Head CT is an essential element of emergency department (ED) diagnosis and treatment of numerous neurologic emergencies. However, it is costly in aggregate, exposes patients to ionizing radiation, and can contribute to increased ED delays and length of stay. The objective of this study was to characterize head CT use in a nationwide sample of EDs between 2007 and 2022. This is a retrospective cohort analysis of the National Hospital Ambulatory Medical Care Survey (NHAMCS) database from 2007 to 2022. We used multivariable logistic regression to determine the odds of an ED encounter receiving a CT scan of the head, applying NHAMCS survey weights. Study exposures included year, patient demographics, and hospital characteristics. To explore differential trends over time, we created interaction terms between year and patient age, sex, and race/ethnicity. In 2007, the weighted number of ED encounters that received a head CT was 7,841,855 (95% CI 6,328,471-9,355,239), and by 2022, it had more than doubled to 15,977,551 (95% CI 12,343,286-19,611,816) (p < 0.001 for difference), representing an increase from 6.7% to 10.3% of ED encounters. We did not find a significant interaction between time (years) and sex, but the interaction between time and age was highly significant (p < 0.001). Patients aged 65 years or older had 6.24 (95% CI 5.66-6.88) times the odds of receiving a head CT compared with patients aged younger than 18 years after controlling for year, month, and chief concern at ED admission. Patients who were Black (OR 0.90, 95% CI 0.85-0.96), on Medicaid (OR 0.82, 95% CI 0.77-0.87), or from a rural hospital (OR 0.76, 95% CI 0.70-0.83) were less likely to receive a head CT. The overall number of head CT scans during an ED encounter increased more than twofold from 7.8 to 16 million during 2007-2022. Racial, insurance, and geographic variations continue to exist in head CT usage. Given increasing rates of head CT scans in the ED, additional evaluation of their yield in comparison with the relative risks and costs is needed.

A shortage of contrast material has made weighing value an urgent aspect of imaging decisions and provided a stark example of the consequences of low-value imaging for public health and health equity.