
- We synthesised results on soil carbon (C) and nitrogen (N) fluxes and the accumulation of soil organic C and N under adjacent 50-year-old Norway spruce, Scots pine and silver birch stands growing on similar soils and evaluated the different processes involved. C and N budgets were calculated. Spruce stands had larger stocks of C and N in biomass and soil than birch stands, with pine intermediate. The differences in soil stocks were mainly found in the organic layer, whereas differences in the mineral soil were small. The study showed that there is no simple answer to what is causing the differences in soil C and N stocks, because several processes are interacting. Spruce and pine trees had higher biomass and litter production than birch trees, but total litter inputs showed no significant difference between stands, because the rich ground vegetation under pine and birch contributed with substantial litter inputs, in contrast to the poor ground vegetation under spruce. Decomposition rate (per g of C) was markedly higher under birch than under spruce and pine resulting in lower C and N stocks in the organic layer. This effect was amplified by higher abundance and biomass of earthworms, favoured by higher pH and palatable litter under birch. Earthworm bioturbation probably both increased decomposition rate and damaged the ectomycorrhizal network with negative consequences for the formation of mycorrhizal litter and C storage. In conclusion, the direct effects of spruce, pine and birch litter on C and N pools and fluxes were modified by indirect effects of understorey structure, pH and earthworm responses. (C) 2013 Elsevier B.V. All rights reserved.
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| 24. |
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| 25. |
- Hudson, Lawrence N, et al.
(författare)
-
The database of the PREDICTS (Projecting Responses of Ecological Diversity In Changing Terrestrial Systems) project
- 2017
-
Ingår i: Ecology and Evolution. - : John Wiley & Sons. - 2045-7758. ; 7:1, s. 145-188
-
Tidskriftsartikel (refereegranskat)abstract
- The PREDICTS project-Projecting Responses of Ecological Diversity In Changing Terrestrial Systems (www.predicts.org.uk)-has collated from published studies a large, reasonably representative database of comparable samples of biodiversity from multiple sites that differ in the nature or intensity of human impacts relating to land use. We have used this evidence base to develop global and regional statistical models of how local biodiversity responds to these measures. We describe and make freely available this 2016 release of the database, containing more than 3.2 million records sampled at over 26,000 locations and representing over 47,000 species. We outline how the database can help in answering a range of questions in ecology and conservation biology. To our knowledge, this is the largest and most geographically and taxonomically representative database of spatial comparisons of biodiversity that has been collated to date; it will be useful to researchers and international efforts wishing to model and understand the global status of biodiversity.
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| 26. |
- Hudson, Lawrence N., et al.
(författare)
-
The PREDICTS database : a global database of how local terrestrial biodiversity responds to human impacts
- 2014
-
Ingår i: Ecology and Evolution. - : Wiley. - 2045-7758. ; 4:24, s. 4701-4735
-
Tidskriftsartikel (refereegranskat)abstract
- Biodiversity continues to decline in the face of increasing anthropogenic pressures such as habitat destruction, exploitation, pollution and introduction of alien species. Existing global databases of species' threat status or population time series are dominated by charismatic species. The collation of datasets with broad taxonomic and biogeographic extents, and that support computation of a range of biodiversity indicators, is necessary to enable better understanding of historical declines and to project - and avert - future declines. We describe and assess a new database of more than 1.6 million samples from 78 countries representing over 28,000 species, collated from existing spatial comparisons of local-scale biodiversity exposed to different intensities and types of anthropogenic pressures, from terrestrial sites around the world. The database contains measurements taken in 208 (of 814) ecoregions, 13 (of 14) biomes, 25 (of 35) biodiversity hotspots and 16 (of 17) megadiverse countries. The database contains more than 1% of the total number of all species described, and more than 1% of the described species within many taxonomic groups - including flowering plants, gymnosperms, birds, mammals, reptiles, amphibians, beetles, lepidopterans and hymenopterans. The dataset, which is still being added to, is therefore already considerably larger and more representative than those used by previous quantitative models of biodiversity trends and responses. The database is being assembled as part of the PREDICTS project (Projecting Responses of Ecological Diversity In Changing Terrestrial Systems - ). We make site-level summary data available alongside this article. The full database will be publicly available in 2015.
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| 27. |
- Jin, Zihui, et al.
(författare)
-
First experimental evaluation of count-rate performance for micrometre resolution deep silicon detector
- 2024
-
Ingår i: Physics in Medicine and Biology. - : IOP Publishing. - 0031-9155 .- 1361-6560. ; 69:3
-
Tidskriftsartikel (refereegranskat)abstract
- Objective. An ultra-fine-pitch deep silicon detector has been developed for clinical photon-counting computed tomography (CT). With a small pixel size of 14 × 650 μm2, it has shown potential to reach micrometre spatial resolution in previous simulation studies. A detector prototype with such geometry has been manufactured, and we report on the first experimental evaluation of its count-rate performance. Approach. The measurement was carried out at MAX IV synchrotron laboratory with 35 keV monochromatic x-rays. By inserting tungsten attenuators of 50, 75, 100, 150, 200, 225, 325 μ m-thicknesses into the beam, the response of the detector to fluence rates from 3.3 × 107 to 1.3 × 1011 mm−2 s−1 was characterized. Main results. The measurement result showed that the detector exhibited count rate linearity up to 6.66 × 108 mm−2 s−1 with 13% count loss and was still functional at count rate up to 2.9 × 1010 mm−2 s−1. A semi-nonparalyzable dead-time model was fitted to the count-rate behaviour of the detector, showing great agreement with the measured data, with an estimated nonparalyzable dead time of 2.9 ns. Significance. This is the first experimental evaluation of the count-rate performance for a deep silicon detector with such small pixel geometry. The results suggest that this type of detector shows the potential to be used at fluence rates encountered in clinical CT with little count loss due to pile-up.
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| 28. |
- Johnsson, Åse (Allansdotter), 1966, et al.
(författare)
-
Incidental findings and their handling in the Swedish CArdioPulmonary bioimage study (SCAPIS)
- 2017
-
Ingår i: Incidental Radiological Findings. - Cham : Springer International Publishing. - 0942-5373 .- 2197-4187. - 9783319425818 - 9783319425795 - 9783319826127 ; , s. 91-101
-
Bokkapitel (refereegranskat)abstract
- The Swedish CArdioPulmonary bioImage Study (SCAPIS) combines the use of new imaging technologies, large-scale proteomics/metabolomics/genomics, and epidemiological analyses to extensively characterize a Swedish cohort of 30,000 men and women aged between 50 and 64 years. Its main aims are to improve risk prediction and to optimize our ability to study mechanisms of cardiopulmonary diseases. SCAPIS is currently recruiting at six sites in Sweden, and a pilot study was conducted in 2012 to test the feasibility of the comprehensive study protocol. In the planning phase, it was recognized that the detailed phenotyping used in SCAPIS would identify a large number of clinical findings in need of medical attention. This was confirmed by evaluation of results from the pilot study. Here we focus on pulmonary nodules and asymptomatic coronary artery stenosis. These clinical features were observed in a large number of participants, and the clinical handing and prognosis related to these observations are unclear. They thus posed great challenges for the study in their practical and ethical handling. This chapter describes how we developed procedures to handle these findings based on existing evidence and expert consensus as well as deliberations on ethical issues.
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| 29. |
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| 30. |
- Liu, Xuejin, et al.
(författare)
-
A Silicon-Strip Detector for Photon-Counting Spectral CT : Energy Resolution From 40 keV to 120 keV
- 2014
-
Ingår i: IEEE Transactions on Nuclear Science. - 0018-9499 .- 1558-1578. ; 61:3, s. 1099-1105
-
Tidskriftsartikel (refereegranskat)abstract
- We are developing a segmented silicon-strip detector for spectral computed tomography. The detector operates in photon-counting mode and allows pulse-height discrimination with 8 adjustable energy bins. In this work, we determine the energy resolution of a detector module using monoenergetic x-rays from 40 keV to 120 keV, provided at the European Synchrotron Radiation Facility, Grenoble. For each incident x-ray energy, pulse height spectra at different input photon fluxes are obtained. We investigate changes of the energy resolution due to charge sharing between pixels and pulse pileup. The different incident energies are used to channel-wise calibrate the pulse-height response in terms of signal gain and offset and to probe the homogeneity of the detector module. The detector shows a linear pulse-height response in the energy range from 40 keV to 120 keV. The gain variation among the channels is below 4%, whereas the variation of the offsets is on the order of 1 keV. We find an absolute energy resolution (sigma(E)) that degrades from 1.5 keV to 1.9 keV with increasing x-ray energy from 40 keV to 100 keV. With increasing input count rate, sigma(E) degrades by approximately 4 . 10(-3) keV Mcps(-1) mm(2), which is, within error bars, the same for the different energies. The effect of charge sharing on the width of the response peak is found to be negligible.
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| 31. |
- Liu, Xuejin, et al.
(författare)
-
Characterization of a silicon strip detector for photon-counting spectral CT using monoenergetic photons from 40 keV to 120 keV
- 2014
-
Ingår i: Medical Imaging 2014. - : SPIE - International Society for Optical Engineering. - 9780819498267 ; , s. 90333O-
-
Konferensbidrag (refereegranskat)abstract
- Background: We are developing a segmented silicon strip detector that operates in photon-counting mode and allows pulse-height discrimination with 8 adjustable energy bins. In this work, we determine the energy resolution of the detector using monoenergetic x-ray radiation from 40 keV to 120 keV. We further investigate the effects of pulse pileup and charge sharing between detector channels that may lead to a decreased energy resolution. Methods: For each incident monochromatic x-ray energy, we obtain count spectra at different photon fluxes. These spectra corresponds to the pulse-height response of the detector and allow the determination of energy resolution and charge-sharing probability. The energy resolution, however, is influenced by signal pileup and charge sharing. Both effects are quantified using Monte Carlo simulations of the detector that aim to reproduce the conditions during the measurements. Results: The absolute energy resolution is found to increase from 1.7 to 2.1 keV for increasing energies 40 keV to 120 keV at the lowest measured photon flux. The effect of charge sharing is found to increase the absolute energy resolution by a factor of 1.025 at maximum. This increase is considered as negligibly small. The pileup of pulses leads to a deterioration rate of the energy resolution of 4 · 10-3 keV Mcps-1 mm2, corresponding to an increase of 0.04keV per 10 Mcps increase of the detected count rate.
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| 32. |
- Liu, Xuejin, et al.
(författare)
-
Energy Calibration of a Silicon-Strip Detector for Photon-Counting Spectral CT by Direct Usage of the X-ray Tube Spectrum
- 2015
-
Ingår i: IEEE Transactions on Nuclear Science. - 0018-9499 .- 1558-1578. ; 62:1, s. 68-75
-
Tidskriftsartikel (refereegranskat)abstract
- The variation among energy thresholds in a multibin detector for photon-counting spectral CT can lead to ring artefacts in the reconstructed images. Calibration of the energy thresholds can be used to achieve homogeneous threshold settings or to develop compensation methods to reduce the artefacts. We have developed an energy-calibrationmethod for the different comparator thresholds employed in a photon-counting silicon-strip detector. In our case, this corresponds to specifying the linear relation between the threshold positions in units of mV and the actual deposited photon energies in units of keV. This relation is determined by gain and offset values that differ for different detector channels due to variations in the manufacturing process. Typically, the calibration is accomplished by correlating the peak positions of obtained pulse-height spectra to known photon energies, e. g. with the aid of mono-energetic x rays from synchrotron radiation, radioactive isotopes or fluorescence materials. Instead of mono-energetic x rays, the calibrationmethod presented in this papermakes use of a broad x-ray spectrum provided by commercial x-ray tubes. Gain and offset as the calibration parameters are obtained by a regression analysis that adjusts a simulated spectrum of deposited energies to ameasured pulse-height spectrum. Besides the basic photon interactions such as Rayleigh scattering, Compton scattering and photo-electric absorption, the simulation takes into account the effect of pulse pileup, charge sharing and the electronic noise of the detector channels. We verify the method for different detector channels with the aid of a table-top setup, where we find the uncertainty of the keV-value of a calibrated threshold to be between 0.1 and 0.2 keV.
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| 33. |
- Liu, Xuejin, et al.
(författare)
-
Modelling the channel-wise count response of a photon-counting spectral CT detector to a broad x-ray spectrum
- 2015
-
Ingår i: Medical Imaging 2015: Physics of Medical Imaging. - : SPIE. - 9781628415025
-
Konferensbidrag (refereegranskat)abstract
- Variations among detector channels in CT very sensitively lead to ring artefacts in the reconstructed images. For material decomposition in the projection domain, the variations can result in intolerable biases in the material line integral estimates. A typical way to overcome these effects is to apply calibration methods that try to unify spectral responses from different detector channels to an ideal response from a detector model. However, the calibration procedure can be rather complex and require excessive calibration measurements for a multitude of combinations of x-ray shapes, tissue combinations and thicknesses. In this paper, we propose a channel-wise model for a multibin photon-counting detector for spectral CT. Predictions of this channel-wise model match well with their physical performances, which can thus be used to eliminate ring artefacts in CT images and achieve projection-basis material decomposition. In an experimental validation, image data show significant improvement with respect to ring artefacts compared to images calibrated with flat-fielding data. Projection-based material decomposition gives basis material images showing good separation among individual materials and good quantification of iodine and gadolinium contrast agents. The work indicates that the channel-wise model can be used for quantitative CT with this detector.
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| 34. |
- Liu, Xuejin, et al.
(författare)
-
Spectral response model for a multibin photon-counting spectral computed tomography detector and its applications
- 2015
-
Ingår i: Journal of Medical Imaging. - : SPIE - International Society for Optical Engineering. - 2329-4302 .- 2329-4310. ; 2:3
-
Tidskriftsartikel (refereegranskat)abstract
- Variations among detector channels in computed tomography can lead to ring artifacts in the reconstructed images and biased estimates in projection-based material decomposition. Typically, the ring artifacts are corrected by compensation methods based on flat fielding, where transmission measurements are required for a number of material-thickness combinations. Phantoms used in these methods can be rather complex and require an extensive number of transmission measurements. Moreover, material decomposition needs knowledge of the individual response of each detector channel to account for the detector inhomogeneities. For this purpose, we have developed a spectral response model that binwise predicts the response of a multibin photon-counting detector individually for each detector channel. The spectral response model is performed in two steps. The first step employs a forward model to predict the expected numbers of photon counts, taking into account parameters such as the incident x-ray spectrum, absorption efficiency, and energy response of the detector. The second step utilizes a limited number of transmission measurements with a set of flat slabs of two absorber materials to fine-tune the model predictions, resulting in a good correspondence with the physical measurements. To verify the response model, we apply the model in two cases. First, the model is used in combination with a compensation method which requires an extensive number of transmission measurements to determine the necessary parameters. Our spectral response model successfully replaces these measurements by simulations, saving a significant amount of measurement time. Second, the spectral response model is used as the basis of the maximum likelihood approach for projection-based material decomposition. The reconstructed basis images show a good separation between the calcium-like material and the contrast agents, iodine and gadolinium. The contrast agent concentrations are reconstructed with more than 94% accuracy.
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| 35. |
|
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| 36. |
- McGinn, Steven, et al.
(författare)
-
New Technologies for DNA analysis-A review of the READNA Project.
- 2016
-
Ingår i: New Biotechnology. - : Elsevier BV. - 1876-4347 .- 1871-6784.
-
Forskningsöversikt (refereegranskat)abstract
- The REvolutionary Approaches and Devices for Nucleic Acid analysis (READNA) project received funding from the European Commission for 4 1/2 years. The objectives of the project revolved around technological developments in nucleic acid analysis. The project partners have discovered, created and developed a huge body of insights into nucleic acid analysis, ranging from improvements and implementation of current technologies to the most promising sequencing technologies that constitute a 3(rd) and 4(th) generation of sequencing methods with nanopores and in situ sequencing, respectively.
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| 37. |
|
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| 38. |
- Nilsson, Kerstin, et al.
(författare)
-
54 forskare: Inte alla klarar höjd pensions-ålder
- 2017
-
Ingår i: Svenska Dagbladet, Stockholm. - 1101-2412.
-
Tidskriftsartikel (populärvet., debatt m.m.)abstract
- Ett hållbart och acceptabelt pensionssystem måste utformas utifrån personliga förutsättningar och förhållanden i arbetslivet, så att fler klarar att arbeta i högre ålder. Att enbart genom ekonomiska åtgärder höja pensionsåldern är inte långsiktigt hållbart, skriver 54 forskare.DEBATT | PENSIONForskning visar att cirka var fjärde har en diagnos eller skada orsakad av sitt arbete. Detta gör arbetsorsakad sjukdom och skada till ett betydelsefullt folkhälsoproblem. Att då enbart genom ekonomiska åtgärder höja pensionsåldern för samtliga (yrkes)grupper utifrån deras kronologiska ålder är inte långsiktigt hållbart när individers biologiska ålder är så olika bland annat till följd av arbetslivet. Detta är en demokratifråga. Forskning om äldre i arbetslivet och hållbart arbete visar att man då främst flyttar individer från pensionssystemet till sjukförsäkringssystemet och ökar klyftorna i samhället.Debatt Det här är en argumenterande text med syfte att påverka. Åsikterna som uttrycks är skribentens egna.Vi är 54 forskare som nu gemensamt har skrivit denna debattartikel. Anledningen är att vi är oroade över att cirka var fjärde blir sjuk av sitt arbete samtidigt som man i det förslag som ligger om att senarelägga ålderspensionen i princip utgår ifrån att arbetskraftsdeltagande enbart styrs av ekonomin. Vi vill trycka på betydelsen av åtgärder i arbetslivet för att komma tillrätta med ohälsan, det vill säga inte enbart ekonomiska restriktioner som tvingar folk som inte kan, vill och orkar att stanna kvar i arbetslivet till en högre kronologisk ålder.Pensionssystemet bygger på att vi ska arbeta en viss del av våra liv för att förtjäna möjligheter till pension. Vi bör dock inte enbart utgå ifrån antalet år sedan en person föddes, då korttidsutbildade generellt träder in på arbetsmarknaden tidigare än långtidsutbildade. De har alltså varit en del av arbetskraften från en yngre ålder. Människor med kortare utbildning har oftare ett arbete som innebär påfrestningar som kan inverka negativt på hälsotillståndet och som till och med kan påskynda det biologiska åldrandet. Dessutom lever korttidsutbildade generellt sett inte lika länge som långtidsutbildade, vilket delvis även avspeglar skilda livs- och arbetsvillkor.Den svenska sjukförsäkringsreformen 2008 avsåg att få tillbaka människor i arbete. Men studien fann att den faktiskt bidrog till att fler gick i tidig ålderspension av dem som var i åldern 55–64 år. Ökningen var störst bland korttidsutbildade. Mer än 5 procent fler gick i tidig ålderspension då det blev svårare att få sjukpenning och sjukersättning. Vi kan notera att det är vanligare att manliga chefer tar ut tidig ålderspension, jämfört med kvinnliga maskinskötare inom tillverkningsindustrin. I vissa yrken är det dessutom vanligare att människor, trots pension, både orkar och faktiskt ges möjlighet att arbeta vidare om de har en specialkompetens som efterfrågas. Om vi endast kombinerar ekonomiska morötter med piskor finns en stor risk att vi ökar klyftan mellan grupper som både kan och vill fortsätta att yrkesarbeta och personer som av olika skäl inte längre kan eller orkar.Ta nytta av den forskning som vi har tagit fram. Ett hållbart och acceptabelt pensionssystem måste utformas utifrån personliga förutsättningar och förhållanden i arbetslivet. Ett hållbart arbetsliv för allt fler i vår åldrande befolkning fordrar att vi samtidigt beaktar faktorer som relaterar till biologisk/kroppslig ålder, mental/kognitiv ålder samt social ålder/livsloppsfas och våra attityder som är kopplade till ålder. Vi måste ta större hänsyn till olika förutsättningar och varierande funktionsförmåga och utifrån detta anpassa de åtgärder som gör att arbetslivet blir möjligt och hållbart för allt fler även i högre ålder.”Morötter” är viktigare för en god arbetshälsa och hög produktivitet än en piska i form av oron för en dålig ekonomi.Forskning visar att pedagogik som bygger på ”morötter” oftast är betydligt bättre än ”piskor” för att nå framgångsrika och långsiktiga mål. ”Morötter” i samhället, för organisationer, företag och individer är därför viktiga för god arbetshälsa och fortsatt produktivitet och kan bidra till ett längre arbetsliv även för grupper som tidigare inte ens klarat av att arbeta fram till pensionsåldern. Genom forskning inom området har bland annat swage-modellen utarbetats. Detta är ett verktyg som visar på komplexiteten i ett hållbart arbetsliv och tillsammans med systematiskt arbetsmiljöarbete, handlingsplaner och åtgärder syftar till ett mer hållbart arbetsliv. Morötter är enligt forskningen i detta sammanhang åtgärder för en god fysisk och mental arbetsmiljö, avpassad arbetsbelastning, stödjande teknik, att man kan anpassa arbetstakten, alternativa arbetstidsmodeller vid behov. Det är viktigt att man känner sig trygg och förväntas och tillåts vara delaktig, att man blir sedd av chefen och arbetskamraterna. Att de egna arbetsuppgifterna upplevs som meningsfulla och behövda av andra skapar självförverkligande och tillfredsställelse i arbetet. Att man känner att ens arbetsuppgifter och man själv är viktig för organisationen och företaget. Att man trots högre ålder inkluderas i olika nysatsningar och får tillgång till kompetensutveckling och inte blir åsidosatt eller åldersdiskriminerad. Utvärderingar visar att de äldre medarbetarna som fick några av dessa anpassningar och möjligheter var mer effektiva, utvilade, stimulerade när de var på arbetet samtidigt som sjukfrånvaron minskade. Vilket i sin tur bidrar till ett längre arbetsliv för grupper som tidigare inte klarat av att arbeta fram till pensionsåldern. I organisationer som bygger på en deltagar- och lärandekultur rustas de anställda för att klara omställningar, nya arbetsuppgifter och vid behov även yrkesbyten.Med en åldrande befolkning där allt fler lever allt längre behöver vi arbeta till en högre ålder i framtiden för att pensionssystemet ska hålla. Men ”morötter” är viktigare för en god arbetshälsa och hög produktivitet än en piska i form av oron för en dålig ekonomi. Det kräver också att vi ändrar våra attityder och förhållningssätt till äldre på arbetsmarknaden, vilket vi bäst gör genom att organisationer och företag får incitament till och erbjuder mer individanpassade arbetsvillkor, särskilt för personer i högre ålder. Låt oss därför använda den framtagna kunskapen i praktiken för att göra arbetslivet friskt och hållbart för alla åldrar.
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| 39. |
- Nilsson, Kerstin, et al.
(författare)
-
Vi är oroade över senare ålderspension
- 2017
-
Ingår i: Dagens Samhälle. - 1652-6511.
-
Tidskriftsartikel (populärvet., debatt m.m.)abstract
- Var fjärde person blir i dag sjuk till följd av sitt arbete. Att höja pensionsåldern för alla yrkesgrupper, utan konkreta åtgärder för att minska ohälsan, är därför problematiskt och mycket oroande. Det är, enligt forskarna, inte långsiktigt samhällsekonomiskt lönsamt att utan andra åtgärder höja pensionsåldern för alla. Vi – 54 forskare – är mycket oroade över konsekvenserna av att, som föreslagits, senarelägga ålderspensionen.Förslaget utgår i princip från arbetskraftsdeltagande i princip enbart styrs av ekonomin, medan forskningen visar att det bara är en av flera faktorer som styr hur länge och hur mycket människor väljer att arbeta.Det här sättet att lösa problemet med en åldrande befolkning och ett sviktande pensionssystem är inte samhällsekonomiskt lönsamt på lång sikt, utan riskerar bara att flytta runt folk mellan olika ersättningssystem. Pensionssystemet bygger på att vi ska arbeta en viss del av våra liv för att tjäna in vår pension. Vi bör dock inte enbart utgå ifrån ålder eller antalet år sedan en person föddes då korttidsutbildade generellt träder in på arbetsmarknaden tidigare än långtidsutbildade. De med kortare utbildningstid har alltså varit en del av arbetskraften från en yngre ålder. Människor med kortare utbildning har också oftare ett arbete som innebär påfrestningar som kan inverka negativt på hälsotillståndet och som till och med kan påskynda det biologiska åldrandet. Dessutom lever korttidsutbildade generellt sett inte lika länge som långtidsutbildade, vilket delvis även avspeglar skilda livs- och arbetsvillkor.Ta nytta av den forskning som vi har tagit fram. Ekonomin är självklart viktigt för att vi ska vilja arbeta, men den är som sagt enbart en av flera faktorer med betydelse vårt arbetsliv.Hälsotillståndet, både det fysiska och det mentala, har en avgörande betydelse för hur länge och hur mycket vi orkar arbeta. Ett fysiskt och mentalt belastande arbete är en stark riskfaktor för en nedsatt hälsa i slutet av arbetslivet. Arbetstid, arbetstakt och möjlighet till återhämtning spelar en allt större roll ju äldre vi blir. Andra aspekter är arbetsinnehåll, hur meningsfulla och stimulerande arbetsuppgifterna är, balansen mellan arbete och familjesituation och fritidsaktiviteter. Organisationskultur, ledarskapet, stöd i arbetet och kompetens har stor betydelse för om vi ska kunna och vilja arbeta till en högre ålder. Vi måste ta större hänsyn till olika förutsättningar och varierande funktionsförmåga och utifrån detta anpassa de åtgärder som gör att arbetslivet blir möjligt och hållbart för allt fler även i högre ålder.Ett hållbart och acceptabelt pensionssystem måste därför utformas utifrån personliga förutsättningar och förhållanden i arbetslivet. Ett hållbart arbetsliv för allt fler i vår åldrande befolkning fordrar att vi samtidigt beaktar faktorer som relaterar till biologisk/kroppslig ålder, mental/kognitiv ålder samt social ålder/livsloppsfas samt de attityder som är kopplade till ålder.
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| 40. |
- Persson, Erik, et al.
(författare)
-
How Will the Emerging Plurality of Lives Change? : How We Conceive of and Relate to Life?
- 2019
-
Ingår i: Challenges. - : MDPI AG. - 2078-1547.
-
Tidskriftsartikel (refereegranskat)abstract
- The project “A Plurality of Lives” was funded and hosted by the Pufendorf Institute for Advanced Studies at Lund University, Sweden. The aim of the project was to better understand how a second origin of life, either in the form of a discovery of extraterrestrial life, life developed in a laboratory, or machines equipped with abilities previously only ascribed to living beings, will change how we understand and relate to life. Because of the inherently interdisciplinary nature of the project aim, the project took an interdisciplinary approach with a research group made up of 12 senior researchers representing 12 different disciplines. The project resulted in a joint volume, an international symposium, several new projects, and a network of researchers in the field, all continuing to communicate about and advance the aim of the project.
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| 41. |
- Persson, Helena, et al.
(författare)
-
Charges drive selection of specific antibodies by phage display.
- 2010
-
Ingår i: Journal of Immunological Methods. - : Elsevier BV. - 1872-7905 .- 0022-1759. ; 353, s. 24-30
-
Tidskriftsartikel (refereegranskat)abstract
- Phage display technology has emerged as a leading approach to select proteins with improved properties for many different types of applications. The selection typically selects not only for improved binding properties but also for other factors such as efficiency of protein production and folding in Escherichia coli, the host in which the proteins and the phage are produced. Furthermore, the selection methodology is likely to influence the character of retrieved variants. We have now defined the extent whereby the charge of the displayed proteins influence the selection process, resulting in an increased average positive charge among selected proteins in comparison to the proteins that are harbored in the library before selection. Implications of and possible routes to minimize this effect are discussed.
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| 42. |
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| 43. |
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| 44. |
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| 45. |
- Persson, Mats, et al.
(författare)
-
Energy-resolved CT imaging with a photon-counting silicon-strip detector
- 2014
-
Ingår i: Medical Imaging 2014. - : SPIE - International Society for Optical Engineering. - 9780819498267 ; , s. 90333L-
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Konferensbidrag (refereegranskat)abstract
- Photon-counting detectors are promising candidates for use in the next generation of x-ray CT scanners. Among the foreseen benefits are higher spatial resolution, better trade-off between noise and dose, and energy discriminating capabilities. Silicon is an attractive detector material because of its low cost, mature manufacturing process and high hole mobility. However, it is sometimes claimed to be unsuitable for use in computed tomography because of its low absorption efficiency and high fraction of Compton scatter. The purpose of this work is to demonstrate that high-quality energy-resolved CT images can nonetheless be acquired with clinically realistic exposure parameters using a photon-counting silicon-strip detector with eight energy thresholds developed in our group. We use a single detector module, consisting of a linear array of 50 0.5 × 0.4 mm detector elements, to image a phantom in a table-top lab setup. The phantom consists of a plastic cylinder with circular inserts containing water, fat and aqueous solutions of calcium, iodine and gadolinium, in different concentrations. We use basis material decomposition to obtain water, calcium, iodine and gadolinium basis images and demonstrate that these basis images can be used to separate the different materials in the inserts. We also show results showing that the detector has potential for quantitative measurements of substance concentrations.
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| 46. |
- Persson, Mats, et al.
(författare)
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Energy-resolved CT imaging with a photon-counting silicon-strip detector
- 2014
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Ingår i: Physics in Medicine and Biology. - : IOP Publishing. - 0031-9155 .- 1361-6560. ; 59:22, s. 6709-6727
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Tidskriftsartikel (refereegranskat)abstract
- Photon-counting detectors are promising candidates for use in the next generation of x-ray computed tomography (CT) scanners. Among the foreseen benefits are higher spatial resolution, better trade-off between noise and dose and energy discriminating capabilities. Silicon is an attractive detector material because of its low cost, mature manufacturing process and high hole mobility. However, it is sometimes overlooked for CT applications because of its low absorption efficiency and high fraction of Compton scatter. The purpose of this work is to demonstrate that silicon is a feasible material for CT detectors by showing energy-resolved CT images acquired with an 80 kVp x-ray tube spectrum using a photon-counting silicon-strip detector with eight energy thresholds developed in our group. We use a single detector module, consisting of a linear array of 50 0.5 x 0.4 mm detector elements, to image a phantom in a table-top lab setup. The phantom consists of a plastic cylinder with circular inserts containing water, fat and aqueous solutions of calcium, iodine and gadolinium, in different concentrations. By using basis material decomposition we obtain water, calcium, iodine and gadolinium basis images and demonstrate that these basis images can be used to separate the different materials in the inserts. We also show results showing that the detector has potential for quantitative measurements of substance concentrations.
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| 47. |
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| 48. |
- Persson, Mats, et al.
(författare)
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Quantification of ring artifact visibility in CT
- 2012
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Ingår i: Medical Imaging 2012. - : SPIE - International Society for Optical Engineering. - 9780819489623 ; , s. 83132J-
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Konferensbidrag (refereegranskat)abstract
- Ring artifacts appear in computed tomography images if there are too large inhomogeneities between different detector elements. The question of how large inhomogeneities are acceptable is gaining in importance due to the development of energy discriminating photon counting CT, where detector homogeneity is an important design parameter. We propose using the systematic-to-statistical error quotient q, defined as the variance of the expected log-normalized count number between detector elements (dels) divided by the variance of log-normalized count numbers measured with the same del, as a metric of ring artifact visibility. With a simple observer study using simulated images, it is shown that rings are visible in the reconstructed image if q exceeds a threshold which lies close to 1.2·10 -3 for 1500 detector elements and 2000 projection angles. It is also shown by visual inspection of simulated images that the threshold value is, to a good approximation, inversely proportional to the number of angle measurements and independent of the number of detector elements. The results suggest that a simple oberver study, together with these scaling relationships, is sufficient for establishing sinogram homogeneity requirements for a particular reconstruction method.
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| 49. |
- Persson, Mats, et al.
(författare)
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Resolution improvement in x-ray imaging with an energy-resolving detector
- 2017
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Ingår i: Medical Imaging 2017. - : SPIE - International Society for Optical Engineering. - 9781510607095
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Konferensbidrag (refereegranskat)abstract
- In x-ray imaging, improving spatial resolution is an important goal, but developing detectors with smaller pixels is technically challenging. We demonstrate a technique for improving the spatial resolution by utilizing the fact that linear attenuation coefficients of all substances within the human body can be expressed, to a good approximation, as a linear combination of two basis functions, or three if there is iodine contrast present in the image. When the x rays pass an interface parallel to the beam direction, the exponential attenuation law makes the linear attenuation coefficient measured by the detector a nonlinear combination of the linear attenuation coefficients on each side of the interface. This so-called nonlinear partial volume effect causes the spectral response to be dependent on the steepness of interfaces in the imaged volume. In this work, we show how this effect can be used to improve the spatial resolution in spectral projection x-ray imaging and quantify the achievable resolution improvement. We simulate x-ray transmission imaging of sharp and gradual changes in the projected path length of iodine contrast with an ideal energy-resolving photon-counting detector and demonstrate that the slope of the transition can be determined from the registered spectrum. We simulate piecewise-linear transitions and show that the algorithm is able to reproduce the transition profile on a subpixel scale. The FWHM resolution of the method is 5-30 % of the pixel width. The results show that an energy-resolving detector can be used to improve spatial resolution when imaging interfaces of highly attenuating objects.
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| 50. |
- Persson, Mats, 1987-
(författare)
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Spectral Computed Tomography with a Photon-Counting Silicon-Strip Detector
- 2016
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Computed tomography (CT) is a widely used medical imaging modality. By rotating an x-ray tube and an x-ray detector around the patient, a CT scanner is able to measure the x-ray transmission from all directions and form an image of the patient’s interior. CT scanners in clinical use today all use energy-integrating detectors, which measure the total incident energy for each measurement interval. A photon-counting detector, on the other hand, counts the number of incoming photons and can in addition measure the energy of each photon by comparing it to a number of energy thresholds. Using photon- counting detectors in computed tomography could lead to improved signal-to-noise ratio, higher spatial resolution and improved spectral imaging which allows better visualization of contrast agents and more reliable quantitative measurements. In this Thesis, the feasibility of using a photon-counting silicon-strip detector for CT is investigated. In the first part of the Thesis, the necessary performance requirements on such a detector is investigated in two different areas: the detector element homogeneity and the capability of handling high photon fluence rates. A metric of inhomogeneity is proposed and used in a simulation study to evaluate different inhomogeneity compensation methods. Also, the photon fluence rate incident on the detector in a scanner in clinical use today is investigated for different patient sizes through dose rate measurements together with simulations of transmission through patient im- ages. In the second part, a prototype detector module is used to demonstrate new applications enabled by the energy resolution of the detector. The ability to generate material-specific images of contrast agents with iodine and gadolinium is demonstrated. Furthermore, it is shown theoretically and ex- perimentally that interfaces in the image can be visualized by imaging the so-called nonlinear partial volume effect. The results suggest that the studied silicon-strip detector is a promising candidate for photon-counting CT.
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