Copenhagen, Denmark 21 August 2010 – ECMUS Committee Report to the Board of Directors

BMUS and BIR (British Institute of Radiology) published the 1st edition of this book in 2000. This was sent free of charge to all BMUS members, and has become a well referenced text. It has now been agreed to update this volume as safety issues have moved on.

Costings from Sherry Dixon, BMUS: Up to 144 pages, plus cover

Trim size B5

Print run 5,000

Printing - £ 5,000 (full colour); £ 3,900 (black & white text)

Typesetting - £ 1,404

Copy editing - £ 700

Total: £ 7,104 for full colour; £ 6,004 for black & white text

The following sponsorship has been obtained:

EFSUMB £ 1400 (typesetting costs)

BMUS £ 2000

National Physical Laboratories (UK) £ 4000–4500

The printing element assumed that we would distribute the book to all BMUS members and EUROSON 2011 delegates.

Proposed Content:

Editor: Gail ter Haar

1. Introduction G. ter Haar (UK)
2. The propagation of ultrasound through tissue F. Duck (UK)
3. The acoustic output of diagnostic machines B. Ward (UK)
4. Ultrasound-induced heating and its biological consequences, Charlie Church (USA) +? Moonen (Fr)
5. Mechanical effects of diagnostic ultrasound – To be decided, ? Coussios (UK) or ?de Jong (NL)
6. Non-thermal effects — acoustic streaming and other radiation stress effects H. Starritt (UK)
7. Bio-effects – cells and tissues, G. ter Haar & Sienkiwiecz (UK)
8. The Safety of Ultrasound Contrast Agents, D. Miller (USA) + ? A. van Wamel (NL)
9. Epidemiological studies of diagnostic ultrasound, K. Salvesen (N)
10. Safety standards and regulations: the manufacturers’ responsibilities, F. Duck (UK)
11. Guidelines and recommendations for the safe use of diagnostic ultrasound: the users’ responsibilities, G. ter Haar (UK)

I have suggested a deadline for full manuscript submission to BMUS of April 1st 2011, with the aim of publication in time for EUROSON 2011.

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3. Ongoing ECMUS Activities

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I. Tutorial Articles

These are designed to be teaching articles aimed at the clinical user without a background in Physics. Suggestions for future topics will be gratefully received!

List of tutorial articles in preparation:

1. Sonothrombolysis: Complete
2. Keepsake scanning: In draft
3. Cellular effects: In draft
4. TI/MI Indices: In draft
5. Opthalmology: In draft
6. QA & Safety: In preparation
7. Neonatal Doppler: In preparation
8. Diagnostic exposures: In preparation – revision of 20: 03 version
9. HIFU & Prostate: To be written
10. Elastography

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Past tutorial articles that are to be updated as necessary/republished in near future

Acoustic Cavitation & Capillary Bleeding (1999)
Color Flow Imaging – Safety Aspects (1996)
Epidemiology (2002)
Genetic Aspects (1994)
Non-linearity and Finite Amplitude Effects (1994)
Principles & Methods of Field Measurements (1994)
Pulsed Doppler Devises – Safety Aspects (1991/2)
Radiation Stress and its Bio-effects (2000)
Safety of Ultrasonic Contrast Agents (1999)
Terms used in Describing Ultrasound Exposures (1997)
Thermal and Mechanical Indices (1996/7)
Thermal Teratology (1999)
Transvaginal Ultrasonography – Safety Aspects (1993–95)
What Happens When you Alter the Settings on your Diagnostic Ultrasound Machine - Safety Considerations (1990-95)

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II. Literature reviews

21 safety related articles are currently under review. These are published in the EFSUMB newsletter, and on the website.

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III. Maintenance of Safety Statements

Existing safety statements are reviewed annually and revised as necessary.

(Clinical safety statement; Souvenir scanning statement). The latest safety statements are also to be found on the EFSUMB website www.efsumb.org.

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IV. Congresses

A safety demonstration/lecture on safety indices and transducer heating has been arranged for Copenhagen 2010. The Post it pads with a safety message, advertising safety on the EFSUMB website will be available in Vienna 2011.

Gail ter Haar

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Appendix A

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European Committee of Medical Ultrasound Safety (ECMUS)

A Safety Statement has been published by EFSUMB annually since 1994. The text is deliberately brief, and gives a concise overview of safety in the use of diagnostic ultrasound. The 2009 Statement is the sixth revision of the Statement.

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Clinical Safety Statement for Diagnostic Ultrasound (2009)

Diagnostic ultrasound has been widely used in clinical medicine for many years with no proven deleterious effects. However, if used imprudently, diagnostic ultrasound is capable of producing harmful effects. The range of clinical applications is becoming wider, the number of patients undergoing ultrasound examinations is increasing and new techniques with higher acoustic output levels are being introduced. It is therefore essential to maintain vigilance to ensure the continued safe use of ultrasound.

Ultrasound examinations should only be performed by competent personnel who are trained and updated in safety matters. It is also important that ultrasound devices are appropriately maintained.

Ultrasound produces heating, pressure changes and mechanical disturbances in tissue. Diagnostic levels of ultrasound can produce temperature rises that are hazardous to sensitive organs and the embryo/fetus. Biological effects of non-thermal origin have been reported in animals but, to date, no such effects have been demonstrated in humans, except when a microbubble contrast agent is present.

The Thermal index (TI) is an on-screen guide to the user of the potential for tissue heating. The Mechanical index (MI) is an on-screen guide of the likelihood and magnitude of nonthermal effects. Users should regularly check both indices while scanning and should adjust the machine controls to keep them as low as reasonably achievable (ALARA principle) without compromising the diagnostic value of the examination. Where low values cannot be achieved, examination times should kept as short as possible. Guidelines issued by several ultrasound societies are available.

Some modes are more likely than others to produce significant acoustic outputs and, when using these modes, particular care should be taken to regularly check the TI and MI indices. Spectral pulse wave Doppler and Doppler imaging modes (colour flow imaging and power Doppler imaging) in particular can produce more tissue heating and hence higher TI values, as can B-mode techniques involving coded transmissions. Tissue harmonic imaging mode can sometimes involve higher MI values. 3D (three dimensional) imaging does not introduce any additional safety considerations, particularly if there are significant pauses during scanning to study or manipulate the reconstructed images. However, 4D scanning (real-time 3D) involves continuous exposure and users should guard against the temptation to prolong examination times unduly in an effort to improve the recorded image sequence beyond that which is necessary for diagnostic purposes.

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Ultrasound Exposure During Pregnancy

The embryo/fetus in early pregnancy is known to be particularly sensitive. In view of this and the fact that there is very little information currently available regarding possible subtle biological effects of diagnostic levels of ultrasound on the developing human embryo or fetus, care should be taken to limit the exposure time and the Thermal and Mechanical Indices to the minimum commensurate with an acceptable clinical assessment.

Temperature rises are likely to be greatest at bone surfaces and adjacent soft tissues. With increasing mineralisation of fetal bones, the possibility of heating sensitive tissues such as brain and spinal cord increases. Extra vigilance is advised when scanning such critical fetal structures, at any stage in pregnancy. Based on scientific evidence of ultrasound-induced biological effects to date, there is no reason to withhold diagnostic scanning during pregnancy, provided it is medically indicated and is used prudently by fully trained operators. This includes routine scanning of pregnant women. However, Doppler ultrasound examinations should not be used routinely in the first trimester of pregnancy.

The power levels used for fetal heart rate monitoring (cardiotocography – CTG) are sufficiently low that the use of this modality is not contra-indicated on safety grounds, even when it is to be used for extended periods.

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Safety Considerations for Other Sensitive Organs

Particular care should be taken to reduce the risk of thermal and non-thermal effects during investigations of the eye and when carrying out neonatal cardiac and cranial investigations.

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Ultrasound Contrast Agents (UCA)

These usually take the form of stable gas filled microbubbles, which can potentially produce cavitation or microstreaming, the risk of which increases with MI value. Data from small animal models suggest that microvascular damage or rupture is possible. Caution should be considered for the use of UCA in tissues where damage to microvasculature could have serious clinical implications, such as in the brain, the eye, and the neonate. As in all diagnostic ultrasound procedures, the MI and TI values should be continually checked and kept as low as possible. It is possible to induce premature ventricular contractions in contrast enhanced echocardiography when using high MI and end–systolic triggering. Users should take appropriate precautions in these circumstances and avoid cardiac examinations in patients with recent acute coronary syndrome or clinically unstable ischaemic heart disease. The use of contrast agents should be avoided 24 hours prior to extra-corporeal shock wave therapy.

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Appendix B

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Statement on the Use of Diagnostic Ultrasound for Producing Souvenir Images or Recordings in Pregnancy (2006)

Developments in real-time three dimensional ultrasonic imaging have led to parents asking for souvenir (keepsake) video recordings of the fetus, sometimes at several stages during the pregnancy. An area of concern is the growth of services designed to provide such images and recordings without any diagnostic element to the scan. Often, such services are unable to provide counselling or offer guidance if signs of a fetal abnormality are unexpectedly revealed. Apart from such services, there are many instances of diagnostic scans being prolonged in order to provide such recordings.

Very little information is currently available regarding possible subtle biological effects of diagnostic levels of ultrasound on the developing human embryo or fetus, and the possibility of developmental effects in the brain cannot be ruled out. There is evidence that diagnostic levels of ultrasound can influence development of the brain in small animals, although it is not possible to extrapolate this finding to the human situation. A balance must always be maintained between diagnostic benefit and risk to the patient. Therefore, it is difficult to justify souvenir or keepsake scanning that has no diagnostic benefit.

Recommendations:

1 Ultrasound scans should not be performed solely for producing souvenir images or recordings of a fetus or embryo.
2 The production of souvenir images or recordings for the parents to keep is reasonable if they are produced during a diagnostic scan, provided that this does not require the ultrasound exposure to be greater in time or magnitude (as indicated by the displayed MI and TI) than that necessary to produce the required diagnostic information.
3 Attention is drawn to the recommendation of the EFSUMB Clinical Safety Statement for Diagnostic Ultrasound that ultrasound examinations should be performed only by competent personnel who are trained and updated in ultrasound safety matters.