Billing code 78645: CSF shunt studyMedicare rate & RVUs in Illinois
Nuclear medicine imaging tracks radiotracer movement through a cerebrospinal fluid shunt to investigate suspected impaired flow or shunt malfunction.
Medicare pays $263.79–$294.56 for 78645 in the office in Illinois, from Rest Of Illinois to Suburban Chicago. 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.
On this page 9 sections
What 78645 covers
This study evaluates flow through an implanted cerebrospinal fluid shunt, commonly when symptoms or other findings raise concern for obstruction or malfunction. A nuclear medicine team administers radiotracer through the shunt access point and obtains images to follow its movement through the shunt pathway. The study may help assess whether flow is occurring and where it appears impaired.
Report 78645 for the shunt-focused radionuclide evaluation, rather than a study directed at general CSF circulation, ventricular imaging, or leak localization. Documentation should identify the clinical concern, the shunt evaluated, the radiotracer administration and imaging performed, and the interpretation of tracer progression. CMS recognizes professional and technical components: report modifier 26 for the interpretation, modifier TC for equipment and staff, or no component modifier for the global service. The professional and technical components are separately priced.
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 78645 pays more and less in Illinois
The same RVUs, adjusted for each area’s costs. Open a locality for its calculation, history and nearby areas.
4 payment localities
$263.79 to $294.56
| Payment locality | Office | Facility |
|---|---|---|
| Chicago | $290.15 | Unavailable |
| East St. Louis | $266.84 | Unavailable |
| Rest Of Illinois | $263.79 | Unavailable |
| Suburban Chicago | $294.56 | Unavailable |
How the 78645 rate is calculated
Each of 78645’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 · 78645
RVUs × geographic indexes × conversion factor
Swap in your local Medicare rate.
Work 0.56Practice expense 7.90Malpractice 0.08
All indexes start at 1.000 (the national rate). Enter a ZIP or drag a slider.
Payment rules and modifiers for 78645
The CMS indicators that decide how 78645 is paid alongside other services.
CMS payment indicators · 78645
CSF shunt study
| 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
78645 without 26 · national office
$285.24
CSF shunt study
78645-26 · Professional component
$25.72
Pays only the interpretation and report.
78645 compared with similar codes
Compare codes
78645 vs 78630 vs 78635 vs 78650: national Medicare rates
Swap in your local Medicare rate.
How to choose
- 78630CSF scan
- Choose 78645 for radionuclide evaluation of an implanted shunt. Code 78630 addresses CSF circulation through cisternography.
- 78635CSF imaging
- Code 78635 is directed at ventricular CSF imaging; 78645 follows tracer through a CSF shunt.
- 78650CSF leak imaging
- Code 78650 is used for imaging directed at CSF leakage. Use 78645 when the clinical question concerns shunt flow or patency.
78645 billing questions
When should I report 78645 instead of a CSF cisternography code?
Report 78645 when the imaging evaluates flow through an implanted CSF shunt. Cisternography evaluates CSF circulation rather than shunt patency.
How do I report the professional and technical portions?
Use modifier 26 for the professional interpretation and modifier TC for the technical service. Without either modifier, the claim represents the global service.
What documentation supports 78645?
Document the suspected shunt problem, the shunt evaluated, radiotracer administration, the imaging performed, and the interpreting clinician’s findings about tracer progression.
Is this the right code for locating a CSF leak?
No. 78645 evaluates an implanted shunt; code 78650 is associated with CSF leak imaging.
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
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