Patient Care and Education
Before the scan
Ask about pregnancy, recent contrast or nuclear medicine studies, and metal in the region of interest. DXA is very low dose (roughly 1–10 µSv, comparable to a few days of background radiation); pregnancy is not an absolute contraindication, but scan only when justified. Barium or iodine contrast can falsely alter spine BMD, so schedule DXA before contrast or delay it (commonly about 7 days, per facility policy). Most Tc-99m studies clear within 24 hours; radioiodine may interfere longer. Patients typically avoid calcium supplements for 24 hours and remove zippers, buttons, coins, and underwire garments.
During the scan
Measure height and weight, and record arm span when height is unreliable (kyphosis, inability to stand). Explain that the table is open, the scan is painless, and the patient must remain still. Position the patient supine and midline, using aids such as a foam block under the knees for the spine and a foot device for hip rotation. Know the table weight limit and alternative sites for patients who exceed it.
Traps
Assuming DXA is contraindicated in pregnancy, scanning over metal without documenting it, accepting self-reported height, and failing to ask about recent contrast.
Rule of thumb: if a patient had a barium study yesterday, treat the spine result as invalid and reschedule rather than reporting a value you cannot trust.