Institute for Diagnostic and Interventional Radiology, Clinic of the Goethe University, Theodor-Stern-Kai 7, 60590 Frankfurt, Germany.
Eur J Radiol. 2011 Dec;80(3):e483-7. doi: 10.1016/j.ejrad.2010.09.030. Epub 2010 Oct 22.
Lung perfusion analysis at dual energy CT (DECT) is sensitive to beam hardening artifacts from dense contrast material (CM). We compared two scan and four CM injection protocols in terms of severity of artifacts and attenuation levels in the thoracic vessels.
Data of 120 patients who had undergone dual source dual energy CT pulmonary angiography for suspected acute pulmonary embolism were evaluated. Group 1 (n=30) was scanned in craniocaudal direction using 64×0.6 mm collimation; groups 2-4 (n=30 each) were scanned in caudocranial direction using 14×1.2 mm collimation. In groups 1-3 biphasic injection protocols with different amounts of CM and NaCl were investigated. In group 4 a split-bolus protocol with an initial CM bolus of 50 ml followed by 30 ml of a 70%:30% NaCl/CM mixture and a 50 ml NaCl chaser bolus was used. CT density values in the subclavian vein (SV), superior vena cava (SVC), pulmonary artery tree (PA), and the descending aorta (DA) were measured. Artifacts arising from the SV and SVC on DE pulmonary iodine distribution map were rated on a scale from 1 to 5 (1=fully diagnostic; 5=non-diagnostic) by two blinded readers.
In protocol 4 mean attenuation in the SV (645±158 HU) and SVC (389±114 HU) were significantly lower compared to groups 1-3 (p<0.002). Artifacts in group 4 (1.1±0.4 and 1.5±0.7 for the SV and SVC, respectively) were rated significantly less severe compared to group 1 (3.2±1.0 and 3.0±1.1), 2 (2.6±1.1 and 2.3±1.0) and 3 (1.9±0.9 and 1.9±0.7) (p<0.01 for all), whereas no significant difference was found between groups 1 and 2 for the subclavian vein (p=0.07). Attenuation in the PA was also significantly lower in group 4 (282±116 HU) compared to group 1 (397±137 HU), group 2 (376±115 HU) and group 3 (311±104 HU), but still on a diagnostic level.
Split-bolus injection provides sufficient attenuation for pulmonary DECT angiography while beam hardening artifacts arising from high density contrast material in the thoracic vessels can be reduced significantly.
双能 CT（DECT）的肺灌注分析对来自高密度对比剂（CM）的射束硬化伪影敏感。我们比较了两种扫描和四种 CM 注射方案在胸部血管伪影严重程度和衰减水平方面的差异。
对 120 例疑似急性肺栓塞行双源双能 CT 肺动脉造影的患者进行评估。第 1 组（n=30）采用 64×0.6mm 准直器行颅尾向扫描；第 2-4 组（n=30 例/组）采用 14×1.2mm 准直器行尾到头向扫描。在第 1-3 组中，研究了不同 CM 和 NaCl 量的双相注射方案。在第 4 组中，使用了初始 CM 剂量为 50ml 的分段-推注方案，随后为 30ml 70%：30% NaCl/CM 混合物和 50ml NaCl 推注剂。测量锁骨下静脉（SV）、上腔静脉（SVC）、肺动脉树（PA）和降主动脉（DA）的 CT 密度值。由两位盲法观察者对 DE 肺部碘分布图上 SV 和 SVC 的伪影进行评分，从 1 到 5 分（1=完全诊断；5=无法诊断）。
与第 1-3 组相比，第 4 组 SV（645±158HU）和 SVC（389±114HU）的平均衰减值明显降低（p<0.002）。第 4 组的伪影（SV 和 SVC 分别为 1.1±0.4 和 1.5±0.7）明显轻于第 1 组（3.2±1.0 和 3.0±1.1）、第 2 组（2.6±1.1 和 2.3±1.0）和第 3 组（1.9±0.9 和 1.9±0.7）（p<0.01 ），而 SV 组间差异无统计学意义（p=0.07）。第 4 组 PA 的衰减值（282±116HU）也明显低于第 1 组（397±137HU）、第 2 组（376±115HU）和第 3 组（311±104HU），但仍处于诊断水平。
分段-推注式注射为 DECT 肺动脉造影提供了足够的衰减，同时可显著减少来自胸部血管高密度对比剂的射束硬化伪影。
