OBJECTIVETo design and manufacture a reliable spine phantom used in the cross calibration and quality control of dual X-ray absorptiometry (DXA).

METHODSA hydroxyapatite quality control phantom was designed and made through three steps: solid water, bone phantom material and integration, then evaluated the phantom on four different types of DXA machines made by LUNAR company.

RESULTSAmong the four DXA densitometers, the Expert fan beam densitometer had the biggest accuracy errors of bone mineral density (BMD), bone mineral content(BMC) and area values while the other three one narrow fan beam (Prodigy) and two pencil beam densitometers-had small errors. Of the three indexes measured by all the machines, BMD error was the smallest (-15.4%-11.5%), with the Prodigy's BMD was most outstanding. BMD errors at the higher density ends were small, tend to be positive values while the errors at the lower ends were big, tend to be negative. In cross calibration, giving consideration to the differences between the both ends, it is better to use the regression equation to correct. The base line of precision error derived by scanning the phantom once a day for consecutive 25 days was better than that derived by scanning the phantom 25 times consecutively on the same day. As to precision error, the coefficient of variation (CV) of scanning-25 times-a day was the smallest (0.0043) while the CV of 12 adults measurements was the biggest (0.0078).

CONCLUSIONSThis phantom can be used in the quality control and cross-calibration of different types of DXA machines.