Advanced imaging is one of the most-denied prior authorizations — but the rule is remarkably consistent. It almost never turns on the CPT code. It turns on two things: is there a red-flag finding (which fast-tracks the scan now), and if not, is there a documented conservative-care trial. Check a case below.
Built from the radiology-benefit-management guidelines insurers actually use — eviCore (Cigna, Aetna) and Carelon (Anthem), both based on the ACR Appropriateness Criteria — digested into the exact criteria below, with the source cited on every result. Last verified June 2026.
Whoever reviews the request — usually a vendor like eviCore or Carelon, not the insurer directly — is checking the chart for one of two pathways:
This is the single most common imaging denial we see: a typical migraine or tension headache, with a normal neurological exam and no red flags, is not covered. The evidence is that imaging in that situation almost never changes management. Imaging is medically necessary the moment there's a red flag — a sudden "worst-ever" onset, a focal neurological finding, a new headache after 50, cancer history, or a headache that wakes the patient from sleep. The difference between a denial and an approval is often a single documented finding.
For a knee, shoulder, or hip MRI, the guidelines require current plain x-rays first — skipping them is an easy denial. After the x-ray, the MRI qualifies with either ~6 weeks of conservative care or at least two acute exam findings that fast-track it: a positive provocative test (McMurray's for the knee, impingement for the shoulder), a locked or catching joint, an effusion, or an acute injury. A locked knee with an effusion, or a positive McMurray's after a twisting injury, can move straight to MRI without the 6-week wait.
See whether a case clears the red-flag or conservative-care bar — and exactly what to document if it doesn't. About two minutes, free.
Check imaging coverageAdvanced imaging is usually reviewed by a radiology-benefit-management vendor (eviCore for Cigna and Aetna, Carelon for Anthem) against criteria based on the ACR Appropriateness Criteria. The most common reasons for denial are no documented red-flag finding and no documented conservative-care trial (about six weeks of physical therapy plus medication), or — for a joint MRI — no plain x-ray done first.
A red flag is a finding that makes advanced imaging medically necessary right away, waiving the conservative-care wait. For the spine: progressive weakness, cauda-equina signs, suspected fracture, cancer, or infection. For the head: thunderclap onset, focal neurological deficit, new headache after 50, cancer or immunosuppression. If a red flag is present, the key is to state it clearly on the request.
A typical migraine or tension headache with a normal neurological exam and no red flags generally does not qualify — this is the most common imaging denial. It qualifies when there's a red-flag feature or a focal neurological finding, or a clear change in the headache pattern.
Yes. The imaging guidelines require current plain x-rays before a joint MRI. After the x-ray, the MRI qualifies with either about six weeks of conservative care or at least two acute exam findings (a positive provocative test, locking, an effusion, or an acute injury).
Largely, yes. Most advanced-imaging PA is delegated to a few vendors — eviCore (Cigna, Aetna) and Carelon (Anthem) — and both build on the same ACR Appropriateness Criteria, so the rules converge. UnitedHealthcare uses its own ACR-aligned policy. We cite the specific guideline that applies to your insurer on every result.
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