Technologies play an important role in medical diagnoses: from physical examination and results processing and sharing, to accessing patients’ health records, to the review of clinical histories. However, new technologies are acknowledged as a major cost driver in health systems (Lorenzoni et al., 2019[1]). This section presents data on the availability and use of three diagnostic imaging technologies: computed tomography (CT), magnetic resonance imaging (MRI) and positron emission tomography (PET). CT and MRI examinations (exams) both show images of internal organs and tissues, while PET scans show other information and problems at the cellular level.
There is no general guideline or international benchmark regarding the ideal numbers of CT scanners, PET scanners or MRI units. Too few units may lead to access problems in terms of geographical proximity or waiting times, while too many may result in overuse of these costly diagnostic procedures, with little if any benefit for patients.
Availability of CT and PET scanners and MRI units has increased rapidly in most OECD countries over the past few decades. Japan had by far the highest number of CT scanners and MRI units, and the third highest number of PET scanners per capita. Australia had the next highest number of CT scanners; the United States the second highest numbers of MRI units and PET scanners; and Denmark the highest number of PET scanners per capita (Figure 5.23). The combined numbers of these three diagnostic technologies were also substantially higher than the OECD average in Korea, Greece, Italy and Germany; and much lower than average in Costa Rica, Colombia and Mexico.
Data on the use of diagnostic scanners are available for 30 OECD countries. Taken together, the use of CT, MRI and PET diagnostic scanners was highest in the United States, Luxembourg, Korea, France and Austria, all of which had a combined total of over 360 exams per 1 000 population in 2021 (Figure 5.24). The use of these three diagnostic exams was lowest in Costa Rica and Chile; and also in OECD accession countries Romania and Bulgaria. There are large variations in the use of CT scanners and MRI units, not only across but also within countries – for example, in Belgium, recent analysis showed a 50% variation in use of diagnostic exams of the spine across provinces in 2017, and this variation was even larger across smaller areas (INAMI/RIVIZ, 2019[2]).
Looking at trends over time, large increases in CT and MRI exams per 1 000 population can be seen in a number of countries up to 2019 (Figure 5.25 and Figure 5.26). For example, the number of CT exams more than doubled in Korea, and the number of MRI exams more than doubled in Australia, Korea and Slovenia.
Clinical guidelines exist in several OECD countries to promote more rational use of MRI and CT exams. Through the Choosing Wisely campaign, which began in the United States in 2012 and has since been emulated in a growing number of countries, some medical societies have identified cases when an MRI or CT exam is not necessary. For example, the Royal College of Physicians in the United Kingdom recommends, based on evidence from the National Institute for Health and Care Excellence (NICE), that patients with low back pain or suspected migraine do not routinely need an imaging test (Choosing Wisely UK, 2018[3]).
Despite the general upward trend in the use of diagnostic technologies over time, there were drops across many OECD countries between 2019 and 2020, particularly for MRI exams. Such reductions were due to health providers being forced to delay or cancel diagnostic exams early in the COVID‑19 pandemic. In the United States, the reduction was particularly large (over 30%). In 2021, however, diagnostic exams increased, and were typically above 2019 levels.
