The Sheffield data collection system

Brown, Brian; Seagar, Andrew

doi:10.1088/0143-0815/8/4a/012

Cited by 385 publications

(208 citation statements)

References 3 publications

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“…Some systems vary the gain for each measurement to compensate for the large dynamic range (i.e. Sheffield Mk I, (Brown and Seagar, 1987)) or explicitly filter measurements (i.e. Hartinger, 2007).…”

Section: Distinguishability Of Current Patternsmentioning

confidence: 99%

Adjacent stimulation and measurement patterns considered harmful

2011

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Abstract. We characterize the ability of electrical impedance tomography (EIT) to distinguish changes in internal conductivity distributions, and analyze it as a function of stimulation and measurement patterns. A distinguishability measure, z, is proposed which is related to the signal to noise ratio of a medium and to the probability of detection of conductivity changes in a region of interest. z is a function of the number of electrodes, the EIT stimulation and measurement protocol, the stimulation amplitude, the measurement noise, and the size and location of the contrasts. Using this measure we analyze various choices of stimulation and measurement patterns under the constraint of medical electrical safety limits (maximum current into the body). Analysis is performed for a planar placement of 16 electrodes for simulated 3D tank and chest shapes, and measurements in a saline tank. Results show that the traditional (and still most common) adjacent stimulation and measurement patterns have by far the poorest performance (by 6.9×). Good results are obtained for trigonometric patterns and for pair drive and measurement patterns separated by over 90 • . Since the possible improvement over adjacent patterns is so large, we present this result as a call to action: adjacent patterns are harmful, and should be abandoned. We recommend using pair drive and measurement patterns separated by one electrode less than 180 • . We describe an approach to modify an adjacent pattern EIT system by adjusting electrode placement.

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Section: Distinguishability Of Current Patternsmentioning

confidence: 99%

Adjacent stimulation and measurement patterns considered harmful

2011

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“…Our methodology of two-dimensional (2D) EIT has been described in detail previously (10,12,17). Electrodes are positioned with equal spacing around the body to be imaged, thus defining a plane through the object.…”

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confidence: 99%

Three-dimensional electrical impedance tomography

Metherall

Barber

Smallwood

et al. 1996

Nature

371

234

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The electrical resistivity of mammalian tissues varies widely (1-5) and is correlated with physiological function (6-8). Electrical impedance tomography (EIT) can be used to probe such variations in vivo, and offers a non-invasive means of imaging the internal conductivity distribution of the human body (9-11). But the computational complexity of EIT has severe practical limitations, and previous work has been restricted to considering image reconstruction as an essentially two-dimensional problem (10,12). This simplification can limit significantly the imaging capabilities of EIT, as the electric currents used to determine the conductivity variations will not in general be confined to a two-dimensional plane (13). A few studies have attempted three-dimensional EIT image reconstruction (14,15), but have not yet succeeded in generating images of a quality suitable for clinical applications. Here we report the development of a three-dimensional EIT system with greatly improved imaging capabilities, which combines our 64-electrode data-collection apparatus (16) with customized matrix inversion techniques. Our results demonstrate the practical potential of EIT for clinical applications, such as lung or brain imaging and diagnostic screening (8).

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“…It is similar to several other impedance imaging devices, notably that devised by Barber and Brown [6].…”

Section: A Electronic Hardwarementioning

confidence: 56%