Dabirrahmani Danè, Magnussen John, Appleyard Richard Charles
From the Australian School of Advanced Medicine, Macquarie University, Sydney, Australia.
J Comput Assist Tomogr. 2015 Nov-Dec;39(6):925-35. doi: 10.1097/RCT.0000000000000300.
To assess the accuracy and suitability of dual-energy computed tomography (DECT) in scanning metals used in orthopedic implants.
Four metal phantoms (Cobalt Chrome, Titanium Grade 5, Stainless Steel 316, and Stainless Steel 630), commonly used materials in orthopedic implants, were scanned by conventional, polychromatic CT as well as Gemstone Spectrum Imaging (GSI) DECT, with and without metal artefact reduction software (MARS). Scans were assessed for artefact based on Hounsfield unit values; and surfaces generated, based on a Canny edge detection algorithm. Two separate metal implants were also scanned and assessed for dimensional accuracy.
Conventional, polychromatic CT, and GSI DECT (without MARS) scans displayed major beam hardening in the presence of all four metals. The GSI DECT with MARS showed very clear and reproducible boundaries with minimal noise surrounding the metal phantoms. However, geometric analysis found overestimation of the dimensions, volume, and surface area for most of the metal phantoms. Titanium displayed the least artefact, compared to the other metals, in all scan scenarios.
Although metal artefact reduction using GSI DECT looks superior to conventional CT, when measured objectively, it was shown to overestimate geometries and skew dimensions. The GSI DECT with MARS should be used with caution, especially when assessing questions of implant shape or wear.
评估双能计算机断层扫描（DECT）在扫描骨科植入物所用金属方面的准确性和适用性。
四个金属模型（钴铬合金、5级钛、316不锈钢和630不锈钢），这些是骨科植入物中常用的材料，通过传统的多色CT以及宝石能谱成像（GSI）DECT进行扫描，扫描时使用和不使用金属伪影减少软件（MARS）。基于亨氏单位值评估扫描的伪影；并基于Canny边缘检测算法生成表面。还对两个单独的金属植入物进行了扫描并评估其尺寸精度。
传统的多色CT扫描以及GSI DECT（不使用MARS）扫描在所有四种金属存在的情况下均显示出严重的束硬化现象。使用MARS的GSI DECT显示出非常清晰且可重复的边界，金属模型周围的噪声最小。然而，几何分析发现大多数金属模型的尺寸、体积和表面积被高估。在所有扫描情况下，与其他金属相比，钛显示出的伪影最少。
尽管使用GSI DECT减少金属伪影看起来优于传统CT，但客观测量时发现它会高估几何形状并使尺寸出现偏差。使用MARS的GSI DECT应谨慎使用，尤其是在评估植入物形状或磨损问题时。
