Magnetic Resonance Imaging — NCD 177 | CMS Coverage Update

TL;DR: The Centers for Medicare & Medicaid Services (CMS) modified NCD 177, the National Coverage Determination governing Medicare coverage of Magnetic Resonance Imaging, effective March 7, 2026. Here's what changes for billing teams.

CMS updated NCD 177 to reflect the current clinical and technical scope of MRI coverage under Medicare, including Magnetic Resonance Angiography (MRA) and contrast-enhanced MRA (CE-MRA). This policy governs reimbursement for MRI services billed to Medicare across a wide range of specialties — radiology, neurology, orthopedics, cardiology, and oncology among them. The policy does not list specific CPT or HCPCS codes in this version, which means your billing team needs to cross-reference your internal charge capture against the coverage criteria directly.

Quick-Reference Table

CMS MRI Coverage Criteria and Medical Necessity Requirements 2026

NCD 177 is the foundational Medicare coverage policy for Magnetic Resonance Imaging. The March 7, 2026 modification updates the framework under which CMS determines whether an MRI or MRA service meets medical necessity — and that distinction is where your claims either get paid or denied.

The coverage policy recognizes MRI as a non-invasive diagnostic imaging modality that produces images by analyzing the density, motion, and relaxation times of hydrogen nuclei in tissue. The clinical utility is well-established: MRI offers contrast resolution equal to or superior to CT in soft tissue evaluation, without ionizing radiation and without the need for iodinated contrast agents. That's not just a clinical note — it's the basis for why CMS covers MRI across such a broad set of indications.

MRA (Magnetic Resonance Angiography) is explicitly recognized as an application of MRI under this NCD. CMS covers MRA as a non-invasive diagnostic tool for imaging normal and diseased blood vessels, including visualization and quantification of blood flow. Two main MRA techniques are recognized: phase contrast (PC), which measures proton spin phase differences across the cardiac cycle, and time-of-flight (TOF), which measures magnetization differences between tissue and blood to evaluate vascular structure.

Contrast-enhanced MRA (CE-MRA) is also addressed. CE-MRA involves intravenous gadolinium — a non-ionic contrast agent — administered before imaging to improve visualization of structures. CMS distinguishes CE-MRA from unenhanced MRI and MRA studies, which matters for prior authorization and documentation purposes at many Medicare Advantage plans operating under this NCD framework.

The medical necessity standard under NCD 177 hinges on whether MRI is the appropriate modality for the clinical question being answered. CMS recognizes MRI for the detection of disruptive, neoplastic, degenerative, or inflammatory lesions in soft tissue structures — and states that this use is "established in medical practice." That phrase carries weight. Established indications under an NCD are covered without the additional scrutiny that experimental or investigational designations trigger.

Where prior authorization requirements enter the picture depends on your payer mix. Traditional Medicare follows NCD 177 directly, but Medicare Advantage plans may layer additional prior auth requirements on top of NCD criteria. If your practice has significant Medicare Advantage volume, check each plan's MRI prior authorization policy separately — NCD 177 sets the floor, not the ceiling.

CMS MRI and MRA Exclusions and Non-Covered Indications

The modified NCD 177 does not enumerate a formal exclusions list in the portion of the policy summary available. That said, MRI coverage under Medicare is not unconditional.

The real issue here is medical necessity documentation. CMS coverage policy requires that the indication for MRI be clinically justified — that the imaging is ordered to answer a specific diagnostic question that MRI is suited to address. Claims denied for lack of medical necessity on MRI are common, and most of them fail at the documentation level, not the clinical level. The physician's order and the clinical note need to connect clearly to the covered indication.

For CE-MRA specifically, the use of gadolinium-based contrast must be documented as clinically indicated. A blanket order for "MRI with contrast" without documented rationale is the kind of thing that attracts post-payment review. Make sure your ordering providers know that.

Coverage Indications at a Glance

CMS MRI Billing Guidelines and Action Items 2026

The absence of specific CPT and HCPCS codes in NCD 177-v6 is not a pass — it's a signal that this NCD operates as a coverage framework rather than a code-specific policy. Your billing team still needs to act.

CPT, HCPCS, and ICD-10 Codes for MRI Under NCD 177

NCD 177-v6 does not list specific CPT, HCPCS, or ICD-10 codes. This is not unusual for a broad NCD covering an imaging modality — CMS typically addresses MRI at the modality level here and leaves code-specific coverage guidance to Local Coverage Determinations (LCDs) and related billing articles.

What This Means for Your Code Mapping

Your MRI billing relies on CPT codes assigned at the claim level — codes like those in the 70xxx and 71xxx series for body part-specific MRI and MRA — but those codes are governed by LCD-level policies and CMS billing contractor guidance, not NCD 177 directly.

Do not fabricate code mappings from this NCD. Cross-reference your specific MRI and MRA CPT codes against the relevant LCD from your Medicare Administrative Contractor (MAC). NCD 177 sets coverage intent; your MAC's LCD sets the code-level rules.

If your billing team isn't sure which MAC LCD applies to your MRI billing, contact your MAC directly or review their published LCDs through the CMS Coverage Database. The NCD 177-v6 effective date of March 7, 2026 is the controlling date for the coverage framework — any LCD updates should align with it.