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Derfalvi B, Boros KK, Szabo D, Bozsaki G, Cseh A, Rudas G, Muller KE, Veres G. Joint involvement, disease activity and quality of life in pediatric Crohn's disease - a cross-sectional study. Pediatr Rheumatol Online J 2022; 20:6. [PMID: 35093127 PMCID: PMC8801094 DOI: 10.1186/s12969-022-00664-z] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/15/2021] [Accepted: 01/06/2022] [Indexed: 12/13/2022] Open
Abstract
BACKGROUND Few published data describe how joint involvement, the most prevalent extraintestinal manifestation, affects quality of life (QoL) of children with Crohn's disease (CD). Arthritis and arthralgia rates in pediatric CD patients are reportedly 3-24% and 17-22%, respectively, but studies on pre-emptive and systematic screening of joint involvement with detailed musculoskeletal rheumatological exam are lacking. More detailed data collection on joint involvement improves our understanding of how arthropathy relates to disease activity and QoL measured by the Pediatric CD Activity Index (PCDAI) and IMPACT-III questionnaire. Our study aims were to assess joint involvement in pediatric CD and correlate it with the PCDAI and IMPACT-III. METHODS In this cross-sectional, observational study, a pediatric gastroenterologist assessed consecutively-seen pediatric CD patients at a tertiary care center. Patients were screened for prevalence of current and previous arthropathy, including arthritis, enthesitis and arthralgia. A single experienced pediatric rheumatologist evaluated detailed musculoskeletal history, joint status, and modified Juvenile Arthritis Multidimensional Assessment Reports (JAMAR). PCDAI, IMPACT-III, sacroiliac MRI, and HLA-B27 genetic testing were also completed. RESULTS A total of 82 (male:female, 1.2:1; age, 13.7 ± 3.2 years) patients were involved in this study. Mean disease duration at time of study was 21.6 ± 21 months; eight of the patients were newly-diagnosed. Of the 82 patients, 29 (35%) had evidence of arthritis; for 24 of those, this was revealed by physical exam during cross-sectional screening, and by prior documentation for the remaining five patients. Joint examination confirmed active arthritis in 8/24 (33%), active enthesitis in 1/24 (4%), and evidence of previous arthritis in 15/24 (62.5%) patients. Hip (41%) and knee (38%) joints were most commonly affected. Cumulative incidence of arthralgia was 48% (39/82), and 46% (18/39) of those patients had only arthralgia without arthritis, usually affecting the knee. Axial involvement was present in 10/82 (12%) patients. Joint involvement correlated with more severe CD disease activity, specifically higher PCDAI and lower IMPACT-III scores, and increased requirement for infliximab treatment. Sacroiliitis and HLA-B27 positivity were insignificant factors in this cohort. CONCLUSIONS When a rheumatologist performed the assessment, joint involvement in pediatric CD was more prevalent than previously reported, in this cross-sectional study. Arthritis was associated with more severe CD disease activity and lower QoL.
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Affiliation(s)
- Beata Derfalvi
- Department of Pediatrics, Dalhousie University/IWK Health Centre, Halifax, Nova Scotia, Canada.
| | - Kriszta Katinka Boros
- grid.11804.3c0000 0001 0942 98211st Department of Pediatrics, Semmelweis University, Budapest, Hungary
| | - Doloresz Szabo
- grid.11804.3c0000 0001 0942 98211st Department of Pediatrics, Semmelweis University, Budapest, Hungary
| | - Gabor Bozsaki
- grid.11804.3c0000 0001 0942 98211st Department of Pediatrics, Semmelweis University, Budapest, Hungary
| | - Aron Cseh
- grid.11804.3c0000 0001 0942 98211st Department of Pediatrics, Semmelweis University, Budapest, Hungary
| | - Gabor Rudas
- grid.11804.3c0000 0001 0942 9821MR Science Centre, Semmelweis University, Budapest, Hungary
| | - Katalin Eszter Muller
- grid.9679.10000 0001 0663 9479Institute for Translational Medicine, University of Pécs, Pécs, Hungary ,grid.413987.00000 0004 0573 5145Heim Pal National Pediatric Institute, Budapest, Hungary
| | - Gabor Veres
- grid.7122.60000 0001 1088 8582Paediatric Institute, University of Debrecen, Debrecen, Hungary
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2
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Hoel H, Heggelund L, Reikvam DH, Stiksrud B, Ueland T, Michelsen AE, Otterdal K, Muller KE, Lind A, Muller F, Dudman S, Aukrust P, Dyrhol-Riise AM, Holter JC, Trøseid M. Elevated markers of gut leakage and inflammasome activation in COVID-19 patients with cardiac involvement. J Intern Med 2021; 289:523-531. [PMID: 32976665 PMCID: PMC7536991 DOI: 10.1111/joim.13178] [Citation(s) in RCA: 58] [Impact Index Per Article: 19.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/03/2020] [Revised: 09/10/2020] [Accepted: 09/14/2020] [Indexed: 01/08/2023]
Abstract
BACKGROUND A high proportion of COVID-19 patients have cardiac involvement, even those without known cardiac disease. Downregulation of angiotensin converting enzyme 2 (ACE2), a receptor for SARS-CoV-2 and the renin-angiotensin system, as well as inflammatory mechanisms have been suggested to play a role. ACE2 is abundant in the gut and associated with gut microbiota composition. We hypothesized that gut leakage of microbial products, and subsequent inflammasome activation could contribute to cardiac involvement in COVID-19 patients. METHODS Plasma levels of a gut leakage marker (LPS-binding protein, LBP), a marker of enterocyte damage (intestinal fatty acid binding protein, IFABP), a gut homing marker (CCL25, ligand for chemokine receptor CCR9) and markers of inflammasome activation (IL-1β, IL-18 and their regulatory proteins) were measured at three time points (day 1, 3-5 and 7-10) in 39 hospitalized COVID-19 patients and related to cardiac involvement. RESULTS Compared to controls, COVID-19 patients had elevated plasma levels of LBP and CCL25 but not IFABP, suggesting impaired gut barrier function and accentuated gut homing of T cells without excessive enterocyte damage. Levels of LBP were twice as high at baseline in patients with elevated cardiac markers compared with those without and remained elevated during hospitalization. Also, markers of inflammasome activation were moderately elevated in patients with cardiac involvement. LBP was associated with higher NT-pro-BNP levels, whereas IL-18, IL-18BP and IL-1Ra were associated with higher troponin levels. CONCLUSION Patients with cardiac involvement had elevated markers of gut leakage and inflammasome activation, suggestive of a potential gut-heart axis in COVID-19.
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Affiliation(s)
- H Hoel
- Research Institute of Internal Medicine, Oslo University Hospital, Oslo, Norway.,Lovisenberg Diaconal Hospital, Oslo, Norway.,Institute of Clinical Medicine, University of Oslo, Oslo, Norway
| | - L Heggelund
- Department of Clinical Science, Faculty of Medicine, University of Bergen, Bergen, Norway.,Department of Internal Medicine, Drammen Hospital, Vestre Viken Hospital Trust, Drammen, Norway
| | - D H Reikvam
- Department of Infectious Diseases, Oslo University Hospital, Oslo, Norway
| | - B Stiksrud
- Department of Infectious Diseases, Oslo University Hospital, Oslo, Norway
| | - T Ueland
- Research Institute of Internal Medicine, Oslo University Hospital, Oslo, Norway.,Institute of Clinical Medicine, University of Oslo, Oslo, Norway.,Faculty of Health Sciences, K.G. Jebsen TREC, University of Tromsø, Tromsø, Norway
| | - A E Michelsen
- Research Institute of Internal Medicine, Oslo University Hospital, Oslo, Norway.,Institute of Clinical Medicine, University of Oslo, Oslo, Norway
| | - K Otterdal
- Research Institute of Internal Medicine, Oslo University Hospital, Oslo, Norway
| | - K E Muller
- Department of Internal Medicine, Drammen Hospital, Vestre Viken Hospital Trust, Drammen, Norway
| | - A Lind
- Department of Microbiology, Oslo University Hospital, Oslo, Norway
| | - F Muller
- Department of Microbiology, Oslo University Hospital, Oslo, Norway
| | - S Dudman
- Institute of Clinical Medicine, University of Oslo, Oslo, Norway.,Department of Microbiology, Oslo University Hospital, Oslo, Norway
| | - P Aukrust
- Research Institute of Internal Medicine, Oslo University Hospital, Oslo, Norway.,Institute of Clinical Medicine, University of Oslo, Oslo, Norway.,Section of Clinical Immunology and Infectious Diseases, Oslo University Hospital, Oslo, Norway
| | - A M Dyrhol-Riise
- Institute of Clinical Medicine, University of Oslo, Oslo, Norway.,Department of Infectious Diseases, Oslo University Hospital, Oslo, Norway
| | - J C Holter
- Institute of Clinical Medicine, University of Oslo, Oslo, Norway.,Department of Microbiology, Oslo University Hospital, Oslo, Norway
| | - M Trøseid
- Research Institute of Internal Medicine, Oslo University Hospital, Oslo, Norway.,Institute of Clinical Medicine, University of Oslo, Oslo, Norway.,Section of Clinical Immunology and Infectious Diseases, Oslo University Hospital, Oslo, Norway
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3
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Kreidler SM, Ringham BM, Muller KE, Glueck DH. Calculating Power for the General Linear Multivariate Model With One or More Gaussian Covariates. COMMUN STAT-THEOR M 2019; 48:1435-1448. [PMID: 31467462 DOI: 10.1080/03610926.2018.1433849] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
We describe a noncentral ℱ power approximation for hypotheses about fixed predictors in general linear multivariate models with one or more Gaussian covariates. The results apply to both single and multiple parameter hypotheses. The approach extends power approximations for models with only fixed predictors, and for models with a single Gaussian covariate. The new method approximates the noncentrality parameter under the alternative hypothesis using a Taylor series expansion for the matrix-variate beta distribution of type I. We used a Monte Carlo simulation to evaluate the accuracy of both the novel power approximation, and published power approximations. The simulation study accounted for randomness in both the predictors and the errors. We varied the number of outcomes, the number of parameters in the hypothesis, the per-treatment sample size, and the correlations between the random predictors and the outcomes. We demonstrate that our approximation is more accurate than published methods, both in small and large samples. We show that the run time for a single power calculation with the new method is on the order of milliseconds, compared to an average empirical simulation time of roughly three minutes. Approximate and simulated power can be calculated using the free, open-source rPowerlib package. (http://github.com/SampleSizeShop/rPowerlib).
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Affiliation(s)
| | - B M Ringham
- Department of Biostatistics and Informatics, University of Colorado Denver
| | - K E Muller
- Department of Health Outcomes and Policy, University of Florida, Gainesville
| | - D H Glueck
- Department of Biostatistics and Informatics, University of Colorado Denver
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Kovacs M, Papp M, Lakatos PL, Jacobsen S, Nemes E, Polgar M, Solyom E, Bodi P, Horvath A, Molnar K, Szabo D, Cseh A, Muller KE, Dezsofi A, Arato A, Veres G. Low mannose-binding lectin (MBL) is associated with paediatric inflammatory bowel diseases and ileal involvement in patients with Crohn disease. J Crohns Colitis 2013; 7:134-41. [PMID: 22504031 DOI: 10.1016/j.crohns.2012.03.008] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/30/2011] [Revised: 03/11/2012] [Accepted: 03/12/2012] [Indexed: 02/08/2023]
Abstract
BACKGROUND Mannose-binding lectin (MBL) is a pattern-recognition molecule of the innate immune system and may be involved in the pathogenesis of inflammatory bowel disease (IBD). Our aim was to assess the prevalence of MBL deficiency in a cohort of patients with paediatric-onset IBD and study whether it is associated with the clinical manifestations, serum antibody formation, or genetic factors. METHODS This prospective study included 159 paediatric patients (mean age: 14.0 years) with IBD [107 patients with Crohn disease (CD) and 52 patients with ulcerative colitis (UC)]. Furthermore, 95 controls were investigated. Serum samples were determined for MBL by enzyme-linked immunosorbent assay (ELISA) and for serologic markers [autoantibodies against Saccharomyces cerevisiae (ASCA) and perinuclear components of neutrophils (pANCA)] by indirect immunofluorescent assay. NOD2/CARD15 variants were tested by polymerase chain reaction/restriction fragment length polymorphism. RESULTS The MBL serum concentration was significantly lower in IBD patients(both with CD and UC) compared to controls (IBD, p=0.007, CD, p=0.04, UC p=0.004). Prevalence of low MBL level (<500 ng/mL) was significantly higher in both CD and UC groups compared to controls (p=0.002 and p=0.006). Furthermore, low MBL level was associated with isolated ileal involvement (p=0.01) and MBL deficiency (<100 ng/mL) with male gender (p=0.004) in patients with CD. We failed to confirm any correlation between MBL deficiency and serum autoantibodies or NOD2/CARD15 variants. CONCLUSIONS Our results suggest that low MBL associated with paediatric-onset IBD and ileal CD may be considered an additional marker of the IBD pathogenesis.
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Affiliation(s)
- Marta Kovacs
- Department of Paediatrics, Petz Aladár County and Teaching Hospital, Győr, Hungary
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5
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Kovacs M, Muller KE, Arato A, Lakatos PL, Kovacs JB, Varkonyi A, Solyom E, Polgar M, Nemes E, Guthy I, Tokodi I, Toth G, Horvath A, Tarnok A, Tomsits E, Csoszánszky N, Balogh M, Vass N, Bodi P, Dezsofi A, Gardos L, Micskey E, Papp M, Szucs D, Cseh A, Molnar K, Szabo D, Veres G. Diagnostic yield of upper endoscopy in paediatric patients with Crohn's disease and ulcerative colitis. Subanalysis of the HUPIR registry. J Crohns Colitis 2012; 6:86-94. [PMID: 22261532 DOI: 10.1016/j.crohns.2011.07.008] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/22/2011] [Revised: 07/13/2011] [Accepted: 07/14/2011] [Indexed: 02/08/2023]
Abstract
BACKGROUND, AIMS According to Porto Criteria upper gastrointestinal (UGI) endoscopy is recommended in patients with suspected inflammatory bowel disease (IBD). Nevertheless, previous studies revealed frequent involvement of UGI tract even in patients with ulcerative colitis (UC). The aim of the present study was to determine the diagnostic role of esophagogastroduodenoscopy (EGD) and assess the prevalence and different aspects of UGI involvement in children registered in the Hungarian Pediatric IBD Registry (HUPIR) from 1st of January 2007 to 31th of December 2009. METHODS Twenty seven institutes provided prospective follow-up data about newly diagnosed IBD patients to HUPIR. The registry was based on detailed questionnaire (76 parameters) involving anamnestic data, laboratory findings, activity indexes, diagnostic procedures, endoscopic examinations (EGD and ileocolonoscopy), and histological data. Localization and phenotype of disease were based on the Montreal classification criteria. RESULTS During the 3-year period 420 children were diagnosed with IBD, 265 (63%) of them had Crohn's disease (CD), 130 (31%) UC, and 25 (6%) IBD-unclassified (IBD-U). The mean age at diagnosis was 13.2 years (range: 1.2-18 years). EGD was performed in 237 patients (56%), in most cases in patients suffering from CD. Macroscopic lesions on EGD were noted in 64% of patients with CD and 40% of children with UC. Characteristic lesions for CD (ulcer, erosion, aphthous lesion, and granuloma) were noted in 31% of CD patients, however, EGD helped to establish the final diagnosis in 9% of CD patients (diagnostic yield, 9%). CONCLUSIONS There was a high frequency of UGI involvement in children with CD and UC. One third of CD patients showed significant lesions at upper endoscopy and one patient out of ten had real diagnostic help from EGD.
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Affiliation(s)
- Marta Kovacs
- Petz Aladár County Teaching Hosp., Győr, Hungary
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6
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Glueck DH, Karimpour-Fard A, Mandel J, Muller KE. Probabilities for separating sets of order statistics. STATISTICS-ABINGDON 2010; 44:145-153. [PMID: 21243084 DOI: 10.1080/02331880902986984] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Abstract
Consider a set of order statistics that arise from sorting samples from two different populations, each with their own, possibly different distribution functions. The probability that these order statistics fall in disjoint, ordered intervals and that of the smallest statistics, a certain number come from the first populations is given in terms of the two distribution functions. The result is applied to computing the joint probability of the number of rejections and the number of false rejections for the Benjamini-Hochberg false discovery rate procedure.
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Affiliation(s)
- D H Glueck
- Department of Preventive Medicine and Biometrics, University of Colorado Denver, Campus Box B119, 4200 East Ninth Avenue, Denver, CO 80262, USA
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7
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Glueck DH, Karimpour-Fard A, Mandel J, Hunter L, Muller KE. Fast Computation by Block Permanents of Cumulative Distribution Functions of Order Statistics from Several Populations. COMMUN STAT-THEOR M 2008; 37:2815-2824. [PMID: 19865590 DOI: 10.1080/03610920802001896] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
The joint cumulative distribution function for order statistics arising from several different populations is given in terms of the distribution functions of the populations. The computational cost of our formula in the case of two populations is still exponential in the worst case, but it is a dramatic improvement compared to the general formula by Bapat and Beg. In the case when only the joint distribution function of a subset of the order statistics of fixed size is needed, the complexity is polynomial, for the case of two populations.
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Affiliation(s)
- D H Glueck
- Department of Preventive Medicine and Biometrics, University of Colorado Denver, Denver, Colorado, USA
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8
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Abstract
The Benjamini-Hochberg procedure is widely used in multiple comparisons. Previous power results for this procedure have been based on simulations. This article produces theoretical expressions for expected power. To derive them, we make assumptions about the number of hypotheses being tested, which null hypotheses are true, which are false, and the distributions of the test statistics under each null and alternative. We use these assumptions to derive bounds for multiple dimensional rejection regions. With these bounds and a permanent based representation of the joint density function of the largest p-values, we use the law of total probability to derive the distribution of the total number of rejections. We derive the joint distribution of the total number of rejections and the number of rejections when the null hypothesis is true. We give an analytic expression for the expected power for a false discovery rate procedure that assumes the hypotheses are independent.
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Affiliation(s)
- D H Glueck
- Department of Preventive Medicine and Biometrics, University of Colorado Denver and Health Sciences Center, Denver, Colorado, USA
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9
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Abstract
Scientists may wish to analyze correlated outcome data with constraints among the responses. For example, piecewise linear regression in a longitudinal data analysis can require use of a general linear mixed model combined with linear parameter constraints. Although well developed for standard univariate models, there are no general results that allow a data analyst to specify a mixed model equation in conjunction with a set of constraints on the parameters. We resolve the difficulty by precisely describing conditions that allow specifying linear parameter constraints that insure the validity of estimates and tests in a general linear mixed model. The recommended approach requires only straightforward and noniterative calculations to implement. We illustrate the convenience and advantages of the methods with a comparison of cognitive developmental patterns in a study of individuals from infancy to early adulthood for children from low-income families.
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Affiliation(s)
- L J Edwards
- Department of Biostatistics, School of Public Health, The University of North Carolina, Chapel Hill 27599-7420, USA.
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10
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Hemminger BM, Zong S, Muller KE, Coffey CS, DeLuca MC, Johnston RE, Pisano ED. Improving the detection of simulated masses in mammograms through two different image-processing techniques. Acad Radiol 2001; 8:845-55. [PMID: 11724039 DOI: 10.1016/s1076-6332(03)80762-6] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
RATIONALE AND OBJECTIVES The purpose of this study was to determine whether contrast-limited adaptive histogram equalization (CLAHE) or histogram-based intensity windowing (HIW) improves the detection of simulated masses in dense mammograms. MATERIALS AND METHODS Simulated masses were embedded in portions of mammograms of patients with dense breasts; the mammograms were digitized at 50 microm per pixel, 12 bits deep. In two different experiments, images were printed both with no processing applied and with related parameter settings of two image-processing methods. A simulated mass was embedded in a realistic background of dense breast tissue, with its position varied. The key variables in each trial included the position of the mass, the contrast levels of the mass relative to the background, and the selected parameter settings for the image-processing method. RESULTS The success in detecting simulated masses on mammograms with dense backgrounds depended on the parameter settings of the algorithms used. The best HIW setting performed better than the best fixed-intensity window setting and better than no processing. Performance with the best CLAHE settings was no different from that with no processing. In the HIW experiment, there were no significant differences in observer performance between processing conditions for radiologists and nonradiologists. CONCLUSION HIW should be tested in clinical images to determine whether the detection of masses by radiologists can be improved. CLAHE processing will probably not improve the detection of masses on clinical mammograms.
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Affiliation(s)
- B M Hemminger
- Department of Radiology, University of North Carolina, Chapel Hill 27599-7510, USA
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11
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Abstract
To compensate for a power analysis based on a poor estimate of variance, internal pilot designs use some fraction of the planned observations to reestimate error variance and modify the final sample size. Ignoring the randomness of the final sample size may bias the final variance estimate and inflate test size. We propose and evaluate three different tests that control test size for an internal pilot in a general linear univariate model with fixed predictors and Gaussian errors. Test 1 uses the first sample plus those observations guaranteed to be collected in the second sample for the final variance estimate. Test 2 depends mostly on the second sample for the final variance estimate. Test 3 uses the unadjusted variance estimate and modifies the critical value to bound test size. We also examine three sample-size modification rules. Only test 2 can control conditional test size, align with a modification rule, and provide simple power calculations. We recommend it if the minimum second (incremental) sample is at least moderate (perhaps 20). Otherwise, the bounding test appears to have the highest power in small samples. Reanalyzing published data highlights some advantages and disadvantages of the various tests.
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Affiliation(s)
- C S Coffey
- Department of Biostatistics, University of Alabama School of Public Health, Birmingham 35294-0022, USA.
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12
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Pisano ED, Cole EB, Major S, Zong S, Hemminger BM, Muller KE, Johnston RE, Walsh R, Conant E, Fajardo LL, Feig SA, Nishikawa RM, Yaffe MJ, Williams MB, Aylward SR. Radiologists' preferences for digital mammographic display. The International Digital Mammography Development Group. Radiology 2000; 216:820-30. [PMID: 10966717 DOI: 10.1148/radiology.216.3.r00se48820] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
PURPOSE To determine the preferences of radiologists among eight different image processing algorithms applied to digital mammograms obtained for screening and diagnostic imaging tasks. MATERIALS AND METHODS Twenty-eight images representing histologically proved masses or calcifications were obtained by using three clinically available digital mammographic units. Images were processed and printed on film by using manual intensity windowing, histogram-based intensity windowing, mixture model intensity windowing, peripheral equalization, multiscale image contrast amplification (MUSICA), contrast-limited adaptive histogram equalization, Trex processing, and unsharp masking. Twelve radiologists compared the processed digital images with screen-film mammograms obtained in the same patient for breast cancer screening and breast lesion diagnosis. RESULTS For the screening task, screen-film mammograms were preferred to all digital presentations, but the acceptability of images processed with Trex and MUSICA algorithms were not significantly different. All printed digital images were preferred to screen-film radiographs in the diagnosis of masses; mammograms processed with unsharp masking were significantly preferred. For the diagnosis of calcifications, no processed digital mammogram was preferred to screen-film mammograms. CONCLUSION When digital mammograms were preferred to screen-film mammograms, radiologists selected different digital processing algorithms for each of three mammographic reading tasks and for different lesion types. Soft-copy display will eventually allow radiologists to select among these options more easily.
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Affiliation(s)
- E D Pisano
- Dept of Radiology, University of North Carolina CB7510, Chapel Hill, NC 27599-7510, USA.
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13
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Abstract
For small samples of Gaussian repeated measures with missing data, Barton and Cramer recommended using the EM algorithm for estimation and reducing the degrees of freedom for an analogue of Rao's F approximation to Wilks' test. Computer simulations led to the conclusion that the modified test was slightly conservative for total sample size of N=40. Here we consider additional methods and smaller sample sizes, Nin¿12,24¿. We describe analogues of the Pillai-Bartlett trace, Hotelling-Lawley trace and Geisser-Greenhouse corrected univariate tests which allow for missing data. Eleven sample size adjustments were examined which replace N by some function of the numbers of non-missing pairs of responses in computing error degrees of freedom. Overall, simulation results allowed concluding that an adjusted test can always control test size at or below the nominal rate, even with as few as 12 observations and up to 10 per cent missing data. The choice of method varies with the test statistic. Replacing N by the mean number of non-missing responses per variable works best for the Geisser-Greenhouse test. The Pillai-Bartlett test requires the stronger adjustment of replacing N by the harmonic mean number of non-missing pairs of responses. For Wilks' and Hotelling-Lawley, an even more aggressive adjustment based on the minimum number of non-missing pairs must be used.
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Affiliation(s)
- D J Catellier
- Department of Biostatistics CB#7400, University of North Carolina, Chapel Hill 27599-7400, USA.
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14
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Abstract
Kaposi's sarcoma of the breast is extremely rare. We report a case of a patient with AIDS presenting with Kaposi's sarcoma localized to the breast and review another published case of a patient with AIDS and disseminated cutaneous Kaposi's sarcoma with breast involvement. Although rare, the diagnosis should be considered in patients with breast lumps.
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Affiliation(s)
- K A Hamed
- Section of Infectious Disease, Department of Veterans Affairs Medical Center, Bay Pines, Florida, USA.
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15
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Hemminger BM, Dillon AW, Johnston RE, Muller KE, Deluca MC, Coffey CS, Pisano ED. Effect of display luminance on the feature detection rates of masses in mammograms. Med Phys 1999; 26:2266-72. [PMID: 10587207 DOI: 10.1118/1.598740] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
Our purpose in this study was to determine the importance of the luminance range of the display system for the detection of simulated masses in mammograms. Simulated masses were embedded in selected portions (512 x 512 pixels) of mammograms digitized at 50 micro pixels, 12 bits deep. The masses were embedded in one of four quadrants in the image. An observer experiment was conducted in which the observer's task was to determine in which quadrant the mass is located. The key variables involved in each trial included the position of the mass, the contrast level of the mass, and the luminance of the display. The contrast of the mass with respect to the background was fixed to one of four selected contrast levels. The digital images were printed to film, and displayed on a mammography lightbox. The display luminance was controlled by placing neutral density films between the laser printed films of mammographic backgrounds and the lightbox. The resulting maximum luminances examined in this study ranged from 34 cd/m2 to 2056 cd/m2. Twenty observers viewed 80 different images (20 observations at each of 4 different mass contrast levels) under each of the 5 luminance conditions for a total of 800 independent observations per observer. An analysis of variance yielded no statistically significant correlation between the luminance range of the display and the feature detection rate of the simulated masses in mammograms. However, the performance of the lower luminance display systems (less than 300 cd/m2), may be reduced due to the high levels of ambient light found in many reading environments.
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Affiliation(s)
- B M Hemminger
- Department of Radiology, University of North Carolina 27599-7515, USA.
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Bullitt E, Liu A, Aylward SR, Coffey C, Stone J, Mukherji SK, Muller KE, Pizer SM. Registration of 3D cerebral vessels with 2D digital angiograms: clinical evaluation. Acad Radiol 1999; 6:539-46. [PMID: 10894063 DOI: 10.1016/s1076-6332(99)80432-2] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
RATIONALE AND OBJECTIVES The purpose of this study was to evaluate the accuracy and speed of a new, semiautomatic method of three-dimensional (3D)-two-dimensional (2D) vascular registration. This method should help guide endovascular procedures by allowing interpretation of each digital subtraction angiographic (DSA) image in terms of precreated, 3D vessel trees that contain "parent-child" connectivity information. MATERIALS AND METHODS Connected, 3D vessel trees were created from segmented magnetic resonance (MR) angiograms. Eleven total DSA images were registered with such trees by using both our method and the current standard (manual registration). The accuracy of each method was compared by using repeated-measures analysis of variance with correction for heterogeneity of variance to evaluate separation of curve pairs on the view plane. Subjective clinical comparisons of the two registration methods were evaluated with the sign test. Registration times were evaluated for both methods and also as a function of the error in the initial estimate of MR angiographic position. RESULTS The new registration method produced results that were numerically superior to those of manual registration (P < .001) and was subjectively judged to be as good as or better by clinical reviewers. Registration time with the new method was faster (P < .001). If the rotational error in the initial estimate of MR angiographic position is less than 10 degrees around each axis, the registration itself took only 1-2 minutes. CONCLUSION This method is quicker than and produces results as good as or better than those of manual registration. This method should be able to calculate an initial registration matrix during endovascular embolization and adjust that matrix intermittently with registration updates provided by automatic tracking systems.
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Affiliation(s)
- E Bullitt
- Medical Image Display and Analysis Group, University of North Carolina at Chapel Hill, 27599, USA
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17
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Boxwala AA, Chaney EL, Fritsch DS, Raghavan S, Coffey CS, Major SA, Muller KE. Comparison of computer workstation with light box for detecting setup errors from portal images. Int J Radiat Oncol Biol Phys 1999; 44:711-6. [PMID: 10348303 DOI: 10.1016/s0360-3016(99)00050-4] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
PURPOSE Observer studies were conducted to test the hypothesis that radiation oncologists using a computer workstation for portal image analysis can detect setup errors at least as accurately as when following standard clinical practice of inspecting portal films on a light box. METHODS AND MATERIALS In a controlled observer study, nine radiation oncologists used a computer workstation, called PortFolio, to detect setup errors in 40 realistic digitally reconstructed portal radiograph (DRPR) images. PortFolio is a prototype workstation for radiation oncologists to display and inspect digital portal images for setup errors. PortFolio includes tools for image enhancement; alignment of crosshairs, field edges, and anatomic structures on reference and acquired images; measurement of distances and angles; and viewing registered images superimposed on one another. The test DRPRs contained known in-plane translation or rotation errors in the placement of the fields over target regions in the pelvis and head. Test images used in the study were also printed on film for observers to view on a light box and interpret using standard clinical practice. The mean accuracy for error detection for each approach was measured and the results were compared using repeated measures analysis of variance (ANOVA) with the Geisser-Greenhouse test statistic. RESULTS The results indicate that radiation oncologists participating in this study could detect and quantify in-plane rotation and translation errors more accurately with PortFolio compared to standard clinical practice. CONCLUSIONS Based on the results of this limited study, it is reasonable to conclude that workstations similar to PortFolio can be used efficaciously in clinical practice.
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Affiliation(s)
- A A Boxwala
- Department of Radiation Oncology, University of North Carolina, Chapel Hill 27599, USA
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18
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Abstract
Wittes and Brittain recommended using an 'internal pilot study' to adjust sample size. The approach involves five steps in testing a general linear hypothesis for a general linear univariate model, with Gaussian errors. First, specify the design, hypothesis, desired test size, power, a smallest 'clinically meaningful' effect, and a speculated error variance. Second, conduct a power analysis to choose provisionally a planned sample size. Third, collect a specified proportion of the planned sample as the internal pilot sample, and estimate the variance (but do not test the hypothesis). Fourth, update the power analysis with the variance estimate to adjust the total sample size. Fifth, finish the study and test the hypothesis with all data. We describe methods for computing exact test size and power under this scenario. Our analytic results agree with simulations of Wittes and Brittain. Furthermore, our exact results apply to any general linear univariate model with fixed predictors, which is much more general than the two-sample t-test considered by Wittes and Brittain. In addition, our results allow for examination of the impact on test size of internal pilot studies for more complicated designs in the framework of the general linear model. We examine the impact of (i) small samples, (ii) allowing the planned sample size to decrease, (iii) the choice of internal pilot sample size, and (iv) the maximum allowable size of the second sample. All affect test size, power and expected total sample size. We present a number of examples including one that uses an internal pilot study in a three-group analysis of variance.
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Affiliation(s)
- C S Coffey
- Department of Biostatistics, University of North Carolina, Chapel Hill 27599-7400, USA
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19
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Warshauer DM, Wehmueller MD, Molina PL, Muller KE, DeLuca MC, Lee JK. Hepatic enhancement and metastatic lesion conspicuity on CT scans: influence of intravenous glucagon and oral CT contrast material. Radiology 1997; 202:394-8. [PMID: 9015064 DOI: 10.1148/radiology.202.2.9015064] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
PURPOSE To determine the effect of glucagon and orally administered contrast material on hepatic enhancement and metastatic lesion conspicuity on computed tomographic (CT) scans. MATERIALS AND METHODS Nine patients with a history of hepatic metastasis underwent two CT examinations with intravenously administered contrast material. Each patient was given orally administered CT contrast material for the first examination. No oral contrast material was given in the second examination. Five patients underwent the initial CT with intravenous administration of 1 mg of glucagon; the second examination was performed without glucagon. Four patients were administered glucagon before the second examination, but no glucagon was administered before the first. Attenuation in the liver, portal vein, and aorta was measured by observers blinded to whether the patient had been given glucagon. Lesion conspicuity was rated on a continuous scale. RESULTS Greater mean hepatic enhancement was noted on scans of patients in whom oral contrast material was administered (mean, 52 HU) versus those in whom no oral contrast material was administered (mean, 47 HU; P = .019). Glucagon was not associated with greater hepatic enhancement. Neither oral contrast material nor glucagon had a significant effect on lesion conspicuity. CONCLUSION Oral CT contrast material is associated with a small increase in hepatic enhancement that does not appear to be clinically important. Glucagon does not appear to affect hepatic enhancement or lesion conspicuity in humans.
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Affiliation(s)
- D M Warshauer
- Department of Radiology, University of North Carolina School of Medicine, Chapel Hill 27599-7510, USA
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20
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Mukherji SK, Schiro S, Castillo M, Kwock L, Muller KE, Blackstock W. Proton MR spectroscopy of squamous cell carcinoma of the extracranial head and neck: in vitro and in vivo studies. AJNR Am J Neuroradiol 1997; 18:1057-72. [PMID: 9194433 PMCID: PMC8337295] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
PURPOSE To determine the ability of in vitro one-dimensional and two-dimensional proton MR spectroscopy to help differentiate squamous cell carcinoma of the extracranial head and neck from normal tissues and to correlate the in vitro observations with clinical studies. METHODS In vitro 1-D and 2-D correlated proton MR spectroscopy (11 T) was performed in tissue specimens of squamous cell carcinoma of the head and neck (n = 19), in normal tissue (n = 13), in metastatic cervical lymph nodes (n = 3), and in a squamous cell carcinoma cell line. In vivo 1-D proton MR spectroscopy (1.5 T) was performed in patients with squamous cell carcinoma (n = 7) and in healthy volunteers (n = 7). The ratio of the areas under the choline (Cho) and creatine (Cr) resonances were calculated for 1-D proton MR spectra for the in vitro tissue studies and correlated with the in vivo studies. Data from in vitro 2-D correlated spectroscopy were analyzed for differences in the presence or absence of various metabolites in samples of tumor and normal tissue. Statistical analysis consisted of 2 x 2 factorial repeated measures analysis of variance (ANOVA), discriminate analysis, and chi2 test. RESULTS The mean in vitro 1-D proton MR spectroscopic Cho/Cr ratio was significantly higher in tumor than in normal tissue. The difference between the mean ratios appeared to increase with increasing echo time. All in vivo tumor Cho/Cr ratios were greater than the calculated mean in vitro tumor ratio, whereas six of the seven volunteers had no detectable Cho and Cr resonances. Two-dimensional correlated MR spectroscopic data revealed that a variety of amino acids have a significantly greater likelihood of being detected in tumor than in normal tissues. CONCLUSIONS One-dimensional and 2-D proton MR spectroscopy can help differentiate primary squamous cell carcinoma and nodal metastases containing squamous cell carcinoma from normal tissue both in vitro and in vivo. In addition, 2-D spectroscopy can help identify the presence of certain amino acids in squamous cell carcinoma that are not detected in normal tissue.
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Affiliation(s)
- S K Mukherji
- Department of Radiology, University of North Carolina School of Medicine, Chapel Hill 27599, USA
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21
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Beard DV, Molina PL, Muller KE, Denelsbeck KM, Hemminger BM, Perry JR, Braeuning MP, Glueck DH, Bidgood WD, Mauro M. Interpretation time of serial chest CT examinations with stacked-metaphor workstation versus film alternator. Radiology 1995; 197:753-8. [PMID: 7480751 DOI: 10.1148/radiology.197.3.7480751] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
PURPOSE Interpretation time of serial staging chest CT cases, which each contained current and previous examinations, with a simple prototype workstation called filmstack was experimentally compared with interpretation time with a film alternator. MATERIALS AND METHODS The filmstack displayed a "stack" of sections for each examination; user controls allowed rapid selection of preset attenuation windows and both synchronized and unsynchronized scrolling. Eight radiologists were timed as they used the filmstack and the film alternator to interpret four ergonomically complex serial CT cases. RESULTS All reports dictated on the basis of findings with filmstack and film were of acceptable clinical accuracy. The time to examine a case with filmstack was significantly faster than the time with film, including the time to load and unload the alternator (99% confidence [P = .01]). There was no statistically significant difference in interpretation time between filmstack and prehung film. CONCLUSION Use of a low-cost stacked CT workstation with a single 1,024 x 1,024 monitor is an effective means of interpreting cases that require comparison of multiple CT examinations.
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Affiliation(s)
- D V Beard
- Department of Radiology, University of North Carolina School of Medicine, Chapel Hill, USA
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22
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Abstract
The treatment of idiopathic membranous glomerulopathy remains an enigma. We have reviewed many of the important clinical trials concerning membranous glomerulopathy using a meta-analysis and a secondary pooled analysis to test the effects of corticosteroid or alkylating, therapy compared with no treatment on renal survival and complete remission of the nephrotic syndrome. A search was performed using MEDLINE (1968 through 1993) for articles on idiopathic membranous glomerulopathy and glomerulonephritis. Bibliographies of articles were reviewed for completeness. Sixty-nine articles were reviewed. Meta-analysis was performed for four trials that evaluated corticosteroids compared with no treatment and for three trials that evaluated alkylating therapy compared with no treatment. Pooled analysis was performed on randomized and prospective studies (10 studies) and then with 22 case series added. All studies evaluated renal biopsy-proven disease. Meta-analysis was performed on the relative chance of being in complete remission for each study. Renal survival could be evaluated by pooled analysis only. For pooled analyses, Cox's proportional hazard and logistic regression models were used to test the effect of therapy on renal survival and the nephrotic syndrome, respectively. Data concerning gender, nephrotic syndrome, and geographic region were used in all statistical models. Evaluation of renal survival revealed no differences by treatment group (P > 0.1). By meta-analysis, the relative chance of complete remission was not improved for corticosteroid-treated patients (1.55; 95% confidence interval, 0.99 to 2.44; P > 0.1), but was improved for patients treated with alkylating agents (4.8; 95% confidence interval, 1.44 to 15.96; P < 0.05) when compared with no treatment. Pooled analysis of randomized and prospective studies, as well pooled analysis with all studies, supported the findings of the meta-analysis. Corticosteroids or alkylating therapy did not improve renal survival in idiopathic membranous glomerulopathy. Complete remission of the nephrotic syndrome was observed more frequently with the use of alkylating agents.
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Affiliation(s)
- S L Hogan
- Department of Medicine, University of North Carolina at Chapel Hill, USA
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Hemminger BM, Johnston RE, Rolland JP, Muller KE. Introduction to perceptual linearization of video display systems for medical image presentation. J Digit Imaging 1995; 8:21-34. [PMID: 7734526 DOI: 10.1007/bf03168052] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
The perceptual linearization of video display systems should play a significant role in medical image presentation. It maximizes the faithfulness of information transfer to the human observer; it provides a method for standardizing the appearance of images across different display devices; and it allows for calculation of the inherent contrast resolution of different display devices. This paper provides insight into the process of perceptual linearization by decomposing it into the digital driving level-to-monitor luminance relationship, the monitor luminance-to-human brightness perception relationship, and the construction of a linearization function derived from these two relationships. A discussion of previous work in these areas is given. We then compare and contrast the results of previous work with recent experiments in our laboratory and related work in vision and computer science. We conclude that (1) sufficiently good visual models exist for agreeing on a standard method of calculating the perceptual linearization function; (2) improvements in the resolution and luminance distribution of the digital-to-analog circuitry in display systems are required for medical imaging; and (3), methods for calculating a linearization remapping from a perceptual linearization function currently have significant error and should be replaced with methods that minimize perceptual error.
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Affiliation(s)
- B M Hemminger
- Department of Radiology, University of North Carolina at Chapel Hill 27599-7510, USA
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24
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Puff DT, Pisano ED, Muller KE, Johnston RE, Hemminger BM, Burbeck CA, McLelland R, Pizer SM. A method for determination of optimal image enhancement for the detection of mammographic abnormalities. J Digit Imaging 1994; 7:161-71. [PMID: 7858011 DOI: 10.1007/bf03168534] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
We present a paradigm for empirical evaluation of digital image enhancement algorithms for mammography that uses psychophysical methods for implementation and analysis of a clinically relevant detection task. In the experiment, the observer is asked to detect and assign to a quadrant, or indicate the absence of, a simulated mammographic structure characteristic of cancer embedded in a background image of normal breast tissue. Responses are indicated interactively on a computer workstation. The parameter values for the enhancement applied to the composite image may be varied on each trial, and structure detection performance is estimated for each enhancement condition. Preliminary investigations have provided insight into an appropriate viewing duration, and furthermore, suggest that nonradiologists may be used under this methodology for the tasks investigated thus far, for predicting parameter values for clinical investigation. We are presently using this method in evaluating several contrast enhancement algorithms of possible benefit in mammography. These methods enable an objective, clinically relevant evaluation, for the purpose of optimal parameter determination or performance assessment, of digital image-processing methods potentially used in mammography.
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Affiliation(s)
- D T Puff
- Department of Biomedical Engineering, University of North Carolina-Chapel Hill
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25
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Beard DV, Hemminger BM, Perry JR, Mauro MA, Muller KE, Warshauer DM, Smith MA, Zito AJ. Interpretation of CT studies: single-screen workstation versus film alternator. Radiology 1993; 187:565-9. [PMID: 8475309 DOI: 10.1148/radiology.187.2.8475309] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
A prototype single-screen workstation with a 2,048 x 2,560-pixel high-brightness monitor, 0.11-second image display time, and simple ergonomic design was compared to a conventional horizontal film alternator in diagnostic interpretation of chest computed tomography (CT) studies. Four radiologists used either the workstation or film alternator in interpretation of studies obtained in 10 patients. A counterbalanced within-subject repeated measures experimental design was used. Response times were analyzed for both methods of interpretation. Grades of excellent, acceptable, and unacceptable were assigned by a blinded "grader" to reports of the radiologists. The average time needed for an interpretation at the workstation was 5.65 minutes. No interpretations were graded unacceptable. Retrospective power analysis showed that 16 observers rather than four would have been required to show that use of the workstation was faster than the alternator. With this 95% confidence interval, the workstation interpretation time is clinically equivalent to that with the alternator. These data show that this type of workstation has practical application in interpretation of CT, magnetic resonance imaging, and ultrasound studies.
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Affiliation(s)
- D V Beard
- Department of Radiology, School of Medicine, University of North Carolina, Chapel Hill 27599-7510
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26
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Abstract
The purpose of this study was to identify personal characteristics that predict individual differences in acute FEV1 response to ozone exposure. Response and predictor data were collected on 290 white male volunteers 18 to 32 yr of age who were each exposed to one of six concentrations of ozone between 0.0 and 0.40 part per million. The sample was divided into an exploratory sample of 96 and a confirmatory sample of 194 subjects. Exploratory analysis indicated that ozone, age, and several other variables explained a significant proportion of the variance in response. In the confirmatory sample, only age and ozone concentration predicted FEV1 decrement. For the combined sample ozone explained 31% of the variance, with age accounting for an additional 4%. The model predicted a decreasing response with increasing age for all nonzero ozone concentrations. For exposure to 0.40 ppm, the model predicts decrements in FEV1 of 1.07 and 0.47 L for 18- and 30-yr-old subjects, respectively. We concluded that for white male subjects age was a significant predictor of response, with older subjects being less responsive to ozone. Furthermore, we demonstrated that exploratory analysis without control of type I statistical error rates may result in apparent findings that cannot be replicated.
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Affiliation(s)
- W F McDonnell
- Clinical Research Branch, U.S. Environmental Protection Agency, Research Triangle Park, NC 27711
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27
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Abstract
We report on the results a 3-year project which had as its goal the development of methods to enhance radiation portal films to improve their readability. We had previously reported on a portal film enhancement technique, contrast limited adaptive histogram equalization, which could enhance low contrast detail, but degraded sharply contrasted edges. A new method, unsharp masking followed by contrast limited adaptive histogram equalization, now appears to overcome this problem. A clinical trial to test whether enhanced portal films could be read more accurately than standard ones was undertaken. The trial involved 12 readers from two institutions doing 276 readings. In this trial the enhanced films were judged to be of higher quality than the non-enhanced films (p < .001) and were read more accurately (p = .026). The usefulness and difficulties of routinely performing portal film enhancement in a busy radiation therapy department are discussed.
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Affiliation(s)
- J Rosenman
- Department of Radiation Oncology, University of North Carolina Hospitals, Chapel Hill 27514
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28
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Abstract
A survey of basic ideas in statistical power analysis demonstrates the advantages and ease of using power analysis throughout the design, analysis, and interpretation of research. The power of a statistical test is the probability of rejecting the null hypothesis of the test. The traditional approach to power involves computation of only a single power value. The more general power curve allows examining the range of power determinants, which are sample size, population difference, and error variance, in traditional ANOVA. Power analysis can be useful not only in study planning, but also in the evaluation of existing research. An important application is in concluding that no scientifically important treatment difference exists. Choosing an appropriate power depends on: a) opportunity costs, b) ethical trade-offs, c) the size of effect considered important, d) the uncertainty of parameter estimates, and e) the analyst's preferences. Although precise rules seem inappropriate, several guidelines are defensible. First, the sensitivity of the power curve to particular characteristics of the study, such as the error variance, should be examined in any power analysis. Second, just as a small type I error rate should be demonstrated in order to declare a difference nonzero, a small type II error should be demonstrated in order to declare a difference zero. Third, when ethical and opportunity costs do not preclude it, power should be at least .84, and preferably greater than .90.
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Affiliation(s)
- K E Muller
- Department of Biostatistics, University of North Carolina, Chapel Hill 27599
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Falk RJ, Hogan SL, Muller KE, Jennette JC. Treatment of progressive membranous glomerulopathy. A randomized trial comparing cyclophosphamide and corticosteroids with corticosteroids alone. The Glomerular Disease Collaborative Network. Ann Intern Med 1992; 116:438-45. [PMID: 1371211 DOI: 10.7326/0003-4819-116-6-438] [Citation(s) in RCA: 65] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
OBJECTIVE To determine if deterioration in renal function could be ameliorated by adding cyclophosphamide to corticosteroid therapy in patients with progressive membranous glomerulopathy. DESIGN Randomized, controlled treatment trial. Patients were followed for a mean of 29.2 +/- 17.1 months. SETTING Collaborative network of 120 university and private-practice nephrologists. PARTICIPANTS Patients with membranous glomerulopathy whose renal function deteriorated (as evidenced by doubling of the serum creatinine level, a 50% fall in the glomerular filtration rate, or a sustained serum creatinine level of greater than 2.0 mg/dL [reciprocal creatinine value, 0.5], or whose nephrotic range proteinuria persisted in association with morbid complications. Of 156 patients with biopsy-proven membranous glomerulopathy, 36 became eligible for randomization. Twenty-six of these 36 patients were randomly assigned to receive one of the two treatments. INTERVENTIONS Pulse methylprednisolone, oral corticosteroids, and 6 months of intravenous cyclophosphamide or alternate-day corticosteroid therapy alone. MAIN RESULTS At entry, no statistical differences were found between the treatment groups in duration of renal disease, age, gender, serum creatinine level, 24-hour urine protein excretion, or biopsy stage. The groups showed no difference in mean arterial blood pressure during follow-up. Four of the 13 patients receiving corticosteroids alone and 4 of the 13 patients receiving corticosteroids plus intravenous cyclophosphamide progressed to end-stage renal disease during follow-up. Reciprocal creatinine values tested at 6-month intervals showed no statistical differences between treatment groups at any time point. The log of the 24-hour protein excretion values showed no statistical differences between treatment groups after treatment. The power to detect a substantial improvement in renal function, defined as a doubling of the reciprocal of the serum creatinine, at the 0.05 significance level was 0.92. CONCLUSIONS Combination therapy with intravenous cyclophosphamide and corticosteroids, when compared with corticosteroid therapy alone, does not improve renal function in patients with progressive membranous glomerulopathy.
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Abstract
Literature on dose-effects functions of carboxyhemoglobin (COHb) and human behavior is internally inconsistent. A recent study was performed to describe such a function for tracking behavior in humans (7). No significant effects were found, however, even for COHb levels up to ca. 17%. The present review and analysis of published data was undertaken to attempt to reduce uncertainty about COHb dose-effects functions. Dose-effects data from six laboratory animal operant behavior studies were reviewed. Maximum COHb levels ranged from 33 to 59%. Data were converted to a common metric and dose-effects functions were fitted. The preferred function was nonlinear, with a shallow slope, indicating small effects (if any) for COHb levels less than ca. 20%. As COHb increased further, the slope of the function became progressively steeper. Review of the human dose-effects function publications for COHb and behavior revealed that no significant findings had survived the test of direct or partial replication. Other studies found no significant effects. A dose-effects curve was fitted to the human data from one study (7) and compared to the laboratory animal curves. Extrapolation of the human curve was used to suggest that the dose-effects curves for humans and laboratory animals were of similar form and that effects of COHb on behavior in man are small or absent below ca. 20%. It is also possible that some uncontrolled variables are affecting the results so that COHb produces effects only some of the time. No conclusion can be drawn from the body of literature due to the divergence of results.
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Affiliation(s)
- V A Benignus
- United States Environmental Protection Agency, Human Studies Division, Research Triangle Park, NC 27711
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31
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Abstract
A total of seventy-four men divided into five groups performed a compensatory tracking task for 4 hr with group mean carboxyhemoglobin (COHb) levels of 0.9, 5.6, 6.1, 11.4 or 16.6%. In all but one group, COHb was formed in approximately 5 min by having the subject breathe a high concentration of carbon monoxide (CO) from a Douglas bag. An appropriate low level of CO in the exposure/test chamber maintained the elevated COHb for the 4-hr duration of the experiment. A slow COHb formation group, not exposed to CO during bag breathing, which was only exposed to low-level CO in the exposure/testing chamber, served as a positive control. Even though mean tracking error scores increased in a nearly monotone manner as a function of COHb, the effects were not statistically significant. Even at the highest dose, the increase in tracking error was small. The increased mean error score due to rapid formation was virtually the same as that due to slow formation.
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Affiliation(s)
- V A Benignus
- United States Environmental Protection Agency, Human Studies Division, Research Triangle Park, NC 27711
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Harbin TJ, Benignus VA, Muller KE, Barton CN. The effects of low-level carbon monoxide exposure upon evoked cortical potentials in young and elderly men. Neurotoxicol Teratol 1988; 10:93-100. [PMID: 3398828 DOI: 10.1016/0892-0362(88)90072-4] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
The neurophysiological effects of acute, low-level carbon monoxide (CO) exposure are not well known. This experiment investigated the effects of a 5% carboxyhemoglobin level upon two indices of neurophysiological function, reaction time and the late positive component of the visual evoked potential in young and elderly men. Results indicated (1) no effects of CO upon any of the neurophysiological indices and (2) greater absorption of CO by young than by elderly men. These results, along with those of other studies, indicate that acute, low-level CO exposure is probably not neurotoxic, in normal, healthy men.
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Affiliation(s)
- T J Harbin
- U.S. Environmental Protection Agency, Research Triangle Park, NC 27711
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33
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Abstract
It has been generally accepted that carboxyhemoglobin levels between 10-20% produce mild headaches, dizziness and/or nausea. Experimental double blind exposures of 18 healthy, nonsmoking young men at rest to 7,000-24,000 ppm CO, designed to elevate COHb to 15-20% in 3-5 minutes, were followed by exposure to 232 ppm CO designed to maintain COHb level for a total of 130 minutes. Resulting COHb values were 16-23%. These COHb values did not produce significantly more symptoms (as reported in an open-ended questioning) than reported in the control group (n = 23). Subjects were especially queried about headache, dizziness and nausea. The symptoms which were previously reported in clinical studies of CO poisoning may have resulted from CO exposure in combination with (a) exposure to other substances, (b) stress due to the event that precipitated medical attention or (c) higher COHb levels before the first blood sample was taken.
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Affiliation(s)
- V A Benignus
- U.S. Environmental Protection Agency, Neurotoxicology Division, Research Triangle Park, NC 27711
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Abstract
Experiments by Putz et al. concerning the effect of carbon monoxide (CO) exposure on compensatory tracking and monitoring in healthy young men were replicated. Task and procedural variables were reproduced as closely as practical. Subjects were exposed to either room air or 100 ppm CO. Mean carboxyhemoglobin (COHb) levels in the high CO exposure groups were 5.1% for Putz et al. (70 ppm exposure), and 8.24% for the present study (100 ppm exposure). In both studies elevated COHb produced a statistically significant increase over time in log mean absolute deviation scores (tracking error) with respect to control groups. The magnitude of the effect was smaller in the present study, perhaps because of subtle methodological or training differences between studies. The relationship between task difficulty and magnitude of CO-induced dysfunction remains unresolved. In contrast to Putz et al., no statistically significant effect of COHb in monitoring behavior was found. The failure to replicate this feature of may reflect the large differences in baseline performance, and higher variance in the present study.
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Dyer RS, Muller KE, Janssen R, Barton CN, Boyes WK, Benignus VA. Neurophysiological effects of 30 day chronic exposure to toluene in rats. Neurobehav Toxicol Teratol 1984; 6:363-8. [PMID: 6514099] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Long-Evans hooded rats were exposed to 1000 ppm toluene or 0 ppm toluene 6 hr/day, 5 days/week for 30 days. Following removal from the exposure conditions (18-26 hr) flash-evoked potentials were recorded to paired light flashes and pentylenetetrazol (PTZ) seizure properties were examined. No alterations were found in the response to the first flash, but alterations in the recoverability of the nervous system were demonstrated by significant latency shifts in the response to the second of the paired flashes, using first flash latencies as covariates. No significant alterations were found in PTZ seizures. The data indicated that at these exposure levels toluene produced a small but significant alteration in brain function, even after toluene had been completely metabolized.
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Benignus VA, Muller KE, Barton CN, Bittikofer JA. Toluene blood level following subcutaneous injection of toluene in the rat. Environ Res 1984; 33:441-453. [PMID: 6714192 DOI: 10.1016/0013-9351(84)90041-0] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
A model of toluene level in blood following subcutaneous injection of toluene mixed with polyoxyethylated-vegetable-oil vehicle was developed. The purpose was to provide a means of predicting dose received for subsequent toxicologic studies for any time and dose combination. The pharmacokinetics were of secondary interest. Using data from 111 rats, a four-parameter equation was devised to predict the time course of toluene blood level from 20-480 min post dosing, for dose levels of 50-1000 mg/kg. Blood concentrations rose at a rate which was independent of dose level. Maximum blood levels were uniquely determined by dose level. Blood levels fell at different rates depending upon dose level. Injection exposure, when compared to inhalation, has the advantages of (a) low expense, (b) low equipment requirements, and (c) simplicity. The disadvantage is, for some experiments, poor temporal stimulation of the normal route of administration, inhalation.
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Benignus VA, Muller KE, Graham JA, Barton CN. Toluene levels in blood and brain of rats as a function of toluene level in inspired air. Environ Res 1984; 33:39-46. [PMID: 6692812 DOI: 10.1016/0013-9351(84)90006-9] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
The relationship of toluene concentration in blood and brain to the concentration of toluene in inspired air has not been explicitly studied. Sixty rats were exposed by inhalation to 50, 100, 500, or 1000 ppm toluene for 3 hr. Immediately following exposure, venous blood samples and whole brains were collected and assayed for toluene levels. For several empirical reasons, the natural logarithm (log) of toluene tissue levels were predicted in a linear model from log toluene levels in air. An additional 10 rats were exposed to 550 ppm toluene for 8 hr in order to verify that the 3-hr exposure was sufficient to produce near-asymptotic levels of toluene in blood and brain. Log brain toluene concentration was significantly higher than log blood concentration by an additive constant. The ratio of brain to blood toluene level was estimated as 1.56/1. Three- and eight-hour exposure results did not differ, thus indicating that these results would hold for toluene exposures of 3 hr or greater.
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Muller KE, Barton CN, Benignus VA. Recommendations for appropriate statistical practice in toxicologic experiments. Neurotoxicology 1984; 5:113-25. [PMID: 6542184] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/05/2023]
Abstract
Appropriate statistical practice in toxicologic research is reviewed. The problem centers on the antagonistic needs to discover toxic effects and avoid false indictments of harmless compounds. Specific problems which distort error rates include having many dependent variables, conducting many tests on a variable, data snooping, lack of statistical power and 5) violations of statistical assumptions. Solution strategies include top down planning, designing efficient experiments, balancing type I and type II error rates, selecting hypotheses and 5) using appropriate statistical analysis methods. Top down planning and the "leapfrog" design strategy are particularly emphasized.
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Benignus VA, Muller KE, Barton CN, Bittikofer JA. Toluene levels in blood and brain of rats during and after respiratory exposure. Toxicol Appl Pharmacol 1981; 61:326-34. [PMID: 7330875 DOI: 10.1016/0041-008x(81)90353-7] [Citation(s) in RCA: 60] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
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Otto DA, Benignus VA, Muller KE, Barton CN. Effects of age and body lead burden on CNS function in young children. I. slow cortical potentials. Electroencephalogr Clin Neurophysiol 1981; 52:229-39. [PMID: 6169500 DOI: 10.1016/0013-4694(81)90052-3] [Citation(s) in RCA: 62] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
The effects of body Pb burden on slow cortical potentials were studied in 63 children aged 13-75 months. Slow wave (SW) voltage during sensory conditioning varied as a linear function of blood lead (PbB) level. The slope of this function, moreover, changed systematically with age. For children under 5 years of age, SW voltage tended to be positive at low PbBs and to be negative above 30 micrograms/dl. For children over 5 years of age, SW voltage tended to be negative at low PbBs and to be less negative (or positive) above 30 micrograms/dl. These results provide evidence of altered CNS function at the lowest Pb effect level ever reported.
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Benignus VA, Otto DA, Muller KE, Seiple KJ. Effects of age and body lead burden on CNS function in young children. II. EEG spectra. Electroencephalogr Clin Neurophysiol 1981; 52:240-8. [PMID: 6169501 DOI: 10.1016/0013-4694(81)90053-5] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
This study explored the effects of age and PbB upon EEG power spectra and various measures of hemispheric laterality in children, aged 13-75 months, watching a display (cartoon). The following are the principle conclusions: (1) The delta- and theta-band amplitude decreased with age. (2) When only bilaterally synchronized EEG between P3 and P4 was considered, the amplitude of P3 was estimated as greater than P4 in all frequency bands and for all ages. Previous reports have not shown lateral EEG dominance in children below 75 months. (3) When lateral dominance measures consider only the relationship between synchronized EEG at P3 and P4, bilateral communality in the delta band increased with age. (4) Increased PbB generally produced an increase in the relative amplitude of synchronized EEG between P3 and P4 in all frequency bands. This was true for PbB levels well below 15 micrograms/dl, among the lowest level PbB effects previously reported. No clinical or behavioral effects of PbB values have been reported below 15 micrograms/dl. It appears to be theoretically and practically important to understand the functional significance of bilaterally synchronized activity. The signal processing of the CNS can be explored using these methods. Greater understanding of these data would help define the extent and etiology of PbB effects on the CNS
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Muller KE, Christiansen DH, Smith J. Guidelines for managing datasets, programs and printouts in scientific research. Comput Programs Biomed 1981; 13:281-8. [PMID: 7318424 DOI: 10.1016/0010-468x(81)90105-7] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
This paper presents guidelines and naming conventions to assist in managing datasets, programs and printouts for small to medium sized research projects. First, the limits and nature of the type of project are considered. A number of definitions are included to help further specify the problem. Four main areas are addressed. First, a consistent set of rules for naming programs and datasets is presented. Next, techniques for storing and archiving the programs and datasets are presented, using the naming conventions just developed. Third, rules for printout management are given, based on the naming rules. Finally, the documentation of all components of the project is discussed. Although trivial to implement, adherence to the naming rules provides a sound basis for a high quality, easy-to-use documentation system.
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