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CPT code 78635: CSF imaging, ventricular flow study2026 Medicare rate & RVUs in Iowa

Nuclear imaging tracks radiotracer movement through ventricular cerebrospinal fluid when clinicians need to assess flow within the brain’s ventricular system.

CMS RVU26DEffective Oct 1, 2026One payment locality

In Iowa, Medicare pays $269.85 for 78635 in the office.

$269.85Office (non-facility)
Not available in this settingHospital or facility
−8.4%vs the national office rate ($294.60)

Check a contract rate as a % of Medicare · 78635 nationwide

Medicare allowed amount for participating (non-QP) physicians, before deductible, coinsurance and claim adjustments. Not a patient’s bill or a hospital charge.

We’ll open 78635 for the payment locality that covers the ZIP.

On this page 11 sections
  1. Rate in Iowa
  2. What 78635 covers
  3. Compared with other areas
  4. Rate map
  5. How it’s calculated
  6. Payment rules
  7. Related codes
  8. Rate history
  9. Where it applies
  10. Billing questions
  11. Sources

What 78635 covers

This nuclear medicine study follows radiotracer distribution through cerebrospinal fluid in the ventricular system. It is used when clinicians need information about ventricular CSF flow, such as in evaluating a suspected flow abnormality. A nuclear medicine physician interprets the images; the study may involve ventricular access for tracer administration, with imaging performed in a nuclear medicine department.

Report 78635 for the ventricular CSF imaging service, rather than a general brain scan or a study focused on shunt function or CSF leakage. The record should support the clinical question, tracer administration and access route, images obtained, and the physician’s interpretation. CMS recognizes a professional component, reported with modifier 26 for interpretation, and a technical component, reported with modifier TC for equipment and staff. Without either modifier, the claim represents the global service.

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.

How Iowa compares for 78635

Across 109 of 109 payment localities, the office rate for 78635 runs from $254.92 in Arkansas to $415.84 in San Benito County, CA. Iowa pays $269.85. The RVUs are the same everywhere; the geographic indexes change the dollars.

78635 in Iowa vs other payment areas
  1. Iowa · this page$269.85
  2. Los Angeles, CA · California$344.32+$74.47
  3. Washington, DC area · District of Columbia$344.42+$74.57
  4. Miami, FL · Florida$309.84+$39.99
  5. Chicago, IL · Illinois$299.56+$29.71
  6. Manhattan, NY · New York$341.52+$71.67
  7. Alaska · Alaska$320.94+$51.09

Other areas in Iowa first, then benchmark localities. Bars start at $0.

Every other payment area

78635 in every other Medicare payment locality
Payment localityOfficeFacility
AlabamaAlabama$259.41—
ArkansasArkansas$254.92—
ArizonaArizona$285.77—
Bakersfield, CACalifornia$320.06—
Chico, CACalifornia$319.82—
El Centro, CACalifornia$319.84—
Fresno, CACalifornia$319.82—
Hanford, CACalifornia$319.82—

78635 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.

$254.92

$367.83

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

View every state and territory as a table
78635 office rate range by state
State / territoryOffice rate rangeLocalities
AK$320.941
AL$259.411
AR$254.921
AZ$285.771
CA$319.82–$415.8429
CO$311.671
CT$316.511
DC$344.421
DE$291.161
FL$283.96–$309.843
GA$265.71–$299.552
GU$330.761
HI$330.761
IA$269.851
ID$271.411
IL$272.42–$304.154
IN$273.351
KS$267.141
KY$264.151
LA$263.18–$278.902
MA$308.80–$347.922
MD$297.84–$344.423
ME$271.81–$291.162
MI$271.26–$286.902
MN$300.611
MO$256.96–$281.533
MS$256.061
MT$294.591
NC$275.391
ND$293.011
NE$271.971
NH$305.421
NJ$320.69–$339.572
NM$272.541
NV$294.421
NY$280.19–$349.605
OH$270.931
OK$264.871
OR$292.71–$324.442
PA$272.13–$306.632
PR$297.551
RI$303.661
SC$273.511
SD$292.821
TN$268.591
TX$269.91–$310.128
UT$277.991
VA$289.18–$344.422
VI$297.551
VT$290.551
WA$308.64–$356.892
WI$281.311
WV$260.091
WY$293.901

See 78635 in every payment locality

How the 78635 rate is calculated

Each of 78635’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 · 78635

RVUs × geographic indexes × conversion factor

Office or facility?

Work0.59

0.59 RVUs× 1.000 GPCI

Practice expense8.15

8.15 RVUs× 1.000 GPCI

Malpractice0.08

0.08 RVUs× 1.000 GPCI

Adjusted RVUs

8.8200

Conversion factor

$33.4009

Medicare rate

$294.60

Every GPCI starts at 1.000, the national rate. Enter a ZIP or drag a slider.

The exact Iowa inputs and CMS source lines

PPRRVU2026_Oct_nonQPP.csv

9,467

Code
78635
Physician work
0.59
Practice expense
8.15
Malpractice
0.08

GPCI2026.csv

53

Locality
Iowa
Physician work
1.000
Practice expense
0.915
Malpractice
0.397
Office calculation for 78635 in Iowa
ComponentRVULocality factorAdjusted
Physician work0.59× 1.0000.5900
Practice expense8.15× 0.9157.4573
Malpractice0.08× 0.3970.0318
Total RVUs8.0790
Conversion factor× 33.4009

Office rate, Iowa$269.85

Office: (0.59 × 1 + 8.15 × 0.915 + 0.08 × 0.397) × $33.4009 = $269.85

Open 78635 in the RVU calculator

Payment rules and modifiers for 78635

The CMS indicators that decide how 78635 is paid alongside other services.

CMS payment indicators · 78635

CSF imaging, ventricular flow study

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

78635 without 26 · national office

$294.60

CSF imaging, ventricular flow study

78635-26 · Professional component

$28.06

Pays only the interpretation and report.

When to use modifier 26

Codes related to 78635

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

Codes related to 78635
CodeHow it relatesOffice range, Iowa
Used instead
78630CSF scan, cisternographyCSF imaging for a different circulation assessment and administration approach.$269.70
78645CSF shunt study, shunt patency assessmentUsed when the clinical question is CSF shunt function.$261.20
78650CSF leak imaging, leak detection and localizationUsed to image suspected CSF leakage rather than ventricular flow.$224.79

How 78635 has changed in Iowa

78635 · Office / nonfacility

$269.85

Effective 2026-10-01

The base rate is $1.75 higher than on 2025-10-01, moving from $268.10 to $269.85 (0.7%).

It is unchanged from the immediately preceding available release, effective 2026-07-01.

Base rate by release · bars start at $0 · select a bar to compare

One bar per available release, ordered by effective date. Missing rates remain gaps. These comparisons hold the code, setting and locality identifiers constant; they do not isolate which policy or input caused a change.

What changed, release by release

  1. January 1, 2026

    RVU26A

    $268.10changed to$269.85

    • Conversion factor 32.3465 changed to 33.4009
    • Work RVU 0.61 changed to 0.59
    • Practice expense RVU 8.37 changed to 8.15
    • Practice expense GPCI 0.913 changed to 0.915
    • Malpractice GPCI 0.457 changed to 0.397

    Held through RVU26B, RVU26C, RVU26D.

  2. January 1, 2025

    RVU25A

    $281.83changed to$268.10

    • Conversion factor 33.2875 changed to 32.3465
    • Practice expense RVU 8.56 changed to 8.37
    • Malpractice RVU 0.09 changed to 0.08

    Held through RVU25B, RVU25C, RVU25D.

  3. March 9, 2024

    RVU24AR

    $277.23changed to$281.83

    • Conversion factor 32.7442 changed to 33.2875

    Held through RVU24B, RVU24C, RVU24D.

  4. January 1, 2024

    RVU24A

    $291.08changed to$277.23

    • Conversion factor 33.8872 changed to 32.7442
    • Practice expense RVU 8.73 changed to 8.56
    • Malpractice RVU 0.08 changed to 0.09
    • Practice expense GPCI 0.910 changed to 0.913
    • Malpractice GPCI 0.441 changed to 0.457

  5. January 1, 2023

    RVU23A

    $300.22changed to$291.08

    • Conversion factor 34.6062 changed to 33.8872
    • Practice expense RVU 8.85 changed to 8.73
    • Malpractice RVU 0.09 changed to 0.08
    • Practice expense GPCI 0.907 changed to 0.910
    • Malpractice GPCI 0.425 changed to 0.441

    Held through RVU23B, RVU23C, RVU23D.

  6. January 1, 2022

    RVU22A

    $315.05changed to$300.22

    • Conversion factor 34.8931 changed to 34.6062
    • Practice expense RVU 9.24 changed to 8.85

    Held through RVU22B, RVU22C, RVU22D.

  7. January 1, 2021

    RVU21A

    $316.86changed to$315.05

    • Conversion factor 36.0896 changed to 34.8931
    • Practice expense RVU 8.97 changed to 9.24
    • Malpractice RVU 0.08 changed to 0.09
    • Malpractice GPCI 0.424 changed to 0.425

    Held through RVU21B, RVU21C, RVU21D.

  8. January 1, 2020

    RVU20A

    $320.01changed to$316.86

    • Conversion factor 36.0391 changed to 36.0896
    • Practice expense RVU 9.08 changed to 8.97
    • Malpractice GPCI 0.423 changed to 0.424

    Held through RVU20B, RVU20C, RVU20D.

  9. January 1, 2019

    RVU19A

    $325.21changed to$320.01

    • Conversion factor 35.9996 changed to 36.0391
    • Practice expense RVU 9.25 changed to 9.08

    Held through RVU19B, RVU19C, RVU19D.

  10. January 1, 2018

    RVU18AR1

    $324.91changed to$325.21

    • Conversion factor 35.8887 changed to 35.9996
    • Practice expense RVU 9.32 changed to 9.25
    • Practice expense GPCI 0.902 changed to 0.907
    • Malpractice GPCI 0.458 changed to 0.423

    Held through RVU18B, RVU18C, RVU18D.

  11. January 1, 2017

    RVU17A

    $318.22changed to$324.91

    • Conversion factor 35.8043 changed to 35.8887
    • Practice expense RVU 9.20 changed to 9.32
    • Malpractice RVU 0.07 changed to 0.08
    • Practice expense GPCI 0.896 changed to 0.902
    • Malpractice GPCI 0.493 changed to 0.458

    Held through RVU17B, RVU17C, RVU17D.

  12. January 1, 2016

    RVU16A

    $319.54changed to$318.22

    • Conversion factor 35.9335 changed to 35.8043
    • Malpractice RVU 0.08 changed to 0.07

    Held through RVU16B, RVU16C, RVU16D.

  13. July 1, 2015

    RVU15C

    $317.95changed to$319.54

    • Conversion factor 35.7547 changed to 35.9335

    Held through RVU15D.

  14. January 1, 2015

    RVU15A

    $310.44changed to$317.95

    • Conversion factor 35.8228 changed to 35.7547
    • Practice expense RVU 9.01 changed to 9.20
    • Malpractice RVU 0.04 changed to 0.08
    • Practice expense GPCI 0.892 changed to 0.896
    • Malpractice GPCI 0.475 changed to 0.493

    Held through RVU15B.

  15. January 1, 2014

    RVU14A

    $311.09changed to$310.44

    • Conversion factor 34.0230 changed to 35.8228
    • Practice expense RVU 9.60 changed to 9.01
    • Practice expense GPCI 0.887 changed to 0.892
    • Malpractice GPCI 0.456 changed to 0.475

    Held through RVU14B, RVU14C, RVU14D.

  16. January 1, 2013

    RVU13AR

    Earliest loaded release: $311.09

    Held through RVU13B, RVU13C, RVU13D.

Rates in every CMS release
Effective fromOfficeFacilityCMS release
2026-10-01$269.85Not available in this settingRVU26D
2026-07-01$269.85Not available in this settingRVU26C
2026-04-01$269.85Not available in this settingRVU26B
2026-01-01$269.85Not available in this settingRVU26A
2025-10-01$268.10Not available in this settingRVU25D
2025-07-01$268.10Not available in this settingRVU25C
2025-04-01$268.10Not available in this settingRVU25B
2025-01-01$268.10Not available in this settingRVU25A
2024-10-01$281.83Not available in this settingRVU24D
2024-07-01$281.83Not available in this settingRVU24C
2024-04-01$281.83Not available in this settingRVU24B
2024-03-09$281.83Not available in this settingRVU24AR
2024-01-01$277.23Not available in this settingRVU24A
2023-10-01$291.08Not available in this settingRVU23D
2023-07-01$291.08Not available in this settingRVU23C
2023-04-01$291.08Not available in this settingRVU23B
2023-01-01$291.08Not available in this settingRVU23A
2022-10-01$300.22Not available in this settingRVU22D
2022-07-01$300.22Not available in this settingRVU22C
2022-04-01$300.22Not available in this settingRVU22B
2022-01-01$300.22Not available in this settingRVU22A
2021-10-01$315.05Not available in this settingRVU21D
2021-07-01$315.05Not available in this settingRVU21C
2021-04-01$315.05Not available in this settingRVU21B
2021-01-01$315.05Not available in this settingRVU21A
2020-10-01$316.86Not available in this settingRVU20D
2020-07-01$316.86Not available in this settingRVU20C
2020-04-01$316.86Not available in this settingRVU20B
2020-01-01$316.86Not available in this settingRVU20A
2019-10-01$320.01Not available in this settingRVU19D
2019-07-01$320.01Not available in this settingRVU19C
2019-04-01$320.01Not available in this settingRVU19B
2019-01-01$320.01Not available in this settingRVU19A
2018-10-01$325.21Not available in this settingRVU18D
2018-07-01$325.21Not available in this settingRVU18C
2018-04-01$325.21Not available in this settingRVU18B
2018-01-01$325.21Not available in this settingRVU18AR1
2017-10-01$324.91Not available in this settingRVU17D
2017-07-01$324.91Not available in this settingRVU17C
2017-04-01$324.91Not available in this settingRVU17B
2017-01-01$324.91Not available in this settingRVU17A
2016-10-01$318.22Not available in this settingRVU16D
2016-07-01$318.22Not available in this settingRVU16C
2016-04-01$318.22Not available in this settingRVU16B
2016-01-01$318.22Not available in this settingRVU16A
2015-10-01$319.54Not available in this settingRVU15D
2015-07-01$319.54Not available in this settingRVU15C
2015-04-01$317.95Not available in this settingRVU15B
2015-01-01$317.95Not available in this settingRVU15A
2014-10-01$310.44Not available in this settingRVU14D
2014-07-01$310.44Not available in this settingRVU14C
2014-04-01$310.44Not available in this settingRVU14B
2014-01-01$310.44Not available in this settingRVU14A
2013-10-01$311.09Not available in this settingRVU13D
2013-07-01$311.09Not available in this settingRVU13C
2013-04-01$311.09Not available in this settingRVU13B
2013-01-01$311.09Not available in this settingRVU13AR

Price 78635 for an earlier date of service

Where the Iowa rate applies

Iowa is a Medicare payment area, not a city. Our Census mapping connects it to 1026 cities and communities in Iowa. Some span more than one payment area; confirm with the service ZIP.

  • Ackley
  • Ackworth
  • Adair
  • Adel
  • Afton
  • Agency
  • Ainsworth
  • Akron

Browse all communities in Iowa

78635 billing questions

How does 78635 differ from a CSF scan?

78635 describes imaging focused on CSF movement through the ventricular system. A CSF scan such as 78630 is used for a different CSF imaging approach and clinical question.

When should 78645 be considered instead?

Use 78645 when the study evaluates CSF shunt function. Code 78635 describes ventricular CSF imaging, not a shunt-specific evaluation.

Can the professional and technical portions be billed separately?

Yes. Report modifier 26 for the physician’s interpretation or TC for the technical service, which includes equipment and staff. Billing without a modifier represents the global service.

What documentation supports reporting 78635?

Document the reason for evaluating ventricular CSF flow, the tracer administration and access route, the imaging performed, and the interpreting physician’s findings.

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 78635PPRRVU2026_Oct_nonQPP.csv, line 9,467 (RVU26D)
Geographic factors for IowaGPCI2026.csv, line 53 (RVU26D)

Open CMS sourceHow we calculate rates

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