Bone densitometry (DXA)

Dual energy x ray absorptiometry (DXA) is the technique most commonly used to determine the amount of calcium in the lower spine and hips.  Low energy x rays are used to determine the difference between beam absorption by bone versus surrounding soft tissues, like muscle.  Bone tissues absorb the beam of x rays while the x rays pass through the soft tissues.  The difference in absorption corresponds to the amount of calcium in the spine and thigh bones.  The test is done while lying flat on your back on a table.  The arm of the machine passes over you for about fifteen minutes.  Other bone density measuring techniques use the heel as the measuring location.  The machine is portable so it is more accessible.  Unfortunately it is less accurate than the DXA of the hips and spine.

Dual Energy X-Ray Absorptiometry (DEXA) Scanning

What is a DEXA?

DEXA scan uses two sources of x-ray energy to separate soft and bone tissue components of bone and surrounding tissues.  DEXA is used to measure the bone mineral density of the lumbar spine and long bones.  A phantom of a constant density is used to calibrate the machine.  The precision of DEXA for bone mineral density of the vertebral spine is 1%, with accuracy variability of 4% to 8%.

How is a DEXA taken?

The test is done while lying flat on your back on a table.  The arm of the machine passes over you for about fifteen minutes.  Other bone density measuring techniques use the heel as the measuring location.  The machine is portable so it is more accessible.  Unfortunately it is less accurate than the DXA of the hips and spine.

CONDITIONS OF THE GI TRACT