Bone Density Measurement Using Computed Tomography

Osteoporosis is a major medical, social, and economic problem. Osteoporosis and low bone mass affect an estimated 44 million Americans (National Osteoporosis Foundation, 2008). The lifetime risk of hip, spine, or forearm fractures is estimated to be 40% in white women and 13% in white men above 50 years of age. Considerable attention is therefore focused on assessing bone mass and the ability to identify people at risk of fracture. Determining bone density (BD) helps a doctor determine those at increased risk for osteoporosis-related fracture. Bone density (or bone mineral density) is a medical term that refers to the amount of matter per square centimeter of bone. Bone density is used in clinical medicine as an indirect indicator of osteoporosis and fracture risk. BD measurements are most commonly made over the lumbar spine and over the upper part of the hip. In recent literature, several approaches have been introduced to measure mandibular and skeletal BD, and then compare these measurements with BD in other parts of the skeleton. The measurement is painless, non-invasive, and involves minimal radiation exposure. In this chapter, bone density using computed the tomography technique will be introduced and discussed. CT is an imaging technique that shows human anatomy in cross sections and provides a three-dimensional dataset that can be used for image reconstruction and analysis in several planes or three-dimensional settings. CT is used to study bone pathology, from traumatic lesions to bone neoplasm. In addition to morphologic information, CT also provides information about tissue attenuation. Direct Hounsfield unit measurements for BD may be used to examine bone quality. Attenuation values can be extracted from raw CT data and used to reconstruct images. These values can also be used to estimate the density of tissues. CT accurately measures bone density. CT density measurement methods can be used as to separate the trabecular bone from the cortical shell and the posterior elements of vertebrae. CT density measurements have shown superiority to other modalities Using CT for take density measurements is discussed, including several of its challenges, in the current clinic. The foundations of CT density, classification, and registration are discussed in detail.