National survey of Australian sonographer knowledge and behaviour surrounding the ALARA principles when conducting the 11–14‐week obstetric screening ultrasound

Abstract

Objectives

To identify gaps in Australian sonographer's knowledge and application of as low as reasonably achievable (ALARA) principles during first trimester imaging; Identify relationships between demographic variables and knowledge or application of the Output Display Standard (ODS) value thermal index (TI) and compare Australian sonographers to their international peers.

Methods

Australian Sonographer Accreditation Registered ( ASAR)‐registered sonographers completed a voluntary questionnaire over September 2015 after institutional ethics approval (RDSE‐48‐15). Seventeen questions detailed their demographics (5); knowledge of ultrasound bioeffects terminology and ALARA principles (9); behaviour surrounding ALARA and first trimester imaging (2) and continuing bioeffects education (1). Exclusion criteria was non‐ASAR status. Descriptive (mode frequency) and inferential statistics (Fisher exact test) were used. Significance level was 95%.

Results

Ninety‐five valid surveys were collected. Ninety‐nine per cent knew the meaning of ALARA, 93.55% correctly defined ‘TI’ and 85.39% knew where to find the TI value via the ODS. Half never monitor the ODS. No correlation (P = 0.094) was found between experience and ODS monitoring. No statistical difference (P = 0.189) existed between obstetric and non‐obstetric sonographers who knew the meaning of TIB (87.18% vs. 76.92%) or those who correctly identified it as the setting for 11–14‐week examinations (30.77% vs. 30.77%). When using Doppler during obstetric examinations, no difference existed (P = 0.293), between obstetric and non‐obstetric sonographers’ knowledge of ASUM/WFUMB guidelines for maximum TI (47.37% vs. 46.15%).

Conclusions

Despite poor ODS usage, Australian sonographers outperform their international peers for ALARA literacy, and show better application of ALARA principles in the first trimester. No relationships were found between demographic variables and knowledge or conscious monitoring of ODS.

Introduction

Diagnostic medical sonography has not been associated with deleterious effects in human tissue.1 It is considered safe when used by trained individuals to seek relevant diagnostic information.2 There is total acceptance within the medical fraternity and compliance within obstetric patient populations as a first trimester screening tool for structural and chromosomal abnormalities.3

Applying principles of ‘as low as reasonably achievable’ (ALARA) requires the operator to use the lowest possible acoustic outputs to obtain diagnostically useful images.4 Sonographers must be familiar with ALARA, understand potential bioeffects and biohazards that may occur due to ultrasound exposure, and how to quantify that exposure using the output display standard (ODS) values of mechanical index (MI) and thermal index (TI).

Development and sophistication of detection in epigenetics, fetal programming, deoxyribonucleic acid methylation, telomere shortening and cell apoptosis, should serve to remind us that biohazard events may be occurring even if we are not observing them contemporaneously.5, 6

Protocols, measurements and novel sonographic soft signs are being encouraged that impose longer dwell times necessitating the use of higher energy modes (such as pulsed Doppler) on low risk first trimester fetuses.7 Protocols for 11–14‐week aneuploidy screening including ductus venosus pulsatility index for veins (DV‐PIV) measurement do not comment on or allow provision for ALARA or ODS observation.8 This is not consistent with ALARA principles for low‐risk pregnancy and contrary to World Federation for Ultrasound in Medicine and Biology (WFUMB) safety statements.

Review of the literature in October 2015 reveals no published studies outlining knowledge and behaviours of Australian sonographers with respect to ultrasound bioeffects and ALARA principles. Previous studies show varying levels of bioeffects language literacy and familiarity of the machine displays that inform good ALARA behaviour among end‐users (see Figure 2).

Our purpose was to examine Australian sonographer knowledge and application of ALARA principles. We sought to quantify self‐reported adherence to ALARA principles and identify if any relationships exist between years of experience, qualification vehicle, ultrasound specialty, and the knowledge and conscious monitoring of ODS value TI. We hoped to establish if a difference exists between Australian sonographers and their international peers with reference to knowledge and practice of ultrasound bioeffects and ALARA principles when conducting first trimester obstetric imaging.

Background

In sonography, we concern ourselves with two potential bioeffects: heating effects and mechanical effects.4 Potential heating is described by the TI. The TI is the ratio of total acoustic power to the acoustic power required to raise tissue temperature by 1°C under certain assumptions made by the machine manufacturers.4 The MI attempts to describe the peak rarefaction pressure, or the pressure exerted on gas bubbles within tissue that may be sufficient to cause cavitation or collapse of the bubbles and potential physical damage.4 In obstetric ultrasound, only the TI is monitored as there are no gas bubbles considered present.9

In 1992, the American Institute of Ultrasound in Medicine and the National Electrical Manufacturers Association introduced the Standard for Real‐Time Display of Thermal and Mechanical Acoustic Output Indices on Diagnostic Ultrasound Equipment referred to as the ODS.10 The United States of America (US) Congress enacted this into law and the US Food and Drug Administration (FDA) implemented it via their 510(k) document.11 The ODS attempts to address the issue of end‐user awareness and provides information on potential for bioeffects to the end‐user.1 The 510(k) document places the burden of responsibility upon the operator to be aware of potential bioeffects, formally including ALARA principles into diagnostic medical sonography culture. We expect the operator to be familiar with accepted MI and TI values and recommended maximum imaging times as set by WFUMB.12

Applying the ALARA principle to ultrasound requires the sonographer to bear the responsibility for minimising potential risk or harm to the patient while ensuring maximum diagnostic quality and information.13 Sonography equipment manufacturers who wish to sell into the US comply with this document. Many industry bodies acknowledge the burden of responsibility on the end‐user in their safety statements.14

Ultrasound education in Australia is highly regulated by both government and industry. To date, most Australian‐trained sonographers have come from an undergraduate medical radiation background.15 Ionising radiation imaging sciences have always been educated in the principles of ALARA.4 The term ALARA was first introduced into radiography in 1973 by the International Commission on Radiological Protection via Recommendation 22.16 The concept was adopted into ultrasound culture from the medical imaging sciences of radiography and nuclear medicine, where the well‐defined and measureable risks of exposure to ionising radiation have been extensively researched.17 The ubiquitous and seemingly benign nature of ultrasound imaging, coupled with undergraduate sonographer training programs that now exist within Australia may mean that new sonographers do not inherit such a strong sense of responsibility to ALARA principles.

In Australia, an Australian Sonographer Accreditation Registered (ASAR) practitioner must perform the ultrasound examination to obtain remuneration for the service via the sovereign‐backed medical health care payment system Medicare.18 This requirement helps to maintain the educational standards for practitioners/sonographers and creates assumptions about their knowledge of ALARA principles and ultrasound bioeffects and safety. ASAR accreditation is available to students enrolled in an ASAR‐accredited sonography course or those who have successfully completed an ASAR‐accredited postgraduate program. One of the requirements for program accreditation by ASAR is the inclusion of ultrasound physics, ultrasound bioeffects and biohazards, and the principles of ALARA.19

Methods

Non‐high risk ethics approval was given by Curtin University Human Research Ethics Committee20 for a cross‐sectional survey of Australian accredited sonographers.

The population was ASAR‐registered diagnostic medical sonographers (approximately 5000 in 2012).21 Of this, approximately 13% are students.

The survey frame was ASUM (approximately 3600)22 and ASA (approximately 3500)23 active members. Membership is voluntary. Many sonographers will be members of ASA and ASUM as well as their compulsory registration with ASAR. Permission was sought from these two peak industry bodies for sonography in Australia to provide information and access to the unique survey uniform resource locator link on their regular email newsletters. An introductory letter, along with consent document and ethics approval number were provided on the survey site. Consent was obtained via digital acceptance of the study information contained within the introductory letter.

Participants were excluded if not ASAR‐accredited at the time of the survey.

Sample size was set at 100 to be achievable within the time frame and still maintain a valid survey size to satisfy 10% margin of error and 95% confidence interval.24

A voluntary, self‐completed, anonymous, untimed, electronic questionnaire created using the online provider Survey Monkey (http://www.surveymonkey.com) was available over a one‐month period in September 2015. Respondents completed 18 questions. Questions were divided into categories.

Five questions sought demographic information (Table 1). Nine questions were designed to assess knowledge of key bioeffects terminology and maximum ODS values recommended during first trimester imaging (Table 2). Two questions queried behaviour related to ALARA principles during first trimester imaging (Table 3) and one question asked about knowledge of, or participation in bioeffects continuing education (Table 4).

Table 1.

Demographic information for Australian sonographers

Question	Frequency n (%)
Demographics
Pathway to ASAR accreditation (n = 95)
ASUM DMU	28 (29.47)
University	55 (57.89)
Recognised international qualification	3 (3.16)
Grandfathered	0 (0.00)
Student sonographer	9 (9.47)
Number of years practicing sonography (n = 94)
Student	11 (11.70)
0–1	0 (0.00)
2–5	15 (15.96)
6–10	18 (19.15)
11+	50 (53.19)
Practice and specialty information
Two leading studies performed regularly (n = 93)
Obstetric & Gynaecologic	52 (55.91)
Vascular	10 (10.75)
Musculoskeletal	31 (33.33)
Abdomen	49 (52.69)
Cardiac	2 (2.15)
Small parts	9 (9.68)
Not currently working	10 (10.75)
Active obstetric scanning (n = 89)
Never	13 (14.61)
Only dating scans	19 (21.35)
Only 11–14‐week nuchal translucency (NT)	0 (0.00)
Only 2nd and 3rd trimester	18 (20.22)
All including 11‐14‐week NT scans	39 (43.82)
Obstetric scanning location (n = 93)
Public Hospital	10 (10.75)
Private radiology practice	55 (59.14)
Private obstetric practice	8 (8.60)
Both public and private practice	8 (8.60)
I never perform obstetric scans	12 (12.90)

Table 2.

Ultrasound bioeffects knowledge of Australian sonographers.^a

Question	Frequency n (%)
Terminology
ALARA with reference to medical imaging (n = 93)
Action Learning Action Response Association	0 (0.00)
Australian Ladies Amateur Radio Association	0 (0.00)
As Low as Reasonably Achievable	92 (98.92)
I do not know	1 (1.08)
What is TI? (n = 93)
Thermal Intensity	2 (2.15)
Temperature Index	2 (2.15)
Thermal Index	87 (93.55)
Temperature intensity	1 (1.08)
I do not know	1 (1.08)
What does the ‘S’ stand for in TIS? (n = 93)
Standard	27 (29.03)
Simple	0 (0.00)
Soft tissue	59 (63.44)
Standard tissue	3 (3.23)
I do not know	4 (4.30)
What does the ‘B’ stand for in TIB? (n = 93)
Brain	3 (3.23)
Bone	73 (78.49)
Blood	5 (5.38)
Baby	2 (2.15)
I do not know	10 (10.75)
What does the ‘C’ stand for in TIC? (n = 91)
Cardiac	16 (17.58)
Cranial	58 (63.74)
Coronal	0 (0.00)
Chest	1 (1.10)
I do not know	16 (17.58)
If you want to know what the TI or MI values are during an examination, what do you do? (n = 89)
Look it up in a textbook/internet	1 (1.12)
Calculate it from the frequency of the transducer I am using	2 (2.25)
Read it off the monitor during the examination	76 (85.39)
Refer to the manufacturer's manual	2 (2.25)
I do not know	8 (8.99)
Guidelines
Output display standard index that should be monitored during the nuchal translucency scan (11‐14 weeks) (n = 89)
TIS	29 (32.58)
TIB	25 (28.09)
TIC	8 (8.99)
MI	8 (8.99)
I do not know	19 (21.35)
ASUM recommended maximum TI when using Doppler mode in obstetric scanning (n = 85)
4.2	0 (0.00)
1.0	27 (31.76)
1.9	16 (18.82)
3.5	4 (4.71)
I do not know	38 (44.71)
WFUMB/ISUOG recommended maximum exposure times when using Doppler mode in obstetric imaging (n = 83)‐more than one response allowed
Five minutes	15 (18.07)
Ten minutes	6 (7.23)
Maximum of 60 min	8 (9.64)
5–10 min	14 (16.87)
No time limit, but only use when clinically indicated	30 (36.14)
I do not know	23 (27.71)

^aCorrect answer is in bold.

WFUMB, World Federation of Ultrasound in Medicine & Biology; ISUOG, International Society of Ultrasound in Obstetrics & Gynaecology.

Table 3.

Behaviour of Australian sonographers with respect to ALARA principals

Question	Frequency n (%)
How often do you perform pulse Doppler studies during the nuchal translucency scan? (n = 89)
Always perform ductus venosus (DV)	8 (8.99)
Always perform tricuspid regurgitation (TR) assessment	0 (0.00)
Always perform DV and TR	6 (6.74)
Never perform pulse Doppler	20 (22.47)
I only perform Doppler studies if indicated on the referral	14 (15.73)
I never perform nuchal translucency scans	41 (46.07)
When do you monitor the TI or MI during an examination? (n = 89)
Never	45 (50.56)
Only during obstetric studies	17 (19.10)
Only when doing neonatal head studies	6 (6.74)
Only when performing contrast studies	0 (0.00)
Only when performing fetal cardiac studies	2 (2.25)
When performing all studies	19 (21.35)

Table 4.

Continuing medical education of Australian sonographers with respect to ALARA principals

Question	Frequency n (%)
Completed bioeffects in ultrasound continuing educational activities (n = 82)
Still a student	13 (15.85)
No, I have never seen any	48 (58.54)
No, but I am aware of bioeffects educational activities	4 (4.88)
Yes, at a conference	6 (7.32)
Yes, through online continuing medical education (CME)	7 (8.54)
Yes, through journal articles	13 (15.85)

One question was to ascertain ASAR status. Participants were excluded if not ASAR registered at the time of the survey. All knowledge questions included the option of ‘I do not know’ to discourage guessing. Question skipping was not allowed, although some respondents did not complete all questions. Missing data fields were removed for statistical analysis.

All questions were designed to collect categorical data. One demographic question (Q. 3 – number of years practicing sonography) was continuous (or quantitative) so categorical values were created by grouping years of practice. The groupings were student; 0–1; 2–5; 6–10, and 11+ years. We designed the groupings to identify when, if any degradation of knowledge or behaviour occurred.

External evaluation for face validity of the survey instrument was performed by a small pilot study of two sonography (both clinically active with 20+ years of experience, one academic and one non‐academic) and two non‐sonography medical imaging professionals (one radiography academic, 10+ years of experience, one nuclear medicine qualified industry professional, 20+ years). There were two rounds of review.

Survey responses were analysed using stata 13 statistical software (StataCorp LP, Texas Station, TX, USA). Descriptive statistics were used to calculate percentage of frequencies for all categorical variable. Cross‐tabulation was used to analyse control demographic categorical variables with dependent bioeffects knowledge categorical variables. Inferential statistical analysis (Fisher exact tests) was performed on cross‐tables to determine whether there is a significant difference between the expected frequencies and the observed frequencies in one or more categories that may indicate a dependency. The level of significance, α was set at 95% for all statistical analyses.

We compared our findings with those from similar studies.2, 25, 26, 27, 28, 29, 30, 31

Results

One hundred and three respondents in total completed the survey. Eight respondents were ineligible due to no ASAR registration. Of the 95 remaining respondents, 71 (74.74%) completed the survey in under 10 min, with 82 (86.32%) completing in less than the 15 min. Only five (5.26%) respondents took greater than 30 min.

Table 1 shows the pathway taken to gain ASAR accreditation; years of clinical experience; clinical examinations performed regularly and practice type.

Table 2 shows Australian sonographer knowledge of bioeffects language and industry guidelines.

In our study, 28.09% knew that TI for bone (TIB) was the correct ODS for the 12–14‐week examination. No statistical difference was found (P = 0.189) between obstetric sonographers only (n = 39), and sonographers who never perform obstetric imaging (n = 13), with 87.18% (34) vs. 76.92% (10) knowing the meaning of TIB, but only 30.77% in each group (12 vs. 4) correctly identified it (Figure 1).

Figure 1.

Obstetric vs. non‐obstetric sonographers ALARA language literacy.

We found 47.37% (18) of obstetric sonographers (n = 39) did not know the ASUM/WFUMB guidelines for maximum TI values when using pulsed Doppler during obstetric examinations. No statistical significance (P = 0.831) existed between obstetric and non‐obstetric sonographers with 28.95% (11) vs. 30.77% (4) correctly identifying the maximum value at 1.0 (Figure 1).

Table 3 details the behaviour of Australian sonographers with respect to the ALARA principles.

No correlation (P = 0.094) was found between number of years of practice and ALARA complacency levels with 54.33% (25) of sonographers having over 11 years of experience never monitoring the ODS for any examination compared to 46.51% (20) for every other group.

Of the 43.83% (39) sonographers performing 11–14‐week nuchal translucency (NT) examinations, 94.87% (37) knew the definition of TI, but 49.72% (19) never monitor the ODS for TI, regardless of the examination type (Table 4; Figure 2).

Figure 2.

Obstetric vs. non‐obstetric sonographers ALARA behaviour.

Discussion

Previous studies show the average knowledge of where to find TI on the ultrasound machine is 36.45% (13.00–80.00%) (Table 5). Due to bias (voluntary, non‐blinding, self‐reporting, untimed) the knowledge among the broader international ultrasound end‐users may be even worse.32 Australian sonographers know the meaning of TI, and outperform their international peers on where to find it on the machine display.

Table 5.

Summary of previous DMS end‐user response to questions regarding ODS

Article	Familiar with the term ‘TI’ (%) (% able to describe TI)	Knew where to find output display standards on their ultrasound machine (%)
This study	Not asked (93.55)	85.39
Akhtar et al.25	33.70 (19.20)	13.00
Bagley26	Not asked	52.00 Based on the questionnaire question: How many times per scan do you monitor the TI/MI
Sheiner2	32.20 (17.70)	20.80
Marsal28	32.00 (22.00)	28.00
Houston et al.27	19.60 (not given)	20.20
Necas 201029	15.00 (15.00)	80.00
Piscaglia30	Not given (93.80)	53.60
Indrielle et al.31	Not asked (69.00)	24.00 Based on practitioner utility of output display standards

TI, thermal index; MI, mechanical index.

Prior to 10 menstrual weeks’ gestation, TI for soft tissue (TIS) is used. Thereafter, bone ossification is evident and the TIB may monitor potential thermal effects.9 Debate exists over the value of TI that should be used to limit risk but a TI of <0.5 to 0.7 is considered safe for an ‘extended’ period of scanning.14

Bromley et al.33 show these guidelines are either not disseminated widely or effectively, or practitioners choose to ignore them. Only 19.5% of images they reviewed had used the correct ODS during 11–14‐week imaging.

We found poor knowledge among sonographers of ODS for 12–14‐week imaging, but no statistical difference between those who perform the examination and those who never do.

Sheiner and Abramowicz34 found values of TI displayed via ODS when performing the 11–14‐week fetal examination including NT measurement within the morphologically normal fetus very low (TI range 0.1–0.7, μ = 0.2) showing 2D ultrasound follows the ALARA principles by collecting valuable data for the calculation of risk profiles using NT measurement, crown rump length and maternal age.

World Federation for Ultrasound in Medicine and Biology note that spectral and power Doppler may increase the TI significantly and should only be used in the first trimester if clinically indicated, i.e. not low risk.14 The addition of DV‐PIV in low‐risk fetuses may not significantly improving detection rates for aneuploidy.8

We found nearly half of the obstetric sonographers questioned did not know the guidelines when using pulsed Doppler during obstetric examinations. Again, no statistical significance was found between obstetric and non‐obstetric sonographers suggesting a need to tailor continuing medical education (CME) towards obstetric sonographers in particular.

Examining attitudes and behaviours of sonographers performing Doppler studies during the first trimester (n = 48), we found 41.67% (20) of sonographers who did nuchal translucency scans never perform any pulsed Doppler during the examination, 29.17% (14) only performing them if indicated by referral. Our study does not assess the motivation behind the behaviour but shows moderate adherence to guidelines. Medicare guidelines may encourage these measurements to be performed during one examination to prevent over‐servicing.

Response rate was difficult to calculate, but the worst estimate is 2.64%. There was no way of knowing how many received the industry e‐newsletters, opened them, or continued on to the survey link. Piscaglia et al.30 anecdotally justified their poor response rate because their sample population ‘…did not consider the topic important enough to justify the time spent answering the questionnaire’. This may also be the case here.

Peer assistance may have been used as some questionnaires came from the same IP address, suggesting multiple users at a worksite. Over the month, some learning bias may have developed to skew the results.32 Completion was voluntary so selection bias also exists, implying that population user knowledge may be lower than shown here. Respondents may have reported an idealised or exaggerated reality with regard to their ALARA behaviours.32 Of the 95 valid responses, 74.74% completed the survey in under 10 min, with 86.32% completing in less than the 15 min time limit allowed by Marsal28 in his seminal study of ultrasound operator knowledge. This period gives validity to our data, suggesting respondents limited their fact checking while completing the survey. Only 5.26% respondents took greater than 30 min.

The Fetal Medicine Foundation (London, UK) first trimester protocols and protocols for 11–14‐week aneuploidy screening including DV‐PIV measurement do not comment on or allow provision for ALARA or ODS observation.8 This is contrary to WFUMB safety statements.

Previous studies show international operators are aware of potential bioeffects when using Doppler during the first trimester with an average of 50.1% (36.2–76.6%) considering 2D always safe, compared to Doppler ultrasound at 21.5% (19.2–23.6%).2, 25, 26, 27, 28, 29, 30 It is interesting to note that despite this, in the two studies where the respondents were asked their opinion on ‘keepsake’ imaging (non‐medically indicated or social), the disapproval rates were 71.1%25 and 69.2%.2

Spectral and power Doppler may increase the TI significantly and we should only use it in the first trimester if clinically indicated.4 Piscaglia et al.30 asked respondents to show an understanding of WFUMB imaging guidelines and received a 42.3% correct response rate. Australian sonographers are following both international guidelines and ALARA principles by minimising exposure of the first trimester fetus to Doppler imaging without warrant.

The ultrasound machine may start up on maximum power to optimise sensitivity, leaving the user to monitor and reduce output levels when necessary.29 FDA guidelines recommend that ODS should be displayed but do not suggest where or how this is to be achieved.11 Sande and Kiserud35 showed absent or very little effect on visualisation of the fetus by increasing output intensity. Higher power output may be necessary with increasing maternal body habitus within the Australian population.36 This may be an area that requires continuing educational support to help sonographers make informed choices that adhere to ALARA principles during first trimester imaging.

Two previous studies report advanced levels of experience led to greater levels of complacency with regard to monitoring ODS indices and attitudes to potential bioeffects to the fetus when using Doppler ultrasound in the first trimester.25, 27 Necas29 reports no sonographers with >10 years’ experience could define or describe TI but 100% of respondents self‐reported familiarity with TI, indicating a lack of information retention. We found Australian sonographers have good information retention of TI knowledge regardless of time since qualification (P = 0.366).

Revisiting this question in some years’ time when more Australian sonographers have come from a background other than ionising radiation medical imaging may show if they have primarily inherited and maintained their ALARA awareness and culture from their undergraduate education. Certainly, poor CME in this area is not affecting knowledge retention.

Application of ALARA principles within the Australian sonographer population is hindered by poor knowledge of peak industry body guidelines. Limited motivation of adherence to ALARA principles and low awareness of, or involvement in (CME) opportunities may be the cause.

Future research may focus on educational vehicles to establish if Australian sonographer levels of bioeffects knowledge and behaviours are inherited from their historically high background in ionising radiation medical imaging.

Industry‐wide assessment of sonographers could be used to discover behaviour deficits, and this knowledge could be used to create voluntary or compulsory (CME) material.