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A scanner used to measure bone density using dual energy X-ray absorptiometry. Bone density, or bone mineral density, is the amount of bone mineral in bone tissue.The concept is of mass of mineral per volume of bone (relating to density in the physics sense), although clinically it is measured by proxy according to optical density per square centimetre of bone surface upon imaging. [1]
DXA is only able to provide the areal bone mineral density. High-resolution peripheral quantitative computed tomography (HR-pQCT) is better than DXA at detecting bone microarchitecture, modeling whole-bone geometry using 3-dimensional information from scans. This method allows estimation of bone strength and other mechanical properties. [20]
Bone densities are often given to patients as a T score or a Z score. A T score tells the patient what their bone mineral density is in comparison to a young adult of the same gender with peak bone mineral density. A normal T score is -1.0 and above, low bone density is between -1.0 and -2.5, and osteoporosis is -2.5 and lower.
The trabecular bone score is a measure of bone texture correlated with bone microarchitecture and a marker for the risk of osteoporosis. Introduced in 2008, [ 1 ] its main projected use is alongside measures of bone density in better predicting fracture risk in people with metabolic bone problems.
In another study, osteoporosis in human cancellous bone led to 3-27% variability in the stiffness and strength compared to health bone. [97] Additionally, bone mineral density (BMD) is a parameter used to evaluate fracture risk in bones and is used as a predictor of osteoporosis. [92]
Information from the DXA scanner creates a bone mineral density T-score by comparing a patient's density to the bone density of a healthy young person. Bone density between 1 and 2.5 standard deviations below the reference, or a T-score between −1.0 and −2.5, indicates osteopenia (a T-score smaller than or equal to −2.5 indicates ...
In educational assessment, T-score is a standard score Z shifted and scaled to have a mean of 50 and a standard deviation of 10. [14] [15] [16] In bone density measurements, the T-score is the standard score of the measurement compared to the population of healthy 30-year-old adults, and has the usual mean of 0 and standard deviation of 1. [17]
Z-test tests the mean of a distribution. For each significance level in the confidence interval, the Z-test has a single critical value (for example, 1.96 for 5% two tailed) which makes it more convenient than the Student's t-test whose critical values are defined by the sample size (through the corresponding degrees of freedom). Both the Z ...