Bone mineral content and quantitative computerized tomography

Many methods are used to determine bone mineral content (BMC). Quantitative computed tomography (QCT) appears to be the most reliable method also because it allows the trabecular and the cortical bone to be measured separately. QCT is usually performed on the first four lumbar vertebral bodies. BMC is expressed in mg/ml and a mean value is calculated. Three hundred and fifteen subjects were studied (281 women and 34 men). The patients affected with Paget's disease or malignancies, with or without bone metastases, were not included in this study. The measurements were performed by means of a General Electric 9800 tomograph with software and calibration phantom (QCT-Bone program by Image Analysis). Fractured vertebrae were not included when calculating the mean value since an increased density is caused by fracture. The BMC of any studied vertebral body is considered in comparison with the BMC of the other lumbar vertebrae of the same subject. When the BMC of a given vertebral body exceeds the others by 25 mg/ml or more, nodules and/or stripes are observed during multiple-slice scanning of the bone. Lytic areas or angiomas are observed when the BMC of a given vertebral body is -25 mg/ml or higher. In calculating the mean vertebral BMC, vertebrae with both +25 and -25 must be excluded. In this way the method reliability increases.