Four electrode measurement (4EM) systems have been used to measure conductivity in tissue where electrode polarization would cause unacceptable inaccuracy in measurement results and where directional measurement of conductivity is required Less polarization than a two-electrode measurement system where the current is applied by the same electrodes that measures the potential and directional measurement as opposed to a coaxial measurement system that measures bulk conductivity but gives no information about direction. ( 1 , 2 , 3) . The system
the tissue engineered constructs. However, these methods such as histology staining, are destructive and time-consuming and require fixing and cutting the tissue cultures ( 6 ).
Therefore, there is a need for real-time and noninvasive monitoring techniques to evaluate the quality of the tissue engineered constructs before implanting them in the body, without the need to use fluorescents or radioactive labels or destructive methods. This in addition, would reduce the number of animals required for this purpose ( 5 , 6 ).
Martina Sammer, Bob Laarhoven, Ernest Mejias, Doekle Yntema, Elmar C. Fuchs, Gert Holler, Georg Brasseur and Ernst Lankmayr
as a static capacitor. The dielectric properties of biological cells and their different components (cell wall, membranes and cytoplasm) were summarized by Markx and Davey [ 4 ]. Over the last couple of decades a lot of research was done on the impedance of cell suspensions, in which a relationship between capacitance and viable cell number was reported [ 5 , 6 , 7 , 8 ]. Fehrenbach et al. [ 5 ] used online capacitive measurements for biomass estimation of Saccaromyces cerevisiae , Pitchia pastoris and Streptomyces virginiae in suspension culture. In their
Abdul Hamid Ismail, Georg Schlieper, Marian Walter, Jürgen Floege and Steffen Leonhardt
changed if required for clinical reasons. The inclusion criteria were: in- and outpatients ≥ 18 years of age on chronic HD three times a week, who had been on dialysis for a minimum of six months. The exclusion criteria were HIV or hepatitis virus C infection, pregnancy, pacemakers, amputation of a limb, artificial joints, or receiving a blood transfusion within a week before the measurement.
Obtained measurements included the patient’s pre- and post-dialysis weight, height, thigh length and circumferences, systolic and diastolic blood pressure
Ørjan G.Martinsen, Oliver Pabst, Christian Tronstad and Sverre Grimnes
Skin conductance measurements have been used in psychophysiology for more than a century. Measurements of galvanic skin response (GSR) (also referred to by the more general term electrodermal activity (EDA)) have been reported as early as the last part of the nineteenth century (see [ 1 ] for an overview). Through many decades, the method of using direct current (DC) measurements of skin conductance with a constant applied voltage has dominated the EDA literature [ 2 ].
However, there are potential complications with the DC method, such as
The stray capacitance between the human body and earth ground can play a significant role in bioimpedance measurement systems where it may yield, for example, apparent inductive components not associated to any magnetic phenomena [ 1 , 2 ]. It is also an intervening factor in the assessment of human body impedance for risk analysis in case of electric contacts [ 3 ] or electromagnetic radiation [ 4 ] and in electrostatic discharge studies [ 5 ], and has strong influence in power-line interference in biopotential measurements [ 6 , 7 , 8
There are a number of parameters that are used to describe properties of a measurement system which consist of measurement instrumentation and measurand. One of these parameters has been given the name sensitivity, which may be misleading. The word sensitivity can be interpreted in at least two ways for a measurement system. Firstly, it specifies how much the output of a system, for example a transducer, changes as a function of a change in the input. This is the classical engineering point-of-view. When considering a 3D volume impedance system
Electrical impedance spectroscopy is a widely used tool for characterization the structure of tissues and cell cultures [ 1 ]. In the cases where the properties of objects are changing in time (e.g., heart muscle) or the objects are moving as cells in a microfluidic channel, the coverage of the frequency range of interest within a short timeframe demands to satisfy the criteria of the linear time-invariant (LTI) system. If the properties of a sample under test (SUT) are changing significantly during a measurement timeframe, the corresponding
Impedance spectroscopy measurements of electrolytes are frequently difficult to perform due to a thin charged layer (double layer) that forms between the electrode and the media [ 1 , 2 ]. The double layer is a result of charge redistribution close to the electrode that results in a very thin layer of high capacitance disturbing the impedance measurements of the media (particularly at low frequencies). We have investigated the possibility of eliminating the double layer effect by constructing a measurement cell capable of varying the distance