ABSTRACT
Computed tomography (CT) scanners image the distribution of linear attenuation coefficents in a thin axial slice of tissue. CT is a highly useful modality for bone imaging because its high attenuation coefficient allows for excellent contrast from the surrounding soft tissue. Quantitative computed tomography (QCT) is a long-standing method for measuring bone mineral density (BMD) in the metabolically-active trabecular bone in the vertebral bodies. CT BMD assessment is based on quantitative analysis of the Hounsfield unit in volumes of bone tissue. Typically, the BMD is quantified using a bone mineral reference phantom which is scanned simultaneously with the patient. The major source of error in the QCT bone measurement is the phenomenon of partial volume averaging. The primary advantage of volumetric QCT of the spine is improved reliability in measurement of trabecular BMD. The two principal QCT manufacturers in the United States are Image Analysis and Mindways.
