LATERAL SPINE DUAL-ENERGY X-RAY ABSORPTIOMETRY - BONE-MINERAL MEASUREMENT WITH FAN-BEAM DESIGN - EFFECT OF OSTEOPHYTIC CALCIFICATIONS ON LATERAL AND ANTEROPOSTERIOR SPINE BMD

Recently, fan beam (FB) designs have been made available by several ma nufacturers (Aloka, Hologic Lunar and Sophar) to measure lumbar spine bone mineral area density (BMD) in both an anteroposterior (AP) and a lateral projection. The present study was performed to evaluate some c haracteristics of a new dual energy X-ray absorptiometry (DXA) system for supine lateral scans in normals and to study possible advantages f or patients with osteophytic calcifications (OC). The precision errors of in vitro and in vivo measurements were estimated by an anthropomor phic phantom and in healthy volunteers. To study the effect of osteoar thritic changes on AP and lateral DXA measurements, BMC (bone mineral content) and BMD were measured in age-matched women (n=150) with and w ithout OC. Precision errors for lateral BMD in vitro over 1 and 6 mont hs were 0.58/0.67% (slow/fast scan modes) and 0.67/0.77% (slow/fast sc an modes), respectively. The short- and mid-term reproducibility of BM D values were 2% and 3.5%, respectively, using the compare function (3 .5% and 7.5%, respectively, without the compare facility). The analysi s of women with and without OC (n=150) demonstrated higher mean values for AP BMD (0.892+/-0.145 g/cm(2)) in patients with OC (n=75) than in normals (0.836+/-0.135 g/cm(2), n=75, difference 6.3%). For lateral s cans, BMD differed to a minor degree (3.1%) in patients with OC (0.629 +/-0.133 g/cm(2)) compared with normals (0.610+/-0.117 g/cm(2)). Corre sponding results were obtained in fast FB mode. Furthermore, we found significant (P<0.0001) correlations between BMD in lateral and AP scan s in patients without OC (r=0.63) and in patients with OC (r=0.57). Al though the FB design facilitated fast AP and lateral scans, the higher precision errors of lateral scans could limit its application in long itudinal studies. The use of compare function should be recommended. H owever, BMD of lateral scans was less influenced by OC.