ULTRA-WIDEBAND SIGNALS FOR THE DETECTION OF WATER

ACCUMULATIONS IN THE HUMAN BODY

Johannes Schmid, Lukasz Niestoruk, Stefan Lamparth, Wilhelm Stork

Institut f

ur Technik der Informationsverarbeitung, Universit

at Karlsruhe (TH), Germany

Elena Pancera, Xuyang Li, Thomas Zwick

Institut f

ur Hochfrequenztechnik und Elektronik, Universit

at Karlsruhe (TH), Germany

Keywords:

Ultra-wideband (UWB), Water detection, Signal processing, Water accumulations, Medical UWB.

Abstract:

In this paper, the concept for an Ultra-wideband (UWB) radar system for the detection and quantiﬁcation of

water accumulations in the human body is presented. With this system, the amount of water in human organs

(e.g. the bladder or the lung) can be estimated by processing reﬂected UWB signals. A simulation-based prove

of concept of this approach is presented and it is shown that the system promises a feasible way to implement

a mobile on-body water detection system for medical applications. Based on the simulation results, it can be

concluded that UWB technology is a very promising opportunity for the realization of a mobile and continuous

on-body water detection system that can drastically reduce the costs in different areas in the ﬁelds of urology

and cardiology.

1 INTRODUCTION AND

MOTIVATION

The continuous detection and quantiﬁcation of wa-

ter accumulations in the human body is an important

topic in various medical ﬁelds. In urology, neurolog-

ical diseases can cause a loss of the ability to detect

the ﬂuid level in the bladder (eg. paraplegic patients)

which makes an external determination of the urina-

tion intervals necessary and often causes a perma-

nent catheterization. Also, these therapies often cause

complications due to infections and lead to immense

follow-up costs for the health care system (Hohenfell-

ner, 2009), (GBE, 2009). Another use is the monitor-

ing of the ﬂuid level in the bladder of senior persons

that suffer from dehydration because they regularly

don’t drink enough (DGE, 2007).

In cardiology, heart failure (HF) is one of the top

three most common causes of death (Destatis, 2009),

(GBE, 2009) and a pulmonary edema is an indication

of an insufﬁcient heart functionality (GBE, 2009),

(Fromm et al., 1995). Being able to continuously

monitor the patients lungs could help to instantly no-

tice decompensation and react with an adapted treat-

ment.

In both ﬁelds, a mobile detection and monitor-

ing of the amount of water in human tissue or or-

gans could prevent patients from being hospitalized

and save resources. In this paper, a new approach to

measuring the amount of water inside the human body

based on Ultra-wideband technology is presented.

The reﬂections of UWB pulses impinging on the

human body are used to deduce the ﬂuid concentra-

tion in the reﬂecting organ or tissue. In Fig. 1 the

concept scheme of the proposed method is shown.

Figure 1: Concept of the on-body water detection system.

In section 2, an analysis of the state of the art in the

ﬁelds of UWB radar systems and medical applications

397

Schmid J., Niestoruk L., Lamparth S., Stork W., Pancera E., Li X. and Zwick T. (2010).

ULTRA-WIDEBAND SIGNALS FOR THE DETECTION OF WATER ACCUMULATIONS IN THE HUMAN BODY.

In Proceedings of the Third International Conference on Bio-inspired Systems and Signal Processing, pages 397-400

DOI: 10.5220/0002694003970400

 SciTePress

of UWB technology is presented. In section 3, results

of a simulated setup are shown to prove the feasibility

of this approach. In the last sections conclusions and

an outline of planned future research on this topic is

presented.

2 STATE OF THE ART

2.1 Deﬁnitions and Terminology

Ultra-wideband describes a radio pulse technology

with a signal bandwidth greater than 500 MHz or

the fractional bandwidth of 20 %. In Germany, the

Federal Network Agency (”Bundesnetzagentur”) has

adopted the regulations of the European Conference

of Postal and Telecommunications Administrations

(CEPT) for UWB signals (Bundesnetzagentur, 2008).

It is important to be noticed that a maximum spectral

density of -41.3 dBm/MHz is allowed for all UWB

applications.

The main application areas for the technology in-

clude imaging, radar and communication systems and

the ﬁeld is currently under very intensive research.

For low power communication, ﬁrst commercial chips

will be available in the near future (Decawave, 2008).

2.2 Ultra-wideband Radar

One of the most interesting research areas is the us-

age of UWB pulses for radar applications. Different

objects and their positions can be detected by inter-

preting reﬂected UWB signals. The short pulses (typ-

ical time domain duration of Full Width at Half Max-

imum of 100 ps) provide a very high range resolu-

tion and the large bandwidth (more than 500 MHz)

allows a ﬁne radar resolution of closely spaced ob-

jects (Rahayu et al., 2008). So far, the main appli-

cations are in the ﬁelds of automotive (e.g. park-

ing assistance, pre-crash sensing, blind spot detection,

stop&go (Dominik, 2007)) and of through-wall detec-

tion (Chamma, 2007), (Lubecke et al., 2007).

2.3 Medical Applications

Also in medical imaging, UWB signals can be used

as radar. A scan of the part of the body under exami-

nation results in an image of the underlying structure.

A precise analysis of the reﬂected signal can deliver

information about the substances in the body and their

amounts (Tan and Chia, 2004). Depending on the fre-

quency range used, further possible applications in-

clude cardiac biomechanics and chest movements as-

sessments, obstructive sleep apnoea monitoring, soft-

tissue biomechanics research, heart and chest imag-

ing, and also cardiac and respiratory monitoring, sud-

den infant death syndrome monitor and vocal tract

studying (Staderini, 2002). A feasibility study on us-

ing one UWB device for communication and radar is

presented in (Bilich, 2006). In (Gupta et al., 2008) a

FM-UWB system for sensing purposes in biomedical

applications is proposed and implemented in a Heart

Rate Monitoring application.

So far, not much work has been done concerning

measurements of water accumulations in the body. To

our knowledge only one other group did also iden-

tify water blobs in the human body in the course of

work on an imaging systems for breast cancer detec-

tion (Khor and Bialkowski, 2007).

3 SIMULATION

Goal of the simulation is to show the feasibility of the

system concept. The reﬂections of UWB pulses im-

pinging on a realistic model of a section of the human

body are recorded. All parameters are adjusted and

tuned to obtain a realistic simulation of the bladder in

the human body.

3.1 Setup

The developed model of the human bladder is based

on the anatomical drawings from (R.Pabst, 2009),

Fig. 2.

Figure 2: Anatomical drawings of the human bladder,

empty and full.

For the simulation, multiple dielectric layers (skin,

fat, muscle, bladder and bone) are used as a repre-

sentation of the bladder (Fig. 3). The thicknesses

of the different layers were chosen in accordance to

the anatomical model from (R.Pabst, 2009) for an ex-

emplary human body, the thickness of the layer that

represents the bladder is changed in accordance to the

state (empty or full).

According to (C. Gabriel and Corthout, 1996),

(S. Gabriel and Gabriel, 1996), the frequency depen-

dency of the dielectric properties of the biological tis-

BIOSIGNALS 2010 - International Conference on Bio-inspired Systems and Signal Processing

398

Figure 3: Model of the bladder with multiple dielectric lay-

ers for simulation (E

: incident electric ﬁeld, E

: reﬂected

electric ﬁeld).

sues are considered. An approximation of the fre-

quency dependency of the dielectrics is applied. The

direction of an incident wave (E

) is orientated per-

pendicularly to the left surface skin (Fig. 3). A plane

wave is applied at a distance shortly before the layer

of skin to generate the UWB pulse. Due to this im-

pinging wave penetrations and reﬂections of UWB

pulses in the multiple dielectric layers are performed.

The reﬂected signal (E

) is received by a probe at a

distance of 0.5 m.

3.2 Results

Two simulations of the proposed model are taken. A

full bladder with urine and an empty bladder are mod-

eled. The differences between these two cases are the

thickness of the bladder muscle (thinner for the ”full”

case) and the amount of urine (larger amount for the

”full” case i.e. thicker bladder). The reﬂected UWB

pulses are recorded, the results are shown in Fig. 4

with a solid line for the full bladder and dotted line

for the empty bladder.

Three strong reﬂections marked with numbers are

identiﬁed from the received electric ﬁeld E

in both

cases (the peak of the transmitted pulse is 1 V/m). The

skin and urine in the bladder have an increased per-

mittivity in comparison to the fat, muscle and bone.

The strong reﬂections r

and r

occur on the bound-

ary between air and skin. r

and r

are the reﬂec-

tions from the boundary between bladder muscle and

urine, while r

and r

are caused by the boundary be-

tween urine and right bladder muscle. A time differ-

ence between r

and r

in the two simulation results

(full case, empty case) is noticed. This is due to the

expansion of the bladder and the displacement of the

reﬂection point which results in a different propaga-

tion time of the electromagnetic waves through the

bladder in the two cases. Thus, the reﬂection proper-

ties can be utilized for the recognition of water in the

body and its amount in the bladder can be estimated.

Figure 4: Received electric ﬁeld E

of the UWB pulses by

the probe: full (solid) vs. empty (dotted) bladder. (full case:

, r

and r

; empty case: r

, r

and r

For the detection and the measurement of water

accumulations in other human organs like the lung,

an evaluation of the amplitudes has to be added to the

signal processing in addition to the propagation time

analysis. The measuring principle remains the same.

4 CONCLUSIONS

The results of the simulations show that the proposed

concept is a feasible way to detect water accumula-

tions in human organs. In the presented example the

detection of water in the bladder is simulated. To ap-

ply the concept to the lung or other organs, the signal

processing has to be adapted and the different attenu-

ation properties and the velocity of propagation have

to be evaluated. This approach allows to develop a

mobile on-body prevention system for various medi-

cal problems that require a continuous monitoring of

the ﬂuid level in a human organ.

5 FUTURE WORK

The next steps include the continuation of the simu-

lations by verifying, crosschecking and reﬁning the

introduced model of the human bladder to obtain re-

sults as realistic as possible. It is then planned to also

model the human lung and to develop signal process-

ing algorithms to evaluate not only the signal offset

but also the amplitude changes of a reﬂected signal in

dependency of the water amount or concentration in

the measured organ. After that, a prototype will be

developed for experimental testing and evaluation of

the signal processing algorithms.

ULTRA-WIDEBAND SIGNALS FOR THE DETECTION OF WATER ACCUMULATIONS IN THE HUMAN BODY

399

ACKNOWLEDGEMENTS

This work was carried out in the framework program

”Mikrosystemtechnik f

ur die Lebenswissenschaften”

of the foundation of Baden W

urttemberg (Landess-

tiftung BaW

u).

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