[Value and limitations of the computed x-ray tomographic measurement of vertebral mineralization]

An experimental study of the reproducibility and exactitude of densitometric measurements obtained by CT scanning showed: 1) the existence of marked variations due to factors related to the apparatus: beam energy, filtration, electronics, direction of rotation, reconstruction software; 2) that the structure of the object was also an influencing factor: variations in tissues surrounding the vertebra, and variations in bone density as a function of the plane in the vertebral body, and in fat content in the spongy tissue. Any measurement by CT scan of the mineral density of the vertebral body requires the use of a calibration phantom, strict definition of the volume to be measured, and routine correction for hypodensity induced by fat when necessary. Results under these conditions are reproducible and useful for the diagnosis of rarefying osteopathies.