Radiology
Radiology coding hinges on a few structural concepts that recur across x-ray, CT, MRI, ultrasound, and nuclear medicine. Chief among them are the professional/technical split, the CPT definition of contrast, and the difference between complete and limited studies. Get these right and most radiology questions become straightforward.
Professional vs technical components
Diagnostic imaging codes often divide into two components. The professional component (modifier -26) captures the physician's supervision, interpretation, and written report. The technical component (modifier -TC) captures the equipment, supplies, film/media, and technologist. When a radiologist reads a study performed on a facility's equipment, the radiologist bills -26 and the facility bills -TC; a physician who owns the equipment and interprets the study may bill the global service with no modifier.
Contrast conventions and complete vs limited studies
CPT defines 'with contrast' as contrast administered intravascularly, intra-articularly, or intrathecally — contrast given only orally or rectally is coded as 'without contrast.' Studies performed first without and then with contrast have their own code choice. Separately, many ultrasound and imaging codes distinguish 'complete' from 'limited': a complete study requires documentation of every anatomic element the CPT guidelines list for that exam; if fewer elements are examined, the study is limited. Reading the guideline notes before assigning the code prevents overcoding.