China
Africa
Explore chapters and articles related to this topic
1
Published in Mara Cercignani, Nicholas G. Dowell, Paul S. Tofts, Quantitative MRI of the Brain: Principles of Physical Measurement, 2018
Many studies set out to compare groups of subjects using the classic double-blind randomised controlled trial design. Typically, a new MR parameter will be evaluated in a particular disease by measuring it in a group of patients and in a group of controls. The controls could be on placebo or another (established) treatment. Other differences between the groups (‘confounding variables’) should be removed as much as possible, hence the need for age and gender matching. The scanning should be carried out at the same time, using interleaved controls, rather than leaving the controls until the end of patient scanning (when a step change in the measurement procedure could produce an artificial group difference). Some patients may be on treatment which alters the MR results. Matching can be improved by dynamic matching, carried out as part of subject recruitment as the study proceeds. Thus, if controls are in short supply, but patients plentiful, then each time a control is recruited, a matched patient is selected from the available patients. In placebo-controlled trials, allocation of a patient to the placebo or treated group can be decided at the time of recruitment, to keep the groups matched at all times. Double-blinding20 is a powerful way of reducing bias in treatment trials. The person giving the treatment, the person making the measurement,21 and the patient are all blinded to whether they are receiving a genuine treatment or a placebo (Table 1.2).
A dimension reduction in neural network using copula matrix
Published in International Journal of General Systems, 2023
Ayyub Sheikhi, Radko Mesiar, Martin Holeňa
In this section, we apply Algorithm 1 in the AIDS Clinical Trial Group (ACTG) 175 study which was a randomized, double-blind, placebo controlled trial involving 2139 HIV positive patients. The data set is included in the R package speff2trial. The goal of the ACTG 175 study is to obtain a covariate effect on time to the onset of AIDS or death in HIV-infected patients. In this experiment, we consider 13 exploratory variables including: age, wtkg, hemo, homo, drugs, karnof, oprior, z30, cd40, cd80, r, cens, arms and the response variable is days. By investigating this data set, we observed that six attributes such as “hemo”, “homo”,…are nominal (falg). For instance, “hemo” stands for hemophilia (0=no, 1=yes). For more information about this data set, we refer to Hammer et al. (1996).
The changing scope of Optometry in New Zealand: historical perspectives, current practice and research advances
Published in Journal of the Royal Society of New Zealand, 2019
Joanna M. Black, Robert J. Jacobs, John R. Phillips, Monica L. Acosta
Paediatric vision studies are an important research theme within SOVS with early studies investigating visual acuity measurement in children (Carkeet et al. 1997) (Garner et al. 1997). Research on paediatric populations has also included the development of new treatments for amblyopia. Amblyopia or ‘lazy eye’ is a neurodevelopmental disorder of vision which effects approximately 3% of children. Traditionally, patching therapy is prescribed, to strengthen the weaker eye by blocking vision to the normally developing eye. A number of studies have been conducted investigating the binocular basis of amblyopia and inter-ocular suppression. These suggest that binocular treatments may give more sustained visual improvements. The binocular treatment of amblyopia using videogames (BRAVO) study was a randomized placebo-controlled double-masked clinical trial led by Auckland that involved multiple international sites. The aim was to assess the effectiveness of a binocular videogame treatment when used at home for children ≥7 years of age and adults. The study result was that both the active and placebo game improved visual acuity following the trial (Gao, Guo, et al. 2018), and that refractive correction shows significant improvements in visual acuity in adults and children (Gao, Anstice, et al. 2018). A Phase II clinical trial of a related binocular therapy – developed by researchers at Auckland – is commencing at Moorfields Eye Hospital in the UK at the time of writing.
Patient-specific flow descriptors and normalised wall index in peripheral artery disease: a preliminary study
Published in Computer Methods in Biomechanics and Biomedical Engineering: Imaging & Visualization, 2018
Jaykrishna Singh, Gerd Brunner, Joel D. Morrisett, Christie M. Ballantyne, Alan B. Lumsden, Dipan J. Shah, Paolo Decuzzi
MRI data were obtained from ELIMIT (Effect of Lipid Modification on Peripheral Artery Disease after Endovascular Intervention Trial; Lumsden et al. 2007; Brunner et al. 2013). ELIMIT was a randomised, double-blind and double placebo-controlled experiment with the goal to assess the efficacy of intensive lipid-modifying therapy (simvastatin, ezetimibe and extended-release niacin) compared to standard therapy (simvastatin). The findings of the ELIMIT study have been reported elsewhere (Brunner et al. 2013). Patients underwent distal SFA MR imaging at baseline (0-months), 12 months and 24 months with a 3.0T system (Signa Excite, GE Healthcare, Milwaukee, Wisconsin) using an unilateral phased array coil with a field of view (FOV) of 8 cm (along z-axis) and 12 cm (in-plane x and y-axes; Pathway Biomedical, Inc.). The geometries were extracted from proton density-weighted (PDW) fast spin-echo scans, as reported previously (Brunner et al. 2013). ELIMIT participants were also imaged using gated (2D PC MRI sequences, at selected locations within the corresponding PDW volumes typically proximal and distally to SFA lesions. Gated 2D-PC was acquired during the same exam with slice thickness = 4 mm, repetition time (TR) = 10.6 ms, echo time (TE) = 4.97 ms, echo train length (ETL) = 1, bandwidth = 244 Hz/pixel, 20 frames per cardiac cycle and velocity encoding (VENC) of 120 cm/s. Serial MRI scans were carefully co-registered across follow-up visits using anatomical landmarks (artery, vein and muscle; Calamante et al. 2003).