A DEXA scan machine looks like a large, open padded table with a mechanical arm suspended above it. There’s no tunnel or enclosed space. The arm slowly glides over your body during the scan while you lie still on the table, and a nearby computer screen displays the results. The whole process takes about 10 to 20 minutes and is completely painless.
What the Machine Looks Like
The central DEXA machine (the standard type used in hospitals and imaging centers) has two main parts: a wide, flat table with padding, and a C-shaped or rectangular arm that hovers above it. An X-ray generator sits inside the table beneath you, and a detector is built into the arm overhead. During the scan, the arm passes slowly over the area being measured, usually your lower spine and hip. It doesn’t touch you.
Next to the table, a computer workstation runs specialized software that calculates your bone density and displays the measurements on a monitor. The technologist operates the scan from this station, often just a few feet away in the same room. The machine is quiet compared to an MRI. You may hear a faint hum or mechanical movement as the arm repositions, but there’s no banging or loud noise.
If you’ve seen an X-ray table before, a DEXA machine looks similar, just with the added overhead arm. It’s far less intimidating than a CT scanner or MRI tube.
Portable Units Look Different
Some clinics and health fairs use smaller, portable DEXA devices that only scan your wrist, heel, or finger. These look nothing like the full-sized machine. They’re compact, tabletop units where you place your hand or foot into a small opening. These peripheral scans are faster but less comprehensive. They can flag potential bone loss, but a central DEXA of the spine and hip is the standard for diagnosing osteoporosis.
What Happens During the Scan
You’ll lie face-up on the padded table in your clothes, though you may be asked to change into a gown if you’re wearing anything with metal. Zippers, underwire bras, belt buckles, and metal buttons can interfere with the image. The technologist will position your body depending on what’s being scanned. For a spine measurement, they typically place a foam block under your lower legs to flatten your spine against the table. For a hip scan, they may put your foot into a small brace that rotates your hip slightly inward.
Once you’re positioned, you just lie still. The arm moves above you in a slow, steady pass. You won’t feel anything: no vibration, no warmth, no pressure. Most people find it far more comfortable than they expected. The actual scanning time is usually under 10 minutes, though the full appointment including positioning and paperwork takes a bit longer.
Radiation Is Extremely Low
DEXA uses X-rays, but the radiation dose is remarkably small. A spine-and-hip scan delivers roughly 1 to 15 microsieverts, depending on the type of machine. For context, you absorb about 10 microsieverts from natural background radiation every single day just going about your life. A standard chest X-ray delivers 20 to 50 microsieverts, so most DEXA scans expose you to less radiation than a single chest X-ray. Newer pencil-beam scanners deliver less than 1 microsievert, making the exposure almost negligible.
What the Results Look Like
Your results come as a T-score, which compares your bone density to that of a healthy 30-year-old. The scale is straightforward:
- T-score of -1 or higher: Normal, healthy bone density.
- T-score between -1 and -2.5: Osteopenia, meaning bone density is lower than normal but not yet in the osteoporosis range.
- T-score of -2.5 or lower: Osteoporosis, indicating significant bone loss and higher fracture risk.
The report may also include a grayscale image of your spine or hip that looks like a blurry X-ray. This isn’t meant to show fine anatomical detail the way a regular X-ray would. Instead, it maps bone density across the scanned area, and the software uses that data to calculate your score. Your doctor will typically review the numbers with you and explain what they mean for your specific situation, including whether follow-up scans are needed down the road. Repeat scans are usually spaced one to two years apart to track changes over time.