Summary & Overview

CPT 77078: CT Study of Bones for Bone Mass and Density Assessment

CPT code 77078 designates a CT-based bone imaging study used to produce high-resolution 2D and 3D cross-sectional images of skeletal structures for assessing bone mass and density. This imaging code is clinically significant for diagnosing and monitoring bone disorders such as osteoporosis, osteomalacia, and renal osteodystrophy, and supports treatment monitoring and disease progression assessment. Nationally, CT bone studies underpin diagnostic workflows where bone morphology or density measurement is required beyond conventional radiography.

Key payers included in the analysis are Aetna, Blue Cross Blue Shield, Cigna Health, UnitedHealthcare, and Medicare. The publication outlines payer coverage patterns, coding guidance, clinical context, and common billing considerations related to CT bone studies billed with CPT code 77078.

Readers will find a concise explanation of the clinical indications and typical sites of service for this study, an overview of payer inclusion and common billing modifiers, and context for how CT bone imaging fits into diagnostic pathways for bone disease. The summary highlights where 77078 is used in practice and what operational areas—imaging modality, reporting, and site of service—are most relevant for clinicians, coders, and administrators seeking clarity on this code.

AetnaBlue Cross Blue ShieldCigna HealthUnitedHealthcareMedicare77078CPTComputed TomographyBone DensityRadiologyDiagnostic ImagingOsteoporosisBone DiseaseOutpatient Imaging

Billing Code Overview

CPT code 77078 describes a computed tomography (CT) study focused on the bones, using computerized axial tomography and related digital axial imaging techniques to produce two‑dimensional and three‑dimensional cross‑sectional images of bony structures. The study evaluates bone mass and density and is used to assess diseases such as osteoporosis, osteomalacia, and renal osteodystrophy, and to monitor disease progression or response to therapy.

Service type: Diagnostic CT bone density/morphology study performed with CT imaging technology to assess bone structure and density.

Typical site of service: Outpatient imaging center, hospital radiology department, or ambulatory surgical center where CT equipment and radiology staff are available.

Clinical & Coding Specifications

Clinical Context

A 68-year-old female with progressive height loss and a history of fragility wrist fracture is referred by her primary care physician for evaluation of bone density. She reports chronic back pain and risk factors for osteoporosis including long-term corticosteroid therapy for polymyalgia rheumatica. The imaging center schedules a quantitative CT bone densitometry study to assess vertebral and hip bone mineral density and to evaluate for osteopenia or osteoporosis.

The clinical workflow: the patient arrives at the outpatient radiology clinic, screening for contraindications is completed, relevant history and medication list are confirmed, and informed consent for imaging is obtained. A CT technologist performs the bone-specific CT acquisition per protocol (calibration phantom when required) and acquires axial images of the lumbar spine and/or hips. Images are processed to generate bone mineral density measurements and T-scores/Z-scores. A radiologist interprets the study and issues a final report with measured values and comparison to prior studies if available. Results are routed to the referring clinician for management decisions.

Coding Specifications

Modifier	Description	When to Use
`26`	Professional component	Use when reporting only the physician interpretation/report for the CT bone densitometry (technical component billed separately).
`TC`	Technical component	Use when reporting only the technical component (facility/equipment) of the CT bone densitometry.
`52`	Reduced services	Use when a limited or partial CT bone study is performed due to patient factors or technical limitations.
`53`	Discontinued procedure	Use when the CT bone scan is started but terminated due to patient instability or sudden contraindication.
`59`	Distinct procedural service	Use when a CT bone densitometry is separate and distinct from another same-day imaging study at a different anatomic site.
`77`	Repeat procedure by same technologist	Use when the technologist repeats the CT acquisition due to initial technical error.
`78`	Unplanned return to the operating/procedure room by same physician following initial service	Rare for CT; use if patient requires immediate unanticipated intervention related to the procedure (very uncommon).
`80`	Assistant surgeon	Not typically used for diagnostic CT; included if procedural intervention with assistant is billed in conjunction.
`GA`	Waiver of liability statement on file (patient declined ABN)	Use when services may be denied and an ABN has been obtained and documented.
`GZ`	Unlikely to be paid—no ABN on file	Use when the service is expected to be noncovered and no ABN documented.
`Q6`	Service furnished in part by a non-physician practitioner	Use when portions of interpretation or management related to the study are furnished by a PA/NP as allowed by payer policy.
`QX`	Service performed by an assistant surgeon — documentation of noncompliance with surgical assistant rules	Rare; include only if assistant surgeon rules are relevant to a related procedure.
`59`	Distinct procedural service	See above; used to indicate separate anatomic site or distinct service when multiple imaging procedures billed same day.
`XX`	Data not available in the input	Data not available in the input.

Taxonomy Code	Specialty	Notes
`2080P0800X`	Radiology — Diagnostic Radiology	Interpreting physician for CT bone densitometry.
`2085R0206X`	Radiology — Nuclear Medicine	Some practices performing quantitative bone imaging may involve nuclear medicine overlap.
`335600000X`	Diagnostic Radiologic Technologist	Performs CT acquisition and calibration procedures.
`363L00000X`	Physician Assistant	May perform elements of patient care, scheduling, and protocoling under supervision.
`332B00000X`	Nurse Practitioner	May manage referrals and communicate results to patients.

Related Diagnoses

ICD-10 Code	Description	Clinical Relevance
`M80.08XA`	Age-related osteoporosis with current pathological fracture, vertebrae, initial encounter	CT BMD helps quantify bone loss and assess fracture-related bone quality.
`M81.0`	Age-related osteoporosis without current pathological fracture	Indication for BMD assessment to confirm diagnosis and guide therapy.
`M83.00`	Adult osteomalacia, unspecified	CT BMD can aid in evaluating bone density changes associated with osteomalacia.
`N25.81`	Renal osteodystrophy	Secondary bone disease from chronic kidney disease assessed with bone density studies.
`Z79.52`	Long term (current) use of systemic steroids	Steroid use is a risk factor for osteoporosis and is an indication for BMD assessment.

Related CPT Codes

CPT Code	Description	Relationship to This Procedure
`77078`	Computed tomography, bone density, single energy CT for bone mineral density (BMD) assessment	Primary code for quantitative CT bone densitometry to evaluate bone mass/density.
`72148`	Computed tomography, pelvis; without contrast material, followed by further sequences	Performed when pelvic/hip CT is required in conjunction with bone density assessment for hip BMD or fracture evaluation.
`72131`	Magnetic resonance imaging, lumbar spine, without contrast	Alternative or complementary modality when vertebral structural detail or marrow pathology is needed in addition to BMD.
`77080`	Dual-energy X-ray absorptiometry (DXA) bone density study, 1 or more sites, axial skeleton	Commonly performed instead of or alongside CT BMD; DXA is the standard BMD screening test.
`71110`	Radiologic examination, chest, single view, frontal	May be performed in the same patient encounter for clinical assessment when indicated (e.g., trauma assessment).