Context: Excessive use of medical imaging increases health care costs and exposure to ionizing radiation (a potential carcinogen) without yielding significant benefits to all patients.

Objective: To determine whether there has been a change in the prevalence of emergency department visits for injury-related conditions for which computed tomography (CT) or magnetic resonance imaging (MRI) was obtained and whether there has been a change in the diagnosis of life-threatening conditions and patient disposition.

Design, setting, and participants: Retrospective cross-sectional analysis of emergency department visits using data from the National Hospital Ambulatory Medical Care Survey (1998-2007). Sampled visits were weighted to produce estimates for the United States.

Main outcomes measures: Proportion of visits for injury-related conditions during which a CT or MRI was obtained, a life-threatening condition was diagnosed (eg, cervical spine fracture, skull fracture, intracranial bleeding, liver and spleen laceration), and which resulted in hospital and intensive care unit admission.

Results: The prevalence of CT or MRI use during emergency department visits for injury-related conditions increased from 6% (95% confidence interval [CI], 5%-7%) (257 of 5237 visits) in 1998 to 15% (95% CI, 14%-17%) (981 of 6567 visits) in 2007 (P < .001 for trend). There was a small increase in the prevalence of life-threatening conditions (1.7% [95% CI, 1.2%-2.2%; 89 of 5237 visits] in 1998 and 2.0% [95% CI, 1.6%-2.5%; 142 of 6567 visits] in 2007; P=.04 for trend) [corrected].There was no change in prevalence of visits during which patients were either admitted to the hospital (5.9% [95% CI, 4.9%-6.9%] in 1998 and 5.5% [95% CI, 4.7%-6.5%] in 2007; P = .50 for trend) or to an intensive care unit (0.62% [95% CI, 0.40%-1.00%] in 1998 and 0.80% [95% CI, 0.53%-1.21%] in 2007; P = .14 for trend). Visits during which CT or MRI was obtained lasted 126 minutes (95% CI, 123-131 minutes) longer than those for which CT or MRI was not obtained.

Conclusion: From 1998 to 2007, the prevalence of CT or MRI use during emergency department visits for injury-related conditions increased significantly, without an equal increase in the prevalence of life-threatening conditions.