This measure calculates the percentage of thorax computed tomography (CT) studies that are performed without and with contrast, out of all thorax CT studies performed (those without contrast, those with contrast, and those with both) at each facility. The measure is calculated based on a one-year window of Medicare fee-for-service claims data. The measure has been publicly reported annually by the measure steward, the Centers for Medicare & Medicaid Services (CMS), since 2010, as a component of its Hospital Outpatient Quality Reporting (HOQR) Program.