Testing the robustness of attribution methods for convolutional neural networks in MRI-based Alzheimer's disease classification

Attribution methods are an easy to use tool for investigating and validating machine learning models. Multiple methods have been suggested in the literature and it is not yet clear which method is most suitable for a given task. In this study, we tested the robustness of four attribution methods, namely gradient*input, guided backpropagation, layer-wise relevance propagation and occlusion, for the task of Alzheimer's disease classification. We have repeatedly trained a convolutional neural network (CNN) with identical training settings in order to separate structural MRI data of patients with Alzheimer's disease and healthy controls. Afterwards, we produced attribution maps for each subject in the test data and quantitatively compared them across models and attribution methods. We show that visual comparison is not sufficient and that some widely used attribution methods produce highly inconsistent outcomes

Advances in the development of Astatine-radiolabelling protocols: exploring the metallic character of astatine

International audiencen.

Effect of dog breed and body conformation on vertical ground reaction forces, impulses, and stance times

OBJECTIVES: To assess whether fully normalised vertical ground reaction forces and stance times obtained at a trot depend on dog breed or body conformations. METHODS: Peak vertical forces (PVF), vertical impulses (VI), stance times (ST), and ratio of forelimb impulse to total impulse (RVI) of 54 dogs of seven different breeds were normalised to body weight and body size according to the theory of dynamic similarity, and were tested for differences between breeds. Breeds were Borzoi, Bernese Mountain dog, Great Dane, Labrador Retriever, Landseer, Rhodesian Ridgeback, and Rottweiler. Body length ratio (BLR) and body mass index (BMI) were also compared between breeds. RESULTS: Significant differences between breeds were found for the normalised forelimb PVF, VI and ST, and hindlimb PVF. Looking at individual breeds, it was most evident that Borzois had a lower forelimb VI, and a higher hindlimb PVF than the other breeds. This resulted in Borzois having a lower RVI compared to other dogs, indicating a more caudally located centre of gravity. Only a few differences in gait parameters were found between other dog breeds. The BMI was significantly lower in Borzois than in other breeds, but was otherwise not associated with gait parameters. CLINICAL SIGNIFICANCE: Force plate data of dogs of different breeds are not necessarily comparable, even after full normalisation to body weight and body size. Group comparisons should only be made when the groups consist of breeds with similar body conformation

Correlation of radiographic changes after tibial tuberosity advancement in dogs with cranial cruciate-deficient stifles with functional outcome

OBJECTIVE: To (1) evaluate radiographic changes associated with osteoarthrosis (OA) before and after tibial tuberosity advancement (TTA) and (2) determine if these changes are indicative of limb function as determined by kinetic gait analysis. STUDY DESIGN: Prospective clinical study. ANIMALS: Dogs (n=35) with cranial cruciate ligament (CCL) deficient stifles (38). METHODS: Variables recorded were: complete or partial CCL rupture, meniscal lesions, arthroscopically graded cartilage lesions, complications, and revision surgeries. Radiographic evaluation and kinetic gait analysis (vertical ground reaction forces [GRFs]) were conducted pre- and 4-16 months postoperatively (mean, 5.9 months). Radiographs were evaluated without knowledge of operative findings and functional outcome. A score (0-3) based on new bone production at 11 specific sites was used to grade OA. Soft tissue changes were classified separately as normal or excessive. Preoperative scores were correlated with clinical variables. Postoperative scores and progression of OA scores were correlated with clinical variables and GRFs. RESULTS: OA remained unchanged in 17 joints and progressed in 21 (55%). Dogs with meniscal lesions had higher OA scores preoperatively, but not at follow-up. Dogs with severe cartilage lesions at surgery had more progression of OA. GRFs improved after surgery and were not correlated with any of the radiographic OA scores. CONCLUSION: Progression of OA was greater in the presence of severe cartilage lesions at surgery. OA scores were not correlated with GRFs. CLINICAL RELEVANCE: Progression of OA is generally expected to occur after TTA despite improvement of limb function

A rapid microwave-assisted procedure for easy access to Nx polydentate ligands for potential application in α-RIT

International audienceHeterocycles bearing a hydrazine moiety react with bisaldehydes or bisketones to afford new Nx polydentate ligands suitable for α-radioimmunotherapy. We developed a fast and efficient method using microwave-assisted technology to obtain chelators with variable size and number of coordination centres which were fully characterized. The complexation efficiency with astatine will be assessed

Prediction of the Atomization Energy of Molecules Using Coulomb Matrix and Atomic Composition in a Bayesian Regularized Neural Networks

Exact calculation of electronic properties of molecules is a fundamental step for intelligent and rational compounds and materials design. The intrinsically graph-like and non-vectorial nature of molecular data generates a unique and challenging machine learning problem. In this paper we embrace a learning from scratch approach where the quantum mechanical electronic properties of molecules are predicted directly from the raw molecular geometry, similar to some recent works. But, unlike these previous endeavors, our study suggests a benefit from combining molecular geometry embedded in the Coulomb matrix with the atomic composition of molecules. Using the new combined features in a Bayesian regularized neural networks, our results improve well-known results from the literature on the QM7 dataset from a mean absolute error of 3.51 kcal/mol down to 3.0 kcal/mol.Comment: Under review ICANN 201

In vivo 212Pb/212Bi generator using indium-DTPA-tagged liposomes

International audienceIndium-DTPA-tagged liposomes were studied in the present work as carriers of in vivo 212Pb / 212Bi generator to be used in targeted alpha therapy. The liposomal uptake of 212Pb, into preformed liposomes, was investigated using different lipophilic chelate (DCP, 2,3-dimercapto-1-propanol (BAL), sodium acetate, and A23187), as a function of various parameters (temperature, concentrations of lipids, Pb, DTPA,...) with 212Pb as a tracer. Different formulations of liposomes were tested to evaluate the radiolabeling efficiency. No complexing agent was necessary for the passage of Pb2+ through the membrane. It occurs naturally via a partial permeability of the lipid bilayer which increases with the temperature. A complexing agent (DTPA) appears necessary to concentrate Pb in the internal compartment of the liposomes. Conditions were found (T = 65°C, internal DTPA concentration of 0.025 M, pH 7.4, ...) yielding a high and rapid uptake of 212Pb in liposomes. The protocol established provides a novel method for the efficient entrapment of about 2-3 Pb atoms per liposome with a yield of 75% in conditions relevant for nuclear medicine

Urban Form, Density and Solar Potential

Rapid urbanization in recent years has exerted tremendous pressure on urban development. In the face of the largely unexamined fashion for densification, it is vital that the environmental impact of compaction be researched. This study comprises solar simulation of eighteen generic models; each represents a particular combination of built form and density. This paper examines the relationships between built forms, density and solar potential, with reference to three design criteria i.e. openness at ground level, daylight factor on building façade and PV potential on building envelope. The result shows the different effects of horizontal and vertical randomness on urban solar potential and it also reveals the interrelation between randomness, plot ratio and site coverage, which can provide helpful insights for planning solar cities