Development of 3D radiography for tooth and its supported structures

调谐孔径计算机断层扫描（TACT）是一种新的三维射线成像方法。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），其中x射线源在患者头部周围以单弧旋转。x射线源和投影系统由一台OP-100正形解剖仪提供。它被修改为接受一个数字口内CCD传感器。我们研究了牙槽病变诊断的条件和准确性。实验分为两部分：评估牙周骨吸收和颞下颌关节（TMJ）骨变化的切片厚度和诊断能力。角度视差影响了Ortho TACT的切片厚度。对于差异大于20度，切片厚度估计小于1毫米。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能提供足够的深度分辨率，以促进各种常见牙齿疾病的诊断。在诊断牙周骨吸收的情况下，OrthoTACT系统比传统的口腔内双切面放射检查有更好的表现。而在TMJ中，骨变化被认为是描述良好质量的。OrthoTACT系统的总辐射剂量与口腔内放射照相几乎相同。综上所述，OrthoTACT系统是牙槽区牙槽区病变较好的三维影像学检查方法。

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.