To compare the intensity of imaging utilization globally. To evaluate the potential effect of wealth and population density on this utilization.

Data regarding the number of radiography, mammography, CT, MR, US and nuclear medicine units and procedures for 2001 was obtained from 14 nations in the North American (3), South American (1), Asian (4), and European (6) continents. Data was obtained from the databases of Frost & Sullivan. Data on GNI/capita, purchasing power parity (PPP) and population density (PD) was obtained from the World Bank 2002 and encyclopedia Wikipedia respectively.

Unit utilization was calculated for the 6 modalities by dividing the total exams by number of units. Unit utilization was divided by PD and PPP to determine relative utilization. Utilization was then divided by US data to create normalized ratios.

Compared to the US, a higher number of exams/unit was performed in Europe (x-ray 1.8 +/- 0.4, mammo 3.7 +/- 4.5, CT 1.1 +/- 0.3, MR 1.7 +/- 0.5, US 1.8 +/- 0.9, NM 1.8 +/- 0.3) and a lower number in Asia (x-ray 1.0 +/- 0.1, mammo 0.1 +/- 0.1, CT 0.5 +/- 0.2, MR 0.3 +/- 0.2, US 0.4 +/- 0.2, NM 0.9 +/- 0.6). Excluding CT and NM, a higher number of exams/unit was also performed in Brazil and Mexico.

Standardizing for PD lowered relative utilization in Europe (x-ray 0.7 +/- 0.7, mammo 0.4 +/- 0.3, CT 0.4 +/- 0.3, MR 0.5 +/- 0.4, US 0.4 +/- 0.3, NM 0.6 +/- 0.5) and Asia (x-ray 0.1 +/- 0.1, mammo 0.02 +/- 0.03, CT 0.04 +/- 0.03, MR 0.03 +/- 0.04, US 0.05 +/- 0.05, NM 0.1 +/- 0.1). The UK served as an outlier with relative utilization paralleling the US.

Standardizing for PPP also lowered relative utilization in Europe (x-ray 0.5 +/- 0.2, mammo 0.4 +/-0.2, CT 0.3 +/- 0.2, MR 0.4 +/- 0.3, US 0.6 +/- 0.5, NM 0.5 +/- 0.5) and Asia (x-ray 2.2 +/- 2.6, mammo 0.1 +/- 0.2, CT 0.3 +/- 0.3, MR 0.3 +/- 0.3, US 0.5 +/- 0.5, NM 0.9 +/- 1.1). Relative utilization standardized by income in Brazil, Mexico and Canada was highest at 5-10 times greater than the US.

The US ranks low among industrialized nations in imaging unit utilization. Analysis of utilization by national income and PD provides comparative global data on imaging unit productivity.

C.Z.: Siemens employee