AORTA DISEASES: MAGNETIC RESONANCE ANGIOGRAPHY VALUE

Transcription

1 AORTA DISEASES: MAGNETIC RESONANCE ANGIOGRAPHY VALUE

2 Magnetic resonance imaging (MRI) has been suggested as an ideal technique for imaging vascular disease. Recent reports suggest its utility in aortic lesions. MR angiography has the potential to accurately diagnose aortic dissection, coarctation, aneurysm, and Takayasu arteritis. It provides detailed vascular information, including the location, degree, extent, and patency of these abnormalities and evaluates surgical bypass grafts.

3 Between April 2005 and March 2008, 14 patients (9 women and 5 men, aged years; mean age, 44 years) with abnormalities of the aorta were examined by MR imaging. The study included four patients with aortic aneurysm, six with Takayasu disease, three with aortic dissection and one with aortic coarctation. MR imaging delineated the presence and extent of aortic aneurysm and showed the relationship of the aneurysm to arch vessels, renal and iliac arteries. It demonstrated intimal flaps and individual lumina in type III aortic dissection. Focal narrowing of the aorta in coarctation were well visualized and in Takayasu arteritis, aortic wall thickening and branch vessel narrowing were evaluated.

4 MRI was realized using a 1.5-T MR unit (GE Healthcare). The entire aorta from its root to bifurcation is imaged. We followed morphological sequences: T1 weighted FAT SAT, T2 weighted FAT SAT and 2D FIESTA. 3D breath hold contrast-enhanced (0.1 mmol/kg; gadopentetate dimeglumine [Magnevist], Nihon-Schering) MR angiography of the thoracic and abdominal aorta is performed to evaluate luminal narrowing or dilatation. After contrast medium injection, The entire aorta is imaged on the axial and coronal plane using a T1-weighted breath hold sequence with fat suppression. Image interpretation was done with the aid of a computer workstation, on which individual source images were analyzed and postprocessing techniques were performed, such as multiplanar volume reformation and MIP reformation.

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6 In our patients, MR angiography provided highquality images, it correctly indicated the size, location of the aneurysm and its relationship with aortic side branches in the case with thoracic aneurysm, and with the renal and iliac arteries in the 3 cases with abdominal aneurysm. It evaluated the proximal and distal extent of the aneurysm. MR imaging provides all the necessary information prior to surgical or endovascular gestures: Evaluation of the aneurysm sac and neck and the extent of the aneurysm.

7 Patient 1: Saccular aneurysm of the aortic arch in a 53-year-old man. Coronal and axial enhanced T1-weighted FAT SAT MR image showing an aneurysm of the ascending aorta with an intraluminal thrombosis (methemoglobin).

8 Patient 1: Axial T2 weighted FAT SAT MR image at the same level. Patient 1: 3D reconstrution : Aneurysmal neck visualizated just before the emanating of the brachiocephalic artery.

9 Images obtained in a 47-year-old man with an infrarenal aortic aneurysm. Patient 2: Axial and coronal enhanced T1 weighted MR image showing the abdominal aneurysm with an intraluminal thrombosis.

10 Patient 2 : 3D MR angiography demonstrates the abdominal aortic aneurysm (AAA) and showing the extension to the right common iliac artery.

11 Patient 3 : Infrarenal abdominal aneurysm in a 44 year-old woman. Axial and coronal MIP reconstrution images which shows an abdominal aneurysm with intraluminal thrombosis.

12 Patient 3 : Coronal and oblique MIP images from 3D MRA showing an infrarenal abdominal aneurysm with circumferential parietal thrombosis.

13 An AAA in a 73 year-old woman. Patient 4: Axial T2 weighted FAT SAT MR image showing an infrarenal abdominal aneurysm. Patient 4 : Axial T1 weighted FAT SAT MR image at the same level.

14 Patient 4 : 3D reconstruction showing a tortuous aorta with an AAA.

15 RESULTS

16 MR angiography showed wall thickening of the aorta in 2 cases. Thickened wall is enhanced on gadolinium-enhanced images. These findings suggest active inflammation. MR angiography showed renal stenosis in 2 patients. MRA studied the aorta in tri-dimensional plans and showed all parietal irregularities and luminal abnormalities (thrombosis).

17 Patient 1: Takayasu s arteritis in a 31- year-old woman. Axial T1-weighted MR images showing wall thickening of the descending aorta which enhanced after gadolinium injection.

18 Patient 2:Takayasu s arteritis in a 34-yearold woman. Axial T2-weighted MR images showing wall thickening of the ascending aorta.

19 Patient 2: 3D reconstruction images show two long and irregular stenotic segments of the descending aorta, initial abdominal aorta and infrarenal aorta.

20 Patient 2: coronal MIP image : wall thikening responsible for extensive aortic narrowings. Patient 2: cine MR image at the same level.

21 Patient 1: Patient 3: Oblique and sagital enhanced 3D MR angiography images of a 35-year-old woman: Irregular dilatation of the thoracic aorta.

22 Patient 3: Axial T2 weighted image in the same patient shows dilatation of the ascending and descending thoracic aorta.

23 Patient 4: 3D GE- MRA images in a 30- year-old woman show a long iregular stenotic segment of the infrarenal abdominal aorta.

24 Patient 4: Axial enhanced T1 weighed images showing aorta wall thickening enhancement after gadolinium injection.

25 Patient 5: a 15 year-old woman with Takayasu s arteritis. MRA images with 3D MIP reconstruction show wall thikening of the aorta with a complete occlusion of the right renal artery and a left collateral vessel (Riolan artery: inconstant artery that connects the left colic branch of the inferior mesenteric artery with the middle branch of the superior mesenteric artery).

26 Patient 6: another 45 year-old woman with the same findings ( patient 5).

27 RESULTS

28 In the 3 patients with aortic dissection, two had a type III dissection and one a type I. MR angiography correctly diagnosed three patients with aortic dissection. The type of dissection was correctly interpreted on gadolinium-enhanced MR images in all patients. The intimal flap was detected by MR imaging as a linear, medium-intensity structure separating the true and false lumina.

29 Patient 1: Type I aortic dissection in a 42 year-old man. T2-weighted axial MR image shows the intimal flap, which is bounded on both sides by dark flow voids in both the true and false lumina. Enhanced T1 weighed MR image at the same axial level.

30 Patient 1: MIP reconstruction images show the intimal flap.

31 Patient 1: Axial MIP image of MRA shows the intimal flap.

32 Patient 1: 3 D gadolinium enhanced MR angiography images reveal the extent of the aortic dissection which involve the entire descending thoracic aorta and abdominal aorta, the visceral arteries depend on the true lumen.

33 Coeliac trunk Superior mesenteric artery Patient 1: Axial reconstructed images: The visceral arteries depend on the true lumen. Renal arteries

34 Patient 2: Type IIIb aortic dissection in a 56 year-old woman. Axial T2 weighted MR image shows the intimal flap. Axial T2 weighted MR image shows an intraluminal thrombosis.

35 Patient 3: Type IIIb aortic dissection in a 45 year-old man. Axial T2 weighted MR image shows the intimal flap. Sagital MIP MRA image shows the intimal flap. 3 D MIP MRA image shows the true and the false lumens.

36 In the patient with aortic coarctation, threedimensional gadolinium-enhanced MR angiography correctly identified the site of coarctation and evaluated the degree of aortic narrowing. MR angiography also demonstrated collateral vessels, including dilated intercostal and internal mammary arteries, indicating that the coarctation were hemodynamically significant.

37 A 17 year-old man with aortic coarctation. 3 D MIP MRA images show the aortic coarctation.

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39 MRA is more suitable in medically stable patients, does not involve nephrotoxic contrast agent or ionizing radiation, and offers greater ease and speed of postprocessing. In clinical practice, contrast-enhanced MR angiography can provide high-quality imaging data suitable for 3D reconstructions. It also has excellent spatial and contrast resolution and allows studies to be performed in multiple vascular phases, making it valuable for the diagnosis and of aortic disorders and in providing information that is helpful for treatment planning. Spin-echo and cine MR imaging are the basics sequences but they have some limitations.

40 3D GE-MRA is a recently developed angiographic technique that can substantially improve the resolution, signal-to-noise ratio, speed, and overall quality of vascular MR imaging. Unlike spin-echo and cine MR imaging, 3D MRA achieves its image contrast and hence its angiographic information from the T1-shortening effect of gadolinium on blood. It is minimally degraded by flow-related artifacts. The distribution of gadolinium throughout the aortic lumen and its vascular connections permits appreciation of subtle aortic wall abnormalities such as mural thrombus or penetrating ulcer, findings that may not always be apparent with other MR imaging techniques.

41 AORTIC DISSECTION

42 Introduction: Aortic dissection is characterised by separation of the layers of the aortic wall due to extraluminal blood that has entered the aortic wall through an intimal tear. Tears are seen at areas of high stress (the anterior aortic wall just above the aortic valve (66%), and the posterior wall of the proximal descending aorta (33%)). When blood enters through an intimal tear it passes longitudinally along the tunica media separating the intima from the adventitia. Despite a reduction in its incidence as a result of improved pharmacological control of hypertension. Without prompt diagnosis and treatement, aortic dissection is rapidly fatal. Therefore, expeditious radiologic confirmation of the suspected diagnosis is crucial.

43 Classification: In the classic DeBakey system for classifying aortic dissection, three types are recognized: Type I dissection involves the entire aorta, Type II affects the ascending aorta, In type III only the descending aorta is affected. DEBAKEY classification

44 CLINICAL PRESENTATION: Typical presentation of acute dissection is with: Sudden onset, unexpected, intense pain in the interscapular region radiating to the lower back or abdomen. Patients are typically hypertensive middle-aged or elderly men. Differential diagnoses include myocardial ischaemia and abdominal aortic aneurysm.

45 Imaging findings: Ultrasonography is widely available and can be used even in relatively unstable patients. However, it has limited diagnostic accuracy and cannot provide three-dimensional (3D) display images for treatment planning. Both computed tomographic (CT), angiography and 3D contrast material enhanced magnetic resonance (MR) angiography can accurately demonstrate aortic dissection. MRI is capable of direct multiplanar imaging, a feature that often increases the technique's sensitivity and its specificity for a particular plane of dissection. With the use of spin-echo MRI techniques, the intimal flap produced by aortic dissection is depicted as a linear structure of medium intensity, separating 2 flow voids (of low signal intensity) that represent the true and false lumina. Cardiac gating improves the anatomic detail still further by eliminating the edge-blurring effects of cardiac pulsation on both the intimal flap and the vessel walls. The multiplanar capability of MRI has proved to be quite useful for evaluating the relationship of an aortic dissection to the arch vessels and other branch vessels and for indicating the extent, and thus the type, of dissection.

46 AORTIC ANEURYSM

47 Introduction: AA is a relatively common, potentially life-threatening condition. It has a wide spectrum of presentations and should be considered in the differential diagnosis for a number of symptoms. AA is usually the result of degeneration in the media of the arterial wall, resulting in a slow and continuous dilatation of the lumen of the vessel. Thoracic aneurysm Abdominal aneurysm 2types:

48 Imaging: MR angiography provides highquality images, its correctly indicates the measurements, location of the aneurysm and it relationship with aortic side branches, renal and iliac arteries. MRA evaluates the proximal and the distal extent of the aneurysm. It can show the intraluminal thrombosis. Imaging is useful for detection and follow-up of nonsurgical aneurysms, presurgical evaluation of aneurysms (evaluation of the aneurysm sac and neck, iliac and visceral arteries, and adjacent organs) and postsurgical follow-up (detection of postoperative complications).

49 TAKAYASU ARTERITIS

50 Introduction: Takayasu arteritis is an inflammatory arteritis affecting large vessels, predominantly the aorta and its main branches. Thickening of the vessel wall is an early hallmark of the disease and leads to stenosis, thrombosis, and sometimes aneurysm formation.

51 Classification: Type I branches of the aortic arch. Type IIa ascending portion of the aorta and/or the aortic arch. Type IIb descending thoracic aorta (with or without involvement of the ascending aorta) or the aortic arch with its branches. Type III concomitant involvement of the descending thoracic aorta, the abdominal aorta, and/or the renal arteries. The ascending aorta and the aortic arch and its branches are not involved. Type IV abdominal aorta and/or the renal arteries. Type V is a generalized type, with combined features of the other types. System for classifying Takayasu arteritis according to the site of involvement.

52 Clinical presentation: TA has traditionally been divided into an early, "prepulseless" systemic phase, and a late, occlusive phase. In the early systemic phase, diagnosis is difficult and symptoms are usually nonspecific and constitutional, including fever, myalgias, weight loss, and arthralgias. In the occlusive phase, ischemic symptoms dominate, including angina, claudication, syncope, and visual impairment. Late-phase TA may be further subclassified as classic pulseless disease (type 1), a mixed type (type 2), an atypical coarctation type (type 3), and a dilated type (type 4). Most patients present with a form of late-phase disease.

53 Imaging: MRA can demonstrate thickening of the vessel wall, which may be the earliest manifestation of the disease, occurring before stenosis and dilatation. MR imaging in particular allows better soft-tissue differentiation and can show other signs of inflammation, including mural edema and increased mural vascularity.

54 Imaging: MRI Features in the Acute Phase: Findings of TA on MRI include mural thrombi, signal alterations within and surrounding inflamed vessels, fusiform vascular dilation, thickened aortic valvular cusps, multifocal stenoses, and concentric thickening of the aortic wall. MRI may also reveal pericardial effusions and signal alterations within the pericardial sac, representing fluid and granulation tissue. Significant findings of the acute phase of TA are wall thickening of the aorta and pulmonary artery.thickened wall is enhanced on gadolinium-enhanced images.these findings suggest active inflammation. Sometimes, occlusion of the aortic branches or pulmonary artery or both is seen in the acute phase. Rarely, pseudoaneurysm formation occurs as in the acute phase.

55 Imaging: MRI Features in the Late Phase: Significant findings of the late phase of TA include diffuse narrowing of the descending thoracic and abdominal aorta. Dilatation occurs most commonly in the ascending aorta. MR angiography depists these findings well. Cine MRI depists aortic regurgitation caused by dilatation of the ascending aorta. Stenotic lesions of aortic branches and pulmonary artery commonly occur in the late phase. The lesions typically occur in the proximal portions of the branches. Stenosis, the most common finding, involves all arteries arising from the aorta, most commonly the common carotid and subclavian arteries.

56 Imaging: MRI Features in the Late Phase: Occlusion is the second most common finding. Abrupt occlusion, abrupt transition to collateral vessels, and flameshaped termination are characteristic. In the abdominal aorta, the renal artery is the most frequently involved branch. Pulmonary artery involvement is relatively high, with an estimated occurrence rate of 50 80%. Pulmonary perfusion scintigraphy or conventional angiography or both, including digital subtraction angiography, are useful methods for detecting obstructive changes of the pulmnary artery. MR angiography and MR perfusion imaging can also depist these findings. TA is also associated with aortic dissection and pseudoaneurysm formation in the late phase. MR angiography is also useful for evaluation of bypass graft.

57 Aortic coarctation

58 Coarctation of the aorta is a complex cardiac lesion that requires careful follow-up care through adulthood and pregnancy. Coarctation of the aorta is a narrowing of the aorta most commonly found just distal to the origin of the left subclavian artery. Most patients with coarctation have juxtaductal coarctation. Older terms such as preductal (infantile-type) or postductal (adult-type) are often misleading. MRA diagnoses the focal aortic narrowing, It also demonstrated collateral vessels, including dilated intercostal and internal mammary arteries, indicating that the coarctation were hemodynamically significant.

59 MARFAN SYNDROME

60 Marfan syndrome is an inherited connective-tissue disorder transmitted as an autosomal dominant trait. It is noteworthy for its worldwide distribution, relatively high prevalence, clinical variability, and pleiotropic manifestations, some of which are life threatening. Cardinal features of the disorder include tall stature, ectopia lentis, mitral valve prolapse, aortic root dilatation, and aortic dissection. About three quarters of patients have an affected parent; new mutations account for the remainder. Marfan syndrome is fully penetrant with marked interfamilial and intrafamilial variability. MR imaging showed dilation of the aortic root or ascending aorta, or both, in all five patients with Marfan syndrome, MR imaging clearly showed the dilated ascending aorta and normal descending aorta coursing transversely across the chest. One patient also had a type A aortic dissection, subsequently confirmed by angiography. In an additional patient with clinically suspected aortic dissection, both MR images and a subsequent angiogram showed no evidence of a dissection.

61 ATHEROSCLEROSIS

62 Atherosclerosis is a disease of large and mediumsized muscular arteries and is characterized by endothelial dysfunction, vascular inflammation, and the buildup of lipids, cholesterol, calcium, and cellular debris within the intima of the vessel wall. This buildup results in plaque formation, vascular remodeling, acute and chronic luminal obstruction, abnormalities of blood flow, and diminished oxygen supply to target organs. MRA can determines the degree of stenosis and achieves the plaque characterization.

63 MR angiography is a fast, accurate, and noninvasive technique that may prove to be the optimal imaging modality in medically stable patients with aortic disorders.

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