Fundamental Study of Three Dimensional Fine Structure Analysis of Jaw Bone

同一标本在不同条件下进行CT扫描时，同一标本的CT值不能与小视场CT(专为牙科设计的CT)的值相同。这种现象在很大程度上取决于标本的外形和大小，即使受试者被覆盖在有限的视野内也会发生这种现象。牙科CT值的不稳定性是由于视野有限造成的所谓投影数据不完整造成的。然而，这种解释可能是不正确的，因为即使对象大小足够小，在我们的结果中可以覆盖在视野内，CT值也会发生不稳定。此外，一些特殊的观察图像处理方法，如切片求和法，提高了图像质量，但失去了视轴的特殊分辨率。通过使用全身CT和为牙科设计的CT，获得了均匀的铝+铜(5%)合金锥体(CT值超过3000HU上限)。都进行了测量。非联合国组织的…牙科用CT值更多地反映了牙科用CT像素密度的非线性特征。这一点也证明了牙科用CT与数字层析成像非常接近。从全身用MD-CT与牙科用CT相比，牙科用CT在空间分辨率的可视测试中并不是特别好。但由于牙科CT的非线性，没有考虑MTF的影响，设计了小型HA模体，可以无干扰地测量小孔和线条，大小为300μm的小孔，MD-CT不能检出，而牙科CT能检出。小视场CT(专为牙科设计的CT)用像素值分析牙体的三维结构似乎并不容易。我们的研究结果表明，在内容物上类似于骨骼的小型CT体模的重要性。较少

CT values of the same bone specimen can not be measured as the same value at small field of view CT (CT designed for the dentistry) scans in different conditions. This phenomenon depended on the contour and size of the specimen greatly, and occured even if subjects were covered within limited view. The un-stability of the CT value at the CT designed for the dentistry was believed to happened by so-called the imcomplete projection data that caused by limited views. However, this explanation may not be true, because the un-stability of the CT value occurs even if objects size were enough small that could be covered within the field of views in our result. Also some special viewing image processing like slices sum methods improve the image quality like S/N but loose the special resolution for view-axis.By using both the whole body CT and CT designed for the dentistry, an uniform aluminum + copper (5%) alloy cone (CT value beyond the upper limit of 3000H.U.) were measured. The the non-unif … More orm CT values at CT designed for the dentistry indicated the non-linear characters of the pixel density of the CT.Also it was proved that CT designed for the dentistry was very close to Digital-Tomography with this point.The CT designed for the dentistry was not especially excellent in visible test of spaceal resolution using W-wires at the comparison between MD-CT for the whole body and CT designed for the dentistry, though it wasn't clear because MTF wasn't being taken into consideration because of the non-linear character of the CT designed for the dentistry.Small HA phantoms were designed so that small hole and line can be measured without aritifacts.Holes with the size of 300μm could not be detected by MD-CT, while it could be detected by the CT designed for the dentistry. The predominance of the CT for the dentistry for the endodontics was shown in the point.It seemed to be not easy to analyze the three dimensional structure by small field of view CT (CT designed for the dentistry) using pixel value like CT. The result of our study show the importance of small CT phantom that similar to bone at contents. Less