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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.


MR images showing the tissue/organ movements during lung ventilation.
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Figure 10: MR images showing the tissue/organ movements during lung ventilation.

Mentions: Earlier studies [14-16] show the linear relationship between average resistivity change and air volume. As shown in Figs. (4-6), the non-linear behavior is seen from the end of expiration to 0.5 liter. This non-linear relationship may be caused in part by chest expansion. With inspiration from end expiration to 0.5, 1.0, or 1.5 liters, the anterior-posterior depth of the thorax increases 3.5%, 4.8%, and 5.2% while the lateral width decreases 1.7%, 2.5% and 3.1%, respectively (Fig. 10). The biggest change of the thoracic size occurs from end expiration to 0.5 liter, compared to those changes from 0.5 to 1.0 liter and from 1.0 to 1.5 liters. Adler et al. (1996) [17] studies show the chest expansion may cause 20% error in the center of EIT images. The averaged resistivity changes in the lung region caused by chest expansion were between 0.65 and 18.31% (Zhang and Patterson 2005) [18]. The influences of the expansion in the local regions such as area 1 and 2, which are away from the center of EIT image, are relatively small. This may be why the relationship for area 1 and 2 is more linear.


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)

MR images showing the tissue/organ movements during lung ventilation.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 10: MR images showing the tissue/organ movements during lung ventilation.
Mentions: Earlier studies [14-16] show the linear relationship between average resistivity change and air volume. As shown in Figs. (4-6), the non-linear behavior is seen from the end of expiration to 0.5 liter. This non-linear relationship may be caused in part by chest expansion. With inspiration from end expiration to 0.5, 1.0, or 1.5 liters, the anterior-posterior depth of the thorax increases 3.5%, 4.8%, and 5.2% while the lateral width decreases 1.7%, 2.5% and 3.1%, respectively (Fig. 10). The biggest change of the thoracic size occurs from end expiration to 0.5 liter, compared to those changes from 0.5 to 1.0 liter and from 1.0 to 1.5 liters. Adler et al. (1996) [17] studies show the chest expansion may cause 20% error in the center of EIT images. The averaged resistivity changes in the lung region caused by chest expansion were between 0.65 and 18.31% (Zhang and Patterson 2005) [18]. The influences of the expansion in the local regions such as area 1 and 2, which are away from the center of EIT image, are relatively small. This may be why the relationship for area 1 and 2 is more linear.

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.