Electroimpedance tomograph
First Claim
1. An electroimpedance tomograph comprising:
- a plurality of electrodes configured to be placed on a body;
measuring circuits that process voltage signals recorded by the electrodes; and
a control unit supplying two adjacent electrodes with an alternating current having one or more preset feed frequencies, said control unit receiving voltage signals from electrodes not directly supplied with said alternating current such that said control unit reconstructs the impedance distribution of the body in an electrode plane, wherein said control unit automatically sets one or more current frequencies such that said control unit records a frequency spectrum or a plurality of frequency spectra of a background signal based on voltage signals of electrodes received over a preset period of time, said voltage signals being stored in said control unit as a voltage time series, said control unit transforming said voltage time series into a background frequency spectrum, said control unit searching said background frequency for a feed frequency having a useful signal to background signal ratio that is greater than a threshold value, said useful signal having a useful signal frequency range, said background signal having a background frequency range, said threshold value being based on an overlap of said useful signal frequency range with said background frequency range.
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Accused Products
Abstract
An electroimpedance tomograph including a plurality of electrodes placed on a body, measuring circuits processing voltage signals recorded by the electrodes, and a control unit supplying two electrodes each with an alternating current. The control unit has a preset feed frequency. The control unit processes the processed voltage signals of all other electrodes to reconstruct the impedance distribution of the body in the electrode plane. The control unit provides for an automatic setting of the current feed frequency/frequencies to record a background frequency spectrum by detecting the electrode voltage signals over a preset period of time and record them as a voltage time series and transform them into a frequency spectrum. The control unit searches in the background frequency spectrum for a frequency (different states) or frequencies (different frequencies) that leads to a useful signal to background ratio above a preset threshold value when used as a feed frequency.
18 Citations
18 Claims
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1. An electroimpedance tomograph comprising:
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a plurality of electrodes configured to be placed on a body; measuring circuits that process voltage signals recorded by the electrodes; and a control unit supplying two adjacent electrodes with an alternating current having one or more preset feed frequencies, said control unit receiving voltage signals from electrodes not directly supplied with said alternating current such that said control unit reconstructs the impedance distribution of the body in an electrode plane, wherein said control unit automatically sets one or more current frequencies such that said control unit records a frequency spectrum or a plurality of frequency spectra of a background signal based on voltage signals of electrodes received over a preset period of time, said voltage signals being stored in said control unit as a voltage time series, said control unit transforming said voltage time series into a background frequency spectrum, said control unit searching said background frequency for a feed frequency having a useful signal to background signal ratio that is greater than a threshold value, said useful signal having a useful signal frequency range, said background signal having a background frequency range, said threshold value being based on an overlap of said useful signal frequency range with said background frequency range. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A method of recording an electroimpedance tomographic image, the method comprising:
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providing a plurality of electrodes configured to be placed on a body; providing measuring circuits that process voltage signals recorded by the electrodes; providing a control unit, said control unit supplying two adjacent electrodes with an alternating current that has one or more preset feed frequencies; processing voltage signals of electrodes not directly supplied with the alternating current; reconstructing an impedance distribution of the body in an electrode plane, wherein said control unit automatically sets a current feed frequency/frequencies; recording at least a background frequency spectrum of a frequency spectrum or a plurality of frequency spectra of a background by detecting voltage signals of electrodes over a preset period of time; recording said voltage signals in said control unit as a voltage time series; transforming said voltage time series into a frequency spectrum; selecting at least one feed frequency or feed frequencies based on said background freguency spectrum, said feed freguency or feed freguencies having a useful signal frequency range that has one of no overlap and a minimum overlap with said background frequency spectrum. - View Dependent Claims (8, 9, 10, 11, 12)
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13. An electroimpedance tomograph comprising:
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a plurality of electrodes configured to be placed on a body, said electrodes including sets of two adjacent electrodes and other electrodes; a measuring circuit means for processing voltage signals received by the electrodes; and a control unit supplying said sets of two adjacent electrodes with an alternating current that has at least one of a preset feed frequency and different preset feed frequencies, said control unit reconstructing an impedance distribution of the body based on voltage signals received from said other electrodes, said control unit automatically setting a current feed frequency/frequencies, said control unit recording a frequency spectrum or a plurality of frequency spectra of a background signal by detecting voltage signals of said other electrodes over a preset period of time, said voltage signals being recorded in said control unit as a voltage time series, said control unit transforming said voltage time series into a background frequency spectrum, said control unit searching for a frequency or frequencies that yields/yield a useful signal to background signal ratio above a preset threshold value when used as a feed frequency/frequencies based on said background frequency spectrum, said useful signal having a useful signal frequency range, said background signal having a background signal frequency range, said preset threshold value associated with a maximum overlap of said user signal frequency range with said background signal frequency range. - View Dependent Claims (14, 15, 16, 17, 18)
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Specification