Prior authorization for MRI, CT, PET, and nuclear, automated across every RBM

Imaging PA is the most delegated category in commercial insurance. Four radiology benefit managers (RBMs) handle the majority of high-tech imaging PA: eviCore, NIA/Evolent, Carelon (formerly AIM), and a still-active AIM channel. Each RBM has its own portal, criteria set, and AUC scoring. This page walks the imaging-type breakdown, the RBM map, and the payer-to-RBM delegation that drives where each PA actually goes.

MRI prior authorization

MRI is the highest-volume high-tech PA category. Most commercial and MA plans require PA for all MRI except emergency-setting scans. Common CPT codes: 73221-73223 MRI shoulder, 72141 MRI cervical spine, 72148 MRI lumbar spine, 70553 MRI brain, 74181 MRI abdomen, 70544-70546 MRA. Each sub-anatomy has its own criteria set with the RBMs. MRI lumbar spine without contrast (72148) is the single most-requested imaging PA in US healthcare.

Criteria for MRI lumbar spine typically require documented symptom duration (often 6 weeks with failed conservative therapy), neurologic findings, or red flags (cauda equina signs, progressive neurologic deficit, malignancy history). eviCore and NIA both publish the ACR Appropriateness Criteria mapping. Approval rates on complete packets are high (80-90 percent); denials usually trace to missing conservative therapy or non-specific symptom documentation.

CT scan prior authorization

CT PA is similar to MRI but lower intensity on criteria for many anatomy categories. Common codes: 74176-74178 CT abdomen and pelvis, 71250-71270 CT chest, 70450 CT head, 72125-72133 CT spine, 74261-74263 CT colonography. Coronary CTA (75574) has become a preferred non-invasive workup before cardiac catheterization and has its own PA criteria under the ACC/AHA guidelines. Low-dose lung-cancer screening CT (71271) is covered as preventive for eligible patients and often bypasses PA, though documentation of eligibility (age, pack-year history) is still required.

PET and nuclear medicine

PET scans (78811-78815 F-18 FDG PET, 78608 brain PET, 78429 cardiac PET, 78608 rubidium) are PA-heavy. Oncology PET typically requires biopsy-confirmed diagnosis, staging or restaging indication, and appropriate use for the specific cancer type. Cardiac PET requires stress test or prior echo documentation. Neurology PET (dementia workup, amyloid PET with florbetapir) has tight PA criteria with AUC scoring.

Nuclear stress tests (78451, 78452 SPECT MPI, 78472-78478 RVG) require symptom documentation, risk stratification (TIMI, HEART score), and often a step through stress echo first. Bone scan (78306), HIDA (78226), thyroid scan (78070), and parathyroid (78070-78072) have lower PA intensity. Y-90 radioembolization (37242 + radiopharmaceutical) is an oncology-adjacent PA covered at infusion and oncology PA.

Interventional imaging and image-guided procedures

Fluoroscopy-guided injections (ESI, facet, SI joint), biopsies (CT-guided lung biopsy 32405, MR-guided breast biopsy 19085), and drainage procedures (percutaneous drainage 49405) share PA DNA with both the specialty (ortho, pain, oncology) and the RBM (eviCore or Carelon often). CT-guided radiofrequency ablation and microwave ablation for oncology has its own PA track.

Radiology benefit managers: eviCore, NIA/Evolent, Carelon, AIM

eviCore is owned by Cigna and operates radiology PA for Cigna commercial, much of Aetna, Humana MA, and several regional BCBS plans. eviCore portal at evicore.com with XML/API submission available for high-volume providers. Criteria published and updated quarterly; tech-assessment packets required for high-tech.

NIA (now part of Evolent) handles radiology PA for portions of UnitedHealthcare (select plans), several BCBS states, and Managed Medicaid plans. Portal is RadMD.com. AUC scoring required on many submissions.

Carelon (Anthem-owned, formerly AIM Specialty Health) handles radiology PA for Anthem BCBS plans, Highmark, and several Elevance subsidiaries. Portal at providerportal.com. AIM branding is still visible in some payer materials; Carelon is the current entity.

AIM Specialty Health remains an active brand under Carelon for legacy contracts. Same back-end, portal may show either name.

HealthHelp handles radiology PA for select Humana and Medicare Advantage lines.

MedSolutions and RadSite exist in narrower markets.

Payer-to-RBM delegation map (2026)

For the full payer detail see commercial payers, BCBS plans, and Medicare, Medicaid, and government payers. The RBMs themselves are covered on the PA portals and UM vendors page.

RIS, PACS, and referring-provider EHRs

• RIS (radiology information systems): Epic Radiant, Sectra, Merge, Intelerad, Change Healthcare Radiology, GE Centricity RIS-IC.
• PACS: Merge, Synapse, Sectra, Intelerad. Flexbone reads reports, not pixel data.
• Referring-provider EHRs: athenahealth, NextGen, eClinicalWorks, Allscripts/Veradigm, and specialty EHRs. See outpatient EHR PA.
• Imaging centers: standalone RIS integrations plus referral feeds from referring-provider EHRs.

How Flexbone handles imaging PA

Imaging PA has a specific rhythm: scan date is fixed, PA has to clear before the patient arrives, and criteria are mostly documentation-based. Flexbone pulls the referring-provider note and any conservative therapy history, matches to the relevant RBM criteria (eviCore, NIA, Carelon, or AIM), submits via portal or XML/API where available, and handles scan-date-coupled escalation when a PA is stuck close to the scan window. See PA workflow and the platform.