Median Discrepancy Research Articles

Does Ct volumetry accurately predict functional reserve of the future liver remnant after major hepatectomy?

Background: Precise quantitative tests are not available to measure synthetic liver function prior to major hepatectomy. Most centers rely on imperfect surrogates including laboratory studies and CT volumetry. Indocyanine green clearance can quantify functional hepatocyte mass, but does not provide regional assessment and has not been widely adopted in North America. Nuclear medicine tests are rarely used for preoperative planning, but are an additional option to asses overall, hemi-liver, and segmental hepatic function. The purpose of this study was to compare CT volumetry with functional nuclear medicine testing as an accurate measure to predict hepatic function of the future liver remnant. Methods: CT volumetry and functional nuclear medicine data were collected prospectively for patients undergoing evaluation for hepatocellular carcinoma (HCC) from February 2016-May 2018. Paired CT and nuclear medicine scans were obtained within 9 months (median 1 month) of one another. Nuclear medicine scans were performed with freshly prepared technetium 99m labeled mebrofenin (an iminodiacetic analogue), initially dynamic planar images were acquired and thereafter a single-photon emission computed tomography (SPECT) scan was performed. Total and regional liver volumes were calculated and reported by an attending radiologist. Extent of discrepancy between modalities was calculated. Clinical and demographic characteristics including the extent of chronic liver disease were recorded. Results: Over 27 months, 63 patients with HCC underwent both CT and functional nuclear medicine imaging. Median age was 64 years (range 25–85 yrs). Fifty patients (74.6%) were classified as cirrhotic. Of the cirrhotic patients, 60% (n = 30) had Child’s A, 38% Child's B (n = 19) and 2% Child's C cirrhosis (n = 1). Standard CT volumetry overestimated total functional liver volume, TLV, (median 1508 ml; range 570.2–4112.9 ml) when compared with functional nuclear medicine scan (median 1320 ml; range 6.9–3546.1 ml; p = 0.02). Significant discrepancy existed between regional liver volumes and percent contribution to hepatic function. The median volume of the right hemi-liver by CT volumetry was 906 ml (range 187–2324; 61% of TLV) and 721 ml by functional nuclear medicine study (range 12–2050; 65% of TLV; p = 0.03). Less discrepancy was found between left hemi-liver measurements: median volume by CT volumetry was 591 ml (range 100–2236; 38% of TLV) and 512 ml by functional nuclear medicine scan (range 69–2050; 35% of TLV; p = 0.21). Median discrepancy in hemi-liver volumes was 4.8% (range 0.2–51.5%) for the right, and 4.7% (0.2–51.5%) for the left hemi-liver. More than half of the patients (n = 34) had less than 5% discrepancy in hemi-liver volumes, 10 had 5–10% discrepancy, 11 had 10–20% discrepancy. Eight patients (12%) had volume discrepancies greater than 20% between CT volumetry and nuclear medicine imaging. Conclusion: Significant discrepancy exists between standard CT volumetry and nuclear medicine SPECT for estimating functional liver volumes. Compared with functional nuclear medicine imaging, CT volumetry appears to overestimate liver volume. Functional nuclear medicine scans provide additional information and may be a useful and affordable tool for preoperative assessment of the future liver remnant when planning major hepatectomy.

Disease Detection Methodologies in Acute Lymphoblastic Leukemia (ALL): Opportunities for Improvement

Background Minimal residual disease (MRD) is highly prognostic for outcomes in ALL, particularly prior to HCT. New methods for MRD determination in bone marrow (BM) increase the sensitivity of disease detection but remain dependent on the quality of the specimen obtained. Residual disease testing in the cerebrospinal fluid (CSF) is rarely performed. With the dual objectives to identify the role of BM biopsy in conjunction with BM aspirate and flow cytometry (FC), and also the role of CSF FC alongside cytopathology (CP), we evaluated the frequency and degree of discrepancies in disease detection based on methodologies of BM and CSF disease assessments. Design In this retrospective study of children and young adults with relapsed ALL who were enrolled on one or more phase I/II trials at the NCI between 2012 and 2018, we systematically analyzed all BM and CSF assessments that were performed. All CSF analyses included cell count, CP, and frequently FC. BM samples needed to have a biopsy, aspirate, and FC results to be included in the study. BM and CNS status were classified based on established definitions. For BM samples, a discrepancy was defined as any difference in marrow status (M1, M2, or M3). For CSF, a discrepancy was noted if the CP and the FC were discordant. BM specimens were further analyzed by extent of hemodilution and cellularity with MRD threshold set at Results From 98 patients, a total of 410 BM samples were analyzed, amongst which 61 (14.8%) samples had at least one discordant result (Figure 1). This included 26 discrepancies between biopsy and aspirate, 47 between biopsy and FC, and 39 between aspirate and FC. From these, 26 (6.3%) were deemed clinically relevant, defined as changing the assessment from a morphologic remission to more extensive involvement, and had a median discrepancy of 30.5% blasts (range, 7-91%). In 17 of these cases, the biopsy was essential to determine the full extent of disease. In 35 cases, the aspirate was reported as poor quality and in 30% the flow specimen had hemodilution deemed to be clinically significant. 351 of 418 CSF samples had a concurrent FC analysis of which, 32 (9.1%) had disease discrepancies; all cases demonstrated FC positivity with a negative CP report, with the highest discrepancy at 60% blasts (CSF WBC: 2). Conclusion MRD testing in ALL is critical, however, assessing the depth of remission is dependent on the quality of the sample acquired. This retrospective analysis highlights the frequency and degree of discrepancies observed between traditional histopathologic methods of disease assessment and FC. While the incorporation of highly-sensitive MRD testing will increase disease detection, these data support expanding methodologies for complimentary quantitation of BM and CNS involvement in patients with ALL.

SAXSMoW 2.0: Online calculator of the molecular weight of proteins in dilute solution from experimental SAXS data measured on a relative scale.

Knowledge of molecular weight, oligomeric states, and quaternary arrangements of proteins in solution is fundamental for understanding their molecular functions and activities. We describe here a program SAXSMoW 2.0 for robust and quick determination of molecular weight and oligomeric state of proteins in dilute solution, starting from a single experimental small-angle scattering intensity curve, I(q), measured on a relative scale. The first version of this calculator has been widely used during the last decade and applied to analyze experimental SAXS data of many proteins and protein complexes. SAXSMoW 2.0 exhibits new features which allow for the direct input of experimental intensity curves and also automatic modes for quick determinations of the radius of gyration, volume, and molecular weight. The new program was extensively tested by applying it to many experimental SAXS curves downloaded from the open databases, corresponding to proteins with different shapes and molecular weights ranging from ~10 kDa up to about ~500 kDa and different shapes from globular to elongated. These tests reveal that the use of SAXSMoW 2.0 allows for determinations of molecular weights of proteins in dilute solution with a median discrepancy of about 12% for globular proteins. In case of elongated molecules, discrepancy value can be significantly higher. Our tests show discrepancies of approximately 21% for the proteins with molecular shape aspect ratios up to 18.

Completeness and accuracy of self-reported history of blood donation: results from a cohort of older adults in Australia.

The validity of studies relying on self-report of blood donation may be severely threatened by systematic errors. We linked the Sax Institute's 45 and Up Study data, which asked self-report of blood and plasma donation including the date of most recent donation to the blood donor database at the Australian Red Cross Blood Service. We used the linked data to validate the accuracy of self-reported blood donation history including the completeness and accuracy of reported date of most recent donation. Of the total 142,503 participants, 47.8 and 5.1% reported ever donating blood and plasma, respectively. Of those self-reporting blood donation (n = 23,113) and plasma donation (n = 4,451) within the last 10 years of survey, 6262 (27.1%) and 1444 (33.0%) had no record of donation within that period, respectively. Among those who had a record of blood and plasma donation within 10 years before the survey, 97.6 and 93.0% correctly self-reported ever donating blood and plasma, respectively. Donors consistently reported a donation date more recent than the actual recorded date, and the median discrepancy and variability increased as the length of time from the survey date to the actual date of donation increased. Almost 98% of donors donating blood within a decade of survey completion date can correctly self-report their history of donation as ever donating blood, whereas 27% of participants self-reporting donation within a decade may not have actually donated blood. Further, self-reported date of blood donation is not a reliable measure of actual date of donation.

Corrigendum

Journal of Applied EcologyVolume 55, Issue 5 p. 2528-2528 CORRIGENDUMFree Access Corrigendum This article corrects the following: Foxes are now widespread in Tasmania: DNA detection defines the distribution of this rare but invasive carnivore Volume 55Issue 3Journal of Applied Ecology pages: 1564-1564 First Published online: May 15, 2017 Foxes are now widespread in Tasmania: DNA detection defines the distribution of this rare but invasive carnivore Stephen D. Sarre, Anna J. MacDonald, Candida Barclay, Glen R. Saunders, David S. L. Ramsey, Paul Lukacs, Volume 50Issue 2Journal of Applied Ecology pages: 459-468 First Published online: December 4, 2012 Editorial Notice Volume 55Issue 5Journal of Applied Ecology pages: 2527-2527 First Published online: August 12, 2018 First published: 12 August 2018 https://doi.org/10.1111/1365-2664.13245AboutSectionsPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat Sensitivity analysis of the fox habitat suitability model in Sarre et al. (2013) to omission of the Glen Esk (Cleveland) fox carcass. Stephen D. Sarre, Anna J. MacDonald, Candida Barclay, Glen R. Saunders, David S. L. Ramsey We fitted a fox habitat suitability model to the 65 locations of physical evidence of foxes using the maximum likelihood method of Royle, Chandler, Yackulic, and Nichols (2012) using the “maxlike” package in r. All the specific methodological details of the maximum likelihood method, data and predictor variables used in the modelling are given in Sarre, MacDonald, Barclay, Saunders, and Ramsey (2013). The initial model fitted here used the same set of predictor variables as was selected in the final model given in Table 1 of Sarre et al. (2013). We then refitted this model to the dataset but with the Glen Esk fox carcass removed (i.e. n = 64 locations). We then compared the predictions of the original and refitted model by comparing the differences (discrepancy) in the estimated habitat suitability for each of the 1-km2 habitat pixels covering Tasmania (i.e. n = 66,456 cells). The maximum discrepancy (difference) for any pixel in the predictions between the original model and the refitted model with the Glen Esk carcass removed was 0.12. However, the average discrepancy was 0.001 and the median discrepancy was 0. Examination of the cumulative distribution of the discrepancies revealed that 99.9% of the discrepancies were less than 0.043. Given the trivial nature of these discrepancies, the estimate of habitat suitability of foxes from the data with the omitted carcass is essentially unchanged from that given in Sarre et al. (2013). REFERENCES Royle, J. A., Chandler, R. B., Yackulic, C., & Nichols, J. D. (2012). Likelihood analysis of species occurrence probability from presence-only data for modelling species distributions. Methods in Ecology and Evolution, 3, 545– 554. https://doi.org/10.1111/j.2041-210X.2011.00182.x Sarre, S. D., MacDonald, A. J., Barclay, C., Saunders, G. R., & Ramsey, D. S. L. (2013). Foxes are now widespread in Tasmania: DNA detection defines the distribution of this rare but invasive carnivore. Journal of Applied Ecology, 50, 459– 468. https://doi.org/10.1111/1365-2664.12011 Volume55, Issue5September 2018Pages 2528-2528 ReferencesRelatedInformation

Discrepancy between pregnancy dating methods affects obstetric and neonatal outcomes: a population-based register cohort study

To assess associations between discrepancy of pregnancy dating methods and adverse pregnancy, delivery, and neonatal outcomes, odds ratios (ORs) with 95% confidence intervals (CIs) were calculated for discrepancy categories among all singleton births from the Medical Birth Register (1995–2010) with estimated date of delivery (EDD) by last menstrual period (LMP) minus EDD by ultrasound (US) −20 to +20 days. Negative/positive discrepancy was a fetus smaller/larger than expected when dated by US (EDD postponed/changed to an earlier date). Large discrepancy was <10th or >90th percentile. Reference was median discrepancy ±2 days. Odds for diabetes and preeclampsia were higher in pregnancies with negative discrepancy, and for most delivery outcomes in case of large positive discrepancy (+9 to +20 days): shoulder dystocia [OR 1.16 (95% CI 1.01–1.33)] and sphincter injuries [OR 1.13 (95% CI 1.09–1.17)]. Odds for adverse neonatal outcomes were higher in large negative discrepancy (−4 to −20 days): low Apgar score [OR 1.18 (95% CI 1.09–1.27)], asphyxia [OR 1.18 (95% CI 1.11–1.25)], fetal death [OR 1.47 (95% CI 1.32–1.64)], and neonatal death [OR 2.19 (95% CI 1.91–2.50)]. In conclusion, especially, large negative discrepancy was associated with increased risks of adverse perinatal outcomes.

Reliability of sonographic fetal weight estimation in triplet pregnancies: a retrospective cohort study

PurposeTo review our experience in ultrasound fetal weight estimation in our large population of triplet pregnancies.MethodsNinety-seven triplet pregnancies were retrospectively included between January 2003 and January 2017. Sonographic fetal weight estimation using Hadlock’s and Schild’s formulas was compared to actual birth weight in a tertiary-care center in Vienna, Austria. Statistical analyses were performed using a stepwise linear regression model and crosstabs.ResultsThe median discrepancy between the sonographically estimated fetal weight by Hadlock’s formula and the actual birth weight was 106 g (IQR 56–190). The percentage error and its standard deviation were − 2.5 ± 12.1%, and the median percentage error was − 3.6%. Concerning the use of Hadlock’s formula, estimated fetal weight was the most important factor predictive of actual birth weight with an estimate of 0.920 (p < 0.001). Female neonates had been overestimated by a mean of 50.473 g per fetus. The sonographic prediction of small-for-gestational-age neonates was significantly reliable (p < 0.001), with positive and negative predictive values ranging from 81.3 to 100.0%. Similar results were obtained for Schild’s formula.ConclusionEven if sonographically estimated fetal weight in triplet pregnancies has a high overall accuracy of fetal weight estimation, there are some limitations in prediction of intrauterine growth restrictions, especially in female fetuses.

Particle swarm optimization for programming deep brain stimulation arrays

Objective. Deep brain stimulation (DBS) therapy relies on both precise neurosurgical targeting and systematic optimization of stimulation settings to achieve beneficial clinical outcomes. One recent advance to improve targeting is the development of DBS arrays (DBSAs) with electrodes segmented both along and around the DBS lead. However, increasing the number of independent electrodes creates the logistical challenge of optimizing stimulation parameters efficiently. Approach. Solving such complex problems with multiple solutions and objectives is well known to occur in biology, in which complex collective behaviors emerge out of swarms of individual organisms engaged in learning through social interactions. Here, we developed a particle swarm optimization (PSO) algorithm to program DBSAs using a swarm of individual particles representing electrode configurations and stimulation amplitudes. Using a finite element model of motor thalamic DBS, we demonstrate how the PSO algorithm can efficiently optimize a multi-objective function that maximizes predictions of axonal activation in regions of interest (ROI, cerebellar-receiving area of motor thalamus), minimizes predictions of axonal activation in regions of avoidance (ROA, somatosensory thalamus), and minimizes power consumption. Main results. The algorithm solved the multi-objective problem by producing a Pareto front. ROI and ROA activation predictions were consistent across swarms (<1% median discrepancy in axon activation). The algorithm was able to accommodate for (1) lead displacement (1 mm) with relatively small ROI (⩽9.2%) and ROA (⩽1%) activation changes, irrespective of shift direction; (2) reduction in maximum per-electrode current (by 50% and 80%) with ROI activation decreasing by 5.6% and 16%, respectively; and (3) disabling electrodes (n = 3 and 12) with ROI activation reduction by 1.8% and 14%, respectively. Additionally, comparison between PSO predictions and multi-compartment axon model simulations showed discrepancies of <1% between approaches. Significance. The PSO algorithm provides a computationally efficient way to program DBS systems especially those with higher electrode counts.

Binary Auto-Regressive Geometric Modelling in a DNA Context

SummarySymbolic or categorical sequences occur in many contexts and can be characterized, for example, by integer-valued intersymbol distances or binary-valued indicator sequences. The analysis of these numerical sequences often sheds light on the properties of the original symbolic sequences. This work introduces new statistical tools for exploring auto-correlation structure in the indicator sequences, for the specific case of deoxyribonucleic acid (DNA) sequences. It is known that the probability distribution of internucleotide distances of DNA sequences deviates significantly from the distribution obtained by assuming independent random placement (i.e. the geometric distribution) and that the deviations can be used either to discriminate between species or to build phylogenetic trees. To investigate the extent to which auto-correlation structure explains these deviations, the 0–1 indicator sequence of each nucleotide (A, C, G and T) is endowed with a binary auto-regressive (AR) model of optimum order. The corresponding binary AR geometric distribution is derived analytically and compared with the observed internucleotide distance distribution by appropriate goodness-of-fit testing. Results in 34 mitochondrial DNA sequences show that the hypothesis of equal observed/expected frequencies is seldom rejected when a binary AR model is considered instead of independence (76/136 versus 125/136 rejections at the 1% level), in spite of χ2-testing tending to reject for large samples, regardless of how close observed/expected values are. Furthermore, binary AR structure also leads to a median discrepancy reduction of 90% for G, 80% for C, 60% for T and 30% for nucleotide A. Therefore, these models are useful to describe the dependences within a given nucleotide and encourage the development of a model-based framework to compact internucleotide distance information and to understand DNA differences among species further.

GEOMETRIC QUALITY ASSESSMENT OF LIDAR DATA BASED ON SWATH OVERLAP

Abstract. This paper provides guidelines on quantifying the relative horizontal and vertical errors observed between conjugate features in the overlapping regions of lidar data. The quantification of these errors is important because their presence quantifies the geometric quality of the data. A data set can be said to have good geometric quality if measurements of identical features, regardless of their position or orientation, yield identical results. Good geometric quality indicates that the data are produced using sensor models that are working as they are mathematically designed, and data acquisition processes are not introducing any unforeseen distortion in the data. High geometric quality also leads to high geolocation accuracy of the data when the data acquisition process includes coupling the sensor with geopositioning systems. Current specifications (e.g. Heidemann 2014) do not provide adequate means to quantitatively measure these errors, even though they are required to be reported. Current accuracy measurement and reporting practices followed in the industry and as recommended by data specification documents also potentially underestimate the inter-swath errors, including the presence of systematic errors in lidar data. Hence they pose a risk to the user in terms of data acceptance (i.e. a higher potential for Type II error indicating risk of accepting potentially unsuitable data). For example, if the overlap area is too small or if the sampled locations are close to the center of overlap, or if the errors are sampled in flat regions when there are residual pitch errors in the data, the resultant Root Mean Square Differences (RMSD) can still be small. To avoid this, the following are suggested to be used as criteria for defining the inter-swath quality of data: a) Median Discrepancy Angle b) Mean and RMSD of Horizontal Errors using DQM measured on sloping surfaces c) RMSD for sampled locations from flat areas (defined as areas with less than 5 degrees of slope) It is suggested that 4000-5000 points are uniformly sampled in the overlapping regions of the point cloud, and depending on the surface roughness, to measure the discrepancy between swaths. Care must be taken to sample only areas of single return points only. Point-to-Plane distance based data quality measures are determined for each sample point. These measurements are used to determine the above mentioned parameters. This paper details the measurements and analysis of measurements required to determine these metrics, i.e. Discrepancy Angle, Mean and RMSD of errors in flat regions and horizontal errors obtained using measurements extracted from sloping regions (slope greater than 10 degrees). The research is a result of an ad-hoc joint working group of the US Geological Survey and the American Society for Photogrammetry and Remote Sensing (ASPRS) Airborne Lidar Committee.

Contact induced spin relaxation in graphene spin valves with Al2O3 and MgO tunnel barriers

We investigate spin relaxation in graphene by systematically comparing the roles of spin absorption, other contact-induced effects (e.g., fringe fields), and bulk spin relaxation for graphene spin valves with MgO barriers, Al2O3 barriers, and transparent contacts. We obtain effective spin lifetimes by fitting the Hanle spin precession data with two models that include or exclude the effect of spin absorption. Results indicate that additional contact-induced spin relaxation other than spin absorption dominates the contact effect. For tunneling contacts, we find reasonable agreement between the two models with median discrepancy of ∼20% for MgO and ∼10% for Al2O3.

Hepatic reaction dose for parenchymal changes on Gd-EOB-DTPA-enhanced magnetic resonance images after stereotactic body radiation therapy for hepatocellular carcinoma.

The present study evaluated the threshold dose for hepatic parenchymal changes on gadolinium ethoxybenzyl diethylenetriaminepentaacetic acid (Gd-EOB-DTPA)-enhanced magnetic resonance (MR) images after stereotactic body radiation therapy (SBRT) for hepatocellular carcinoma (HCC). Twenty patients with available data of follow-up MR images acquired 2-4 months after completion of SBRT were selected among the registered patients. SBRT was performed using multiple coplanar and non-coplanar beams with energies of 6 or 15 MV. All patients were treated with doses of 45 Gy administered in three fractions over 3 consecutive days. For image registration between planning computed tomography (CT) and MR images, landmark-based rigid body registration was performed using MIM software. Seventeen patients were included in the analysis. The median discrepancies between planning CT and MR images in the left-right, anterior-posterior and superior-inferior directions were 1.38 mm, 1.24 mm and 1.72 mm, respectively. The median D50 value for the defect in the hepatobiliary phase of Gd-EOB-DTPA-enhanced MR images after SBRT was 19.8 Gy (range, 14.2-28.7 Gy), with R(2) values ranging from 0.76 to 0.99. The threshold dose for parenchymal changes in the hepatobiliary phase of Gd-EOB-DTPA-enhanced MR images performed 2-4 months after 45 Gy of SBRT in three fractions was approximately 20 Gy. Our results provide the basis for further research on the functional loss of liver parenchyma after SBRT.

Calculation of Organ Doses for a Large Number of Patients Undergoing CT Examinations

The objective of our study was to develop an automated calculation method to provide organ dose assessment for a large cohort of pediatric and adult patients undergoing CT examinations. We adopted two dose libraries that were previously published: the volume CT dose index-normalized organ dose library and the tube current-exposure time product (100 mAs)-normalized weighted CT dose index library. We developed an algorithm to calculate organ doses using the two dose libraries and the CT parameters available from DICOM data. We calculated organ doses for pediatric (n = 2499) and adult (n = 2043) CT examinations randomly selected from four health care systems in the United States and compared the adult organ doses with the values calculated from the ImPACT calculator. The median brain dose was 20 mGy (pediatric) and 24 mGy (adult), and the brain dose was greater than 40 mGy for 11% (pediatric) and 18% (adult) of the head CT studies. Both the National Cancer Institute (NCI) and ImPACT methods provided similar organ doses (median discrepancy < 20%) for all organs except the organs located close to the scanning boundaries. The visual comparisons of scanning coverage and phantom anatomies revealed that the NCI method, which is based on realistic computational phantoms, provides more accurate organ doses than the ImPACT method. The automated organ dose calculation method developed in this study reduces the time needed to calculate doses for a large number of patients. We have successfully used this method for a variety of CT-related studies including retrospective epidemiologic studies and CT dose trend analysis studies.

Inverse procedure for high‐latitude ionospheric electrodynamics: Analysis of satellite‐borne magnetometer data

AbstractThis paper presents an analysis of data from the magnetometers on board the Defense Meteorological Satellite Program (DMSP) F‐15, F‐16, F‐17, and F‐18 satellites and the Iridium satellite constellation, using an inverse procedure for high‐latitude ionospheric electrodynamics, during the period of 29–30 May 2010. The Iridium magnetometer data are made available through the Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE) program. The method presented here is built upon the assimilative mapping of ionospheric electrodynamics procedure but with a more complete treatment of the prior model uncertainty to facilitate an optimal inference of complete polar maps of electrodynamic variables from irregularly distributed observational data. The procedure can provide an objective measure of uncertainty associated with the analysis. The cross‐validation analysis, in which the DMSP data are used as independent validation data sets, suggests that the procedure yields the spatial prediction of DMSP perturbation magnetic fields from AMPERE data alone with a median discrepancy of 30–50 nT. Discrepancies larger than 100 nT are seen in about 20% of total samples, whose location and magnitude are generally consistent with the previously identified discrepancy between DMSP and AMPERE data sets. Resulting field‐aligned current (FAC) patterns exhibit more distinct spatial patterns without spurious high‐frequency oscillatory features in comparison to the FAC products provided by AMPERE. Maps of the toroidal magnetic potential and FAC estimated from both AMPERE and DMSP data under four distinctive interplanetary magnetic field (IMF) conditions during a magnetic cloud event demonstrate the IMF control of high‐latitude electrodynamics and the opportunity for future scientific investigation.

Sleep-wake time perception varies by direct or indirect query.

The diagnosis of insomnia rests on self-report of difficulty initiating or maintaining sleep. However, subjective reports may be unreliable, and possibly may vary by the method of inquiry. We investigated this possibility by comparing within-individual response to direct versus indirect time queries after overnight polysomnography. We obtained self-reported sleep-wake times via morning questionnaires in 879 consecutive adult diagnostic polysomnograms. Responses were compared within subjects (direct versus indirect query) and across groups defined by apnea-hypopnea index and by self-reported insomnia symptoms in pre-sleep questionnaires. Direct queries required a time duration response, while indirect queries required clock times from which we calculated time durations. Direct and indirect queries of sleep latency were the same in only 41% of cases, and total sleep time queries matched in only 5.4%. For both latency and total sleep, the most common discrepancy involved the indirect value being larger than the direct response. The discrepancy between direct and indirect queries was not related to objective sleep metrics. The degree of discrepancy was not related to the presence of insomnia symptoms, although patients reporting insomnia symptoms showed underestimation of total sleep duration by direct response. Self-reported sleep latency and total sleep time are often internally inconsistent when comparing direct and indirect survey queries of each measure. These discrepancies represent substantive challenges to effective clinical practice, particularly when diagnosis and management depends on self-reported sleep patterns, as with insomnia. Although self-reported sleep-wake times remains fundamental to clinical practice, objective measures provide clinically relevant adjunctive information.

Abstract T P197: Variation in Last Known Normal Times of Stroke Code Patients

Introduction: Given the time-sensitivity of thrombolytic therapy, the accurate documentation of the patient’s last known normal (LKN) time is crucial to ensure safe and effective management of stroke patients. There exist no studies comparing first recorded LKN times to final verified LKN times. This study investigates whether a difference exists, and the potential impact on treatment and emergent management of acute stroke. Methods: All stroke code patients evaluated at UCSD hospitals (4/2008-7/2013) with 90 day mRS scores available were included. Electronic chart review was performed to obtain first recorded LKN time. Onset to arrival (OTA) intervals were calculated using both the first recorded LKN and official LKN times. Patients were split into three groups based on the disparity between the OTA intervals. Group A: longer OTA interval using first LKN, Group B: two intervals equal, and Group C: shorter OTA interval using first LKN. These groups were compared by baseline characteristics, rates of tPA administration, 90 day mRS score, and rates of symptomatic ICH. Results: Of 226 patients included, 74.3% had disparity between first and official LKN time; 16.8% in Group A and 57.5% in Group C. The median discrepancy between the times was 30 minutes for Group A and 45 minutes for Group C. Baseline characteristics were not significantly different between groups. In stroke/TIA patients, rates of tPA administration were significantly different (A: 65.4%, B: 39.5%, C: 34.8, p=0.022). In Group A, 62.5% had 90 day mRS of 0-1, versus 50% of Group B and 34.4% of Group C, without significant difference. There were no symptomatic ICHs in Group A, compared to 1 (5.6%) in Group B and 3 (9.1%) in Group C. Conclusions: There was a significant proportion of patients with disparity between the first and official recorded LKN times, with the majority falling into Group C (shorter OTA interval using first LKN). If this first recorded time were used to make treatment decisions, as may be the case at community hospitals without stroke neurologists, patients may be frequently treated outside of the recommended window, with a higher risk of adverse safety outcomes. This study highlights the need for accurate determination of last known normal time in order to make the proper treatment decisions.

Multidetector-Row Computed Tomography Allows Accurate Measurement of Mechanical Prosthetic Heart Valve Leaflet Closing Angles Compared With Fluoroscopy

The purpose of this study was to compare multidetector-row computed tomography (MDCT) leaflet restriction measurements with fluoroscopy measurements in commonly used mechanical prosthetic heart valves (PHVs). Four mechanical PHVs (ON-X, Carbomedics, St. Jude, and Medtronic Hall) were imaged in a pulsatile model using fluoroscopy and 64-detector-row computed tomography. Five image acquisitions of each PHV without (1) and with (4) restricted leaflet closure were made. Three observers measured closure angles on fluoroscopy and MDCT. Data were analyzed using intraclass correlation coefficient (ICC) and Bland-Altman plots. Interobserver agreement was high in restricted and non-restricted leaflets on both modalities (ICCs >0.995). MDCT and fluoroscopy showed high agreements (ICCs >0.989). Median MDCT closure angle measurements differed at most -2 to +2 degrees from fluoroscopy in the restricted and -1 to +2 degrees in the non-restricted leaflets. MDCT allows measurement of leaflet motion with a maximal median discrepancy of 2 degrees. Both MDCT and fluoroscopy detect restricted leaflet closure with great accuracy.

Abstract 92: Documentation Discrepancies of Time-Dependent Critical Events in Out of Hospital Cardiac Arrest

Background: The timing of and interval between prehospital interventions and patient-related events during out of-hospital cardiac arrest (OHCA) resuscitation are important for system design and patient outcome. Since most prehospital research relies on data abstraction from the medical record, it is imperative to assure the accuracy and precision of time-stamped events in prehospital documentation. Austere environments and/or limited human resources may impair the accuracy and precision of this documentation. OHCA is a time-sensitive disease that necessitates rapid interventions; even small errors in timing documentation may introduce unrecognized bias into analysis. Objective: Determine the accuracy and precision of EMS documentation of time-stamped events during OHCA. Hypothesis: Times of critical events (CE) in OHCA documented by EMS are inaccurate when compared to audio documentation of the same cases. Methods: We reviewed prehospital documentation of OHCA resuscitation from two regional EMS agencies. We abstracted the documented times of CE in the prehospital medical record, as well as synchronized, time-stamped audio recordings from the monitor/defibrillator corresponding to each case. CE included IV/IO access, first epinephrine administration, successful airway placement, and return of spontaneous circulation. We compared the difference in minutes between medical record and audio sources, rounding down to the whole minute. Results: A total of 411 patients suffered OOHCA during the study period. Of these, 192 patients had both documentation times and audio times for at least one CE. A total of 422 CEs were documented. A median absolute difference of 2 minutes (IQR 1-4 minutes) was found for all CE. 136 (32.8%) of the cardiac arrest cases had 2 or more CE documented. There was a median discrepancy of 4.5 minutes (Range 0-27, IQR 1-4.5) in the interval between CE in the same case. Within case error shows that the differences are random, and not simply related to synchronization of timing devices. Conclusion: Documentation may introduce an error of 2 minutes in the times of CE and 4.5 minutes in the estimated intervals between CE. These errors are meaningful for studies of time dependent diseases like OHCA.

The stellar masses of ∼ 40 000 UV selected Galaxies from the WiggleZ survey at 0.3

We characterise the stellar masses and star formation rates in a sample of almost 40000 spectroscopically confirmed UV luminous galaxies at 0.3<z<1.0 selected from within the WiggleZ Dark Energy Survey. In particular, we match this UV bright population to wide-field infrared surveys such as the near infrared UKIDSS LAS and the mid infrared WISE All-Sky Survey. We find that ~30% of the UV luminous WiggleZ galaxies are detected at >5sigma in the UKIDSS-LAS at all redshifts. An even more luminous subset of 15% are also detected in the WISE 3.4 and 4.6um bands. We compute stellar masses for this very large sample of extremely blue galaxies and quantify the sensitivity of the stellar mass estimates to various assumptions made during the SED fitting. The median stellar masses are log10(M*/M0)=9.6\pm0.7, 10.2\pm0.5 and 10.4\pm0.4 for the IR-undetected, UKIDSS detected and UKIDSS+WISE detected galaxies respectively. We demonstrate that the inclusion of NIR photometry can lead to tighter constraints on the stellar masses. The mass estimates are found to be most sensitive to the inclusion of secondary bursts of star formation as well as changes in the stellar population synthesis models, both of which can lead to median discrepancies of the order of 0.3dex in the stellar masses. We find that the best-fit M/LK is significantly lower (by ~0.4 dex) than that predicted by simple optical colour based estimators, in particular for the bluer galaxies with younger best-fit ages. The WiggleZ galaxies have star formation rates of 3-10 M0/yr and mostly lie at the upper end of the main sequence of star-forming galaxies at these redshifts. Their rest-frame UV luminosities and stellar masses are comparable to both local compact UV-luminous galaxies as well as Lyman break galaxies at z~2-3.(abridged)

Sample size in orthodontic randomized controlled trials: are numbers justified?

Sample size calculations are advocated by the Consolidated Standards of Reporting Trials (CONSORT) group to justify sample sizes in randomized controlled trials (RCTs). This study aimed to analyse the reporting of sample size calculations in trials published as RCTs in orthodontic speciality journals. The performance of sample size calculations was assessed and calculations verified where possible. Related aspects, including number of authors; parallel, split-mouth, or other design; single- or multi-centre study; region of publication; type of data analysis (intention-to-treat or per-protocol basis); and number of participants recruited and lost to follow-up, were considered. Of 139 RCTs identified, complete sample size calculations were reported in 41 studies (29.5 per cent). Parallel designs were typically adopted (n = 113; 81 per cent), with 80 per cent (n = 111) involving two arms and 16 per cent having three arms. Data analysis was conducted on an intention-to-treat (ITT) basis in a small minority of studies (n = 18; 13 per cent). According to the calculations presented, overall, a median of 46 participants were required to demonstrate sufficient power to highlight meaningful differences (typically at a power of 80 per cent). The median number of participants recruited was 60, with a median of 4 participants being lost to follow-up. Our finding indicates good agreement between projected numbers required and those verified (median discrepancy: 5.3 per cent), although only a minority of trials (29.5 per cent) could be examined. Although sample size calculations are often reported in trials published as RCTs in orthodontic speciality journals, presentation is suboptimal and in need of significant improvement.