- Email: [email protected]
The American Institute of Ultrasound Policy and statement on safety
First symposium
on safety and standardisation
of ultrasound
4. BASED ON AVAILABLE EVIDENCE, WHAT ARE THE APPROPRIATE INDICATIONS FOR AND THE LIMITATIONS ON, THE USE OF ULTRASOUND IN OBSTETRICS TODAY?
0 G. KOSSOFF and S. B. BARNETT
STUDIES ARE AND SAFETY OF IN PREGNANCY?
A sustained and supportive research effort is recommended to (1) study the fundamental mechanisms leading to bioeffects; (2) develop laboratory experiments that focus on those cellular processes that are most likely to be affected during embryonic and fetal development: (3) perform postnatal studies in animals
?? WORLD POLICIES ON THE USE OF DIAGNOSTIC THE
ULTRASOUND
AMERICAN INSTITUTE AND STATEMENT M. Temple
University,
C.
OF
IN OBSTETRICS
ULTRASOUND ON SAFETY
POLICY
ZISKIN
Philadelphia.
The American Institute of Ultrasound in Medicine considers the Safety of Ultrasound in Obstetrical Practice to be an important topic. There are no fewer than seven committees which in one way or another are concerned with some aspect of this topic. AIUM committees concerned in the use of ultrasound in pregnancy
711
after i?z utero exposure to ultrasound; (4) explore interactions between ultrasound exposure and such agents as drugs, nutrition, ionizing radiation, hyperthermia, and hypoxia; and (5) develop and improve dosimetry. It is also recommended to fund randomized clinical trials on long term follow-up of infants exposed to in zrtero ultrasound and studies to establish clinical efficacy of ultrasound in reducing morbidity and mortality. It is recommended that randomized, controlled clinical trials of routine ultrasound screening during pregnancy should be conducted in the United States. This consensus statement is not meant to be a static document, but represents a distillation of all available experimental, clinical and epidemiological data available until February 1984, and is sure to change in the very near future. The panel learned some interesting facts which were somewhat surprising to most of us: 1. We do not understand ultrasound dose to the fetus. 2. We have not proven efficacy of routine screening of all pregnant patients. 3. We have not proven that there are any reproducible adverse biological effects to the fetus at diagnostic power levels presently used. 4. Quality of ultrasound imaging varies from very poor to excellent with very little attention for quality control. 5. There are insufficient numbers of trained physicians and sonographers to perform the ultrasound examinations, if routine screening were ever found to be efficacious. On the basis of this information the panel concluded that until more information was available it could not recommend the utilisation of routine ultrasound screening in obstetrics.
It is the consensus of the panel that ultrasound examination in pregnancy be performed for a specific medical indication. The data on clinical efficacy and safety do not allow a recommendation for routine screening at this time. Specific indications have been considered in question 2. Another important limitation on the use of obstetrical ultrasound is that this technique is critically dependent upon examiner training and experience, and there are too few adequately trained ultrasonologists to affect a mass screening effort, even if it were proven efficacious. The panel recommends minimum training requirements and uniform credentialling for all physicians and sonographers performing ultrasound examinations, and these individuals should demonstrate adequate knowledge of basic physical priciples of ultrasound, transducers, and equipment and keep adequate records of the procedures performed, the indications and the findings. 5. WHAT FURTHER NEEDED OF EFFICACY USE OF ULTRASOUND
in obstetrics
Pennsylvania
19 140, USA
Section of Obstetrics and Gynaecology Bioeffects Committee Education Committee Standards Committee Manufacturers Commendation Panel Task Force ?? AIUM/NEMA . Public Relations Committee ??
. . . .
712
Ultrasound
in Medicine
and Biology
Legislative Council Central Planning Committee The Public Relations Committee is charged with the responsibility of providing factual information to the general public. Working under the philosophy that society is best served by a well-informed public, this Committee has produced a pamphlet entitled “Your Ultrasound Examination,” for distribution in physicians’ offices. The Education Committee is concerned with ensuring that physicians and other users of ultrasound possess adequate knowledge and training in the safe practice of medical ultrasound. In conjunction with the American College of Radiology, and the American College of Obstetricians and Gynecologists, this Committee has issued “Guidelines for Post-Residency Training in Obstetrical and Gynaecological Ultrasound.” Minimum recommendations for post-residency training in obstetrical and gynecological ultrasound Supervised and-documented training in an 1 month established ultrasound facility To include: Basic physics, Technique, Performance, and Interpretation Practical experience (at least 200 exami2 months nations) ??
??
Continuing education-self assessment examinations The Standards Committee has generated a number of standards and guidelines for testing, specifying, and labelling (see attached list of AIUM Publications). The Manufacturers Commendation Panel awards commendation certification to those ultrasonic instrument manufacturers who specify and make known the acoustic outputs of these instruments. This Committee has just made available the most complete compilation of acoustic data for diagnostic ultrasound equipment ever assembled. The Bioeffects Committee has been particularly valuable in providing AIUM with constant vigilance of the world literature on the biological effects of ultrasound and its critical evaluation by recognised authorities in this field. This Committee has produced a number of important AIUM Statements and Documents. The question “How safe is ultrasound?” has no simple, absolute answer. In considering this question, the AIUM has formulated three statements that offer guidance in the judicious application of ultrasound in medical practice. The AIUM Statement on Clinical Safety draws upon decades of collective clinical experience to address risk-benefit considerations. The Statement on Mammalian In Viva Ultrasonic Biological Effects is based upon an extensive review of animal experiments. It is
September
1986, Volume
12, Number
9
stated in terms of acoustic exposure parameters that will be explained prior to presenting the statement. The AIUM Statement on In Vitro Biological Effects provides a viewpoint for interpreting the significance of experimental biological effects observed under conditions that do not correspond directly to the clinical situation.
Statement on clinical safety Diagnostic ultrasound has been in use for over twenty-five years. Given its known benefits and recognised efficacy for medical diagnosis, including use during human pregnancy, the American Institute of Ultrasound in Medicine herein addresses the clinical safety of such use: No confirmed biological effects on patients or instrument operators caused by exposure at intensities typical of present diagnostic ultrasound instruments have ever been reported. Although the possibility exists that such biological effects may be identified in the future, current data indicates that the benefits to patients of the prudent use of diagnostic ultrasound outweigh the risks, if any, that may be present. This statement is self-explanatory. It implies that one should not hesitate to use ultrasound, with appropriate equipment and procedures, when medical benefit is expected. It does not suggest that ultrasound should be used as a “toy” or that it is “perfectly safe,” and it calls attention to the need for continued awareness of future research findings. It also calls for the prudent use of diagnostic ultrasound. In, 1976, the AIUM Bioeffects Committee reviewed the literature describing ultrasonically induced effects in in viva mammalian tissues and formulated a summary statement regarding such effects. This statement has been reviewed periodically by the AIUM and has been slightly revised.
Statement on mammalian in vivo ultrasonic biological t@cts (Oct. 1982) In the low megahertz frequency range there have been (as of this date) no independently confirmed significant biological effects in mammalian tissues exposed to intensities? below 100 mW/cm’. Furthermore, for ultrasonic exposure times* less than 500 seconds and greater than one second, such effects have not been demonstrated even at higher intensities, when the product of intensity? and exposure time+ is less than 50 joules/cm*. t Spatial peak, temporal
average as measured
in a free field in
water. $ Total time: this includes off-time as well as on-time for a repeated pulse regime. Note that the intensity referred to is the SPTA value for the pulsed mode and the SP value for the CW mode.
First symposium on safety and standardisation of ultrasound in obstetrics 0 G. KOSSOW and S. B. BARNETT
Accompanying this Statement on Mammalian In Mvo Ultrasonic Biological Effects were comments by the Bioeffects Committee, the substance of which (somewhat paraphrased) is as follows. ?? This statement apparently applies to all existing data on biological changes produced in mammalian tissues by ultrasound in the frequency range from about 0.5 10 MHz. Included in our literature review leading to this statement are results obtained with focussed as well as unfocussed ultrasonic fields, generated continuously or (to a lesser extent) in a series of repeated pulses. ?? This statement includes all seemingly reliable data considered in published summaries as well as results of satisfactory quality which have been published more recently. We have consulted a “jury” of informed investigators and have not learned of any exception to the statement. However, in any application of the Statement on Mammalian In IGo Ultrasonic Biological Effects to “safety decisions,” attention should be given to the following considerations:
While useful results are now being generated in several research laboratories, the pool of reliable and highly relevant data is only beginning to fill. Most experiments have not been repeated by independent investigators. Especially in short supply are results at low intensities and long exposure times. Little research has been done with repeated short pulses such as would be most relevant to diagnostic ultrasound. ?? Data available at present on intensity levels at which biological effects occur are, in general, not minimum levels (if, indeed, definite minima exist). Further research is urgently needed to determine whether signficant biological changes occur at levels lower than those corresponding to the Statement. As more results become available, it is reasonable to expect at least some lowering of the observed “threshold” levels for some biological systems, especially as more sensitive tests are used, and as more critical physical conditions are identified. ?? We believe the Statement will be helpful in arriving at recommendations for wise use of ultrasound in medicine. However, the Statement does not, in itself, imply specific advice on “safe levels” which might be universally valid. Determination of recommended maximum levels will require consideration of such difficult topics as: adequacy of present knowledge of biological effects; expected reliability of equipment specifications; assessment of patient benefits; and others. So far these matters have not been treated systematically.
??
713
It is to be noted that the Statement on Mammalian In V~vo Ultrasonic Biological Effects applies to data for mammals and does not pertain to plants or to in vitro experiments. The statement carries a date and the committee is aware that exceptions might be found in future experiments. The Bioeffects Committee continually reviews the literature to determine whether an exception has occurred. The value quoted, an SPTA intensity of 100 mW/ cm*, is not to be considered as a definitive threshold for damage, or for “perfectly safe” operation. Nevertheless, it does serve as a useful basis for discussion. Data which have been reported for commercial pulseecho ultrasound devices show that SPTA intensities fall in the range 0.01 to 200 mW/cm*. In vitro biological efects experiments There have been, and continue to be, a large number of experiments concerning the biological effects of ultrasound on in vitro preparations. These studies have provided useful data regarding mechanisms of interaction between ultrasound and biological constituents. However, it is often difficult to extrapolate in vitro results to the clinical situation. The difficulty arises partly from biological considerations, i.e. the in vitro preparation might not exhibit the same response as an in vivo system would. In addition, the ultrasonic exposure conditions existing in an in vitro preparation might not closely simulate those found within intact human tissues, and the mechanisms of action might be different. Often, these difficulties in extrapolating in vitro results have been neglected and their applicability to the clinical situation has been mis-stated. Therefore, the AIUM Bioeffects Committee issued a statement regarding ultrasonically induced in vitro effects which is presented below.
Statement on in vitro biological effects It is often difficult to evaluate reports of ultrasonically induced in vitro biological effects with respect to their clinical significance. The predominant physical and biological interactions and mechanisms involved in an in vitro effect may not pertain to the in vivo situation. Nevertheless, an in vitro effect must be regarded as a real biological effect. Results from in vitro experiments suggest new endpoints and serve as a basis for design of in vivo experiments. In vitro studies provide the capability to control experimental variables and thus offer a means to explore and evaluate specific mechanisms. Although they may have limited applicability to irz vivo biological effects, such studies can disclose fundamental intercellular or intracellular interactions. While it is valid for authors to place their results in context and to suggest further relevant investigations,
714
Ultrasound in Medicine and Biology
reports which do more than that should be viewed with caution. SUMMARY While no simple, absolute answers exist to the question of the safety of diagnostic ultrasound, the available information suggests the following reasonable attitudes towards its medical use. Diagnostic ultrasound has proven to be a valuable tool in medical practice and should be used without hesitation, with appropriate equipment and procedures,
POLICY
September 1986, Volume 12, Number 9
when medical benefit is expected. An excellent safety record exists in that after decades of clinical use there is no known instance of human injury due to diagnostic ultrasound. In assessing risk, overly simplistic attitudes should be avoided. The SPTA intensity of 100 mW/cm* should not be treated as a magic number. Levels under this value do not guarantee “perfect” safety, and levels above this value may well be appropriate if they are needed to yield diagnositc information. In choosing procedures and equipment, the obligation is always present to balance benefit against risk.
STATEMENT OF THE AUSTRALIAN FOR ULTRASOUND IN MEDICINE
SOCIETY
W. J. GARRETT Royal Hospital for Women, Sydney, NSW. 2000 Australia POLICY
ON
ULTRASOUND
SERVICES
1. At present there have been no independently verified studies that have demonstrated any biological effect of diagnostic ultrasound in vivo in humans. As a matter of principle patients should be examined only by competent personnel and only as much as is necessary to provide the required diagnostic information. 3 Ultrasound _. services should be provided only by those Medical Practitioners wo have competence in the specific examinations they undertake. Such examinations must be in the best interest of the patients and carried out using appropriate equipment. 3. Patient identification. The date of service and name of the Medical Practitioner or Medical Practice responsible for the conduct of the ultrasound examination should be imprinted in, or otherwise recorded with, each film or other record. 4. A written report should be issued on all ultrasound examinations by the responsible Medical Practitioner and the report should be made available with copies of the films or other records in response to a legitimate request. examinations performed 5. A request of ultrasound should be kept by each medical practice. 6. Specialists in ultrasound should collaborate in undergraduate and postgraduate education and in the education of other Medical Practitioners and Sonographers. 7. While all Medical Practitioners should be free to
request ultrasound investigations dependent on their clinical experience and judgement, a specialist in diagnostic ultrasound has a duty to decide whether a requested investigation is appropriate, having regard to the level of diagnosis required, risks involved and cost effectiveness. 8. Sonographers should not practice independently of Medical Practitioners.
POLICY
ON
OBSTETRIC
EXAMINATIONS
It is considered that a standard obstetric ultrasound examination should include evaluation of the following aspects of the pregnancy: 1. Fetal number 2. Fetal cardiac activity (after 7 wk) 3. Fetal presentation (where appropriate) 4. Gestational age (by multiple parameters) 5. Placental localisation 6. Amount of amniotic fluid 7. Major fetal anatomical landmarks 8. Evaluation of the uterus and adnexa 9. Fetal abnormality It is recognised that NOT all structural congenital abnormalities can be identified but if there is uncertainty with regard to the findings, a second opinion should be sought. This list is not meant to be exclusive or exhaustive, but serves as a guide to the minimum information necessary for an adequate ultrasound examination in pregnancy.
on safety and standardisation
of ultrasound
4. BASED ON AVAILABLE EVIDENCE, WHAT ARE THE APPROPRIATE INDICATIONS FOR AND THE LIMITATIONS ON, THE USE OF ULTRASOUND IN OBSTETRICS TODAY?
0 G. KOSSOFF and S. B. BARNETT
STUDIES ARE AND SAFETY OF IN PREGNANCY?
A sustained and supportive research effort is recommended to (1) study the fundamental mechanisms leading to bioeffects; (2) develop laboratory experiments that focus on those cellular processes that are most likely to be affected during embryonic and fetal development: (3) perform postnatal studies in animals
?? WORLD POLICIES ON THE USE OF DIAGNOSTIC THE
ULTRASOUND
AMERICAN INSTITUTE AND STATEMENT M. Temple
University,
C.
OF
IN OBSTETRICS
ULTRASOUND ON SAFETY
POLICY
ZISKIN
Philadelphia.
The American Institute of Ultrasound in Medicine considers the Safety of Ultrasound in Obstetrical Practice to be an important topic. There are no fewer than seven committees which in one way or another are concerned with some aspect of this topic. AIUM committees concerned in the use of ultrasound in pregnancy
711
after i?z utero exposure to ultrasound; (4) explore interactions between ultrasound exposure and such agents as drugs, nutrition, ionizing radiation, hyperthermia, and hypoxia; and (5) develop and improve dosimetry. It is also recommended to fund randomized clinical trials on long term follow-up of infants exposed to in zrtero ultrasound and studies to establish clinical efficacy of ultrasound in reducing morbidity and mortality. It is recommended that randomized, controlled clinical trials of routine ultrasound screening during pregnancy should be conducted in the United States. This consensus statement is not meant to be a static document, but represents a distillation of all available experimental, clinical and epidemiological data available until February 1984, and is sure to change in the very near future. The panel learned some interesting facts which were somewhat surprising to most of us: 1. We do not understand ultrasound dose to the fetus. 2. We have not proven efficacy of routine screening of all pregnant patients. 3. We have not proven that there are any reproducible adverse biological effects to the fetus at diagnostic power levels presently used. 4. Quality of ultrasound imaging varies from very poor to excellent with very little attention for quality control. 5. There are insufficient numbers of trained physicians and sonographers to perform the ultrasound examinations, if routine screening were ever found to be efficacious. On the basis of this information the panel concluded that until more information was available it could not recommend the utilisation of routine ultrasound screening in obstetrics.
It is the consensus of the panel that ultrasound examination in pregnancy be performed for a specific medical indication. The data on clinical efficacy and safety do not allow a recommendation for routine screening at this time. Specific indications have been considered in question 2. Another important limitation on the use of obstetrical ultrasound is that this technique is critically dependent upon examiner training and experience, and there are too few adequately trained ultrasonologists to affect a mass screening effort, even if it were proven efficacious. The panel recommends minimum training requirements and uniform credentialling for all physicians and sonographers performing ultrasound examinations, and these individuals should demonstrate adequate knowledge of basic physical priciples of ultrasound, transducers, and equipment and keep adequate records of the procedures performed, the indications and the findings. 5. WHAT FURTHER NEEDED OF EFFICACY USE OF ULTRASOUND
in obstetrics
Pennsylvania
19 140, USA
Section of Obstetrics and Gynaecology Bioeffects Committee Education Committee Standards Committee Manufacturers Commendation Panel Task Force ?? AIUM/NEMA . Public Relations Committee ??
. . . .
712
Ultrasound
in Medicine
and Biology
Legislative Council Central Planning Committee The Public Relations Committee is charged with the responsibility of providing factual information to the general public. Working under the philosophy that society is best served by a well-informed public, this Committee has produced a pamphlet entitled “Your Ultrasound Examination,” for distribution in physicians’ offices. The Education Committee is concerned with ensuring that physicians and other users of ultrasound possess adequate knowledge and training in the safe practice of medical ultrasound. In conjunction with the American College of Radiology, and the American College of Obstetricians and Gynecologists, this Committee has issued “Guidelines for Post-Residency Training in Obstetrical and Gynaecological Ultrasound.” Minimum recommendations for post-residency training in obstetrical and gynecological ultrasound Supervised and-documented training in an 1 month established ultrasound facility To include: Basic physics, Technique, Performance, and Interpretation Practical experience (at least 200 exami2 months nations) ??
??
Continuing education-self assessment examinations The Standards Committee has generated a number of standards and guidelines for testing, specifying, and labelling (see attached list of AIUM Publications). The Manufacturers Commendation Panel awards commendation certification to those ultrasonic instrument manufacturers who specify and make known the acoustic outputs of these instruments. This Committee has just made available the most complete compilation of acoustic data for diagnostic ultrasound equipment ever assembled. The Bioeffects Committee has been particularly valuable in providing AIUM with constant vigilance of the world literature on the biological effects of ultrasound and its critical evaluation by recognised authorities in this field. This Committee has produced a number of important AIUM Statements and Documents. The question “How safe is ultrasound?” has no simple, absolute answer. In considering this question, the AIUM has formulated three statements that offer guidance in the judicious application of ultrasound in medical practice. The AIUM Statement on Clinical Safety draws upon decades of collective clinical experience to address risk-benefit considerations. The Statement on Mammalian In Viva Ultrasonic Biological Effects is based upon an extensive review of animal experiments. It is
September
1986, Volume
12, Number
9
stated in terms of acoustic exposure parameters that will be explained prior to presenting the statement. The AIUM Statement on In Vitro Biological Effects provides a viewpoint for interpreting the significance of experimental biological effects observed under conditions that do not correspond directly to the clinical situation.
Statement on clinical safety Diagnostic ultrasound has been in use for over twenty-five years. Given its known benefits and recognised efficacy for medical diagnosis, including use during human pregnancy, the American Institute of Ultrasound in Medicine herein addresses the clinical safety of such use: No confirmed biological effects on patients or instrument operators caused by exposure at intensities typical of present diagnostic ultrasound instruments have ever been reported. Although the possibility exists that such biological effects may be identified in the future, current data indicates that the benefits to patients of the prudent use of diagnostic ultrasound outweigh the risks, if any, that may be present. This statement is self-explanatory. It implies that one should not hesitate to use ultrasound, with appropriate equipment and procedures, when medical benefit is expected. It does not suggest that ultrasound should be used as a “toy” or that it is “perfectly safe,” and it calls attention to the need for continued awareness of future research findings. It also calls for the prudent use of diagnostic ultrasound. In, 1976, the AIUM Bioeffects Committee reviewed the literature describing ultrasonically induced effects in in viva mammalian tissues and formulated a summary statement regarding such effects. This statement has been reviewed periodically by the AIUM and has been slightly revised.
Statement on mammalian in vivo ultrasonic biological t@cts (Oct. 1982) In the low megahertz frequency range there have been (as of this date) no independently confirmed significant biological effects in mammalian tissues exposed to intensities? below 100 mW/cm’. Furthermore, for ultrasonic exposure times* less than 500 seconds and greater than one second, such effects have not been demonstrated even at higher intensities, when the product of intensity? and exposure time+ is less than 50 joules/cm*. t Spatial peak, temporal
average as measured
in a free field in
water. $ Total time: this includes off-time as well as on-time for a repeated pulse regime. Note that the intensity referred to is the SPTA value for the pulsed mode and the SP value for the CW mode.
First symposium on safety and standardisation of ultrasound in obstetrics 0 G. KOSSOW and S. B. BARNETT
Accompanying this Statement on Mammalian In Mvo Ultrasonic Biological Effects were comments by the Bioeffects Committee, the substance of which (somewhat paraphrased) is as follows. ?? This statement apparently applies to all existing data on biological changes produced in mammalian tissues by ultrasound in the frequency range from about 0.5 10 MHz. Included in our literature review leading to this statement are results obtained with focussed as well as unfocussed ultrasonic fields, generated continuously or (to a lesser extent) in a series of repeated pulses. ?? This statement includes all seemingly reliable data considered in published summaries as well as results of satisfactory quality which have been published more recently. We have consulted a “jury” of informed investigators and have not learned of any exception to the statement. However, in any application of the Statement on Mammalian In IGo Ultrasonic Biological Effects to “safety decisions,” attention should be given to the following considerations:
While useful results are now being generated in several research laboratories, the pool of reliable and highly relevant data is only beginning to fill. Most experiments have not been repeated by independent investigators. Especially in short supply are results at low intensities and long exposure times. Little research has been done with repeated short pulses such as would be most relevant to diagnostic ultrasound. ?? Data available at present on intensity levels at which biological effects occur are, in general, not minimum levels (if, indeed, definite minima exist). Further research is urgently needed to determine whether signficant biological changes occur at levels lower than those corresponding to the Statement. As more results become available, it is reasonable to expect at least some lowering of the observed “threshold” levels for some biological systems, especially as more sensitive tests are used, and as more critical physical conditions are identified. ?? We believe the Statement will be helpful in arriving at recommendations for wise use of ultrasound in medicine. However, the Statement does not, in itself, imply specific advice on “safe levels” which might be universally valid. Determination of recommended maximum levels will require consideration of such difficult topics as: adequacy of present knowledge of biological effects; expected reliability of equipment specifications; assessment of patient benefits; and others. So far these matters have not been treated systematically.
??
713
It is to be noted that the Statement on Mammalian In V~vo Ultrasonic Biological Effects applies to data for mammals and does not pertain to plants or to in vitro experiments. The statement carries a date and the committee is aware that exceptions might be found in future experiments. The Bioeffects Committee continually reviews the literature to determine whether an exception has occurred. The value quoted, an SPTA intensity of 100 mW/ cm*, is not to be considered as a definitive threshold for damage, or for “perfectly safe” operation. Nevertheless, it does serve as a useful basis for discussion. Data which have been reported for commercial pulseecho ultrasound devices show that SPTA intensities fall in the range 0.01 to 200 mW/cm*. In vitro biological efects experiments There have been, and continue to be, a large number of experiments concerning the biological effects of ultrasound on in vitro preparations. These studies have provided useful data regarding mechanisms of interaction between ultrasound and biological constituents. However, it is often difficult to extrapolate in vitro results to the clinical situation. The difficulty arises partly from biological considerations, i.e. the in vitro preparation might not exhibit the same response as an in vivo system would. In addition, the ultrasonic exposure conditions existing in an in vitro preparation might not closely simulate those found within intact human tissues, and the mechanisms of action might be different. Often, these difficulties in extrapolating in vitro results have been neglected and their applicability to the clinical situation has been mis-stated. Therefore, the AIUM Bioeffects Committee issued a statement regarding ultrasonically induced in vitro effects which is presented below.
Statement on in vitro biological effects It is often difficult to evaluate reports of ultrasonically induced in vitro biological effects with respect to their clinical significance. The predominant physical and biological interactions and mechanisms involved in an in vitro effect may not pertain to the in vivo situation. Nevertheless, an in vitro effect must be regarded as a real biological effect. Results from in vitro experiments suggest new endpoints and serve as a basis for design of in vivo experiments. In vitro studies provide the capability to control experimental variables and thus offer a means to explore and evaluate specific mechanisms. Although they may have limited applicability to irz vivo biological effects, such studies can disclose fundamental intercellular or intracellular interactions. While it is valid for authors to place their results in context and to suggest further relevant investigations,
714
Ultrasound in Medicine and Biology
reports which do more than that should be viewed with caution. SUMMARY While no simple, absolute answers exist to the question of the safety of diagnostic ultrasound, the available information suggests the following reasonable attitudes towards its medical use. Diagnostic ultrasound has proven to be a valuable tool in medical practice and should be used without hesitation, with appropriate equipment and procedures,
POLICY
September 1986, Volume 12, Number 9
when medical benefit is expected. An excellent safety record exists in that after decades of clinical use there is no known instance of human injury due to diagnostic ultrasound. In assessing risk, overly simplistic attitudes should be avoided. The SPTA intensity of 100 mW/cm* should not be treated as a magic number. Levels under this value do not guarantee “perfect” safety, and levels above this value may well be appropriate if they are needed to yield diagnositc information. In choosing procedures and equipment, the obligation is always present to balance benefit against risk.
STATEMENT OF THE AUSTRALIAN FOR ULTRASOUND IN MEDICINE
SOCIETY
W. J. GARRETT Royal Hospital for Women, Sydney, NSW. 2000 Australia POLICY
ON
ULTRASOUND
SERVICES
1. At present there have been no independently verified studies that have demonstrated any biological effect of diagnostic ultrasound in vivo in humans. As a matter of principle patients should be examined only by competent personnel and only as much as is necessary to provide the required diagnostic information. 3 Ultrasound _. services should be provided only by those Medical Practitioners wo have competence in the specific examinations they undertake. Such examinations must be in the best interest of the patients and carried out using appropriate equipment. 3. Patient identification. The date of service and name of the Medical Practitioner or Medical Practice responsible for the conduct of the ultrasound examination should be imprinted in, or otherwise recorded with, each film or other record. 4. A written report should be issued on all ultrasound examinations by the responsible Medical Practitioner and the report should be made available with copies of the films or other records in response to a legitimate request. examinations performed 5. A request of ultrasound should be kept by each medical practice. 6. Specialists in ultrasound should collaborate in undergraduate and postgraduate education and in the education of other Medical Practitioners and Sonographers. 7. While all Medical Practitioners should be free to
request ultrasound investigations dependent on their clinical experience and judgement, a specialist in diagnostic ultrasound has a duty to decide whether a requested investigation is appropriate, having regard to the level of diagnosis required, risks involved and cost effectiveness. 8. Sonographers should not practice independently of Medical Practitioners.
POLICY
ON
OBSTETRIC
EXAMINATIONS
It is considered that a standard obstetric ultrasound examination should include evaluation of the following aspects of the pregnancy: 1. Fetal number 2. Fetal cardiac activity (after 7 wk) 3. Fetal presentation (where appropriate) 4. Gestational age (by multiple parameters) 5. Placental localisation 6. Amount of amniotic fluid 7. Major fetal anatomical landmarks 8. Evaluation of the uterus and adnexa 9. Fetal abnormality It is recognised that NOT all structural congenital abnormalities can be identified but if there is uncertainty with regard to the findings, a second opinion should be sought. This list is not meant to be exclusive or exhaustive, but serves as a guide to the minimum information necessary for an adequate ultrasound examination in pregnancy.