Fundamental Study of Three Dimensional Fine Structure Analysis of Jaw Bone

同一骨标本在不同条件下进行小视野CT扫描时，其CT值不可能相同。这一现象与标本的外形和大小有很大关系，即使在有限视野范围内也会发生。牙科CT值的不稳定性被认为是由于有限的视野所导致的所谓的不完整投影数据。然而，这种解释可能是不正确的，因为即使物体尺寸足够小，可以在我们的结果中的视野内覆盖，CT值的不稳定性也会发生。采用全身CT和牙科专用CT扫描，获得了均匀的铝铜（5%）合金锥（CT值超过3000 H. U.）测定了非unif 关于我们 牙科专用CT的CT值显示了CT像素密度的非线性特征，证明了牙科专用CT在这一点上与数字断层扫描（Digital-Tomography）非常接近，但在全身MD-CT与牙科专用CT的比较中，牙科专用CT在W丝空间分辨力的可见性测试中并不是特别优秀，由于牙科CT的非线性特性，MTF没有被考虑在内，所以目前尚不清楚，我们设计了小型HA模型，可以无伪影地测量小孔和线，MD-CT不能检测到300μm的小孔，而牙科CT可以检测到。牙科CT在牙髓病学中的优势体现在这一点上，小视野CT（CT designed for the dentistry，牙科专用CT）利用CT的像素值分析三维结构似乎并不容易。本研究结果显示了在内容上与骨骼相似的小型CT体模的重要性。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