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Hu Z.,University of Iowa | Abramoff M.D.,University of Iowa | Abramoff M.D.,Iowa City Medical Center | Kwon Y.H.,University of Iowa | And 2 more authors.
Investigative Ophthalmology and Visual Science | Year: 2010

PURPOSE. To develop an automated approach for segmenting the neural canal opening (NCO) and cup at the level of the retinal pigment epithelium (RPE)/Bruch's membrane (BM) complex in spectral-domain optical coherence tomography (SD-OCT) volumes. To investigate the correspondence and discrepancy between the NCO-based metrics and the clinical disc margin on fundus photographs of glaucoma subjects. METHODS. SD-OCT scans and corresponding stereo fundus photographs of the optic nerve head were obtained from 68 eyes of 34 patients with glaucoma or glaucoma suspicion. Manual planimetry was performed by three glaucoma experts to delineate a reference standard (RS) for cup and disc margins from the images. An automated graph-theoretic approach was used to identify the NCO and cup. NCO-based metrics were compared with the RS. RESULTS. Compared with the RS disc margin, the authors found mean unsigned and signed border differences of 2.81 ± 1.48 pixels (0.084 ± 0.044 mm) and -0.99 ± 2.02 pixels (-0.030 ± 0.061 mm), respectively, for NCO segmentation. The correlations of the linear cup-to-disc (NCO) area ratio, disc (NCO) area, rim area, and cup area of the algorithm with the RS were 0.85, 0.77, 0.69, and 0.83, respectively. CONCLUSIONS. In most eyes, the NCO-based 2D metrics, as estimated by the novel automated graph-theoretic approach to segment the NCO and cup at the level of the RPE/BM complex in SD-OCT volumes, correlate well with RS. However, a small discrepancy exists in NCO-based anatomic structures and the clinical disc margin of the RS in some eyes. © Association for Research in Vision and Ophthalmology. Source


Eber M.R.,Center for Disease Dynamics | Eber M.R.,University of Southern California | Shardell M.,University of Maryland Baltimore County | Schweizer M.L.,University of Iowa | And 4 more authors.
PLoS ONE | Year: 2011

Background: Knowledge of seasonal trends in hospital-associated infection incidence may improve surveillance and help guide the design and evaluation of infection prevention interventions. We estimated seasonal variation in the frequencies of inpatient bloodstream infections (BSIs) caused by common bacterial pathogens and examined associations of monthly BSI frequencies with ambient outdoor temperature, precipitation, and humidity levels. Methods: A database containing blood cultures from 132 U.S. hospitals collected between January 1999 and September 2006 was assembled. The database included monthly counts of inpatient blood cultures positive for several clinically important Gram-negative bacteria (Acinetobacter spp, Escherichia coli, Klebsiella pneumoniae, and Pseudomonas aeruginosa) and Gram-positive bacteria (Enterococcus spp and Staphylococcus aureus). Monthly mean temperature, total precipitation, and mean relative humidity in the postal ZIP codes of participating hospitals were obtained from national meteorological databases. Results: A total of 211,697 inpatient BSIs were reported during 9,423 hospital-months. Adjusting for long-term trends, BSIs caused by each Gram-negative organism examined were more frequent in summer months compared with winter months, with increases ranging from 12.2% for E. coli (95% CI 9.2-15.4) to 51.8% for Acinetobacter (95% CI 41.1-63.2). Summer season was associated with 8.7% fewer Enterococcus BSIs (95% CI 11.0-5.8) and no significant change in S. aureus BSI frequency relative to winter. Independent of season, monthly humidity, monthly precipitation, and long-term trends, each 5.6°C (10°F) rise in mean monthly temperature corresponded to increases in Gram-negative bacterial BSI frequencies ranging between 3.5% for E. coli (95% CI 2.1-4.9) to 10.8% for Acinetobacter (95% CI 6.9-14.7). The same rise in mean monthly temperature corresponded to an increase of 2.2% in S. aureus BSI frequency (95% CI 1.3-3.2) but no significant change in Enterococcus BSI frequency. Conclusions: Summer season and higher mean monthly outdoor temperature are associated with substantially increased frequency of BSIs, particularly among clinically important Gram-negative bacteria. © 2011 Eber et al. Source


Kumar N.,University of Miami | Liang D.,University of Iowa | Comellas A.,University of Iowa | Chu A.D.,NASA | Abrams T.,Iowa City Medical Center
Journal of Exposure Science and Environmental Epidemiology | Year: 2013

A hybrid approach is proposed to estimate exposure to fine particulate matter (PM 2.5) at a given location and time. This approach builds on satellite-based aerosol optical depth (AOD), air pollution data from sparsely distributed Environmental Protection Agency (EPA) sites and local time-space Kriging, an optimal interpolation technique. Given the daily global coverage of AOD data, we can develop daily estimate of air quality at any given location and time. This can assure unprecedented spatial coverage, needed for air quality surveillance and management and epidemiological studies. In this paper, we developed an empirical relationship between the 2 km AOD and PM 2.5 data from EPA sites. Extrapolating this relationship to the study domain resulted in 2.3 million predictions of PM 2.5 between 2000 and 2009 in Cleveland Metropolitan Statistical Area (MSA). We have developed local time-space Kriging to compute exposure at a given location and time using the predicted PM 2.5. Daily estimates of PM 2.5 were developed for Cleveland MSA between 2000 and 2009 at 2.5 km spatial resolution; 1.7 million (∼79.8%) of 2.13 million predictions required for multiyear and geographic domain were robust. In the epidemiological application of the hybrid approach, admissions for an acute exacerbation of chronic obstructive pulmonary disease (AECOPD) was examined with respect to time-space lagged PM 2.5 exposure. Our analysis suggests that the risk of AECOPD increases 2.3% with a unit increase in PM 2.5 exposure within 9 days and 0.05° (∼5 km) distance lags. In the aggregated analysis, the exposed groups (who experienced exposure to PM 2.5 >15.4 μg/m 3) were 54% more likely to be admitted for AECOPD than the reference group. The hybrid approach offers greater spatiotemporal coverage and reliable characterization of ambient concentration than conventional in situ monitoring-based approaches. Thus, this approach can potentially reduce exposure misclassification errors in the conventional air pollution epidemiology studies. © 2013 Nature America, Inc. Source


Booth B.M.,University of Arkansas for Medical Sciences | Mengeling M.,University of Iowa | Torner J.,University of Iowa | Sadler A.G.,Iowa City Medical Center
Journal of Traumatic Stress | Year: 2011

The association of rape history and sexual partnership with alcohol and drug use consequences in women veterans is unknown. Midwestern women veterans (N = 1,004) completed a retrospective telephone interview assessing demographics, rape history, substance abuse and dependence, depression, and posttraumatic stress disorder (PTSD). One third met lifetime criteria for substance use disorder (SUD), half reported lifetime completed rape, a third childhood rape, one quarter in-military rape, 11% sex with women. Lifetime SUD was higher for women with rape history (64% vs. 44%). Women with women as sex partners had significantly higher rates of all measures of rape, and also lifetime substance use disorder. Postmilitary rape, sex partnership, and current depression were significantly associated with lifetime SUD in multivariate models (odds ratio = 2.3, 3.6, 2.1, respectively). Many women veterans have a high need for comprehensive mental health services. Published 2011. This article is a US Government work and is in the public domain in the USA. Source


Zhang L.,University of Iowa | Sonka M.,University of Iowa | Folk J.C.,University of Iowa | Russell S.R.,University of Iowa | And 2 more authors.
Investigative Ophthalmology and Visual Science | Year: 2014

Purpose. We reported a fully automated method to identify and quantify the thickness of the outer retinal-subretinal (ORSR) layer from clinical spectral-domain optical coherence tomography (SD-OCT) scans of choroidal neovascularization (CNV) due to exudative age-related macular degeneration (eAMD). Methods. A total of 23 subjects with CNV met eligibility. Volumetric SD-OCT scans of 23 eyes were obtained (Zeiss Cirrus, 200 × 200 × 1024 voxels). In a subset of eyes, scans were repeated. The OCT volumes were analyzed using our standard parameters and using a 3-dimensional (3D) graph-search approach with an adaptive cost function. A retinal specialist graded the segmentation as generally accurate, local segmentation inaccuracies, or failure. Reproducibility on repeat scans was analyzed using root mean square coefficient of variation (RMS CV) of the average ORSR thickness. Results. Using a standard segmentation approach, 1/23 OCT segmentations was graded generally accurate and 22/23 were failure(s). With the adaptive method 21/23 segmentations were graded generally accurate; 2/23 were local segmentation inaccuracies and none was a failure. The intermethod quality of segmentation was significantly different (P << 0.001). The average ORSR thickness measured on CNV patients (78.0 μm; 95% confidence interval [CI], 72.5-83.4 μm) is significantly larger (P << 0.001) than normal average ORSR layer thickness (51.5 ± 3.3 μm). The RMS CV was 8.1%. Conclusions. We have developed a fully automated 3D method for segmenting the ORSR layer in SD-OCT of patients with CNV from eAMD. Our method can quantify the ORSR layer thickness in the presence of fluid, which has the potential to augment management accuracy and efficiency of anti-VEGF treatment. © 2014 The Association for Research in Vision and Ophthalmology, Inc. Source

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