- Email: [email protected]
Evaluation of the acoustic intensity of new ultrasound therapy equipment
Ultrasonics 39 (2002) 553–557 www.elsevier.com/locate/ultras
Evaluation of the acoustic intensity of new ultrasound therapy equipment Rinaldo Guirro *, Sandra C. Britshcy Dos Santos Department of Physiotherapy, Universidade Metodista de Piracicaba (Piracicaba Methodist University), UNIMEP, Rodovia do Acßucar Km 156, Bairro Taquaral, Piracicaba SP 13.400-901, Brazil Received 20 July 1999; received in revised form 10 January 2001; accepted 12 December 2001
Abstract International safety standards recommend a limit below 30% variation in acoustic intensity for ultrasound therapy (UST) equipment. In view of this question, the purpose of this work was to evaluate the intensity of new UST equipment in the Brazilian market. An evaluation was performed of eight models manufactured by six different national manufacturers; under continuous and pulsed conditions, at frequencies of 1.0–3.0 MHz, for a total of 48 items of equipment. The intensities were analysed according to the technical standards IEC 601-2-5, in the range 0.01–3.0 W cm2 , using a radiation pressure scale UPM-DT-10 (Ohmic Instruments), previously calibrated. The results demonstrated that the models Sonacel, Sonacel plus, Sonacel III, Avatar I, and Sonamed I, although they were new (unused) presented calibration errors of over 30% in more than one intensity checked, and the models SONOPULSE, PRO-SEVEN and SONOMASTER ST. are within the standards proposed. The results show that industry must improve quality control on their production lines, as well as that there is a need for a supervising body at national level. Ó 2002 Published by Elsevier Science B.V. Keywords: Ultrasound; Dosimetery; Acoustic intensity
1. Introduction The action of therapeutic ultrasound on biological tissues depends largely on the intensity used, which often has calibration errors capable of promoting inefficiency in the treatment or even new lesions. The explanation for existence of this problem is not the metrology procedures that enable this equipment to be checked [1,2]. It occurs as a result of two factors: the non-existence of a metrology culture among users and the restricted number of items of measuring equipment available, these being found in research centres or manufacturing industries [3]. Surveys published with regard to therapeutic equipment performance [3–5] show very similar results, with few of the apparatus analysed having intensity gauge errors below 20–30%. In view of this question, this work evaluated the acoustic intensity of new ultrasound therapy (UST) *
Corresponding author. Tel.: +55-19-4221515x323/401.
equipment, seeking out the different makes and models existent on the Brazilian national market.
2. Material and methods Analyses were made of 48 items of new (unused) equipment manufactured by six companies distributed over eight models. The therapeutic ultrasound equipment used in this work came from distributors or representatives of manufacturers who showed interest in checking the quality of the equipment they sold. The equipment was not requested directly from the manufacturing companies in order not to run the risk that it would be subjected to a thorough quality control, a fact that would not reflect the reality of such equipment. Data was collected during the period from May to October 1997. Intensity values were predetermined in accordance with each model, thus providing a wide range (0.01–3.0 W cm2 ). The measurement of acoustic energy followed
0041-624X/02/$ - see front matter Ó 2002 Published by Elsevier Science B.V. PII: S 0 0 4 1 - 6 2 4 X ( 0 2 ) 0 0 2 5 1 - 2
554
R. Guirro, S.C. Britshcy Dos Santos / Ultrasonics 39 (2002) 553–557
the standards of the international Electrotechnical Commission [6,7], in the publications 601-2-5 and 1689. In performing the experiment, the force of radiation method that measures the total ultrasonic radiation power was adopted. With this method, it should be borne in mind that exact measurements are only possible if effected under free acoustic field conditions. A digital balance was used, model UPM-DT-1 (Ohmic Instruments Co.), with the possibility of measuring between 10 mW to 30 W, previously calibrated. It was placed on an immobile bench, which had a shock absorbing system to avoid reading errors arising from vibrations external to the system, as well as isolation from air currents, which could also cause reading errors. To obtain intensity, three consecutive measurements of the output power were taken, and then the average was obtained. The output intensity calculation was made by dividing the average of the radiation power by the effective radiation area, according to the manufacturers instructions. Measurements were always taken by the same experimenter. Both the continuous and pulsed conditions were analysed. Statistical evaluation of the data was done by means of formulating the independent averages with the respective standard deviations, in accordance with the make and model of the equipment.
3. Results The results show that the performance of some of the equipment, even though it was unused, fell outside of the specifications. Tables 1–3 show the results of checking the 48 items of UST equipment. The minus
signs () and the plus signs (þ) respectively indicate emission below and above that expected. As may be seen in Table 1, the model Sonomed I showed variation of above 30% at all of the intensities checked. Note that for the intensity of 0.2 W cm2 , the intensity emitted was of 30% up to þ60% of the value selected, therefore showing a variation of 90% between the minimum and maximum values. This discrepancy between the value selected on the panel and the value effectively emitted by the equipment may be seen with greater emphasis in Table 3, with regard to the evaluation under pulsed conditions. The models Sonacel, Sonacel plus, Avatar I, when evaluated under continuous conditions (Table 1), show a variation of the above 30%. With regard to the analysis under pulsed conditions (Table 2), in addition to the previously cited models, the model Sonacel III was also shown to be outside of the specifications. A model that deserves attention is the Avatar I. This item of equipment only emitted ultrasonic power at the intensities above 0.5 W cm2 , both in the continuous and pulsed mode, and in some of instances, the quantity of ultrasonic power emitted showed decreases of over 50%. The items of equipment that showed variations of below 30% in intensity emitted and, therefore, within the parameters of normality, are the models Sonopulse, Pr oseven and Sonomaster St., under continuous conditions (Table 1), with exception at the intensity of 2.0 and 3.0 W cm2 for the Sonomaster St. In the pulsed mode only the models Sonopulse and Pr o-seven are within the limits, with each of the models having exceptions at the intensities of 0.04 and 0.03 W cm2 respectively (Table 2).
Table 1 Data referring to the variations in percentage of the intensities checked for the different models of therapeutic ultrasound equipment, under continuous conditions Models
Intensities selected on panel 0.20
Sonacel Sonacel plus Sonacel III
0.25
Sonopulse Sonomed I Pro-seven
0.80
1.0
1.5
2.0
7% þ58% 67% 4% 8% þ42%
6% þ38% 58% þ10% þ2% þ52% 61% 1% 13% þ19% 14% 12% 44% 16% 14% 12%
12% þ10% 41% þ20% þ4% þ42% 57% þ3% 15% 10% 14% 11% 4% 36% 24% 8%
17% þ1% 35% þ18% 8% þ27%
76% 26%
Avatar I Sonomaster Standart
0.75
þ35% þ195% 15% 5% 4% þ4%
25% 5% 20% 10% 30% þ60%
14% 28% 13% 10% 39% 4% 28% 12%
23% 4%
The minus sign () indicates decrease, while the plus sign (þ) indicates increase.
33% 14% 13% 7% 61% 45% 26% 7%
3.0
44% 21%
60% 72%
R. Guirro, S.C. Britshcy Dos Santos / Ultrasonics 39 (2002) 553–557
555
Table 2 Data referring to the variations in percentage of the intensities checked for the different models of therapeutic ultrasound equipment under pulsed conditions Intensities selected on panel
Models
0.03 Sonacel Sonacel Plus Sonacel III
0.04
0.08
þ75% þ225% 75% 25% 25% 68%
þ37% þ137% 62.5% 25% 88% þ237%
0.10
0.16
0.20
0.30
0.40
þ12% þ50% 63% 25% 88% þ150%
þ5% þ25% 55% 5% 70% þ140% 55% 15% 20%
14% 0% 37% þ30% 47% þ106% 47% 0% 40%
33% 13% 28% þ42% 40% þ65%
39%
0% 15% 5% 20% 10%
20% 4% þ3% 27% 7%
37% 13% þ7% 23% 8%
70% 50%
Avatar I Sonomaster Standart Sonopulse
13%
0%
þ12% 38% 25%
75%
13%
44% 24%
Pro-seven
þ12% 10% 4%
15% 5% 28% 2%
The minus sign () indicates decrease, while the plus sign (þ) indicates increase.
Table 3 Data referring to the variations in percentage of the intensities checked for the model of therapeutic ultrasound equipment Sonamed I, under pulsed conditions Models Sonomed I
Intensities selected on panel 0.2
0.5
0.8
1.0
1.50
2.5
85% 65%
70% 54%
65% 30%
49% 48%
54% 50%
69% 58%
The minus sign () indicates decrease, while the plus sign (þ) indicates increase.
4. Discussion Application in various areas of knowledge is increasingly being found for the radiation produced by ultrasound transducers. In certain cases it is necessary for the powers applied to be safely known, mainly in the medical area where it is widely used in diagnoses, therapy or in surgical procedures [8]. Ultrasound is among the physical resources most used by physiotheraphy professionals for the treatment of lesions to the muscular–skeletal system. Its action on the tissues largely depends on the intensity employed, which frequently has calibration errors, and may even cause new lesions [9,10]. Thus, the equipment must be periodically checked to ensure that the safety standards are correct. The main problem encountered is in not adopting a metrology culture for due checking of these items of equipment. This occurs as a result of three factors: (1) because there is no metrology culture among users, (2) due to the restricted number of items of measuring equipment available and (3) because, up to now, there is
no standardisation at national level regulating such procedures [11]. In this context Zeqiri [12] emphasises that one of the factors is a lack of consciousness and training of the physiotherapist. He also states that generally physiotherapists have a key role to perform in assuring that the equipment bought from manufacturers is calibrated in accordance with international standards and specifications for this purpose. Various international safety standards establish an upper limit for ultrasonic power emitted, with a view to protecting the patient from unfavourable biological effects. The World Health Organisation, limited intensity to a maximum of 3.0 W cm2 , for both types of wave. However, a safety aspect that is not considered in these limits is the occurrence of high instantaneous spatial intensities within the beam, that may lead to tissue damage, and should, therefore, be avoided. International Electrotechnical Commission Document, IEC 601-2-5 [7], published the particular checking standards required for the safety of ultrasound, where the output acoustic power, the effective intensity and the maximum temporal intensity should not vary by more than 30% of the values indicated on the panel of the equipment. An American Standard Association, ASA Z24.18 [13] states that the ultrasound power should be maintained within the limit of 15%, and the maximum instantaneous intensity at 20%. Many researchers have analysed the acoustic intensity emitted from the UST transducers and found the need for more rigid control in the production process, as well as for periodic checks [2,4,10,14,15]. All of these surveys published with regard to the performance of UST equipment show very similar results, in which very few
556
R. Guirro, S.C. Britshcy Dos Santos / Ultrasonics 39 (2002) 553–557
of the items of equipment analysed have intensity gauges with errors of below 20–30%. The authors agree with this and recommend that UST users should receive information with respect to calibration and the importance thereof, and furthermore, that they should consider the possibility of adopting a standard of calibration for their equipment. These measures would greatly increase the possibility of guaranteeing that ultrasonic therapy is safely and effectively produced. The results obtained through the above mentioned research are similar to that found in this paper, even though the items of equipment tested in this research are unused, that is to say, new. The implementation of standards for the production process and later control of the acoustic intensity emitted by items of UST equipment is occurring slowly on the Brazilian market. In its first publication––Diario Ofical da Uni~ ao 12-03-96 [16] the Secretary for Health Control makes a general statement with regard to the definitions of the terms and deadlines for the implementation of some of the stages. It is noted that after more than 24 months have passed, there has still been no completely implemented standardisation. The Brazilian Government intends following the technical standards proposed by IEC 601-2-5 [6], with regard to therapeutic ultrasound. Detailing of the procedures will follow the publication 1689 of 1996. According to Parizotto [17], the Ministry of Health ruling no. 2.043 of 12 December, 1994 updated by ruling no. 155 of 27 February, 1997, calls for there to be a demand that industries manufacturing electro-medical equipment should have certification from accredited laboratories. The companies will become responsible for the quality of the products placed on the market as stipulated in articles 4–25 of the ‘‘C odigo de Defesa do Consumidor’’ (Consumer Defence Code) (Law No. 8.078 of 11 September, 1990). The author concludes that professionals ought to work only with reliable and safe equipment, periodically evaluate the working conditions of these apparatuses and submit them to maintenance, apart from acquiring only equipment with adequate certification. In this context, it is suggested that some companies should implement a more rigid quality control, as well as an updating of their own equipment. It may be observed that analogue equipment presents a variation of intensity higher than digital equipment, thus confirming the necessity of updating the project. A point favouring good calibration is that in physiotherapy departments where patients are treated by equipment that exhibits alterations in acoustic intensity, the results of the treatment may be unsatisfactory. Furthermore, every scientific research that envisages the use of ultrasonic energy only becomes reliable when checking is performed, and if necessary, calibration is carried out prior to experimental tests.
Another alarming point is that there is no assistance from an inspecting body with regard to new or used equipment, since the literature points to the loss of energy emitted when the equipment is used. This great discrepancy between the selected acoustic energy and that emitted may be responsible for the non-reproducibility of the results of clinical practice or in experimental research. According to Cunningham [18] some equipment tested showed 100% error in output intensity. The author comments on a recommendation by Pye [19], in which the author suggests a specific certificate of calibration for ultrasound equipment. The imprecision of ultrasound equipment makes the information in literature irrelevant. There is no guaranteeing that the response to the treatment is due to ultrasound, to the natural evolution of the lesion or even to a placebo. Another relevant point is the fact that the professional receives payment for service, in this case the application of ultrasound, and is not really performing the service due to the equipment not being calibrated. In this context Parizzoto [17] puts forward a reflection, in which he questions whether if the patient was sufficiently informed to opt for or against the performance of a certain examination or treatment and if they knew what type of situation to which they would be submitted, would they consent to having it performed?
5. Conclusions The UST equipment models Sonamed I, Sonacel, Sonacel plus, Sonacel III and Avatar I, although new, presented calibration errors of above 30% when compared with the intensity of the panel, both under continuous and pulsed conditions. The models Sonomaster St., Pr o-seven and Sonopluse were within the specifications proposed by the IEC-601/ 84. There is need for greater quality control on the part of the industries manufacturing therapeutic ultrasound. The companies that sell this equipment should demand from the manufacturers, an improvement in design as well as better quality control. There is urgent need for a supervising body that controls the quality of equipment produced on the national market. Professionals should join forces to demand better quality equipment, as they invest in the purchase thereof and sell a service to the patient, which frequently is not being performed correctly.
Acknowledgements ‘‘Femandes Fisioterapai’’ and ‘‘Skin Distribuidora de Equipment’’ (Skin Equipment Distributors).
R. Guirro, S.C. Britshcy Dos Santos / Ultrasonics 39 (2002) 553–557
References [1] P.N. Burns, T. Mcdiarmid, Clinical applications of therapeutic ultrasound, Physiotherapy 73 (1987) 155–162. [2] H.F. Stewart et al., Survey of use and performance of ultrasonic therapy equipment in pinellas county, Florida, Physical Therapy 54 (1974) 707–715. [3] R. Guirro, F. Serr~ ao, D. Elais, A.J. Bucalon, Calibration of therapeutic ultrasound equipment, Physiotherapy 83 (1997) 419–422. [4] M.C. Fyfe, S.M. Parnell, The importance of measurement of effective transducer radiating area in the testing and calibration of ‘‘therapeutic’’ ultrasonic instruments, Health Physics 43 (1982) 377–381. [5] R.T. Hekkenberg, R. Reibold, B. Zeqiri, Evaluation of ultrasound therapy devices, Physiotherapy 72 (1986) 390–395. [6] International Electrotechnical Commission Publication 601-2-5, Particular Requirements for the Safety of Ultrasonic Therapy Equipment, IEC, Geneve, Suisse, 1984. [7] International Electrotechnical Commission Publication 601-2-5, Ultrasonics-Physiotherapy systems––Performance Requirements and Methods of Measurement in the Frequency Range 0.5–5.0 MHz, IEC, Geneve, Suisse, 1996. [8] A.J. Bucalon, I.L. Batista, Forcßa de radiacß~ao ac ustica e sua medida, Trabalho de iniciacß~ao cientifica, Departamento de Fisica, Unesp-Rio Claro, 1993. [9] K. Hildersley, A simple calorimeter for monitoring the output power of ultrasound therapy machines, Physiotherapy 80 (1994) 219–223.
557
[10] S.D. Pye, C. Milford, The performance of ultrasound physiotherapy machines in Lothian, Scotland, 1992, Ultrasound in Medicine and Biology 20 (1994) 347–359. [11] R. Guirro, S.C.B. Santos, A Realidade da pot^encia ac ustica emitida pelos equipamentos de ultra-som terap^eutico: Uma Revis~ao, Revista de Fisioterapia da Universidade de S~ao Paulo 4 (1997) 76–82. [12] B. Zeqiri, Calibration and safety of physiotherapy ultrasound equipment, Physiotherapy 83 (1997) 559–560. [13] American Standard Specification for Ultrasonic Therapeutic Equipment, American National Standards Institute, New York, January 18, 1956, p. Z24.18. [14] M.H. Repacholi, D.A. Benwell, Using surveys of ultrasound therapy devices to draft performance standards, Health Physics 36 (1979) 679–686. [15] J.J. Lloyde, J.A. Evans, A calibration survey of physiotherapy ultrasound equipment in North Wales, Physiotherapy 74 (1988) 56–61. [16] Diario Oficial da Uni~ao––secretaria de Vigil^ancia Sanit aria––Portaria conjunta No. 1, de 8 de marcßo. tica na eletroterapia––Editorial, Revista Brasileria [17] N. Parizotto, E de Fisioterapia 2 (1998). [18] S.J. Cunningham, Calibration chaos makes research irrelevant, Physiotherapy 83 (1997) 440–441. [19] S.D. Pye, Ultrasound therapy equipment: Does it perform?, Physiotherapy 82 (1996) 36–44.
Evaluation of the acoustic intensity of new ultrasound therapy equipment Rinaldo Guirro *, Sandra C. Britshcy Dos Santos Department of Physiotherapy, Universidade Metodista de Piracicaba (Piracicaba Methodist University), UNIMEP, Rodovia do Acßucar Km 156, Bairro Taquaral, Piracicaba SP 13.400-901, Brazil Received 20 July 1999; received in revised form 10 January 2001; accepted 12 December 2001
Abstract International safety standards recommend a limit below 30% variation in acoustic intensity for ultrasound therapy (UST) equipment. In view of this question, the purpose of this work was to evaluate the intensity of new UST equipment in the Brazilian market. An evaluation was performed of eight models manufactured by six different national manufacturers; under continuous and pulsed conditions, at frequencies of 1.0–3.0 MHz, for a total of 48 items of equipment. The intensities were analysed according to the technical standards IEC 601-2-5, in the range 0.01–3.0 W cm2 , using a radiation pressure scale UPM-DT-10 (Ohmic Instruments), previously calibrated. The results demonstrated that the models Sonacel, Sonacel plus, Sonacel III, Avatar I, and Sonamed I, although they were new (unused) presented calibration errors of over 30% in more than one intensity checked, and the models SONOPULSE, PRO-SEVEN and SONOMASTER ST. are within the standards proposed. The results show that industry must improve quality control on their production lines, as well as that there is a need for a supervising body at national level. Ó 2002 Published by Elsevier Science B.V. Keywords: Ultrasound; Dosimetery; Acoustic intensity
1. Introduction The action of therapeutic ultrasound on biological tissues depends largely on the intensity used, which often has calibration errors capable of promoting inefficiency in the treatment or even new lesions. The explanation for existence of this problem is not the metrology procedures that enable this equipment to be checked [1,2]. It occurs as a result of two factors: the non-existence of a metrology culture among users and the restricted number of items of measuring equipment available, these being found in research centres or manufacturing industries [3]. Surveys published with regard to therapeutic equipment performance [3–5] show very similar results, with few of the apparatus analysed having intensity gauge errors below 20–30%. In view of this question, this work evaluated the acoustic intensity of new ultrasound therapy (UST) *
Corresponding author. Tel.: +55-19-4221515x323/401.
equipment, seeking out the different makes and models existent on the Brazilian national market.
2. Material and methods Analyses were made of 48 items of new (unused) equipment manufactured by six companies distributed over eight models. The therapeutic ultrasound equipment used in this work came from distributors or representatives of manufacturers who showed interest in checking the quality of the equipment they sold. The equipment was not requested directly from the manufacturing companies in order not to run the risk that it would be subjected to a thorough quality control, a fact that would not reflect the reality of such equipment. Data was collected during the period from May to October 1997. Intensity values were predetermined in accordance with each model, thus providing a wide range (0.01–3.0 W cm2 ). The measurement of acoustic energy followed
0041-624X/02/$ - see front matter Ó 2002 Published by Elsevier Science B.V. PII: S 0 0 4 1 - 6 2 4 X ( 0 2 ) 0 0 2 5 1 - 2
554
R. Guirro, S.C. Britshcy Dos Santos / Ultrasonics 39 (2002) 553–557
the standards of the international Electrotechnical Commission [6,7], in the publications 601-2-5 and 1689. In performing the experiment, the force of radiation method that measures the total ultrasonic radiation power was adopted. With this method, it should be borne in mind that exact measurements are only possible if effected under free acoustic field conditions. A digital balance was used, model UPM-DT-1 (Ohmic Instruments Co.), with the possibility of measuring between 10 mW to 30 W, previously calibrated. It was placed on an immobile bench, which had a shock absorbing system to avoid reading errors arising from vibrations external to the system, as well as isolation from air currents, which could also cause reading errors. To obtain intensity, three consecutive measurements of the output power were taken, and then the average was obtained. The output intensity calculation was made by dividing the average of the radiation power by the effective radiation area, according to the manufacturers instructions. Measurements were always taken by the same experimenter. Both the continuous and pulsed conditions were analysed. Statistical evaluation of the data was done by means of formulating the independent averages with the respective standard deviations, in accordance with the make and model of the equipment.
3. Results The results show that the performance of some of the equipment, even though it was unused, fell outside of the specifications. Tables 1–3 show the results of checking the 48 items of UST equipment. The minus
signs () and the plus signs (þ) respectively indicate emission below and above that expected. As may be seen in Table 1, the model Sonomed I showed variation of above 30% at all of the intensities checked. Note that for the intensity of 0.2 W cm2 , the intensity emitted was of 30% up to þ60% of the value selected, therefore showing a variation of 90% between the minimum and maximum values. This discrepancy between the value selected on the panel and the value effectively emitted by the equipment may be seen with greater emphasis in Table 3, with regard to the evaluation under pulsed conditions. The models Sonacel, Sonacel plus, Avatar I, when evaluated under continuous conditions (Table 1), show a variation of the above 30%. With regard to the analysis under pulsed conditions (Table 2), in addition to the previously cited models, the model Sonacel III was also shown to be outside of the specifications. A model that deserves attention is the Avatar I. This item of equipment only emitted ultrasonic power at the intensities above 0.5 W cm2 , both in the continuous and pulsed mode, and in some of instances, the quantity of ultrasonic power emitted showed decreases of over 50%. The items of equipment that showed variations of below 30% in intensity emitted and, therefore, within the parameters of normality, are the models Sonopulse, Pr oseven and Sonomaster St., under continuous conditions (Table 1), with exception at the intensity of 2.0 and 3.0 W cm2 for the Sonomaster St. In the pulsed mode only the models Sonopulse and Pr o-seven are within the limits, with each of the models having exceptions at the intensities of 0.04 and 0.03 W cm2 respectively (Table 2).
Table 1 Data referring to the variations in percentage of the intensities checked for the different models of therapeutic ultrasound equipment, under continuous conditions Models
Intensities selected on panel 0.20
Sonacel Sonacel plus Sonacel III
0.25
Sonopulse Sonomed I Pro-seven
0.80
1.0
1.5
2.0
7% þ58% 67% 4% 8% þ42%
6% þ38% 58% þ10% þ2% þ52% 61% 1% 13% þ19% 14% 12% 44% 16% 14% 12%
12% þ10% 41% þ20% þ4% þ42% 57% þ3% 15% 10% 14% 11% 4% 36% 24% 8%
17% þ1% 35% þ18% 8% þ27%
76% 26%
Avatar I Sonomaster Standart
0.75
þ35% þ195% 15% 5% 4% þ4%
25% 5% 20% 10% 30% þ60%
14% 28% 13% 10% 39% 4% 28% 12%
23% 4%
The minus sign () indicates decrease, while the plus sign (þ) indicates increase.
33% 14% 13% 7% 61% 45% 26% 7%
3.0
44% 21%
60% 72%
R. Guirro, S.C. Britshcy Dos Santos / Ultrasonics 39 (2002) 553–557
555
Table 2 Data referring to the variations in percentage of the intensities checked for the different models of therapeutic ultrasound equipment under pulsed conditions Intensities selected on panel
Models
0.03 Sonacel Sonacel Plus Sonacel III
0.04
0.08
þ75% þ225% 75% 25% 25% 68%
þ37% þ137% 62.5% 25% 88% þ237%
0.10
0.16
0.20
0.30
0.40
þ12% þ50% 63% 25% 88% þ150%
þ5% þ25% 55% 5% 70% þ140% 55% 15% 20%
14% 0% 37% þ30% 47% þ106% 47% 0% 40%
33% 13% 28% þ42% 40% þ65%
39%
0% 15% 5% 20% 10%
20% 4% þ3% 27% 7%
37% 13% þ7% 23% 8%
70% 50%
Avatar I Sonomaster Standart Sonopulse
13%
0%
þ12% 38% 25%
75%
13%
44% 24%
Pro-seven
þ12% 10% 4%
15% 5% 28% 2%
The minus sign () indicates decrease, while the plus sign (þ) indicates increase.
Table 3 Data referring to the variations in percentage of the intensities checked for the model of therapeutic ultrasound equipment Sonamed I, under pulsed conditions Models Sonomed I
Intensities selected on panel 0.2
0.5
0.8
1.0
1.50
2.5
85% 65%
70% 54%
65% 30%
49% 48%
54% 50%
69% 58%
The minus sign () indicates decrease, while the plus sign (þ) indicates increase.
4. Discussion Application in various areas of knowledge is increasingly being found for the radiation produced by ultrasound transducers. In certain cases it is necessary for the powers applied to be safely known, mainly in the medical area where it is widely used in diagnoses, therapy or in surgical procedures [8]. Ultrasound is among the physical resources most used by physiotheraphy professionals for the treatment of lesions to the muscular–skeletal system. Its action on the tissues largely depends on the intensity employed, which frequently has calibration errors, and may even cause new lesions [9,10]. Thus, the equipment must be periodically checked to ensure that the safety standards are correct. The main problem encountered is in not adopting a metrology culture for due checking of these items of equipment. This occurs as a result of three factors: (1) because there is no metrology culture among users, (2) due to the restricted number of items of measuring equipment available and (3) because, up to now, there is
no standardisation at national level regulating such procedures [11]. In this context Zeqiri [12] emphasises that one of the factors is a lack of consciousness and training of the physiotherapist. He also states that generally physiotherapists have a key role to perform in assuring that the equipment bought from manufacturers is calibrated in accordance with international standards and specifications for this purpose. Various international safety standards establish an upper limit for ultrasonic power emitted, with a view to protecting the patient from unfavourable biological effects. The World Health Organisation, limited intensity to a maximum of 3.0 W cm2 , for both types of wave. However, a safety aspect that is not considered in these limits is the occurrence of high instantaneous spatial intensities within the beam, that may lead to tissue damage, and should, therefore, be avoided. International Electrotechnical Commission Document, IEC 601-2-5 [7], published the particular checking standards required for the safety of ultrasound, where the output acoustic power, the effective intensity and the maximum temporal intensity should not vary by more than 30% of the values indicated on the panel of the equipment. An American Standard Association, ASA Z24.18 [13] states that the ultrasound power should be maintained within the limit of 15%, and the maximum instantaneous intensity at 20%. Many researchers have analysed the acoustic intensity emitted from the UST transducers and found the need for more rigid control in the production process, as well as for periodic checks [2,4,10,14,15]. All of these surveys published with regard to the performance of UST equipment show very similar results, in which very few
556
R. Guirro, S.C. Britshcy Dos Santos / Ultrasonics 39 (2002) 553–557
of the items of equipment analysed have intensity gauges with errors of below 20–30%. The authors agree with this and recommend that UST users should receive information with respect to calibration and the importance thereof, and furthermore, that they should consider the possibility of adopting a standard of calibration for their equipment. These measures would greatly increase the possibility of guaranteeing that ultrasonic therapy is safely and effectively produced. The results obtained through the above mentioned research are similar to that found in this paper, even though the items of equipment tested in this research are unused, that is to say, new. The implementation of standards for the production process and later control of the acoustic intensity emitted by items of UST equipment is occurring slowly on the Brazilian market. In its first publication––Diario Ofical da Uni~ ao 12-03-96 [16] the Secretary for Health Control makes a general statement with regard to the definitions of the terms and deadlines for the implementation of some of the stages. It is noted that after more than 24 months have passed, there has still been no completely implemented standardisation. The Brazilian Government intends following the technical standards proposed by IEC 601-2-5 [6], with regard to therapeutic ultrasound. Detailing of the procedures will follow the publication 1689 of 1996. According to Parizotto [17], the Ministry of Health ruling no. 2.043 of 12 December, 1994 updated by ruling no. 155 of 27 February, 1997, calls for there to be a demand that industries manufacturing electro-medical equipment should have certification from accredited laboratories. The companies will become responsible for the quality of the products placed on the market as stipulated in articles 4–25 of the ‘‘C odigo de Defesa do Consumidor’’ (Consumer Defence Code) (Law No. 8.078 of 11 September, 1990). The author concludes that professionals ought to work only with reliable and safe equipment, periodically evaluate the working conditions of these apparatuses and submit them to maintenance, apart from acquiring only equipment with adequate certification. In this context, it is suggested that some companies should implement a more rigid quality control, as well as an updating of their own equipment. It may be observed that analogue equipment presents a variation of intensity higher than digital equipment, thus confirming the necessity of updating the project. A point favouring good calibration is that in physiotherapy departments where patients are treated by equipment that exhibits alterations in acoustic intensity, the results of the treatment may be unsatisfactory. Furthermore, every scientific research that envisages the use of ultrasonic energy only becomes reliable when checking is performed, and if necessary, calibration is carried out prior to experimental tests.
Another alarming point is that there is no assistance from an inspecting body with regard to new or used equipment, since the literature points to the loss of energy emitted when the equipment is used. This great discrepancy between the selected acoustic energy and that emitted may be responsible for the non-reproducibility of the results of clinical practice or in experimental research. According to Cunningham [18] some equipment tested showed 100% error in output intensity. The author comments on a recommendation by Pye [19], in which the author suggests a specific certificate of calibration for ultrasound equipment. The imprecision of ultrasound equipment makes the information in literature irrelevant. There is no guaranteeing that the response to the treatment is due to ultrasound, to the natural evolution of the lesion or even to a placebo. Another relevant point is the fact that the professional receives payment for service, in this case the application of ultrasound, and is not really performing the service due to the equipment not being calibrated. In this context Parizzoto [17] puts forward a reflection, in which he questions whether if the patient was sufficiently informed to opt for or against the performance of a certain examination or treatment and if they knew what type of situation to which they would be submitted, would they consent to having it performed?
5. Conclusions The UST equipment models Sonamed I, Sonacel, Sonacel plus, Sonacel III and Avatar I, although new, presented calibration errors of above 30% when compared with the intensity of the panel, both under continuous and pulsed conditions. The models Sonomaster St., Pr o-seven and Sonopluse were within the specifications proposed by the IEC-601/ 84. There is need for greater quality control on the part of the industries manufacturing therapeutic ultrasound. The companies that sell this equipment should demand from the manufacturers, an improvement in design as well as better quality control. There is urgent need for a supervising body that controls the quality of equipment produced on the national market. Professionals should join forces to demand better quality equipment, as they invest in the purchase thereof and sell a service to the patient, which frequently is not being performed correctly.
Acknowledgements ‘‘Femandes Fisioterapai’’ and ‘‘Skin Distribuidora de Equipment’’ (Skin Equipment Distributors).
R. Guirro, S.C. Britshcy Dos Santos / Ultrasonics 39 (2002) 553–557
References [1] P.N. Burns, T. Mcdiarmid, Clinical applications of therapeutic ultrasound, Physiotherapy 73 (1987) 155–162. [2] H.F. Stewart et al., Survey of use and performance of ultrasonic therapy equipment in pinellas county, Florida, Physical Therapy 54 (1974) 707–715. [3] R. Guirro, F. Serr~ ao, D. Elais, A.J. Bucalon, Calibration of therapeutic ultrasound equipment, Physiotherapy 83 (1997) 419–422. [4] M.C. Fyfe, S.M. Parnell, The importance of measurement of effective transducer radiating area in the testing and calibration of ‘‘therapeutic’’ ultrasonic instruments, Health Physics 43 (1982) 377–381. [5] R.T. Hekkenberg, R. Reibold, B. Zeqiri, Evaluation of ultrasound therapy devices, Physiotherapy 72 (1986) 390–395. [6] International Electrotechnical Commission Publication 601-2-5, Particular Requirements for the Safety of Ultrasonic Therapy Equipment, IEC, Geneve, Suisse, 1984. [7] International Electrotechnical Commission Publication 601-2-5, Ultrasonics-Physiotherapy systems––Performance Requirements and Methods of Measurement in the Frequency Range 0.5–5.0 MHz, IEC, Geneve, Suisse, 1996. [8] A.J. Bucalon, I.L. Batista, Forcßa de radiacß~ao ac ustica e sua medida, Trabalho de iniciacß~ao cientifica, Departamento de Fisica, Unesp-Rio Claro, 1993. [9] K. Hildersley, A simple calorimeter for monitoring the output power of ultrasound therapy machines, Physiotherapy 80 (1994) 219–223.
557
[10] S.D. Pye, C. Milford, The performance of ultrasound physiotherapy machines in Lothian, Scotland, 1992, Ultrasound in Medicine and Biology 20 (1994) 347–359. [11] R. Guirro, S.C.B. Santos, A Realidade da pot^encia ac ustica emitida pelos equipamentos de ultra-som terap^eutico: Uma Revis~ao, Revista de Fisioterapia da Universidade de S~ao Paulo 4 (1997) 76–82. [12] B. Zeqiri, Calibration and safety of physiotherapy ultrasound equipment, Physiotherapy 83 (1997) 559–560. [13] American Standard Specification for Ultrasonic Therapeutic Equipment, American National Standards Institute, New York, January 18, 1956, p. Z24.18. [14] M.H. Repacholi, D.A. Benwell, Using surveys of ultrasound therapy devices to draft performance standards, Health Physics 36 (1979) 679–686. [15] J.J. Lloyde, J.A. Evans, A calibration survey of physiotherapy ultrasound equipment in North Wales, Physiotherapy 74 (1988) 56–61. [16] Diario Oficial da Uni~ao––secretaria de Vigil^ancia Sanit aria––Portaria conjunta No. 1, de 8 de marcßo. tica na eletroterapia––Editorial, Revista Brasileria [17] N. Parizotto, E de Fisioterapia 2 (1998). [18] S.J. Cunningham, Calibration chaos makes research irrelevant, Physiotherapy 83 (1997) 440–441. [19] S.D. Pye, Ultrasound therapy equipment: Does it perform?, Physiotherapy 82 (1996) 36–44.