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.     

Three-dimensional contrast-enhanced magnetic resonance angiography of the thoracic vasculature

Magnetic resonance angiography (MRA) has become a useful non-invasive imaging technique for the assessment of vascular disease. Due to limitations such as respiratory motion artefacts, saturations problems, and long acquisition times, applications of MRA in the thorax have largely been restricted to imaging of the aorta. The recent introduction of breath-hold three-dimensional (3D) contrast-enhanced MRA promises not only to enhance conventional MR protocols for aortic imaging, but to extend the clinical indications of MRI to diseases affecting other vascular structures of the thorax, most notably the pulmonary arteries. This article describes the technical aspects of contrast-enhanced 3D MRA and reviews existing and potential future clinical applications. Received 17 September 1996; Revision received 6 November 1996; Accepted 8 November 1996     

Hydatid disease of right ventricle and pulmonary arteries: a rare cause of pulmonary embolism—computed tomography and magnetic resonance imaging findings (2009: 5b)

Hydatid disease can occur anywhere in the body and can demonstrate different imaging features that vary according to growth stage, associated complications, and affected tissue. Cardiovascular system involvement of hydatid disease is very rare. In this article, we present the cardiac magnetic resonance (MR) and thorax computed tomography (CT), MR angiography (MRA) findings of hydatid cysts located in the right ventricle and pulmonary arteries after surgical removal of hepatic hydatid cysts.     

Infra-renal abdominal aorta agenesis: a case report with emphasis on MR angiography findings

The purpose of this study is to report a case of infra-renal aorta agenesis with emphasis on the MR angiography (MRA) findings. A 66-year-old woman presented with urinary complaints. Pelvic and abdominal ultrasound showed hydronephrosis secondary to ureteral lithiasis; the distal portion of the abdominal aorta was not identified. Abdominal CT showed that the infra-renal portion of the abdominal aorta was apparently absent. MRI and MRA demonstrated that, after the origin of the renal arteries, the abdominal aorta spontaneously terminated in two lumbar hypertrophic arteries. In addition, MRA showed a dilated superior mesenteric artery that formed a vascular loop, which continued posterior and inferiorly towards the posterior pelvic region. In this region, it bifurcated and formed internal iliac branches, which were responsible for the arterial supply of the pelvis. In conclusion, MRA allows for precise evaluation of patients with infra-renal abdominal aorta agenesis. Although it is a rare entity, radiologists should be able to recognize it in ultrasound, CT and MRI studies.     

Acute chest pain: The role of MR imaging and MR angiography

MR imaging (MRI) and MR angiography (MRA) have gained a high level of diagnostic accuracy in cardiovascular disease. MRI in cardiac disease has been established as the non-invasive standard of reference in many pathologies. However, in acute chest pain the situation is somewhat special since many of the patients presenting in the emergency department suffer from potentially life-threatening disease including acute coronary syndrome, pulmonary embolism, and acute aortic syndrome. Those patients need a fast and definitive evaluation under continuous monitoring of vital parameters. Due to those requirements MRI seems to be less suitable compared to X-ray coronary angiography and multislice computed tomography angiography (CTA). However, MRI allows for a comprehensive assessment of all clinically stable patients providing unique information on the cardiovascular system including ischemia, inflammation and function. Furthermore, MRI and MRA are considered the method of choice in patients with contraindications to CTA and for regular follow-up in known aortic disease. This review addresses specific features of MRI and MRA for different cardiovascular conditions presenting with acute chest pain.     

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.     

Pulmonary circulation

Evaluation of the pulmonary vasculature is mainly indicated in patients with suspected pulmonary thromboembolism. The routine procedure so far is ventilation-perfusion scintigraphy alone or in combination with diagnostic assessment of the legs to rule out deep venous thrombosis. The results are still not reliable for the majority of patients. In the case of equivocal diagnosis, invasive conventional angiography is considered the gold standard. With steady improvements in tomographic imaging techniques, such as computed tomography (CT) or magnetic resonance imaging (MRI), non-invasive alternatives to the routine diagnostic work-up are given. Helical CT and CTA techniques are already in clinical use and estimated to sufficiently serve the demands for detection/exclusion of pulmonary thromboembolism. The disadvantages mainly concern peripheral disease and reconstruction artifacts. MRI and MR angiography have been implemented in the diagnosis of pulmonary vascular disease since the introduction of contrast-enhanced MRA. In breath-hold techniques, the entire lung vascularization can be delineated and thromboemboli can be detected. The clinical experience in this field is limited, but MRI has the potential to demonstrate its superiority over CT due to its improved delineation of the vascular periphery and the more comprehensive three-dimensional reconstruction. Received: 20 January 1998; Accepted: 10 February 1998     

Diagnostic accuracy of contrast-enhanced MR angiography and unenhanced proton MR imaging compared with CT pulmonary angiography in chronic thromboembolic pulmonary hypertension

Objective

To evaluate the diagnostic accuracy of contrast-enhanced MR angiography (CE-MRA) and the added benefit of unenhanced proton MR angiography compared with CT pulmonary angiography (CTPA) in patients with chronic thromboembolic disease (CTE).

Methods

A 2?year retrospective study of 53 patients with chronic thromboembolic pulmonary hypertension who underwent CTPA and MRI for suspected pulmonary hypertension and a control group of 36 patients with no CT evidence of pulmonary embolism. The MRI was evaluated for CTE and the combined diagnostic accuracy of ce-MRA and unenhanced proton MRA was determined. CE-MRA generated lung perfusion maps were also assessed.

Results

The overall sensitivity and specificity of CE-MRA in diagnosing proximal and distal CTE were 98% and 94%, respectively. The sensitivity improved from 50% to 88% for central vessel disease when CE-MRA images were analysed with unenhanced proton MRA. The CE-MRA identified more stenoses (29/18), post-stenosis dilatation (23/7) and occlusions (37/29) compared with CTPA. The CE-MRA perfusion images showed a sensitivity of 92% for diagnosing CTE.

Conclusion

CE-MRA has high sensitivity and specificity for diagnosing CTE. The sensitivity of CE-MRA for visualisation of adherent central and lobar thrombus significantly improves with the addition of unenhanced proton MRA which delineates the vessel wall.     

CT in vascular pathologies

Since the introduction of helical scanners, CT angiography (CTA) has achieved an essential role in many vascular applications that were previously managed with conventional angiography. The performance of CTA is based on the accurate selection of collimation width, pitch, reconstruction spacing and scan delay, which must be modulated on the basis of the clinical issue. However, the major improvement of CT has been provided by the recent implementation of many post-processing techniques, such as multiplanar reformatting, shaded surface display, maximum intensity projections, 3D perspectives of surface and volume rendering, which simulate virtual intravascular endoscopy. The integration of the potentialities of the scanner and of the image processing techniques permitted improvement of: (a) the evaluation of aneurysms, dissection and vascular anomalies involving the thoracic aorta; (b) carotid artery stenosis; (c) aneurysms of abdominal aorta; (d) renal artery stenosis; (e) follow-up of renal artery stenting; and (f) acute or chronic pulmonary embolism. Our experience has shown that the assessment of arterial pathologies with CTA requires the integration of 3D post-processing techniques in most applications. Received 23 December 1997; Accepted 2 January 1998     

Vascular diseases of the thorax: evaluation with multidetector CT

The list of vascular diseases in the thorax has been narrowed to three, which are considered essential information for radiologists interpreting CT scans of the thorax: (1) aortic dissection and its variants, intramural hematoma and penetrating atherosclerotic ulcer; (2) acute pulmonary embolism; and (3) coronary artery disease. The spatial resolution of multidetector CT is such that CT has become the imaging modality of choice for aortic dissection and pulmonary embolism. This move away from angiography has transpired over the last decade; perhaps the next decade will see the same occur for evaluation of coronary artery disease.     

CT and MR imaging of the thoracic aorta: current techniques and clinical applications

Disease of the thoracic aorta can present with a broad clinical spectrum of symptoms and signs. The accepted diagnostic gold standard, selective digital subtraction angiography, is now being challenged by state-of-the-art CT angiography (CTA) and MR angiography(MRA). Currently, in many centers, cross-sectional imaging modalities are being used as the first line of diagnosis to evaluate the cardiovascular system, and conventional angiography is reserved for therapeutic intervention. Understanding the principles of CTA and MRA techniques is essential to acquire diagnostic images consistently. This article reviews current CTA and MRA methods used in the evaluation of thoracic aortic disease.     

Non-traumatic thoracic emergencies: CT diagnosis of acute pulmonary embolism: the first 10 years

Over the past 10 years, spiral CT angiography of the pulmonary arteries has reached a high accuracy in the evaluation of pulmonary embolism. Major advantages of CT compared with ventilation/perfusion lung scintigraphy and pulmonary angiography is direct visualization of clots in the pulmonary arteries, and to provide alternative findings or diagnosis. The recent introduction of multislice CT has improved the evaluation of peripheral pulmonary arteries, enabling high-resolution CT examinations over the entire thorax in a short breathhold. The examination techniques, imaging findings, pitfalls, and results of CT in the diagnosis of pulmonary embolism are reviewed in comparison with other diagnostic tests.     

Prospective comparison of helical CT and MR imaging in clinically suspected acute pulmonary embolism

The purpose of this study is to compare sensitivity and specificity of helical CT and MR imaging for detecting acute pulmonary embolism (PE). Patients who were suspected clinically of having PE were randomly assigned to undergo either helical contrast-enhanced CT or gradient-echo MR (if one modality was contraindicated, the patient was assigned to the other). Patients were considered to have PE if they had: (1) high-probability V-Q scan and high clinical probability of PE; or (2) pulmonary angiogram positive for PE. Patients were considered not to have PE if they had either: (1) normal V-Q scan; (2) low probability V-Q scan and low clinical probability of PE; or (3) pulmonary angiogram negative for PE. The CT and MR images were read randomly and independently by five radiologists with varying levels of CT and MR experience. Twenty eight patients underwent CT and 25 MR. A total of 21 patients underwent pulmonary angiography (6 had PE, 15 did not have PE). Of the other 32 patients, 15 had high probability scan/high clinical probability and 17 had low probability scan/low clinical probability. For the five observers, the average sensitivity of CT was 75% and of MR 46%; the average specificity of CT was 89% and of MR 90%. Experience with vascular MR and enhanced CT influenced diagnostic accuracy. For the two vascular MR experts, average sensitivity and specificity of MR were 71% and 97%, and of CT 73% and 97%. In this pilot study, when CT and MR were interpreted with comparable expertise, they had similar accuracy for detecting pulmonary embolism.     

Pulmonary magnetic resonance angiography

In the past few years magnetic resonance angiography (MRA) of the pulmonary vasculature has advanced from a research tool to a clinically relevant imaging modality. Early 2D phase-contrast and time-of-flight (TOF) sequences without the use of contrast agents were time-consuming and limited by considerable imaging and motion artifacts. Since the introduction of MR scanners with stronger gradients (> 20 mT/m) and contrast-enhanced techniques, imaging of the pulmonary vasculature with adequate spatial resolution within a single breathhold is now possible. In the detection of pulmonary embolism in the lobar or segmental arteries, contrast-enhanced MRA is now on the verge of being considered an established modality, possibly competing with conventional pulmonary angiography and contrast-enhanced helical CT. In the future, utilization of phased-array torso coils, the application of navigator pulse sequences, and 3D time-resolved ultrafast MRA will overcome the final limitations of current techniques. Blood-pool MR contrast agents may provide a “one-stop-shopping” approach to the investigation of lower extremity veins and pulmonary arteries in venous thromboembolism.     

Value of contrast-enhanced MR angiography and helical CT angiography in chronic thromboembolic pulmonary hypertension

The aim of this study was to evaluate the diagnostic value of contrast-enhanced MR angiography (ce MRA) and helical CT angiography (CTA) of the pulmonary arteries in the preoperative workup of patients with chronic thromboembolic pulmonary hypertension (CTEPH). The ce MRA and CTA studies of 32 patients were included in this retrospective evaluation. Image quality was scored by two independent blinded observers. Data sets were assessed for number of patent segmental, subsegmental arteries, and number of vascular segments with thrombotic wall thickening, intraluminal webs, and abnormal proximal to distal tapering. Image quality for MRA/CTA was scored excellent in 16 of 16, good in 11 of 14, moderate in 2 of 5, and poor in no examinations. The MRA/CTA showed 357 of 366 patent segmental and 627 of 834 patent subsegmental arteries. CTA was superior to MRA in visualization of thrombotic wall thickening (339 vs 164) and of intraluminal webs (257 vs 162). Abnormal proximal to distal tapering was better assessed by MRA than CTA (189 vs 16). In joint assessment of direct and indirect signs, MRA and CTA were equally effective (353 vs 355). MRA and CTA are equally effective in the detection of segmental occlusions of the pulmonary arteries in CTEPH. CTA is superior for the depiction of patent subsegmental arteries, of intraluminal webs, and for the direct demonstration of thrombotic wall thickening.     

肺动静脉畸形的综合影像评价

目的 评价各种影像学检查手段诊断肺动静脉畸形的作用。材料与方法 回顾性分析11例肺动静脉畸形患者的各种影像学检查的表现、胸片、肺动静脉造影11例,CT平扫7例（增强4例）,MR扫描2例（PA、MRA）,并计算各种检查方法的敏感性。结果 肺动静脉造影发现病灶29个,病灶呈瘤样扩张的血管,有1条供血动脉和数条引流静脉,引流静脉和左房早期显影。胸片表现为肺内局限结节样影且有异常血管与肺门相连,其敏感性为79.3%(23/29）。CT表现为病灶密度均实,边界光整,并有典型的“血管蒂”征,增强扫描示病灶与肺动脉同步强化,多平面重建（MPR）有助于认识其相关血管,检查敏感性为94.4%(17/18）。MR扫描敏感性的80.8%(4/5）,对比增强肺动脉MR成像（CE MRA）可弥补常规序列的不足,有助于显示病变全貌,图像堪与肺动脉造影相比。结论 胸片可作为筛选方法,而肺动脉造影是诊断的“金标准”;CT可以提供与肺动脉造影相同的诊断信息,在某种程度上可取代肺动脉造影;MR特别是动态增强MRA不仅可以在形态上确认病灶,还可用以评价血流动力学改变和评估预后。胸片与CT是最佳的治疗后随访手段。     

三维动态增强磁共振血管造影诊断肺隔离症的价值

目的：评估三维动态增强磁共振血管造影（3D DCE MRA）对显示肺隔离症异常血管的价值。方法：5例肺隔离症患者作了胸部正侧芯片，CT和MRI检查后，均行胸部和上腹部3D DCE MRA检查，并进行最大信号强度投影（MIP）和多平面重建（MPR）。结果：5例肺隔离症均为肺叶内型，位于左肺下叶。胸片表现隔离的肺组织均位于左下叶，呈圆形或椭圆形，密度较均匀的团块影。CT示降主动脉后方软组织密度肿块，2例肿块周围伴有肺气肿。增强CT显示2例供血动脉。平扫MRI示隔离肺组织在T1WI和T2WI较正常肺组织信号高的软组织块影，并显示3例供血动脉，但未能显示其作貌，行程，分支及引流静脉。另2例异常供血动脉未能显示，而3D工DCE MRA均显示了其异常供血动脉和引流静脉，并清楚显示了其分支和行程，与术中所见完全一致。结论：3D DCE MRA较能较好地显示肺隔离症的异常供血动脉和引流静脉，有利于确诊此病和制订手术治疗方案。     

MR and MR angiography characterization of soft tissue vascular malformations

Hemangioma is an abnormal proliferation of blood vessels that may occur in any vascularized tissue. Different classifications separate vascular lesions of soft tissues into hemangiomas and vascular malformations on the basis of their natural history, location, cellular turnover, and histology. Soft-tissue vascular malformations are relatively common. These lesions can be categorized on MR imaging because of their typical appearance as multiple lobules with fat overgrowth and serpentine channels, depending on the vascular flow. The combination of conventional MR and MR angiography (MRA) enable the differentiation between low-flow and high-flow vascular malformations and allows a noninvasive diagnostic strategy. This article reviews the MR and MRA imaging characteristics of soft-tissue hemangiomas to provide a helpful guide for radiologists to perform a more specific diagnosis and better management of these anomalies.     

Intra-arterial MR angiography in the iliac system: initial clinical experience with 25 patients

The aim of this study was to evaluate intra-arterial magnetic resonance angiography (MRA) of the iliac arteries. Therefore, 25 consecutive patients (17 male, 8 female) suffering from symptomatic occlusive disease of the lower limbs were investigated prospectively. Catheter angiography was performed before MRA and served as the standard of reference. Contrast-enhanced intra-arterial MRA was performed using a 1.5 Tesla MRI system. Contrast agent (gadodiamide) was injected by a conventional pigtail-shaped angiography catheter placed in the abdominal aorta. Vascular lesions were assessed by four investigators. The degree of stenosis was compared with the findings of conventional catheter angiography. Additionally, the diagnostic quality of the MR angiograms was assessed by the investigators using a semi quantitative five-point scale. All lesions shown by catheter angiography were detected and correctly localized by intra-arterial MRA. MR angiograms exhibit a specificity of 95% and a sensitivity of 96% for stenoses of 50% or more. The diagnostic quality of the images was judged from good to excellent, on average. Intra-arterial MRA exhibits a specificity and sensitivity comparable with intravenous angiography. The image quality appears to be adequate for supporting MR-guided vascular intervention.     

Moderne Schnittbildgebung der Kopf-Hals-Gefäße

Although digital subtraction angiography (DAS) remains the gold standard for neurovascular imaging, the number of diagnoses made on the basis of less invasive cross-sectional imaging techniques (CT and MR angiography) is increasing. The present article provides important technical principles of CT and MR angiography, followed by an analysis of the diagnostic possibilities and limitations of vascular cross-sectional imaging. The particular importance of post-processing of vascular cross-sectional datasets is also discussed. Using the typical clinical diagnostic work-up of extra- and intracranial vascular diseases as a basis, the article explains how a suitable examination technique and protocol is chosen and which limitations need to be borne in mind. After taking at look at the technical advances expected in the future (3-Tesla MRA, dual-energy CTA, post-processing workflow in PACS), the remaining indications for diagnostic DSA will be presented and explained.