Congenital thoracic vascular anomalies: evaluation with state-of-the-art MR imaging and MDCT

Congenital thoracic vascular anomalies include embryologic developmental disorders of the thoracic aorta, aortic arch branch arteries, pulmonary arteries, thoracic systemic veins, and pulmonary veins. Diagnostic evaluation of these anomalies in pediatric patients has evolved with innovations in diagnostic imaging technology. State-of-the-art magnetic resonance (MR) imaging, MR angiography multidetector-row computed tomographic (MDCT) angiography, and advanced postprocessing visualization techniques offer accurate and reliable high-resolution two-dimensional and three-dimensional noninvasive anatomic displays for interpretation and clinical management of congenital thoracic vascular anomalies. This article reviews vascular MR imaging, MR angiography, MDCT angiography, and advanced visualization techniques and applications for the assessment of congenital thoracic vascular anomalies, emphasizing clinical embryology and the characteristic imaging findings.     

MR angiography of the thoracic aorta with an electrocardiographically triggered breath-hold contrast-enhanced sequence.

An electrocardiographically (ECG) triggered breath-hold contrast material-enhanced magnetic resonance (MR) angiography sequence has been developed for imaging the thoracic aorta. A three-dimensional (3D) gradient-echo sequence is used with a contrast material bolus. Forty-nine patients with various aortic abnormalities and five healthy volunteers underwent imaging with the sequence. All studies were performed in a single breath hold. ECG-triggered breath-hold contrast-enhanced MR angiography was tolerated in 48 of the 49 patients. The images demonstrated no respiratory motion artifacts and diminished pulsation artifacts. The cardiac chambers, aortic root, ascending and descending aorta, aortic arch, proximal arch vessels, and proximal coronary arteries were clearly demonstrated and not obscured by ghost artifacts. The 3D data set allowed excellent multiplanar reformation, permitting orthogonal or oblique views of the vascular anatomy. A variety of congenital and acquired abnormalities were clearly identified. When this sequence is used, it is important to evaluate both the maximum-intensity projection and source images. Delayed imaging should be performed to detect late filling. In conjunction with cine MR and T1-weighted spin-echo imaging, ECG-triggered breath-hold contrast-enhanced MR angiography should be considered the technique of choice for imaging the thoracic aorta.     

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.     

The role of MR imaging in the evaluation of acquired diseases of the thoracic aorta.

Because MR imaging combines the major attributes of angiography, echocardiography, and CT, its role in the evaluation of the thoracic aorta is steadily increasing. When standard spin-echo techniques are used, flowing blood produces a signal void that allows excellent depiction of the anatomy and simultaneous evaluation of the lumen, vessel wall, and periaortic structures. On dynamic or cine MR, flowing blood generates a signal that allows visualization of the blood as it pulsates through the aorta. Turbulent blood generates a signal void, thereby allowing the detection and qualitative assessment of the pathophysiologic consequences of anatomic abnormalities. With phase-mapping techniques, blood velocity can be measured and used to calculate pressure gradients. Recent advances in the field of MR angiography will greatly enhance the overall role of MR in the evaluation of the thoracic vasculature by allowing detection and assessment of the branch vessels. Although the technique is still evolving, it has shown extraordinary potential as a tool for studying the thoracic aorta. The exact role of MR in patient care will depend on advances in transesophageal echocardiography. However, it is not unreasonable to think that someday MR imaging will be the primary technique for evaluation of the thoracic aorta.     

Angeborene Fehlbildungen der Aorta im Kindes- und Jugendalter

Aortic abnormalities are common cardiovascular malformations accounting for 15-20% of all congenital heart disease. Ultrafast CT and MR imaging are noninvasive, accurate and robust techniques that can be used in the diagnosis of aortic malformations. While their sensitivity in detecting vascular abnormalities seems to be as good as that of conventional catheter angiocardiography, at over 90%, they are superior in the diagnosis of potentially life-threatening complications, such as tracheal, bronchial, or esophageal compression. It has been shown that more than 80% of small children with aortic abnormalities benefit directly from the use of noninvasive imaging: either cardiac catheterization is no longer necessary or radiation doses and periods of general anesthesia for interventional catheterization procedures can be much reduced.The most important congenital abnormalities of the aorta in children and adolescents are presented with reference to examples, and the value of CT and MR angiography is documented.     

MR imaging of congenital anomalies of the aortic arch

Eighteen patients with congenital aortic arch anomalies were evaluated by ECG-gated MR imaging. Transverse images encompassing the heart and thoracic aorta were available in all patients; sagittal or coronal studies were available in 12 patients. Visualization of the aortic arch, its orientation, and the origin and course of the arch vessels was assessed. Associated intracardiac abnormalities were noted, and the effect of aberrant vessels on the trachea or esophagus was determined. Thirteen patients had a right aortic arch. Mirror-image branching was found in 10 cases, and an aberrant left subclavian artery was found in three of these. Three patients had a left aortic arch with aberrant right subclavian artery, and two patients had a double arch. Tracheal compression caused by vascular rings was found in two patients with respiratory symptoms. Corroborating studies (angiography, surgery, CT, and autopsy) in 16 patients confirmed the MR diagnoses in all but one. We conclude that MR could substitute for other techniques as an effective, noninvasive method for the evaluation of congenital aortic arch anomalies.     

Right heart dilatation in adults: congenital causes

OBJECTIVE: The purpose of this article is to illustrate the common congenital cardiac lesions that are characterized by right-sided heart enlargement that may be seen on routine thoracic or cardiac imaging. CONCLUSION: A systematic approach to the evaluation of the right heart and an understanding of the congenital abnormalities causing right chamber enlargement will allow the radiologist to diagnose unsuspected cardiac abnormalities on routine clinical thoracic and cardiac imaging as well as accurately identify these defects on dedicated cardiac CT or MRI examinations.     

Levotransposition of the aorta: identification of segmental cardiac anatomy using MR imaging

Several reports have shown that high-quality magnetic resonance (MR) images can be obtained in patients with congenital heart disease. However, little attention has been paid to the segmental analysis of cardiac MR images. The authors believe that this approach is essential in the evaluation of complex congenital cardiac abnormalities. The segmental approach is based on the morphologic identification of the different cardiac compartments and the type of connection among these compartments. The authors applied the basic principles of the segmental approach to the interpretation of MR images obtained in a group of patients with levotransposition of the aorta. Results indicate that this logical step-by-step method can be used to advantage in the accurate analysis of MR images obtained in patients with complex congenital cardiac disease. In this report, the authors discuss the results obtained when the segmental approach is used to interpret cardiac MR images.     

MR imaging and CT of vascular anomalies and connections in patients with congenital heart disease: significance in surgical planning.

To plan effective management of congenital heart disease, one needs the clearest understanding of the anatomy. Although echocardiography and angiography are the dominant imaging modalities in patients with congenital heart disease, magnetic resonance (MR) imaging and computed tomography (CT) are valuable noninvasive adjuncts. MR imaging and CT are effective in demonstrating the complex cardiovascular morphology present in congenital heart disease, especially the extracardiac morphology. In patients with tetralogy of Fallot with complex pulmonary artery anatomy, MR imaging and CT are useful in demonstrating the pulmonary artery anatomy, along with the significant aortopulmonary collateral vessels. In the heterotaxy syndromes, patients often have unusual atriovenous connections. MR imaging allows accurate identification of the hepatic, systemic, and pulmonary veins and their relationships to both atria. CT and MR are the imaging modalities of choice in a patient who is thought to have a vascular ring. Treatment of aortic coarctation is usually performed on the basis of typical clinical and echocardiographic findings. In patients with atypical clinical or echocardiographic findings, MR imaging and CT yield helpful information that can change the treatment plan. The enhanced preoperative understanding of congenital heart disease provided by MR imaging and CT simplifies surgical decision making and consequently may improve outcome.     

Congenital heart disease: gated MR imaging in 72 patients

Seventy-two patients (aged 2 months to 75 years; mean 23 years) with a variety of congenital anomalies of the heart and great vessels underwent ECG-gated magnetic resonance (MR) imaging using the multisectional spin-echo technique (0.35 Tesla). The ability to define segmental anatomy and intracardiac anomalies on transverse, sagittal, and coronal images was evaluated. MR images were graded as excellent, diagnostic, or nondiagnostic, and MR findings were corroborated by angiography and/or two-dimensional echocardiography. Studies that were considered to be excellent or diagnostic were obtained in 96% of the cases. Visceroatrial situs, the type of ventricular loop, and the relationship of the great vessels could be identified in all patients with studies encompassing the entire heart. Forty-four of 47 abnormalities at the level of the great vessels were identified with MR, including coarctation of the aorta and vascular rings. MR showed 32 of 35 ventricular abnormalities; 2 small ventricular septal defects and 1 Ebstein anomaly were not demonstrated. All of the abnormalities at the atrial level and those of systemic and pulmonary venous return were seen on MR images. Complex cardiac anomalies, such as single ventricles, and the status of the pulmonary arteries were clearly demonstrated, and a good assessment of total and palliative postoperative anatomy was provided.     

Non-contrast-enhanced MR angiography of the thoracic aorta using cardiac and navigator-gated magnetization-prepared three-dimensional steady-state free precession

PURPOSE: To assess the usefulness of non-contrast-enhanced MR angiography using cardiac and navigator-gated magnetization-prepared three-dimensional (3D) steady-state free precession (SSFP) imaging for the diagnosis of diseases of the thoracic aorta. MATERIALS AND METHODS: Twenty-two patients with diseases of the thoracic aorta were examined using a 1.5 Tesla unit. Non-contrast-enhanced MR angiography was done using parasagittal 3D SSFP combined with cardiac-gating and k-space weighted navigator-gating techniques, using T2-prepared and fat-suppression pulses. Imaging quality and the diagnostic capability of this technique were compared with the imaging quality of 2D SSFP or contrast-enhanced 3D MR angiography and with final diagnoses. RESULTS: Non-contrast-enhanced 3D MR angiography provided signal-to-noise and contrast-to-noise ratios of the thoracic aorta comparable to non-contrast-enhanced 2D or contrast-enhanced 3D MR angiography (P > 0.17). This imaging technique gave accurate diagnoses in 19 of the 22 patients. CONCLUSION: Non-contrast-enhanced MR angiography using cardiac and navigator-gated magnetization-prepared 3D SSFP technique was useful for the diagnosis of diseases of the thoracic aorta.     

State-of-the-Art CT Imaging Techniques for Congenital Heart Disease

CT is increasingly being used for evaluating the cardiovascular structures and airways in the patients with congenital heart disease. Multi-slice CT has traditionally been used for the evaluation of the extracardiac vascular and airway abnormalities because of its inherent high spatial resolution and excellent air-tissue contrast. Recent developments in CT technology primarily by reducing the cardiac motion and the radiation dose usage in congenital heart disease evaluation have helped expand the indications for CT usage. Tracheobronchomalacia associated with congenital heart disease can be evaluated with cine CT. Intravenous contrast injection should be tailored to unequivocally demonstrate cardiovascular abnormalities. Knowledge of the state-of-the-art CT imaging techniques that are used for evaluating congenital heart disease is helpful not only for planning and performing CT examinations, but also for interpreting and presenting the CT image findings that consequently guide the proper medical and surgical management.     

Contributions of newer MR imaging strategies for congenital heart disease.

Magnetic resonance (MR) imaging is a valuable noninvasive adjunct in the evaluation of congenital heart disease (CHD). With its multiplanar image acquisition, good spatial resolution, and large-field-of-view image display, MR imaging can allow appreciation of vascular connections not readily apparent at echocardiography or angiography. Evaluation of CHD with MR imaging has two components: definition of cardiovascular anatomy and characterization of blood flow. However, the variety of MR imaging options is large and often confusing. Besides spin-echo and gradient-echo imaging, MR imaging techniques for evaluation of CHD include MR angiography, cine MR imaging, and flow quantification. An understanding of the potential MR imaging options enables formulation and more efficient application of MR imaging strategies. When performed well, MR imaging greatly enhances surgical planning and can even obviate cardiac catheterization. MR imaging is also an excellent modality for serial evaluation of surgical results and complications in cases of CHD.     

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     

MR imaging of posterior fossa infarctions: vascular territories and clinical correlates.

Ischemic infarctions in certain vascular territories of the cerebellum and brain stem can produce some characteristic radiologic and clinical patterns. The cerebellum serves as a coordination center for the maintenance of equilibrium and muscle tone and refines the movements of the somatic muscles. The anatomy of the brain stem is extremely complex, and small infarcts can potentially be disastrous. MR imaging depicts the anatomy of the posterior fossa and infarcts in this region with greater accuracy than was previously possible. Familiarity with the vascular territories and patterns of infarction of the posterior fossa depicted with MR imaging and familiarity with the associated clinical symptoms of stroke in this region can help the radiologist recognize these infarcts and correlate clinical and radiologic findings. When patients are referred for MR imaging of the brain because of clinical findings suggestive of infarction, it may be useful to obtain coronal or sagittal views in addition to axial images to better depict the vascular distribution of a suspected ischemic lesion.     

Isolated absence of the optic chiasm: a rare cause of congenital nystagmus

The cases presented are rare examples of congenital nystagmus associated with isolated absence of the optic chiasm. MR imaging in both patients demonstrated unremarkable anterior optic pathways and optic tracts. No additional midline central nervous system abnormalities, migrational anomalies, space-occupying lesions, or destructive processes were noted. These cases demonstrate that the achiasmatic syndrome should be included in the differential diagnosis of congenital nystagmus and may be overlooked without careful MR imaging evaluation.     

Aberrant right common carotid and subclavian arteries causing tracheoesophageal compression combined with persistent left superior vena cava—case report

Vascular rings are a rare group of congenital thoracic vascular anomalies which are characterized by abnormal vascular structures that completely or incompletely encircle the trachea, esophagus, or both. We report the case of a vascular ring formed around the trachea and esophagus by aberrant right subclavian artery and aberrant right common carotid artery, associated with persistent left superior vena cava, complete absence of azygos vein, and with multiple nonvascular abnormalities. Recurrent pulmonary infections were the only clinical manifestation of this complex vascular anomaly. Our report represents a so-far-undescribed anatomic variation of the vascular ring that clinicians should be aware of.     

Dynamic contrast-enhanced breath-hold MR imaging of thoracic malignancy using cardiac compensation

The purpose of this paper was to evaluate the use of dynamic gadopentetate dimeglumine-enhanced, breath-hold spoiled gradient-recalled (SPGR) MR imaging with cardiac compensation (CMON) compared to spin-echo MR imaging in patients with thoracic malignancy. We retrospectively reviewed MR images from 29 patients with thoracic tumors. MR imaging included axial electrocardiogram (ECG)-gated T1-weighted, fast spin echo (FSE) T2-weighted, and contrast-enhanced breath-hold fast multiplanar SPGR imaging with CMON, which selects the phase-encoding gradient based on the phase within the cardiac cycle. Images were reviewed for lung masses, mediastinal or hilar tumor, disease of the pleura, chest wall, and bones, and vascular compression or occlusion. Contrast-enhanced fast multiplanar SPGR imaging with CMON produces images of the chest that are free of respiratory artifact and have diminished vascular pulsation artifact. ECG-gated T1-weighted images were preferred for depicting mediastinal and hilar tumor. The gadopentetate dimeglumine-enhanced fast multiplanar SPGR images were useful for depicting chest wall tumor, vascular compression or thrombosis, osseous metastases, and in distinguishing a central tumor mass from peripheral lung consolidation. Pleural tumor was depicted best on the FSE T2-weighted images and the contrast-enhanced SPGR images. As an adjunct to spin echo T1-weighted and T2-weighted imaging, contrast-enhanced fast multiplanar SPGR imaging with CMON is useful in the evaluation of thoracic malignancy.     

MR Imaging of Congenital Heart Diseases in Adolescents and Adults

Echocardiography and catheterization angiography suffer certain limitations in the evaluation of congenital heart diseases in adults, though these are overcome by MRI, in which a wide field-of view, unlimited multiplanar imaging capability and three-dimensional contrast-enhanced MR angiography techniques are used. In adults, recently introduced fast imaging techniques provide cardiac MR images of sufficient quality and with less artifacts. Ventricular volume, ejection fraction, and vascular flow measurements, including pressure gradients and pulmonary-to-systemic flow ratio, can be calculated or obtained using fast cine MRI, phase-contrast MR flow-velocity mapping, and semiautomatic analysis software. MRI is superior to echocardiography in diagnosing partial anomalous pulmonary venous connection, unroofed coronary sinus, anomalies of the pulmonary arteries, aorta and systemic veins, complex heart diseases, and postsurgical sequelae. Biventricular function is reliably evaluated with cine MRI after repair of te ralogy of Fallot, and Senning''s and Mustard''s operations. MRI has an important and growing role in the morphologic and functional assessment of congenital heart diseases in adolescents and adults.     

Thorax: new millennium vascular imaging

In recent years the technological development of computed tomography (CT) and magnetic resonance (MR) has promoted new improvements in diagnosis by means of imaging. In particular the introduction of multislice CT and MR angiography (MRA) has broadened the non-invasive diagnostic possibilities in the vascular study of the thorax. The new technological developments of CT and MR enable functional studies as well. Recent studies have demonstrated that CT and MR are as accurate in finding the vascular anomalies as digital subtraction angiography, while they are more precise in recognising possible associated pathologies which modify therapeutic treatment (for example of the trachea, bronchi, oesophagus etc.). There are many vascular structures in the thorax which need to be considered (aorta, pulmonary and coronary arteries, pulmonary veins, vena cava). The field of associated pathologies is also broad, and includes congenital vascular anomalies, vascular malformations, aorta dissection, vascular compression syndromes, atherosclerotic stenosis or occlusions, and pulmonary embolism. In pulmonary embolism some authors have demonstrated the utility of CT, in showing pulmonary segmental perfusion defects, and MRA, in identifying sub-segment pulmonary embolism. In this paper we analyse the most important CT and MR applications for the study of vascular thoracic diseases and compare them with other diagnostic techniques. We also evaluate the morpho-functional capabilities of CT and MR in this field.