A total of 47 responses was received by the initial July 2021 deadline. Following a three-week extension and direct contact with national contact persons, an additional nine responses were received by the August deadline. Two of these responses were incomplete with no answers completed beyond the demographic questions; these responses were discarded, along with three duplicate responses (most recent submission retained), leaving 51 completed responses for analysis (82% response rate). Responses were received from 30 countries, including 25 from NRS and 21 from NCAs with at least one response received for all countries except Liechtenstein (Table 1).

Most respondents (n = 32, 63%) reported that guidelines are available on the implementation of regulatory requirements for justification of medical exposures and that roles and responsibilities of the referrer and the radiology practitioner for justification of medical imaging examinations are defined in national regulations (n = 38, 78%). Respondents who reported that guidelines were not available for justification of (CT) medical practices included NCAs in Cyprus, Denmark, Estonia, Greece, Hungary, Iceland, Lithuania, Romania, Slovenia and Sweden and additionally NRS in Austria, Belgium, Estonia, Greece, Portugal, Slovenia.

Specifically, regarding justification of CT examinations, when asked about whether justification of individual CT examinations was a legal requirement, just five respondents, namely the NRS from Austria, Belgium, Greece, Iceland and Portugal responded that it was not compulsory, with the majority answering that it was in all cases (n = 45, 88%). Similarly, just two respondents, the NRS from Belgium and Portugal, answered that CT referrals were not justified by a medical practitioner before the examination takes place with the majority indicating medical practitioner justification either in all cases (n = 24, 47%) or mostly (n = 19, 37%) (Fig. 1).

Are CT referrals justified by a medical practitioner before the examination takes place?

Radiologists alone predominantly (n = 27, 53%) made the final decision on justification of CT examinations daily (Fig. 2). However, this decision was reported by many countries to be a common effort between the radiologist and the referrer (n = 13, 26%), radiologist and the radiographer (n = 8, 16%) or all three professionals together (n = 2, 4%). One respondent (Slovakian NRS) stated that the referrer alone made the decision and another (Latvian NRS) that the radiographer alone did this. All respondents (n = 51, 100%) answered that the radiology practitioner has the legal right to change the CT referral to a more appropriate examination or to refuse a CT examination if the requested examination is inappropriate.

Who in daily practice makes the final decision on justification of CT examinations?

A range of imaging referral guidelines is available across countries, with European guidelines being most reported (n = 27, 55%) (Fig. 3). Just the Portuguese NRS and the Romanian NCA respondents reported that no referral guidelines were recommended nationally, although the Romanian NRS differed and reported that European guidelines were recommended. Respondents were asked about the availability of paediatric specific guidelines with just 24 respondents (49%) confirming their availability. Where guidelines were available, most respondents (n = 30, 61%) reported that they include information on radiation exposure. Guidelines were mostly available in electronic format across countries, with just 10 respondents (20%) reporting they were not, however only seven respondents (14%) from four countries stated that guidelines were incorporated into referral systems (clinical decision support), including NCAs from Ireland and Cyprus and both the NCA and NRS from Sweden and the UK.

Which of the following imaging referral guidelines does your country recommend?

Just six respondents (13%) believed that referral guidelines were in daily use by referrers / radiology practitioners (Fig. 4). These included the Finnish and German NCA, Italian, Latvian, Norwegian, Romanian and Slovak NRS. Most (n = 27, 56%) stated they were somewhat used daily.

To the best of your knowledge, are referral guidelines in daily use by referrers/radiology practitioners in your country?

When asked about justification of new practices, most respondents (n = 39, 77%) replied that responsibilities for justification of new practices (with CT) were regulated, and that responsibility for initiating the process of justification of a new practice varied widely, ranging from health authorities (n = 5, 10%) to individual health practitioners (n = 6, 12%), professional societies (n = 6, 12%) and undertakings/licence holders (n = 13, 26%). Belgium, Iceland and Portugal respondents reported not having any national system in place for (generic) justification of new types of classes of CT practices [12]. The most common mechanism used for justification of new types of practices was via evidence-based procedures conducted by national societies (n = 26, 51%) or local hospital mechanisms (n = 25, 49%). Health screening with CT was reported by just 20 respondents (Fig. 5), with the majority (n = 30, 59%) not having such screening in place. Health screening with CT was reported by three NCAs (Bulgaria, Czech Republic, United Kingdom) and five NRS (France, Norway, Poland, Spain, United Kingdom) as part of an approved screening programme. Eleven respondents reported that CT screening occurred outside of an approved screening programme (NCA: Belgium, Bulgaria, Greece, Hungary, Switzerland and UK; NRS: Austria, Finland, Portugal, Spain, Switzerland). However, responses differed between the NCA and NRS in seven countries (Belgium, Bulgaria, Czech Republic, Finland, France, Greece, Norway) about whether screening with CT took place in their country. In four of these countries, the NRS responded in the negative (Belgium, Bulgaria, Czech Republic, Greece).

Responses to whether health screening with CT takes place in your country?

Just three respondents (NCA: Finland, UK; NRS: Germany) reported that guidelines are available from relevant medical societies and the NCA regarding the use of imaging for asymptomatic individuals outside of approved screening programmes, with another nine stating they are partly available (NCA: Switzerland; NRS: Austria, Bulgaria, Finland, Ireland, Norway, Poland, Romania, Spain). Eleven of seventeen respondents who reported using CT for health screening did have national regulations, with seven stating that such regulations included provisions about advertisement of CT health screening practices and just three (NCA: UK, NRS: Finland, Poland) that regulations allowed self-presenting of asymptomatic individuals.

Respondents were asked whether any published audit/survey of the appropriateness of CT examinations had been carried out in their country in the past 10 years. Fifteen respondents from 11 countries (Croatia, Czech Republic, Estonia, Finland, France, Ireland, Italy, Luxembourg, Malta, Norway and Sweden), confirmed in the positive, while 10 did not know. Nine respondents provided links to these reported publications, three of which (Croatia [13], France [14], Ireland [15]) on further review were not specific to CT justification, while the Czech Republic, Estonian and Maltese audits were confirmed as unpublished audits. Respondents who reported a previous audit/survey of CT justification were also asked to identify any key outcomes/learnings from the audit, which are summarised in Table 2 below.

As anticipated, responses from within individual countries were not entirely consistent. When ‘I don’t know’ responses were disregarded it was noted that responses to specific questions varied when reported by the NRS or NCA, with a median of two different responses per country although this ranged from full agreement (zero differences: Denmark, Estonia) to seven different responses (Belgium).