Radiology and Diagnostic Imaging
Radiology tests systematic image interpretation, appropriate test selection, and awareness of radiation and contrast risk.
Core rules
- Chest radiograph: systematic ABCDE - airway, breathing (lungs), circulation (heart and mediastinum), diaphragm, everything else (bones, soft tissue, lines and tubes).
- CT head: acute blood is white; extradural is biconvex, subdural crescentic, subarachnoid blood fills sulci and basal cisterns.
- Test selection: ultrasound first for gallstones, DVT, and pregnancy; CT for trauma, suspected pulmonary embolism (with contrast), and acute abdomen; MRI for soft tissue and spinal cord.
- Contrast: check eGFR and metformin; premedicate prior reactors; avoid iodinated contrast in pregnancy unless essential.
- Radiation: justify every exposure - ALARA, especially in children and women of childbearing age.
Worked example
A 24-year-old after a motorcycle crash: stable, GCS 15, abdominal tenderness. Do not order a plain abdominal film. Perform FAST; if positive or the patient becomes unstable, proceed to contrast CT for solid-organ injury. Document the justification and shield where feasible.
Traps
- Missing a pneumothorax at the lung apex on a supine film.
- Requesting MRI in a patient with a pacemaker or intraocular metal.
- Declaring a film normal without checking lines, tubes, and blind spots (apices, behind the heart, costophrenic angles).
- Forgetting that an early normal CT does not exclude subarachnoid hemorrhage - lumbar puncture after 12 hours.