DXA Bone Density Screening

Dual-energy X-ray absorptiometry of lumbar spine + proximal femur (and sometimes forearm) — standard screening for osteoporosis in postmenopausal women, men over 70, and patients on chronic steroids or with secondary risk factors. Extremely low radiation dose (~1 µSv per site). Results reported as T-score and Z-score referenced to the manufacturer's normative database; FRAX 10-year fracture risk computed from BMD + clinical risk factors.

Clinical pathway

1. Patient positioning — supine on table, feet in positioner for hip scan.
2. Lumbar spine AP scan — L1–L4; exclude fractured or osteophytic vertebrae from analysis.
3. Proximal femur scan — femoral neck, total hip.
4. Optional VFA (vertebral fracture assessment) — lateral T4–L4 to detect morphometric fractures.
5. Reporting — lowest T-score determines diagnosis; ISCD guidelines for serial comparison.

Typical systems

• Hologic Horizon family (A / W / Wi / Ci tiers)
• GE Lunar iDXA
• GE Lunar Prodigy (large refurb base)
• Norland (legacy installed base)

Hologic and GE Lunar normative databases are not cross-comparable — serial scans must be on the same manufacturer's system, and ideally the same unit, for meaningful comparison.

Room + procedure characteristics

• Scan time: 5–10 min total including positioning.
• Dose: <10 µSv per scan (less than a day of natural background).
• Team: DXA-trained tech, interpretation by radiologist or endocrinologist.

Equipment considerations that bite

• Manufacturer lock-in. Choosing Hologic vs GE Lunar is a multi-decade decision because patient serial-scan continuity depends on the platform. A site that switches vendors creates a discontinuity in every patient's longitudinal record.
• Software version + ISCD calibration — the normative database update is software-driven; running on outdated software causes T-score drift on the same hardware. Refurb deals should explicitly include current software.
• Phantom QC discipline — daily spine phantom scan tracks long-term BMD precision. Drift outside ISCD thresholds requires recalibration; missed QC days don't count for billing in many jurisdictions.
• VFA + body composition options — VFA is a separate license tier on most platforms; whole-body composition (DXA body comp) adds another. Refurb buyers commonly find these absent from the configuration they bought.
• Detector / source aging — DXA sources are long-lived but not infinite; precision degrades silently before failure. Annual physicist survey catches it.

Operational reality

• Throughput is patient flow, not scan time. A unit can do 20+ patients per day; the bottleneck is room scheduling and tech coverage.
• Reimbursement is tight — DXA codes are low-margin per-study; volume + adjacent endocrine / rheumatology referrals are how programs justify the install. Mobile DXA fleets exist on this economics.
• MQSA-style accreditation — ISCD facility certification is the de-facto QA framework for DXA; accreditation lapses interrupt billing.
• Refurb economics — DXA fleets age gracefully; installed bases of 10+ year-old Lunar Prodigy and Hologic Discovery / Horizon units are the entry-tier market. Software / workstation refresh is the high-yield refurb upgrade.

Related

• Screening Mammography (sibling preventive imaging)
• Hologic Horizon Field Guide
• Hologic Horizon family
• GE Lunar iDXA