| 61. |
- Norrman, Eva, et al.
(författare)
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Optimization of image process parameters through factorial experiments using a flat panel detector
- 2007
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Ingår i: Physics in Medicine and Biology. - Bristol : IOP publishing. - 0031-9155 .- 1361-6560. ; 52:17, s. 5263-5276
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Tidskriftsartikel (refereegranskat)abstract
- In the optimization process of lumbar spine examinations, factorial experiments were performed addressing the question of whether the effective dose can be reduced and the image quality maintained by adjusting the image processing parameters. A 2(k)-factorial design was used which is a systematic and effective method of investigating the influence of many parameters on a result variable. Radiographic images of a Contrast Detail phantom were exposed using the default settings of the process parameters for lumbar spine examinations. The image was processed using different settings of the process parameters. The parameters studied were ROI density, gamma, detail contrast enhancement (DCE), noise compensation, unsharp masking and unsharp masking kernel (UMK). The images were computer analysed and an image quality figure (IQF) was calculated and used as a measurement of the image quality. The parameters with the largest influence on image quality were noise compensation, unsharp masking, unsharp masking kernel and detail contrast enhancement. There was an interaction between unsharp masking and kernel indicating that increasing the unsharp masking improved the image quality when combined with a large kernel size. Combined with a small kernel size however the unsharp masking had a deteriorating effect. Performing a factorial experiment gave an overview of how the image quality was influenced by image processing. By adjusting the level of noise compensation, unsharp masking and kernel, the IQF was improved to a 30% lower effective dose.
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| 62. |
- Birindwa, Archippe M., et al.
(författare)
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Decreased number of hospitalized children with severe acute lower respiratory infection after introduction of the pneumococcal conjugate vaccine in the Eastern Democratic Republic of the Congo.
- 2020
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Ingår i: Pan African Medical Journal. - : Pan African Medical Journal. - 1937-8688. ; 37
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Tidskriftsartikel (refereegranskat)abstract
- Introduction: acute lower respiratory infections (ALRI) are a leading killer of children under five worldwide including the Democratic Republic of the Congo (DR Congo). We aimed to determine the morbidity and case fatality rate due to ALRI before and after introduction of the 13-valent pneumococcal conjugate vaccine (PVC13) in DR Congo 2013. Methods: data were collected from medical records of children with a diagnosis of ALRI, aged from 2 to 59 months, treated at four hospitals in the eastern DR Congo. Two study periods were defined; from 2010 to 2012 (before introduction of PCV13) and from 2014 to 2015 (after PCV13 introduction). Results: out of 21,478 children admitted to the hospitals during 2010-2015, 2,007 were treated for ALRI. The case fatality rate among these children was 4.9%. Death was significantly and independently associated with malnutrition, severe ALRI, congenital disease and symptoms of fatigue. Among the ALRI hospitalised children severe ALRI decreased from 31% per year to 18% per year after vaccine introduction (p = 0.0002) while the fatality rate remained unchanged between the two study periods. Following introduction of PCV13, 63% of the children diagnosed with ALRI were treated with ampicillin combined with gentamicin while 33% received ceftriaxone and gentamicin. Conclusion: three years after PCV13 introduction in the Eastern part of the DR Congo, we found a reduced risk of severe ALRI among children below five years. Broad-spectrum antibiotics were frequently used for the treatment of ALRI in the absence of any microbiological diagnostic support.
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| 63. |
- Holst, Karen, et al.
(författare)
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Projection-based respiratory-resolved left ventricular volume measurements in patients using free-breathing double golden-angle 3D radial acquisition.
- 2019
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Ingår i: Magma. - : Springer Science and Business Media LLC. - 1352-8661. ; 32:3
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Tidskriftsartikel (refereegranskat)abstract
- To refine a new technique to measure respiratory-resolved left ventricular end-diastolic volume (LVEDV) in mid-inspiration and mid-expiration using a respiratory self-gating technique and demonstrate clinical feasibility in patients.Ten consecutive patients were imaged at 1.5 T during 10 min of free breathing using a 3D golden-angle radial trajectory. Two respiratory self-gating signals were extracted and compared: from the k-space center of all acquired spokes, and from a superior-inferior projection spoke repeated every 64 ms. Data were binned into end-diastole and two respiratory phases of 15% respiratory cycle duration in mid-inspiration and mid-expiration. LVED volume and septal-lateral diameter were measured from manual segmentation of the endocardial border.Respiratory-induced variation in LVED size expressed as mid-inspiration relative to mid-expiration was, for volume, 1 ± 8% with k-space-based self-gating and 8 ± 2% with projection-based self-gating (P = 0.04), and for septal-lateral diameter, 2 ± 2% with k-space-based self-gating and 10 ± 1% with projection-based self-gating (P = 0.002).Measuring respiratory variation in LVED size was possible in clinical patients with projection-based respiratory self-gating, and the measured respiratory variation was consistent with previous studies on healthy volunteers. Projection-based self-gating detected a higher variation in LVED volume and diameter during respiration, compared to k-space-based self-gating.
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| 64. |
- Velickaite, Vilma, et al.
(författare)
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Cognitive function in very old men does not correlate to biomarkers of Alzheimer's disease
- 2017
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Ingår i: Bmc Geriatrics. - : Springer Science and Business Media LLC. - 1471-2318. ; 17
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Tidskriftsartikel (refereegranskat)abstract
- Background: The Alzheimer's disease (AD) brain displays atrophy with amyloid-beta (A beta) and tau deposition, whereas decreased A beta 42 and increased tau are measured in cerebrospinal fluid (CSF). The aim of this study was to relate cognitive performance to the degree of brain atrophy, CSF biomarker levels and neuropathology in a cohort of aged men. Methods: Fifty-eight 86-92-year-old men from the Uppsala Longitudinal Study of Adult Men (ULSAM) cohort underwent cognitive testing, brain computed tomography and lumbar puncture. Atrophy was graded with established scales. Concentrations of CSF A beta 42, t-tau and p-tau were measured by ELISA. Thirteen brains were examined post mortem. Results: Forty-six of the individuals were considered non-demented, whereas twelve were diagnosed with dementia, either at baseline (n = 4) or during follow-up (n = 8). When comparing subjects with and without dementia, there were no differences in the degree of atrophy, although the mini mental state examination (MMSE) scoring correlated weakly with the degree of medial temporal atrophy (MTA) (p = 0.04). Moreover, the CSF biomarker levels did not differ significantly between healthy (n = 27) and demented (n = 8) subjects (median values 715 vs 472 pg/ml for A beta 42, 414 vs 427 pg/ml for t-tau and 63 vs 60 pg/ml for p-tau). Similarly, there were no differences in the biomarker levels between individuals with mild (n = 24) and severe (n = 11) MTA (median values 643 vs 715 pg/ml for A beta 42, 441 vs 401 pg/ml for t-tau and 64 vs 53 pg/ml for p-tau). Finally, the neuropathological changes did not correlate with any of the other measures. Conclusion: In this cohort of aged men only a weak correlation could be seen between cognitive performance and MTA, whereas the various neuroradiological, biochemical and neuropathological measures did not correlate with each other. Thus, AD biomarkers seem to be less informative in subjects of an advanced age.
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| 65. |
- Ahlander, Britt-Marie, 1954-, et al.
(författare)
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Development and validation of a questionnaire evaluating patient anxiety during Magnetic Resonance Imaging : the Magnetic Resonance Imaging- Anxiety Questionnaire (MRI-AQ)
- 2016
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Ingår i: Journal of Advanced Nursing. - : Wiley-Blackwell. - 0309-2402 .- 1365-2648. ; 72:6, s. 1368-1380
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Tidskriftsartikel (refereegranskat)abstract
- Aim: To develop and validate a new instrument measuring patient anxiety during Magnetic Resonance Imaging examinations, Magnetic Resonance Imaging-Anxiety Questionnaire.Background: Questionnaires measuring patients’ anxiety during Magnetic Resonance Imaging examinations have been the same as used in a wide range of conditions. To learn about patients’ experience during examination and to evaluate interventions, a specific questionnaire measuring patient anxiety during Magnetic Resonance Imaging is needed.Design: Psychometric cross-sectional study with test-retest design.Methods: A new questionnaire, Magnetic Resonance Imaging-Anxiety Questionnaire, was designed from patient expressions of anxiety in Magnetic Resonance Imagingscanners. The sample was recruited between October 2012–October 2014. Factor structure was evaluated with exploratory factor analysis and internal consistency with Cronbach’s alpha. Criterion-related validity, known-group validity and test-retest was calculated.Results: Patients referred for Magnetic Resonance Imaging of either the spine or the heart, were invited to participate. The development and validation of Magnetic Resonance Imaging-Anxiety Questionnaire resulted in 15 items consisting of two factors. Cronbach’s alpha was found to be high. Magnetic Resonance Imaging-Anxiety Questionnaire correlated higher with instruments measuring anxiety than with depression scales. Known-group validity demonstrated a higher level of anxiety for patients undergoing Magnetic Resonance Imaging scan of the heart than for those examining the spine. Test-retest reliability demonstrated acceptable level for the scale.Conclusion: Magnetic Resonance Imaging-Anxiety Questionnaire bridges a gap among existing questionnaires, making it a simple and useful tool for measuring patient anxiety during Magnetic Resonance Imaging examinations.
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| 66. |
- Christensson, Anders, et al.
(författare)
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Serum cystatin C advantageous compared with serum creatinine in the detection of mild but not severe diabetic nephropathy.
- 2004
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Ingår i: Journal of Internal Medicine. - : Wiley. - 1365-2796 .- 0954-6820. ; 256:6, s. 510-518
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVE: To determine whether serum cystatin C is more accurate than serum creatinine in the detection of diabetic nephropathy, also after adjustment for age.METHODS: Forty-one patients with type 1 and 82 patients with type 2 diabetes were evaluated with serum creatinine, serum cystatin C, and (51)Cr-EDTA clearance (reference method). Cystatin C was measured by a particle-enhanced turbidimetric method and creatinine by an enzymatic method. Statistical estimations were performed both without and with age adjustment created by z-scores for (51)Cr-EDTA clearance, creatinine, and cystatin C. The cut-off levels for glomerular filtration rate (GFR) ((51)Cr-EDTA clearance) were 60 and 80 mL min(-1) 1.73 m(-2), respectively, in absolute values and 80, 90 and 95% CIs, respectively, in age-adjusted values (z-scores).RESULTS: Estimations without age adjustment showed significantly (P = 0.0132) closer correlation for cystatin C (r = 0.817) versus (51)Cr-EDTA clearance as compared with creatinine (r = 0.678). However, when using age-adjusted values, the correlation for cystatin C and creatinine, respectively, versus (51)Cr-EDTA clearance did not differ. When comparing the diagnostic utilities for serum cystatin C versus serum creatinine in manifest renal impairment (GFR < 60 mL min(-1) 1.73 m(-2) or z-scores <-1.28 SD), there were no significant differences between the two markers whether age adjusted or not. However, for diagnosing mild nephropathy (GFR < 80 mL min(-1) 1.73 m(-2) or z-score -0.84 SD), serum cystatin C is significantly more useful.CONCLUSIONS: Serum cystatin C performed better compared with serum creatinine even when measured enzymatically, to detect mild diabetic nephropathy. However, serum creatinine was as efficient as serum cystatin C to detect advanced diabetic nephropathy.
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| 67. |
- Töyräs, Juha, et al.
(författare)
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Speed of sound in normal and degenerated bovine articular cartilage.
- 2003
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Ingår i: Ultrasound in Medicine and Biology. - : Elsevier. - 0301-5629 .- 1879-291X. ; 29:3, s. 447-454
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Tidskriftsartikel (refereegranskat)abstract
- The unknown and variable speed of sound may impair accuracy of the acoustic measurement of cartilage properties. In this study, relationships between the speed of sound and cartilage composition, mechanical properties and degenerative state were studied in bovine knee and ankle cartilage (n = 62). Further, the effect of speed variation on the determination of cartilage thickness and stiffness with ultrasound (US) indentation was numerically simulated. The speed of sound was significantly (n = 32, p < 0.05) dependent on the cartilage water content (r = -0.800), uronic acid content (per wet weight, r = 0.886) and hydroxyproline content (per wet weight, r = 0.887, n = 28), Young's modulus at equilibrium (r = 0.740), dynamic modulus (r = 0.905), and degenerative state (i.e., Mankin score) (r = -0.727). In addition to cartilage composition, mechanical and acoustic properties varied significantly between different anatomical locations. In US indentation, cartilage is indented with a US transducer. Deformation and thickness of tissue are calculated using a predefined speed of sound and used in determination of dynamic modulus. Based on the simulations, use of the mean speed of sound of 1627 m/s (whole material) induced a maximum error of 7.8% on cartilage thickness and of 6.2% on cartilage dynamic modulus, as determined with the US indentation technique (indenter diameter 3 mm). We believe that these errors are acceptable in clinical US indentation measurements.
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| 68. |
- Ge, Chenjie, 1991, et al.
(författare)
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Deep semi-supervised learning for brain tumor classification
- 2020
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Ingår i: BMC Medical Imaging. - : Springer Science and Business Media LLC. - 1471-2342. ; 20:1
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Tidskriftsartikel (refereegranskat)abstract
- Background: This paper addresses issues of brain tumor, glioma, classification from four modalities of Magnetic Resonance Image (MRI) scans (i.e., T1 weighted MRI, T1 weighted MRI with contrast-enhanced, T2 weighted MRI and FLAIR). Currently, many available glioma datasets often contain some unlabeled brain scans, and many datasets are moderate in size. Methods: We propose to exploit deep semi-supervised learning to make full use of the unlabeled data. Deep CNN features were incorporated into a new graph-based semi-supervised learning framework for learning the labels of the unlabeled data, where a new 3D-2D consistent constraint is added to make consistent classifications for the 2D slices from the same 3D brain scan. A deep-learning classifier is then trained to classify different glioma types using both labeled and unlabeled data with estimated labels. To alleviate the overfitting caused by moderate-size datasets, synthetic MRIs generated by Generative Adversarial Networks (GANs) are added in the training of CNNs. Results: The proposed scheme has been tested on two glioma datasets, TCGA dataset for IDH-mutation prediction (molecular-based glioma subtype classification) and MICCAI dataset for glioma grading. Our results have shown good performance (with test accuracies 86.53% on TCGA dataset and 90.70% on MICCAI dataset). Conclusions: The proposed scheme is effective for glioma IDH-mutation prediction and glioma grading, and its performance is comparable to the state-of-the-art.
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| 69. |
- Björk, Jonas, et al.
(författare)
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A new tool for predicting the probability of chronic kidney disease from a specific value of estimated GFR.
- 2010
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Ingår i: Scandinavian Journal of Clinical and Laboratory Investigation. - : Informa UK Limited. - 1502-7686 .- 0036-5513. ; Jul 1, s. 327-333
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Tidskriftsartikel (refereegranskat)abstract
- Abstract Objective. To demonstrate how patients' probability of having chronic kidney disease (CKD) stage 3-5 (measured GFR <60 mL/min/1.73 m(2)) can be predicted from a specific value of estimated glomerular filtration rate (eGFR). Material and methods. The probability of CKD stage 3-5 was predicted from a logistic regression model (n = 850) using three different eGFR prediction equations: Lund-Malmö, MDRD and CKD-EPI. Population weighting was used to illustrate how this probability varies in three different populations: original sample (55% true prevalence of CKD stage 3-5), a screening (6.7% prevalence) and a CKD population (84% prevalence). Results. All three eGFR-equations had high classification ability (area under the receiver-operating-characteristic curve = 97%). The probability of CKD stage 3-5 increased with decreasing eGFR, varied substantially among the populations studied and to some extent between the eGFR-equations. Using the Lund-Malmö equation as illustration, the probability of CKD stage 3-5 is > 90% only when eGFR is <38 mL/min/1.73 m(2) in a screening population, whereas it is > 90% already when eGFR is <51 mL/min/1.73 m(2) in a CKD population. Conversely, the probability of CKD stage 3-5 is <10% if eGFR > 59 mL/min/1.73 m(2) in a screening population, whereas it is <10% only when eGFR is > 88 mL/min/1.73 m(2) in a CKD population. Conclusion. Instead of reporting diagnostic accuracy as sensitivity, specificity, and predictive values, actual eGFR supplemented with the probability that it represents a true GFR <60 mL/min/1.73 m(2) may be more valuable for physicians. Clinical (pre-test) probability in the population must be considered when predicting this probability.
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| 70. |
- Björk, Jonas, et al.
(författare)
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Revised equations for estimating glomerular filtration rate based on the Lund-Malmö Study cohort.
- 2011
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Ingår i: Scandinavian Journal of Clinical and Laboratory Investigation. - : Informa UK Limited. - 1502-7686 .- 0036-5513. ; 71, s. 232-239
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Tidskriftsartikel (refereegranskat)abstract
- Abstract Objective. To increase the accuracy of estimated GFR (eGFR) from creatinine overall and at measured GFR ≥90 mL/min per 1.73 m(2) by revising the Lund-Malmö (LM) equations, to elaborate on more complex forms to improve the LM and CKD-EPI equations further, and to assess benefits of adding lean body mass (LBM). Material and methods. Swedish Caucasians (n = 850, 376 women; median 60, range 18-95 years) referred for GFR measurement (plasma iohexol-clearance: median 55, range 5-173 mL/min/1.73 m(2)) constituted the Lund-Malmö Study cohort. Bias, precision, accuracy, expressed as median absolute percentage difference and percentage of estimates ±10% (P(10)) and ±30% (P(30)) of measured GFR, and classification ability with respect to five GFR stages were compared with the original LM, CKD-EPI and MDRD equations. Results. LM Revised overall performed better than LM Original without LBM due to increased accuracy at measured GFR ≥90 mL/min/1.73 m(2). Further extensions of the CKD-EPI or LM equations did not substantially improve overall performance. In particular, the performance of LM Revised at measured GFR ≥90 mL/min/1.73 m(2) could not be improved further without decreasing accuracy and classification ability at lower GFR-levels. Adding LBM to the equations had no strong effect on accuracy. Conclusion. Comparisons with the CKD-EPI and MDRD equations suggest that the LM equations are superior for the present Swedish population, due to markedly higher accuracy of the LM equations at measured GFR <30 mL/min/1.73 m(2). However, the LM equations cannot be recommended for use in general clinical practice until validated in other populations.
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