CPT Code 78815: PET/CT Billing, Modifiers & Reimbursement

Key Takeaways

CPT Code 78815 describes a PET scan with concurrent CT for attenuation correction, covering skull base to mid-thigh – not whole body

HCPCS A9552 (FDG) is billed separately from 78815; the procedure code does not include radiopharmaceutical drug administration

Medicare coverage requires a confirmed or suspected oncologic indication; the PI modifier is used for non-covered indications to prevent automatic denial

Pabau’s claims management software helps radiology and nuclear medicine practices reduce 78815 claim denials through structured documentation workflows

PET/CT denials are among the costliest in nuclear medicine billing. CPT Code 78815 is one of the most frequently submitted codes for oncologic imaging, yet practices routinely lose reimbursement due to missing documentation, incorrect modifier usage, or misidentified anatomic coverage. Understanding exactly how to bill CPT Code 78815 – from radiopharmaceutical pairing to payer-specific prior authorization – is where accurate reimbursement either holds or collapses.

This reference covers the full descriptor, covered diagnoses, Medicare criteria, modifier requirements, HCPCS radiopharmaceutical pairing, code comparisons within the 78811-78816 series, and the denial patterns coders need to anticipate before submission.

CPT Code 78815: Full Descriptor and Clinical Definition

CPT Code 78815 is defined by the American Medical Association (AMA) as: Positron emission tomography (PET) with concurrently acquired computed tomography (CT) for attenuation correction and anatomical localization imaging; skull base to mid-thigh. The key clinical distinction is the anatomical scan range. Where whole-body codes (78813, 78816) require imaging beyond mid-thigh, this code specifically applies when the scan field terminates at approximately the mid-femur level.

The concurrent CT component in this code serves two purposes: attenuation correction of the PET signal and anatomical localization of tracer uptake. It is not a diagnostic CT. Billing the CT as a separate diagnostic study alongside 78815 is a common bundling error that triggers edits. A diagnostic CT requires separate clinical indication, separate interpretation, and specific documentation to justify unbundling.

The 78811-78816 PET/CT Code Series

Selecting the correct code from the PET/CT series is the first billing decision. The wrong choice here generates downcoding or denial before documentation is even reviewed.

According to Radiology Today coding guidance, when a scan does not cover the full body (including extremities below mid-thigh), the provider should report it as a skull base to mid-thigh study using 78812 or 78815. For melanoma staging or other presentations requiring complete lower extremity imaging, 78816 is appropriate. Applying Pabau’s claims management software to track scan type against submitted codes helps radiology billing teams catch mismatches before claims go out the door.

Medicare Coverage and Medical Necessity for CPT Code 78815

Medicare coverage for CPT Code 78815 is governed by National Coverage Determination (NCD) 220.6. Coverage is indication-specific: not every PET scan ordered for a cancer patient automatically qualifies. The CMS Medicare Coverage Database outlines which oncologic indications are covered, which require evidence development (registry participation), and which remain non-covered.

Medicare Part B covers FDG PET scans for staging, re-staging, and monitoring of treatment response across a defined list of cancers. Common covered oncologic indications include colorectal cancer, esophageal cancer, head and neck cancers (non-thyroid), lymphoma, melanoma, non-small cell lung cancer, cervical cancer, and thyroid cancer. Breast cancer coverage under Medicare is limited to specific clinical scenarios.

NaF Bone PET and Registry Requirements

Sodium fluoride (NaF) bone PET represents one of the most common denial triggers for 78815 claims. Medicare currently deems NaF bone PET imaging to be covered only through Coverage with Evidence Development (CED), which means patients must be enrolled in an approved registry before the study qualifies for reimbursement. Practices submitting 78815 for NaF bone PET without registry enrollment documentation should expect denial. Per AAPC forum discussions referencing CMS coverage policy, this requirement remains a consistent compliance gap for practices transitioning from conventional bone scans to PET-based bone imaging.

Commercial Payer Policies

Aetna’s Clinical Policy Bulletin 0071 and Cigna’s Knowledge Center both maintain medical policies governing PET scan coverage that may differ from Medicare NCD 220.6 criteria. Commercial payers often apply their own covered indication lists and may require precertification for CPT Code 78815 regardless of Medicare coverage status. TRICARE covers PET scans for covered services as documented in its covered services guidance. Always verify payer-specific policy before scheduling the study when prior authorization may be required.

Modifiers for CPT Code 78815

Modifier selection for CPT Code 78815 directly affects whether a claim is paid, pending, or denied. Two modifier categories matter most in practice.

• PI modifier (Positron Emission Tomography [PET] or PET/CT to inform initial treatment strategy of tumors/masses when the beneficiary’s treating physician determines that the PET study is needed): Used for non-covered indications to signal that the service was furnished for a reason not covered by Medicare. This modifier is critical for compliance. Without it, submitting a non-covered indication risks a straight denial with no appeal pathway based on beneficiary notification. Per the WPS GHA FDG PET Imaging Modifier Fact Sheet, the PI modifier flags the claim appropriately and enables patient billing when a valid Advance Beneficiary Notice (ABN) is on file.
• TC and 26 modifiers: When the technical component (scanner, technologist) and professional component (physician interpretation) are billed separately, modifier TC applies to the facility or imaging center billing the equipment and technologist cost, while modifier 26 applies to the interpreting radiologist or nuclear medicine physician billing the professional read. Global billing (no modifier) applies when a single provider owns both components.
• Modifier 59: Use when 78815 is billed with another procedure on the same date and bundling edits are triggered, where a separate and distinct service can be documented.

Maintaining thorough HIPAA-compliant documentation in your billing records ensures that modifier justifications are defensible on audit. Every modifier applied to 78815 should correspond to a documented clinical rationale in the patient record.

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Radiopharmaceutical Billing: HCPCS A9552 and Non-FDG Agents

CPT Code 78815 does not include the cost of the radiopharmaceutical. The tracer must be billed separately using the appropriate HCPCS Level II code. Failure to bill the radiopharmaceutical, or billing the wrong HCPCS code for the agent used, represents a direct revenue loss on every claim.

FDG and Common Non-FDG HCPCS Codes

PYLARIFY (piflufolastat F 18) is a PSMA-targeted PET imaging agent used for prostate cancer. Per the Lantheus PYLARIFY Coding and Billing Guide, it is billed under its specific HCPCS code alongside CPT 78815 when used for prostate cancer staging or recurrence evaluation. Prostate cancer PET/CT at centers like the Mallinckrodt Institute of Radiology (WashU Medicine) pairs CPT 78815 with either A9588 (FACBC) or A9515 (Choline), each with distinct preparation requirements: a minimum 4-hour fast for FACBC and 6-hour fast for Choline.

Reimbursement Rates and the Medicare Physician Fee Schedule

Medicare reimbursement for CPT Code 78815 varies by site of service, geographic location, and payment year. The CMS Physician Fee Schedule lookup tool provides current reimbursement data searchable by CPT code, year, and locality. Published procedure price data is also available directly at Medicare’s Procedure Price Lookup for code 78815.

Hospital outpatient departments and ambulatory surgical centers (ASCs) receive facility payments under the Hospital Outpatient Prospective Payment System (OPPS), which differs from the Physician Fee Schedule rate applied to non-facility settings. Nuclear medicine physicians billing the professional component (modifier 26) receive the non-facility professional rate. For current RVU values and precise geographic payment calculations, the FastRVU 2026 RVU lookup tool offers a practical reference for Work, Practice Expense, and Malpractice RVU components. Rates change annually with CMS updates, so prior-year figures should never be used for current billing estimates.

Tracking reimbursement trends across payers is easier when practice billing data is organized in a centralized system. Practices using structured patient record documentation can correlate scan indications with claim outcomes, making it faster to identify which payer combinations or indication categories generate the highest denial rates for 78815.

Documentation Requirements and Common Denial Avoidance

Most 78815 denials trace back to documentation gaps rather than coding errors. The physician order and the nuclear medicine report must each support the claim independently. A claim that codes correctly but lacks supporting clinical documentation is still a denial waiting to happen.

Documentation Checklist for 78815 Claims

• Covered oncologic indication clearly stated in the order and clinical notes, matching the ICD-10-CM diagnosis code submitted
• Prior therapy history documented when billing for re-staging or treatment response monitoring
• Specific scan range documented to confirm skull base to mid-thigh rather than whole body (distinguishing 78815 from 78816)
• Radiopharmaceutical agent and dose documented in the procedure note to support the separately billed HCPCS code
• ABN on file when the PI modifier is applied, evidencing that the patient was notified of likely non-coverage before the study
• Registry enrollment documentation for NaF bone PET studies billed under Coverage with Evidence Development (CED)
• Prior authorization number recorded in the claim when required by the payer – missing PA numbers are a top administrative denial cause

Maintaining this documentation within a structured clinical forms workflow reduces the time spent reconstructing records during pre-payment review or post-payment audit. Digital clinical documentation captures these elements at the point of care rather than retroactively.

Prior Authorization Requirements by Payer

Prior authorization requirements for CPT Code 78815 vary significantly across payers and cannot be generalized. Medicare fee-for-service generally does not require prior authorization for covered PET indications under NCD 220.6, though Medicare Advantage plans frequently impose their own PA requirements. Commercial payers including Aetna and Cigna may require precertification for PET/CT studies regardless of the clinical indication.

TRICARE covers PET scans for covered services; refer to the TRICARE covered services documentation for current authorization criteria. For practices managing high volumes of PET referrals, building payer-specific PA requirements into the pre-service intake and authorization workflow reduces the rate of studies performed without authorization. A claim submitted without a required PA number is an administrative denial, recoverable only if authorization can be obtained retroactively – a process most payers restrict significantly.

Expert Picks

Need a broader reference for nuclear medicine billing workflows? Pabau Claims Management Software outlines how practices can reduce claim errors and track prior authorization requirements across payer types.

Looking for a comprehensive CPT coding reference? AAPC Codify CPT lookup provides code descriptors, guidelines, and crosswalk data for the full 78811-78816 PET/CT series.

Want to optimize your practice’s billing documentation systems? Best Medical Practice Management Software reviews platforms that support clinical documentation and claims workflows for specialty practices.

Conclusion

CPT Code 78815 billing hinges on three things: correct anatomical code selection within the 78811-78816 series, proper radiopharmaceutical HCPCS pairing billed as a separate line item, and airtight documentation supporting the specific covered indication. Modifier errors and missing prior authorization are the most recoverable denial types – but only when practices have systems in place to catch them before submission.

Pabau’s claims management tools help nuclear medicine and radiology practices structure documentation, track authorization status, and reduce the administrative errors that drive 78815 denials. To see how Pabau can support your billing workflow, book a demo with the team.

Frequently Asked Questions