Department of Radiology, Academic Medical Center, University of Amsterdam, PB 22660, 1100 DD Amsterdam, The Netherlands.
Eur J Radiol. 2013 Aug;82(8):1144-58. doi: 10.1016/j.ejrad.2011.10.030. Epub 2011 Dec 7.
This article reviews two important aspects of CT-colonography, namely colonic distension and scan parameters. Adequate distension should be obtained to visualize the complete colonic lumen and optimal scan parameters should be used to prevent unnecessary radiation burden. For optimal distension, automatic carbon dioxide insufflation should be performed, preferably via a thin, flexible catheter. Hyoscine butylbromide is - when available - the preferred spasmolytic agent because of the positive effect on insufflation and pain/burden and its low costs. Scans in two positions are required for adequate distension and high polyp sensitivity and decubitus position may be used as an alternative for patients unable to lie in prone position. The great intrinsic contrast between air or tagging and polyps allows the use of low radiation dose. Low-dose protocol without intravenous contrast should be used when extracolonic findings are deemed unimportant. In patients suspected for colorectal cancer, normal abdominal CT scan protocols and intravenous contrast should be used in supine position for the evaluation of extracolonic findings. Dose reduction can be obtained by lowering the tube current and/or voltage. Tube current modulation reduces the radiation dose (except in obese patients), and should be used when available. Iterative reconstructions is a promising dose reducing tool and dual-energy CT is currently evaluated for its applications in CT-colonography. This review also provides our institution's insufflation procedure and scan parameters.
本文回顾了 CT 结肠成像的两个重要方面，即结肠扩张和扫描参数。应获得足够的扩张以可视化完整的结肠腔，并且应使用最佳的扫描参数以防止不必要的辐射负担。为了获得最佳的扩张，应通过薄而灵活的导管进行自动二氧化碳充气。氢溴酸东莨菪碱是首选的解痉剂，因为它对充气和疼痛/负担有积极影响，而且成本低。需要进行两个位置的扫描以获得充分的扩张和高息肉灵敏度，并且可以为无法仰卧的患者使用卧位作为替代。空气或标记与息肉之间的巨大固有对比度允许使用低辐射剂量。当认为额外结肠发现不重要时，应使用无静脉对比的低剂量方案。对于怀疑患有结直肠癌的患者，应在仰卧位使用正常的腹部 CT 扫描方案和静脉对比来评估额外结肠的发现。可以通过降低管电流和/或电压来减少剂量。管电流调制可降低辐射剂量（肥胖患者除外），并且在可用时应使用。迭代重建是一种有前途的降低剂量的工具，双能 CT 目前正在评估其在 CT 结肠成像中的应用。本文还提供了我们机构的充气程序和扫描参数。
