Radiographic Positioning and Radiographic Anatomy
Terminology
Position describes the patient's physical orientation; projection describes the path of the central ray. AP, PA, lateral, oblique, and tangential are projections. Decubitus is named by the side on which the patient lies.
Routine positioning
Chest PA: upright, 72 in SID, chin elevated, shoulders rolled forward, full inspiration, and no rotation. Rotation is judged by clavicle symmetry relative to the spinous processes. AP portable chest magnifies the heart and is reserved for patients who cannot stand. Abdomen: supine AP (KUB), erect, or decubitus for air-fluid levels. Extremities: include both joints when possible; use AP/PA, lateral, and oblique as indicated; center to the part and collimate. Spine: open-mouth odontoid, lateral C-spine, AP/oblique/lateral T- and L-spine; ensure true projections.
Anatomy landmarks
Know palpable landmarks (jugular notch, xiphoid, iliac crest, ASIS, greater trochanter) and which vertebral levels they approximate. Body habitus affects organ position and technique.
Traps
Do not confuse position with projection. A lateral chest is not automatically a left lateral. Rotation degrades positioning even when exposure is correct. Collimation should be to the region of interest, not the receptor.
Worked example: On a PA chest, unequal clavicle distances from the midline indicate rotation; correct before repeating.