Error analysis of tissue resistivity measurement.
We identified the error sources in a system for measuring tissue resistivity at eight frequencies from 1 Hz to 1 MHz using the four-terminal method. We expressed the measured resistivity with an analytical formula containing all error terms. We conducted practical error measurements with in-vivo and bench-top experiments. We averaged errors at all frequencies for all measurements. The standard deviations of error of the quantization error of the 8-bit digital oscilloscope with voltage averaging, the nonideality of the circuit, the in-vivo motion artifact and electrical interference combined to yield an error of +/- 1.19%. The dimension error in measuring the syringe tube for measuring the reference saline resistivity added +/- 1.32% error. The estimation of the working probe constant by interpolating a set of probe constants measured in reference saline solutions added +/- 0.48% error. The difference in the current magnitudes used during the probe calibration and that during the tissue resistivity measurement caused +/- 0.14% error. Variation of the electrode spacing, alignment, and electrode surface property due to the insertion of electrodes into the tissue caused +/- 0.61% error. We combined the above errors to yield an overall standard deviation error of the measured tissue resistivity of +/- 1.96%.
Tsai
Jang-Zern
JZ
Department of Electrical and Computer Engineering, University of Wisconsin, MadisonI 53706 USA.
Will
James A
JA
Hubbard-Van Stelle
Scott
S
Cao
Hong
H
Tungjitkusolmun
Supan
S
Choy
Young Bin
YB
Haemmerich
Dieter
D
Vorperian
Vicken R
VR
Webster
John G
JG
D000818:Animals; D016880:Anisotropy; D002138:Calibration; D017097:Electric Impedance; D004562:Electrocardiography / Q000295:instrumentation*; D004566:Electrodes; D004867:Equipment Design; D006321:Heart / Q000502:physiology*; D008955:Models, Cardiovascular; D015233:Models, Statistical; D015203:Reproducibility of Results; D013552:Swine