Kinetic modeling of PET-FDG in the brain without blood sampling

The aim in this work is to report a new method to calculate parametric images from a single scan acquisition with positron emission tomography (PET) and fluorodeoxyglucose (FDG) in the human brain without blood sampling. It is usually practical for research or clinical purposes to inject the patient in an isolated room and to start the PET acquisition only for some 10–20 min, about 30 min after FDG injection. In order to calculate the cerebral metabolic rates for glucose (CMRG), usually several blood samples are required. The proposed method considers the relation between the uptake of the tracer in the cerebellum as a reference tissue and the population based input curve. Similar results were obtained for CMRG values with the present method in comparison to the usual autoradiographic and the non-linear least squares fitting of regions of interest.     

Denervation causes changes in electrophysiological properties in rat phrenic motoneurons

Thirty-nine male adult rats were divided into a control group and a denervation group that had been subjected to phrenicotomy 4 weeks earlier. Electrophysiological membrane properties (input resistance and rheobase) of phrenic motoneurons were measured from intracellular recordings made with glass microelectrodes. Under anesthetized and artificially ventilated conditions, the recorded motoneurons were divided into recruited (spike discharge) and non-recruited (depolarization only) types. There was a significant inverse relationship between the rheobase and input resistance in the control rats, but not in the denervated rats. In the control rats, the mean value of rheobase in the non-recruited motoneurons was significantly higher than that in the recruited motoneurons. In denervated rats, however, the mean value of rheobase in the recruited motoneurons was identical to that in the non-recruited motoneurons. The results indicated that phrenicotomy induced a de-differentiation of electrophysiological properties of the phrenic motoneurons, and that these changes might be restricted to the motoneurons innervating fast-twitch, low fatigue resistance muscle fibers.     

Microelectrode amplifier with improved method of input-capacitance neutralisation

A circuit is described which allows the input capacitance of an f.e.t. input integrated circuit to be used both as the feedback capacitance to neutralise the total input capacitance and to inject current pulses into the input. Compared with the conventional method of adding discrete capacitors to perform these functions, this design results in a lower total capacitance at the input, which reduces the high-frequency noise generated by the amplifier and facilitates the achievement of a low effective capacitance. A modified version having an ultralow (0·1pA) input current, for use with ion-sensitive microelectrodes, is also described.     

Nonlinear and Frequency-Dependent Mechanical Behavior of the Mouse Respiratory System

The assessment of the mechanical properties of the respiratory system is typically done by oscillating flow into the lungs via the trachea, measuring the resulting pressure generated at the trachea, and relating the two signals to each other in terms of some suitable mathematical model. If the perturbing flow signal is broadband and not too large in amplitude, linear behavior is usually assumed and the input impedance calculated. Alternatively, some researchers have used flow signals that are narrow band but large in amplitude, and invoked nonlinear lumped-parameter models to account for the relationship between flow and pressure. There has been little attempt, however, to deal with respiratory data that are both broadband and reflective of system nonlinearities. In the present study, we collected such data from mice. To interpret these data, we first developed a time-domain approximation to a widely used model of respiratory input impedance. We then extended this model to include nonlinear resistive and elastic terms. We found that the nonlinear elastic term fit the data better than the linear model or the nonlinear resistance model when amplitudes were large. This model may be useful for detecting overinflation of the lung during mechanical ventilation. © 2003 Biomedical Engineering Society. PAC2003: 8719Rr, 8719Uv     

ECLIPS: An extended clinical laboratory information processing system

The clinical laboratory is regarded as a component of the medical care system extending from physician to laboratory staff and back to physician. From this concept a computer-based system of laboratory information is derived, emphasizing: (1) total laboratory responsibility for the test and its request, and (2) physician-oriented output reports.     

The impact of the health-care sector on national economies in selected European countries

Policy-makers face pressures to improve lives and safeguard public finances sustainably. In this analysis, we estimate the economic importance of the health-care sector in 19 European national economies.We use input–output tables for the year 2010 and sectoral data to estimate a set of multipliers: simple, total, truncated, type I and type II multipliers for output, income, value-added, employment and import multiplier.The analysis reveals similarities in the economic importance of the health-care sector for the national economies of the observed countries. Results suggest prevailing positive effects on national economies (value-added, employment and household income) when spending on health-care sector products and services increases, especially in comparison to the effects of increases in spending in other sectors. The importance of the health-care sector is connected to countries’ levels of development; the benefits are especially promising in countries with lower levels of gross domestic product (GDP) per capita, where changes in the health-care sector have a larger impact on employment in the national economy than similar changes in more developed countries. The health-care sector therefore can play an important role as an instrument of economic policy.     

Non-invasive assessment of skeletal kinetics using fluorine-18 fluoride positron emission tomography: evaluation of image and population-derived arterial input functions

To measure regional skeletal kinetics using fluorine-18 fluoride positron emission tomography (PET) it is necessary to know the concentration of radioactive tracer being delivered to bone by arterial plasma with relation to time, the arterial input function (IFa). Methods by which IFa can be derived without arterial sampling are attractive because of their relative technical simplicity and the reduction in possible morbidity to the subject. We have compared the use of a scaled population input function (IFp) and a corrected image-derived input function from the aorta (IFi) with an IFa directly measured from a radial artery line in ten normal postmenopausal women. Both of the aforementioned methods rely only on a small number of discrete venous samples. Each subject had a dynamic PET acquisition of the lumbar spine performed after the intravenous injection of 180 MBq ¹⁸F-fluoride. Both the IFp and the IFi were compared with the IFa in terms of the accuracy of determination of six parameters. These were: plasma clearance of fluoride to bone mineral (K _i), unidirectional plasma clearance to total bone tissue (K ₁) and individual rate constants k ₂, k ₃ and k ₄, calculated using non-linear regression with a three-compartment model, and the plasma clearance to bone mineral calculated using the Patlak method (K _pat). For both the IFp and the IFi method the root mean square errors for K _pat and K _i were similar and small (<8.2%). The errors in determining K ₁ and the rate constants k ₂ to k ₄ are larger by either method, but with a small advantage using the IFp method. It is concluded that the use of either non-invasive method for determining the arterial plasma input function is suitable for the measurement of the most important parameters, K _i and K _pat, in these subjects. Received 8 April and in revised form 11 July 1999     

Ionic mechanism of 4-aminopyridine action on leech neuropile glial cells

Extracellular 4-aminopyridine (4-AP), tetraethylammonium chloride (TEA) and quinine depolarized the neuropile glial cell membrane and decreased its input resistance. As 4-AP induced the most pronounced effects, we focused on the action of 4-AP and clarified the ionic mechanisms involved. 4-AP did not only block glial K+ channels, but also induced Na+ and Ca2+ influx via other than voltage-gated channels. The reversal potential of the 4-AP-induced current was -5 mV. Application of 5 mM Ni2+ or 0.1 mM d-tubocurarine reduced the 4-AP-induced depolarization and the associated decrease in input resistance. We therefore suggest that 4-AP mediates neuronal acetylcholine release, apparently by a presynaptic mechanism. Activation of glial nicotinic acetylcholine receptors contributes to the depolarization, the decrease in input resistance, and the 4-AP-induced inward current. Furthermore, the 4-AP-induced depolarization activates additional voltage-sensitive K+ and Cl- channels and 4-AP-induced Ca2+ influx could activate Ca2+-sensitive K+ and Cl- channels. Together these effects compensate and even exceed the 4-AP-mediated reduction in K+ conductance. Therefore, the 4-AP-induced depolarization was paralleled by a decreasing input resistance.     

基于DEA视角的安徽省卫生健康事业投入与产出效率评价

目的 分析安徽省卫生健康事业投入与产出效率,为区域卫生健康事业发展规划提供参考。方法 采用数据包络分析方法对安徽省16个市2011～2017年的卫生投入产出效率进行测算。结果 2011～2017年,皖北年均总体技术效率和纯技术效率（0.976、0.983）均高于皖南（0.937、0.941）、皖中（0.902、0.913）;皖南年均规模技术效率（0.996）高于皖北（0.993）、皖中（0.989）。结论 安徽省卫生健康事业发展模式亟待转变,应继续落实落细分级诊疗,打造结构合理的高素质医疗卫生人才队伍,构建现代化公立医院管理体系。