The Study Of Accuracy Of Volumetric Quantitative Computed Tomography In Measuring Bone Mineral Density Of The Proximal Femur

ObjectiveTo compare the data of volumetric quantitative computed tomography(vQCT) and of dual energy radiograph absorptiometry (DXA) with of bone ash analysis respectively in measuring bone mineral density of the proximal femur, to determine and compare the correlation, and then to guide the diagnosis and treatment of osteoporosis.Summary of background dataOsteoporosis is a systemic skeletal disease characterized by low bone mass and microarchitecrural deterioration of bone tissue, with a consequent increase in bone fragility and susceptibility to fracture, and it has been a severe disease can influence human's healthy. Nowadays, the important index to diagnose osteoporosis is to measure the bone mineral density. Among bone mineral densitometry techniques, dual energy radiograph absorptiometry (DXA) and conventional quantitative computed tomogra-phy(QCT) are used widespreadly and accuracily. But it is not very clearly that which technique is more accuracy and better. Beacouse of the complicated architecture, the triaxiality bone mineral density of proximal femur is very different interiorly, volumetric quantitative computed tomography(vQCT) has been used to measure the bone mineral densith of the proximal femur, but we should study the accuracy further in order to guide the clinical application more accurately and safely.Methods10 specimens of cadaveric hip (male 4, female 6) were recruited. Bone mineral density(BMD, g/cm~2) and bone mineral content(BMC,g) was measured anteroposterior by DXA around the midpoint of the neck of femur. 64-slice spiral CT scanned the specimens from the head to trochanter of femur and the standard phantom meanwhile. The OsteoCAD software analysis the pictorial date automatic from CT, ane divide images automatic from proximal femur to acetabulum to get the BMD(g/cm~3) and the BMC(g) of proximal femur and neck of femur. 20 specimens of proximal femur were dissected from the hip. After adjunctive soft tissue removed by boil completely, the specimens were divided into head, neck and trochanter of femur manual, and then we dried the specimens and measured the volume by extractio. By incinerated them in muffle furnace and weighed the ash we got the weight. According to densith means weight divide volume, the ash density have gained(g/cm~3).ResultsAfter compared the value of BMD and BMC of neck of fumer measured by DXA and vQCT respectively with the value of bone ash density of incinerated proximal femur, we calculated the correlation between the BMD measured by vQCT and bone ash density and between BMD measured by DXA and bone ash density and calculated the correlation between the BMC measured by vQCT and bone ash density and between BMC measured by DXA and bone ash density. The BMD of neck measured by vQCT, DXA and bone ash density were 0.2126±0.0840 g/cm~3, 1.0788±0.1760 g/cm~2, 0.5175±0.0821g/cm~3. The BMC of neck measured by vQCT, DXA and bone ash weight were 5.1294±1.5800g, 5.0949±1.2629g, 6.8906±1.2173g. The correlation of BMD measured by vQCT and the bone ash density was high(r=0.852, P=0.001), The correlation of BMD measured by DXA and the bone ash density was low relatively(r=0.807, P=0.001). The correlation of BMC measured by vQCT and the bone ash weight was (r=0.882,P=0.002), The correlation of BMC measured by DXA and the bone ash weight was high too(r=0.854, P=0.002), but was low relatively than the correlation of BMC measured by vQCT and the bone ash weight.Conclusion vQCT is a three-dimensional quantitative technique that close to the ture meaning of the BMD volumetrically and that permits separate characterization of bone geometry and bone density as elements of fracture risk. This volumetric measurement removes the confounding influences of bone size and shape. Beacouse of the complicated archi-tectureand the triaxiality bone mineral density of proximal femur is very different interiorly, the significance of measuring the BMD by conventional QCT is low. The linear correlation of BMD measured by vQCT and bone ash density is higher than that by DXA and the linear correlation of BMC measured by vQCT and bone ash weight is higher than that by DXA. In conclusion, we found that the measurement of BMD by vQCT is reliable and valuable for diagnosing of osteoporosis, predicting of fragile fracture, evaluating and guiding of operative treatment.