Todd A D, Gher M E, Quintero G, Richardson A C
Periodontics Department, Naval Dental School, National Naval Dental Center, Bethesda, MD.
J Periodontol. 1993 Dec;64(12):1243-9. doi: 10.1902/jop.1993.64.12.1243.
Tomography is a radiographic process that produces cross-sectional images of bony structures within the body. The purpose of this study was to evaluate the accuracy of diagnostic measurements made by dental implant team members from linear tomograms of human cadaver mandibles. Five partially edentulous cadaver mandibles were radiographed using linear tomography (LT) and computer-assisted tomography (CT). From the tomograms, each of four team members traced the perceived outer circumference of the mandible and the inferior alveolar canal. Tomogram tracings were compared to each other and to the equivalent CT cross-sectional image to determine the precision of the measurements. One mandible was sectioned to verify the accuracy of the CT images. Repeated measures analysis of variance of the measurements made from the LT and CT scans showed significant statistical differences between team members. Multiple cross-sectional views facilitated identification of the inferior alveolar canal in the majority of CT scans, whereas image blurring inherent to LT resulted in the inability of team members to identify the canal in 14% to 50% of the images. Volume averaging within the CT slice aperture was found capable of producing a magnification error of short dense objects. CT and LT must both be interpreted cautiously because of innate technique objects. CT and LT must both be interpreted cautiously because of innate technique pecularities that can lead to measurement errors. The wide variation in interpretation of the linear tomograms and frequent inability to identify the inferior alveolar canal made this technique less valuable than the reformatted CT when planning dental surgical procedures.
断层摄影术是一种放射成像过程，可生成体内骨结构的横断面图像。本研究的目的是评估牙科种植团队成员根据人类尸体下颌骨的线性断层照片进行诊断测量的准确性。使用线性断层摄影术（LT）和计算机辅助断层摄影术（CT）对五具部分牙列缺失的尸体下颌骨进行了放射成像。从断层照片中，四名团队成员分别描绘出下颌骨和下牙槽管的可见外周。将断层照片的描绘结果相互比较，并与等效的CT横断面图像进行比较，以确定测量的精度。对其中一具下颌骨进行切片以验证CT图像的准确性。对LT和CT扫描测量结果进行的重复测量方差分析显示，团队成员之间存在显著的统计学差异。多个横断面视图有助于在大多数CT扫描中识别下牙槽管，而LT固有的图像模糊导致团队成员在14%至50%的图像中无法识别该管。发现CT切片孔径内的体积平均会对短而致密的物体产生放大误差。由于固有的技术特点可能导致测量误差，CT和LT都必须谨慎解读。在线性断层照片的解读中存在很大差异，并且经常无法识别下牙槽管，这使得该技术在规划牙科手术时不如重新格式化的CT有价值。
