CPT code 77331: Radiation dosimetry, special measurement2026 Medicare rate & RVUs in Louisiana
Reports specialized radiation dose measurement, such as TLD-based dosimetry, when a radiation oncology team needs more than routine treatment-planning calculations.
Medicare pays $61.03–$63.29 for 77331 in the office in Louisiana, from Rest of Louisiana to New Orleans, LA. Which amount applies depends on the service address.
Medicare allowed amount for participating (non-QP) physicians, before deductible, coinsurance and claim adjustments. Not a patient’s bill or a hospital charge.
Your location
On this page 9 sections
What 77331 covers
This service covers specialized measurement of radiation dose, including methods such as thermoluminescent dosimetry (TLD) or microdosimetry. A radiation oncology physicist typically performs or interprets the work, with technical staff and measurement equipment supporting the test. It may be used when the team needs a patient-specific dose measurement or verification beyond routine dose calculations in a radiation treatment plan.
Select the code for the specialized measurement actually performed, not simply because a treatment plan includes dose calculations. Documentation should identify the measurement method, its clinical purpose, and the findings or interpretation. CMS treats the service as having professional and technical components: report modifier 26 for the interpretation, modifier TC for the equipment and staff, or neither modifier when billing the global service. The record should support the component billed and show that the specialized measurement was performed.
This summary was written with AI assistance from CMS physician fee schedule data and checked against the CMS billing rules shown here. Rates on this page come directly from CMS files.
Where 77331 pays more and less in Louisiana
| Payment locality | Office | Facility |
|---|---|---|
| New Orleans, LA | $63.29 | Unavailable |
| Rest of Louisiana | $61.03 | Unavailable |
How the 77331 rate is calculated
Each of 77331’s three RVUs is multiplied by a geographic index (GPCI) for the payment locality, added up, and multiplied by the conversion factor. Drag the indexes or enter a ZIP to see what moves the rate.
How the rate is built · 77331
RVUs × geographic indexes × conversion factor
Work0.85
0.85 RVUs× 1.000 GPCI
Practice expense1.05
1.05 RVUs× 1.000 GPCI
Malpractice0.05
0.05 RVUs× 1.000 GPCI
Adjusted RVUs
1.9500
Conversion factor
$33.4009
Medicare rate
$65.13
Every GPCI starts at 1.000, the national rate. Enter a ZIP or drag a slider.
Payment rules and modifiers for 77331
The CMS indicators that decide how 77331 is paid alongside other services.
CMS payment indicators · 77331
Radiation dosimetry, special measurement
| Rule | CMS value | What it means |
|---|---|---|
| Global period | XXX | The global surgery concept doesn’t apply. |
| Multiple procedures | 0 | No multiple-procedure reduction. |
| Bilateral (modifier 50) | 0 | The 150% bilateral adjustment doesn’t apply. |
| Assistant at surgery (80/81/82/AS) | 0 | Not paid without supporting documentation. |
| Co-surgeons (62) | 0 | Not permitted. |
| Team surgery (66) | 0 | Not permitted. |
| Professional/technical | 1 | Diagnostic test with separate professional (26) and technical (TC) components. |
What modifiers do to the payment
Modifier 26 · payment effect
With and without the modifier
77331 without 26 · national office
$65.13
Radiation dosimetry, special measurement
77331-26 · Professional component
$45.76
Pays only the interpretation and report.
77331 compared with similar codes
Compare codes · National
4 codes, side by side
How to choose
- 77300Dosimetry calculationBasic, per calculation
- 77300 represents routine radiation dose calculation. Choose 77331 when specialized measurement, such as TLD or microdosimetry, is performed.
- 77321Radiation planSpecial port plan
- 77321 is for a special teletherapy port plan. It addresses treatment planning, while 77331 represents specialized dose measurement.
- 77370Radiation physics consultUnusual treatment circumstances
- 77370 represents a special radiation physics consultation. Use 77331 for a specialized dose measurement, not merely a physics review or consultation.
77331 billing questions
How is this different from 77300?
Use 77300 for routine radiation dose calculations. Report 77331 when specialized measurement, such as TLD or microdosimetry, is performed rather than relying only on those calculations.
Which modifier identifies the interpretation?
Append modifier 26 for the professional interpretation. Modifier TC identifies the technical component, including equipment and staff; billing without either modifier represents the global service.
What documentation supports reporting 77331?
Document the specialized measurement method, why it was needed, and the measured results or interpretation. The record should make clear that the work was more than routine treatment-planning calculation.
Can 77331 be reported with a radiation dose plan?
It may accompany a dose-planning service when the specialized measurement is a distinct service actually performed. The record should distinguish the measurement from the plan's routine calculations.
Does this code describe a radiation treatment aid?
No. It describes specialized dose measurement; codes 77332–77334 describe radiation treatment aids, such as devices used to shape or support treatment delivery.
Where these rates come from
FeeBase calculates base physician payments from CMS work, practice-expense and malpractice RVUs, adjusted by each locality’s geographic indexes and the conversion factor. Services without a published rate are labeled, never given a made-up amount. Amounts are Medicare allowed amounts before claim adjustments: not a patient’s bill or a commercial rate.
CMS RVU26D · effective Oct 1, 2026 through the day before Jan 1, 2027
Show the CMS file lines behind this rate
Fee sheets
Put 77331 and the rest of your codes on one sheet
Your codes at your locality, with payer contracts beside Medicare.
Build my fee sheet