CPT 78635Radiology

Csf ventriculography

CPT code 78635 covers cerebrospinal fluid (CSF) ventriculography, a nuclear medicine imaging procedure that uses radioactive tracers to visualize the fluid-filled spaces (ventricles) within the brain and assess CSF flow patterns.

Showing rates for

National Average

Base Medicare rate

$293.06

This calculator gives a typical-case estimate using standard Medicare modifier rules. Actual payment depends on payer policies, documentation, code-specific CMS status indicators, and locality. Verify before billing.

RVU breakdown

Work RVU

0.61

PE RVU (NF)

8.37

MP RVU

0.08

Total RVU

9.06

Conversion factor: 32.3465 · Source: CMS MPFS RVU25A · Confidence: High

NCCI bundling edits

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Billing tips

Always verify that the radiopharmaceutical administration is separately billable and document the specific isotope used (typically In-111 DTPA) with dosage and time of injection
Impact: Proper radiopharmaceutical billing can add $150-400 to total reimbursement depending on the agent used
Document all imaging time points (immediate, delayed at 2-4 hours, 24 hours, and sometimes 48-72 hours) as Medicare considers the complete study to include serial imaging
Impact: Incomplete imaging series documentation can result in downcoding or denial of the entire $293.06 claim
Link to specific ICD-10 codes that support medical necessity such as G91.x (hydrocephalus codes), G96.0 (CSF leak), or T85.03xA (shunt malfunction) rather than generic symptoms
Impact: Improper diagnosis linkage is responsible for approximately 30% of denials for this code
When performed in conjunction with shunt evaluation, ensure that any related procedures (such as shunt tap) are documented as separate and distinct services with modifier 59 if billed together
Impact: Prevents bundling denials that could reduce total reimbursement by 50% or more
Bill facility versus non-facility based on actual place of service; both have identical rates ($293.06) for this code, but POS code must be accurate
Impact: Incorrect place of service coding can trigger audit flags even when payment amount is identical
Document physician presence during radiopharmaceutical injection and personal interpretation of all imaging phases, not just final report signature
Audit risk mitigation; incomplete supervision documentation can require refund of entire professional component

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Frequently asked questions

What is the Medicare reimbursement rate for CPT 78635 in 2025?

The 2025 Medicare national average reimbursement for CPT 78635 is $293.06 for both facility and non-facility settings. This rate is based on 9.06 total RVUs (0.61 work RVU + 8.37 PE RVU + 0.08 MP RVU) multiplied by the 2025 conversion factor of 32.3465.

How often can CPT 78635 be billed for the same patient?

There is no absolute frequency limitation for CPT 78635, but repeat studies require clear documentation of medical necessity, such as interim clinical changes, shunt revision, new symptoms, or treatment monitoring. Most payers expect at least 3-6 months between studies unless there is documented acute clinical deterioration or surgical intervention.

Can CPT 78635 be billed with modifier 26 for professional component only?

Yes, CPT 78635 can be split into professional (modifier 26) and technical (modifier TC) components. This is common when a radiologist provides only the interpretation while the hospital bills for the technical equipment and staff. Each entity bills their respective component of the $293.06 total allowable.

What diagnosis codes support medical necessity for CPT 78635?

Common supporting diagnosis codes include G91.x series (hydrocephalus types), G96.0 (CSF leak from spinal puncture), T85.03xA (mechanical complication of ventricular shunt), G93.2 (benign intracranial hypertension), and G91.2 (normal pressure hydrocephalus). The diagnosis must justify why nuclear medicine imaging is necessary over CT or MRI.

Is CPT 78635 the same as a CSF flow study or cisternography?

No, CPT 78635 specifically describes CSF ventriculography focusing on the ventricular system. Cisternography (CPT 78630) evaluates the basal cisterns and general CSF circulation. While both use radiopharmaceutical tracers, they have different injection sites, imaging protocols, and clinical indications. Do not confuse or interchange these codes.

What radiopharmaceutical is typically used for CPT 78635?

Indium-111 DTPA (In-111 diethylenetriaminepentaacetic acid) is the most common radiopharmaceutical for CSF ventriculography. The radiopharmaceutical itself is billed separately using appropriate HCPCS codes (typically A9547 for In-111) and is not included in the CPT 78635 reimbursement of $293.06.

What are the work RVUs for CPT 78635 in 2025?

CPT 78635 has 0.61 work RVUs, 8.37 practice expense RVUs, and 0.08 malpractice RVUs for a total of 9.06 RVUs in 2025. The work RVU reflects the physician time, technical skill, mental effort, and stress associated with interpreting the ventriculography study and managing the patient encounter.