Taguchi Narumi, Oda Seitaro, Nakaura Takeshi, Utsunomiya Daisuke, Funama Yoshinori, Imuta Masanori, Yuki Hideaki, Nagayama Yasunori, Kidoh Masafumi, Hirata Kenichiro, Iyama Yuji, Namimoto Tomohiro, Kai Noriyuki, Hatemura Masahiro, Yamashita Yasuyuki
1 Department of Diagnostic Radiology, Faculty of Life Sciences, Kumamoto University , Kumamoto , Japan.
2 Department of Medical Physics, Faculty of Life Sciences, Kumamoto University , Kumamoto , Japan.
Br J Radiol. 2018 Jan;91(1081):20170285. doi: 10.1259/bjr.20170285. Epub 2017 Nov 6.
Different CT scanners have different X-ray spectra and photon energies indicating that contrast enhancement vary among scanners. However, this issue has not been fully validated; therefore, we performed phantom and clinical studies to assess this difference.
Two scanners were used: scanner-A and scanner-B. In the phantom study, we compared the contrast enhancement between the scanners at tube voltage peaks of 80, 100 and 120 kVp. Then, we calculated the effective energies of the two CT scanners. In the clinical study, 40 patients underwent abdominal scanning with scanner-A and another 40 patients with scanner-B, with each group using the same scanning protocol. The contrast enhancement of abdominal organs was assessed quantitatively (based on the absolute difference between the attenuation of unenhanced scans and contrast-enhanced scans) and qualitatively. A two-tailed independent Student's t-test and or the Mann-Whitney U test were used to compare the discrepancies.
In the phantom study, contrast enhancement for scanner-B was 36.9, 32.6 and 30.8% higher than that for scanner-A at 80, 100 and 120 kVp, respectively. The effective energies were higher for scanner-A than for scanner-B. In the quantitative analysis for the clinical study, scanner-B yielded significantly better contrast enhancement of the hepatic parenchyma, pancreas, kidney, portal vein and inferior vena cava compared with that of scanner-A. The mean visual scores for contrast enhancement were also significantly higher on images obtained by scanner-B than those by scanner-A.
There were significant differences in contrast enhancement of the abdominal organs between the compared CT scanners from two different vendors even at the same scanning and contrast parameters. Advances in knowledge: Awareness of the impact of different X-ray energies on the resultant attenuation of contrast material is important when interpreting clinical CT images.
不同的CT扫描仪具有不同的X射线光谱和光子能量，这表明不同扫描仪之间的对比增强效果存在差异。然而，这一问题尚未得到充分验证；因此，我们进行了体模和临床研究来评估这种差异。
使用了两台扫描仪：扫描仪A和扫描仪B。在体模研究中，我们比较了两台扫描仪在80、100和120 kVp管电压峰值下的对比增强情况。然后，我们计算了两台CT扫描仪的有效能量。在临床研究中，40例患者使用扫描仪A进行腹部扫描，另外40例患者使用扫描仪B进行腹部扫描，每组采用相同的扫描方案。对腹部器官的对比增强进行了定量评估（基于未增强扫描和增强扫描的衰减绝对差值）和定性评估。使用双尾独立样本t检验和/或曼-惠特尼U检验来比较差异。
在体模研究中，扫描仪B在80、100和120 kVp时的对比增强分别比扫描仪A高36.9%、32.6%和30.8%。扫描仪A的有效能量高于扫描仪B。在临床研究的定量分析中，与扫描仪A相比，扫描仪B对肝实质、胰腺、肾脏、门静脉和下腔静脉的对比增强明显更好。扫描仪B获得的图像上对比增强的平均视觉评分也显著高于扫描仪A获得的图像。
即使在相同的扫描和对比参数下，来自两个不同厂家的CT扫描仪在腹部器官的对比增强方面仍存在显著差异。知识进展：在解读临床CT图像时，了解不同X射线能量对造影剂最终衰减的影响很重要。
