ESTABLISHMENT OF MEASUREMENTS METHOD FOR COMPACT BONE MINERAL DENSITY BY HELICAL SCAN CT WITH HA-C REFERENCE

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The main purpose of this prefect, i.e. establishment of measurements method for compact bone mineral density by helical scan CT with HA-C reference were completed. The features of this new reference were as furrows ; (1) The materials of new reference is consist of hydroxyapatite and pure carbon. (2) The CT number of 100% references have higher than compact bone. (3) The accuracy were verified by the examination using human cadavers.The new columnar shape references, 3.4 - 5.7 mm in height and 1 3.05 + 0.10 m diameter, consists of two materials : hydroxyapatite (HA) which was prepared in our laboratory according to the Shimoda (1990) method, and 99.9% carbon(C) : (Soekawa Chemicals Tokyo). After using an agate mortar and pestle to make a mixture of fine granules of hydroxyapatite and carbon powder using at the exact weight ratios of 100, 80, 60, 40, 20%, each mixed sample was pressed using a metal mold and presser (shimazu, at 600kg/cm2) equipped with a vacuum pump. These five step HA- … More C pellets were used as a CT standard after measuring their accurate weight and volume. The unit of references, therefore, represented HA weight (mg) per unit volume (mm) according to the hydroxyapatite contents of each pellet. The spiral CT images were taken as a test measurement of CT value using a human cadaver equipped with the references at the menton region of mandible. The CT images were taken under the following conditions : slice thickness 1 mm table forward speed, 1mm/sec : X-ray tube voltage, 120kV tube current ranges between 75 - 175mA. The CT values of the references were in a range between 2583.1±25.28〜351.91±17.66, and the CT value to HA mg/mm of each reference showed positive linear regression (r= 0.9996). The maximum CT value of the compact bone in the mandible was 1665.9±198.43, and the conversion value in HA weights per unit volume was 1.393mg/mm3. After the test measurements of the CT value of the new references in regard to human com-pact bone the validity of the references was examined by biopsy using human cadaver.The clinical test measuring of BMD in age twenties to sixties woman showed that the maximum BMD values of compact bone in human mandible were seen at thirties and then decreased with ageing. It is considered that more extensive studies should be done quickly. Less