In near-infrared (NIR) analysis of plant extracts, excessive background often exists in near-infrared spectra. The detection of active constituents is difficult because of excessive background, and correction of this problem remains difficult. In this work, the orthogonal signal correction (OSC) method was used to correct excessive background. The method was also compared with several classical background correction methods, such as offset correction, multiplicative scatter correction (MSC), standard normal variate (SNV) transformation, de-trending (DT), first derivative, second derivative and wavelet methods. A simulated dataset and a real NIR spectral dataset were used to test the efficiency of different background correction methods. The results showed that OSC is the only effective method for correcting excessive background.
Background correction; Plant extracts; Orthogonal signal correction; Near-infrared spectroscopy
Targeted gene correction employs a site-specific DNA lesion to promote homologous recombination that eliminates mutation in a disease gene of interest. The double-strand break typically used to initiate correction can also result in genomic instability if deleterious repair occurs rather than gene correction, possibly compromising the safety of targeted gene correction. Here we show that single-strand breaks (nicks) and double-strand breaks both promote efficient gene correction. However, breaks promote high levels of inadvertent but heritable genomic alterations both locally and elsewhere in the genome, while nicks are accompanied by essentially no collateral local mutagenesis, and thus provide a safer approach to gene correction. Defining efficacy as the ratio of gene correction to local deletion, nicks initiate gene correction with 70-fold greater efficacy than do double-strand breaks (29.0±6.0% and 0.42±0.03%, respectively). Thus nicks initiate efficient gene correction, with limited local mutagenesis. These results have clear therapeutic implications, and should inform future design of meganucleases for targeted gene correction.
Practitioners are often asking if the treatment successfully improved performance. Many times this question is directed towards the outcome of a single individual. In this article, we develop a method to assess the improvement of a single individual who is administered a test of percent correct at pre-treatment and post-treatment. A Bayesian approach is taken where the number correct is modelled as a binomial random variable and the percent correct is set to a beta prior distribution. The first model assumes percent correct at pre-test is equal to the percent correct at post-test and the posterior predictive distribution is used to evaluate the change in the number correct. We subsequently model the proportions correct at pre-test and post-test as unequal. The second model then assumes independent proportions and the third assumes correlated beta distributions for the two proportions. 95% credible intervals are calculated for the various methods for number of correct at post-test given a particular level at pre-test. An example using data from a cochlear implant clinical trial is presented where clinicians recorded percent correct in a consonant-nucleus-consonant test.
A systematic sequence of prompt and probe trials was used to teach picture names to three severely retarded children. On prompt trials the experimenter presented a picture and said the picture name for the child to imitate; on probe trials the experimenter did not name the picture. A procedure whereby correct responses to prompts and probes were nondifferentially reinforced was compared with procedures whereby correct responses to prompts and probes were differentially reinforced according to separate and independent schedules of primary reinforcement. In Phase 1, correct responses to prompts and probes were reinforced nondifferentially on a fixed ratio (FR) 6 or 8 schedule; in Phase 2, correct responses to prompts were reinforced on the FR schedule and correct responses to probes were reinforced on an FR schedule of the same value; in Phase 3, correct responses to prompts were reinforced on the FR schedule and correct responses to probes were reinforced on a continuous reinforcement (CRF; every correct response reinforced) schedule; in Phase 4, correct responses to prompts were reinforced on a CRF schedule and correct responses to probes were reinforced on the FR schedule; in Phase 5, a reversal to the conditions of Phase 3 was conducted. For all three children, the FR schedule for correct responses to prompts combined with the CRF schedule for correct responses to probes (Phases 3 and 5) generated the highest number of correct responses to probes, the highest accuracy (correct responses relative to correct responses plus errors) on probe trials, and the highest rate of learning to name pictures.
The development of position and stimulus biases often occurs during initial training on matching-to-sample tasks. Furthermore, without intervention, these biases can be maintained via intermittent reinforcement provided by matching-to-sample contingencies. The present study evaluated the effectiveness of a correction procedure designed to eliminate both position and stimulus biases. Following key-peck training, a group of 6 pigeons had extended exposure to matching-to-sample contingencies without a correction procedure, a group of 4 pigeons was briefly exposed to a simultaneous matching-to-sample procedure to assess biases prior to exposure to the correction procedure, and a group of 5 pigeons was exposed directly to the correction procedure. The correction procedure arranged that every time an incorrect match was made, the trial configuration was repeated on the subsequent trial until a correct match was made. Extended exposure to matching-to-sample contingencies without a correction procedure was associated with reduced biases eventually for most subjects, but rapid development of near-perfect accuracy and bias-free performance was observed upon the implementation of the correction procedure regardless of the type of bias. Bias-free performance was maintained following subsequent exposure to a zero-delay MTS procedure.
position bias; stimulus bias; correction procedure; matching-to-sample; pigeons
Several methods have been proposed for motion correction of High Angular Resolution Diffusion Imaging (HARDI) data. There have been few comparisons of these methods, partly due to a lack of quantitative metrics of performance. We compare two motion correction strategies using two figures of merit: displacement introduced by the motion correction and the 95% confidence interval of the cone of uncertainty of voxels with prolate tensors. What follows is a general approach for assessing motion correction of HARDI data that may have broad application for quality assurance and optimization of postprocessing protocols. Our analysis demonstrates two important issues related to motion correction of HARDI data: 1) although neither method we tested was dramatically superior in performance, both were dramatically better than performing no motion correction, and 2) iteration of motion correction can improve the final results. Based on the results demonstrated here, iterative motion correction is strongly recommended for HARDI acquisitions.
Quantitative myocardial PET perfusion imaging requires partial volume corrections.
Patients underwent ECG-gated, rest-dipyridamole, myocardial perfusion PET using Rb-82 decay corrected in Bq/cc for diastolic, systolic, and combined whole cycle ungated images. Diastolic partial volume correction relative to systole was determined from the systolic/diastolic activity ratio, systolic partial volume correction from phantom dimensions comparable to systolic LV wall thicknesses and whole heart cycle partial volume correction for ungated images from fractional systolic-diastolic duration for systolic and diastolic partial volume corrections.
For 264 PET perfusion images from 159 patients (105 rest-stress image pairs, 54 individual rest or stress images), average resting diastolic partial volume correction relative to systole was 1.14 ± 0.04, independent of heart rate and within ±1.8% of stress images (1.16 ± 0.04). Diastolic partial volume corrections combined with those for phantom dimensions comparable to systolic LV wall thickness gave an average whole heart cycle partial volume correction for ungated images of 1.23 for Rb-82 compared to 1.14 if positron range were negligible as for F-18.
Quantitative myocardial PET perfusion imaging requires partial volume correction, herein demonstrated clinically from systolic/diastolic absolute activity ratios combined with phantom data accounting for Rb-82 positron range.
Electronic supplementary material
The online version of this article (doi:10.1007/s12350-010-9327-y) contains supplementary material, which is available to authorized users.
PET-CT imaging; partial volume correction; myocardial perfusion
Increased type I error resulting from multiple statistical comparisons remains a common problem in the scientific literature. This may result in the reporting and promulgation of spurious findings. One approach to this problem is to correct groups of P-values for “family-wide significance” using a Bonferroni correction or the less conservative Bonferroni-Holm correction or to correct for the “false discovery rate” with a Benjamini-Hochberg correction. Although several solutions are available for performing this correction through commercially available software there are no widely available easy to use open source programs to perform these calculations. In this paper we present an open source program written in Python 3.2 that performs calculations for standard Bonferroni, Bonferroni-Holm and Benjamini-Hochberg corrections.
Bonferroni correction; software program; type I error
The inconsistency of k-space trajectories results in Nyquist artifacts in echo-planar imaging (EPI). Traditional techniques often only correct for phase errors along the frequency-encoding direction (1D correction), which may leave significant residual artifacts, particularly for oblique-plane EPI or in the presence of cross-term eddy currents. As compared with 1D correction, two-dimensional (2D) phase correction can be much more effective in suppressing Nyquist artifacts. However, most existing 2D correction methods require reference scans and may not be generally applicable to different imaging protocols. Furthermore, EPI reconstruction with 2D phase correction is susceptible to error amplification due to subject motion. To address these limitations, we report an inherent and general 2D phase correction technique for EPI Nyquist removal. First, a series of images are generated from the original dataset, by cycling through different possible values of phase errors using a 2D reconstruction framework. Second, the image with the lowest artifact level is identified from images generated in the first step using criteria based on background energy in sorted and sigmoid-weighted signals. In this report, we demonstrate the effectiveness of our new method in removing Nyquist ghosts in single-shot, segmented and parallel EPI without acquiring additional reference scans and the subsequent error amplifications.
A large variability in adolescent idiopathic scoliosis (AIS) correction objectives and instrumentation strategies was documented. The hypothesis was that different correction objectives will lead to different instrumentation strategies. The objective of this study was to develop a numerical model to optimize the instrumentation configurations under given correction objectives.
Eleven surgeons from the Spinal Deformity Study Group independently provided their respective correction objectives for the same patient. For each surgeon, 702 surgical configurations were simulated to search for the most favourable one for his particular objectives. The influence of correction objectives on the resulting surgical strategies was then evaluated.
Fusion levels (mean 11.2, SD 2.1), rod shapes, and implant patterns were significantly influenced by correction objectives (p < 0.05). Different surgeon-specified correction objectives produced different instrumentation strategies for the same patient.
Instrumentation configurations can be optimized with respect to a given set of correction objectives.
Scoliosis; Instrumentation; Simulation; Modeling; Optimization; 3-D correction
To propose a method to correct Optical Coherence Tomography (OCT) images of posterior surface of the crystalline lens incorporating its gradient index (GRIN) distribution and explore its possibilities for posterior surface shape reconstruction in comparison to existing methods of correction.
2-D images of 9 human lenses were obtained with a time-domain OCT system. The shape of the posterior lens surface was corrected using the proposed iterative correction method. The parameters defining the GRIN distribution used for the correction were taken from a previous publication. The results of correction were evaluated relative to the nominal surface shape (accessible in vitro) and compared to the performance of two other existing methods (simple division, refraction correction: assuming a homogeneous index). Comparisons were made in terms of posterior surface radius, conic constant, root mean square, peak to valley and lens thickness shifts from the nominal data.
Differences in the retrieved radius and conic constant were not statistically significant across methods. However, GRIN distortion correction with optimal shape GRIN parameters provided more accurate estimates of the posterior lens surface, in terms of RMS and peak values, with errors less than 6μm and 13μm respectively, on average. Thickness was also more accurately estimated with the new method, with a mean discrepancy of 8μm.
The posterior surface of the crystalline lens and lens thickness can be accurately reconstructed from OCT images, with the accuracy improving with an accurate model of the GRIN distribution. The algorithm can be used to improve quantitative knowledge of the crystalline lens from OCT imaging in vivo. Although the improvements over other methods are modest in 2-D, it is expected that 3-D imaging will fully exploit the potential of the technique. The method will also benefit from increasing experimental data of GRIN distribution in the lens of larger populations.
optical coherence tomography; optical distortion correction; gradient index distribution; crystalline lens
Motion-induced artefacts in magnetic resonance spectroscopic imaging are much harder to recognize than in imaging experiments and can therefore lead to erroneous interpretation. A method for prospective motion correction based on an optical tracking system has recently been proposed and has already been successfully applied to single voxel spectroscopy. In this work, the utility of prospective motion correction in combination with retrospective phase correction is evaluated for spectroscopic imaging in the human brain. Retrospective phase correction, based on the interleaved reference scan method, is used to correct for motion-induced frequency shifts and ensure correct phasing of the spectra across the whole spectroscopic imaging slice. It is demonstrated that the presented correction methodology can reduce motion-induced degradation of spectroscopic imaging data.
spectroscopic imaging; SI; prospective motion correction; interleaved reference scan
Dynamic registration uncertainty of a wavefront-guided correction with respect to underlying wavefront error (WFE) inevitably decreases retinal image quality. A partial correction may improve average retinal image quality and visual acuity in the presence of registration uncertainties. The purpose of this paper is to (a) develop an algorithm to optimize wavefront-guided correction that improves visual acuity given registration uncertainty and (b) test the hypothesis that these corrections provide improved visual performance in the presence of these uncertainties as compared to a full-magnitude correction or a correction by Guirao, Cox, and Williams (2002). A stochastic parallel gradient descent (SPGD) algorithm was used to optimize the partial-magnitude correction for three keratoconic eyes based on measured scleral contact lens movement. Given its high correlation with logMAR acuity, the retinal image quality metric log visual Strehl was used as a predictor of visual acuity. Predicted values of visual acuity with the optimized corrections were validated by regressing measured acuity loss against predicted loss. Measured loss was obtained from normal subjects viewing acuity charts that were degraded by the residual aberrations generated by the movement of the full-magnitude correction, the correction by Guirao, and optimized SPGD correction. Partial-magnitude corrections optimized with an SPGD algorithm provide at least one line improvement of average visual acuity over the full magnitude and the correction by Guirao given the registration uncertainty. This study demonstrates that it is possible to improve the average visual acuity by optimizing wavefront-guided correction in the presence of registration uncertainty.
optical design; wavefront-guided correction; stochastic parallel gradient descent; keratoconus; registration uncertainty
The treatment of hyponatraemia is controversial because of the risk of causing central or extrapontine myelinolysis (EPM). Rapid correction with hypertonic saline to a low normal sodium level has its proponents; others feel that slow correction to below normal sodium values is preventative. Most investigators feel that overcorrection should be avoided. It is not known whether the magnitude of serum sodium change is more important than the actual rate of correction. We present three patients with hyponatraemia ranging from 103 to 105 mmol/l who were corrected slowly with normal saline, corrected quickly with hypertonic saline, or rapidly overcorrected with hypertonic saline. All became comatose and died; all had EPM with or without central pontine myelinolysis (CPM). The rate of correction, the solution used, or the magnitude of correction did not seem to protect against demyelination. In a review of 67 reported CPM cases since 1983, no patients documented as having CPM or EPM by radiological studies or necropsy were treated with water restriction only. A group of 27 hyponatraemic patients treated only with water restriction and 35 with diuretic cessation alone did not develop CPM or EPM. This may be a reasonable approach to patients with symptomatic hyponatraemia and normal renal function.
Aim: To evaluate the acceptability, effectivity, and side effects of a monovision spectacle correction designed to reduce accommodation and myopia progression in schoolchildren.
Methods: Dominant eyes of 11 year old children with myopia (−1.00 to −3.00 D mean spherical equivalent) were corrected for distance; fellow eyes were uncorrected or corrected to keep the refractive imbalance ⩽2.00 D. Myopia progression was followed with cycloplegic autorefraction and A-scan ultrasonography measures of vitreous chamber depth (VCD) for up to 30 months. Dynamic retinoscopy was used to assess accommodation while reading.
Results: All children accommodated to read with the distance corrected (dominant) eye. Thus, the near corrected eye experienced myopic defocus at all levels of accommodation. Myopia progression in the near corrected eyes was significantly slower than in the distance corrected eyes (inter-eye difference = 0.36 D/year (95% CI: 0.54 to 0.19, p = 0.0015, n = 13); difference in VCD elongation = 0.13 mm/year (95% CI: 0.18 to 0.08, p = 0.0003, n = 13)). After refitting with conventional spectacles, the resultant anisometropia returned to baseline levels after 9–18 months.
Conclusions: Monovision is not effective in reducing accommodation in juvenile myopia. However, myopia progression was significantly reduced in the near corrected eye, suggesting that sustained myopic defocus slows axial elongation of the human eye.
ametropia; eyeglasses; refraction; accommodation; children
Thirty-one college undergraduates learned to touch abstract stimuli on a computer screen in arbitrarily designated “correct” sequential orders. Four sets of seven stimuli were used; the stimuli were arrayed horizontally on the screen in random sequences. A correct response (i.e., touching first the stimulus designated as first) resulted in that stimulus appearing near the top of the screen in its correct sequential position (left to right), and remaining there until the end of the trial. Incorrect responses (i.e., touching a stimulus out of sequence) terminated the trial. New trials displayed either the same sequence as the one on which an error had occurred (same-order correction procedure), or a new random sequence (new-order correction procedure). Whenever all responses occurred in the correct sequence, the next trial displayed a new random sequence. Each phase ended when five consecutive correct response sequences occurred. Initially, the same-order correction procedure increased control by the position as well as by the shape of the stimuli; also, it produced more errors, more total trials, more trials to mastery, and more individual patterns of reacquisition than were produced by the new-order procedure.
correction procedures; sequential ordering; sequential behavior patterns; human adults
Treatment of radial clubhand has progressed over the years from no treatment to aggressive surgical correction. Various surgical methods of correction have been described; Centralization of the carpus over the distal end of the ulna has become the method of choice. Corrective casting prior to centralization is an easy and effective method of obtaining soft tissue stretching before any definitive procedure is undertaken. Moreover, it helps put the limb in a correct position. The outcome of deformity correction by serial casting / JESS distractor followed by centralization is discussed.
Materials and Methods:
In a prospective study, of 17 cases with 18 radial clubhands of Heikel's Grade III and IV (with average age 11 months (range 20 days – 24 months) with M:F of 2.6:1, were treated by gradual soft tissue stretching using corrective cast (14 cases) and JESS distraction (4 cases), followed by centralization (16 cases) or radialization (2 cases) and tendon transfers.
The average correction attained during the study was 71° of radial deviation and 31° of volar flexion. The average third metacarpal to distal ulna angle in anteroposterior and lateral view at final follow-up was 7° in both views. Angle of movement at elbow showed a small increase from 99° to 101° during the follow-up period. However, the range of movement at fingers showed increase in stiffness during the follow-up. No injury occurred to the distal ulnar epiphysis during the operative intervention. The results at the final follow-up, at the end of 2 years were graded on the basis of the criteria of F.W. Bora, and of Bayne and Klug. Considering the criteria of F.W. Bora, satisfactory result was shown by nine of the 18 hands (50%) while 16 out of 18 hands (89%) showed good or satisfactory result based on deformity criteria of Bayne and Klug.
The management of radial clubhand by gradual corrective cast or JESS distractor followed by centralization and tendon transfers in children is an acceptable method of treatment with consistently satisfactory results, both functional and cosmetic.
Centralization; radial clubhand; radial ray defects; serial casting; JESS
We conducted a national survey of prisons, jails, and community correctional agencies to estimate the prevalence of entry into and accessibility of correctional programs and drug treatment services for adult offenders. Substance abuse education and awareness is the most prevalent form of service provided, being offered in 74% of prisons, 61% of jails, and 53% of community correctional agencies; at the same time, remedial education is the most frequently available correctional program in prisons (89%) and jails (59.5%), whereas sex offender therapy (57.2%) and intensive supervision (41.9%) dominate in community correctional programs. Most substance abuse services provided to offenders are offered through correctional programs such as intensive supervision, day reporting, vocational education, and work release, among others. Although agencies report a high frequency of providing substance abuse services, the prevalence rates are misleading because less than a quarter of the offenders in prisons and jails and less than 10% of those in community correctional agencies have access to these services through correctional agencies; in addition, these are predominantly drug treatment services that offer few clinical services. Given that drug-involved offenders are likely to have dependence rates that are four times greater than those among the general public, the drug treatment services and correctional programs available to offenders do not appear to be appropriate for the needs of this population. The National Criminal Justice Treatment Practices survey provides a better understanding of the distribution of services and programs across prisons, jails, and community correctional agencies and allows researchers and policymakers to understand some of the gaps in services and programs that may negatively affect recidivism reduction efforts.
Drug treatment services for adult offenders; Outpatient therapy; Service integration; Prevalence; Access rates of services
This study compares the provision of HIV testing in a nationally representative sample of correctional agencies and community-based substance abuse treatment programs and identifies the internal organizational-level correlates of HIV testing in both organizations. Data are derived from the CJ-DATS’ National Criminal Justice Treatment Practices Survey (NCJTP). Using an organizational diffusion theoretical framework (Rogers, 2003), the impact of Centralization of Power, Complexity, Formalization, Interconnectedness, Organizational Resources, and Organizational Size on HIV testing was examined in correctional agencies and treatment programs. While there were no significant differences in the provision of HIV testing among correctional agencies (49%) and treatment programs (50%), the internal organizational-level correlates were more predictive of HIV testing in correctional agencies. Specifically, all dimensions, with the exception of Formalization, were related to the provision of HIV testing in correctional agencies. Implications for correctional agencies and community treatment to adopt HIV testing are discussed.
HIV testing; Correctional Agencies; Outpatient Substance Abuse Treatment; Organizational-Level Adoption
To correct eddy-current artifacts in diffusion tensor (DT) images without the need to obtain auxiliary scans for the sole purpose of correction.
Materials and Methods
DT images are susceptible to distortions caused by eddy currents induced by large diffusion gradients. We propose a new postacquisition correction algorithm that does not require any auxiliary reference scans. It also avoids the problematic procedure of cross-correlating images with significantly different contrasts. A linear model is used to describe the dependence of distortion parameters (translation, scaling, and shear) on the diffusion gradients. The model is solved numerically to provide an individual correction for every diffusion-weighted (DW) image.
The assumptions of the linear model were successfully verified in a series of experiments on a silicon oil phantom. The correction obtained for this phantom was compared with correction obtained by a previously published method. The algorithm was then shown to markedly reduce eddy-current distortions in DT images from human subjects.
The proposed algorithm can accurately correct eddy-current artifacts in DT images. Its principal advantages are that only images with comparable signals and contrasts are cross-correlated, and no additional scans are required.
diffusion tensor imaging; fractional anisotrophy; distortions; eddy currents; echo-planar imaging
No population-based data are available regarding the proportion of school-age children who have corrective lenses in the U.S. The objective of this study was to quantify the proportion of children who have corrective lenses (glasses or contact lenses) and to evaluate the association of corrective lenses with age, gender, race/ethnicity, health insurance status, and family income.
Children 6 to 18 years of age were identified in the 1998 Medical Expenditure Panel Survey. National estimates were made of the proportion with corrective lenses. Logistic regression modeling was used to assess factors that were associated with corrective lenses.
Based on the 5,141 children in the 1988 Medical Expenditure Panel Survey, an estimated 25.4% of the 52.6 million children between 6 and 18 years had corrective lenses. Girls had greater odds than boys of having corrective lenses (odds ratio, 1.41; p < 0.001). Insured children, regardless of race/ethnicity, and uninsured nonblack/non-Hispanic children had similar odds of having corrective lenses. Compared with uninsured black or Hispanic children (odds ratio, 1), greater odds of corrective lens use was found among uninsured nonblack/non-Hispanic children (odds ratio, 2.29; p = 0.002) and black or Hispanic children with public (odds ratio, 1.67; p = 0.005) or private health insurance (odds ratio,1.77; p = 0.004). Among families with an income ≥200% of the federal poverty level, the odds of having corrective lenses increased with age (p ≤ 0.04). In contrast, among those families <200% of the federal poverty level, the odds of having corrective lenses at 12 to 14 years was similar to 15- to 18-year olds (p = 0.93).
The use of corrective lenses suggests that correctable visual impairment is the most common treatable chronic condition of childhood. Income, gender, and race/ethnicity, depending on insurance status, are associated with having corrective lenses. The underlying causes and the impacts of these differences must be understood to ensure optimal delivery of eye care.
eyeglasses; health services research; socioeconomic factors; child; adolescent
To evaluate the effectiveness of refractive correction alone for the treatment of untreated anisometropic amblyopia in children 3 to <7 years old.
Prospective, multicenter, noncomparative intervention.
84 children 3 to <7 years old with untreated anisometropic amblyopia ranging from 20/40 to 20/250.
Optimal refractive correction was provided and visual acuity was measured with the new spectacle correction at baseline, and at 5-week intervals until visual acuity stabilized or amblyopia resolved.
Main Outcome Measures:
Maximum improvement in best-corrected visual acuity in the amblyopic eye and proportion of children whose amblyopia resolved (interocular difference of 1 line or less) with refractive correction alone.
Amblyopia improved with optical correction by 2 or more lines in 77% of the patients and resolved in 27%. Improvement took up to 30 weeks for stabilization criteria to be met. After stabilization, additional improvement occurred with spectacles alone in 21 of 34 patients followed in a control group of a subsequent randomized trial, with amblyopia resolving in 6. Treatment outcome was not related to age, but was related to better baseline visual acuity and lesser amounts of anisometropia.
Refractive correction alone improves visual acuity in many cases and results in resolution of amblyopia in at least one third of 3 to <7-year-old children with untreated anisometropic amblyopia. While most cases of resolution occur with moderate (20/40 to 20/100) amblyopia, the average 3-line improvement in visual acuity resulting from treatment with spectacles may lessen the burden of subsequent amblyopia therapy for those with denser levels of amblyopia.
Refractive correction alone improves visual acuity in many cases and results in resolution of amblyopia in at least one third of children 3 to <7 years old with untreated anisometropic amblyopia.
PROPELLER and Turboprop-MRI are characterized by greatly reduced sensitivity to motion, compared to their predecessors, fast spin-echo and gradient and spin-echo, respectively. This is due to the inherent self-navigation and motion correction of PROPELLER-based techniques. However, it is unknown how various acquisition parameters that determine k-space sampling affect the accuracy of motion correction in PROPELLER and Turboprop-MRI. The goal of this work was to evaluate the accuracy of motion correction in both techniques, to identify an optimal rotation correction approach, and determine acquisition strategies for optimal motion correction. It was demonstrated that, blades with multiple lines allow more accurate estimation of motion than blades with fewer lines. Also, it was shown that Turboprop-MRI is less sensitive to motion than PROPELLER. Furthermore, it was demonstrated that the number of blades does not significantly affect motion correction. Finally, clinically appropriate acquisition strategies that optimize motion correction were discussed for PROPELLER and Turboprop-MRI.
This research measures the effectiveness of the practice of correction and republication of invalidated articles in the biomedical literature by analyzing the rate of citation of the flawed and corrected versions of scholarly articles over time. If the practice of correction and republication is effective, then the incidence of citation of flawed versions should diminish over time and increased incidence of citation of the republication should be observed.
This is a bibliometric study using citation analysis and statistical analysis of pairs of flawed and corrected articles in MEDLINE and Web of Science.
The difference between citation levels of flawed originals and corrected republications does not approach statistical significance until eight to twelve years post-republication. Results showed substantial variability among bibliographic sources in their provision of authoritative bibliographic information.
Correction and republication is a marginally effective biblioremediative practice. The data suggest that inappropriate citation behavior may be partly attributable to author ignorance.
The aim of this study was to examine the quality of data collection by studying the validity of collected data. Data were extracted from the clinic charts of two anonymous outpatients by 38 data collectors. A standard for the data to be collected was determined (168 items). The validity was measured by comparing the collected items with the standard; in this way, the percentages of the collected items that were ‘correct’ could be calculated. The percentage ‘correct’ was higher for clinic chart 1 (mean: 83% correct, SD 7%) than for clinic chart 2 (mean: 78% correct, SD 8%). All categories contained incorrectly collected data. These data were divided into missing data, incorrect start-stop dates, and surplus collected data. Almost all start-stop dates would change into ‘correct’ if ‘monthyear’ was considered correct (instead of the standard ‘daymonthyear’). Not all data collectors used specific protocols, and sources other than the written comments were not always checked. This study shows that a high proportion of data was correctly collected. However, the collection of start-stop dates was not optimal, and the collected data included surplus and missing data. Data collectors should be more knowledgeable about HIV disease and trained in the use of difficult protocols, so that they can better recognize what data to collect and how it should be collected. Among physicians, there should be more agreement about what information to record in the charts, to facilitate data extraction for data collectors.
Database; manual data entry; quality of data collection; HIV/AIDS.