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    v1.0.30
    OpenPayerBilling CodesOther ProceduresCPT cpt-77399-medical-radiation-physics-dosimetry-unlisted
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    CPT 77399: Medical Radiation Physics, Dosimetry, and Treatment Devices

    CPT code 77399 is an unlisted procedure code used to report medical radiation physics, dosimetry, and treatment device services that lack a specific CPT code, typically encompassing custom physics consultations, complex dosimetry calculations, and nonstandard treatment device fabrication or modification; service type: medical radiation physics and dosimetry; typical site of service: radiation oncology departments, hospital outpatient departments, and freestanding radiation therapy centers.

    For related coverage guidance, see recent payer policy updates: Radiation oncology coverage and treatment delivery guidelines, Proton Beam Therapy, Radiation and Oncologic Procedures.

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    Table of contents

    Progress1 / 7

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    Clinical & Coding Specifications

    Clinical Context

    A typical patient is an adult undergoing external beam radiotherapy for a malignant tumor (for example, head and neck, lung, or prostate cancer) who requires a non-routine medical physics, dosimetry, or treatment device service that does not have a specific CPT code. The workflow begins with the radiation oncologist identifying a unique planning or delivery need—such as custom bolus design, specialized dosimetric measurements for an irregular treatment field, patient‑specific quality assurance for an uncommon treatment technique, or fabrication/verification of a novel immobilization or shielding device. A medical physicist and dosimetrist perform measurements, calculations, device fabrication or commissioning, and documentation. The service may occur in the radiation oncology department within a hospital outpatient department, freestanding radiation therapy center, or academic medical center. Billing uses 77399 to report the one‑off or miscellaneous physics/dosimetry/treatment device service when no other specific CPT code applies. Documentation includes the clinical indication, description of the service performed, time and personnel involved, technical report of measurements/calculations, device specifications, and patient‑specific QA results.

    Related CPT Codes

    CPT CodeDescriptionRelationship to This Procedure
    77336Continuing medical physics consultation, including chart review and oversight of treatment deliveryOften billed for ongoing physics oversight; 77399 used for unusual physics tasks not covered by 77336.
    77370Special medical radiation physics consultation, including chart review, and review of treatment plans, typical for complex casesUsed for special consultations; 77399 applies when specific technical tasks or device fabrication fall outside 77370.
    77331Special dosimetry (for example, multiple calculation points, brachytherapy planning)Related dosimetry services; 77399 used when unique dosimetric measurements or devices are required that lack specific codes.
    77338Stereotactic radiosurgery physics consultation, patient-specific QA for radiosurgeryFrequently associated for high-precision treatments; 77399 may capture bespoke QA or device work not described by 77338.
    77334Special medical radiation physics consulting, dosimetry or treatment devices (provision of custom devices) — note: limited and sometimes facility-specificUsed when available; if no specific code fits the custom device or one‑time service, 77399 is reported.

    Related Modifiers

    12 rows

    ModifierDescriptionWhen to Use
    22Modifier –22 (Increased Procedural Services) is used when a reported procedure is substantially more extensive than normally required. The CPT Manual and CMS state it may be appended only when the…- When to use: Append modifier -22 to a procedural CPT code when the service performed is substantially more extensive than the usual service described by that code — i.e., the procedure required…
    23Modifier -23 (Unusual Anesthesia) is used on anesthesia service CPT codes when a procedure that normally requires no anesthesia or only local anesthesia must be performed under general anesthesia…- Use modifier -23 only on anesthesia CPT codes (00100–01999) when a procedure that normally requires no anesthesia or only local anesthesia must be performed under general anesthesia because of…
    26Modifier 26 (Professional Component) identifies and bills only the professional portion of a split service — the physician’s interpretation, report, and medical judgment — when the technical…- Use CPT Modifier -26 when you are billing only the professional component (PC) of a split‑bill eligible service—i.e., you performed the physician interpretation, medical judgment and prepared a…
    50Modifier –50 (Bilateral Procedure) is appended to a CPT code when an identical procedure is performed on paired anatomical structures during the same operative session. The AMA states to add…- Use modifier -50 when the same CPT surgical, diagnostic, or radiology procedure is performed on paired anatomical structures (both sides of the body) during the same operative/session by the same…
    52Modifier ‑52 (Reduced Services) indicates that a service or procedure was partially reduced or omitted at the provider’s discretion, allowing reporting of the basic procedure number with a qualifier…- Use modifier -52 when a physician or qualified health professional electively reduces or omits part of a procedure or service (for example, performing fewer required views or omitting a portion of…
    53Modifier 53 (Discontinued Procedure) signals that a surgical or diagnostic service was begun by the physician but terminated because of extenuating circumstances that threatened the patient’s…- Use modifier -53 when a physician/qualified healthcare professional has started a surgical or diagnostic procedure (e.g., anesthesia administered, incision or scope insertion) and then discontinues…
    59Modifier 59 indicates a distinct procedural service when two procedures that are not normally billed together are clinically and procedurally separate. The CPT definition (as reiterated by CMS)…- Use modifier -59 to report a distinct procedural service when documentation supports that the procedure reported is not normally billed together with another service on the same day because of a…
    62Modifier 62 indicates that two surgeons function as co‑surgeons, each performing distinct parts of the same primary surgical procedure. It is appended to the primary procedure code (and any…- Use modifier -62 when two surgeons act as co‑surgeons (both primary surgeons) on a single definitive primary procedure, each performing distinct parts of the same surgical procedure (append -62 to…
    76Modifier -76, Repeat Procedure or Service by Same Physician or Other Qualified Health Care Professional, is appended when the same provider performs an identical, medically necessary procedure or…- Use modifier -76 when the same physician or other qualified health care professional performs an identical procedure or service a second (or subsequent) time on the same date of service and the…
    80CPT® Modifier 80 (Assistant Surgeon) is appended to a surgical CPT code when a physician (MD or DO) provides full, continuous assistance throughout the operative procedure. It is intended only for…- Use CPT Modifier -80 when a physician (MD or DO) serves as an assistant surgeon and provides full, continuous assistance throughout the entire operative procedure; append -80 to the surgical CPT…

    Showing 1–10 of 12

    Related Provider Taxonomies

    8 rows

    Taxonomy Code
    251B00000X
    246Q00000X
    208D00000X
    174400000X
    390200000X
    287300000X
    3336H0001X
    101YP2500X

    Related ICD-10-CM Codes

    26 rows

    ICD-10-CM CodeDescription
    C15.9Malignant neoplasm of esophagus, unspecified
    C18.9Malignant neoplasm of colon, unspecified
    C20Malignant neoplasm of rectum
    C22.0Liver cell carcinoma
    C25.9Malignant neoplasm of pancreas, unspecified
    C34.90Malignant neoplasm of unspecified part of unspecified bronchus or lung
    C43.9Malignant melanoma of skin, unspecified
    C50.912Malignant neoplasm of unspecified site of left female breast
    C54.9Malignant neoplasm of corpus uteri, unspecified
    C56.9Malignant neoplasm of unspecified ovary

    Showing 1–10 of 26

    Related Payer Policy Updates

    Specialty: Radiation Oncology1 / 2

    10 rows

    PolicyPayerEffective Date
    Radiation oncology coverage and treatment delivery guidelinesevicore2026-11-05
    Proton Beam Therapyuniversityofutahhealthplans2026-10-25
    Radiation and Oncologic ProceduresUnitedHealthcare2026-09-01
    Electronic Brachytherapy for Nonmelanoma Skin CancerBluecross Idaho2026-07-30
    Surface Radiation Therapy for Treatment of Non-Melanoma Skin Cancereocco2026-07-09
    Radiofrequency Ablation of Tumors Outside the LiverProvidence Health Plan2026-07-01
    Therapeutic Radiopharmaceuticals in Oncology (Lutathera, Pluvicto, Xofigo) Coverage CriteriaBlue Cross Blue Shield - North Carolina2026-07-01
    Intensity Modulated Radiation TherapyAmbetter Georgia2026-06-01
    Irreversible Electroporation (IRE) of Tumors Other Than LiverBlue Cross Blue Shield - Rhode Island2026-06-01
    Irreversible Electroporation (IRE) — NanoKnife (Preauthorization Required)Blue Cross Blue Shield - Nebraska2026-06-01

    Frequently Asked Questions

    References

    1. 1.CPT® Codes and Descriptions. AAPC. Retrieved Aug 11, 2026.Maintains the CPT code set's official descriptions and guidelines, licensed from the American Medical Association, used as the definitional source for CPT codes on this page.
    2. 2.HCPCS Quarterly Update. Centers for Medicare & Medicaid Services (CMS). Retrieved Aug 11, 2026.CMS's quarterly release of HCPCS Level II codes and short/long descriptors, the source for HCPCS code definitions and update history.
    3. 3.ICD-10-CM Full Code List. Centers for Medicare & Medicaid Services (CMS). Retrieved Aug 11, 2026.CMS's complete ICD-10-CM diagnosis code list, used to cross-reference diagnosis codes associated with this procedure or service.
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