Department of Oral Diagnosis, Division of Oral Radiology, Piracicaba Dental School, University of Campinas (UNICAMP), Sao Paulo, Brazil.
Department of Imaging & Pathology, Faculty of Medicine, KU Leuven and Oral and Maxillofacial Surgery, University Hospitals Leuven, Leuven, Belgium.
Dentomaxillofac Radiol. 2020 Jul;49(5):20190385. doi: 10.1259/dmfr.20190385. Epub 2020 Mar 16.
To create a new phantom design to evaluate the real impact of artefacts caused by titanium on bone structures in cone beam CT images considering different positions and quantity of metals in the dental arch, with and without metal artefact reduction (MAR).
A three cylindrical polymethyl methacrylate (PMMA) plate phantom was designed containing eight perforations arranged to simulate the lower dental arch in the intermediate plate. Three titanium cylinders were positioned in different locations and quantities to test different clinical conditions and to quantify the impact of the metal artefact around five bone cylinders. Scans were carried out in seven different protocols (Control, A-F) in two cone beam CT devices (OP300 Maxio and Picasso Trio). Eight regions of interest around each cortical and trabecular bone were used to measure the grey value standard deviation corresponding the artefact expression in the Image J software. Both the artefact expression and the MAR effect were assessed using the Wilcoxon, Friedman (Dunn) and Kruskal-Wallis tests (significance level of 5%).
For both devices, MAR was statistically efficient only for the protocols E, and F. Protocol F (three metals on the adjacent area of the analysis region) showed higher artefact expression when compared to the others.
In conclusion, the new phantom design allowed the quantification of the metal artefact expression caused by titanium. The metal artefact expression is higher when more metal objects are positioned in the adjacent bone structures. MAR may not be effective to reduce artefact expression on the adjacencies of those objects for the devices studied.
设计一种新的体模，以评估在锥形束 CT 图像中考虑不同位置和数量的金属以及是否使用金属伪影减少（MAR）技术时，钛引起的伪影对骨结构的实际影响。
设计了一个包含八个穿孔的三个圆柱形聚甲基丙烯酸甲酯（PMMA）板体模，以模拟中板的下齿弓。将三个钛圆柱体放置在不同的位置和数量，以测试不同的临床情况，并量化五个骨圆柱体周围金属伪影的影响。在两个锥形束 CT 设备（OP300 Maxio 和 Picasso Trio）中，以七种不同的协议（Control、A-F）进行扫描。在 Image J 软件中，使用八个感兴趣区域测量每个皮质骨和松质骨周围的灰度值标准差，以对应伪影的表达。使用 Wilcoxon、Friedman（Dunn）和 Kruskal-Wallis 检验（显著性水平为 5%）评估伪影表达和 MAR 效果。
对于两种设备，仅在协议 E 和 F 中，MAR 具有统计学上的效果。与其他协议相比，协议 F（三个金属位于分析区域的相邻区域）显示出更高的伪影表达。
总之，新的体模设计允许量化钛引起的金属伪影表达。当更多的金属物体放置在相邻的骨结构中时，金属伪影表达更高。对于所研究的设备，MAR 可能无法有效地减少这些物体相邻区域的伪影表达。
