Microwave tomography with phaseless data on the calcaneus by means of artificial neural networks.

The aim of this study is to use a multilayer perceptron (MLP) artificial neural network (ANN) for phaseless imaging the human heel (modeled as a bilayer dielectric media: bone and surrounding tissue) and the calcaneus cross-section size and location using a two-dimensional (2D) microwave tomographic array. Computer simulations were performed over 2D dielectric maps inspired by computed tomography (CT) images of human heels for training and testing the MLP. A morphometric analysis was performed to account for the scatterer shape influence on the results. A robustness analysis was also conducted in order to study the MLP performance in noisy conditions. The standard deviations of the relative percentage errors on estimating the dielectric properties of the calcaneus bone were relatively high. Regarding the calcaneus surrounding tissue, the dielectric parameters estimations are better, with relative percentage error standard deviations up to ≈ 15%. The location and size of the calcaneus are always properly estimated with absolute error standard deviations up to ≈ 3 mm. Microwave tomography of the calcaneus using phaseless data. Simulations were inspired in Computed Tomography images from real heels (above). Inverse problem was solved using Multilayer Perceptron Artificial Neural Network (below).

Is there any information on micro-structure in microwave tomography of bone tissue?

In this work, two-dimensional simulations of the microwave dielectric properties of models with ellipses and realistic models of trabecular bone tissue are performed. In these simulations, finite difference time domain methodology has been applied to simulate two-phase structures containing inclusions. The results presented here show that the micro-structure is an important factor in the effective dielectric properties of trabecular bone. We consider the feasibility of using the dielectric behaviour of bone tissue to be an indicator of bone health. The frequency used was 950 MHz. It was found that the dielectric properties can be used as an estimate of the degree of anisotropy of the micro-structure of the trabecular tissue. Conductivity appears to be the most sensitive parameter in this respect. Models with ellipse shaped-inclusions are also tested to study their application to modelling bone tissue. Models with ellipses that had an aspect ratio of a/b=1.5 showed relatively good agreement when compared with realistic models of bone tissue. According to the results presented here, the anisotropy of trabecular bone must be accounted for when measuring its dielectric properties using microwave imaging.

Density expansion for particle-particle correlations in time-dependent physical clusters

We present a theory for the particle-particle correlations in physical clusters for which bonding between particles is determined by a connectivity distance and a permanency time. A generalized Mayer density expansion for the cluster pair correlation function is found, as well as an Ornstein-Zernike like relation. We can rely on this formalism to study clustering in realistic models by applying techniques of liquid state theory.

Characterization and viral safety validation study of a pasteurized therapeutic concentrate of antithrombin III obtained through affinity chromatography.

BACKGROUND AND OBJECTIVE: Antithrombin III (ATIII) concentrates are employed as therapy for congenital or acquired deficiencies. These concentrates are obtained from Cohn's fraction IV1. To improve yields, purity and safety, our group developed a procedure to obtain a pasteurized ATIII concentrate from the supernatant of Cohn's fraction II + III including a highly efficient heparin affinity chromatography purification and pasteurization as a viral inactivation step. DESIGN AND METHODS: Three steps of the manufacturing procedure (Cohn's fraction II + III precipitation, affinity chromatography and pasteurization) were selected to examine their efficacy in inactivating and/or removing the selected viruses. RESULTS: The industrial batches show a purity higher than 99% with approximately 95% native heparin binding ATIII. Only albumin and IgG could be detected at trace levels (0.07% and 0.16% of the total protein present, respectively). The specific activity of the product was approximately 6.65 IU/mg protein. Five viruses were spiked into the manufacturing starting materials and samples were collected at various points to determine the infection level of virus. The study showed a reduction factor (log 10) > or = 11.7 for HIV-1; > or = 8.1 for bovine herpes virus (analyzed as a model for herpes and hepatitis B viruses); > or = 8.1 for bovine diarrhea virus (model for hepatitis C and G) and > or = 6.0 for encephalomyocarditis virus (model for hepatitis A and other non-enveloped viruses). INTERPRETATION AND CONCLUSIONS: No biochemical alterations of the ATIII were detected in the final product. A high viral elimination capacity of the production process was demonstrated. So far, more than 32 million units of ATIII have been transfused in the form of this therapeutic concentrate without any detected seroconversion.

[Evaluation of viral safety of a high-purity human factor VIII concentrate submitted to 2 specific virus inactivation treatments (FANDHI)]. / Estudio de validación de la seguridad viral de un concentrado de factor VIII humano de alta pureza, sometido a dos tratamientos específicos de inactivación viral (FANHDI).

AIM: To perform a validation study of the production process of a human high purity FVIII concentrate, obtained by affinity chromatography and treated with solvent-detergent and 80 degrees C, 72- hour dry heating in the final vial, in order to demonstrate its viral safety. MATERIAL AND METHODS: The ability to inactivate or eliminate viruses was studied in the steps of PEG precipitation, solvent-detergent treatment (6 h 25 degrees C), affinity chromatography and lyophilization plus heating 80 degrees C for 72 h. HIV and models for hepatitis A, B and C, as well as a model for parvovirus B-19 were employed. The experiments were carried out by spiking the samples at each step with 10% of their volume with the highest titer available virus culture. The samples were processed under validated conditions (mimicking the industrial process) and the residual infectivity was determined (as well as p24 antigen and reverse transcriptase for HIV at the solvent-detergent step). RESULTS: No residual infectivity could be detected for enveloped viruses (HIV and models for hepatitis B and C) after the first minutes of solvent-detergent treatment, which lasts 6 hours. Lyophilization followed by heating 80 degrees C for 72 hours caused complete disappearance of infectivity for the models of hepatitis A and C, before 24 hours of a treatment which lasts 72. Furthermore, lyophilization plus heating reduced infectivity for the models of hepatitis B and parvovirus B-19 by 3.4 and 4.1 logs, respectively. The affinity chromatography reduced infectivity by 7.6 logs for the model of hepatitis B and 2 logs for HIV. PEG precipitation also reduced the infectivity by 3.3 logs for the model of hepatitis A and by 1.2 logs for the model of parvovirus B-19. Taking the process as whole, the study showed cumulative reduction values between 5.3 and > 19 logs of the analyzed viruses. 25 million FVIII units have been transfused so far as FANHDI, with no seroconversion detected. Furthermore, no increase in FVIII inhibitor frequency has been described. CONCLUSION: The FVIII concentrate described shows outstanding viral safety characteristics. These data, together with the preliminary clinical experience after one year usage of the product, indicate that FANHDI is a suitable preparation for haemophilia A treatment.