X-ray diagnostics: Frequency and radiation exposure of the German population

X-ray examinations always involve some, albeit low, radiation risk. Therefore, the number of examinations performed as well as the associated radiation exposure for the German population are regularly assessed. This data is collected, evaluated and evaluated for each calendar year in order to be able to identify trends over time. The evaluations are carried out at least every two years.

How is the frequency of X-ray examinations estimated?

When physicians’ services are billed, reference is made to specific codes of reimbursement catalogues. These codes describe all services provided by the physician, including radiological procedures. They are well suited to estimate the frequency of X-ray examinations, since approximately 98 % of the general population in Germany have statutory or private full-cover health insurance. The most important sources for X-ray frequency estimates, therefore, are the health insurance companies.

For inpatients, valid data on hospital statistics published by the Federal Office of Statistics are available since 2007. Further, data from research studies are included.

How is the radiation exposure from X-ray diagnostics estimated?

To estimate the level of collective effective dose (collective dose), the frequency of each type of examination is multiplied by the corresponding estimated mean effective dose from that type of examination, and the products obtained for each type of examination are added up.

Annual population numbers of the German population are used to calculate the mean effective dose per per inhabitant and year.

Figure 1: Frequency of X-ray examinations in Germany

Results of the present evaluation

Frequency

In 2021, approximately 125 Million X-ray procedures were performed (excluding dentals: about 75 Million). The frequency of X-ray examinations in Germany was on average about 1.6 examinations per inhabitant and year during 2007 and 2021 (Figure 1). Around 80 % of all X-ray procedures are carried out in outpatient settings, of which around 90 % are performed on patients with statutory health insurance. In the outpatient sector, the total number of X-ray applications decreased slightly between 2007 and 2021. There was a noticeable decrease in frequency in 2020 due to the COVID-19 pandemic, followed by a subsequent increase in 2021.

Dental X-ray examinations

About 40 % of the total number of X-ray examinations in 2021 were dental (including orthodontics) (Figure 2). The frequency of dental X-ray examinations has remained largely unchanged over the years. However, the number of orthodontic x-rays, which now account for almost 25 % of all dental x-ray examinations for people with statutory health insurance, has increased.

Other conventional X-ray examinations

Figure 2: Contribution of various examination types to total frequency (left panel) and to collective effective dose (right panel) in 2021

Apart from dental examinations, X-rays of the skeleton (that is, skull, shoulder girdle, spine, pelvic girdle, limbs) and chest (thorax) accounted for most of all X-ray examinations (Figure 2). The number of most conventional X-ray examinations, for example of skull, thorax, and spine, decreased considerably in 2007-2021.

Due to the introduction of the German Mammography Screening Programme (MSP), the frequency of mammograms increased between 2007 and 2009 by 35 per cent, and was – after a slight decrease – nearly constant since 2011 (except for a pandemic-related decline in 2020).

Computed tomography (CT)

The frequency of CT examinations has increased considerably between 2007 and 2021 (Figure 1). For outpatients, the increase was about 25 %, for inpatients the frequency of CT examinations even doubled between 2007 and 2021. While the vast majority of all conventional X-ray examinations are performed in outpatients, about half of all CT are carried out in hospitals. A considerable increase in the frequency of examinations can also be observed in magnetic resonance imaging (MRI), that is, another diagnostic procedure that also provides three-dimensional detailed images but does not use ionising radiation.

Dose

Figure 3: Mean annual per caput effective dose (mSv) due to x-ray diagnostics in Germany

The 2021 estimate for the mean effective dose per caput is about 1.4 millisievert (mSv) in Germany (Figure 3). The mean effective dose from CT examinations per inhabitant and year has increased over time, although this increase is more moderate than the corresponding increase in CT frequency due to the decreasing dose per CT examination over the years.

By contrast, the annual per caput dose from other imaging procedures decreased slightly between 2007 and 2021 (Figure 3). In the outpatient sector, the per caput dose from conventional X-ray examinations has almost halved between 2007 and 2021.

As expected, the relative contribution of conventional X-ray examinations to the collective effective dose is relatively low. For example, this is only around 6 % for examinations of the skeletal system, although the proportion of the frequency is around a quarter. CT examinations, as well as angiography and interventional procedures of blood vessels, which are also associated with relatively high radiation doses, contributed just 15 % to the total frequency of examinations but made about 85 per cent contribution to the total collective effective dose in 2021 (Figure 2).