Allen K M, Hausmann E, Kutlubay M E, Loza J, Carpio L C, Ortman L, Wobschall D
Department of Oral Biology, State University of New York at Buffalo 14214-3008.
J Periodontal Res. 1994 May;29(3):174-8. doi: 10.1111/j.1600-0765.1994.tb01210.x.
The usefulness of subtraction radiography for detecting small changes in crestal bone is dependent upon achieving reproducible geometry between x-ray beam and patient structures when serial radiographs are taken. This study evaluates 2 methods currently employed to maintain geometric correspondence: 1) a stent-based system which rigidly fixes a custom-made stent to the x-ray tube by the use of a rod and 2) an extra-oral system which positions a patient in the x-ray unit by means of ear rods. The projection of a light beam from a fixed subject reference was used to measure the change of the orientation of the reference at 2 different measurement times. The rod-stent system was able to maintain a discrepancy of less than 2 degrees 75% of the time over a time period of 6 months. For the extra-oral system this ranged from 72% to 92% during a 1-month period.
减影放射摄影术用于检测牙槽嵴骨微小变化的有效性取决于在拍摄系列X光片时，X光束与患者结构之间能否实现可重复的几何关系。本研究评估了目前用于维持几何对应关系的两种方法：1）基于支架的系统，该系统通过使用杆将定制的支架牢固地固定在X光管上；2）口外系统，该系统通过耳杆将患者定位在X光设备中。利用来自固定的受试者参考物的光束投影，在两个不同的测量时间测量参考物方向的变化。在6个月的时间段内，杆式支架系统有75%的时间能够将差异维持在2度以内。对于口外系统，在1个月的时间段内，这一比例在72%至92%之间。
