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Studies in System Science (SSS) Volume 2, 2014
A Study of Applications of Medical
Piezoelectrical Ultrasonic Transducer
Materials and the Transducers
Quanlu Li*1, Jing Wu 2, Yinhong Zhang3
School of Physics an d Information Technology, Shaanxi Normal University,
No. 199, Chang’an South Road, Xi’an, Shaan xi 710062, China
*1
2
3
lql0314@snnu.edu.cn; wujing@snnu.edu.cn ; zhangyh@snnu.edu
Abstract
This paper briefly reports the design, preparation and testing properties of tw o medical piezoe lectrical ultrasonic transducer
materials (i.e. SF − PZT ( k p of F2 − PZT is 0.52, its Qm is 1010, and tgδ is 2.3), F1 − PZT ( K p of F1 − PZT , is 0.50 and its
Qm is 780, but, tgδ, dielectric loss, is 2.3) and F2 − PZT ( k p of F2 − PZT is 0.52, its Qm is 1010, and tgδ is 2.3) ) effect to
(Tow apparatuses designed and manufactured with the two piezoelectrical materials mentioned above) high-performance medical
piezoelectric ultrasonic diagnosis transducer (i.e. an A-mode medical ultrasonic diagnosis transducer—single-probe) and medical
piezoelectric ultrasonic therapeutic transducer which were used for clinical practice and obtained the expected results. Moreover,
the performance parameters of the clinically-tried A-mode medical ultrasonic diagnosis transducer (single-probe) are superior to
the primary probes of the commonly used ultrasonic diagnosis equipments (made in China or imported from abroad). The medical
experts who witnessed the whole process of the clinical-trial of the new apparatus agree that the ultrasonic diagnosis transducer
proves to be technically mature and clinically efficient and can be applied for diagnosis of all cases of the relevant category of our
ultrasonic therapeutic transducers with “the ultrasonic therapeutic equipments of acupuncture point of human body”, “UTM—1
type ultrasonic-thermotherapy-medical therapeutic machine”, etc getting good medical treatment effects for different illness at
800~900kHz, to treat many and varied diseases of the patients which are especially remarkable, and there are not any side effects
for all of the sufferers. Finally, some problems of the medical piezoelectric materials (including lead-free piezoelectric materials etc)
and medical piezoelectric devices (including medical ultrasonic imaging systems, ultrasonic holography and ultrasonic
computerized tomography, etc), etc used for the ultrasonic medicine which needs further researches are pointed.
Keywords
Medical Piezoelectric Ultrasonic Transducer; Piezoelectrical Ultrasonic Transducer Material; Ultrasonic Medicine; Application
Introduction
Rapi d development of medical ultrasonics, including ultrasonic diagnosis an d ultrasonic therapy, is needed in the
development of new medical ultrasonic apparatus (including medical ultrasonic i maging systems, ultrasonic
holography and ultrasonic computerized tomography, etc), especially core of the n ew apparatus, ultrasonic
transducer which is made of the new piezoel ectric materials. The present paper reports on preparations an d
applications of two kind medical piezoelectrical ultrasonic transducer materials, high-performance medical
piezoelectric ultrasonic di agnosis transducers and medical piezoelectric ultrasonic therapeutic transducers in present
work, these materials an d devices for development of ultrasonic medicine will be of significant advance, an d
increasing the general level of the people’ s health is of great immediate significance.
Preparations of Two Kind Med ical Pie zoelectrical Ultrasonic Transducer Materials
1)
Formulae of the Two Kind Medical Piezoelectrical Ultrasonic Transducer Materials
Because of slightly changing the chemical composition of the piezoelectric ceramics, it is possi ble to emphasize
one or more specific properties so that speci al requirements can be met. The below formula is based on our
long-term investigation an d st udy for some PZT. Such complicated composition can be obtained by adding
foreign matter in the make- up of a formulation to improve the properties of some PZT. Notes: (for applied fi elds
of acoustoelectric transducing) F shows transmitting type pi ezoelectric ceramic mat erials; SF shows
transmit-receiving type piezoelectric ceramic materials.
SF − PZT is expressed as: Pbx Sr1− x ( ZryTi1− y )O3 (x =0.93~0.96; y=0.52~0.55)
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with small amount of NiCO3 , Cr2O3 an d PbO added.
F1 − PZT is expressed as: x[ Pby Sr1− y ( ZrmTi1−m )O3 ] + (1 − x )BiFeO3
(x=0.995~0.998; y=0.91~0.96; m=0.50~0.53)
with small amount of Fe2O3 , MnO2 an d PbO added.
F2 − PZT is expressed as: Pbx Sr1− x ( ZryTi1− y )O3 + m%( wt )K 2O + n%( wt )Fe2O3
(x=0.92~0.96; y=0.50~0.53; m=0.1~0.4; n=0.2~0.6)
2)
Flow Chart of Technological Process of the Two Kind Medical Piezoelectrical Ultrasonic Transducer
Materials
In the present study, we have applied the theory and practice of molecular design to determine the correct
formulation an d to use dry method ceramic technologies operations, their cardinal processes of development
technique an d flow chart of technological process are as follows: (1). Designing formulation, selecting raw
materials, grinding (class of superfine pow der); (2). Calculation, make-up the formula; (3). Mi xing of raw materials;
(4). pre-pressing; (5). calcination (first sintering); (6). grinding; (7). High speed fluid energ y milling or superfine
vibration-mill; (8). Granulation; (9). Forming by dry pressing; (10). de-adhesives; (11). Sintering; (12). Finishing
after sintering; (13). Metalizing; (14). Polarizing; (15). Ageing; (16). Testing an d measuring; (17). Piezoelectric
element.
After finishing the sintering and metallization, piezoelectric ceramic crystals must be polarized to gain
piezoelectricity. Each polarizing condition (voltag e V, temperature T and time t) of some piezoelectric ceramics is
omitted.
3)
Principal properties of Two Kind Medical Piezoelectrical Ultrasonic Transducer Materials
After fabrication and metallization, piezoelectric ceramic crystals cannot possess piezoel ectricity and become
piezoelectric elements when polarized. As these PZT crystalline pellets (made by ourselves) have all passed ageing,
their properties must be tested an d measured by IEEE standard on piezoelectricity. The principal properties of
two kind of medical pi ezoelectrical ultrasonic transducer materials in present work are shown in Table 1. In the
measurements of the PZT piezoelectric ceramics, the el ectrical properties of a piezoelectric ceramic vibrator are
dependent on the elastic, piezoelectric, and dielectric constants of the vibrator materials. Thus, val ues of
performance parameter of the vi brator materials (i.e. for these constants) can be obtained from resonator
measurements on a suitably shaped and oriented specimen , provi ded the theory for the mode of motion of that
speci men is known. The basic const ant measurements will determine the electrical impedance of the resonator as
a function of frequency. In principl e it is necessary to measure the resonance and antiresonance frequencies, and
the capacitance. The removal of dissipation factor from the resonance range also n eeds to be measured to obtain
the information necessary for finding the material constants. In some instances, an accurate measurement of the
antiresonance frequency cannot be made, but it is convenient to characterize the resonator by a
lumped- paramet er equivalent circuit and to calculate the material const ant from the measured parameters of this
circuit. The equivalent circuit (the properties of piezoelectrical ceramics an d their devices must be tested and
[1]
measured by IEEE standard on piezoelectricity which refer 1) is shown in Fig. 1; the measured circuit of present
work is shown in Fig. 2; an d the testing and measuring methods of principal properties of piezoelectric ceramics
materials are listed in Table 1 (Notes: the present paper only briefly introduces testing and measuring methods of
some important practical parameters of principal properties of pi ezoelectric ceramics materials, in which d33 is
measured by a d33 -meter that is made in In stitute of Acoustics, Chinese Academy Science).
TABLE 1 PRINCIPAL PROPERTIES OF THE TWO KIND MEDICAL PIEZOELECTRICAL ULTRASONIC TRANSDUCER MATERIALS. NOMENCLATURE OF PROPERTIES OF
PIEZOELECTRIC CERAMICS : K p PLANAR ELECTROMECHANICAL COUPLING FACTOR ; Q m MECHANICAL QUALITY FACTOR ; Ε T33 /Ε 0 RELATIVE DIELECTRIC
CONSTANT; G 33 PIEZOELECTRIC VOLTAGE CONSTANT; TGΔ DIELECTRIC LOSS ; Ρ DENSITY. PROPERTIES IN THE PLANAR MODE ARE MEASURED ON DISCS 20 MM
DIAMETER AND 1-MM THICK.
Materials
symbol
SF − PZT
F1 − PZT
F2 − PZT
Kp
Qm
(pC·N −1 )
0.54
0.50
(×10 −3 V·m·N −1 )
370
780
0.52
1010
ε T33 /ε 0
(×10 −3 )
1450
1200
1130
d 33
g 33
tgδ
(×10 3 Kg·m −3 )
426
370
32
24.8
240
34
ρ
11
7.6
1.9
7.7
2.3
7.74
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Studies in System Science (SSS) Volume 2, 2014
FIG. 1 EQUIVALENT ELECTRICAL CIRCUIT OF A PIEZOELECTRIC VIBRATOR
Notes:
L — seri es inductance in resonator equival ent circuit;
R — seri es resistance in resonator equivalent circuit;
C1 — series capacitor in reson ator equi valent circuit;
C0 — sh unt capacitor in resonator equivalent circuit.
FIG. 2 SCHEMATIC DIAGRAM OF SIMPLE TRANSMISSION-LINE METHOD MEASURING CIRCUIT
Notes:
R T — resi stance (R T < R 1 ; when anti-resonance frequency, R T = 2Ω, 5Ω, 10Ω, 50Ω, 103 Ω,104 Ω, etc. );
R 1 — the sum of output reactance of the signal generator and input reactance of the frequency meter;
R 2 — the input reactance of the millivoltmeter.
Preparations of High-effect Medical Ultrasonic Diagnosis Transducers and Medical Ultrasonic Therapeutic
Transducers
For some basic theory of ultrasonic medicine and the ultrasonic transducers, we have prepared high-performance
medical ultrasonic diagnosis transducers an d medical ultrasonic therapeutic transducers which are made from
SF − PZT and F1 − PZT (or F2 − PZT ) made by ourselves in present work, to apply them to practice of medical
ultrasonics, and, to obtain good effect of medical ultrasonics beyon d what have already been reported in the
literature.
1)
Preparation of High-effect Medical Piezoelectric Ultrasonic Dia gnosis Transducers
Medical ultrasonic diagnosi s transducers are many and vari ed, their properties also are different, but, the
structures of the medical ultrasonic di agnosis transducers are basically same. We have prepared the medical
ultrasonic diagnosis tran sducer as Fig. 3 is a schematic diagram of structure principle of A-mode medical
ultrasonic diagnosis tran sducer (single-probe). Th e front end of the probe is the piezoelectric ceramic crystalline
pellet, lower and upper surface of the piezoelectric ceramic crystalline pellet is spread on an d sinter-permeated
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silver layers (electrodes), and, from each silver layer (electrode) is welded a silver wire. The two wires are
separately connect ed with the centre and sh ell of contact base of the medical ultrasonic diagnosis transducer. The
two links transmit excited high-frequency electric oscillation to the piezoel ectric ceramic crystalline pellet and
return high-frequency electric signal of the echo of the piezoelectric ceramic crystalline pellet to being
transmitted to the receiving amplifier. Th e shell of the medical ultrasonic di agnosis transducer i s made of perspex
which is used as a protective support. Th e front of the pi ezoelectric ceramic crystalline pellet is spread on the film
of epoxy resin which is used to protect the silver layer (electrode) of the piezoelectric ceramic cryst alline pellet,
the thickness of the protective film of epoxy resin should be 1 λ of the wavelength of sound, specific acoustic
2
impedance of the protective film lay between the piezoelectric ceramic cryst alline pellet an d skin of h uman body,
and, at this acoustic impedance, the transmitting effect of sound is very good. The back of the piezoelectric
ceramic crystalline pellet filled in backing layer (sound absorption material) to increase sound damping, an d to
absorb backward soun d waves to be advantageous to ameliorating of longitudinal resolution, and to decrease
interference of miscellaneous waves. The backing layer materi al is more made from epoxy resin and tungsten (W)
powder or epoxy resin combined mercuric oxide (HgO). In present work, we prepared the outer diameter of the
A-mode medical ultrasonic di agnosis transducer (single-probe) which is approximatel y 14 mm and 40- mm length.
In the A-mode medical ultrasonic diagnosi s transducer (single-probe), the diameter of the piezoelectric ceramic
crystalline pellet is approximately 12 mm. the schematic diagram of structure principle of A-mode medical
ultrasonic diagnosis transducers as is shown in Fig. 3.
Fig. 3 THE SCHEMATIC DIAGRAM OF PRINCIPLE OF A-MODE MEDICAL PIEZOELECTRIC ULTRASONIC DIAGNOSIS TRANSDUCERS
2)
Preparation of High-effect Medical Piezoelectric Ultrasonic Therapeutic Transducers
The schematic diagram of principle of which we have prepared the medical pi ezoelectric ultrasonic therapeutic
transducers as i s shown in Fig. 4. In the Fig. 4, ① the metal cap have two effect s: the 1st is fi xed piezoelectric
ceramic crystalline pellet of F1 − PZT (or F2 − PZT they are all made by ourselves), an d 2nd, outer of the met al
cap will transmit the ultrasonic energy to the position of human body some of which will be treated by ultrasonics.
The metal cap must be grounded with the earth being in same el ectric potential to be advantageous to the
personal safety of patient. ② the fixing ring is fixed with the chassis of the transducer together by the screw n ut
close-knit. ③ for the transducer is waterproofed, to pad a rubber ring. ④ the mica spacer is padded between the
pressed blank electrode and the piezoel ectric ceramic crystalline pellet of F1 − PZT (or F2 − PZT ), the purpose
is preventing occasionally a phenomenon which i s sparked from the piezoelectric ceramic crystalline pellet of
F1 − PZT (or F2 − PZT ) at high frequency. ⑤ insulating support is propped up the sustaining spring to press the
piezoelectric ceramic crystalline pellet of F1 − PZT (or F2 − PZT ) closely, and connects the high-tension core
wire and the binding post, to link up the piezoel ectric ceramic crystalline pellet which requires high-voltage and
high-frequency A-C power supply. ⑥ the insulating casing pi pe is used for increasing high-voltage insulating
ability of the whole transducer. As indicated, above method is to fix the piezoelectric ceramic crystalline pellet to
be sample, thus convenient for the ultrasonic energy being transmitted to therapeutic position of human body. As
the Fig. 4 shows, outward of the ultrasonic therapy tran sducer is straight form, for all practical purpose, some of
the ultrasonic therapy transducers also are curved, but, the inside of these tran sducers are fi xed method of the
piezoelectric ceramic crystalline pellet which is roughly the same. The area of the met al cap of ultrasonic therapy
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transducer which is used to tran smit ultrasonic waves has different specifications in 3 cm2 ~12 cm2 , the
piezoelectric ceramic pellet of ultrasonic therapy transducer which needs high-frequency electricity, i s linking up
high-frequency oscillating circuit of ultrasonic therapy machine by the high-frequency coaxial cable.
FIG. 4 THE SCHEMATIC DIAGRAM OF PRINCIPLE OF MEDICAL PIEZOELECTRIC ULTRASONIC THERAPEUTIC TRANSDUCERS
Applications
In present work, our medical piezoelectric ultrasonic diagnosis transducers an d ultrasonic therapeutic transducers
are made by ourselves that have been used for clinical practice and all gain better effects. A-mode medical ultrasonic
diagnosis tran sducers (single-probe) are used to diagnose normal or pathological changes of varied positions of
human body at 2.5 MHz, such as, ki dney, cholecystitis, hepatomeg aly, h epatitis, spleen, hydatidiform mole, etc, get
the clear and unambiguous diagnostic results and for all patients there are not harm an d sufferings, in their
detectable dept and sensitivity, etc, performance parameters of the A-mode medical ultrasonic diagnosis transducers
(single-probe) are superior to the primary probes of the ultrasonic diagnosis equipments (made in China or enter
port from abroad). Medical experts review the ultrasonic diagnosis transducers that can be applied for diagnosis of all
illness of the category of the A-mode ultrasonic di agnosis. Our ultrasonic therapeutic transducers with “the ultrasonic
therapeutic equipments of acupuncture point of human body”, “UTM —1 type ultrasonic-thermotherapy- medical
therapeutic machine”, etc get good medical treatment effects for different illness at 800~900kHz, such as, the
curative effects of prost atitis, around shoulder inflammation, relieve pain, subsidence of a swelling, arthritis, anal
fissure, anal fi stula, stomach trouble, nephritis, hyperplasia of mammary, proctitis, high blood pressure, an d for the
proving blood circulation, their effects are especially remarkable an d there are not any side effect s for all of the
sufferers. The author of present paper deems it to be necessary for the conditions, in a word, all of the clinical cases of
ill of the ultrasonic therapy (or ultrasonic diagnosis) with the transducers of present work are omitted because they
are not focal point in present paper. In the ultrasonic therapy, acoustic intensity i s a important parameter to affect
their therapeutic effect, “Th e selection of the dosage of the acoustic intensity i s relat ed to operating conditions, the
probe whether or not moves, direct radiation or indirect of the ultrasonic energy, radiation of continuous w aves or
pulse waves, the time of the radiation, the angle of incidence of acoustical beam, an d is current different position of
human body”, etc. General is regarded as ultrasonic energy at 0.5~1.5 Wcm−2 is smaller dosage, 1.5~3 Wcm−2 is
mid-dosage, 3~6 Wcm−2 is largest, un der normal conditions they are selected 1 Wcm−2 or so. The opti mum
conditions of the ultrasonic therapy must decide as the clinical experimental results.
Conclusion
Ultrasonic medicine (i .e. medical ultrasonics, is the ultrasonic techniques which is used for the concret e development
and practice of the basic medicine, the clinical medicine, and hygienics, etc medical field.) i s a rapid developing and
newly branch of learning, for increasing the gen eral level of the people’s health is of great immediate significance.
Ultrasonic medicine mainly involves ultrasonic diagnosi s and ultrasonic therapy, etc. Ultrasonic diagnosis originates
from ultrasonic inspection and measurement in the industry, in view of the modern electronics, acoustical principle
combined with the radar techniques, etc to be used as a diagnostic method of clinical medicine. Along with the
informational engineering technology developing an d joining the ultrasonic diagnosis (including medical ultrasonic
imaging systems, ultrasonic holography and ultrasonic computerized tomography, etc) which will be come up to
[2]
newly advanced st andards (the model and sign of the ultrasonic tissue characterization refer 2) . Ultrasonic therapy
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is any method and mean s which applies ultrasonic energy to cure any illness of h uman body. In substance, ultrasonic
therapy is part of the pow er ultrasonics (power ultrasonics is a process which makes use of the energy of ultrasonic
vibration to change the structure states, characteristics an d functions, etc of the substantial organizations, or, to
speed up this change. An active applied technology of the dynamic applications is outstan ding charact eristic of power
ultrasonics, has larg er acoustic power an d higher acoustic intensity). Ultrasonic energy for the tissue of human body
will produce lukewarm effect, massage action, biochemistry effect, and, feeble acoustic cavitations in the tissue fl uid,
etc hybrid actions are the elementary factors of the ultrasonic therapy. Along with the high-techniques developing
and i s applied to the ultrasonic therapy which will be still more effective on curing the sickness and to have more
indications which could be cured with the ultrasonics. S uch as, ultrasonic transmission and absorption of oblique
plane waves though the human skull are analyzed numerically for frequencies ranging from 1/2 to 1 MHz (the
[3]
analyzed n umerically methods for frequencies refer 3) . These frequenci es are optimum for noninvasive ultrasonic
therapy of brain disorders where n umerical predictions of skull transmission are used to set the ph ase an d amplitude
of source elements in the phased array focusing system. But, up to now , piezoelectrical mat erials an d pizeoel ectrical
ultrasonic tran sducers occupy an important place in the ultrasonic medicine, these materials and devices are a
cornerstone of ultrasonic medicine, an d their principal performance directly affects various effects of the ultrasonic
medicine. Thus, research an d developments of new type piezoelectrical material s and high-performance transducers
are long-term assignment in the ultrasonic medicine. The piezoelectrical materi als an d devices also need to be in
company with medical ultrasonic appearances (including ultrasonic power source, el ectric circuits, etc) to develop
forward. The authors are convinced of new developments an d applications of ultrasonic medicine which can
unquestionabl e be attained when new-technology an d high-techniques (including material s, devices, and, a complet e
set of equipment, etc) are joined or applied.
In the other respect, piezoelectric ceramics have wide-ranging important applications in many fields (including
medical piezoelectric ultrasonic di agnosis transducers and medical pi ezoelectric ultrasonic therapeutic transducers,
etc). But, with the deeping of the sense of the human-basic, people’ s consciousnesses of the environ mental protection
is future enhancement, the problems of some piezoelectric ceramics (i .e. PT and PZT etc.) with lead bring to people’ s
good health more think deeply. We must give out the present main research directions of medical piezoel ectrical
ultrasonic transducer materials an d the transducers in the lead-free piezoel ectric ceramics an d lead-free medical
piezoelectrical ultrasonic transducers, which are: BaTiO3 ( BT ), Bi0.5 Na0.5TiO3 ( BNT ) basic lead-free piezoelectric
ceramics and bi smuth (Bi) layer structure pi ezoelectric ceramics, which have been used for partial “green an d
environmental protection type” medical ultrasonic equipments(including medical ultrasonic imaging systems,
ultrasonic holography and ultrasonic computerized tomography, etc), etc.
ACKNOWLEDGMENT
The authors are grat eful to the Peopl e’s Hospital of Shaan xi Province, the Affiliated Hospital of Fourth Military
Medical University, the Secon d Affiliated Hospital of Xi’an University of Medical Sciences, the Fourth P eople’ s
Hospital of Xi’an City an d Xi’an Institute of Chinese Medicine, etc. who provi ded clinical experimental conditions
(including the ultrasonic diagnosis apparat us (made in China or enter port from abroad), varied ultrasonic therapy
machines, a host of cases of illness, etc), analysis of the results for medical ultrasonic di agnosis transducers an d
medical ultrasonic therapy transducer, and assist some Chinese traditional and herbal drugs of ultrasonic therapy to
our work.
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