Sonography/Ultrasound Protocol and Safety Standards

Sonography/Ultrasound Protocol and Safety Standard. By: Sterling Foster

Sonography/Ultrasound Protocol and Safety Standards

A senior research projected submitted in partial requirement for the degree Doctorate of Chiropractic.

Logan University

Sterling Foster

Advisor: Mary Unger-Boyd, DC, DICS, CACCP

December 2013


Abstract:

The evolution of the diagnosis and management of women who are pregnant has been a medical success over the past years. Pregnancy confirmation was once determined by amenorreaic symptoms in the presence sexual activity accompanied by a feeling of “morning sickness.” It progressed into a pregnancy test that has reached a level of sensitivity and specificity which is unlikely to be surpassed either by better tests or alternative technology.22 currently, confirmation of pregnancy is being achieved through visualization of the fetus with sonography. The biophysical effects of the ultrasound are damaging to energy sensitive structures of the fetus if >1.5 TI or MI is exceeded. User incompetence is identified through poor knowledge of safety standards on sonography equipment through questionnaires. These factors must be acknowledged when discussing routine, low-risk ultrasoundography.

Methods: A comprehensive review of the literature is performed. Information was inserted in Cochrane database of Systematic Review, PubMed, and Google Scholar in an attempt to identify the presence of specific practice guidelines when performing prenatal ultrasounds/sonography.

Conclusion: ODS safety standards issued by the FDA exceed levels that may be harmful too the developing fetus, especially the first trimester, when sonography is used improperly by the end user. Further research is needed in regards to regulation standards for ultrasound technicians.

Keywords: sonography, ultrasound, safety, efficacy, complication, protocol and procedure.


Introduction:

The evolution of the diagnosis and management of women who are pregnant has been a

medical success over the past years. Pregnancy confirmation was once determined by

amenorreaic symptoms in the presence of sexual activity accompanied by a feeling of “morning

sickness.” It progressed into a pregnancy test that has reached a level of sensitivity and

specificity which is unlikely to be surpassed either by better tests or alternative technology.22

Currently, confirmation of pregnancy is being achieved through visualization of the fetus with

sonography. The complications of the first two remain minimal, however evidence regarding the

safety of the latter is rarely, if ever, reviewed or questioned. Modern sophisticated

ultrasonographic equipment is capable of delivering substantial levels of acoustic energy into

the body when used at maximum outputs.20 Establishing the boundaries for obstetrical

intervention is important for the health of the mother and child during the gestational period.

Identifying key factors for neonatal mortality are important, but routine ultrasound does not

increase these chances. The New England Journal of Medicine reported screening

ultrasonography did not improve prenatal outcome as compared with the selective use of

ultrasonography on the basis of clinician judgment.1 With such similarity existing between the

two groups it should become even more important to thoroughly analyze the safety of emitting

routine ultrasonography to a developing fetus without first evaluating the potential for harm.

High-energy ultrasound can induce biophysical effects when passing through tissue, for

example, thermal effects and mechanical stress, causing cavitations. Standard ultrasound

protocols and procedures should be in place to prevent abuse or harm to the fetus and


regulation should strictly adhered to. This literature review evaluates the potential side effects

of ultrasound, diagnostic usage, and safety protocols of the end-user.


Discussion:

Biophysical Effects: The FDA mandates that machines capable of producing higher outputs be

able to display to the diagnostician some indication of the relative potential for ultrasound-

induced bioeffects. This regulation is known as the Standard for Real-Time Display of Thermal

and Mechanical Acoustic Output Indices on Diagnostic Ultrasound Equipment, more commonly

known as the output display standard (ODS).15 The ODS indicators comprise two types of

biophysical index: the thermal index (TI) and mechanical index (MI)10 The ODS supplies on

screen, in real time, numerical displays that provide information about the potential for

temperature increases (TI) and mechanical damage (MI).14 These indices are calculated for the

given machine settings on the basis of tissue models and their acoustic properties.

The TI is an estimate of the tissue temperature rise in degrees centigrade (°C). For

particular examination situations, three types of TI have been defined: soft tissue (TIS), bone

tissue (TIB) thermal index, and for cranial examinations (TIC). The presence of bone within the

ultrasound beam greatly increases the likelihood of a temperature rise due to direct absorption

in the bone itself and conduction of heat from bone to adjacent tissues.16 A temperature

elevation less than 1.5°C likely does not present a bioeffects risk to the embryo, although there

has been some debate on the threshold nature of thermal effects. A temperature elevation

greater than 4°C for 5 minutes can present a bioeffects risk to the embryo. Biologically

significant temperature increases can occur at or near to bone in the fetus from the second

trimester, if the beam is held stationary for more than 30 s in some pulsed Doppler

applications.21 Velocity, power, and pulsed spectral Doppler ultrasound all have the potential to


reach these levels. The TI provides a guide for the sonographer and sonologist regarding the

magnitude of the temperature increase.17

The MI attempts to indicate the probability of non-thermal effects occurring within the

tissue. Cavitation is the phenomenon where bubbles form in a liquid material when the local

pressure falls below the vapor pressure of the liquid sufficient to pull the material apart.

Cavitation generally falls into 2 types: (1) inertial or transient cavitation, in which the newly

formed bubble rapidly collapses, producing a shock wave that can be capable of biological

effects and (2) non-inertial cavitations, in which the bubble oscillates in the acoustic field and

appears to be less likely to produce biological effects.16 The MI and TI are only rough estimates

of possible effects and should not be understood as giving more than guidance to the operator.

Nevertheless, the ODS is considered at present to be the best way of providing safety

information.9

According to the ODS, for equipment that can at certain machine settings produce

output energy giving TI or MI ≥ 1.0, the indices should be displayed if they exceed 0.4.16

Sonography Protocol: Cochrane database of Systematic Review (CDSR) produced no results

found with the keyword search “sonography” AND “safety, efficacy, complication, protocol and

procedure.” The same lack of results was found with the keyword “ultrasound” AND “safety,

efficacy, complication, protocol and procedure.”

There were a total of 2 results found in the CDSR when the word “sonography” was used alone

in conjunction with the “Protocol” type result. They are reported as Second-line, post-docetaxel


therapy for advanced, androgen deprivation-refractory prostate cancer; and Transcranial

Doppler sonography for detecting stenosis or occlusion of intracranial arteries people with

acute ischemic stroke. No sonography protocols for prenatal management were identified under

the CDSR.

There were a total of 9 results found in the CDSR when the word “ultrasound” was used

in conjunction with the “Protocol” type result. The studies were as followed:

1. Dimercaptosuccinic acid scan versus ultrasound in screening for vesicoureteral reflux

among children with urinary tract infections. 2. Doppler ultrasound, CT angiography, MR

angiography, and contrast-enhanced MR angiography versus intra-arterial angiography for

moderate and severe carotid stenosis in symptomatic patients. 3. Therapeutic ultrasound for

chronic low-back pain. 4. Therapeutic ultrasound for soft-tissue injuries of the elbow. 5.

Therapeutic ultrasound for soft-tissue injuries of the knee. 6. Traditional landmark versus

ultrasound guidance for central vein catheterization. 7. Transient ultrasound elastography and

magnetic resonance elastography for the diagnosis of oesophageal varices in patients with

chronic liver disease or portal vein thrombosis. 8. Ultrasound-guided transvaginal ovarian

needle drilling for clomiphene-resistant polycystic ovarian syndrome in subfertile women. 9. Use

of endoanal ultrasound for reducing the risk of complications related to anal sphincter injury

after vaginal birth.

No ultrasound protocols for prenatal management were present in the CDSR.

Protocols for sonography have not been systematically reviewed by the CDSR.


LITERATURE STUDY: One study found exposure to multiple prenatal ultrasound examinations

from 18 weeks' gestation onwards might be associated with a small effect on fetal growth but is

followed in childhood by growth and measures of developmental outcome similar to those in

children who had received a single prenatal scan.3 That same study also states that there were

no significant differences indicating deleterious effects of multiple ultrasound studies at any age

as measured by standard tests of childhood speech, language, behavior, and neurological

development.3

Another study suggests that diagnostic US has no adverse effect on embryogenesis or fetal

growth. However, although B and M mode are safe during the first trimester, color, pulsed or

power Doppler should be performed with caution. The US effects are mainly due to cavitation.4

However, this Mechanism has been determined mainly in animal models. Thermal effect, which

was thought to be hazardous, probably does not influence fetal development.4

A similar study suggest children that were exposed to ultrasound in utero showed evidence that

prenatal ultrasound examination does not cause adverse effects with regard to malformations,

childhood malignancy, neurological abnormalities or abnormal growth. 7

Obstetric ultrasound should only be done for medical reasons, and exposure should be

kept as low as reasonably achievable (ALARA) because of the potential for tissue heating. Higher

energy is of particular concern for pulsed Doppler, color flow, first trimester ultrasound with a

long transvesical path (> 5 cm), second or third trimester exams when bone is in the focal zone,

as well as when scanning tissue with minimal perfusion (embryonic) or in patients who are

febrile.5 Operators should minimize risk by limiting dwell time and limiting exposure to critical


structures. Critical structures can be classified as places such as the retina and visual cortex and

the cochlea of the inner ears.21 these places become compromised because of one-to-one cell

connections. Even the eye lens is a sensitive organ because of the lack of continuous blood

circulation, so a rise in temperature caused by ultrasound cannot be counteracted.21

consequently, minor visual or hearing losses could be possible results of ultrasound exposure in

fetal life.

The following equipment generated exposure information is recommended by

Diagnostic Imaging Committee of Health Canada.

Recommendations:

1. Obstetric ultrasound should only be used when the potential medical benefit outweighs any

theoretical or potential risk.

2. Obstetric ultrasound should not be used for nonmedical reasons, such as sex determination,

producing nonmedical photos or videos, or for commercial purposes.

3. Ultrasound exposure should be as low as reasonably achievable (ALARA) because of the

potential for tissue heating when the thermal index exceeds 1. Exposure can be reduced

through the use of output control and (or) by reducing the amount of time the beam is focused

on one place (dwell time).

4. All diagnostic ultrasound devices should comply with the output display standards (MI and

TI).


5. When ultrasound is done for research or teaching purposes, exposed individuals should be

informed if either the MI or TI is greater than 1 and how this exposure compares to that found

in normal diagnostic practice.

6. While imaging the fetus in the first trimester, Doppler and color Doppler should be avoided.5

A contradictory study promotes the use of Doppler ultrasound in identifying the pulsatile index

of veins of the ductos venosus as early as 10-14 weeks. Ductus venosus Doppler studies can

substantially improve Down syndrome screening efficiency.25 Violation of safety protocol

procedures by early use of Doppler ultrasound in the first trimester may affect future fetal

development negatively.

DAMAGE: Mammalian tissues have differing sensitivities to damage by physical agents such as

ultrasound.21 Ultrasound may damage human tissue by a rise in temperature or cavitations.

Local cell death or cell membrane damage, which in turn affects cell differentiation, might be

the result of ultrasound exposure. Hyperthermia is considered teratogenic in human fetuses,

especially during organogenesis in the first trimester.27 Actively dividing cells of the embryonic

and fetal central nervous system are most readily disturbed.21 As a diagnostic ultrasound beam

envelopes a small volume of tissue, it is possible that the effects of mild disturbance may not be

detected unless major neural pathways are involved. Identifying the disturbances is difficult to

calculate in the prenatal period. It has been shown that the output intensities of commercially


available equipments have significantly increased over the years and that they can reach levels

many times higher than those used years ago.11 Increased acoustic output levels, as expressed

by TI levels, are reached during obstetric Doppler studies.24 Evidence demonstrates that maybe

the intent of prevention might be the source of causalgia due to the increase in energy output

of sonography equipment.

USER INCOMPETANCE: One study identifies the profound incompetence and poor quality

control of the end-user. Only 32.2% of the participants were familiar with the term thermal

index, only 17.7% actually gave the correct answer to the question on the nature of the thermal

index. Only 22% were familiar with the term mechanical index, but only 3.8% described it

properly. Almost 80% of end users did not know where to find the acoustic indices. Only 20.8%

were aware that they are displayed on the monographic monitor during the examinations.14

A second study showed 13.4% of residents and 20.9% of maternal-fetal medicine fellows knew

how to find or use the output display standard, and 10.9% of residents and 22.7% of fellows

reported use of the output display standard during their ultrasound examinations. Overall, 37%

to 46% of residents and fellows reported no limitations to the use of obstetric ultrasound and

22% to 39% reported no limitations to the use of Doppler ultrasound in the first, second, and

third trimesters. Only 34.8% of third-year fellows reported use of the output display standard.19

About one-third of the ultrasound experts were able to define the abbreviations TI and MI. For

the subclasses of the TI, the correct answer was found in only 3–8% of cases. Of those who

knew what the TI and MI meant, only two-thirds and one-third of respondents, respectively,


were able to give a simple explanation of the indices.19 In 49% of questionnaires, the Doppler

modes were correctly ranked as generally producing higher ultrasound exposure than the

imaging modes (B-mode, 3D). Some 28% of the respondents correctly indicated where on their

own machine the information on safety indices is displayed. However, not all of them knew how

to control the output energy level. For all items in the questionnaire there were no significant

differences in the results between the three categories of respondents (i.e. physicians,

sonographers and midwives).19

The results of these studies were anything but encouraging and they indicated that the

users, who are supposed to be responsible for controlling exposure of the fetus to ultrasound,

had a very poor knowledge of the basic safety aspects of ultrasound. This was surprising

because the people who are lacking the knowledge of safety are the ones performing the fetal

imaging. It can be presumed that the level of knowledge is still lower among clinicians without

special interest in diagnostic ultrasounds that are routinely using ultrasound for examinations of

pregnant women.

NON DIAGNOSTIC USE: Nondiagnostic uses of ultrasound equipment should be avoided. First-

trimester fetal scans should not use color and power Doppler modes and should not be

performed for the sole purpose of producing souvenir videos or photographs. Production of

fetal souvenir photographs or videos during diagnostic clinical studies should not increase

exposure levels or extend scan times beyond those needed for clinical purposes.18 Operators

should follow safe scanning guidelines and ALARA principles. The FDA considers the promotion,


selling, or leasing of ultrasound equipment for making “keepsake fetal videos” that are not part

of a medical diagnostic procedure to be an unapproved use of a medical device; thus, the use of

diagnostic ultrasound system for these purposes, without a physician’s order, may be in

violation of state laws or regulations.18 Previous studies state 30% of the ultrasound

professionals actually approved of keepsake ultrasound examinations without any clinical

indication. The discrepancy represents the need for stricter regulation in performing ultrasound

for non diagnostic use.

DIAGNOSTIC USE: Routine ultrasound in early pregnancy appears to enable better gestational

age assessment, earlier detection of multiple pregnancies and earlier detection of clinically

unsuspected fetal malformation at a time when termination of pregnancy is possible.2 Of

course, high-risk pregnancy warrant ultrasound exposure at clinician’s discretion. It is more

likely to exceed the ODS safety measure when longer dwell times and needed for diagnoses. In a

study recording the levels of safety indices and their time course during standard examinations

of high-risk pregnancies, including examinations of the uterine and fetal circulation with

Doppler ultrasound, the TI values were found to exceed 1.5 and even 2.0 on several occasions

during the examination.12 Some believe the use of ultrasound as a screening tool is effective

diagnostic use. A high proportion of abdominal wall defects are associated with concurrent

malformations, syndromes or chromosomal abnormalities, stressing the need for the

introduction of repeated detailed ultrasound examination as a standard procedure.26

One study of small sample size reported proper regulation of ODS safety standards. MI and TI

levels never exceeded 1.5.22


Conclusion:

Standard ultrasound protocols and procedures should be in place to prevent abuse or harm to

the fetus. Ultrasound usage continues daily under the impression of zero side-effects; however

evidence demonstrates the potential for tissue heating and cellular destruction through

cavitations if the ultrasound exceeds safety limits. With such a large part of obstetrical

healthcare being prenatal based, it is important to further research efforts to ensure safety

requirements are constantly being evaluated.

The purpose of the ODS was to provide the capability for end users of diagnostic

ultrasound to operate their machines at higher levels to increase diagnostic capabilities. The

ODS does not specify any upper limits and it is up to the end user, whether obstetrician or

sonographer, to be competent enough to follow safety regulations. Obstetricians and

sonographers should be familiar with the output energy, how to control it, and, accordingly,

how to use the machine in a safe manner. More studies of the biophysical effects of cellular

interaction occurring from ultrasound energy need to be performed along with proper end-user

training programs.


References:

1. Ewigman, B. G., Crane, J. P., Frigoletto, F. D., LeFevre, M. L., Bain, R. P., & McNellis, D. (1993). Effect of prenatal ultrasound screening on perinatal outcome. New England journal of medicine, 329(12), 821-827.

2. Neilson, J. P. (1998). Ultrasound for fetal assessment in early pregnancy. Cochrane Database Syst Rev,

3. Newnham, J. P., Doherty, D. A., Kendall, G. E., Zubrick, S. R., Landau, L. L., & Stanley, F. J. (2004). Effects of repeated prenatal ultrasound examinations on childhood outcome up to 8 years of age: follow-up of a randomised controlled trial. The Lancet, 364(9450), 2038-2044.

4. Hershkovitz, R., Sheiner, E., & Mazor, M. (2002). Ultrasound in obstetrics: a review of safety. European Journal of Obstetrics & Gynecology and Reproductive Biology, 101(1), 15-18.

5. Bly, S., & Van den Hof, M. C. (2005). Obstetric ultrasound biological effects and safety. Journal of obstetrics and gynaecology Canada: JOGC= Journal d'obstétrique et gynécologie du Canada: JOGC, 27(6), 572.

6. Barnett, S. B., Ter Haar, G. R., Ziskin, M. C., Rott, H. D., Duck, F. A., & Maeda, K. (2000). International recommendations and guidelines for the safe use of diagnostic ultrasound in medicine. Ultrasound in medicine & biology, 26(3), 355-366.

7. Salvesen KA, Eik-Nes SH. Ultrasound during pregnancy and birthweight, childhood malignancies and neurological development. Ultrasound Med Biol 1999; 25: 1025–1031.

8. Salvesen KA, Eik-Nes SH. Ultrasound during pregnancy and subsequent childhood non righthandedness: a meta-analysis. Ultrasound Obstet Gynecol 1999; 13: 241–246.

9. Maršál, K. (2005). The output display standard: has it missed its target?. Ultrasound in Obstetrics & Gynecology, 25(3), 211-214.

10. European Committee for Ultrasound Radiation Safety. EFSUMB tutorial paper: thermal and mechanical indices. Eur J Ultrasound 1996; 4: 145–150.

11. Whittingham TA. The acoustic output of diagnostic machines. In The Safe Use of Ultrasound in Medical Diagnosis, ter HaarG, DuckFA (eds). British Medical Ultrasound Society/British Institute of Radiology: London, UK, 2000; 16–31.

12. Deane C, Lees C. Doppler obstetric ultrasound: a graphical display of temporal changes in safetyindices. Ultrasound Obstet Gynecol 2000; 15: 418–423.

13. Mole R.Possible hazards of imaging and Doppler ultrasound in obstetrics. Birth1986; 13: 29–37.

14. Sheiner, E., Shoham-Vardi, I., & Abramowicz, J. S. (2007). What do clinical users know regarding safety of ultrasound during pregnancy?. Journal of ultrasound in medicine, 26(3), 319-325.

15. American Institute of Ultrasound in Medicine. How to interpret the ultrasound output display standard for higher acoustic output diagnostic ultrasound devices: version 2[technical bulletin]. J Ultrasound Med 2004; 23:723–726


16. Nelson, T. R., Fowlkes, J. B., Abramowicz, J. S., & Church, C. C. (2009). Ultrasound biosafety considerations for the practicing sonographer and sonologist. Journal of Ultrasound in Medicine, 28(2), 139.

17. World Federation for Ultrasound in Medicine and Biology.WFUMB Symposium on Safety of Ultrasound in Medicine.Conclusions and recommendations on thermal and nonthermal mechanisms for biological effects of ultrasound;Kloster-Banz, Germany; 14–19 April, 1996. Ultrasound Med Biol 1998; 24(suppl 1):i–xvi, S1–S58.

18. Rados C. FDA cautions against ultrasound “keepsake”images. FDA Consumer 2004; January-February. http://www.fda.gov/fdac/features/2004/104_images.html.

19. Houston, L. E., Allsworth, J., & Macones, G. A. (2011). Ultrasound is safe... right? Resident and maternal-fetal medicine fellow knowledge regarding obstetric ultrasound safety. Journal of Ultrasound in Medicine, 30(1), 21-27.

20. Barnett, S. B., Ter Haar, G. R., Ziskin, M. C., Rott, H. D., Duck, F. A., & Maeda, K. (2000). International recommendations and guidelines for the safe use of diagnostic ultrasound in medicine. Ultrasound in medicine & biology, 26(3), 355-366.

21. Barnett, S. B., Rott, H. D., ter Haar, G. R., Ziskin, M. C., & Maeda, K. (1997). The sensitivity of biological tissue to ultrasound. Ultrasound in medicine & biology, 23(6), 805-812.

22. Chard, T. (1992). REVIEW: Pregnancy tests: a review. Human Reproduction, 7(5), 701-710. 23. Sheiner, E., Freeman, J., & Abramowicz, J. S. (2005). Acoustic output as measured by

mechanical and thermal indices during routine obstetric ultrasound examinations. Journal of ultrasound in medicine, 24(12), 1665-1670.

24. Sheiner, E., Shoham-Vardi, I., Pombar, X., Hussey, M. J., Strassner, H. T., & Abramowicz, J. S. (2007). An increased thermal index can be achieved when performing Doppler studies in obstetric sonography. Journal of ultrasound in medicine, 26(1), 71-76.

25. Borrell, A., Gonce, A., Martinez, J. M., Borobio, V., Fortuny, A., Coll, O., & Cuckle, H. (2005). First‐trimester screening for Down syndrome with ductus venosus Doppler studies in addition to nuchal translucency and serum markers. Prenatal diagnosis, 25(10), 901-905.

26. Barisic, I., Clementi, M., Haeusler, M., Gjergja, R., Kern, J., & Stoll, C. (2001). Evaluation of prenatal ultrasound diagnosis of fetal abdominal wall defects by 19 European registries. Ultrasound in obstetrics & gynecology, 18(4), 309-316.

27. Cavicchi TJ, O’Brien WD Jr. Heat generated by ultrasound in an absorbing medium. J Acoust Soc Am 1984; 70: 1244–1245

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Sonography/Ultrasound Protocol and Safety Standards

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