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Dual X-ray Absorptiometry

- Discussion:

    - is the newest and the most precise technique for evaluating osteoporosis, and has emerged as the successor to DPA;
- anatomic sites for DXA measurement include:
- lumbar spine, proximal femur, forearm and calcaneus;
- advantages of an x-ray system over a DPA radionuclide system include:
- shortened examination time (2 min);
- greater accuracy and precision due to higher resolution
- lowest radiation of the available techniques and lack of radionuclide decay (1/10th radiation dose of a CXR);
- can distinguish between regions w/ distinct compositions of trabecular and cortical bone (eg the femoral neck and Ward's triangle);
- disadvantages: gives an area measurement study versus a volumetric study;
- T-scores:
- bone-mineral-density values are expressed in terms of "T-scores"
- these indicate the number of standard deviations by which the patient's bone-mineral density differs from a normal mean value;
- osteopenia is defined as a T-score of between -1 and -2.5
- osteoporosis is defined as a T-score of below -2.5

Noninvasive Measurements of Bone Mass, Structure, and Strength: Current Methods and Experimental Techniques.

Bone density at various sites for prediction of hip fractures. The Study of Osteoporotic Fractures Research Group.

Current methods and recent advances in the diagnosis of osteoporosis.