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Variability in EIT Images of Lung Ventilation as a Function of Electrode Planes and Body Positions.

Zhang J, Patterson R - Open Biomed Eng J (2014)

Bottom Line: There was no significant difference (p>0.05) between supine and sitting.The two 8x8 regions show a larger inter individual variability (coefficient of variation, CV, is from 30% to 382%) compared to the entire left, entire right and total lung (CV is from 11% to 51%).The results for the global regions are more consistent.

View Article: PubMed Central - PubMed

Affiliation: Division of Medical Physics, Department of Radiology, University of Kentucky, Lexington, KY 40536, USA.

ABSTRACT
This study is aimed at investigating the variability in resistivity changes in the lung region as a function of air volume, electrode plane and body position. Six normal subjects (33.8 ± 4.7 years, range from 26 to 37 years) were studied using the Sheffield Electrical Impedance Tomography (EIT) portable system. Three transverse planes at the level of second intercostal space, the level of the xiphisternal joint, and midway between upper and lower locations were chosen for measurements. For each plane, sixteen electrodes were uniformly positioned around the thorax. Data were collected with the breath held at end expiration and after inspiring 0.5, 1.0, or 1.5 liters of air from end expiration, with the subject in both the supine and sitting position. The average resistivity change in five regions, two 8x8 pixel local regions in the right lung, entire right, entire left and total lung regions, were calculated. The results show the resistivity change averaged over electrode positions and subject positions was 7-9% per liter of air, with a slightly larger resistivity change of 10 % per liter air in the lower electrode plane. There was no significant difference (p>0.05) between supine and sitting. The two 8x8 regions show a larger inter individual variability (coefficient of variation, CV, is from 30% to 382%) compared to the entire left, entire right and total lung (CV is from 11% to 51%). The results for the global regions are more consistent. The large inter individual variability appears to be a problem for clinical applications of EIT, such as regional ventilation. The variability may be mitigated by choosing appropriate electrode plane, body position and region of interest for the analysis.

No MeSH data available.


An example for the negative resistivity changes in the area 1 and 2. The EIT images were reconstructed using experimentalmeasurements from one subject at different air volumes, 0.5 liter (left) and 1.0 liter (right). The subject was in the supine position and theupper electrode place was used.
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Figure 9: An example for the negative resistivity changes in the area 1 and 2. The EIT images were reconstructed using experimentalmeasurements from one subject at different air volumes, 0.5 liter (left) and 1.0 liter (right). The subject was in the supine position and theupper electrode place was used.

Mentions: Large inter-individual variability (CVs from 10% to 382%) is observed with air volume changes. The local regional measurements in some individuals caused a decrease in resistivity with inspiration. Fig. (9) shows an example for the negative resistivity measurements in the area 1 and 2 in the right lung. When the subjects inhaled, the resitivities in these areas should increase. The negative values may be due to the changes of electrode position. A simulation study using a Finite Difference human thorax model shows that EIT images are very sensitive to the changes of electrode position [13]. Any electrode repositioning during experiments may result in similar artifacts as shown in Fig. (9). During experiment, any movement of the shoulder may move the electrode up or down with the skin movement, especially for the superior electrode plane. During breathing, the chest will expand in anterior-posterior direction more than that in lateral direction, which will cause unequally spaced electrode positions.


Variability in EIT Images of Lung Ventilation as a Function of Electrode Planes and Body Positions.

Zhang J, Patterson R - Open Biomed Eng J (2014)

An example for the negative resistivity changes in the area 1 and 2. The EIT images were reconstructed using experimentalmeasurements from one subject at different air volumes, 0.5 liter (left) and 1.0 liter (right). The subject was in the supine position and theupper electrode place was used.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4126188&req=5

Figure 9: An example for the negative resistivity changes in the area 1 and 2. The EIT images were reconstructed using experimentalmeasurements from one subject at different air volumes, 0.5 liter (left) and 1.0 liter (right). The subject was in the supine position and theupper electrode place was used.
Mentions: Large inter-individual variability (CVs from 10% to 382%) is observed with air volume changes. The local regional measurements in some individuals caused a decrease in resistivity with inspiration. Fig. (9) shows an example for the negative resistivity measurements in the area 1 and 2 in the right lung. When the subjects inhaled, the resitivities in these areas should increase. The negative values may be due to the changes of electrode position. A simulation study using a Finite Difference human thorax model shows that EIT images are very sensitive to the changes of electrode position [13]. Any electrode repositioning during experiments may result in similar artifacts as shown in Fig. (9). During experiment, any movement of the shoulder may move the electrode up or down with the skin movement, especially for the superior electrode plane. During breathing, the chest will expand in anterior-posterior direction more than that in lateral direction, which will cause unequally spaced electrode positions.

Bottom Line: There was no significant difference (p>0.05) between supine and sitting.The two 8x8 regions show a larger inter individual variability (coefficient of variation, CV, is from 30% to 382%) compared to the entire left, entire right and total lung (CV is from 11% to 51%).The results for the global regions are more consistent.

View Article: PubMed Central - PubMed

Affiliation: Division of Medical Physics, Department of Radiology, University of Kentucky, Lexington, KY 40536, USA.

ABSTRACT
This study is aimed at investigating the variability in resistivity changes in the lung region as a function of air volume, electrode plane and body position. Six normal subjects (33.8 ± 4.7 years, range from 26 to 37 years) were studied using the Sheffield Electrical Impedance Tomography (EIT) portable system. Three transverse planes at the level of second intercostal space, the level of the xiphisternal joint, and midway between upper and lower locations were chosen for measurements. For each plane, sixteen electrodes were uniformly positioned around the thorax. Data were collected with the breath held at end expiration and after inspiring 0.5, 1.0, or 1.5 liters of air from end expiration, with the subject in both the supine and sitting position. The average resistivity change in five regions, two 8x8 pixel local regions in the right lung, entire right, entire left and total lung regions, were calculated. The results show the resistivity change averaged over electrode positions and subject positions was 7-9% per liter of air, with a slightly larger resistivity change of 10 % per liter air in the lower electrode plane. There was no significant difference (p>0.05) between supine and sitting. The two 8x8 regions show a larger inter individual variability (coefficient of variation, CV, is from 30% to 382%) compared to the entire left, entire right and total lung (CV is from 11% to 51%). The results for the global regions are more consistent. The large inter individual variability appears to be a problem for clinical applications of EIT, such as regional ventilation. The variability may be mitigated by choosing appropriate electrode plane, body position and region of interest for the analysis.

No MeSH data available.