Cai Wenli, Zhang Da, Lee June-Goo, Shirai Yu, Kim Se Hyung, Yoshida Hiroyuki
Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Boston, MA 02114, USA.
J Comput Assist Tomogr. 2013 Mar-Apr;37(2):183-94. doi: 10.1097/RCT.0b013e31827bc266.
The purpose of our study was to measure the dual-energy index (DEI) value of colonic luminal air in both phantom and clinical fecal-tagging dual-energy computed tomography (CT) colonography (DE-CTC) images and to demonstrate its impact on dual-energy electronic cleansing.
For the phantom study, a custom-ordered colon phantom was scanned by a dual-energy CT scanner (SOMATON Definition Flash; Siemens Healthcare, Forchheim, Germany) at two photon energies: 80 and 140 kVp. Before imaging, the phantom was filled with a 300-mL mixture of simulated fecal materials tagged by a nonionic iodinated contrast agent at three contrast concentrations: 20, 40, and 60 mg/mL. Ten regions-of-interest (ROIs) were randomly placed in each of the colonic luminal air, abdominal fat, bony structure, and tagged material in each scan. For the clinical study, 22 DE-CTC (80 and 140 kVp) patient cases were collected, who underwent a low-fiber, low-residue diet bowel preparation and orally administered iodine-based fecal tagging. Twenty ROIs were randomly placed in each of the colonic luminal air, abdominal fat, abdominal soft tissue, and tagged fecal material in each scan. For each ROI, the mean CT values in both 80- and 140-kVp images were measured, and then its DEI was calculated.
In the phantom study, the mean DEI values of luminal air were 0.270, 0.298, 0.386, and 0.402 for the four groups of tagging conditions: no tagged material and tagged with three groups of contrast concentrations at 20, 40, and 60 mg/mL. In the clinical study, the mean DEI values were 0.341, -0.012, -0.002, and 0.188 for colonic luminal air, abdominal fat, abdominal soft tissue, and tagged fecal material, respectively.
In our study, we observed that the DEI values of colonic luminal air in DE-CTC images (>0.10) were substantially higher than the theoretical value of 0.0063. In addition, the observed DEI values of colonic luminal air were significantly higher than those of soft tissue. These findings have an important impact on electronic cleansing: it may provide an effective means of differentiating colonic soft-tissue structures from the air-tagging mixture caused by the partial volume effect and thus of minimizing the cleansing artifacts.
我们研究的目的是测量结肠腔内空气在体模和临床粪便标记双能量计算机断层扫描（CT）结肠成像（DE-CTC）图像中的双能量指数（DEI）值，并证明其对双能量电子清洗的影响。
对于体模研究，使用双能量CT扫描仪（SOMATON Definition Flash；西门子医疗，德国福希海姆）在两个光子能量（80和140 kVp）下扫描定制的结肠体模。在成像前，用非离子型碘化造影剂标记的模拟粪便材料的300 mL混合物填充体模，造影剂浓度分为三组：20、40和60 mg/mL。在每次扫描中，在结肠腔内空气、腹部脂肪、骨骼结构和标记材料的每一项中随机放置10个感兴趣区域（ROI）。对于临床研究，收集了22例DE-CTC（80和140 kVp）患者病例，这些患者接受了低纤维、低残渣饮食的肠道准备，并口服了碘基粪便标记物。在每次扫描中，在结肠腔内空气、腹部脂肪、腹部软组织和标记粪便材料的每一项中随机放置20个ROI。对于每个ROI，测量80 kVp和140 kVp图像中的平均CT值，然后计算其DEI。
在体模研究中，对于四组标记条件：无标记材料以及标记有20、40和60 mg/mL三组造影剂浓度，腔内空气的平均DEI值分别为0.270、0.298、0.386和0.402。在临床研究中，结肠腔内空气、腹部脂肪、腹部软组织和标记粪便材料的平均DEI值分别为0.341、-0.012、-0.002和0.188。
在我们的研究中，我们观察到DE-CTC图像中结肠腔内空气的DEI值（>0.10）显著高于理论值0.0063。此外，观察到的结肠腔内空气的DEI值显著高于软组织的DEI值。这些发现对电子清洗有重要影响：它可能提供一种有效的方法，将结肠软组织结构与由部分容积效应引起的空气标记混合物区分开来，从而将清洗伪影降至最低。
