Image Acquisition and Analysis
Positioning
Spine: supine, centered on the table, knees flexed over a foam block to flatten lumbar lordosis; scan approximately T12–L5. Hip: supine with the foot secured in the positioning device and the leg in 15–25° internal rotation so the femoral neck lies parallel to the table; include the ischium. Forearm: nondominant arm unless it is fractured or has hardware; the 33% radius is the standard site.
Analysis
Check centering, motion, and artifact before drawing intervertebral lines. Exclude vertebrae that are fractured, severely degenerated, laminectomized, augmented with cement, or covered by metal. ISCD requires at least two evaluable vertebrae for a spine result. Diagnosis uses the lowest T-score among valid sites: lumbar spine, total hip, femoral neck, or 33% radius. Do not use Ward's area or the greater trochanter for diagnosis.
Traps
Including a fractured vertebra; comparing T-scores over time instead of g/cm²; monitoring at a different site; and neglecting internal rotation, which shortens the projected femoral neck and changes BMD.
Worked example: L1–L4 are scanned and L3 shows a compression fracture. Exclude L3, report the mean of L1, L2, and L4, and note the excluded level in the report.