Norfolk and Norwich University Hospital, Norwich, UK.
Skeletal Radiol. 2013 Feb;42(2):275-82. doi: 10.1007/s00256-012-1458-6. Epub 2012 Jun 9.
The aim of this study was to determine whether high keV monoenergetic reconstruction of dual energy computed tomography (DECT) could be used to overcome the effects of beam hardening artefact that arise from preferential deflection of low energy photons.
Two phantoms were used: a Charnley total hip replacement set in gelatine and a Catphan 500. DECT datasets were acquired at 100, 200 and 400 mA (Siemens Definition Flash, 100 and 140 kVp) and reconstructed using a standard combined algorithm (1:1) and then as monoenergetic reconstructions at 10 keV intervals from 40 to 190 keV. Semi-automated segmentation with threshold inpainting was used to obtain the attenuation values and standard deviation (SD) of the streak artefact. High contrast line pair resolution and background noise were assessed using the Catphan 500.
Streak artefact is progressively reduced with increasing keV monoenergetic reconstructions. Reconstruction of a 400 mA acquisition at 150 keV results in reduction in the volume of streak artefact from 65 cm(3) to 17 cm(3) (74 %). There was a decrease in the contrast to noise ratio (CNR) at higher tube voltages, with the peak CNR seen at 70-80 keV. High contrast spatial resolution was maintained at high keV values.
Monoenergetic reconstruction of dual energy CT at increasing theoretical kilovoltages reduces the streak artefact produced by beam hardening from orthopaedic prostheses, accompanied by a modest increase in heterogeneity of background image attenuation, and decrease in contrast to noise ratio, but no deterioration in high contrast line pair resolution.
本研究旨在确定双能 CT（DECT）的高 keV 单能量重建是否可用于克服因低能光子优先偏转而产生的束硬化伪影的影响。
使用两个体模：一个置于明胶中的 Charnley 全髋关节置换套件和一个 Catphan 500。在 100、200 和 400 mA（西门子 Definition Flash，100 和 140 kVp）下采集 DECT 数据集，并使用标准组合算法（1:1）进行重建，然后以 10 keV 的间隔从 40 到 190 keV 进行单能量重建。使用半自动分割和阈值内插进行条纹伪影的衰减值和标准偏差（SD）的获取。使用 Catphan 500 评估高对比线对分辨率和背景噪声。
条纹伪影随 keV 单能量重建的增加而逐渐减少。在 150 keV 下对 400 mA 采集进行重建，可使条纹伪影的体积从 65 cm3 减少到 17 cm3（74%）。随着管电压的升高，对比噪声比（CNR）降低，在 70-80 keV 时达到峰值 CNR。在高 keV 值时保持了高对比度空间分辨率。
双能 CT 的单能量重建随着理论千伏值的增加，可减少来自矫形假体的束硬化伪影，同时背景图像衰减的异质性略有增加，对比噪声比降低，但高对比度线对分辨率无恶化。
