Open Access

Impedance Ratio Method for Urine Conductivity-Invariant Estimation of Bladder Volume

T. Schlebusch
T. Schlebusch
, 
J. Orschulik
J. Orschulik
, 
J. Malmivuo
J. Malmivuo
, 
S. Leonhardt
S. Leonhardt
, 
D. Leonhäuser
D. Leonhäuser
, 
J. Grosse
J. Grosse
, 
M. Kowollik
M. Kowollik
, 
R. Kirschner-Hermanns
R. Kirschner-Hermanns
 and 
M. Walter
M. Walter
   | Sep 09, 2014
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Article Category: Articles
Published Online: Sep 09, 2014
Page range: 48 - 54
Received: Jun 11, 2014
DOI: https://doi.org/10.5617/jeb.895
Keywords
© 2014 T. Schlebusch, J. Orschulik, J. Malmivuo, S. Leonhardt, D. Leonhäuser, J. Grosse, M. Kowollik, R. Kirschner-Hermanns, M. Walter, published by Sciendo
This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 3.0 License.

Fig. 1

Variability of urine conductivity in nine patients: Even in a hospitalized environment, high intra- and inter-individual variations are apparent.
Variability of urine conductivity in nine patients: Even in a hospitalized environment, high intra- and inter-individual variations are apparent.

Fig. 2

Experimental set-up of in-vivo measurement for controlled volume instillation: The EIT belt is placed cranial of the iliac crest and a standard urinary balloon catheter is used for fluid instillation by a 50 ml syringe.
Experimental set-up of in-vivo measurement for controlled volume instillation: The EIT belt is placed cranial of the iliac crest and a standard urinary balloon catheter is used for fluid instillation by a 50 ml syringe.

Fig. 3

Influence of urine conductivity on EIT global impedance: the slope of the impedance-volume-mapping is influenced by urine conductivity.
Influence of urine conductivity on EIT global impedance: the slope of the impedance-volume-mapping is influenced by urine conductivity.

Fig. 4

The Impedance Ratio Method uses three tetrapolar measurements at front (ventral, Uf /If ), side (Us/Is) and back (dorsal, Ub/Ib) positions.
The Impedance Ratio Method uses three tetrapolar measurements at front (ventral, Uf /If ), side (Us/Is) and back (dorsal, Ub/Ib) positions.

Fig. 5

Sensitivity field of the measurement positions showing the spatial difference in sensitivity regions, [1/m4].
Sensitivity field of the measurement positions showing the spatial difference in sensitivity regions, [1/m4].

Fig. 6

Measurement system schematics with Agilent E4980 impedance measurement device, custom built multiplexer and phantom. A PC is used to control injection frequency and selection of current injection and voltage measurement electrodes.
Measurement system schematics with Agilent E4980 impedance measurement device, custom built multiplexer and phantom. A PC is used to control injection frequency and selection of current injection and voltage measurement electrodes.

Fig. 7

In-vitro tank filled with agar as a multi-frequency EIT phantom: A cylindrical cavity is cut into the agar and filled with solutions of different conductivities to model varying urine conductivity. The sketches visualize the spatial arrangement (left) and variation in cavity size (right).
In-vitro tank filled with agar as a multi-frequency EIT phantom: A cylindrical cavity is cut into the agar and filled with solutions of different conductivities to model varying urine conductivity. The sketches visualize the spatial arrangement (left) and variation in cavity size (right).

Fig. 8

In-silico results for single-frequency variant using absolute values: The method is unreliable for urine conductivities in the range of surrounding tissue impedances (4 mS/cm in this case).
In-silico results for single-frequency variant using absolute values: The method is unreliable for urine conductivities in the range of surrounding tissue impedances (4 mS/cm in this case).

Fig. 9

In-silico results for single-frequency variant using imaginary parts: For urine volumes higher than 100 ml the method works as expected.
In-silico results for single-frequency variant using imaginary parts: For urine volumes higher than 100 ml the method works as expected.

Fig. 10

In-silico results for frequency-differential variant using absolute values: Comparable result to the single-frequency variant using imaginary parts.
In-silico results for frequency-differential variant using absolute values: Comparable result to the single-frequency variant using imaginary parts.

Fig. 11

Noise susceptibility of the three methods for given SNR: Due to the smaller amplitude of the impedance differences, the multi-frequency method is much more susceptible to noise than the single frequency method.
Noise susceptibility of the three methods for given SNR: Due to the smaller amplitude of the impedance differences, the multi-frequency method is much more susceptible to noise than the single frequency method.

Fig. 12

In-vitro results for single-frequency variant using absolute values: the influence of urine conductivity is not suppressed completely.
In-vitro results for single-frequency variant using absolute values: the influence of urine conductivity is not suppressed completely.

Fig. 13

In-vitro results for single-frequency variant using imaginary parts: good suppression of urine conductivity variation in the volume estimation result.
In-vitro results for single-frequency variant using imaginary parts: good suppression of urine conductivity variation in the volume estimation result.

Fig. 14

In-vitro results for frequency-differential variant using absolute values: the results from simulation could not be reproduced, probably by an impact of varying electrode contact impedances on the measurement device.
In-vitro results for frequency-differential variant using absolute values: the results from simulation could not be reproduced, probably by an impact of varying electrode contact impedances on the measurement device.
eISSN:
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Language:
English
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Journal Subjects:
Engineering, Bioengineering and Biomedical Engineering, Biomedical Electronics, Life Sciences, Biophysics, Medicine, Biomedical Engineering, Physics, Spectroscopy and Metrology
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