Disruption of extracellular matrix and perineuronal nets modulates extracellular space volume and geometry.

Extracellular matrix (ECM) is a network of macromolecules which has two forms - perineuronal nets (PNNs) and a diffuse ECM (dECM) - both influence brain development, synapse formation, neuroplasticity, CNS injury and progression of neurodegenerative diseases. ECM remodeling can influence extrasynaptic transmission, mediated by diffusion of neuroactive substances in the extracellular space (ECS). In this study we analyzed how disrupted PNNs and dECM influence brain diffusibility.

Blind deconvolution decreases requirements on temporal resolution of DCE-MRI: Application to 2nd generation pharmacokinetic modeling.

Purpose: Dynamic Contrast-Enhanced (DCE) MRI with 2nd generation pharmacokinetic models provides estimates of plasma flow and permeability surface-area product in contrast to the broadly used 1st generation models (e.g. the Tofts models).

Corrigendum to: Assessment of the degree of adherence of medical laboratories to KDIGO 2012 guideline for evaluation and management of CKD in Czechia and Slovakia.

[This corrects the article DOI: 10.11613/BM.2019.

Blind deconvolution estimation of an arterial input function for small animal DCE-MRI.

Purpose: One of the main obstacles for reliable quantitative dynamic contrast-enhanced (DCE) MRI is the need for accurate knowledge of the arterial input function (AIF). This is a special challenge for preclinical small animal applications where it is very difficult to measure the AIF without partial volume and flow artifacts. Furthermore, using advanced pharmacokinetic models (allowing estimation of blood flow and permeability-surface area product in addition to the classical perfusion parameters) poses stricter requirements on the accuracy and precision of AIF estimation.

Distributed capillary adiabatic tissue homogeneity model in parametric multi-channel blind AIF estimation using DCE-MRI.

Purpose: One of the main challenges in quantitative dynamic contrast-enhanced (DCE) MRI is estimation of the arterial input function (AIF). Usually, the signal from a single artery (ignoring contrast dispersion, partial volume effects and flow artifacts) or a population average of such signals (also ignoring variability between patients) is used.

Methods: Multi-channel blind deconvolution is an alternative approach avoiding most of these problems.

Blind deconvolution in dynamic contrast-enhanced MRI and ultrasound.

This paper is focused on quantitative perfusion analysis using MRI and ultrasound. In both MRI and ultrasound, most approaches allow estimation of rate constants (Ktrans, kep for MRI) and indices (AUC, TTP) that are only related to the physiological perfusion parameters of a tissue (e.g.

The precision of DCE-MRI using the tissue homogeneity model with continuous formulation of the perfusion parameters.

The present trend in dynamic contrast-enhanced MRI is to increase the number of estimated perfusion parameters using complex pharmacokinetic models. However, less attention is given to the precision analysis of the parameter estimates. In this paper, the distributed capillary adiabatic tissue homogeneity pharmacokinetic model is extended by the bolus arrival time formulated as a free continuous parameter.

A pragmatic proposal for permissible limits in external quality assessment schemes with a compromise between biological variation and the state of the art.

Permissible limits for internal and external quality assurance are either based on biological variation or on the state of the art (technical feasibility). The former approach has a scientific basis, but, in some cases, leads to limits which are either not achievable under the present technology, or which are not stringent enough. If proficiency testing is mandatory, stringent limits which cannot be fulfilled by the majority of laboratories could lead to juristic consequences.

Estimation of trueness of measurement results obtained in external quality assessment.

Background: We demonstrated that lyophilised EQA/PT control materials, under certain circumstances, provide equal information about bias values as pools of native patient sera, and that in some cases, long-term reliable work with such materials is possible.

Methods: Bias values, estimated from results of routine surveys of EQA SEKK (Czech Republic) programmes for eight basic blood serum analytes using lyophilised control materials, were compared with bias values reached in the CAP (USA) programme where pools of native and lyophilised patient sera were used.

Results: Results for the components Na, K, Mg, Cl, P, urea, glucose, and uric acid were assessed.

Quality of serum creatinine measurement in light of EQA programs.

Background: The aim of our study was to identify the role of External Quality Assessment (EQA) programs in improving the quality of serum creatinine measurement and glomerular filtration rate (GFR) estimation. Comparison of results achieved during EQA with National Kidney Disease Education Program and College of American Pathologists guidelines identified an urgent need for an improvement in measurement quality. We compared actual results for serum creatinine measurement within the Czech Republic EQA with the requirements of EC Directive 98/79.

Trueness verification in European external quality assessment schemes: time to care about the quality of the samples.

An external quality assessment (EQA) survey on 14 fresh-frozen, single-donation sera assigned with reference measurement procedure (RMP) values revealed a mean bias of + 5.2% and + 3.7% for the cholesterol oxidase and the photometric glucose oxidase procedure groups, respectively.

Pilot external quality assessment survey for post-market vigilance of in vitro diagnostic medical devices and investigation of trueness of participants' results.

The Czech External Quality Assessment Scheme organized a survey using 14 fresh-frozen sera targeted for cholesterol and glucose by reference measurement procedures. The objective was to investigate whether it could fulfil a post-market vigilance function for in vitro diagnostic medical devices and assess trueness of participants' results. It revealed a mean bias of +5.

Survey of serum potassium reference measurements.

We compared the quality of reference measurements for serum potassium in four reference laboratories from three different European countries, using a panel of 60 native patients' samples. The reference methods were based on either ion chromatography (one laboratory) or flame atomic emission spectrometry (three laboratories). Performance specifications for serum potassium measurements were defined as a maximum overall coefficient of variation (CV) of 1.

"Ocean-to-Ocean Project": a transcontinental external quality assessment trial in clinical chemistry realized throughout Eurasia.

More than 800 diagnostic laboratories situated throughout the Eur-Asian continent--from the Pacific Coast up to the North Sea littoral--were involved in a common survey of External Quality Assessment (EQA). It consisted of the simultaneous measurement of up to 30 analytes of 'general' clinical chemistry using the same batch of control material. The laboratories were associated in four EQA institutions: SKZL (The Netherlands), OQUASTA (Austria), SEKK (Czech Republic) and BKKSystem (Community of Independent States).

Current stage of standardization of measurements of specific polypeptides and proteins discussed in light of steps needed towards a comprehensive measurement system.

We present a standardization model for the measurement of specific polypeptides and proteins, which is based on an integrated development of all important elements of a reference measurement system. Generally, the model is in line with other current recommendations. However, it puts special emphasis on the definition of the analyte and on the role of reference methods for verification of the standardization process by measurement of patient specimens.

Analytical specifications of reference methods compilation and critical discussion (from the members of the European EQA-Organizers Working Group B).

We present a compilation of published data for accuracy, precision, and measurement design for analytes that, currently, are of major interest for European reference laboratories. These data are compared with recent recommendations for performance of reference methods to be used within networks of European reference laboratories. In addition, we review the literature on reference methods and related topics.

Analytical quality specifications for reference methods and operating specifications for networks of reference laboratories. discussion paper from the members of the external quality assessment (EQA) Working Group B1) on target values in EQAS.

The aim of the Working Group was to describe guidelines for the establishment of networks of reference laboratories. The need for such networks to achieve an accuracy-based uniform measurement system with traceability of results of analytical systems/test-kits to the true value is outlined. Criteria for analytical quality specifications, which are related to the ultimate purpose of the reference method and thereby to the objectives of the networks, are emphasized.

[Direct determination of inorganic phosphor in serum and urine utilizing Rhodamin B (author's transl)].

A micromethod is described for the spectrophotometric determination of inorganic phosphate in serum and urine utilizing Rhodamin B as a dye (phosphomolybdat-Rhodamin B complex), Brij 35, and polyvinylpyrrolidon as catalyst. The procedure does not involve deproteinization and yields a stable complex in 20 min. The linearity is constant up to at least 9 mg Pi per 100 ml.