Abstract
Errors in accuracy and precision are important problems in bone mineral density analysis.
Changes in the CT numbers caused by X-ray beam-hardening have an important effe ct on bone mineral density measurements.
X-ray beam-hard ening decreases as the effective energy of incident beam increases. We attached an additional filter (0.4mmCu) to the standard filter (3.3mmAl) to increase the effective energy of the incident X-ray beam. The effective energy increased from 43keV to 63keV. We measured the CT number of a calcium-hydroxyapatite rod (26mm Φ,100 mg/cm3) in a water phantom (body phantom) using different heights of the water phantom with the rod fixed in it, and usig different heights of the rod with the water phantom fixed. We compared the standard deviations (SDs)of the CT numbers with and without the additional filter. In conclusion, change in the CT number was suppressed from 1.7% to 1.1% with the additional Cu filter.
