- 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
Current methods and recent advances in the diagnosis of osteoporosis.