title: Variability in EIT Images of Lung Ventilation as a Function of Electrode Planes and Body Positions.
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.
authors.affiliation: Division of Medical Physics, Department of Radiology, University of Kentucky, Lexington, KY 40536, USA.
authors.forename: Jie
authors.initials: J
authors.lastname: Zhang
authors.affiliation: Department of Physical Medicine and Rehabilitation, University of Minnesota, Minneapolis, MN 55455, USA.
authors.forename: Robert
authors.initials: R
authors.lastname: Patterson
keywords: EIT; electrical impedance topography; lung; variability.; ventilation
references.citation: Clin Phys Physiol Meas. 1988;9 Suppl A:79-85
references.pmid: 3240655
references.citation: Physiol Meas. 2013 Jun;34(6):567-77
references.pmid: 23719577
references.citation: Physiol Meas. 2003 May;24(2):467-75
references.pmid: 12812430
references.citation: Physiol Meas. 2011 Jul;32(7):731-44
references.pmid: 21646709
references.citation: Physiol Meas. 2013 Jun;34(6):659-69
references.pmid: 23719130
references.citation: IEEE Trans Med Imaging. 1999 Sep;18(9):764-73
references.pmid: 10571381
references.citation: Clin Phys Physiol Meas. 1987;8 Suppl A:155-65
references.pmid: 3568565
references.citation: Physiol Meas. 2009 Jun;30(6):S35-55
references.pmid: 19491438
references.citation: Clin Phys Physiol Meas. 1987;8 Suppl A:47-54
references.pmid: 3568570
references.citation: Physiol Meas. 2000 May;21(2):R1-21
references.pmid: 10847187
references.citation: Physiol Meas. 2005 Apr;26(2):S81-92
references.pmid: 15798249
references.citation: Med Biol Eng. 1967 May;5(3):239-48
references.pmid: 6045783
references.citation: IEEE Trans Biomed Eng. 1996 Apr;43(4):414-20
references.pmid: 8626190
references.citation: Physiol Meas. 2012 May;33(5):679-94
references.pmid: 22532268
references.citation: Intensive Care Med. 2006 Sep;32(9):1392-8
references.pmid: 16799773
references.citation: Physiol Meas. 1995 Aug;16(3 Suppl A):A191-211
references.pmid: 8528117
references.citation: Physiol Meas. 2002 Feb;23(1):3 p preceding R1
references.pmid: 11876239
references.citation: Eur J Heart Fail. 1999 Dec;1(4):379-84
references.pmid: 10937951
references.citation: Physiol Meas. 2007 Jul;28(7):S13-27
references.pmid: 17664631
references.citation: Physiol Meas. 2000 Feb;21(1):155-63
references.pmid: 10720011