Magnetic resonance imaging of aortic aneurysm

Magnetic resonance (MR) imaging in 16 patients with aortic aneurysm used a field of 5,000 Gauss and spin echo multisection imaging with two echos. Results were compared retrospectively with those of echotomography, computed tomography and angiography. Surgical exploration allowed correlation with histopathology in 13 patients. The external diameter of aneurysm and of its residual lumen and length of aneurysm were in each case evaluated precisely by MR. In patients with abdominal aneurysm, MR images identified the limits of the aneurysm in relation to renal and iliac arteries. In aneurysms of thoracic aorta, synchronization of signal with an ECG and longitudinal imaging provided data on relations of aneurysm with supraaortic trunks. In 2 patients with extensive, partially thrombosed thoracic and abdominal aorta aneurysm, MR imaging could not eliminate a diagnosis of aortic dissection with thrombosed false lumen. Finally, aortic wall calcifications were never apparent on MR images.     

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。     

Thoracic aortic dissections: magnetic resonance imaging

Six patients with documented dissections of the thoracic aorta (two Type A, four Type B) were examined by magnetic resonance (MR) imaging using a 0.6-Tesla superconductive magnet. Cardiac gating was applied in five cases. Correlation was made with CT and angiography. MR imaging demonstrated the dissection in all six cases and accurately differentiated Type A from Type B dissections. Coronal and sagittal MR sections were advantageous in establishing the relationship of the three arch vessels to the dissection. In addition, cardiac-gated MR was useful in demonstrating mural thrombus and in distinguishing the true from the false lumen based on differences in signal intensity resulting from different flow rates. In five cases, the information obtained by MR was equal to or surpassed that obtained by CT. In the one case of a completely thrombosed dissection, the CT scan was more helpful. MR should become an important imaging modality in the evaluation of aortic dissections.     

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.     

Aortic dissection: magnetic resonance imaging

Fifteen patients with suspected or known aortic dissection were imaged with magnetic resonance (MR). Thirteen of these patients were eventually shown to have dissection. In most instances the diagnosis was established by aortography and/or computed tomography (CT) prior to the MR study. Surgical proof (6/13) and/or aortographic proof (10/13) were available in 11/13 patients with aortic dissection. MR demonstrated the intimal flap and determined whether the dissection was type A or type B. In addition, MR: differentiated between the true and false lumens; determined the origins of the celiac, superior mesenteric, and renal arteries from the true or false lumen in the cases where the dissection extended into the abdominal aorta (8/12); allowed post-surgical surveillance of the dissection; and identified aortoannular ectasia in the three patients who had Marfan syndrome. In addition to the 13 cases with dissection, there were two cases in whom the diagnosis of dissection was excluded by MR. Our early experience suggests that MR can serve as the initial imaging test in clinically suspected cases of aortic dissection and that the information provided by MR is sufficient to manage many cases. Additionally, MR obviates the use of iodinated contrast media.     

Clinical assessment of rotational digital angiography for the diagnosis of aortic dissection

Rotational digital angiography was performed in five patients with aortic dissection. Intimal tears, intimal flap and involvement of major branches were clearly demonstrated in two patients with opacified false lumen. Ulcer-like projections were also identified in three patients with thrombosed false lumen. The device has, therefore, been found to be of great value in diagnosing aortic dissection particularly for the detection of intimal tear sites and ulcer-like projections.     

64层螺旋CT对主动脉夹层的应用价值

目的:探讨64层螺旋CT诊断主动脉夹层的临床价值。方法:39例拟诊为主动脉病变的患者作为本组研究对象,对所有患者行CT平扫及增强扫描。CT平扫图像上观察内膜钙化的移位、主动脉直径扩大、心包和/或纵隔积血、胸腔积液/血。并对A型和B型主动脉夹层的平扫征象进行统计学比较。CT增强图像上观察低密度的内膜瓣、破口(入口和再入口)、真假腔及主要动脉分支受累情况。结果:21例主动脉夹层中,CT平扫观察到钙化的内膜瓣移位9例(42.9%),主动脉直径增宽8例(38.1%),心包和/或纵隔积血8例(38.1%),胸腔积液/血5例(19.0%)。CT增强扫描对主动脉夹层内膜瓣的显示率达100%(21/21),对真、假腔的显示率为100%(21/21),对破口的显示率为85.7%(18/21)。8例(38.1%)弓上血管受累,5例(19.0%)内脏血管受累。结论:64层螺旋CT对主动脉夹层有较高的诊断价值,能较好的显示夹层的真假腔、内膜瓣及破口,并且可以显示主要动脉受累情况,为外科的手术治疗提供重要信息。     

Aortic dissection: atypical patterns seen at MR imaging

Aortic dissection is typically manifested by an intimal flap separating true and false lumens. Atypical patterns lacking an intimal flap can occur, however, and are less well recognized. In this study, the authors review their experience with atypical patterns at magnetic resonance (MR) imaging. They evaluated the T1-weighted and gradient-echo MR images of the entire aorta in 64 patients with aortic dissection. In nine patients (14%) aortic wall thickening was the only sign of dissection in the thorax. In three of these cases, an intimal flap was found in the abdominal aorta; the other six patients had no flap in any region of the aorta, and this led to false-negative angiographic results in three cases. Aortic wall thickening as an atypical sign of dissection was seen more frequently in acute (29%) than in chronic (7%) dissection and was seen in only patients without Marfan syndrome. Two patients with atypical acute dissection at initial examination developed a clearly identifiable intimal flap at follow-up. Aortic wall thickening may represent the only sign of aortic dissection. In some cases, imaging the entire aorta can enable recognition of dissection in atypical cases.     

Differentiation between dissection and a true aneurysm of the descending thoracic aorta using magnetic resonance tomography

The case reviewed here demonstrates that magnetic resonance imaging in contrast to CT and i.v. DSA can differentiate between aortic dissection with partially thrombosed false lumen and a true aneurysm using the spin-echo and the gradient-echo technique. The gradient-echo technique was able to depict the moving intimal flap as well as the higher blood flow velocity in the true lumen.     

CT virtual angioscopy in the study of thoracic aortic dissection]

PURPOSE: Virtual endoscopy is a technique in which helical-CT and MR data sets are processed by a special software creating a three-dimensional viewing of the inner surface of hollow viscera that simulates the endoscopic view. We report our 2.5-year experience with virtual intraluminal endoscopy (VIE) in the study of the thoracic aorta in patients with aortic dissection and in patients with normal aorta. MATERIAL AND METHODS: From December 1997 to June 2000, CT angiography (CTA) data sets of the thoracic aorta obtained in a series of 43 patients were retrospectively evaluated. Our series included 23 patients with clinical or radiological suspicion of aortic dissection and 20 patients in whom the study of the thoracic aorta was carried out as a necessary completion of an abdominal aortic disease. CTA data sets were processed with a dedicated software (Navigator); the view point and view direction could be set arbitrarily in the vessel, obtaining an intraluminal endoscopic view of the inner surface of the vessel. Multiple views were obtained and visualised consecutively through a cine-loop technique. The entire thoracic aorta was studied. RESULTS: VIE enabled correct visualisation of the intimal flap in all cases of aortic dissection (=23) and of its origin at the level of the ascending aorta in 16 cases (Stanford A) and in the descending aorta in the remaining 7 patients (Stanford B). In the control group (=20) no signs of intimal flap were identified with the VIE. In all patients with aortic dissection false and true lumen were entirely visualised. VIE allowed the understanding of the relation between false lumen and supraaortic vessels that originated from the true lumen in all cases and were found to be dissected in 6 patients. In 16 cases the dissection included thoracic and abdominal aorta. In some cases the endoscopic view was altered by artifacts related to the selected threshold levels and represented by pierced surface and floating shape artifacts. A correlation with axial and multiplanar (MPR) images allowed the correct interpretation of such artifacts. CONCLUSIONS: According to our experience, virtual endoscopy represents a useful tool in the evaluation of the dissection of the thoracic aorta, allowing a better definition of anatomical details. A correlation with axial images and multiplanar views remains compulsory for a better understanding of VIE findings, which is nevertheless significantly influenced by the operator's experience.     

Cine-MR in dissection of the thoracic aorta

Magnetic resonance imaging (MRI) of the thoracic aorta, including cine-MRI, was performed in 25 patients suspected of having dissection of the thoracic aorta. MRI was correlated with echocardiography, CT and angiography. The sensitivity of MRI (100%) was most closely followed by CT and angiography (83% and 77% respectively). The specificity of MRI and angiography was equally good, at 100% each. MRI was able to demonstrate the intimal flap in all 9 cases of aortic dissection, and there were no false-positive results. Differentiation of thrombosis and slow flow was possible on proton density images, gradient echo images permitted detection of the entry and re-entry sites. The nature of the dissection was determinated correctly in 8 out of 9 cases. MRI is capable of providing all the relevant parameters necessary to decide appropriate treatment of dissecting aneurysms of the thoracic aorta.     

外伤性主动脉夹层的CT诊断(附2例报告)

目的：探讨外伤性主动脉夹层的早期CT表现。方法：回顾性分析在我院漏诊及确诊的外伤性主动脉夹层的CT表现。2例中1例行3次CT平扫,1例行CT平扫和增强扫描。结果：2例均为DeBakeyIU型主动脉夹层,1例3次CT平扫示降主动脉管腔进行性增宽,伴双侧胸腔积液;此例因漏诊,患者于2周后死亡。另1例CT平扫示降主动脉增粗,CT增强扫描明确诊断,主要表现为降主动脉扩张,可见真腔、假腔及内膜线;此例患者行支架植入术后,患者预后良好。结论：对于胸部外伤患者,CT平扫时应注意观察主动脉的直径,如果降主动脉增粗、尤其是进行性增粗时,应考虑主动脉夹层的可能。     

MR imaging of the aorta after surgery for aortic dissection

MR imaging is known to be an effective technique for the noninvasive diagnosis of thoracic aortic disease, but it has not been used to monitor the appearance of the aorta or the fate of the false lumen after surgery for aortic dissection. This study describes our initial experience with postsurgical MR imaging of aortic dissection (nine type A and two type B) to evaluate prognostically important features, including the status of residual false lumen. The most notable findings were (1) aneurysmal dilatation beyond the interposed graft (11/11 cases), (2) residual intimal flap (10/11 cases) with at least partial patency of the false lumen (10/10 cases), and (3) origin of a visceral vessel from the false lumen in persistently dissected abdominal aorta (6/9 cases). Evaluation of residual false lumen by double-spin-echo-intensity and phase-display techniques showed evidence of slow blood flow with variable amounts of thrombus in eight of 10 cases. Differentiation between signal within the false lumen due to slow flow and signal due to thrombus was facilitated by phase display. MR imaging can be used for noninvasive monitoring of the aorta after surgical repair of aortic dissection. Since the false lumen usually remains patent after surgical repair, such follow-up of its status seems necessary for identifying potential complications of the original dissection and/or the therapy.     

64层螺旋CT血管成像在主动脉夹层诊断中的临床价值

目的:探讨64层螺旋CT血管成像(CTA)在主动脉夹层(AD)诊断及术前评价中的应用价值。方法:58例连续性AD患者行64层螺旋CTA,对所有数据进行MPR、MIP、VR等重建分析。结果:CTA结果显示依据DeBakey分类法,Ⅰ型夹层14例,Ⅱ型2例,Ⅲ型42例。所有患者均存在明确的撕裂内膜片及真假腔,动脉期真腔平均CT值较假腔高,差异有统计学意义(P=0.000<0.05)。所有患者均明确显示了初始破口的位置,55例显示了一个或多个再破口,3例Ⅲ型患者未显示再破口。39例Ⅲ型患者初始破口位于主动脉弓降部或降胸主动脉近端,其近端瘤颈长度、宽度分别为0.4～10.8cm(平均3.5cm)、2.2～3.6cm(平均2.8cm),瘤体最大径为3.2～9.2cm(平均5.4cm)。图像准确显示了所有患者主动脉重要分支受累以及假腔内血栓形成情况。结论:64层螺旋CT血管成像具有无创、快速、准确性高等优点,是主动脉夹层诊断及术前评价的可靠影像学检查方法之一。     

主动脉病变螺旋CT三维成像的临床应用

目的　探讨螺旋CT在主动脉疾病诊断中的临床应用及其价值。　材料与方法　22例主动脉疾病（11例主动脉瘤、1例胸主动脉假性动脉瘤、7例主动脉夹层动脉瘤、1例大动脉炎、2例主动脉缩窄）者行螺旋CT增强检查,以表面覆盖显示(SSD)、多平面重建(MPR)、最大密度投影(MIP)、血管CT仿真内窥镜成像(CTVE)等多种方式重建。　结果　SSD均能很好显示病变的全貌,动脉瘤的大小、范围,夹层内膜片及与分支血管的关系等;MPR可较好显示附壁血栓,真假腔和内膜片;MIP可清楚显示管壁钙化和动脉瘤形态;CTVE可清晰显示内膜片、真假腔及血管的狭窄。　结论　诊断主动脉疾病综合应用螺旋CT的各种技术可基本取代X线血管造影,其为临床提供了一种可靠的诊断手段。     

Pitfalls in diagnosis of aortic dissection by angiography: Algorithmic approach utilizing CT and MRI

Dissection of the thoracic aorta is a life-threatening event requiring imaging studies to define the level of the tear and the intinmal flap. The “gold standard” has been angiography. This method may fail to demonstrate the dissection, however, due to overlap of the true and false lumens or a very thin flap that is imaged en face rather than tangentially. Computed tomography has a diagnostic accuracy of 95%, but can fail to image the dissection due to technical factors or a thrombosed false hunen. Magnetic resonance imaging requires a hemodynamically stable and cooperative patient. A diagnostic algorithm is proposed for diagnosis of aortic dissection based on renal function and the surgeon's imaging modality preference.     

特殊类型主动脉夹层的电子束CT表现及诊断

目的探讨表现特殊的主动脉夹层的电子束CT(EBCT)影像特征及诊断.材料和方法20例表现特殊的主动脉夹层,其中不典型夹层13例,三腔以上夹层动脉瘤3例,合并升主动脉壁内血肿的Stanford B型夹层2例,动脉瘤样夹层1例,外伤性主动脉夹层1例.结果主动脉不典型夹层为主动脉壁新月形或环形的低密度血肿包绕,常可见穿透性溃疡或钙化内移等征象;三腔以上夹层动脉瘤有2～3个内膜片,3～4个腔,瘤体管径较大;合并升主动脉壁内血肿的B型夹层见升主动脉管壁低密度新月形或环形增厚,降主动脉则见内膜片及真假两腔形成;动脉瘤样主动脉夹层见降主动脉局限性瘤样扩张,破口大,内膜片不易发现.1例外伤性夹层于主动脉弓峡部及降部起始见破裂内膜片.结论特殊类型的主动脉夹层表现各具特征,EBCT可清晰显示,是极适用于胸部急症的快速、无创的检查方法.     

MRI和螺旋CT对主动脉夹层的对比研究及其临床应用

目的对比分析磁共振成像(MR I)和螺旋CT诊断主动脉夹层(AD)的影像特征,评价2种技术对临床的应用价值。方法回顾性分析经手术或临床证实的18例AD的MR I和螺旋CT表现。结果2种先进检查技术诊断AD的敏感性和特异性均较高,能不同程度地显示AD的范围及其分型、真假腔、内膜片和内膜破口、附壁血栓和壁内血肿、主动脉的扩张和狭窄及其分支血管受累情况。结论对疑有AD者应行MR I或螺旋CT检查,MR I与CT对病变范围及分型、真假腔及主动脉的狭窄和扩张的显示相似;而内膜片、内膜破口、附壁血栓和壁内血肿、主动脉整体及分支受累的显示MR I明显优于螺旋CT;对内膜及主动脉壁钙化、急危重者的检查螺旋CT优于MR I。     

大螺距双源CT在急性主动脉夹层诊断中的应用

目的：探讨大螺距双源 CT 低剂量血管造影技术在急性主动脉夹层(AAD)诊断中的应用价值。方法对21例疑似主动脉夹层的危重患者,采用第2代双源 CT Flash 技术(螺距3.2,100 kV,100 mAs),使用较低的对比剂量(60 mL),在不使用心电门控状态下行全主动脉造影检查。结果所有受检患者均在接受了尽可能低的辐射剂量及碘摄入量的同时,获得了准确的,包括主动脉内膜破口的位置、内膜片、真假腔及病变累及的范围等血管征象及解剖关系信息,Stanford A 型2例,B 型19例,2例主动脉破裂。平均扫描时间2.6 s,平均有效辐射剂量270 mGy·cm。结论大螺距双源 CT 低剂量血管造影技术配合低对比剂量,能快速获得满足诊断要求的优质图像,为全身重度复合伤的危重患者是否合并主动脉夹层提供了安全、可靠、即时的筛查方法。     

Thrombosis of the false lumen in acute aortic dissection. CT diagnosis

Three cases are reported of acute aortic dissection with complete thrombosis of the false channel, which is a very uncommon event in De Bakey's I and II type aortic dissections. The 3 patients entered hospital because of severe thoracic pain without any ECG sign of myocardial infarction. Emergency CT showed evidence of pericardial effusion suggesting hemopericardium, enlargement of the ascending aorta and a peripheral semilunar filling defect which caused a slight deformation of the true channel. On precontrast scans, only one case showed inward displacement of peripheral intimal calcifications and high-density aortic wall. No typical signs of aortic dissection were reported, except in the first patient--where a double contrast filled lumen, separated by an intimal flap was seen. CT findings are individually discussed. It is emphasized that in all patients more than one CT sign was present at a time. The correct evaluation of these signs together with the clinical data could lead to the right diagnosis of aortic dissection in spite of the lack of a filled false channel.