A novel variational model for image registration using Gaussian curvature

Image registration is one important task in many image processing applications. It aims to align two or more images so that useful information can be extracted through comparison, combination or superposition. This is achieved by constructing an optimal trans- formation which ensures that the template image becomes similar to a given reference image. Although many models exist, designing a model capable of modelling large and smooth deformation field continues to pose a challenge. This paper proposes a novel variational model for image registration using the Gaussian curvature as a regulariser. The model is motivated by the surface restoration work in geometric processing [Elsey and Esedoglu, Multiscale Model. Simul., (2009), pp. 1549-1573]. An effective numerical solver is provided for the model using an augmented Lagrangian method. Numerical experiments can show that the new model outperforms three competing models based on, respectively, a linear curvature [Fischer and Modersitzki, J. Math. Imaging Vis., (2003), pp. 81- 85], the mean curvature [Chumchob, Chen and Brito, Multiscale Model. Simul., (2011), pp. 89-128] and the diffeomorphic demon model [Vercauteren at al., NeuroImage, (2009), pp. 61-72] in terms of robustness and accuracy.Comment: 23 pages, 5 figures. Key words: Image registration, Non-parametric image registration, Regularisation, Gaussian curvature, surface mappin

Microbiological Assay of Two Selected Products of Ceftriaxone Powder for Injection from Pharmaceuticals' Market in Sudan

Background: Different techniques have classically been used to evaluate and assure the quality of medicines circulated on the market; one of the commonly uses is chemical analysis. However, some evidence has shown that there are other important indicators (e.g. bioequivalence, relative potency, etc.) that should also be considered when evaluating the quality of pharmaceutical products.Materials and Methods: A microbiological assay was conducted to compare the relative potency of two Ceftriaxone products (with a third one used as standard product) from the market using 3 reference bacteria including Streptococcus pneumoniae, Klebsiella pneumoniae and Staphylococcus aureus. Serial dilutions were made with the corresponding 1, 4, 8, 16 and 32-fold Minimum Inhibitory Concentration (MIC) of Ceftriaxone against the bacteria under investigation.Results: The relative potency of one product compared to the standard product was estimated to be within the acceptable range of bioequivalence (89.6%), while the other product showed unacceptable relative potency (72.3%).Conclusions: The microbiological assay is an effective and simple method for comparing the equivalency of injectable products. A complaint reporting system about quality and effectiveness problems needs to be considered as a priority source of such information to inform decision-makers.Keywords: Microbiological assay, Ceftriaxone, quality assurance, relative potency and genericmedicines

Interchangeability and Comparative Effectiveness between Micronized and Non-micronized Products of Glibenclamide Tablets

Background: During the last few years there was wide debate about the interchangeability and effectiveness between circulated products containing Glibenclamide in the market.Objectives: This study aimed to compare the effectiveness of this product “non-micronized” to the originator’s product of Glibenclamide tablets “of micronized” sulfonylurea.Methods: 12 volunteers received a dose of 5mg of Glibenclamide (from test and standard products) under fasting conditions in two separate sessions using randomized crossover design. Blood glucose level for the volunteers was monitored to avoid the development of hypoglycemia. Plasma samples were collected over 24 hours and analyzed using HPLC.Results: The maximum concentration Cmax for the test and reference products were 2.508 ± 0.104 and 3.526 ± 0.118 (ìg/ml) respectively and the area under the curve AUC0-[ were 3.511 ± 0.153 4.572 ± 0.202 (ìg.h/ml) for these products respectively, with a difference of about 24% between the test and reference products in its AUC.Conclusions: The results indicate that the test product is not bioequivalent to reference product. The difference in formulation between micronized product and non-micronized product of Glibenclamide tablets has impact on clinical outcomes.Key words:sulfonylurea,Blood glucose,hypoglycemia

An improved model for joint segmentation and registration based on linear curvature smoother

Image segmentation and registration are two of the most challenging tasks in medical imaging. They are closely related because both tasks are often required simultaneously. In this article, we present an improved variational model for a joint segmentation and registration based on active contour without edges and the linear curvature model. The proposed model allows large deformation to occur by solving in this way the difficulties other jointly performed segmentation and registration models have in case of encountering multiple objects into an image or their highly dependence on the initialisation or the need for a pre-registration step, which has an impact on the segmentation results. Through different numerical results, we show that the proposed model gives correct registration results when there are different features inside the object to be segmented or features that have clear boundaries but without fine details in which the old model would not be able to cope. </jats:p

Fair Wrapping for Black-box Predictions

We introduce a new family of techniques to post-process ("wrap") a black-box classifier in order to reduce its bias. Our technique builds on the recent analysis of improper loss functions whose optimization can correct any twist in prediction, unfairness being treated as a twist. In the post-processing, we learn a wrapper function which we define as an $\alpha$-tree, which modifies the prediction. We provide two generic boosting algorithms to learn $\alpha$-trees. We show that our modification has appealing properties in terms of composition of $\alpha$-trees, generalization, interpretability, and KL divergence between modified and original predictions. We exemplify the use of our technique in three fairness notions: conditional value-at-risk, equality of opportunity, and statistical parity; and provide experiments on several readily available datasets.Comment: Published in Advances in Neural Information Processing Systems 35 (NeurIPS 2022

CP violating asymmetry in H±→W±h1H^\pm\to W^\pm h_1 decays

The CP violating asymmetry from the decay rates $H^\pm\to W^\pm h_1$ of charged Higgs bosons into the lightest neutral Higgs boson and a $W^\pm$ boson is calculated and discussed in the complex MSSM. The contributions from all complex phases are considered, especially from the top-squark trilinear coupling, which induces a large contribution to the CP asymmetry.Comment: 19 pages, 10 figures, version published in JHE

Semiparametric regression analysis for composite endpoints subject to componentwise censoring

Composite endpoints with censored data are commonly used as study outcomes in clinical trials. For example, progression-free survival is a widely used composite endpoint, with disease progression and death as the two components. Progression-free survival time is often defined as the time from randomization to the earlier occurrence of disease progression or death from any cause. The censoring times of the two components could be different for patients not experiencing the endpoint event. Conventional approaches, such as taking the minimum of the censoring times of the two components as the censoring time for progression-free survival time, may suffer from efficiency loss and could produce biased estimates of the treatment effect. We propose a new likelihood-based approach that decomposes the endpoints and models both the progression-free survival time and the time from disease progression to death. The censoring times for different components are distinguished. The approach makes full use of available information and provides a direct and improved estimate of the treatment effect on progression-free survival time. Simulations demonstrate that the proposed method outperforms several other approaches and is robust against various model misspecifications. An application to a prostate cancer clinical trial is provided