Detection of the Biological Active Point using the Bioimpedance System based on the Adaptive
FrequencyTracking Filter and the Transition Event
Detector
Hodong Park1, Sungpil Cho1, JaeyeonShin1, Kyoungjoung Lee2,Hojun Yeom3
1
MEZOO Inc., Wonju, South Korea
Department of Biomedical Engineering, Yonsei Univ.,Wonju,South Korea
3
Department of Biomedical Engineering, Eulji Univ., Sungnam, South Korea
2
[email protected]
Abstract. The biological active points (BAP) are known as low resistance spots
or good electro-permeable points, have relativelower electric resistance than the
surrounding tissues. In this study, a new method for BAP detection using the
bio-impedance measurement system based on the adaptive frequency
trackingfilter (AFTF) and the transition event detector is presented
Keywords: Biological active points, Bio-impedance, transition event detector
1 Introduction
According to Traditional Oriental Medicine,there exists a relationship between
organs and the biological active points (BAP)which are called acupuncture points in a
human body. Bio-impedance measurement of human skin are non-invasive and
widely used for various clinical applications, such as investigation of transdermal
drug delivery and others [1][2]. We propose a new method for detection the BAPs
using the equivalent circuit model and the multi-frequency impedance characteristics
of the BAPs which are different from the characteristics of the surrounding
skin.Multi-frequency bio-impedance methodgenerally has been used as a measure of
differences in body water and fat distribution [3]. Bio-impedance signals demodulated
by each frequency have been applied to the transition event detector based on the
phase space method [4].
2. Methods and Experimental Setup
The data acquisition system is composed to a current source using a
microcontroller (Analog Device ADUC 7021 with A/D and D/A converter). The
current source is used to generate a sinusoidal signal where the frequency can be
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selected between 3 Hz to 100Hz. And then the generated current is passed by the
human skin. The reference electrode is made from brass with wide dimension and the
active electrode is made from with yellow brass which diameter is 3mm. The
measurements were done especially for PC6 point of the Pericardium Meridian and
TE5 point of Triple Energizer Meridian. Measurements of the BAPs were performed
on atotal of 50 BAPs from 25 subjects.
Digital Hilbert transform filter can be employed for this purpose. We present a
structure of the transition event detectorto detect the transition event to the BAP area
from the surrounding skin. This processor was implemented using the phase space
method (PSM), which is a sort of a topology mapping method, and a least-squares
acceleration filter (LSAF) [4].
The PSM is a topology mapping algorithm that can detect points from a
characteristic form of the signal occurring in real time. Further, the LSA filter has
been proposed to estimate the derivative or acceleration of a digitized signal. LSAF is
a simple mathematical algorithm used to detect the most morphologically distinct
sharpness. We can simply adjust the order to make the window length equal to the
typical duration of the waveform whose sharpness is to be measured. The output of a
pth-order LSA filter, xÖ(n) , is defined as
p 1
š
x ( n)
¦ l K(n i)
i
(1)
i 0
where K(n) is the contaminated signal used as the input of the LSA filter and
li ,0 d i d p 1 , are the weights of the LSA filter. This approach is computationally
simple, can be performed in real time, and is robust in the presence of noise.
In the course of the event detection process, the signal K(n) is applied to the
LSAF. After the LSA filtering, a topology mapping method (PSM) is used to extract
the transitionarea from surrounding skin. Finally, decision of BAP area is achieved.
3Results
Fig. 1.The results using real data :outputs of the AFTF using real data -(a)measured multi-
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frequency signal (b)40Hz (c)80Hz (d)160Hz (e)240Hz, Phase space plots of demodulated
signals ±(f)40Hz (g)80Hz (h)160Hz (i) 240Hz
To detect the area transition, a topology mapping from the demodulated
signalisused. The topology mapping is processed in realtime. The demodulated
signals, the output of the AFTF, are mapped onto the second dimensional phase space
plot with respect to delays of five samples. The AFTF output signalsand trajectories
of those in real dataare shown in Fig.1. As shown in Fig.1(a)-(e), the transition of
phase was induced in the BAP.Unlike the surrounding skins, characteristic and
particular patterns of BAP areas were shown in PSM plots.The region of surrounding
skin is shaded in Fig.1(f)-(i). As using these particular patterns, we can detect
accurately the BAPs on searching the surrounding skins. Therefore if the areas of the
transition of phase are searched, the BAP can be detected easily and simply.
4Discussions and Conclusions
In this study, the bio-impedance measurement system based on the adaptive
frequency tracking filter (AFTF) and the transition event detectoris designed to detect
the BAPs.The microcontroller performed continuous demodulation by multi
frequency components using the AFTF. Therefore this method can be used in real
time application because the transition of phase in the BAP is only detected.
As shown in results, it has been found that the bio-impedance transition
characteristics of theBAPs, studied in this work, differ from those corresponding tothe
surrounding skin. From the results obtained,we propose that an analysis of the
characteristictransition patternsat the BAPs could be used to decision of the human
BAPs if such system was performedin real time.
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