Chest CT scanning for clinical suspected thoracic aortic dissection: beware the alternate diagnosis

The aim of the study was retrospectively to evaluate the spectrum of chest diseases in patients presenting with clinical suspicion of thoracic aortic dissection in the emergency department. We performed a retrospective medical records review of 86 men and 44 women (ages ranging between 23 and 106 years) with clinically suspected aortic dissection, for CT scan findings and final clinical diagnoses dating between January 1996 and September 2001. All images were obtained by using a standard protocol for aortic dissection. We found aortic dissection in 32 patients (24.6%), 22 of which were Stanford classification type A and 10 Stanford type B. In 70 patients (53.9%), chest pain could not be explained by the CT scan findings. However, in 28 patients (21.5%), CT scanning did reveal an alternate diagnosis that, along with the clinical impression, probably explained the patients' presenting symptoms, including: hiatal hernia (7), pneumonia (5), intrathoracic mass (4), pericardial effusion/hemopericardium (3), esophageal mass/rupture (2), aortic aneurysm without dissection (2), pulmonary embolism (2), pleural effusion (1), aortic rupture (1), and pancreatitis (1). In cases where there is clinical suspicion of aortic dissection, CT scan findings of an alternate diagnosis for the presenting symptoms are only slightly less common than the finding of aortic dissection itself. Although the spectrum of findings will vary depending upon your patient population, beware the alternate diagnosis. Electronic Publication     

Motion artifact simulating aortic dissection on CT

We recently imaged two patients clinically suspected of having aortic dissection whose contrast-enhanced CT examinations, obtained on a new scanner with a 1-sec scanning time, showed findings suggesting an ascending aortic dissection. The subsequent clinical course and evaluation implied that the CT findings were predominantly artifactual. We identified identical artifacts in 18% of 50 consecutive contrast-enhanced CT examinations performed for a variety of indications on the same scanner. The double-lumen artifact, simulating an intimal flap, occurs in the proximal ascending aorta and is limited to one or two contiguous transaxial images. The artifact was not detected on two other CT units. We believe the artifact arises from motion of the aortic wall and the surrounding pericardial recesses during image acquisition.     

彩超在诊断主动脉夹层中的应用

目的评价彩超诊断主动脉夹层的临床价值。方法采用HP—Image Point Hx和PH—HD11彩超，对2000年2月至2007年1月间诊断的21例主动脉夹层患者进行总结分析。结果19例主动脉夹层患者均经彩超确诊，2例可疑病例经尸检证实。结论彩超对主动脉夹层的诊断、治疗方案选择及预后判断具有重要的临床价值。     

Suspected aortic dissection and other aortic disorders: multi-detector row CT in 373 cases in the emergency setting

PURPOSE: To retrospectively review the authors' experience with multi-detector row computed tomography (CT) for detection of aortic dissection in the emergency setting. MATERIALS AND METHODS: The investigation was institutional review board approved, did not require informed patient consent, and was HIPAA compliant. In 373 clinical evaluations in the emergency setting, 365 patients suspected of having aortic dissection and/or other aortic disorders underwent multidetector CT. Criteria for acute aortic disorder were confirmed by using surgical and pathologic diagnoses or findings at clinical follow-up and any subsequent imaging as the reference standard. Positive cases were characterized according to type of disorder interpreted. Resulting sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and accuracy were calculated by using two-way contingency tables. All cases found to be negative for acute aortic disorders were grouped according to alternative CT findings. RESULTS: Sixty-seven (18.0%) of the 373 cases were interpreted as positive for acute aortic disorder. One hundred twelve acute aortic disorders were identified in these 67 cases: 23 acute aortic dissections, 14 acute aortic intramural hematomas, 20 acute penetrating aortic ulcers, 44 new or enlarging aortic aneurysms, and 11 acute aortic ruptures. Three hundred five (81.8%) cases were interpreted as negative for acute aortic disorder. In 48 negative cases, multidetector CT depicted alternative findings that accounted for the clinical presentation. Of these, three included both acute aortic disorders and alternative findings, and 45 included only alternative findings. One (0.3%) case was indeterminate for acute aortic disorder. Overall, 112 findings were interpreted as positive for acute aortic disorder, an alternative finding, or both at CT. No interpretations were false-positive, one was false-negative, 67 were true-positive, and 304 were true-negative. Sensitivity, specificity, PPV, NPV, and accuracy were 99% (67 of 68), 100% (304 of 304), 100% (67 of 67), 99.7% (304 of 305), and 99.5% (371 of 373), respectively. CONCLUSION: The positivity rate for acute aortic dissection or other acute aortic disorder in 373 cases examined at multi-detector row CT was 18.0%.     

超声、MR、CT、X线诊断主动脉夹层的比较

目的：比较超声、MR、CT及X线对主动脉夹层的诊断价值。方法：2005—01～2008—09经手术病理证实的26例主动脉夹层患者,26例均经超声、X线检查,17例经MR及CT检查,重点观察超声主动脉声像,内膜有无撕裂及撕裂部位,真假腔血流情况,主动脉瓣有无受累及瓣膜反流情况、心包积液、左室收缩功能等。结果．26例超声诊断25例,其中12例为DeB—bakeyI型,占46．2％,5例为Ⅱ型,占19．2％,9例为Ⅲ型,占34．6％,I型最常见。19例中量以上主动脉瓣反流,7例少量主动脉瓣反流,9例少一中量心包积液。16例LVEF％及LVFS％降低。17例经MR及CT检查诊断15例,26例胸片提示主动脉增宽,心影增大。结论：超声可作为诊断主动脉夹层的首选检查项目。     

Useful CT findings for predicting the progression of aortic intramural hematoma to overt aortic dissection

PURPOSE: The purpose of this work was to assess useful CT findings for predicting the progression of aortic intramural hematoma to aortic dissection. METHOD: We analyzed the CT findings of 29 patients with aortic intramural hematoma with regard to the following: involved site, maximum thickness of hematoma, presence or absence of compression of true lumen, and pericardial and pleural effusion. CT findings were compared with those of the patients who progressed to aortic dissection (Group I) and those who did not (Group II). Each CT finding was evaluated with independent t test and Mann-Whitney U test (p < 0.05). RESULTS: Seven of 8 cases of Type A aortic intramural hematoma and 3 of 21 cases of Type B aortic intramural hematoma progressed to aortic dissection. The type of aortic intramural hematoma, maximum thickness of hematoma, compression of true lumen, and pericardial or pleural effusion were significantly different in Groups I and II. CONCLUSION: Type A aortic intramural hematoma, maximum thickness of hematoma, compression of true lumen, and pericardial or pleural effusion are the useful CT findings for predicting the progression of aortic intramural hematoma to aortic dissection.     

CT recognition of acute aortic dissection

Twenty-six patients with suspected acute aortic dissection were investigated using computed tomography (CT) as the primary mode of investigation. The diagnosis was controlled by aortography or surgery or both. There were no false-positive or false-negative studies using CT. Aortography was performed on 19 of the 21 patients with aortic dissection and was positive in each instance. However, in two illustrated cases, CT indicated proximal or type A aortic dissection, whereas the corresponding aortograms indicated distal or type B aortic dissection. In two of the 21 acute aortic dissections, only CT was performed, and in both instances surgical confirmation was obtained. The results suggest that CT is at least as accurate as aortography in the diagnosis of acute aortic dissection.     

Radiological evaluation of the ascending aorta following repair of type A dissection

A patient with persistent chronic dissection proximal to an aortic interposition graft for repair of a type A dissection prompted us to review the computed tomographic (CT) findings in 14 other such patients 5–47 months after surgery. No other case of proximal aortic dissection was identified although dilatation of the aortic root proximal to the graft was present in 8 patients (57%). Persistent dissection distal to the graft in 11 patients (79%) was in keeping with that reported by other workers. Chronic dissection proximal to the surgical repair of a dissection seems a rare although important complication     

螺旋CT不同成像方法在主动脉夹层诊断中的比较

目的 评估螺旋CT不同成像方法在主动脉夹层诊断中的意义。资料与方法 对29例主动脉夹层患者的2D、MPR以及包括MIP、SSD和3DMT的三维成像进行对比。其中10例与手术所见对照。结果 2D、MPR和3DMT成像对内膜瓣的显示率为93.1％(27／29)，MIP、SSD和3DMT成像均不能显示血管腔内膜瓣轮廓；2D成像对破口的显示率为65．5％(19／29)，与手术符合率为100％(10／10)，MPR成像的显示率为13．8％(4／29)，MIP、SSD和3DMT未能显示破口；2D、MPR和3DMT成像对真、假腔的显示率为93．1％(27／29)，区分率均为92．6％(25／27)；SSD对两腔显示率为68.9％(20／29)，不能区分真假腔，有2例仅显示了一个腔；2D、MPR和3DMT对血栓的显示率均为51.7％(15／29)，SSD为13．8％(4／29)；2D成像100％(29／29)能判断其起始与终止部位。MPR能部分分段显示，SSD和3DMT均能整体显示；夹层邻近的血管分支的受累，2D图像显示率为71.4％(20／28)，其余重建方法难以显示。结论 螺旋CT对主动脉夹层的成像能采用多种重建方法，提供具有各自特点的图像信息，满足临床的要求。     

主动脉夹层支架置入术前CT的诊断价值(附9例报告)

目的:探讨主动脉夹层行支架置入术前CT检查的诊断价值及对手术的指导意义.方法:回顾性分析9例主动脉夹层患者的支架置入术及CT影像资料,分析术前CT对支架置入术的指导作用及手术对CT的诊断要求.结果:主动脉夹层支架置入术前行CT平扫、增强及三维重建可较准确地反映主动脉夹层的分型、内膜裂口、周围脏器血供等情况.根据术前CT诊断信息设计手术,8例手术成功,1例术中发现病情发展而中止手术.结论:CT可较准确地诊断主动脉夹层,并为支架置入术提供重要信息.     

CT diagnosis of acute aortic dissection; clinical importance of acute aortic dissection with non-opacified false lumen

Sixteen (47.5%) of 35 patients with acute aortic dissection showed a non-opacified crescent in the aorta on an initial contrast CT. Seven of these 16 patients underwent cineangiography soon after the initial CT, and in all 7 patients, neither an intimal tear nor an intimal flap was obtained. All but one of above 16 patients were followed by CT. Mean duration of follow-up was 9.6 months. In 10 of 15 patients with non-opacified false lumen, the false lumen remained non-opacified until the last examination. Moreover, in 6 of these 10 patients, the false lumen shrunk, and in the other 3, it disappeared completely on follow-up CT. On the other hand, in remaining 5 of these 15 patients who were initially diagnosed to have non-opacified false lumen, the false lumen became opacified and enlarged in size on follow-up CT performed in the first 14 weeks. Moreover, in 4 of these 5 patients, the false lumen became opacified in the only first 6 weeks. No matter how intensive care should be paid at least for the first 6 weeks, it seems that patients with aortic dissection which have non-opacified false lumen had good prognosis in comparison to patients with ordinary aortic dissections which have opacified false lumen. We believe aortic dissection with non-opacified false lumen may consist of two type of aortic dissection, one has no intimal tear, the other has some intimal tears and a thrombosed false lumen. In conclusion, CT is the most useful modality in diagnosing acute aortic dissection. The reasons are the incidence of acute aortic dissection with non-opacified false lumen was high, patients with non-opacified false lumen had good prognosis, and it was difficult to diagnose aortic dissection with non-opacified false lumen by conventional cineangiography and/or DSA.     

螺旋CT血管造影及三维重建在主动脉夹层诊断中的应用

目的:评价螺旋CT血管造影(SCTA)及三维重建在主动脉夹层诊断中的临床应用。方法:对21例主动脉夹层患者进行了SCTA成像及三维重建,并与手术及血管造影对照。结果:SCTA能清楚显示主动脉夹层病变及其复杂的解剖关系,如双腔、内膜片及累及的范围等。与血管造影及手术对照,SCTA的诊断符合率达100％。结论:SCTA二维与三维重建的联合应用,有助于主动脉夹层的诊断并可指导手术,且有望取代传统血管造影。     

16层螺旋CT血管成像技术在主动脉夹层中的临床价值

目的:探讨16层CT血管成像在主动脉夹层的诊断和临床治疗中的应用价值。方法:27例主动脉夹层患者均行16层CT胸腹联合平扫和增强扫描,采用多平面重组(MPR)、最大密度投影(MIP)、容积再现(VR)及表面遮盖显示(SSD)等后处理方法,重点观察和评价主动脉夹层的真假腔、内膜片、内膜破口以及重要分支血管的受累情况。结果:原始横轴位图像对病变信息的存储最为可靠;不同的重组方式所得图像有不同的显示特点;27例均很好地显示了主动脉全程及其分支,显示真、假腔27例(100%)、显示内膜片(100%)、内膜破口24例(88.9%)、假腔内血栓形成9例(30%)。结论:16层螺旋CT血管成像可以全面显示主动脉夹层的病变和解剖细节,在主动脉夹层的诊断和临床治疗中有重要的临床应用价值。     

Descending thoracic aortic aneurysm: thoracic CT findings after endovascular stent-graft placement.

PURPOSE: To evaluate the usefulness of thoracic computed tomography (CT) after placement of an endovascular stent-graft for the treatment of descending thoracic aortic aneurysm. MATERIALS AND METHODS: From 1992 to 1996, 85 patients with thoracic aortic aneurysm underwent stent-graft placement. In 63 patients, thoracic CT scans were obtained both before and within 10 days after placement. The CT findings were retrospectively studied, and their clinical effect analyzed. In 20 of 63 patients, long-term follow-up CT findings were also evaluated. RESULTS: After stent-graft placement in the 63 patients, CT demonstrated an increase in pleural effusion in 46 (73%), periaortic changes in 21 (33%), perigraft leak in 13 (21%), atelectasis in six (10%), mural thrombus within the stent-graft in two (3%), and new aortic dissection in one (2%). The mean maximum diameter of the aneurysm was 58.8 mm before and 60.0 mm after stent-graft insertion. Sixty-two (98%) patients were successfully treated until discharge. Interventional procedures were performed to eliminate the leakage into the aneurysm sac in 10 patients with perigraft flow depicted at CT. Other complications were managed conservatively. CONCLUSION: Thoracic CT is useful in the treatment of patients after stent-graft insertion for the management of descending thoracic aortic aneurysm.     

不典型主动脉夹层的多层螺旋CT诊断价值

目的:回顾性分析不典型主动脉夹层(atypical aortic dissection,AAD)的CT表现,探讨螺旋CT诊断AAD的价值。方法:25例AAD患者,全部行平扫及增强扫描,并结合多平面重组、曲面重组等方法显示AAD及穿透溃疡,根据Stan-ford分类法分型。结果:25例AAD,A型7例,B型18例。主要CT表现:主动脉壁呈新月型或环形增厚,无内膜破裂形成的双腔主动脉征象,增强扫描假腔无强化。内膜钙化向内移位7例,穿透性溃疡征3例。并发心包、纵隔及胸腔积液和积血共10例。经内科保守治疗后,6例完全吸收,3例部分不典型吸收,2例无明显变化。结论:螺旋CT清楚显示夹层的部位、范围及并发症,可作为主动脉夹层的首选检查及随访方法。     

Implementation of an aortic dissection CT protocol with clinical decision support aimed at decreasing radiation exposure by reducing routine abdominopelvic imaging

Patients suspected of having an acute aortic syndrome in the ED typically undergo CT of the chest/abdomen/pelvis. However, the overwhelming majority of these exams are negative. With the help of clinical decision support, we implemented a new radiologist monitored ‘aortic dissection screening protocol’ that forgoes routine abdominopelvic imaging in order to reduce radiation dose without compromising diagnostic accuracy. The purpose of the present study is to assess the performance of this protocol. A retrospective analysis was performed to study the effect of the dissection screening protocol on the diagnostic yield, radiation and contrast dose on a total of 835 ED patients who underwent CT scans for suspected aortic dissection over a 48-week study period immediately before and after implementation of the protocol. 3.4% (28/835) of examinations were positive for an acute aortic syndrome over the 48-week study period with no difference in positivity before and after implementation of the ‘aortic dissection screening’ protocol, 3.0% vs. 3.7%, respectively (p = 0.57). There was a 14.6% reduction in median radiation dose and a 16% decrease in contrast volume utilization for the total ED population who underwent CT for aortic dissection using any protocol in the period after implementation of the ‘aortic dissection screening’ protocol. Aortic dissection CT in the ED is negative in the overwhelming majority of cases. A monitored ‘aortic dissection screening’ protocol that initially images the chest only significantly reduced contrast and radiation dose without reducing diagnostic accuracy for ED patients who underwent CT for aortic dissection.     

The value of narrow CT window settings in the recognition of subtle acute aortic intramural haematoma

Four patients with acute aortic intramural haematoma are presented. In all patients the typical crescentic hyperdense rim within the aortic wall was not obvious on unenhanced CT when reviewed on standard mediastinal windows, but the hyperdense crescentic rim was well seen on narrow window settings. The findings suggest that all patients with a typical clinical presentation of acute thoracic aortic dissection who do not have a classical dissection on contrast-enhanced CT or a hyperdense intramural haematoma on standard mediastinal settings, should have the non-contrast scans reviewed on narrow window settings.     

薄层CT平扫对主动脉夹层诊断的价值

目的 探讨薄层CT平扫对主动脉夹层的临床诊断价值。方法 回顾性分析56例疑似主动脉夹层病人,男26例,女30例,平均年龄(55.9±11.2)岁,以CT血管成像(CTA)作为金标准,其中30例确诊为主动脉夹层,26例非主动脉夹层。采用χ2检验对2组间内膜瓣钙化内移、增宽的主动脉密度不均、管腔内线样高密度、主动脉横径增宽这4个主要CT平扫征象及伴随征象的差异进行比较,并对主要征象做诊断准确性分析。结果 主动脉夹层平扫的主要征象包括内膜瓣钙化内移(22例,39.3%)、增宽的主动脉密度不均(44例,78.6%)、腔内线样高密度(31例,55.4%)、主动脉横径局限性或广泛性增宽(36例,64.3%);伴随征象包括主动脉壁钙化(47例,83.9%)、病变累及分支血管管腔增粗(6例,10.7%)、心包积液(11例,19.6%)、胸腔积液(15例,26.8%)。主动脉夹层组的内膜瓣钙化内移和管腔内线样高密度发生率均高于非主动脉夹层组(均P<0.05);其中,内膜瓣钙化内移诊断主动脉夹层的敏感度66.7%,特异度92.3%,准确度78.6%;管腔内线样高密度的敏感度80%,特异度73.1%,准确度76.8%。2组其他CT征象比较差异无统计学意义(P>0.05)。结论 薄层CT平扫对急诊主动脉夹层的诊断具有重要提示意义。     

Synthetic interposition grafts of the thoracic aorta: postoperative appearance on serial CT studies

PURPOSE: To determine the normal postoperative appearance of thoracic aortic interposition grafts on serial CT studies and to document CT detectable complications. MATERIALS AND METHODS: The 235 CT studies in 114 patients with one or more thoracic aortic interposition grafts were analyzed for the presence or absence of felt rings, felt pledgets, low-attenuation material surrounding the graft, pseudoaneurysm, and dissection flap. A graft was present in the ascending aorta in 93 patients, in the descending aorta in 25, and in the arch in 11. RESULTS: Low-attenuation material was seen adjacent to the ascending graft in 55%-82% of patients and adjacent to the descending graft in 60%-79% of patients, showing diminishing frequency and thickness over time. CT scans in 30 of 53 patients showed residual low-attenuation material adjacent to the graft more than 1 year after surgery. CT scans in four of 93 patients with ascending grafts and one of 25 patients with descending grafts showed a pseudoaneurysm. CONCLUSION: CT studies obtained after aortic interposition grafting show characteristic findings. Knowledge of the type of operative procedure and typical location and CT appearance of surgical materials used is important to correctly diagnose or exclude postoperative complications following thoracic aortic interposition grafting.     

Computed tomography of thoracic aortic dissection: accuracy and pitfalls

During a 5 year period, 137 patients with suspected acute aortic dissection were screened by CT. The radiologic diagnosis of dissection was made in 54 cases and eliminated in 76. There were seven false-negative CT examinations. Surgical and angiographic correlations or clinical follow-up were obtained with all patients.