CPT 77331: Special Dosimetry and Radiation Monitoring

Medicare pays $45 and commercial payers pay $173 on average nationally for this procedure.

CPT code 77331 describes physician-ordered special dosimetry services in which the provider uses radiation monitoring and measuring devices to calculate the amount of radiation delivered to the human body; this is a dosimetry and radiation monitoring service performed as part of radiation treatment planning and delivery, typically provided in an outpatient radiation oncology or hospital radiation therapy setting using in-vivo or phantom-based measurement techniques.

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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National Reimbursement Benchmarks

Commercial averages sit well above Medicare for CPT 77331: Blue Cross Blue Shield and BUCA show notably higher means versus Medicare’s mean of $44.9. BUCA’s average commercial rate is $173.4, roughly four times Medicare, while Blue Cross Blue Shield’s mean is $259.3, nearly six times Medicare, indicating substantial commercial premiuming for this code.

Dispersion (P75–P25) highlights contrast across payers. Blue Cross Blue Shield has one of the widest interquartile spreads at $71.6 ($283.7–$212.1), followed by UnitedHealth Group at $45.7 ($82.8–$36.1) and Cigna at $49.4 ($88.5–$35.6). Aetna’s spread is $33.0 ($61.0–$27.0), while BUCA’s spread is $60.0 ($195.3–$135.3). Medicare’s spread is $42.0 ($63–$21). Blue Cross Blue Shield is the most dispersed and Aetna the tightest among the listed payers.

National Payer Mean Reimbursement Rates

State Reimbursement Rates

State: Alaska1 / 51

Clinical & Coding Specifications

Clinical Context

A 68-year-old male with newly diagnosed prostate cancer (C61) is scheduled to receive external beam radiation therapy. The radiation oncology physician orders special dosimetry to measure and document the actual radiation dose delivered to sensitive organs and to verify patient-specific dose distributions prior to and during treatment. A medical physicist or qualified radiation dosimetrist places and reads thermoluminescent dosimeters or uses in vivo electronic dosimeters at the skin surface and within bolus material as directed by the physician. The workflow includes physician order for special dosimetry, setup of dosimeters during simulation or the first treatment fraction, measurement and analysis by the physics team, and documented reporting of measured dose compared to planned dose. Results are used for treatment verification, quality assurance, and to address any deviations that might require physician review. Typical sites of service are outpatient radiation oncology departments, hospital radiation therapy centers, or ambulatory surgery centers where radiation therapy is delivered.

Related CPT Codes

CPT Code	Description	Relationship to This Procedure
`77301`	IMRT treatment planning (development of an IMRT plan)	`77331` is bundled into payment for `77301` when dosimetry is provided as part of IMRT planning and should not be reported separately in that context.

Related Modifiers

9 rows

Modifier	Description	When to Use
26	Modifier 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…
77	Modifier 77 indicates that a previously performed procedure or service was legitimately repeated by a different physician or other qualified health care professional. The AMA’s CPT definition…	- Use modifier 77 when a basic procedure or service already performed is repeated by a different physician or other qualified health care professional (for example, a second provider independently…
59	Modifier 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…
52	Modifier ‑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…
53	Modifier 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…
76	Modifier -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…
78	CPT modifier -78 indicates an unplanned, related return to the operating or procedure room by the same provider during the global postoperative period. It is appended when treatment for a…	- Use modifier -78 when an unplanned, related complication during the original procedure’s global postoperative period requires the patient to return to a formal operating or procedure room and the…
22	Modifier –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…
62	Modifier 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…

Related Provider Taxonomies

8 rows

Taxonomy Code
2085R0001X
2085N0904X
2085B0100X
261QS0112X
102L00000X
225XP0200X
225X00000X
2085D0003X

Related Payer Policy Updates

Specialty: Radiation Oncology1 / 2

10 rows

Policy	Payer	Effective Date
Radiation oncology coverage and treatment delivery guidelines	evicore	2026-11-05
Proton Beam Therapy	universityofutahhealthplans	2026-10-25
Radiation and Oncologic Procedures	UnitedHealthcare	2026-09-01
Electronic Brachytherapy for Nonmelanoma Skin Cancer	Bluecross Idaho	2026-07-30
Surface Radiation Therapy for Treatment of Non-Melanoma Skin Cancer	eocco	2026-07-09
Radiofrequency Ablation of Tumors Outside the Liver	Providence Health Plan	2026-07-01
Therapeutic Radiopharmaceuticals in Oncology (Lutathera, Pluvicto, Xofigo) Coverage Criteria	Blue Cross Blue Shield - North Carolina	2026-07-01
Intensity Modulated Radiation Therapy	Ambetter Georgia	2026-06-01
Irreversible Electroporation (IRE) of Tumors Other Than Liver	Blue Cross Blue Shield - Rhode Island	2026-06-01
Irreversible Electroporation (IRE) — NanoKnife (Preauthorization Required)	Blue Cross Blue Shield - Nebraska	2026-06-01

Related Codes

CPT-77300-RADIATION-THERAPY-DOSIMETRY

CPT 77300: Radiation Dosimetry and Treatment Planning

CPT-77301-INTENSITY-MODULATED-RADIOTHERAPY-IMRT-DELIVERY

CPT 77301: Intensity-Modulated Radiotherapy (IMRT) Delivery

CPT-77306-RADIATION-THERAPY-BEAM-ARRANGEMENT-DOSE-CALCULATION

CPT 77306: Parallel Opposed External Beam Radiation Treatment Setup

CPT-77307-RADIATION-THERAPY-ISODOSE-TANGENTIAL-PORT-PLANNING

CPT 77307: Tangential Ports and Isodose Beam Arrangement for Radiation Therapy

CPT-77316-BRACHYTHERAPY-SIMPLE-ISODOSE-PLANNING

CPT 77316: Simple Level Isodose Planning for Brachytherapy

CPT-77317-INTERMEDIATE-BRACHYTHERAPY-ISODOSE-PLANNING

CPT 77317: Intermediate Isodose Planning for Brachytherapy

CPT-77318-INTERMEDIATE-ISODOSE-BRACHYTHERAPY-PLANNING

CPT 77318: Brachytherapy Isodose Planning, Intermediate

CPT-77321-ELECTRON-SPECIAL-BEAM-PLANNING-RADIATION-ONCOLOGY

CPT 77321: Radiation Therapy Planning — Special Beam Consideration

CPT-77332-SIMPLE-TREATMENT-DEVICE-DESIGN-SELECTION

CPT 77332: Simple Treatment Device Design and Selection

CPT-77333-RADIATION-THERAPY-INTERMEDIATE-DEVICE-DESIGN

CPT 77333: Design/Construction of Intermediate Radiation Therapy Devices

Showing 1–10 of 14

Frequently Asked Questions

References

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.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.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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State Reimbursement Rates

State: Alaska1 / 51

Rate by payer

Clinical & Coding Specifications

Clinical Context

Related CPT Codes

CPT Code	Description	Relationship to This Procedure
`77301`	IMRT treatment planning (development of an IMRT plan)	`77331` is bundled into payment for `77301` when dosimetry is provided as part of IMRT planning and should not be reported separately in that context.

Related Modifiers

9 rows

Modifier	Description	When to Use
26	Modifier 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…
77	Modifier 77 indicates that a previously performed procedure or service was legitimately repeated by a different physician or other qualified health care professional. The AMA’s CPT definition…	- Use modifier 77 when a basic procedure or service already performed is repeated by a different physician or other qualified health care professional (for example, a second provider independently…
59	Modifier 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…
52	Modifier ‑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…
53	Modifier 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…
76	Modifier -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…
78	CPT modifier -78 indicates an unplanned, related return to the operating or procedure room by the same provider during the global postoperative period. It is appended when treatment for a…	- Use modifier -78 when an unplanned, related complication during the original procedure’s global postoperative period requires the patient to return to a formal operating or procedure room and the…
22	Modifier –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…
62	Modifier 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…

Related Provider Taxonomies

8 rows

Taxonomy Code
2085R0001X
2085N0904X
2085B0100X
261QS0112X
102L00000X
225XP0200X
225X00000X
2085D0003X

Related Payer Policy Updates

Specialty: Radiation Oncology1 / 2

10 rows

Policy	Payer	Effective Date
Radiation oncology coverage and treatment delivery guidelines	evicore	2026-11-05
Proton Beam Therapy	universityofutahhealthplans	2026-10-25
Radiation and Oncologic Procedures	UnitedHealthcare	2026-09-01
Electronic Brachytherapy for Nonmelanoma Skin Cancer	Bluecross Idaho	2026-07-30
Surface Radiation Therapy for Treatment of Non-Melanoma Skin Cancer	eocco	2026-07-09
Radiofrequency Ablation of Tumors Outside the Liver	Providence Health Plan	2026-07-01
Therapeutic Radiopharmaceuticals in Oncology (Lutathera, Pluvicto, Xofigo) Coverage Criteria	Blue Cross Blue Shield - North Carolina	2026-07-01
Intensity Modulated Radiation Therapy	Ambetter Georgia	2026-06-01
Irreversible Electroporation (IRE) of Tumors Other Than Liver	Blue Cross Blue Shield - Rhode Island	2026-06-01
Irreversible Electroporation (IRE) — NanoKnife (Preauthorization Required)	Blue Cross Blue Shield - Nebraska	2026-06-01

Related Codes

CPT-77300-RADIATION-THERAPY-DOSIMETRY

CPT 77300: Radiation Dosimetry and Treatment Planning

CPT-77301-INTENSITY-MODULATED-RADIOTHERAPY-IMRT-DELIVERY

CPT 77301: Intensity-Modulated Radiotherapy (IMRT) Delivery

CPT-77306-RADIATION-THERAPY-BEAM-ARRANGEMENT-DOSE-CALCULATION

CPT 77306: Parallel Opposed External Beam Radiation Treatment Setup

CPT-77307-RADIATION-THERAPY-ISODOSE-TANGENTIAL-PORT-PLANNING

CPT 77307: Tangential Ports and Isodose Beam Arrangement for Radiation Therapy

CPT-77316-BRACHYTHERAPY-SIMPLE-ISODOSE-PLANNING

CPT 77316: Simple Level Isodose Planning for Brachytherapy

CPT-77317-INTERMEDIATE-BRACHYTHERAPY-ISODOSE-PLANNING

CPT 77317: Intermediate Isodose Planning for Brachytherapy

CPT-77318-INTERMEDIATE-ISODOSE-BRACHYTHERAPY-PLANNING

CPT 77318: Brachytherapy Isodose Planning, Intermediate

CPT-77321-ELECTRON-SPECIAL-BEAM-PLANNING-RADIATION-ONCOLOGY

CPT 77321: Radiation Therapy Planning — Special Beam Consideration

CPT-77332-SIMPLE-TREATMENT-DEVICE-DESIGN-SELECTION

CPT 77332: Simple Treatment Device Design and Selection

CPT-77333-RADIATION-THERAPY-INTERMEDIATE-DEVICE-DESIGN

CPT 77333: Design/Construction of Intermediate Radiation Therapy Devices

Showing 1–10 of 14

Frequently Asked Questions

References

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.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.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.

Published by

Trek Health powers OpenPayer with a leading commercial payer intelligence platform, seamlessly converting fragmented payer data into actionable insights for provider organizations.

CPT 77331: Special Dosimetry and Radiation Monitoring

Sign up for cpt 77331 policy alerts

National Reimbursement Benchmarks

CPT 77331: Special Dosimetry and Radiation Monitoring

Sign up for cpt 77331 policy alerts

National Reimbursement Benchmarks

State Reimbursement Rates

Clinical & Coding Specifications

Clinical Context

Related CPT Codes

Related Modifiers

Related Provider Taxonomies

Related Payer Policy Updates

Related Codes

What clinical purpose does CPT 77331 serve?

Where is CPT 77331 typically performed?

Can CPT 77331 be billed separately from IMRT planning (CPT 77301)?

Which modifiers are commonly used with CPT 77331 and when are they appropriate?

How do reimbursement rates for CPT 77331 compare between Medicare and commercial payers?

References

State Reimbursement Rates

Clinical & Coding Specifications

Clinical Context

Related CPT Codes

Related Modifiers

Related Provider Taxonomies

Related Payer Policy Updates

Related Codes

What clinical purpose does CPT 77331 serve?

Where is CPT 77331 typically performed?

Can CPT 77331 be billed separately from IMRT planning (CPT 77301)?

Which modifiers are commonly used with CPT 77331 and when are they appropriate?

How do reimbursement rates for CPT 77331 compare between Medicare and commercial payers?

References