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CPT code 77331: Radiation dosimetry, special measurement2026 Medicare rate & RVUs

Reports specialized radiation dose measurement, such as TLD-based dosimetry, when a radiation oncology team needs more than routine treatment-planning calculations.

CMS RVU26DEffective Oct 1, 2026109 payment localities23.6K Medicare services in 2024

Medicare pays $65.13 for 77331 nationally in the office. Local office rates run $59.38–$82.98.

Medicare rate · 77331

Radiation dosimetry, special measurement

Office or facility?

Work RVUs
0.85
Total RVUs
1.95
Global days
XXX

National rate · 2026

$65.13

Office setting, before claim adjustments.

See every locality for 77331 →Billed by an NP, PA or therapist? →

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

Medicare pays by the payment locality where the service is performed.

On this page 10 sections
  1. Medicare rate
  2. What 77331 covers
  3. By payment locality
  4. Rate map
  5. How it’s calculated
  6. Payment rules
  7. Similar codes
  8. Related codes
  9. Billing questions
  10. Sources

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

The same RVUs, adjusted for each area’s costs. Open a locality for its calculation, history and nearby areas.

109 payment localities

$59.38 to $82.98

$59.38$71.18$82.98
One dot per payment locality, office / nonfacility. Hover a dot to see the locality; select it to open that rate.

109 of 109 payment localities

77331 office and facility rates by payment locality
Payment localityOfficeFacility
Alabama$60.02Unavailable
Alaska$80.86Unavailable
Arizona$63.80Unavailable
Arkansas$59.38Unavailable
Atlanta, GA$66.11Unavailable
Austin, TX$67.03Unavailable
Bakersfield, CA$68.39Unavailable
Baltimore area, MD$68.54Unavailable
Beaumont, TX$61.86Unavailable
Brazoria, TX$64.68Unavailable

77331 rates by state

Office rate range in each state. Select a state to see its payment localities.

MEWIVTNHMTNDMNMINYMARIWAIDWYSDIAILINOHPANJCTORNVUTCONEMOKYWVVAMDDECAAZNMKSOKARTNNCSCDCTXLAMSALGAFLAKHI

Explore a state

Local rates. Clear comparisons.

Hover or focus a tile to see its rate range. Select it to open the state’s fee schedule.

$59.38

$80.86

Color shows the midpoint of each state’s locality range.

View every state and territory as a table
77331 office rate range by state
State / territoryOffice rate rangeLocalities
AK$80.861
AL$60.021
AR$59.381
AZ$63.801
CA$68.21–$82.9829
CO$67.351
CT$68.751
DC$73.101
DE$64.681
FL$64.43–$69.123
GA$61.66–$66.112
GU$69.231
HI$69.231
IA$61.141
ID$61.451
IL$63.02–$67.674
IN$61.711
KS$60.941
KY$61.101
LA$61.03–$63.292
MA$67.11–$72.922
MD$65.70–$73.103
ME$61.69–$64.202
MI$62.30–$65.052
MN$64.971
MO$60.25–$63.453
MS$59.821
MT$65.131
NC$62.181
ND$64.141
NE$61.391
NH$66.361
NJ$69.66–$72.652
NM$62.561
NV$64.891
NY$62.88–$75.015
OH$62.091
OK$61.011
OR$64.50–$69.052
PA$62.16–$67.402
PR$65.491
RI$66.651
SC$62.221
SD$64.021
TN$61.171
TX$61.86–$67.038
UT$62.861
VA$64.04–$73.102
VI$65.491
VT$63.961
WA$66.96–$74.212
WI$62.501
WV$61.261
WY$64.701

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

Office or facility?

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

RuleCMS valueWhat it means
Global periodXXXThe global surgery concept doesn’t apply.
Multiple procedures0No multiple-procedure reduction.
Bilateral (modifier 50)0The 150% bilateral adjustment doesn’t apply.
Assistant at surgery (80/81/82/AS)0Not paid without supporting documentation.
Co-surgeons (62)0Not permitted.
Team surgery (66)0Not permitted.
Professional/technical1Diagnostic 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.

When to use modifier 26

77331 compared with similar codes

Compare codes · National

4 codes, side by side

Office or facility?

  • 77331

    Radiation dosimetry, special measurement0.85 wRVU

    $65.13

  • 77300

    Dosimetry calculation, basic, per calculation0.6 wRVU

    $67.14+$2.01

  • 77321

    Radiation plan, special port plan0.93 wRVU

    $94.52+$29.39

  • 77370

    Radiation physics consult, unusual treatment circumstances0 wRVU

    $150.97+$85.84

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.

Codes related to 77331

Related codes aren’t interchangeable: bill the code that matches the service performed.

Codes related to 77331
CodeHow it relatesNational office range
Used instead
77300Dosimetry calculation, basic, per calculationRoutine dose calculation; use it when specialized measurement is not performed.$60.04–$88.95
Often billed with
77321Radiation plan, special port planA special teletherapy port plan may be performed alongside a distinct dose measurement.$85.00–$124.48
77370Radiation physics consult, unusual treatment circumstancesMay accompany a separately documented, case-specific radiation physics consultation.$127.96–$213.16

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
RVUs for 77331PPRRVU2026_Oct_nonQPP.csv, line 9,071 (RVU26D)

Open CMS sourceHow we calculate rates

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