Imaging utilization on stroke patients is affected by age and imaging capacity — the number of magnetic resonance imaging (MRI) and computed tomography (CT) machines at any given facility, according to a study in the June issue of the Journal of the American College of Radiology (www.jacr.org).

Advanced medical imaging is a component of health care expenditure growth. Although there are many potential reasons for imaging growth, including that scans have been directly linked to greater life expectancy, declines in cancer mortality rates, and are generally less expensive than the invasive procedures that they replace, one of the major drivers of utilization may be enhanced imaging capacity available in most major metropolitan areas.

"To better understand some of the determinants of imaging ordering behavior, we analyzed the effect of differential capacity on the imaging workup of patients with acute non-hemorrhagic stroke," said Max P. Rosen, MD, MPH, lead author of the study. A "natural experiment" between the United States and Canada was performed.

Nine hundred eighteen patients at the U.S. hospital and 1,759 patients at the Canadian hospital were included in the study. We found that patient age and site (U.S. vs. Canada) were significant predictors of MRI use. Scanning utilization varied at hospitals with differential access to scanning technologies — there was less frequent use of MRI scanning at hospitals with limited access to this modality.

"Our study demonstrates that for patients presenting with symptoms of acute stroke, differences in scanning capacity (CT and MRI) may shape aspects of clinical management," said Rosen.