title: A comparison of techniques to optimize measurement of voltage changes in electrical impedance tomography by minimizing phase shift errors.
abstract: In electrical impedance tomography, errors due to stray capacitance may be reduced by optimization of the reference phase of the demodulator. Two possible methods, maximization of the demodulator output and minimization of reciprocity error have been assessed, applied to each electrode combination individually, or to all combinations as a whole. Using an EIT system with a single impedance measuring circuit and multiplexer to address the 16 electrodes, the methods were tested on resistor-capacitor networks, saline-filled tanks and humans during variation of the saline concentration of a constant fluid volume in the stomach. Optimization of each channel individually gave less error, particularly on humans, and maximization of the output of the demodulator was more robust. This method is, therefore, recommended to optimize systems and reduce systematic errors with similar EIT systems.
authors.affiliation: University College London, Middlesex Hospital, UK.
authors.forename: A J
authors.initials: AJ
authors.lastname: Fitzgerald
authors.forename: D S
authors.initials: DS
authors.lastname: Holder
authors.forename: L
authors.initials: L
authors.lastname: Eadie
authors.forename: C
authors.initials: C
authors.lastname: Hare
authors.forename: R H
authors.initials: RH
authors.lastname: Bayford
mesh_terms: D016477:Artifacts; D017097:Electric Impedance; D004566:Electrodes; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D019047:Phantoms, Imaging; D011786:Quality Control; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013270:Stomach / Q000033:anatomy & histology* / Q000502:physiology*; D014054:Tomography / Q000295:instrumentation* / Q000379:methods*