Rev. Bras. Fisiot. Vol. 2, No. I (1997)
©Associação Brasileira de Fisioterapia
35
Calibration of Acoustic Intensity of Therapeutic
Ultrasound Equipment in use in the City o f Piracicaba*
1
1
1
R. Guirro , F. Serrão , D. Elias e A.J. Bucalon
2
1
2
Departamento de Fisioterapia, UNIMEP, Piracicaba - SP, Brasil
Departamento de Bioquímica e Microbiologia Aplicada, UNESP, Rio Claro- SP, Brasil
Received: 31.03.97; Accepted: 12.05.97
Resumo. A intensidade acústica temporal e espacial (SATA) dos equipamentos de ultra-som terapêutico
(UST) deve ser monitorada periodicamente. Com o objetivo de avaliar as condições dos equipamentos de UST em uso na
cidade de Piracicaba-SP foram analisados 31 equipamentos nos regimes de pulso contínuo e pulsado com frequência de
1 MHz. As intensidades 0.1, 0.2, 0.5, 0.8, 1.0, 1.5, 2.0, 2.5 e 3.0 W cm- 2, indicadas no painel do equipamento, foram
analisadas, utilizando-se para isso uma balança de pressão de radiação modelo UPM-DT-1, previamente aferida. Os
resultados quanto à intensidade acústica (I) foram expressos a partir do método estatístico descritivo, através dos quartis
2
superior (QS) e inferior (QI), para transdutores com superfície metálica de 9 cm . Os resultados encontrados nos quartis
superior e inferior, no regime contínuo foram respectivamente: lo. I= -20.0% e -96.2%, Io.2 = -3.1% e -83.7%, Io.s = -35.0%
e -86.5%, Io.s = -37.5% e -71.0%, I1.o = -21.5% e -61.0%, I 1.5 = -34.2% e -63.4%, Iz.o = -46.2% e -67.0%, lz.s = -49.0% e
-69.5%, 13.0 = -58.1% e -77.6%. Para o regime pulsado, as intensidades encontradas foram: Io.J = -40.0% e -86.2%,
Io.2 = -46.9% e -77.5%, Io.s = -56.5% e -80.5%, Io.s = -59.4% e -76.9%, l1.o = -50.0% e -86.5%, l1.s = -62.5% e -82.5%,
Iz.o = -62.5% e -81.6%, Iz.s = -64.7% e -88.8% e h o= -87.1% e -94.8%. Em resposta a um questionário, a totalidade dos
usuários não havia realizado aferições anteriores, sendo a faixa de 58 a 68 meses a de maior concentração quanto ao tempo
de compra. Dessa forma, esse trabalho demonstra a grande discrepância entre a intensidade indicada no painel do
equipamento e a emitida pelo transdutor, ressaltando assim a necessidade de avaliações periódicas do equipamento de UST.
Palavras-chave: ultra-som terapêutico, balança de força de radiação, dosimetria e intensidade
Abstract. Temporal arid Spatial accoustic intensity (SAT A) o f therapeutic ultrasound equipment (UST)
should be monitored periodically. With the object of evaluating the conditions of UST equipment in use in the city of
Piracicaba-SP, 31 items of equipment, were analysed under continua! pulse and pulsed conditions ata frequency of 1 MHz.
2
Intensities of 0.1, 0.2, 0.5, 0.8, 1.0, 1.5, 2.0, 2.5 and 3.0 W cm- , indicated on the equipment pane!, were analysed, by means
of using a previously calibrated digital radiation pressure scale model UPM-DT-1. The acoustic intensity (I) results were
expressed by the descriptive statistical method, by means of superior and inferior quartics (QS) and (QI) respectively, to
2
transducers with metal surfaces of 9 cm . The results found in the superior and inferior quartics respectively, under
continuous conditions were: lo. I = -20.0% and -96%, Io.2 = -3.1% and -83.7%, Io.s = -35.0% and -86.5%, Io.s = -37.5% and
71.0%, I1.o= -21.5% and -61%, I 1.5= -34.2% and -63.4%, Iz.o= -46.2% and -67.0%, Iz.s = -49.0% and -69.5%, h o= -58.1%
and -77.6%. For pulsed conditions, the intensities found were: Io.J = -40.0% and -86.2%, Io.2 = -46.9% and -77.5%,
Io.s = -56.5% and -80.5%, Io.s = -59.4% and -76.9%, I1.o= -50.0% and -86.5%, I1.5 -62.5% and -82.5%, Iz.o = -62.5% and
-81.6%, lz.s = -64.7% and -88.8%, ho = -87.1% and-94.8%. In reply to the use, ali the users had not carried our previous
calibrations, and the greatest concentration with regard to the time since bought was in the range of 58-68 months. This
paper therefore, shows the great discrepancy between the intensity indicated on the equipment pane! and that emitted by
the transducer, thus highlighting the necessity for period evaluations of UST equipment.
Keywords: therapeutic ultrasound, radiation force balance, dosimetry and power
=
Introduction
1
The American Standards Association (ASA) in their
publication Z24.18-1956 recommends a variation of±l5% for
an effective acoustic output power. Pye and Milford 2 report that
the Intemational Electronic Commission 3 (IEC 601-2-5, 1984)
1
postulates that accousti,c output power fluctuate ±30% from the
values indicated on the equipment panel.
Literature demonstrates a disturbing picture with regard
to the dosimetry of UST equipment, in which there are various
24 5 67
publications · • · · •8.
Universidade Metodista de Piracicaba- UNIMEP- Departamento de Fisioterapia, Rodovia do Açucar, Km 156, Bairro Taquaral, 13.400-901 Piracicaba, SP
1996.
* Artigo aceito para publicação na Physiotherapy, in press,
Rev_ Bras_ Fisiot.
Guirro et a/.
36
In the face of the unanimity of authors who report inoperative UST equipment with regard to their intensity, this paper
proposed to calibrate the temporal and spatial acoustic intensity
(SATA) of UST equipment in use in the city of Piracicaba, as
well as to make a survey of the conditions of their use.
Methodology
UST equipment was collected in the city of Piracicaba, SP,
where it was possible to recruit 31 items of equipment in use,
with all national makes being represented. The present experiment adopted the methods of the force of radiation for measuring the power of ultrasonic radiation, using a digital scale Model
UPM-DT-1. The radiation pressure scale was previously calibrated.
Calibration was carried out under continuai pulse and
pulsed conditions, ata frequency of 1.0 Mega Hertz (MHz) with
transducers having a metal surface of 9 cm 2 , at intensities
indicated on the panel of 0.1; 0.2; 0.5; 0.8; 1.0; 1.5; 2.0; 2.5 and
3.0 W cm- 2• An effective radiation area (ERA) of 4 cm 2 was
adopted after consulting the manufacturers. The results obtained
were analysed by means of the descriptive statistical method,
where it was possible to determine the quartics and from these,
construct the box plot.
Concommitently with the calibration, users were asked to
fill out a questionnaire.
IO
o
00
00 00
000 000
000 0000
o 000 00000
o
o
OL_--~~~~~~----~----~---------0.1
1.0
0.5
2.0
1.5
2.5
3.0
5
Most used intensity (W em')
Figure 2. Representative figure ofintensities most used by users during therapy.
.
lO
o
o o
o o
o o
o o o
o o o o o
5
o o
o o o o
o o o 000
o 100 200
o
o
o
o
o
o
300
400
500
600
Weekly time of use (min)
o
700
•
800
Figure 3. Representative figure of weekly time of use_
1o·
Results
The values presented with a negative sign indicate a
decrease in the intensity emitted in relation the the intensity
indicated on the equipment panel, Fig. 1.
With reference to the questionnaire, the results is expose
in Figs. 2, 3 e 4.
lO
o
o
O
o o
o o
o o
o
00
00
000
000000000000 000
10 20
30 40
50
60
o
L __ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ _ _
o
70
80
Time elapsed since purchase (months)
90
100
Figure 4. Representative figure of Time since Purchase of Equipment.
o
-I o
-20
-30
"'
"'
o
.....o -40
-50
~
-60
-70
-80
-90
-I 00
5
Conclusion
0.1 0.2 0.5 0.8 1.0 1.5 2.0 2.5 3.0
Intensities indicated on the equipament pane! (W cm- 2)
lll Continuai
[J Pulsed
Figure 1. Representative figure of intervals of loss of ultrasonic radiation
demonstrated by means of the superior and inferior quartics values, for the
different intensities indicated on the equipment pane! under both types of pulse
conditions.
During the time that equipment was being asked for and
the questionnaire being presented to users, a totallack of information was observed, conceming the need for routinely conducted metrological procedures.
The results found in UST equipment in use in the city of
Piracicaba, perrnits the conclusion that all of these were found
to be out of the technical specifications proposed by IEC 6012-5 (1984), with the exception of some equipment, at certain
intensities, which were shown to be within the acceptable limits.
Acknowledgments
We would like to thank Fundo de Apoio a Pesquisa (FAPUNIMEP), PIBIQ/CNPq Program; Statistic teacher MSc M.I.F.
Alves; Department of Bioengineering of the Escola de Engenharia
de São Carlos-Universidade de São Paulo and Dr. O Silva.
Vol. 2. No. I, 1997
Calibration of Acoustic Intensity ofTherapeutic Ultrasound Equipment
References
1. American Standard Specification for Ultrasonic
Therapeutic Equipment, New York, American National lnstitute, Sz4.18 , January 18, 1956
2. Pye, D.S. and Milford, C.; The performance of ultrasound physiotherapy machines in Lothian region,
Scotland, 1992. Ultrasound in Medicine and Biology,20,347-359, 1994.
3. Intemation Electrotechical Commission (IEC). Particular Requirements for the Safety of Ultrasonic
Therapy Equipment, Publication 601- 2-5. Geneva,
1984.
4. Fyfe, M.C. and Pamell, S.M.; The importance of mensurement of effective transdutor radiating area in the
5.
6.
7.
8.
37
testing and calibration oftherapeutic ultrasonic instmments. Health Physics, 43, 377-381, 1982.
Lloyd, J.J. and Evans, J.A.; A calibration survey of
physiotherapy ultrasound equipment in north wales.
Physiotherapy, 74, 56-61, 1988.
Starritt, H.C. and Duck, F.A. ( 1992). A comparison of
ultrasound exposure in therapy and pulsed Doppler
fields. British Journal of Radiology, 65, 557-563,
1992.
Hekkenberg, R.T., Reibold, R., Zepiri, B.; Evaluation
ofultrasound therapy devices. Physioterapy, 72, 390395, 1986.
Cunningham-Hill, C.J. and Pelmore, J.M.; Evaluation
of the dorchester ultrasound power meter. Physiotherapy, 78, 569-570, 1992.