Schyns Lotte E J R, Almeida Isabel P, van Hoof Stefan J, Descamps Benedicte, Vanhove Christian, Landry Guillaume, Granton Patrick V, Verhaegen Frank
1 Department of Radiation Oncology (MAASTRO), GROW-School for Oncology and Developmental Biology, Maastricht University Medical Centre, Maastricht, Netherlands.
2 iMinds Medical IT-IBiTech-MEDISIP-INFINITY, De Pintelaan 185, Ghent, Belgium.
Br J Radiol. 2017 Jan;90(1069):20160480. doi: 10.1259/bjr.20160480. Epub 2016 Nov 2.
The aim of this work was to investigate whether quantitative dual-energy CT (DECT) imaging is feasible for small animal irradiators with an integrated cone-beam CT (CBCT) system.
The optimal imaging protocols were determined by analyzing different energy combinations and dose levels. The influence of beam hardening effects and the performance of a beam hardening correction (BHC) were investigated. In addition, two systems from different manufacturers were compared in terms of errors in the extracted effective atomic numbers (Z) and relative electron densities (ρ) for phantom inserts with known elemental compositions and relative electron densities.
The optimal energy combination was determined to be 50 and 90 kVp. For this combination, Z and ρ can be extracted with a mean error of 0.11 and 0.010, respectively, at a dose level of 60 cGy.
Quantitative DECT imaging is feasible for small animal irradiators with an integrated CBCT system. To obtain the best results, optimizing the imaging protocols is required. Well-separated X-ray spectra and a sufficient dose level should be used to minimize the error and noise for Z and ρ. When no BHC is applied in the image reconstruction, the size of the calibration phantom should match the size of the imaged object to limit the influence of beam hardening effects. No significant differences in Z and ρ errors are observed between the two systems from different manufacturers. Advances in knowledge: This is the first study that investigates quantitative DECT imaging for small animal irradiators with an integrated CBCT system.
本研究旨在探讨定量双能CT（DECT）成像对于配备集成锥束CT（CBCT）系统的小动物辐照仪是否可行。
通过分析不同能量组合和剂量水平来确定最佳成像方案。研究了射线硬化效应的影响以及射线硬化校正（BHC）的性能。此外，比较了来自不同制造商的两个系统在提取已知元素组成和相对电子密度的体模插入物的有效原子序数（Z）和相对电子密度（ρ）时的误差。
确定最佳能量组合为50和90 kVp。对于该组合，在60 cGy的剂量水平下，Z和ρ的提取平均误差分别为0.11和0.010。
定量DECT成像对于配备集成CBCT系统的小动物辐照仪是可行的。为了获得最佳结果，需要优化成像方案。应使用充分分离的X射线光谱和足够的剂量水平来最小化Z和ρ的误差和噪声。当在图像重建中不应用BHC时，校准体模的尺寸应与成像对象的尺寸匹配，以限制射线硬化效应的影响。不同制造商的两个系统在Z和ρ误差方面未观察到显著差异。知识进展：这是第一项研究配备集成CBCT系统的小动物辐照仪的定量DECT成像的研究。
