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，专门用于适应全景投影架构(Ortho Tact)，在该架构中，X射线源绕患者头部旋转一条弧线。X线源和投影系统由OP-100型正位投影仪提供。它被改装成可以接受数字口腔内ccd传感器。实验包括牙周骨吸收和TMJ骨改变的诊断能力和牙周骨吸收诊断能力的评估两部分。角度差影响正畸牙槽骨的层厚，对于大于20°的层厚，层厚估计小于1 mm。因此，我们得出结论，在这些条件下，20度或更大的角差可以提供足够的深度分辨率来帮助诊断各种常见的牙病。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断层摄影。而在TMJ中，骨变化被认为描绘得很好。OrthoTACT系统的总辐射剂量与口内X线片基本相同，因此，OrthoTACT系统是一种较好的牙槽骨病变的三维摄影方法。

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.