Magnetic resonance imaging of congenital abnormalities of the thoracic aorta

This article outlines the ability of MR imaging in the detection and presurgical evaluation of congenital abnormalities of the thoracic aorta (CATA). Congenital abnormalities of the thoracic aorta may be found incidentally on chest radiographs in patients without symptoms, or it can be associated with clinical findings which are very variable depending on the association with congenital cardiac malformations or vascular ring. When CATA is suspected as the cause of anomalies in the mediastinum in asymptomatic patients, confirmation of the abnormality should be by MR imaging allowing precise evaluation of the thoracic aorta and origin of the principal arteries. When CATA is considered because clinical findings indicate coarctation of the aorta, vascular ring or associated cardiac disorder, evaluation with ultrasound can be complemented by MR, which in most cases will replace the diagnostic catheterization. Received 2 April 1997; Revision received 14 July 1997; Accepted 12 September 1997     

Urgent thoracic aortal dissection and aneurysm: treatment with stent-graft implantation in an angiographic suite

The aim of this study was to evaluate the feasibility of endoluminal stent-graft placement in an angiographic suite for the treatment of emergent type-B aortic dissections and ruptured thoracic aortal aneurysms. Twenty-six patients with either urgent type-B dissection (n=8) or aneurysms (n=18) of the descending thoracic aorta were chosen for stent-graft implantation. All patients received a multidetector-row CT angiography of the whole aorta and pelvic arteries prior to stent-graft implantation. All procedures were performed in a fully equipped digital subtraction angiography (DSA) suite under general anesthesia. In 20 patients Talent LPS tube grafts and in 4 patients an Excluder graft were used. Access was achieved via surgical cut-down in the left (n=7) or right (n=19) groin. Sealing was successful in 24 patients. The proximal covered portion of the stent graft was placed across the left subclavian artery in 2 patients. Procedural success was achieved in 23 of 24 patients. One patient required a second stent-graft placement before the aneurysm was sealed. One patient with an acute perforation of the descending aorta died due to cardiac failure prior to stent-graft implantation. In 1 patient stent-graft delivery failed due to severe calcification of both common iliac arteries. Endoluminal treatment of both urgent type-B aortic dissections and thoracic aortal aneurysms with stent graft is an attractive alternative treatment to surgical repair. The placement of stent grafts in an angiographic suite is a safe and feasible method with good clinical effectiveness and, so far, good clinical outcome.     

Unusual vascular complications of dissecting thoracic aortic aneurysms

Nondissecting, chronic, thoracic aortic aneurysms (TAA) may be associated with such vascular complications as aorto-cardiac, aorto-superior vena caval (SVC) and aorto-pulmonary arterial (PA) fistula formation, and/or SVC or PA compression. Dissecting TAA have been associated with these lesions far less often. This report summarizes the occurrence and outcome of the following complications of dissecting TAA: (1) SVC obstruction; (2) aortoright and-left atrial, aorta-right ventricular and aorto-PA fistula formation; (3) compression of the PA and (4) hematoma of the interatrial septum. Two patients are described with aortic dissection complicated by: (1) SVC obstruction and aorto-left atrial fistula; and (2) aorto-PA fistula. These complicttions are rarer with aortic dissection, because of the acute, catastrophic nature of this lesion. When dissection is chronic, however, arteriovenous fistulae are often well tolerated, and urgent surgical intervention seems to be unnecessary.     

Follow-up of patients with previous treatment for coarctation of the thoracic aorta: comparison between contrast-enhanced MR angiography and fast spin-echo MR imaging

Regular follow-up is required in patients with previous intervention for coarctation of the aorta to detect recoarctation or aneurysm formation. In this study we describe the findings encountered on routine follow-up exams and we compare the use of contrast-enhanced 3D MR angiography (CE MRA) with fast spin-echo MRI (FSE) to study the thoracic aorta after previous intervention. In 51 consecutive patients previously treated for aortic coarctation, 74 MR studies of the thoracic aorta were performed during a 2-year period using CE MRA and FSE MRI. The thoracic aorta was evaluated for abnormalities of course, caliber, shape, and pathology of side branches. The CE MRA and FSE MRI studies were evaluated side by side by consensus of two reviewers evaluating which MR technique depicted the abnormalities of the thoracic aorta the best. Of 74 exams, six clinically important abnormalities were found: four aneurysms and two restenoses. Two small pseudoaneurysms were missed on the FSE studies. Contrast-enhanced MRA was judged to visualize aortic abnormalities better than FSE (47 of 74 MR studies) especially for the transverse aortic arch, coarctation site, left subclavian artery, and aortic arch configuration. For the ascending aorta and distal descending aorta, CE MRA and FSE performed equally well. Aortic diameters measured at four levels in the first 18 MRI studies showed no significant differences in diameter when measured by FSE or CE MRA (p = not significant). Clinically important abnormalities, such as aneurysm formation and restenosis, can be present years after treatment for aortic coarctation. In the regular follow-up of these patients, CE MRA may provide additional diagnostic information compared with FSE and should be included as part of the routine exam. Received: 3 April 2000; Revised: 5 July 2000; Accepted: 7 July 2000     

Mice with a deletion in the first intron of the Col1a1 gene develop dissection and rupture of aorta in the absence of aneurysms: high-resolution magnetic resonance imaging, at 4.7 T, of the aorta and cerebral arteries.

Deletion of the majority of the first intron of the Col1a1 gene in mice leads to decreased type I collagen synthesis and content in the aortic wall. In 54% of cases, mice homozygous for the Col1a1 mutation die of thoracic hemorrhage by the age of 18 months. It is unknown whether the fatal bleeding results from an acute dissection of the aortic wall or a gradually developing dilatation of the medial layer prior to rupture. We optimized high-resolution MRI methods using a 4.7 T MR scanner to obtain in vivo images of the entire mouse aorta. The MR images were acquired in three imaging planes using gradient echo, spin echo, and spin echo with inversion recovery pulse sequences with a maximum in-plane resolution of 68 x 68 microm and acquisition times less than 10 min. In five Col1a1 mutated mice aged 16 months, the MR images showed no signs of aneurysmal dilatation, wall defects, or former dissection, suggesting that the mechanism for aortic rupture is an acute dissection of the aortic medial layer. Cerebral arteries were imaged using a three-dimensional time of fight pulse sequence. The resolution of 73 x 73 x 94 microm showed normal cerebral arteries. Histology showed a 22% thinner cerebral artery wall in Col1a1 mutated mice.     

胸主动脉供血与腹主动脉供血肺隔离症的对比分析

目的：对比分析胸主动脉供血与腹主动脉供血肺隔离症的影像学征象。方法：回顾性分析经术后病理证实的23例肺隔离症病例,对比分析胸主动脉供血及腹主动脉供血肺隔离症的CT 图像。结果：23例肺隔离症中,16例由胸主动脉供血,其中7例有2支供血动脉;7例由腹主动脉供血。21例表现为实性软组织密度,1例胸主动脉供血者表现为囊实性不均匀密度,1例胸主动脉供血者表现为局部粗大血管。胸主动脉供血动脉直径（4．8±2．2）mm,长度（37±12）mm,腹主动脉供血动脉直径（3．3±0．5）mm,长度（104±42）mm。胸主动脉供血血管长度及隔离肺组织体积均小于腹主动脉供血（P均＜0．001）。结论：胸主动脉供血及腹主动脉供血肺隔离症的肺内表现相似,胸主动脉与腹主动脉供血动脉长度及隔离肺组织体积存在差异。     

胸主动脉MR仿真内镜检查的临床应用及其缺陷

目的：研究MR仿真内镜（MRVE）对胸主动脉解剖及病变的临床应用价值。探讨其成像方法及存在缺陷。方法：对20例健康检查者及33例临床考虑胸主动脉病变的患者行MR三维动态增强扫描血管成像（3D-DCE-MRA）检查，将其原始数据进行仿真内镜重建处理，观察其对血管内表面解剖及病变的显示能力。结果：MRVE直观地显示胸主动脉解剖及病变情况，21例夹层动脉瘤，MRVE清楚地显示夹层动脉瘤入口，内膜移位及瘤腔情况；对主动脉瘤及大动脉炎可显示其扩张或缩窗的内腔结构；对法乐氏四联征，清楚地显示主动脉骑跨及骑跨程度；半环状伪影为MRVE主要存在的伪影。结论：MRVE能直观地显示胸主动脉内壁的解剖及病变情况，可作为临床怀疑胸主动脉病变患者的常规检查手段。     

多层螺旋CT对主动脉夹层动脉瘤的诊断价值

目的探讨多层螺旋CT对主动脉动脉瘤的诊断价值。方法对25例主动脉瘤患者于临床症状出现后进行多层螺旋CT平扫加增强扫描并利用原始数据在AW4．3工作站进行MPR及VR后处理。结果横轴位图像上可观察到真假腔形态、大小、剥脱的内膜片、破口位置及内膜和主动脉壁钙化,MPR重建图像能观察主动脉弓受累情况,确定内膜剥离范围,显示内膜与各分支血管之间的关系,按DeBakey分型,本组患者表现为Ⅰ型4例,Ⅱ型2例,Ⅲ型19例。结论多层螺旋CT能直观、立体显示真、假腔的形态、大小,破口位置及其与大分支血管的关系,因而它应是诊断夹层动脉瘤的首选检查方法。     

Congenital diseases of the thoracic aorta. Role of MRI and MRA

Aortic malformations may be associated with other congenital heart abnormalities or may present independently, as incidental findings in asymptomatic patients. For more than 30 years, conventional imaging techniques for detection and assessment of congenital anomalies of the aorta have been chest X-ray, echocardiography and angiography. In recent times, considerable interest in congenital aortic diseases has been shown, due to technical progresses of noninvasive imaging modalities. Among them, magnetic resonance imaging (MRI) almost certainly offers the greatest advantages, especially in young patients in which a radiation exposure must be avoided as much as possible. MRI provides an excellent visualization of vascular structures with a wide field of view, well suited for evaluation of the thoracic aorta malformations. With the implementation of magnetic resonance angiography (MRA) it is also possible to depict any relationship with supra-aortic or mediastinal vessels. Phase contrast technique allows identification of the hemodynamic significance of the aortic alteration. Some technical considerations, which include fast spin-echo, gradient-echo and, especially, MRA techniques with phase-contrast and contrast enhanced methods, are discussed and applied in the evaluation of congenital thoracic aorta diseases.     

Acquired diseases of the thoracic aorta: role of MRI and MRA

Diseases of the thoracic aorta can present with a broad clinical spectrum of symptoms and signs. Their prevalence appears to be increasing in western populations, most likely corresponding to aging and heightened clinical awareness but also influenced by the progress of high-resolution, noninvasive imaging modalities. Among them, MRI provides an excellent visualization of vascular structures and is well suited for evaluation of thoracic aorta disease. Currently, in many centers, noninvasive imaging modalities are the first choice in the cardiovascular system evaluation and diagnosis, reserving conventional angiography for use only before therapeutic intervention. Understanding the principle MRA techniques is essential for acquiring consistent diagnostic images. Basic technical considerations, which include fast spin-echo, fast gradient-echo, and MRA techniques with phase contrast and contrast-enhanced methods, are discussed and applied in the evaluation of acquired thoracic aorta diseases.     

MR diagnosis of a congenital abnormality of the thoracic aorta with an aneurysm of the right subclavian artery presenting as a Horner's syndrome in an adult

Congenital abnormality of the aortic arch is a diagnosis made most of the time incidentally in childhood, unless dysphagia or respiratory disorders occur before. A case of a complex aortic arch anomaly with an aneurysm of the right subclavian artery presenting as an isolated Horner's syndrome in an adult is reported herein. Magnetic resonance imaging led to this very unusual diagnosis. Received: 17 March 1999; Revised: 15 July 1999; Accepted: 13 August 1999     

Abdominal aortic dissection with retrograde extension into the thoracic aorta: Case report

A case of spontaneous dissection originating in the infrarenal abdominal aorta with retrograde extension into the thoracic aorta is reported along with the computed tomography and angiographic findings. Surgical repair resulted in the obliteration of the false lumen, healing of the thoracic hematoma, and clinical recovery. The principles for radiologic evaluation and therapeutic management are discussed.     

Contrast-enhanced three-dimensional MR angiography of the thoracic aorta: experiences after 118 examinations with a standard dose contrast administration and different injection protocols

The aim of this study was to test three injection protocols for contrast-enhanced magnetic resonance angiography (MRA) of the thoracic aorta with a standard-dose application. Ninety-three patients with a total of 118 examinations underwent MRA of the thoracic aorta at 1.5 T. There were three injection protocols: in 24 cases, no test bolus was performed and contrast was injected manually; in 14 cases, contrast was injected manually after a test bolus; and in 80 cases, a MR-compatible injector was used after a timing examination. All patients received 20 ml of Gd-DTPA. Quantitative signal-to-noise (SNR) measurements were obtained at different locations in the thoracic aorta, the pulmonary arteries, and the superior vena cava. Two readers in conference retrospectively evaluated each examination with respect to overall image quality and quality of bolus timing. Bolus timing was considered optimal in 70 cases, and either too early or too late in 11 cases. In 37 examinations the bolus was broadened. The SNR measurements of the thoracic aorta revealed that examinations after bolus testing were significantly superior to examinations without a test bolus (p < 0.001). Signal intensity ratios of the aorta and the pulmonary trunk were significantly higher in examinations with an optimal contrast timing (p < 0.001). Magnetic resonance angiograms of the thoracic aorta with a timing run are significantly superior to non-timed examinations with respect to image quality and SNRs. The administration of 20 ml of Gd-DTPA is sufficient for adult patients.     

Imaging of acute traumatic injuries of the thoracic aorta

Blunt traumatic aortic injuries are a major concern in the settings of high-speed deceleration accidents, since they are associated with a very high mortality rate; however, with prompt diagnosis and surgery, 70% of the patients with a blunt aortic lesion who reach the hospital alive will survive. This statement challenges the emergency radiologist in charge to evaluate the admission radiological survey in a severe chest trauma patient. With a 95% negative predictive value for the identification of blunt traumatic aortic lesions, plain chest film represents an adequate screening test. If aortography remains the gold standard, it tends, at least in hemodynamically stable trauma patients, to be replaced by spiral-CT angiography (SCTA), which demonstrates a 96.2% sensitivity, a 99.8% specificity, and a 99.7% accuracy. In unstable patients, trans-esophageal echography (TEE) plays a major diagnostic role. Knowledge of advantages and pitfalls of these imaging techniques, as reviewed in this article, will help the emergency radiologist to choose the appropriate algorithm in the diagnosis of traumatic aortic injury, for each trauma patient.     

Concomitant lower thoracic spine disc disease in lumbar spine MR imaging studies

Our objective was to study the coexistence of lower thoracic-spine disc changes in patients with low back pain using a large field of view (FOV) in lumbar spine MR imaging. One hundred fifty patients with low back pain were referred to an MR examination. All patients were studied with a large FOV (27 cm), covering from the coccyx to at least the body of T11. Discs were coded as normal, protrusion, and extrusion (either epiphyseal or intervertebral). The relationship between disc disease and level was established with the Pearson χ² test. The T11–12 was the most commonly affected level of the lower thoracic spine with 58 disc cases rated as abnormal. Abnormalities of T11–12 and T12–L1 discs were significantly related only to L1–L2 disease (p=0.001 and p=0.004, respectively) but unrelated to other disc disease, patient's gender, and age. No correlation was found between other discs. Magnetic resonance imaging of the lumbar spine can detect a great amount of lower thoracic disease, although its clinical significance remains unknown. A statistically significant relation was found within the thoracolumbar junctional region (T11–L2), reflecting common pathoanatomical changes. The absence of relation with lower lumbar spine discs is probably due to differences in their pathomechanisms. Electronic Publication     

多层螺旋CT血管造影在主动脉夹层及主动脉瘤诊断中的价值

目的：探讨多层螺旋CT血管造影在主动脉夹层及主动脉瘤中的临床应用价值。方法：对34例临床怀疑主动脉疾病者进行CT血管造影，层厚3．2mm，重建间隔1．6mm，pitchl 25，对比剂用量100ml，注射速度3ml/s，延迟时间23～28s；对所有病人进行最大密度投影、多平面重组、表面遮盖显示、仿真内窥镜、容积再现重组。结果：34例中，正常者7例，主动脉夹层16例，主动脉瘤7例，左锁骨下动脉瘤1例，马凡综合征1例，主动脉弓血管置换术后1例，腹主动脉瘤血管内支架术后1例。结论：MSCTA在主动脉夹层及主动脉瘤中有积极的临床应用价值，横断面CTA为诊断主动脉疾病的基础，图像后处理技术作为补充。     

Heartbeat-related distension and displacement of the thoracic aorta in healthy volunteers

Purpose

To test our hypothesis that distension and displacement in various segments of the healthy thoracic aorta are significant and can be predicted based on clinical characteristics.

Materials and methods

Sixty-one Caucasian volunteers without cardiovascular disease (49 ± 16 years, range 19–82; 28 men, 33 women) divided into two age groups (A: <50, B: ≥50 years) underwent 1.5-T MRI. ECG-gated dynamic data sets were acquired at five locations perpendicular to the thoracic aorta. Aortic distension and Centre of Mass (CoM) displacement were determined as percentages of diastolic aortic diameter. A multiple linear regression model including age group, gender, location, mean arterial blood pressure, heart rate and body mass index was tested.

Results

Mean aortic distension averaged over all locations was 11.2 ± 4.1% (age group A) and 6.7 ± 3.3% (age group B), mean displacement 15.1 ± 8.3% (A) and 11.0 ± 6.2% (B). Systolic and diastolic aortic diameter and CoM position significantly differed at all locations (p < 0.001). Distension and displacement could be predicted based on the regression model (p < 0.001). Age group A and women exhibited significantly greater distension and displacement compared to age group B (p < 0.001) and men (p < 0.01), respectively. Distension increased, displacement decreased from proximal to distal.

Conclusion

Distension and translational displacement are significant at all levels of the thoracic aorta and can be predicted based on clinical characteristics.