International Circulation: My first question is about CT angiography versus ventilation-perfusion (VQ) SPECT. Can you talk about some of the advantages and disadvantages of each and what takes priority in your practice?
    《国际循环》:我的第一个问题是关于CT血管造影和通气灌注（VQ）SEPCT。您能介绍两种检查方法的优缺点，以及您在实践中会优先选择哪一项吗？
    Dr. Le Gal: In terms of global safety and effectives， the two of comparable if they are used with a standardized， diagnostic strategy.  Obviously， one of the major concerns with the VQ is that it is often nonconclusive， but again， if you have a particular strategy， if you only do it in patients with non-high clinical probability but positive D-dimmer， and if you can associate it with a transform regression， you can reach the diagnostic conclusion in most cases without any need for a CT. That is why it works， even if it more difficult to interpret. Years ago， as the CT scan evolved from a single-detector CTs to multi-detector ones， these scans became more accurate for the detection of smaller embolisms. At the end of the day， it raised some concerns about the novel diagnosis of PE using multi- detector CT pulmonary angiogram (CTPA). A trial conducted by Anderson in 2007 compared the two diagnostic strategies. They found that， in terms of safety， there was no difference between the two of them， but using multi-detector CT they found a novel diagnosis of PE in over 5% of patients. With no difference in safety， more patients were being diagnosed with PE when using a CTPA. Likely， these additional patients would not have been diagnosed if using the VQ scan. These patients will be treated with anti-coagulants for nothing. The main explanation is likely that using， multi-detector CTs， there was a huge increase in the number of subsegmental PEs that were diagnosed. Using the first generation of CT scan， only 4%～5% of all PEs that were revealed to be subsegmental. Now with the MD CTs， that number is growing to 10%. Again， that is one of the elements under discussion. Another concern with the CT scan is radiation as patients receive more and more CTs during their life. On the other hand， of the advantages of CT is that in the presence of chest pain or shortness of breath， it can give you an alternative diagnosis to PE. The VQ can only answer the question: is there a PE or not? The CT scan can diagnosis PE， pneumonia， pleural effusion， pneumothorax， cancer， etc. These are the key elements under discussion. CT is simpler， you do the test and you follow the results， it is also good for alternative diagnoses， it increases the number of patients diagnosed with PE， but has a rate of radiation.
　Le Gal：如果使用标准诊疗策略，这两种方法在总体安全性和有效性方面相似。很显然，对VQ的主要担忧之一是它经常不能确诊。但是，如果你只对临床可能性不大但D-二聚体阳性的患者使用，并且和变换回归关联，就可以在绝大多数患者中不需要进行CT就能够得到诊断结论。这就是VQ有用的原因，即使解读结果存在困难。多年前，CT从单排CT升级为多排CT，对于小栓塞的检查更加精确。近来，关于使用多排CT肺血管造影（CTPA）诊断肺栓塞（PE）的新方法引起了一些关注。2007年，Anderson进行的试验比较了两种诊断策略。他们发现两种检查安全性没有差异，但是使用多排CT对超过5%的患者中新诊断PE。而使用CTPA则对更多患者新诊断PE。如果使用VQ检查，这部分患者很可能就不会被诊断。因此这些患者接受了抗凝治疗，而没有增加额外风险。主要的解释可能是使用多排CT会大大增加亚段肺栓塞的诊断率。使用第一代CT检查，只有4%～5%的PE是亚段PE，而使用多排CT时上升至10%。这个问题也正在被讨论。另一个关于CT的担忧是辐射，患者终生接受的CT检查越来越多。另一方面，CT的一个优点是如果存在胸痛或呼吸困难，能够提供替代诊断。VQ只能回答是或不是PE的问题，而CT能够诊断PE、肺炎、胸腔积液、气胸、肿瘤等。这些也是在讨论的重要问题。CT更简单，做检查然后追踪结果。CT对替代诊断也有好处。CT增加了PE的诊断率，但是也存在辐射的问题。