Investigation on accuracy and sensitibity of three-dimensional computed tomography, and its application for simulation surgery.

本研究的目的是：1.研究3D-CT图像和颅骨复制品的准确性; 2.研究CT图像和颅骨复制品上骨缺损的原因; 3.寻找减少假阴性数据的方法; 4.评价无框架三维数据配准系统的准确性。使用此卷数据;制作0.2mm层厚颅骨模型，CT阈值为200 HU。在额眶缝水平切割颅骨，从上方拍摄眶底照片。然后用0.2mm层厚数据重建眶底三维骨表面图像，CT阈值分别为200 HU和100 HU。然后制作层厚数据，CT阈值分别为200 HU和100 HU。最后，用CT值分别为200 HU和100 HU的0.2mm层厚数据重建眶底三维骨表面图像。然后，用CT值分别为200 HU和100 HU的0.2mm层厚数据重建眶底三维骨表面图像。最后，用CT值分别为200 HU和100 HU的0.2mm层厚数据重建眶底三维骨表面图像。间隔为2.0 mm，在工作站上以0.2 mm内插图像。从这些内插切片数据，结果：1.在CT阈值为200 HU和100 HU的条件下，重建眶底三维骨表面图像，并计算出照片和三维骨表面图像中骨缺损面积占整个眶底面积的比例，并进行比较。2.假阴性骨缺损的产生主要是通过对颅骨数据的拟合和制作CAD数据的过程中产生的。3.颅骨模型具有较高的精度，最大误差为1.96 mm，最小误差为0.25 mm，平均误差为0.73 mm; 4.平均配准误差小于1个像素（=0.39 mm）。

The purpose of this research were as follows.1.Investigation of accuracy of 3D-CT image and skull replicas.2.Investigation of the cause of bone deficits on CT image and skull replicas.3.Search the way to reduce the false negative data.4.Evaluation of the accuracy of the frameless three-dimensional data registration system.Helical volume CT data of the whole head were accumulated. Using this volume data ; 0.2 mm slice data were prepared and a skull replica fabricated with a threshold CT value of 200 HU.The skull was cut at the level of the frontonaseal suture and a photograph of the orbital floors was taken from above.3D osseous surface images of the orbital floors then were reconstructed with the 0.2 mm slice data with threshold CT values of 200 HU and 100HU.Slice data then were prepared with an interval of 2.0 mm and images interpolated at 0.2 mm on the workstation. From these interpolated slice data, 3D osseous surface images of the orbital floors were reconstructed with threshold CT values of 200 HU and 100HU.The ratios of the area of bone loss to the whole orbital floors in the photograph and 3D osseous surface images were evaluated with a personal computer and then compared with each other.We could conclude by the studies as follows.1.The errors produced during the precess of thresholding and interpolation had play the main role in causing false bone deficits in the orbital floors of skull replicas.2.False negative bone deficits were created on the way from accumlating data through making CAD data. The error could be reduced by taking data with a threshold CT value of 100HU.3.Skull model have relatively high accuracy which errors are 1.96 mm maximum, 0.25 mm minimum, 0.73 mm average.4.The average registration error was liss than one pixel (=0.39 mm)