Z. Q. ZHAO ET AL.
Copyright © 2013 SciRes. ENG
6] and in patients with mild, moderate, and severe lung
diseases [7-9]. However, evaluation of EIT measurement
is not easy for doctors since 1) there is no established
guideline for measurement; 2) commercially available
software is device specific and rarely extensible for var-
ious clinical trials; 3) open source software is compre-
hensive but not disease specific.
We recently developed a customized EIT evaluation
software for a clinical study in university hospital
Schleswig-Holstein. The examination protocol of the
clinical trial is briefly described, followed by the devel-
opment process of the software.
2.2. Examination Protocol
At the time point of writing the manuscript, over one
hundred patients with chronic obstructive pulmonary
disease (COPD), cystic fibrosis (CF), or asthma were
included in the clinical trial. All subjects were examined
by spirometry (Jaeger pneumotachograph, CareFusion,
Höchberg, Germany) and EIT (Goe-MF II EIT system,
CareFusion, Höchberg, Germany) in a seated position
during spontaneous tidal breathing. They were asked to
perform full inspiration from functional r esidual capacity
to total lung capacity, followed by standard forced full
expiration maneuver and at the end back to spontaneous
tidal breathing (F ig ure 1) [2]. For the EIT measurement,
16 ECG electrodes were placed on the chest circumfe-
rence in the 5 - 6th intercostal space (parasternal line)
and one reference electrode on the abdomen in each sub-
ject. Data acquisition lasted about 60 - 100 s.
2.3. Development of the Evaluation Software
Software requirements and design: The engineers from
Furtwangen University and the clinicians from Universi-
ty Medical Center Schleswig-Holstein have held a series
of meetings to discuss the settings of the clinical trial; to
elicit, analyze, specify and validate the requirements of
the evaluation software. Illustrations of various disease-
specific parameters and indices were graphically summa-
rized by the clinicians (e.g. Figure 2(A)). Evaluation
requirements were described in functional flow block
diagram (Figure 2(B)).
Software construction: Considering that a very useful
EIT open source tool EIDORS [10] is programmed with
MATLAB (The MathWorks, Natick, MA, USA), the
evaluation software is written with MATLAB (Ver. 7.2)
and built with MATLAB Deploy tool and C++ Compiler.
Software testing and refinem ent : The behavior and
performance of the evaluation software was dynamically
verified on a set of test cases before delivered to the phy-
sicians. Feedback was given by the physicians after test-
ing the software on patient data. Unexpected behaviors of
the software due to misunderstanding or bugs were cor-
Figure 1. Spirogram of lung volume changes during the
examination. Four phases are recognized: spontaneous tidal
breathing, vital capacity maneuver, forced expiration ma-
neuver and again spontaneous tidal breathing. VT: tidal
volume; ΔEELV: change of end-expiratory lung volume.
rected. This testing-improving process was repeated sev-
eral times to improve the software.
3. Results
The software consists of two parts: The physicians use the
first part to process the raw measurement data (Figure
3(A)). Five different EIT raw and image data formats can
be recognized. EIT images are reconstructed with either
back projection or GREIT method and can be extended
easily. Fifty frequently used clinical parameters such as
forced expiratory volume in 1 second (FEV1) and peak
expiratory flow (PEF) and their quotients can be quickly
calcula te d by c licking the c or r e s ponding butt ons . EIT data
and results are graphically displayed and as different for-
mats exported or printed (e.g. JPEG, TXT, XLS, PDF;
Figure 3(B)). Simple filters such as moving average and
butterworth are implemented to suppress signals other
than respiration.
In the second part of the software, various disease-spe-
cific parameters and indices can b e displayed as function-
al images or histogram in different scales and combina-
tions (Figure 4). Comparison of the parameters between
measurements, among different maneuvers or among dif-
ferent patients can be easily conducted via choosing the
corresponding options. Several validity checks (e.g. the
study group, the input ranges) are performed to prevent
mistakes of data evaluation.
4. Discussion and Conclusions
In the present study, we demonstrated the development
process of a customized evaluation software for a clinical
trial of pulmonary function test with EIT. The custo-
mized software has the following advantages compared
to the data process with device specific program and other