DEXA Scan - Dual Energy X-Ray Absorptiometry/Densitometry

DEXA stands for Dual Energy X-Ray Absorptiometry (or Densitometry). A DEXA scan is a procedure that measures the amount of bone, muscle and/or body fat.

The DEXA determination of bone density or body composition (muscle and fat composition) is performed with an instrument that uses low energy x-rays. (Read about "X-rays") For bone density measurements, scans are typically performed of the lumbar (lower) spine, the hip and the wrist. (Read about "The Spine" "The Hip") This is a common procedure for the diagnosis of osteoporosis (Read about "Osteoporosis") and other bone diseases. (Read about "Skeletal System") For body composition measurements, a scan of the entire body is performed.

The DEXA instrument is very open consisting of a table and scanning arm (in the shape of a "C") that houses the x-ray tube on one end of the arm and the detector on the other end.

There is no specific preparation for a DEXA scan. There are limitations however.

• DEXA studies cannot be performed if the patient has had a nuclear medicine study within 1 week, or an x-ray procedure using contrast within 72 hours. Procedures such as CT and PET scans are examples of procedures that use contrast and nuclear material. (Read about "Nuclear Medicine" "CT Scan - Computerized Tomography" "PET - Positron Emission Tomography")
• Women who are of childbearing age must have pregnancy ruled out before undergoing the test. Often this means having a pregnancy test performed within 1 week of the DEXA procedure. (Read about such dangers in "Healthy Pregnancy")

The patient should wear light clothing. They may be asked to change into a surgical scrub uniform or other garments for the study.

After changing, the patient will have their weight and height measured. For these measurements and scans, patients usually remove their shoes. The individual scanning procedures are performed with the patient either lying on top of or sitting next to the scanning table.

The length of time in the facility will depend on the number of procedures that are performed. Usually the appointment is for either 1/2 hour or 1 hour.

For each scan, the technologist must perform two steps. First, they must perform the scan; second, they must analyze the scan to determine the information contained within the scan. The DEXA scans are therefore more complicated than standard x-rays.

After the technologist has completed and satisfactorily analyzed the scans, the patient can then change back into their street clothes and leave.

A physician reviews the scans to determine the patient's risk for osteoporosis and bone fractures. (Read about "Bone Fractures") A report of the DEXA scan results will be entered into computer and record systems and forwarded to your healthcare provider.