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排序方式: 共有871条查询结果,搜索用时 31 毫秒
1.
Lu W Parikh PJ El Naqa IM Nystrom MM Hubenschmidt JP Wahab SH Mutic S Singh AK Christensen GE Bradley JD Low DA 《Medical physics》2005,32(4):890-901
We have developed a four-dimensional computed tomography (4D CT) technique for mapping breathing motion in radiotherapy treatment planning. A multislice CT scanner (1.5 mm slices) operated in ciné mode was used to acquire 12 contiguous slices in each couch position for 15 consecutive scans (0.5 s rotation, 0.25 s between scans) while the patient underwent simultaneous quantitative spirometry measurements to provide a sorting metric. The spirometry-sorted scans were used to reconstruct a 4D data set. A critical factor for 4D CT is quantifying the reconstructed data set quality which we measure by correlating the metric used relative to internal-object motion. For this study, the internal air content within the lung was used as a surrogate for internal motion measurements. Thresholding and image morphological operations were applied to delineate the air-containing tissues (lungs, trachea) from each CT slice. The Hounsfield values were converted to the internal air content (V). The relationship between the air content and spirometer-measured tidal volume (v) was found to be quite linear throughout the lungs and was used to estimate the overall accuracy and precision of tidal volume-sorted 4D CT. Inspection of the CT-scan air content as a function of tidal volume showed excellent correlations (typically r>0.99) throughout the lung volume. Because of the discovered linear relationship, the ratio of internal air content to tidal volume was indicative of the fraction of air change in each couch position. Theoretically, due to air density differences within the lung and in room, the sum of these ratios would equal 1.11. For 12 patients, the mean value was 1.08 +/- 0.06, indicating the high quality of spirometry-based image sorting. The residual of a first-order fit between v and V was used to estimate the process precision. For all patients, the precision was better than 8%, with a mean value of 5.1% +/- 1.9%. This quantitative analysis highlights the value of using spirometry as the metric in sorting CT scans. The 4D reconstruction provides the CT data required to measure the three-dimensional trajectory of tumor and lung tissue during free breathing. 相似文献
2.
Reduced hippocampal insulin-degrading enzyme in late-onset Alzheimer's disease is associated with the apolipoprotein E-epsilon4 allele 总被引:5,自引:0,他引:5 下载免费PDF全文
Cook DG Leverenz JB McMillan PJ Kulstad JJ Ericksen S Roth RA Schellenberg GD Jin LW Kovacina KS Craft S 《The American journal of pathology》2003,162(1):313-319
Abeta is the major component of amyloid plaques characterizing Alzheimer's disease (AD). Abeta accumulation can be affected by numerous factors including increased rates of production and/or impaired clearance. Insulin-degrading enzyme (IDE) has been implicated as a candidate enzyme responsible for the degradation and clearance of Abeta in the brain. We have previously shown that AD patients exhibit abnormalities in insulin metabolism that are associated with apoliprotein E (APOE) status. The possible association of IDE with AD, as well as the link between APOE status and insulin metabolism, led us to examine the expression of IDE in AD. We report that hippocampal IDE protein is reduced by approximately 50% in epsilon4+ AD patients compared to epsilon4- patients and controls. The allele-specific decrease of IDE in epsilon4+ AD patients is not associated with neuronal loss since neuron-specific enolase levels were comparable between the AD groups, regardless of APOE status. Hippocampal IDE mRNA levels were also reduced in AD patients with the epsilon4 allele compared to AD and normal subjects without the epsilon4 allele. These findings show that reduced IDE expression is associated with a significant risk factor for AD and suggest that IDE may interact with APOE status to affect Abeta metabolism. 相似文献
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Stella R. Milsom Sasha M. Nair Cara M. Ogilvie Joanna M. Stewart Sally N. Merry 《Journal of pediatric and adolescent gynecology》2013,26(3):142-147
ObjectiveTo determine whether adolescents with polycystic ovary syndrome (PCOS) are more depressed than adolescent girls in the community and to examine factors associated with depression.DesignAn observational study comparing clinical and community samples.SettingTwo specialist reproductive endocrine clinics in Auckland, New Zealand.Participants102 girls aged 14-19 presenting for clinical assessment, fulfilling the Rotterdam consensus for PCOS. The comparison group was 1349 girls from a school-based survey of New Zealand youth.InterventionsClinically significant depression was identified by the long and short form Reynolds Adolescent Depression Scale. BMI, androgen levels, oral contraceptive use, objective symptom severity, age, ethnicity, and socioeconomic grouping were recorded.Main Outcome MeasuresClinically significant depression in the PCOS and community samples. Potential determinants of depression.ResultsClinically significant depression in adolescent girls with PCOS was not increased compared with the community sample (OR 1.3; 95%CI 0.7-2.7, P = .42). Within the PCOS cohort, depression was correlated with increased BMI (P = .01) and possibly acne (P = .08).ConclusionsLean adolescent girls with PCOS did not have more clinically significant depression than girls in the community. Within the PCOS cohort, however, there was a clear association between higher depression scores and elevated BMI. There is a potentially important interaction between obesity and depression in PCOS. 相似文献
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Global profiling of Shewanella oneidensis MR-1: expression of hypothetical genes and improved functional annotations 总被引:1,自引:0,他引:1 下载免费PDF全文
Kolker E Picone AF Galperin MY Romine MF Higdon R Makarova KS Kolker N Anderson GA Qiu X Auberry KJ Babnigg G Beliaev AS Edlefsen P Elias DA Gorby YA Holzman T Klappenbach JA Konstantinidis KT Land ML Lipton MS McCue LA Monroe M Pasa-Tolic L Pinchuk G Purvine S Serres MH Tsapin S Zakrajsek BA Zhu W Zhou J Larimer FW Lawrence CE Riley M Collart FR Yates JR Smith RD Giometti CS Nealson KH Fredrickson JK Tiedje JM 《Proceedings of the National Academy of Sciences of the United States of America》2005,102(6):2099-2104
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Kathy Boutis Jocelyn Gravel Stephen B. Freedman William Craig Ken Tang Carol A. DeMatteo Alexander Sasha Dubrovsky Darcy Beer Emma Burns Gurinder Sangha Roger Zemek 《The Journal of emergency medicine》2018,54(6):757-765
Background
The accurate identification of children with a concussion by emergency physicians is important to initiate appropriate anticipatory guidance and management.Objectives
We compared the frequency of persistent concussion symptoms in children who were provided the diagnosis of concussion by an emergency physician versus those who met Berlin/Zurich international criteria for this diagnosis. We also determined the clinical variables independently associated with a physician-diagnosed concussion.Methods
This was a planned secondary analysis of a prospective, multicenter cohort study. Participants were 5–17 years of age and met the Zurich/Berlin International Consensus Statement criteria for concussion.Results
There were 2946 enrolled children. In those with physician-diagnosed concussion vs. no concussion, the frequency of persistent symptoms was 62.5% vs. 38.8% (p < 0.0001) at 1 week, 46.3% vs. 25.8% (p < 0.0001) at 2 weeks, and 33.0% vs. 23.0% (p < 0.0001) at 4 weeks. Of those meeting international criteria, 2340 (79.4%) were diagnosed with a concussion by an emergency physician and 12 variables were associated with this diagnosis. Five had an odds ratio (OR) > 1.5: older age (13–17 vs. 5–7 years, OR 2.9), longer time to presentation (≥16 vs. <16 h, OR 2.1), nausea (OR 1.7), sport mechanism (OR 1.7), and amnesia (OR 1.6).Conclusions
Relative to international criteria, the more selective assignment of concussion by emergency physicians was associated with a greater frequency of persistent concussion symptoms. In addition, while most children meeting international criteria for concussion were also provided this diagnosis for concussion by an emergency physician, the presence of 5 specific variables made this diagnosis more likely. 相似文献9.
Sasha Taleban Nima Toosizadeh Shilpa Junna Todd Golden Sehem Ghazala Rita Wadeea Coco Tirambulo Jane Mohler 《Digestive diseases and sciences》2018,63(12):3272-3280
Background
Colonoscopy is associated with multiple adverse outcomes. With an aging population undergoing colorectal cancer screening, few modalities exist to assess the patient risk prior to colonoscopy. Frailty, the age-related decline in reserve and function across multiple organ systems, predicts poor surgical outcomes, but its role in endoscopy is unclear.Aims
This prospective cohort study assesses the efficacy of frailty in predicting acute colonoscopy outcomes.Methods
Participants aged ≥?50 years undergoing screening colonoscopy at a tertiary care center were recruited over 2 months ending in July 2017. Frailty was assessed using a validated 20-s upper-extremity frailty test, which measures the capacity of muscle performance. Demographic data, American Society of Anesthesiologists (ASA) status, and Charlson comorbidity index (CCI) were evaluated. Procedure-related adverse events and cardiopulmonary changes during and in the immediate post-procedure period were recorded. Adverse events were stratified into minor and major events. Chi-square and ANCOVA models were used in the analysis.Results
Ninety-nine adults (mean age 62.8 years) were enrolled, among which 49 were non-frail and 50 were pre-frail/frail; 50 were female. Overall, 55 participants experienced a total of 87 adverse events. Frailty and ASA status were significantly associated with colonoscopy adverse events (p?=?0.01 and p?=?0.02, respectively). Age and CCI did not predict colonoscopy outcomes.Conclusions
Compared to age and CCI, frailty status better predicts colonoscopy outcomes in older adults. Among adults undergoing colonoscopy, routine frailty screening should be considered for risk stratification. Additional prospective studies evaluating frailty measurements in endoscopy will further clarify its role in forecasting adverse events.10.
Lubomir Tzvetanov Sasha Nikolaeva Ivan Michailov Petar Tivchev 《Ultrastructural pathology》2013,37(3):171-175
This study applied an experimental rat model and ceramic as an artificial matrix to explore the ultrastructural development of new bone production in tibia defects. By X-ray diffraction control or energy-dispersive X-ray analysis the nature of ceramic was verified and routine histology and TEM investigation were used to demonstrate bone - ceramic interaction. The results show that biphasic ceramic can promote bone growth in an osseous defect and is therefore an alternative to autogenous bone matrix. The porousity and bioactivity of the biphasic ceramic enhanced bone formation and provided a scaffold for new lamellar bone invasion. 相似文献