A NEW LINEAR ARRAY IMAGING SYSTEM OF ELECTRICAL

AND ULTRASONIC PROPERTIES IN A LIVING BODY

Akira Kimoto, Yuuta Taninaka and Katsunori Shida

Faculty of Science and Engineering, Saga University, Honjyo 1,Saga, Japan

Keywords: Piezoelectric ceramic transducer, Ultrasonic property, Electrical property.

Abstract: In this paper, a new linear array imaging system of ultrasonic and electrical properties in the living body is

proposed. The proposed imaging system measures not only the ultrasonic property of the living body using

the linear arrayed piezoelectric ceramic transducers, but also the electrical property using the surface

electrodes of each piezoelectric ceramic transducer. From these data, ultrasonic and electrical properties in

the same object space are simultaneously reconstructed. In the experiment, propagation time and electrical

voltage of the living body model are measured by the proposed imaging system based on linear arrayed

eight piezoelectric ceramic transducers. Ultrasonic and electrical properties are reconstructed from the

measurement values. It was found that the ultrasonic and electrical properties in the same space could be

reconstructed by the proposed imaging system. Therefore, it is suggested that the proposed imaging system

has potential for application although there are some problems that must be solved.

1 INTRODUCTION

Imaging techniques based on the ultrasonic property

(Opielinski and Gudra, 2000, Simaeys et al., 2000)

or electrical property (Holder et al., 1993, Barber

and Brown, 1984) of a living body are especially

important in medical field, and have been actively

researched. A non-invasive ultrasonic imaging

system using ultrasonic properties of the living body

has been studied for determining the blood flow

velocity distribution and internal organ imaging

(Nitta et al., 1996, Lopez et al., 1992). The electrical

impedance computed tomography using electrical

properties of the living body has also been

developed for imaging of the heart and lungs (Fuks

et al., 1991), temperature distribution measurements

(Conway et al., 1992) and so on.

The aim of our research is to establish a non-

invasive simultaneous imaging system of two

parameters in the living body such as temperature

and a body composition. To achieve it, we propose a

new linear array imaging system of ultrasonic and

electrical properties in the living body. In the

proposed system, the ultrasonic propagation time is

measured by the linear arrayed piezoelectric ceramic

transducers. In addition, the electrical potential is

measured by the surface electrodes of poizoelectric

ceramic transducers (Kimoto and Shida, 2001, 2002).

Therefore, it is possible to measure the ultrasonic

and electrical properties in the same object space

using the proposed imaging system. From these data,

ultrasonic and electrical properties in the living body

are reconstructed. Moreover, two parameters such as

temperature and composition are estimated from

their reconstructed distributions.

In this paper, the imaging system with the linear

arrayed eight piezoelectric ceramic transducers is

established. In the experiment, ultrasonic

propagation time and electrical voltage in 0.1 %

saline solution with acrylic as the living body model

are measured by the proposed imaging system, and

then, the reconstructions of ultrasonic and electrical

properties are demonstrated from their measuremet

values.

2 PRINCIPLE

The ultrasonic and electrical properties in the living

body are generally measured by different sensors. In

the proposed method, they are measured by the same

sensor. Figure 1 shows the measurement method of

the ultrasonic and electrical properties in the living

body. In this method, a linear arrayed piezoelectric

ceramics are used. In figure 1(a), an electrical signal

with a resonance frequency of the piezoelectric

372

Kimoto A., Taninaka Y. and Shida K. (2009).

A NEW LINEAR ARRAY IMAGING SYSTEM OF ELECTRICAL AND ULTRASONIC PROPERTIES IN A LIVING BODY.

In Proceedings of the International Conference on Biomedical Electronics and Devices, pages 372-375

DOI: 10.5220/0001543103720375

 SciTePress

ceramic transducer, S

, is applied to a piezoelectric

transducer, and the reflected wave, S

is measured by

the other piezoelectric ceramic transducer. From

these signals, the ultrasonic property of the object is

obtained. In figure 1(b), the constant current is

injected between the surface electrodes of a pair of

piezoelectric ceramic transducers and the induced

voltage between each surface electrodes are

measured. The electrical property is obtained from

the induced voltage and injected current. Therefore,

the ultrasonic and electrical properties in the same

object space are obtained using a pair of

piezoelectric ceramic transducers. Moreover, the

reconstructed distributions of the ultrasonic and

electrical properties are respectively obtained from

the measured values by using linear arrayed many

piezoelectric ceramic transducers.

Ultrasonic property

Time of flight

(a)

Electrical property

(b)

Figure 1: Measurement method. (a) Measurement of

ultrasonic property. (b)Measurement of electrical property.

3 MEASUREMENT SYSTEM

Figure. 2 shows the schematic diagram of the

measurement equipment. The rectangular equipment

(40×40×100 mm

) was constructed by acrylic plate

and the eight piezoelectric ceramic transducers

(10×5×1 mm

) with 2 MHz resonance frequency are

linearly arrayed with the gap of 1 mm at an acrylic

plate inside the equipment. It is filled with the 0.1%

saline solution as the living body model.

Figure 3 shows the outline of the measurement

system. In the ultrasonic measurement, the burst

wave of the five sinusoidal waves with the

amplitude of 10 V and the 2 MHz frequency as the

transmitted wave is given to one of the piezoelectric

ceramic transducers by the function generator. The

reflected wave is measured by each piezoelectric

ceramic transducer. Transmitted and reflected waves

are passed through the AD converter and stored at

the PC. From their waves, propagation time is

obtained.

100

120

40 60

Acrylic

Side view

Top view Side view

[mm]

Piezoelectric ceramic

transducer

18234567

0.1 % saline solution

Figure 2: Schematic diagram of experimental equipment

with linear arrayed eight piezoelectric ceramic

transducers.

Imaging area

I/O board

AD converter

GPIB board

VI C VI C VI C VI C VI CVI C

VI C

Switch1 Switch2 Switch3 Switch4 Switch5 Switch6 Switch7 Switch8

Function

generator

Switch box

VI C:V-I converter

Figure 3: Schematic diagram of measurement system.

In the electrical measurement, the sinusoidal

current of 1mA, which sinusoidal voltage with the

amplitude of 1 V and 10 kHz frequency is converted

by V-I converter, is injected between the surface

electrodes of a pair of piezoelectric ceramic

transducers. The voltages induced on rest of surface

A NEW LINEAR ARRAY IMAGING SYSTEM OF ELECTRICAL AND ULTRASONIC PROPERTIES IN A LIVING

BODY

373

electrodes of piezoelectric ceramic transducers are

measured. Each voltage is also digitalized by the AD

converter and stored at the PC.

The ultrasonic and electrical measurements and

the selection of piezoelectric ceramic transducers are

changed using the switching system controlled by

the I/O signal.

4 EXPERIMENT

Figure 4 shows the experimental model. 0.1 % saline

solution model, which acrylic (10×10 mm

) is

inserted at the position of 15 mm apart from the

piezoelectric ceramic transducers, was prepared. The

ultrasonic and electrical distributions are

respectively reconstructed from the measurement

values of ultrasonic propagation time and electrical

voltage. In this time, propagation time and voltage

for reconstructing the ultrasonic and electrical

distributions were measured as follows.

Propagation time as ultrasonic property was

obtained from transmitted and reflected waves

measured at each piezoelectric ceramic transducer

from No.1 to No.8. Therefore, ultrasonic distribution

was obtained from eight data. In electrical property,

the voltage induced at surface electrode of

piezoelectric ceramic transducer between a pair of

surface electrodes used as current electrodes was

measured. Table 1 shows the combinations of

current and voltage electrodes. Therefore, 56 voltage

values were used for the imaging of electrical

property. In this time, impedance distribution as

electrical property was reconstructed by the

measured data and the numerical calculation using

the finite element method (FEM).

Table 1: Combination of electrical measurement.

Current electrode

numbers

Voltage electrode

number

(1,3), (2,4), (3,5),

(4,6),(5,7),(6,8)

(2), (3), (4),

(5), (6), (7)

(1,4), (2,5), (3,6),

(4,7), (5,8)

(2,3), (3,4), (4,5),

(5,6), (6,7)

(1,5), (2,6),

(3,7), (4,8)

(2,3,4), (3,4,5),

(4,5,6), (5,6,7)

(1,6), (2,7), (3,8) (2,3,4,5), (3,4,5,6),

(4,5,6,7)

(1,7), (2,8) (2,3,4,5,6), (3,4,5,6,7)

(1, 8) (2,3,4,5,6,7)

Figure 5 shows the 26 unknown elements of

impedance estimated by FEM. Impedance values in

other regions are those of 0.1 % saline solution.

Impedance of each element was estimated by the

modified Newton-raphson method as the iterative

method (Kimoto and Shida, 2000).

Acrylic

0.1 % saline solution

Piezoelectric ceramic

transducer

18234567

15 mm

Figure 4: Reconstructed model.

Figure 5: Estimated elements of electrical property.

(a)

1.02

0.80

[%]

(b)

Figure 6: Reconstructed results. (a) The ultrasonic

propagation time. (b)The change ratio of electrical

impedance.

5 RESULTS

Figure 6 shows the reconstructed results of

ultrasonic and electric properties. Figure 6(a) shows

the positon of reflected wave obtained by the

propagation time and the sound speed. In this time,

BIODEVICES 2009 - International Conference on Biomedical Electronics and Devices

374

sound speed was calculated by propagation time

measured in 0.1 % saline solution and 40 mm

distance of equipment. From figure 6(a), it is found

that the boundary of the target in 0.1 % saline

solution is obtained although it was difficult to

detect the construction of the target. Figure 6(b)

shows the impeadace change ratio between 0.1 %

saline solution with and without acrylic at three

iteration. From figure 6(b), it is found that impedace

in the part of acrylic decreased although the

estimated resolution is insufficient. In this system, it

is possible to reconstruct the ultrasonic and electrical

properties by measuremets of propagation time and

voltage. In addition, it is suggested that the

resolution of the reconstructed image would be

improved by combining the ultrasonic and electrical

reconstructed images because their reconstructed

distributions are different.

6 DISCUSSION

The accuracies of reconstructed distributions of

ultrasonic and electrical properties were insufficient.

They are mainly caused by measurement error of the

system and insufficient measured data number. The

measurement system, especially, the switching

system must be improved. Data number will be also

increased by using several measurement

combinations.

In this time, although ultrasonic and electrical

measurements are changed by the switching system,

simultaneous measurements of the ultrasonic and

electrical properties are possible in which one

electrical signal is created from the electrical signal

with the resonance frequency for ultrasonic

measurement and that of the electrical impedance

measurement and is applied to the electrode as an

alternating current.

7 CONCLUSIONS

A new linear array imaging system of ultrasonic and

electrical properties in the living body was proposed.

In the proposed imaging system, the ultrasonic

propagation time is measured by the linear arrayed

piezoelectric ceramic transducers and the electrical

potential is also measured by the surface electrodes

of poizoelectric ceramic transfuces. Therefore, it is

possible to measure the ultrasonic and electrical

properties in the same object space using the

proposed system. From these data, ultrasonic and

electrical properties in the living body are

reconstructed. In the experiment, the ultrasonic and

electrical properties in 0.1 % saline solution with

acrylic as the living body model were reconstructed

from propagation time and voltage measured by the

proposed imaging system. As a result, it was

suggested that the proposed imaging system has

potential for application although there are some

problems that must be solved.

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