Radiographic Anatomy and Physiology
This domain tests normal radiographic appearances, surface and skeletal landmarks, organ position, and the physiological changes that alter images. Questions often ask you to identify a structure, side, plane or expected appearance on a standard projection.
Core rules
- Use anatomical position: the patient's right is on the viewer's left in a standard frontal image.
- Know the major body planes and directional terms: anterior, posterior, medial, lateral, proximal, distal, supine, prone, erect, decubitus.
- Skeletal anatomy includes bone types, joints, growth plates, and common variants. The thorax includes lungs, pleura, mediastinum, heart and diaphragm.
- Abdominal anatomy includes liver on the right, stomach and splenic flexure on the left, kidneys retroperitoneal, and bladder in the pelvis.
- Physiology affects appearance: inspiration lowers the diaphragm; gravity changes fluid levels; age changes bone density and growth plates.
Worked example
On an erect PA chest image, the gastric bubble appears under the left hemidiaphragm and the liver shadow under the right. If the image is marked as PA but the gastric bubble is on the viewer's right, first check marker placement and whether the image was flipped. Do not assume situs inversus without clinical correlation. The reasoning is that standard display places the patient's right on the viewer's left.
Traps
Do not confuse patient right with image right. Do not call every lucency an abnormality; bowel gas and breast shadow are normal. Do not assess rotation from a single clavicle. Remember that supine and erect images change air-fluid and free-gas appearances.