Spiral CT angiography of aortic dissection

Spiral CT angiography (CTA) is one of the newest imaging techniques used for the evaluation of aortic dissection. Current spiral CT scanners with high-performance tubes and subsecond scanning allow increased regions of coverage. Large volumes of data are rapidly acquired through the aorta during maximum contrast enhancement. Multiplanar reformat (MPR), curved planar reformat (CPR), and 3-D rendering techniques including shaded surface display (SSD) and maximum intensity projection (MIP) are then applied to the data to generate CT angiographic images of the aorta. Emergent spiral CTA may be performed in patients with suspected aortic dissection who are hemodynamically stable. Postprocessing is performed immediately following data acquisition and can provide additional information for aortic dissection diagnosis and clinical management. The technique, applications, and limitations of spiral CTA for the evaluation of aortic dissection will be discussed relative to the role of other imaging modalities.     

Diagnostic imaging of aortic diseases

Summary The aim of this overview is the comparison between noninvasive tomographic imaging modalities such as surface echocardiography, transesophageal echocardiography, X-ray computed tomography and magnetic resonance imaging with the previous gold standard angiography in the setting of acute and chronic aortic diseases. Methods: The groundwork for the comparison between various noninvasive modalities is the validation of findings with angiography or intraoperative and histopathological results. Results and conclusions: Noninvasive modalities such as transesophageal echocardiography, X-ray computed tomography and magnetic resonance imaging are suitable methods for reliable diagnosis or exclusion of aortic dissection both in the ascending and descending segment of the thoracic aorta. Other more rare pathologies of the aorta such as intramural hemorrhage as a precursor of dissection, aortic ulcers, aneurysms as well as congenital and posttraumatic lesions may also be subjected to transesophageal echocardiography or magnetic resonance imaging with excellent sensitivity and specificity; both techniques have also proven to be safe procedures in critically ill patients and have, in our view, replaced angiography for the diagnosis of acute aortic syndromes. Thus, in acute aortic diseases invasive angiographic procedures should be relegated to a complementary role, while transesophageal echocardiography, X-ray computed tomography (especially helical CT) in acute, and magnetic resonance imaging in chronic cases represent prefered diagnostic options. In addition to primary diagnostics the noninvasive approaches using transesophageal echocardiography and magnetic resonance imaging are superbly suitable for serial follow-up imaging in all forms of aortic pathology. Eingegangen am 23. Januar 1997 Angenommen am 23. Januar 1997     

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.     

Thoracic aortic disease: Spectrum of multidetector computed tomography imaging findings

The clinical presentation of diseases involving the thoracic aorta ranges from a large number of asymptomatic patients with clinically undetectable thoracic aortic aneurysm to patients with symptoms of severe chest pain as a result of acute aortic dissection. Thoracic aortic disease often remains undiagnosed until a life-threatening complication occurs or the disease is discovered serendipitously on imaging studies performed for other purposes. Multidetector row computed tomography (MDCT) imaging of the aorta is used to diagnose various acute and chronic conditions, including aortic aneurysms, aortic dissection, intramural hematoma, penetrating atherosclerotic ulcer, traumatic injury, rupture, inflammatory disorders, and congenital malformations. This review illustrates the wide range of MDCT imaging findings of thoracic aortic disease.     

Clinical application of single shot GRE-EPI as non-enhanced MRA (EPI-MRA) for aortic aneurysm and dissection

We investigated the usefulness of single shot gradient echo type echo planar imaging (GRE-EPI) as magnetic resonance angiography (MRA) for the diagnosis of aortic aneurysm and dissection. This technique can detect blood flow signals in several tenths of a milliseconds without the need for contrast medium, breath-holding, or electrocardiographic (ECG) gating. By scanning approximately 20 frames in the coronal plane, three-dimensional (3D) imaging can be achieved by maximum intensity projection (MIP) at different angles. Three radiologists evaluated the ability of this single shot GRE-EPI as non-enhanced MRA (EPI-MRA) to diagnose aortic aneurysm and dissection. The examined lesions consisted of three cases of thoracic aortic aneurysm, seven of abdominal aortic aneurysm and eight of aortic dissection with a total of 15 involved aorta. In all patients with aortic aneurysm, EPI enabled detection and diagnosis of the aneurysm. However, the size of the lesion and relationship with major branches were determined only in the abdominal aorta, and could not be determined precisely in thoracic lesions. Similar results were obtained for patients with aortic dissection. The technique visualized the intimal flap and enabled determination of the extent of dissection in the abdominal aorta. In the thoracic aorta, serious magnetic susceptibility artifacts caused image distortion, and as a result only the dissection could be detected and diagnosed. No entry site was detected at either the abdominal or thoracic aorta. These results suggest that EPI-MRA may have a clinical potential for screening patients with acute aortic disease who cannot undergo physical restraint for scanning.     

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.     

Complex thoracic aortic dissection treated by aorto-biiliac bypass and juxta-renal removal of aortic fenestrations

Thoracic aortic dissections are a life-threatening pathology. They occur when there is an intimal tear causing separation of the layers of the aorta. Thoracic aortic dissections can be acute or chronic and depending on the pattern of the dissection can be difficult to treat. No acute dissections are the same, and herein we describe a case of a 62-male presenting with an acute thoracic aortic dissection requiring acute aorto-biiliac bypass and juxta-renal removal of aortic fenestrations.     

Streak artefacts of the thoracic aorta: pseudodissection

Streak artefacts running across images of the aorta can mimic aortic dissection on CT. We have compared 12 patients suffering from dissection with 45 others. Some artefacts were found in every patient. Such misleading appearances were more obtrusive in dissectors. However, we have found several pointers that help distinguish true intimal flaps from artefacts. Flaps are usually thin structures showing mild curvature. Artefacts are generally linear and vary in thickness. Their orientation may change markedly from one CT section to the next; they frequently extend beyond the confines of the aorta. In the ascending aorta, artefacts usually run at an angle of approximately 66 degrees to the coronal plane; especial care should be taken before diagnosing a straight intimal flap in that orientation. Careful study of images on the monitor rather than on film is a further help in the important distinction between artefact and intimal flap.     

主动脉不典型夹层的电子束CT诊断

目的 评价电子束CT（EBCT）在主动脉不典型夹层诊断中的临床应用。方法 1994年5月至2000年4月15000例EBCT检查中诊断主动脉夹层263例,其中25例为不典型夹层。男21例,女4例。全部患者均以主诉急性胸痛入院检查。采用Imatron 150-XP型EBCT扫描机,连续容积增强扫描,层厚3mm,扫描时间为0．1s。扫描范围自主动脉弓水平至左右髂动脉分叉处,共140层。结果 不典型夹层EBCT血管造影（EBCTA）：直接征象为:(1)25例主动脉壁均呈半月状或环状增厚,达5－23mm,平均15．3mm,无内膜破裂形成的双腔主动脉征象,CT值50－87HU,累及长度为2．5－49．0cm,平均16．3cm;（2）内膜钙化移位5例;（3）6例治疗后EBCT随访,管壁厚度呈动态变化。间接征象为：（1）主动脉壁增厚溃疡形成7例;（2）动脉粥样硬化性改变12例。上述征象结合临床急性胸痛病史,诊断可以成立。病变累及升主动脉（StanfordA型）6例;仅累及降主动脉（StanfordB型）19例。全部病例临床均采取保守治疗,其中6例EBCT复查,3个月至1年血肿吸收。结论 急诊胸痛鉴别诊断中EBCT对主动脉不典型夹层诊断是一种无创、安全、有效的诊断方法,且便于治疗后随诊观察。     

Acute non-opacified dissection of the ascending thoracic aorta--significance of retrograde dissection and re-dissection]

Thirteen cases of acute aortic dissection with non-opacified false lumen of the ascending aorta were examined by CT and other imaging modalities. On the basis of the initial CT findings, these cases were classified into two types; one was pure non-opacified dissection not associated with opacified false lumen (Type N, n = 7), the other was non-opacified dissection of the ascending aorta associated with opacified false lumen of the following aorta (Type N+O, n = 6). On examining the relation between the entry site and the false lumen in Type N+O, the dissection of the ascending aorta was considered to be retrograde. Retrograde dissection seemed to be an important factor in the development of the non-opacified dissection of the ascending aorta. During the follow-up period, re-dissection in the ascending aorta occurred in four of the 13 cases (Type N = 3, Type N+O = 1). The re-dissection occurred within the first four weeks in all of them, and the diagnosis of re-dissection was possible at its early stage. In one case, ulcerlike projection (ULP) was detected by aortography. In another case, ULP was identified by cine-MR imaging. Contrast CT also revealed enlargement and small opacification of the false lumen. In two other cases, similar CT findings were observed. Three of the four patients recovered by surgical treatment. One died the day after the diagnosis of re-dissection. Early diagnosis and earliest possible surgical intervention for re-dissection were considered necessary to save the patients with re-dissected false lumen in the ascending aorta. Close observations with several imaging modalities, mainly CT examination, should be paid in the patients with non-opacified dissection of the ascending aorta for at least four weeks after the onset of dissection.     

CT of acute abdominal aortic disorders

Aortic aneurysm rupture, aortic dissection, PAU, acute aortic occlusion, traumatic aortic injury, and aortic fistula represent acute abdominal aortic conditions. Because of its speed and proximity to the emergency department, helical CT is the imaging test of choice for these conditions. MR imaging also plays an important role in the imaging of aortic dissection and PAU, particularly when the patient is unable to receive intravenous contrast material. In this era of MDCT, conventional angiography is used as a secondary diagnostic tool to clarify equivocal findings on cross-sectional imaging. Ultrasound is helpful when CT is not readily available and the patient is unable or too unstable to undergo MR imaging.     

Fatal Delayed Esophageal Rupture Following Aortic Clamping for Treatment of Stanford Type B Dissection

A 65-year-old man underwent a thromboexclusion operation for management of chronic Stanford type B dissecting aneurysm in 1991. However, long-term follow-up CT scans after the operation revealed that the ascending aorta gradually enlarged and was eventually complicated by recurrent aortic dissection. The patient complained of frequent bloody sputum, whereas chest roentogenography showed no pulmonary abnormalities. Subsequent swallow esophagogram demonstrated that the upper esophagus was deviated to the right and the middle esophagus was greatly compressed by the aortic clamp. Esophageal endoscopy showed a bloody inner surface and marked swelling of the middle esophagus. The patient eventually died of massive hematemesis in 2001. We describe the imaging features of unanticipated complications such as recurrent dissecting aneurysm or impending esophageal rupture. Furthermore, we discuss the cause of hematemesis and document that the aortic clamp migrated and resulted in development of a recurrent aneurysmal dissection, which in turn resulted in esophageal rupture with aneurysmal disruption.     

Penetrating atherosclerotic ulcers of the descending thoracic aorta: evaluation with CT and distinction from aortic dissection.

Penetrating atherosclerotic ulceration of the aorta is a poorly understood entity that clinically mimics classic aortic dissection but has imaging features that are distinctly different. In a review of 16 patients with penetrating atherosclerotic ulceration, patients were typically hypertensive (n = 14), and they experienced chest or back pain (n = 13). All patients had an abnormal chest radiograph, with diffuse (n = 14) or focal (n = 2) enlargement of the descending thoracic aorta. Features at contrast material-enhanced computed tomography (CT) included intramural hematoma (n = 16), focal ulcer (n = 15), displaced intimal calcification (n = 13), pleural and/or extrapleural fluid (n = 7), mediastinal fluid (n = 4), and a thick or enhancing aortic wall (n = 6). The chest radiograph and CT findings were compared in patients treated conservatively (n = 9) and surgically (n = 7). These findings did not correlate with the need for surgery. Eight of nine conservatively treated patients were asymptomatic after treatment with antihypertensive medication. Contiguous dynamic contrast-enhanced CT of the aorta enables distinction of ulceration from dissection, which is particularly important in the hemodynamically unstable patient because the surgical management of ulceration is more extensive than that for aortic dissection.     

Acute aortic abnormalities

Aneurysm and type B dissections account for most acute abdominal aortic abnormalities. The postsurgical aorta deserves special attention owing to the risk of complications. Most aortic abnormalities presenting acutely are emergencies that carry a high risk of mortality, and imaging plays a critical role in patient evaluation. Modern helical CT scanners provide excellent spatial resolution, are readily available, and allow for rapid imaging. For these reasons, helical CT angiography is the imaging modality of choice for initial evaluation of the acute aorta.     

Acute and chronic complications of aortic intramural hematoma on follow-up computed tomography: incidence and predictor analysis

OBJECTIVE: To ascertain the incidence of acute and chronic complications of aortic intramural hematoma (IMH) and to analyze the predictors of the development of each complication. MATERIALS AND METHODS: This retrospective study includes 107 consecutive patients diagnosed with aortic IMH by means of computed tomography (CT) during the period from January 1998 to December 2003 and followed up with serial CT examinations (median follow-up period, 320 days). There were 36 patients with type A and 71 with type B IMH. Initial and follow-up CT scans were reviewed, with special attention given to the development of complications, such as increase in the thickness of IMH, clinical and hemodynamic evolution requiring urgent surgery, and development of aortic dissection and/or aneurysm. If each complication developed within 30 days after the initial episode, we classified it as an acute complication; the others were classified as chronic complications. The time interval between the initial and the subsequent CT examination showing each complication was recorded. To identify the predictors of each complication, we analyzed the demographic and CT findings with regard to the following factors: age, sex, maximum thickness of the hematoma, maximum aortic diameter on initial CT examination, ulcerlike projection (ULP) on initial and follow-up CT examinations, and the degree of atherosclerosis. The Cox proportional hazards regression model with stepwise multivariate analyses was used to determine the significant predictors of each complication. RESULTS: Sixteen patients had acute complications consisting of aortic dissection (n = 7), aortic aneurysm (n = 6), and acute clinical and hemodynamic evolution requiring operation (n = 3). Three additional patients with aortic dissection (n = 1) and aneurysm (n = 2) underwent emergency surgery. Twenty-three patients with chronic complications had aortic dissection (n = 3), and aortic aneurysm (n = 20). Cox proportional hazards regression model revealed that the maximal diameter of involved aorta is the only significant predictor of the development of acute complications (P = 0.006), whereas the age (P = 0.040), type A IMH (P = 0.015), presence of ULP (P = 0.015), and newly developed ULP as revealed on follow-up CT examination (P = 0.032) were significant predictors of the development of chronic complications. With regard to the aortic dissection in 10 patients (9.3%; type A/B ratio, 5:5; median time interval, 34 days), Cox proportional hazards regression model revealed that the maximal thickness of the hematoma is the only significant predictor (P = 0.018). Twenty-one saccular and 5 fusiform aneurysms (24.3%) developed, as revealed on follow-up CT examinations (median time interval, 180 days). The presence of ULP (P = 0.030), type A (P = 0.038) and the maximal thickness of the hematoma (P = 0.017) were significant predictors for the development of an aneurysm. CONCLUSIONS: The maximum thickness of a hematoma on the initial CT is the significant factor predicting the development of aortic dissection and aortic aneurysm. Patients with type A IMH and ULP, as revealed by initial and short-term follow-up CT examinations, should be carefully followed up with subsequent CT examination to monitor the development of an aortic aneurysm, which is a relatively common chronic complication of IMH.     

带膜支架腔内置入术治疗急性胸腹主动脉夹层

目的 :探讨带膜支架腔内置入术治疗急性胸腹主动脉夹层的应用和疗效。方法 :对 1例急性胸腹主动脉多发破口的主动脉夹层采用带膜支架置入治疗 ,并分析其疗效。结果 :经股动脉置入两枚带膜支架封闭破口成功 ,术后复查彩超和多层螺旋CT示主动脉夹层消失 ,假腔内血栓形成 ,未出现支架移位、狭窄等并发症。结论 :带膜支架腔内置入术是治疗主动脉夹层的有效方法。     

64层螺旋CT诊断血管性病变急腹症的临床价值分析

目的：探讨血管性病变导致急性腹痛的64层螺旋C T诊断价值。方法分析38例血管源性急腹症平扫及增强CT ,分析CT表现。结果内脏动脉瘤合并出血6例;腹主动脉及右侧髂总动脉瘤合并出血3例;腹主动脉分支夹层7例;肠系膜上动静脉扭转3例;肠系膜上动静脉栓塞及血栓形成14例;肾动脉栓塞5例。结论通过64层螺旋C T平扫及增强扫描,腹部血管性病变能清晰显示其病因、病变范围及其继发改变,达到诊断明确,所以腹痛疑诊为血管性病变时,CTA应作为影像学的首选检查方法。     

Multidetector-row CT evaluation of nontraumatic acute thoracic aortic syndromes

Acute thoracic aortic syndromes encompass a spectrum of emergencies presenting with acute chest pain and marked by a high risk of aortic rupture and sudden death. These include nontraumatic disease entities of the thoracic aorta, namely, dissection, intramural haematoma, penetrating atherosclerotic ulcer and aneurysm rupture. In clinical practice, the most frequent imaging procedure used in the diagnostic assessment of these diseases is computed tomography (CT), which, thanks to recent technological developments [multidetector-row computed tomography (MDCT)], affords important diagnostic possibilities and very interesting future perspectives. This paper on the use of MDCT in the evaluation of acute thoracic nontraumatic aortic syndromes illustrates the examination technique and the key imaging findings related to each disease. Moreover, the role of MDCT for planning specific treatment is also highlighted.     

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。     

Aorta-cameral fistulas: Spectrum of CT findings and review

Aorto-cameral fistula (ACF) is an uncommon entity, defined as an abnormal communication between the aorta and a cardiac chamber. The most common causes include ruptured sinus of Valsalva aneurysm, infective endocarditis, traumatic injury, aortic dissection, or rarely can be iatrogenic in nature. While smaller communications may initially be asymptomatic, the natural course of these connections is generally refractory heart failure as they do not spontaneously heal. Larger fistulas can be life threatening with high mortality rates, and therefore once recognized, surgery is generally considered the treatment of choice. Diagnosis, however, can be challenging, and various imaging modalities are often used for diagnosis. This review highlights common underlying etiologies, clinical manifestations, and radiologic imaging appearances of ACF to each of the cardiac chambers of this uncommon, but clinically important entity, with emphasis on CT.