Medications used for diagnostic purposes help in imaging tests, identifying infections, and assessing organ function. Common classes include contrast agents and diagnostic agnets. Contrast agents like gadobutrol (Gadavist) are often used in MRI scans to help your radiologist identify abnormal itssues. Omnipaque (iohexol) is a contrast agent used during CT scans. Diagnostic agents like regadenoson (Lexiscan) are used in stress tests to test heart function.