Department of Radiology, Hôpital Erasme, Université libre de Bruxelles, Brussels, Belgium.
Br J Radiol. 2014 Jan;87(1033):20130546. doi: 10.1259/bjr.20130546. Epub 2013 Nov 20.
To investigate the effect of a two-third reduction of the scanned length (i.e. 10 cm) on diagnosis of both pulmonary embolism (PE) and alternative diseases.
247 consecutive patients suspected of acute PE had a CT pulmonary angiography (CTPA) of the thorax (standard length, L). Based on this acquisition, a second set of images was created to obtain a scan length of 10 cm caudally to the aortic arch (l). Images were anonymized, randomized and interpreted by two independent readers. The quality of enhancement, the presence of PE and the possible alternative and/or complementary diagnoses were recorded. A McNemar exact test investigated differences in discrepancies between readers and between scan lengths.
57 (23%) patients had an acute PE. Among l sets, PE was missed by both readers in one (1.8%) patient, because the unique clot was localized in a subsegmental artery out of the 10-cm range. There were discrepancies between L and l sets in 9 (3.6%) and 11 (4.5%) patients, by Readers 1 and 2 (p=0.820), respectively. Discrepancies between the readers of L sets and those between both sets were not different regardless of the reader (p>0.99). There were discrepancies between both sets for alternative and/or complementary diagnoses in 43 (17.2%) patients.
Although its performance in diagnosing PE is maintained, CTPA should not be restricted to a range of 10 cm centred over the pulmonary hilum, because alternative and/or complementary diagnoses could be missed.
(1) A 10-cm CTPA acquisition reduces the radiation dose by two-thirds as compared with a standard one, but does not impair the accuracy for the diagnosis of PE. (2) Significant alternative diagnoses are missed in 17.2% of patients when reducing the acquisition height to 10 cm.
探讨扫描长度减少三分之二（即 10cm）对诊断肺栓塞（PE）和其他疾病的影响。
对 247 例疑似急性 PE 的连续患者进行胸部 CT 肺动脉造影（CTPA）（标准长度 L）。在此采集的基础上，创建第二组图像以获得主动脉弓（l）尾侧 10cm 的扫描长度。对图像进行匿名、随机化处理，并由两名独立读者进行解释。记录增强质量、PE 的存在以及可能的替代和/或补充诊断。采用 McNemar 精确检验比较了读者之间和扫描长度之间差异的差异。
57 例（23%）患者发生急性 PE。在 l 组中，由于唯一的血栓位于 10cm 范围之外的亚段动脉中，两位读者均漏诊了一位（1.8%）患者的 PE。L 和 l 组之间存在差异的患者分别为 9 例（3.6%）和 11 例（4.5%），由读者 1 和 2 分别（p=0.820）。无论读者如何，L 组读者之间和两组之间的差异均无差异（p>0.99）。在 43 例（17.2%）患者中，两组之间存在替代和/或补充诊断的差异。
尽管 CTPA 诊断 PE 的性能保持不变，但不应将 CTPA 限制在以肺门为中心的 10cm 范围内，因为可能会漏诊替代和/或补充诊断。
（1）与标准采集相比，10cm CTPA 采集可将辐射剂量减少三分之二，但不会影响 PE 的诊断准确性。（2）当采集高度减少到 10cm 时，17.2%的患者会错过重要的替代诊断。
