Senior-clinician companion to introductory Radiology notes. Educational use only; imaging selection and interpretation require current guidance and qualified radiology support.
A Word From Your Senior
Imaging is not a fishing expedition. The safest scan is the one that answers a clinically important question, is suitable for this patient, and will change management.
Modalities and Trade-offs
Plain radiography uses ionising radiation and is excellent for many chest and skeletal questions but compresses three-dimensional anatomy into projections. Ultrasound uses sound, offers real-time and bedside assessment, and is operator- and window-dependent. CT uses ionising radiation to create cross-sectional data and is rapid, but radiation and iodinated contrast risks require justification. MRI uses magnetic fields and radiofrequency energy, provides strong soft-tissue contrast, and has important implant, foreign-body, monitoring, and access considerations.
Modality choice depends on urgency, suspected pathology, patient age, pregnancy, renal function where contrast is considered, implants, ability to cooperate, availability, and consequence of delay.
Before and After the Scan
Provide a focused clinical question, relevant history, examination, prior imaging, surgery, devices, pregnancy possibility, allergy details, and organ function as required. "Pain, please scan" transfers uncertainty rather than solving it.
After imaging, read the report in clinical context, review critical findings promptly, compare prior studies, clarify uncertainty with radiology, act on incidental findings appropriately, and ensure follow-up ownership. A report is a consultation, not a laboratory number.
Bedside Case
A patient has sudden focal neurological deficit. Activate the stroke pathway; establish last-known-well time, glucose, contraindications and severity while arranging protocol-defined imaging. A non-contrast CT may initially exclude haemorrhage without visibly confirming early ischaemia. Do not interpret "no acute finding" as "no stroke" without context.
Accuracy Guardrails
- MRI does not use ionising radiation, but it is not risk-free or always superior.
- Ultrasound cannot reliably exclude every deep or gas-obscured process.
- A negative study has meaning only for the question and test performance involved.
- Contrast reaction history should be characterised, not recorded vaguely as "iodine allergy."
- Use radiation principles of justification and optimisation; avoid both unnecessary exposure and harmful avoidance of indicated imaging.