Medicare covers PET scans under National Coverage Determination 220.6 when a treating physician documents that the scan is medically necessary for a specific cancer, cardiac, or neurological condition on the covered list. Medicare PET scan coverage is national, so the rules apply the same way regardless of where you live or which contractor processes the claim, and you pay the standard Part B cost-sharing once the scan qualifies. What varies is the indication, the radioactive tracer, and the paperwork your provider must attach to the claim.
Cancer Indications and How Often Medicare Will Pay
Cancer is the broadest category under NCD 220.6, and coverage is split into two phases of treatment. The phase controls how many scans Medicare will pay for and which modifier your provider must use on the claim.
Initial Treatment Strategy
Medicare covers one FDG-PET scan per cancer diagnosis to help plan the first course of treatment. The tumor must be either biopsy-proven or strongly suspected based on other diagnostic testing. This applies to all solid tumors, not a shortlist of specific cancers. The claim carries the PI modifier to show the scan is informing the initial treatment plan.1Centers for Medicare & Medicaid Services. Transmittal 3162 – Medicare Claims Processing Manual
Subsequent Treatment Strategy
Once initial therapy is complete, Medicare covers FDG-PET scans to detect residual disease, evaluate suspected recurrence, or determine the extent of a known recurrence. These claims use the PS modifier. For some uses, the scan results must demonstrably influence clinical management, such as pinpointing the best location for a biopsy or surgical procedure.1Centers for Medicare & Medicaid Services. Transmittal 3162 – Medicare Claims Processing Manual
The Three-Scan Cap and the KX Modifier
Medicare pays for up to three subsequent treatment strategy PET scans per cancer diagnosis without additional documentation. Each different cancer diagnosis gets its own count: one PI scan and three PS scans. Whether or not a PI claim was filed has no effect on the PS count.1Centers for Medicare & Medicaid Services. Transmittal 3162 – Medicare Claims Processing Manual
Starting with the fourth subsequent treatment strategy scan for the same cancer diagnosis, your provider must add a KX modifier to the claim. The KX modifier is an attestation that the scan meets the medical policy requirements set by your local Medicare Administrative Contractor. A fourth or later PS scan submitted without KX will be denied as not medically necessary.1Centers for Medicare & Medicaid Services. Transmittal 3162 – Medicare Claims Processing Manual
Heart Indications
Medicare covers cardiac PET in two distinct situations, and the tracer differs depending on the question being asked.
For myocardial viability, Medicare covers FDG-PET to determine whether damaged heart muscle is still alive before a revascularization procedure such as bypass surgery or angioplasty. The scan can serve as the primary diagnostic study or as a follow-up when a prior SPECT was inconclusive. SPECT cannot be used as a follow-up to an inconclusive PET for this purpose.2Centers for Medicare & Medicaid Services. NCD – PET Scans 220.6
For cardiac perfusion, Medicare covers PET scans using Rubidium-82 or Ammonia N-13, not FDG, to evaluate blood flow to the heart in patients with known or suspected coronary artery disease. The perfusion PET must be performed in place of a SPECT or after a SPECT that was inconclusive. Inconclusive means the results were equivocal, technically unreadable, or didn’t match the patient’s other clinical findings, and that must be documented in the file.3Centers for Medicare & Medicaid Services. NCD – PET for Perfusion of the Heart 220.6.1
Neurological Indications
Neurological coverage breaks into three categories with quite different rules.
Distinguishing Frontotemporal Dementia from Alzheimer’s
Medicare covers FDG-PET to differentiate frontotemporal dementia from Alzheimer’s disease when the diagnosis remains uncertain after a thorough clinical evaluation. The patient must have documented cognitive decline lasting at least six months and a comprehensive workup including a medical history from the patient and someone who knows them well, cognitive testing, lab work, and structural imaging such as MRI or CT. A physician experienced in diagnosing dementia must have evaluated the patient, and that evaluation must not have identified a specific neurodegenerative cause.2Centers for Medicare & Medicaid Services. NCD – PET Scans 220.6
Amyloid PET for Alzheimer’s Treatment Eligibility
Effective October 13, 2023, CMS ended the coverage with evidence development requirement and removed the one-scan-per-lifetime limit for amyloid PET imaging. Medicare Administrative Contractors now make their own coverage decisions for amyloid PET, so rules can vary by region. Ask your provider to confirm current billing requirements with the MAC.
This matters because newer Alzheimer’s treatments, including monoclonal antibody therapies, require confirmation of beta-amyloid plaques to establish eligibility. Medicare covers these treatments for patients diagnosed with mild cognitive impairment or mild dementia due to Alzheimer’s disease, and the provider must confirm amyloid plaque presence as part of the eligibility criteria and collect data for a qualifying study or registry.4Medicare. Monoclonal Antibodies for the Treatment of Early Alzheimers Disease
Seizure Focus Localization
FDG-PET is covered to locate the source of seizures in patients with refractory epilepsy who are being evaluated for surgery. The scan helps identify the brain region responsible for seizure activity when medication has failed to control it.2Centers for Medicare & Medicaid Services. NCD – PET Scans 220.6
What Medicare Will Not Cover
NCD 220.6 works on a whitelist principle: if a use is not specifically listed, it is not covered. A few exclusions surprise people.
- Screening. PET scans are not covered for patients without specific signs or symptoms of disease. There is no general cancer-check PET.
- Infection and inflammation. FDG-PET is specifically not covered for chronic osteomyelitis, infection of hip replacement hardware, or fever of unknown origin. CMS concluded the evidence was insufficient to show improved health outcomes.5Centers for Medicare & Medicaid Services. NCD – FDG PET for Infection and Inflammation 220.6.16
- Non-FDG tracers for unlisted conditions. Newer tracers such as Gallium-68 DOTATATE, used for neuroendocrine tumors, are not addressed in NCD 220.6. Coverage falls to your regional MAC through a local coverage determination.
When an indication isn’t covered nationally and no local determination applies, Medicare will deny the claim. If your provider expects a denial, they are required to give you an Advance Beneficiary Notice of Non-coverage before performing the scan. The ABN explains that Medicare likely won’t pay and lets you decide whether to proceed and accept financial responsibility.6Centers for Medicare & Medicaid Services. FFS ABN
Baseline Conditions Every PET Scan Must Meet
Even a covered indication won’t get paid unless the basics are in place. Your treating physician must order the scan and document why it’s medically necessary in your medical record. The scan can’t simply duplicate information already available from other covered diagnostic tests. The radioactive tracer and any related drugs must be FDA-approved.2Centers for Medicare & Medicaid Services. NCD – PET Scans 220.6
Outpatient imaging suppliers that perform PET scans must also be accredited by a CMS-designated organization. This requirement does not apply to hospitals or critical access hospitals.7Centers for Medicare & Medicaid Services. Accreditation of Advanced Diagnostic Imaging Suppliers
What You Will Pay
PET scans fall under Medicare Part B. In 2026, the Part B annual deductible is $283.8Centers for Medicare & Medicaid Services. 2026 Medicare Parts A and B Premiums and Deductibles Once the deductible is met, you pay 20% of the Medicare-approved amount and Medicare pays the remaining 80%.9Medicare. Medicare and You Handbook 2026
A Medigap supplemental policy may cover part or all of that 20% coinsurance. Medicare Advantage plans must cover everything Original Medicare covers, but they can impose prior authorization requirements and may use different cost-sharing structures. If you’re enrolled in Medicare Advantage, check with your plan before scheduling.
If the Claim Is Denied
Denials happen. The common causes are a missing modifier, insufficient documentation of medical necessity, or an indication outside NCD 220.6. Medicare has a five-level appeals process for Part B claim denials, and most disputes resolve at the first or second level.10Centers for Medicare & Medicaid Services. Medicare Parts A and B Appeals Process
The first step is a redetermination request to your Medicare Administrative Contractor. You have 120 calendar days from the date you receive the denial notice to file, and receipt is presumed to be five days after the notice date unless you can show otherwise.11eCFR. 42 CFR 405.942 – Time Frame for Filing a Request for a Redetermination The key to winning a redetermination is documentation: your physician’s notes should clearly explain why the scan was medically necessary for your specific condition and how it meets the criteria in NCD 220.6.
If the denial was caused by a missing PI, PS, or KX modifier, your provider can often correct and resubmit the claim without a formal appeal. Ask before you file. A billing fix is faster than a redetermination.