The reasoning
- First‑line test: cheap, available, safe; may answer the question or triage (CXR, US, radiograph).
- Investigation of choice (IOC): best non‑invasive test for the specific question in usual circumstances.
- Gold standard: reference test (often invasive or historical: DSA, histology, catheter angiography).
- Modifiers: pregnancy (US, MRI without gadolinium), children (US, MRI, low‑dose), renal function (non‑contrast, CEUS, group II GBCA), allergy, implants, stability (treat first), availability and cost, radiation (justification), and evidence‑based guidelines (ACR Appropriateness Criteria, iRefer, ESR iGuide).