Almeida Isabel P, Schyns Lotte E J R, Öllers Michel C, van Elmpt Wouter, Parodi Katia, Landry Guillaume, Verhaegen Frank
Department of Radiation Oncology (MAASTRO), GROW - School for Oncology and Developmental Biology, Maastricht University Medical Centre, Maastricht, The Netherlands.
Department of Medical Physics, Faculty of Physics, Ludwig-Maximilians-Universität München, Am Coulombwall 1, 85748, Garching b. München, Germany.
Med Phys. 2017 Jan;44(1):171-179. doi: 10.1002/mp.12000. Epub 2017 Jan 10.
To assess image quality and to quantify the accuracy of relative electron densities (ρ ) and effective atomic numbers (Z ) for three dual-energy computed tomography (DECT) scanners: a novel single-source split-filter (i.e., twin-beam) and two dual-source scanners.
Measurements were made with a second generation dual-source scanner at 80/140Sn kVp, a third-generation twin-beam single-source scanner at 120 kVp with gold (Au) and tin (Sn) filters, and a third-generation dual-source scanner at 90/150Sn kVp. Three phantoms with tissue inserts were scanned and used for calibration and validation of parameterized methods to extract ρ and Z , whereas iodine and calcium inserts were used to quantify Contrast-to-Noise-Ratio (CNR). Spatial resolution in tomographic images was also tested.
The third-generation scanners have an image resolution of 6.2, ~0.5 lp/cm higher than the second generation scanner. The twin-beam scanner has low imaging contrast for iodine materials due to its limited spectral separation. The parameterization methods resulted in calibrations with low fit residuals for the dual-source scanners, yielding values of ρ and Z close to the reference values (errors within 1.2% for ρ and 6.2% for Z for a dose of 20 mGy, excluding lung substitute tissues). The twin-beam scanner presented overall higher errors (within 3.2% for ρ and 28% for Z , also excluding lung inserts) and also larger variations for uniform inserts.
Spatial resolution is similar for the three scanners. The twin-beam is able to derive ρ and Z , but with inferior accuracy compared to both dual-source scanners.
评估三种双能计算机断层扫描（DECT）扫描仪的图像质量，并量化相对电子密度（ρ）和有效原子序数（Z）的准确性：一种新型单源分体滤波器（即双束）扫描仪和两种双源扫描仪。
使用第二代双源扫描仪在80/140Sn kVp下进行测量，第三代双束单源扫描仪在120 kVp下使用金（Au）和锡（Sn）滤波器进行测量，以及第三代双源扫描仪在90/150Sn kVp下进行测量。对三个带有组织插入物的体模进行扫描，并用于校准和验证提取ρ和Z的参数化方法，而碘和钙插入物用于量化对比度噪声比（CNR）。还测试了断层图像中的空间分辨率。
第三代扫描仪的图像分辨率为6.2，比第二代扫描仪高约0.5 lp/cm。双束扫描仪由于其有限的光谱分离，对碘材料的成像对比度较低。参数化方法对双源扫描仪进行校准后拟合残差较低，得到的ρ和Z值接近参考值（对于20 mGy的剂量，ρ的误差在1.2%以内，Z的误差在6.2%以内，不包括肺替代组织）。双束扫描仪总体误差较高（ρ在3.2%以内，Z在28%以内，也不包括肺插入物），并且均匀插入物的变化也较大。
三种扫描仪的空间分辨率相似。双束扫描仪能够得出ρ和Z，但与两种双源扫描仪相比准确性较差。
