Development of 3D radiography for tooth and its supported structures

调谐孔径CT（TACT）是一种新的三维成像方法。我们现在正在开发一种TACT系统，该系统特别适合于适应全景投影架构（Ortho TACT），其中X射线源围绕患者头部以单个弧旋转。X射线源和投影系统由Orthopantomograph OP-100提供。它被修改为接受一个数字口内CCD传感器。本研究探讨了OrthoTACT诊断牙槽骨病变的条件和准确性，实验分为层厚评价和对牙周骨吸收和颞下颌关节（TMJ）骨质改变的诊断能力两部分，角度差异影响OrthoTACT的层厚，当角度差异大于20 °时，切片厚度估计小于1 mm。因此，我们得出结论，在这些条件下，20度或更大的角度差异可以提供足够的深度分辨率，以便于诊断各种常见的牙科疾病。在诊断牙周骨吸收的情况下，OrthoTACT系统的性能优于传统的口内双切片X线摄影。颞下颌关节骨改变被认为是描述良好的质量。OrthoTACT系统的总辐射剂量与口内X线片的总辐射剂量基本相同，是一种较好的牙槽骨病变三维X线摄影方法。

Tuned-aperture computed tomography (TACT) is a new three dimentional radiographic method. We now are developing a TACT system adapted specifically to accommodate a panoramic projection architecture (Ortho TACT) wherein the x-ray source rotates in a single arc around the patient's head. The x-ray source and projection system were provided by an Orthopantomograph, OP-100. It was modified to accept a digital intra-oral CCD sensor. We studied its conditions which required for and accuracy for diagnosing dent-alveolar lesions.The experiments were consisted of two parts those were evaluation of slice thickness and diagnosing ability for periodontal bone resorption and temporomandibular joint (TMJ) bone changes.The angular disparity influenced slice thickness of Ortho TACT.For disparities greater than 20 degrees, slice thickness was estimated to be less than 1 mm. We therefore conclude that under these conditions angular disparities of 20 degrees or more may provide enough depth resolution to facilitate diagnosis of a large variety of common dental disorders.In case of diagnosis for periodontal bone resorption, OrthoTACT system is better performance than conventional intraoral bi-secting radiography. And in TMJ bone changes is considered to be depicted good quality. Total radiation dose for OrthoTACT system are almost same as that for intraoral radiography.In conclusion, OrthoTACT system is better three-dimensional radiographic methods for dent-alveolar lesions.