A family physician orders a lumbar MRI for a 48-year-old with eight weeks of low back pain radiating down the left leg. The referral coordinator submits the prior authorization to the patient's Blue plan, waits four days, and gets a denial. The plan did not decide it. A radiology benefit manager did, in about ninety seconds, because the request did not say how long the pain had lasted or what conservative treatment had been tried. The physician's note had both. Nobody typed them into the portal.
Prior authorization for imaging is the most automated corner of utilization management. For advanced imaging, which means MRI, CT, PET and nuclear cardiology, most commercial plans and many Medicare Advantage and Medicaid managed care plans hand the decision to a radiology benefit manager (RBM): a vendor that applies evidence-based criteria through a scripted set of questions and either approves in real time or routes to a nurse and then a physician reviewer. Once you know the questions, the same-day approval rate goes up sharply.
This piece names the four RBMs you will meet, explains what they check, walks through a lumbar MRI request, and covers what changed on January 1, 2026 under the CMS interoperability and prior authorization rule.
Key takeaways
- Four vendors decide most imaging prior authorizations in the United States: EviCore, Carelon Medical Benefits Management, Evolent and HealthHelp. Which one you face depends on the plan, not the patient.
- RBM criteria are built on the ACR Appropriateness Criteria and ask the same things: duration of symptoms, conservative treatment tried, red flags, prior imaging and the specific question the study will answer.
- Requests submitted through the RBM portal with the clinical questions answered from the note usually approve in minutes; requests that say "MRI lumbar, back pain" go to review and often deny.
- Since January 1, 2026, Medicare Advantage and Medicaid managed care plans must decide standard requests within 7 calendar days and urgent requests within 72 hours, and must give a specific denial reason.
Who the radiology benefit managers are
The names change through mergers, which is part of why staff find them confusing. EviCore is owned by Evernorth, Cigna's services arm, and reviews imaging for Cigna as well as for other plans that contract with it, including some Aetna commercial products and many regional plans. Carelon Medical Benefits Management is the Elevance Health (Anthem) subsidiary that was called AIM Specialty Health until 2023; it reviews for Anthem plans and several other Blue plans. Evolent absorbed National Imaging Associates, long known as NIA or Magellan Healthcare, and runs the RadMD portal used by many Blue plans and Medicaid managed care organizations. HealthHelp is the fourth, used by a number of regional and Medicaid plans.
The practical consequence is that "which payer" is the wrong question at the front desk. The right question is "which RBM does this plan use for imaging," and the answer is usually on the back of the card or in the plan's provider manual. We keep a grid by plan with the RBM name, portal address, phone number and hours, and whether the plan requires authorization for office ultrasound and plain films (most do not) as well as advanced imaging (most do).
Original Medicare is the exception. Fee-for-service Medicare does not require prior authorization for office or outpatient advanced imaging, and the Appropriate Use Criteria program that would have required ordering physicians to consult a clinical decision support tool was paused and its regulations rescinded in the CY 2024 Physician Fee Schedule final rule, effective January 1, 2024. For a Medicare fee-for-service MRI there is nothing to do beyond documenting medical necessity.
What the RBM actually checks
Each RBM publishes its clinical guidelines, and they are more alike than different because they descend from the same source: the American College of Radiology Appropriateness Criteria, supplemented by specialty society guidance. For any study the reviewer, human or algorithm, is looking for five things.
- The clinical question. What the imaging is meant to decide. "Rule out disc herniation as the cause of L5 radiculopathy before surgical referral" is a question. "Back pain" is a symptom.
- Duration and course. How long, and whether it is worsening. Many guidelines require six weeks of symptoms for a non-emergent spine MRI unless a red flag is present.
- Conservative treatment. What was tried, for how long, and the result: physical therapy, NSAIDs, activity modification, a home exercise program, with dates.
- Red flags or exam findings that bypass the waiting period. Progressive neurologic deficit, bowel or bladder symptoms, history of cancer, fever with back pain, trauma, anticoagulation. These are the criteria that turn a routine request into an approval on the spot.
- Prior imaging. Whether a plain film or an earlier study exists and what it showed. Ordering a knee MRI with no radiograph on file is one of the most common reasons for a pend.
The table shows how this plays out for the studies independent practices order most.
| Study | CPT | What the RBM usually wants to see |
|---|---|---|
| MRI lumbar spine without contrast | 72148 | 6 weeks of symptoms with conservative care documented, or a red flag; neuro exam findings; plain films optional |
| MRI knee without contrast | 73721 | Recent radiograph; mechanical symptoms (locking, giving way) or suspected ligament or meniscal tear; failed conservative care |
| MRI brain with and without contrast | 70553 | Specific indication (new focal deficit, headache with red flags, seizure); why contrast is needed |
| CT abdomen and pelvis with contrast | 74177 | Acute indication or specific finding to characterize; labs when relevant; whether ultrasound was done first for right upper quadrant or pelvic pain |
| CT chest without contrast | 71250 | Abnormal chest radiograph, nodule follow-up interval per guideline, or lung cancer screening criteria (age and pack-year history) for 71271 |
One check is less clinical: for many plans the RBM steers site of care, so a request for hospital outpatient imaging may be approved only at a freestanding center unless a clinical reason for the hospital is given.
A lumbar MRI, done twice
Here is our opening case, submitted the way it was and the way it should have been. The first submission, typed into the Carelon portal by a coordinator working from the order alone: "72148, lumbar MRI, diagnosis M54.50 low back pain." The algorithm found no duration, no conservative treatment, no neurologic findings and a nonspecific diagnosis. It pended to nurse review, the nurse requested records, records arrived on day three, and the physician reviewer denied on day four because the faxed note was 14 pages and the relevant sentence was on page 9.
The second submission, built from the note: diagnosis M54.16, radiculopathy, lumbar region; onset eight weeks ago; six weeks of physical therapy completed on a stated date with a copy of the PT discharge summary; positive straight-leg raise on the left with diminished ankle reflex documented at the visit; NSAIDs and a home exercise program for eight weeks; clinical question is surgical referral for suspected L5-S1 herniation. Every one of those items maps to a portal question. The approval came back in the same session with an authorization number and a 45-day validity window.
The clinical answers existed; the workflow did not carry them from the note to the portal. We fix this with a one-page imaging order checklist the physician completes at the time of the order, with the five items above as fields, so the coordinator is transcribing rather than hunting.
Getting a same-day answer
Use the RBM's portal, not the plan's fax line. Portal requests are scored in real time; faxes wait for a human. Enter the exact CPT code including the contrast decision (72148 without, 72158 with and without) and a diagnosis code as specific as the documentation supports; an unspecified pain code is a soft signal for review. Attach the relevant pages of the note, not the whole chart.
If the request pends, ask for the peer-to-peer review right away. Most RBMs allow the ordering physician to speak with a reviewing physician within a short window, often before the formal denial is issued, and a two-minute conversation that states the red flag or the failed conservative care resolves most pends. Put the peer-to-peer phone number for each RBM on the grid.
Know the retroactive rules before the patient is scanned. Some plans allow a retro request within two business days of the study for urgent cases; others allow none. A scan performed without authorization comes back CO-197 (precertification, authorization or notification absent) or CO-15 (authorization number missing or invalid), and the patient cannot be billed for the plan's share under most contracts. Those denials are almost never overturned on appeal unless the situation was a true emergency, which is why the imaging center usually refuses to scan without a number. Track them in your denial management reporting as a front-end failure, not a payer failure.
What changed in 2026
The CMS Interoperability and Prior Authorization final rule (CMS-0057-F), published January 17, 2024, has its first operational provisions in force as of January 1, 2026. Medicare Advantage plans, Medicaid and CHIP managed care plans and fee-for-service Medicaid must now issue standard prior authorization decisions within 7 calendar days of a complete request and expedited decisions within 72 hours, and every denial must state a specific reason. Qualified health plans on the federal exchanges are covered by the rule but were excluded from the decision timeframes, and the rule does not apply to drugs. Because RBMs decide on behalf of these plans, the clocks apply to them too.
State law is moving as well. Texas passed the first gold card law in 2021, exempting physicians with high approval rates from prior authorization for the services concerned, and several states have followed. Some RBMs are trimming their lists on their own; Evolent, for example, removed prior authorization for a set of radiology and diagnostic cardiology codes for Health Net members effective May 1, 2026. Check each RBM's code list at least twice a year; requesting authorization for a study that no longer needs one wastes an hour just as surely as forgetting one.
Questions we hear
The imaging center says it will get the authorization. Can we let them?
They can start the request, but the RBM still needs the ordering physician's clinical answers, and if the center submits "back pain" you own the denial and the delayed patient. The fastest path in our experience is for the ordering office to submit with the note attached and give the center the authorization number.
How long is an imaging authorization good for?
It depends on the RBM and the plan: 30, 45, 60 and 90 days are all common, and the window is printed on the approval. If the patient cannot be scheduled inside it, call before it expires; most RBMs will extend once. A scan one day after expiry denies as if there were no authorization at all.
Does a Medicare Advantage plan have to follow Medicare's no-authorization rule for imaging?
No. Medicare Advantage plans may require prior authorization for services that Original Medicare does not, and most do for advanced imaging, usually through one of the RBMs above. What they cannot do, since January 1, 2026, is take longer than 7 calendar days for a standard decision or deny without a specific reason. Since 2024 they also must follow Original Medicare coverage criteria when making medical necessity decisions, which is worth citing in an appeal when a plan denies a study Medicare would cover.
What to do this week
- Build the RBM grid: for each of your top ten plans, the vendor, portal, phone, peer-to-peer line, retro-authorization window and which imaging codes require authorization.
- Create a one-page imaging order checklist with the five clinical items and have physicians complete it at the time of the order for one week.
- Pull last quarter's CO-197 and CO-15 denials on imaging and sort them by cause: never requested, requested late, expired, or wrong code. Each cause has a different fix.
- Check the current code lists for your RBMs and remove any study that no longer requires authorization from the coordinator's workflow.
- Log the submission and decision dates on Medicare Advantage and Medicaid managed care requests to hold plans to the 7-day and 72-hour limits.
