[Methodological basis and clinical applications of total-body densitometry]

With the advent of dual-energy x-ray absorptiometry (DXA) total body scans can be done in only 10-20 minutes rather than the 60-80 minutes required by dual-photon absorptiometry (DPA). The DXA approach replace the Gd153 radionuclide source of DPA and provides substantially greater output intensity. The higher radiation flux achievable provides several advantages over conventional DPA: this makes total body scans routinely accessible. The measures of the entire skeleton and its major subregions cut down the problems of representativeness and relocation. The short term precision (coefficient of variation) was 0.5% for total body-bone mineral density (BMD) and about 1% for regional-BMD. We studied 885 women; study cohort consisted of 161 healthy postmenopausal women, 357 healthy postmenopausal women and 367 osteoporotic women with one or more vertebral crushes. The results indicate that bone mass begin decreasing during the last period of the premenopausal phase; the advent of menopause brings about a dramatic reduction of both total body and single area BMD: this phenomenon is particularly marked in subjects with osteoporosis. The single most important factor in determining BMD changes, is years since menopause. In order to assess the ability of DXA total body to distinguish women with postmenopausal osteoporosis of variable radiological degress from healthy postmenopausal women, we studied 330 postmenopausal females aged 42-85 years. There were 63 healthy women who were considered controls (Group 1).(ABSTRACT TRUNCATED AT 250 WORDS)