Background:
Appropriate use of medical technologies affects several aspects of clinical practice. Besides the analytical validity, examinations’ clinical usefulness and validity allegedly lead to better outcomes. Further, a reasonable ethical and economic approach contributes to improving healthcare delivery. Conversely, imaging overuse and low-value care dramatically drive up costs with scarce or no benefit for patients. The current research aims to assess a trend over a 10-year timeframe on the proportion between imaging tests and radiology devices in 16 countries belonging to the Organisation for Economic Co-operation and Development (OECD).

Methods:
A time-trend analysis based on OECD indicators on diagnostic imaging (Computer Tomography _ CT, Magnetic resonance imaging _ MRI, and Positron emission tomography _ PET) involved 12 European countries and four overseas countries. OECD indicators were annual number of exams per 1000 population, annual number of devices per million population and annual number of exams per device. Country-specific trend was measured as average annual percent change.

Results:
The trend exam-to-scanner ratio for CT, RMI and PET grew during the study-period in most of countries (11, 13 and 12, respectively). Predominantly, it highlighted a faster rise of exams’ amount than number of devices. During the same timeframe, Italy registered an increase of CT, MRI and PET units, although exams did not. However, the contraction of medical procedures during 2020 was crucial in defining this trend. Solely in Luxemburg, CT and PET examinations increased despite the reduction of scanners, whereas for MRI a reverse trend was reported.

Conclusion:
According to our analysis, the exam-to-scanner ratio has grown in most of the countries involved, accounting for a raised amount of both exams and devices. Overuse is likely to be increasing worldwide, however these trends may reflect defensive medical decision making, or rather an improvement of diagnostic supply in response to a higher demand.