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Developmental Abnormalities

MRI permits an excellent workup of the anatomic and physiologic status particularly as regards congenital cardiovascular malformations of the aorta. Since children or young adults most frequently require evaluation, the lack of ionizing radiation and the excellent safety profile of the applied MR contrast agents are a considerable advantage when compared with other diagnostic modalities. Moreover, since patients with congenital cardiovascular malformations need regular follow-up, it is important to reduce to a minimum the number of examinations that require ionizing radiation.

Aortic Coarctation

Coarctation of the aorta has a male predominance of 4 to 1. Two forms can be distinguished: the localized postductal coarctation (Fig. 3a, b) and the preductal or tubular hypoplasia of the aortic arch.

In the localized form a short discrete narrowing of the aorta close to the ligamentum arterio-sum can be found. Although concomitant cardiac anomalies are uncommon in this form of aortic coarctation, there is an association with bicuspid aortic valve in 25-50% of cases. Diagnosis is often made in young adults but sometimes even later in life (Fig. 4). In contrast, in the preductal, infantile form of aortic coarctation a hypoplasia of a longer segment of aortic arch after the origin of the innominate artery is found [14]. This form is often associated with a variety of coexisting cardiac anomalies as described in Chapter VIII "MRA in pediatric patients".

Collateral supplies in aortic coarctation are often easily depicted on CE MRA and may derive from the intercostal and internal mamarian arteries, the scapular arteries, and the lateral thoracic and transverse cervical arteries (Fig. 5a-c). MRI in coarctation not only allows depiction of the involved segment enabling determination of the length and diameter of the aorta, but may also per-

Postductal Coarctation Collateral
Fig. 3a, b. Localized postductal coarctation in an 18-year old man. Dilatation of the left subclavian artery (arrow) and a stenosis of the aorta can be seen in a. However, the degree of the stenosis (arrow) is much better appreciated on the subvolume MIP image (b)

Fig. 4. A 68-year old male patient with hypertension and increasing claudication (Gd-BOPTA, 0.1 mmol/kg). The contrast enhanced MRA study shows coarctation and a high grade stenosis of the aorta distal to the origin of the left subclavian artery (arrow) and involving the left subclavian artery (arrowhead). This finding is important for surgery since part of the arch has to be reconstructed

Aorta Coarctation Surgery

Fig. 5a-c. Depiction of collateral supplies in aortic coarctation in a 17-year old female (Gd-BOPTA, 0.1 mmol/kg). The CE MRA study reveals collaterals from the intercostals, internal mamarian arteries and lateral thoracic arteries (arrowsin a), as well as collaterals from the scapular arteries and transverse cervical arteries (arrows in b). Note that the degree of stenosis is best displayed on multiplanar reconstructions following the long axis of the aorta (arrowin c)

Fig. 5a-c. Depiction of collateral supplies in aortic coarctation in a 17-year old female (Gd-BOPTA, 0.1 mmol/kg). The CE MRA study reveals collaterals from the intercostals, internal mamarian arteries and lateral thoracic arteries (arrowsin a), as well as collaterals from the scapular arteries and transverse cervical arteries (arrows in b). Note that the degree of stenosis is best displayed on multiplanar reconstructions following the long axis of the aorta (arrowin c)

Aortic Coarctation Repair

Fig. 6a, b. Follow up study in a patient after surgical repair of aortic coarctation (Gd-BOP-TA, 0.1 mmol/kg). Neither the MIP image (a) nor the volume rendered image (b) from the CE 3D MRA dataset reveal a residual stenosis although some irregularities of the aortic wall due to patch angioplasty are apparent. Note the persisting dilatation of the left subclavian artery (arrowin a) and the kinking of the thoracic aorta (arrowin b)

Fig. 6a, b. Follow up study in a patient after surgical repair of aortic coarctation (Gd-BOP-TA, 0.1 mmol/kg). Neither the MIP image (a) nor the volume rendered image (b) from the CE 3D MRA dataset reveal a residual stenosis although some irregularities of the aortic wall due to patch angioplasty are apparent. Note the persisting dilatation of the left subclavian artery (arrowin a) and the kinking of the thoracic aorta (arrowin b)

Kinking Aorta

Fig. 7a, d. Pre-intervention (a, b) and post-intervention (c, d) evaluations of a patient with aortic coarctation undergoing intraluminal intervention and stent placement. a and b show coarctation of the thoracic aorta a few centimeters distal to the origin of the subclavian artery. Due to the rather long distance from the subclavian artery stent placement was planned for treatment of the coarctation. On the post-interventional MIP image almost complete signal loss is apparent in the area of the stent (arrow in c). However, if multiplanar reconstructions are made from the source data the area of the stent can be evaluated on MR images. In this case no hemodynamic relevant residual stenosis is visible (arrows in d)

Fig. 7a, d. Pre-intervention (a, b) and post-intervention (c, d) evaluations of a patient with aortic coarctation undergoing intraluminal intervention and stent placement. a and b show coarctation of the thoracic aorta a few centimeters distal to the origin of the subclavian artery. Due to the rather long distance from the subclavian artery stent placement was planned for treatment of the coarctation. On the post-interventional MIP image almost complete signal loss is apparent in the area of the stent (arrow in c). However, if multiplanar reconstructions are made from the source data the area of the stent can be evaluated on MR images. In this case no hemodynamic relevant residual stenosis is visible (arrows in d)

mit estimation of the pressure gradient through evaluation of the maximum flow velocity [15].

Not only diagnosis but also post surgical or post interventional follow-up is of importance (Fig. 6a, b) either to detect residual stenosis of the aorta or to evaluate newly developed stenosis due to scar tissue formation. Furthermore, evaluation of post interventional procedures e.g. dilatation of the stenosis or stent placement (Fig. 7a-d) is necessary to detect intramural hemorrhage, dissection or aneurysm formation (Fig. 8a-e).

If a diagnosis of coarctation is made, the aortic valve should always be evaluated as well in case a concomitant bicuspid aortic valve is present (see Fig. 18).

What The Bicuspid Valve

Fig. 8a-e. Aneurysm formation in a patient with recurrent coarctation (Gd-BOPTA, 0.1 mmol/kg). The MIP image (a) reveals some irregularities of the aortic wall (arrows) in the area of the former coarctation but no signs of a residual stenosis. However, if volume rendering is used for evaluation of the anatomy (b, c) a tremendously irregular aortic wall and aneurysm formation is demonstrated (arrow in b) together with a residual stenosis (arrowin c). The stenosis is confirmed on axial reformations of the CE 3D MRA dataset (arrow in d) and can be further evaluated by CINE imaging (e)

Fig. 8a-e. Aneurysm formation in a patient with recurrent coarctation (Gd-BOPTA, 0.1 mmol/kg). The MIP image (a) reveals some irregularities of the aortic wall (arrows) in the area of the former coarctation but no signs of a residual stenosis. However, if volume rendering is used for evaluation of the anatomy (b, c) a tremendously irregular aortic wall and aneurysm formation is demonstrated (arrow in b) together with a residual stenosis (arrowin c). The stenosis is confirmed on axial reformations of the CE 3D MRA dataset (arrow in d) and can be further evaluated by CINE imaging (e)

Fig. 9a, b. Incidental finding of a double aortic arch in a 64-year old patient. On conventional thorax x-ray a widening of the upper mediastinum was noted and the patient underwent MRI for further evaluation. The volume rendered images of the CE 3D MRA dataset (Gd-BOPTA, 0.1 mmol/kg) show a complete double aortic arch. This can already be noted on an anterior-to-posterior view (a) but is even better displayed if a cranio-caudal view (b) is obtained. Note the separate anterior origin of the two common carotid arteries (arrows) and the posterior origin of the two subclavian arteries (arrowheads)

Arch Anomalies

Anomalies of the aortic arch such as double aortic arch (Fig 9a, b), aberrant right subclavian artery (Fig 10a-c, 11 a-c), right sided aortic arch (Fig 12a, b) and patent ductus arteriosus (Fig 13a-c) are easily and accurately diagnosed on contrast enhanced

MRI, as is aortic pseudocoarctation (Fig 14 a,b). In some of these instances patients may be asymptomatic with the diagnosis made due to an incidental finding of, for example, widened upper mediastinum on conventional thorax x-ray.

Resonant Relationship Images

Fig. 10a-c. Aberrant right subclavian artery (Lusoria artery) in a 72-year old male. Whereas the anatomic relationship between the supraaortic vessels is hard to identify on the MIP image (a), the volume rendered images in anterior-posterior (b) and posterior-anterior (c) direction clearly depict an aberrant right subclavian artery (arrows) arising as the last vessel from the aortic arch and passing to the opposite site. Note in addition the common trunk of the carotid arteries branching first from the aortic arch (arrowhead)

Fig. 10a-c. Aberrant right subclavian artery (Lusoria artery) in a 72-year old male. Whereas the anatomic relationship between the supraaortic vessels is hard to identify on the MIP image (a), the volume rendered images in anterior-posterior (b) and posterior-anterior (c) direction clearly depict an aberrant right subclavian artery (arrows) arising as the last vessel from the aortic arch and passing to the opposite site. Note in addition the common trunk of the carotid arteries branching first from the aortic arch (arrowhead)

Abberant Right Subclavian Artery

Fig. 11a-c. Aberrant right subclavian artery with development of an aneurysm. Again the relationship between the supraaortic vessels is much better appreciated on the volume rendered image (b) than on the standard MIP reconstruction (a). As in Fig. 10 an aberrant right subclavian artery (arrow) arises as the last vessel from the aortic arch and passes to the opposite site. However in this case a large aneurysm (arrow) of the aberrant right subclavian artery with thrombus formation can be noted on the conventional post contrast T1w axial image (c). Furthermore note the esophagus (arrowhead and the trachea (asterisk) anterior to the aberrant right subclavian artery

Fig. 11a-c. Aberrant right subclavian artery with development of an aneurysm. Again the relationship between the supraaortic vessels is much better appreciated on the volume rendered image (b) than on the standard MIP reconstruction (a). As in Fig. 10 an aberrant right subclavian artery (arrow) arises as the last vessel from the aortic arch and passes to the opposite site. However in this case a large aneurysm (arrow) of the aberrant right subclavian artery with thrombus formation can be noted on the conventional post contrast T1w axial image (c). Furthermore note the esophagus (arrowhead and the trachea (asterisk) anterior to the aberrant right subclavian artery

Abberant Right Subclavian Artery

Fig. 12a, b. Right aortic arch giving rise to an aberrant left trunk (Gd-BOPTA, 0.1 mmol/kg). On routine x-ray of the thorax a right descending aorta was noted and the patient was transferred to MRI to further evaluate the vascular structures. The MIP image (a) shows the right descending aorta together with a large vessel that passes to the left (arrow). The relationship between the vessels is again much better appreciated on the surface rendered image (b) which clearly demonstrates that first the right common carotid artery, second the right subclavian artery and last the atypical trunk that gives separate rise to the left common carotid, subclavian and vertebral artery branch from the right aortic arch

Fig. 13a-c. CE MRA study (Gd-BOPTA, 0.1 mmol/kg) of a patent ductus arteriosus in a 16-year old female patient. A large vessel (arrows) connecting the descending aorta with the pulmonary trunk can be identified on the MIP projection (a). The volume rendered images (b, c) identify the site of connection between the patent ductus arteriosus and the pulmonary trunk (arrowin c) and generally reveal more details of the exact anatomic situation in this complex anatomy

Fig. 13a-c. CE MRA study (Gd-BOPTA, 0.1 mmol/kg) of a patent ductus arteriosus in a 16-year old female patient. A large vessel (arrows) connecting the descending aorta with the pulmonary trunk can be identified on the MIP projection (a). The volume rendered images (b, c) identify the site of connection between the patent ductus arteriosus and the pulmonary trunk (arrowin c) and generally reveal more details of the exact anatomic situation in this complex anatomy

Pseudocoarctation Angiogram

Fig. 14a, b. Aortic pseudocoarctation in a 72-year old male patient. A dilatation of the descending aorta (arrowsin a) can be noted on the MIP reconstruction (a) of the 3D CE MRA dataset (Gd-BOPTA, 0.1 mmol/kg). On the volume rendered image (b) a slight narrowing of lumen of the aorta (arrow in b) can be noted with proximal elongation of the vessel which corresponds to aortic pseudocoarctation

Fig. 14a, b. Aortic pseudocoarctation in a 72-year old male patient. A dilatation of the descending aorta (arrowsin a) can be noted on the MIP reconstruction (a) of the 3D CE MRA dataset (Gd-BOPTA, 0.1 mmol/kg). On the volume rendered image (b) a slight narrowing of lumen of the aorta (arrow in b) can be noted with proximal elongation of the vessel which corresponds to aortic pseudocoarctation

Aortic Aneurysm

Aneurysms of the thoracic aorta can be classified according to their shape as either saccular, fusiform or dissecting. The latter are discussed in a separate subchapter. Aneurysms of the thoracic aorta can be distinguished by their location. The most frequent aortic aneurysms are found in the sinus of valsalva, the ascending aorta where they are typically associated with valvular disease, the aortic arch and in the area of the descending aorta. As regards etiology, on rare occasions aortic aneurysms might be congenital. More typically, they are due to atherosclerotic disease, trauma or inflammation.

If the diameter of the aorta is below 4 cm the condition is referred to as aortic ectasia. Conversely, if the diameter exceeds 4 cm the dilatation is generally considered an aneurysm. If an aneurysm of the ascending aorta exceeds a diameter of 5 cm surgical repair has to be considered (Fig. 15a, b), since the risk of rupture is significantly increased. Likewise, aneurysms that are saccular or which develop due to inflammation, as well as aneurysms that increase in diameter by approximately 1 cm over the course of a one year period, should be considered potential surgical candidates since these types of aneurysm have an increased risk of rupture as well [16,17].

In cases in which the descending aorta is in-

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Mra Aortic Arch Aneurysm

Fig. 16. MIP reconstruction of a 3D CE MRA dataset (Gd-BOPTA, 0.1 mmol/kg) of a patient with aortic aneurysm. In contrast to the case in Fig. 15 in this case the aortic arch also shows dilatation (arrowheads) and the brachiocephalic trunk should at least be described as ectatic (arrow). Note that the supraaortic vessels up to the carotid bifurcation can be evaluated in the same study

Fig. 16. MIP reconstruction of a 3D CE MRA dataset (Gd-BOPTA, 0.1 mmol/kg) of a patient with aortic aneurysm. In contrast to the case in Fig. 15 in this case the aortic arch also shows dilatation (arrowheads) and the brachiocephalic trunk should at least be described as ectatic (arrow). Note that the supraaortic vessels up to the carotid bifurcation can be evaluated in the same study volved endoluminal treatment by aortic stent placement may be considered. However, for accurate planning of stent placement and stent size CT imaging should also be considered to allow for exact measurement of the diameters of the aorta above and below the aneurysm as well as to detect extensive calcification [2].

One big advantage of 3D CE MRA is the large field of view (FOV) which with a single contrast agent injection permits evaluation of both the aorta and the relationship of the aneurysm to branching vessels (Fig. 16). Several studies correlating 3D CE MRA with conventional angiography and surgical specimen have shown an almost 100% accuracy for assessing the size and extent of aortic aneurysms and for evaluating their relationship to

Fig. 15a, b. MIP reconstruction (a) and volume rendered image (b) of a 3D CE MRA dataset (Gd-BOPTA, 0.1 mmol/kg) of a patient with an aneurysm of the ascending aorta due to aortic valve stenosis. Note the significant dilatation of the ascending aorta (arrows) which was measured at 5.2 cm on multiplanar reconstructions perpendicular to the long axis of the aorta. Due to the already large diameter and a progressively increasing diameter of more than 0.5 cm over a one year period surgical reconstruction of the aortic valve and reconstruction of the ascending aorta was performed. Note that the aorta at the level of the origin of the brachiocephalic trunk as well as the trunk itself is not dilated meaning that reconstruction of the arch does not have to be performed aortic branches. To further increase the diagnostic value of CE MRA in patients with aortic aneurysms luminal imaging of the arterial phase of the 3D CE MRA should be combined with cross-sectional imaging either pre or post contrast agent injection (Fig. 17a-c). If post contrast images are acquired they easily allow for differentiation between the patent lumen of an aortic aneurysm and wall thrombosis. Additionally, assessment of inflammation surrounding the aorta, inflammation of the wall and evaluation of surrounding soft tissue is made possible and may provide important additional information [18].

As mentioned above, aneurysms of the ascending aorta are most often caused by valvular disease. Therefore, if an ectasia or aneurysm of the ascending aorta is identified, CINE imaging of the aortic valve and the ascending aorta should be performed to detect congenital malformation of the aortic valve e.g. a bicuspid aortic valve (Fig. 18a-d), or to diagnose stenosis, insufficiency or a combination of both conditions (Fig. 19a, b).

Finally, as discussed previously, MRI allows for quantification of pressure gradients over the aortic valve as well as quantification of the regurgitation fraction in patients with aortic insufficiency.

Aortic Dissection

In contrast to the increased diameter of the aorta in aortic aneurysms the underlying anatomic abnormality in aortic dissection is a spontaneous longitudinal separation of the aortic intima and adventitia. This occurs due to circulating blood gaining access to the media of the aortic wall causing it to split in two. The separation of the intima and the adventitia of the aortic wall results in a dissection membrane which is the typical imaging finding of aortic dissection (Fig. 20a-c). Dissection a

Mra Aortic Dissection

Fig. 17a-c. Kinking and aneurysm formation of the descending aorta in a 74-year old patient. The MIP reconstruction (a) of the CE 3D MRA dataset (Gd-BOpTA, 0.1 mmol/kg) shows an elongation of the descending aorta with an almost ascending portion of the aorta (arrow) just above the level of the diaphragm. On the volume rendered image (b) the anatomy can be appreciated more readily and irregularities of the surface of the aortic lumen can be identified. The unenhanced T1w precontrast image (c) clearly identifies a large aneursym of the descending aorta (arrows). Partial thrombosis of this aneurysm is apparent and the still perfused part (asterisk) demonstrates an almost normal diameter, as indicated by the low signal intensity due to flow void. This case clearly demonstrates the importance of combining CE MRA studies with cross sectional imaging

Fig. 17a-c. Kinking and aneurysm formation of the descending aorta in a 74-year old patient. The MIP reconstruction (a) of the CE 3D MRA dataset (Gd-BOpTA, 0.1 mmol/kg) shows an elongation of the descending aorta with an almost ascending portion of the aorta (arrow) just above the level of the diaphragm. On the volume rendered image (b) the anatomy can be appreciated more readily and irregularities of the surface of the aortic lumen can be identified. The unenhanced T1w precontrast image (c) clearly identifies a large aneursym of the descending aorta (arrows). Partial thrombosis of this aneurysm is apparent and the still perfused part (asterisk) demonstrates an almost normal diameter, as indicated by the low signal intensity due to flow void. This case clearly demonstrates the importance of combining CE MRA studies with cross sectional imaging

Aortic Dissection Unenhanced Study

■I Fig. 18a-d. Aneurysm of the ascending aorta in a 25-year old patient with bicuspid aor-I tic valve. The MIP reconstruction of the 3D CE MRA dataset (Gd-BOPTA, 0.1 mmol/kg) in anterior-posterior (a) and lateral (b) views shows dilatation of the ascending aorta (ar-I rows). Since aortic valve disease is the main reason for aortic aneurysm formation of the I ascending aorta in this age group further evaluation of the aortic valve was performed. A I True FISP CINE sequence parallel to the axis of the ascending aorta (c) shows stenosis (arrowheads) and a jet phenomenon (arrow) at the aortic valve. A CINE image perpendicular I to the aortic root at the level of the aortic valve (d) clearly displays the so-called "fish-^ mouth-appearance" of a bicuspid aortic valve (arrow)

Fig. 19a, b. A volume rendered CE MRA image (Gd-BOPTA, 0.1 mmol/kg) of the thoracic aorta (a) shows tremendous dilatation of the ascending aorta (arrow) in a 38-year old patient. The corresponding True FISP CINE sequence (b) parallel to the axis of the ascending aorta in this case shows a diastolic retrograde jet over the aortic valve (arrow) indicating aortic valve insufficiency. This can further be evaluated by phase-contrast GRE images with which a quantification of the regurgitation volume is possible

Fig. 19a, b. A volume rendered CE MRA image (Gd-BOPTA, 0.1 mmol/kg) of the thoracic aorta (a) shows tremendous dilatation of the ascending aorta (arrow) in a 38-year old patient. The corresponding True FISP CINE sequence (b) parallel to the axis of the ascending aorta in this case shows a diastolic retrograde jet over the aortic valve (arrow) indicating aortic valve insufficiency. This can further be evaluated by phase-contrast GRE images with which a quantification of the regurgitation volume is possible

Fig. 20a-c. 3D CE MRA study in a patient with aortic dissection (Gd-BOPTA, 0.1 mmol/kg). The CE MRA study of the thorax (a, b) shows dissection of the descending aorta with early filling of the true lumen (arrowin a) and delayed filling of the false lumen (arrowhead in a). On a multiplanar reconstruction (b) following the orientation of the aortic arch the beginning of the dissection (arrowin b) just distal to the origin of the left subclavian artery (arrowheadin b) can be identified indicating a Stanford Type B dissection. Further identification of the true (arrow) and false (arrowhead lumens is achieved in additional study of the abdomen (c). Note that the true lumen ends in the right iliac artery and that the false lumen ends in the left iliac artery

Fig. 20a-c. 3D CE MRA study in a patient with aortic dissection (Gd-BOPTA, 0.1 mmol/kg). The CE MRA study of the thorax (a, b) shows dissection of the descending aorta with early filling of the true lumen (arrowin a) and delayed filling of the false lumen (arrowhead in a). On a multiplanar reconstruction (b) following the orientation of the aortic arch the beginning of the dissection (arrowin b) just distal to the origin of the left subclavian artery (arrowheadin b) can be identified indicating a Stanford Type B dissection. Further identification of the true (arrow) and false (arrowhead lumens is achieved in additional study of the abdomen (c). Note that the true lumen ends in the right iliac artery and that the false lumen ends in the left iliac artery may involve a localized area or the entire circumference of the aorta. Although predisposing underlying diseases include cystic media necrosis, Mar-fan's syndrome, Ehlers-Danlos syndrome, Turner's syndrome and Behcet disease among others, in the majority of patients no underlying syndrome can be found and the main pathomechanism is systemic hypertension. This is the underlying disease in approximately 60-90% of cases [19].

According to the Stanford Classification, aortic dissections may be categorized as Stanford Type A (70%) and Stanford Type B (20-30%) dissection, with Stanford Type A dissection affecting the ascending aorta +/- the aortic arch and Type B dissection beginning beyond the origin of the left subclavian artery.

In the DeBakey Classification Type I dissection represents a dissection of the ascending aorta and a portion of the aorta distal to the arch, Type II dissection involves only the ascending aorta, and Type III dissection involves only the descending aorta. In subtype III A of the DeBakey classification the dissection runs down to the level of the diaphragm while in subtype III B the dissection extends below the diaphragm [20].

From the clinical point of view an acute dissection is a dissection that is less than two weeks old while a chronic dissection is one that is more than two weeks old. In the majority of acute Type A dissections, CE MRA or MRI in general does not play an important role since urgent surgery is required as soon as the diagnosis is established. Typically, in the first hours after the onset of a Type A dissection the mortality rate per hour is approximately 8%. In contrast, in chronic Type A dissection MRI and MRA may provide very important clinical in formation. Similarly, MRA is appropriate for follow up of Type B dissections and for follow up of patients with reconstruction of the ascending aorta following Type A dissection with remaining dissection of the descending aorta [7].

The major questions which should be answered in the setting of aortic dissection are the exact localization and extent of the dissection, the localizations of entries and re-entries, and the involvement of branching vessels. Concerning branching vessels, the supraaortic vessels are of particular interest in Type A dissections while the mesenteric and renal arteries are of interest in Type B dissections. If the involvement of branching vessels cannot be excluded based on the arterial 3D CE MRA dataset, further evaluation with CINE imaging or with contrast enhanced T1w fat suppressed sequences such as VIBE sequences may be helpful.

Simple morphologic criteria can be used to distinguish between the true and the false lumen in aortic dissection. Typically, the true lumen is smaller and if black-blood imaging is performed the faster flowing blood in the true lumen shows complete flow void while the frequently very much slower flow in the larger, false lumen results in an intermediate signal. Occasionally, complete thrombosis of the false lumen occurs (Fig. 21a-c).

It is important to note that other types of dissections or aortic wall anomalies can be distinguished from classical aortic dissection. Examples include intramural hematoma (Fig. 22a-e) which may progress to classical aortic dissection, intimal tear, atherosclerotic ulcer (Fig. 23) and iatrogenic or traumatic dissections.

Atherosclerotic Disease

In atherosclerotic disease not only evaluation of the aorta but also evaluation of the supraaortic vessels is necessary (Fig. 24). Diseases associated with arteriosclerosis are aortic ulcers, kinking of the aorta and aneurysmatic widening of the thoracic aorta as well as stenosis or occlusion with and without elongation of the supraaortic vessels. Anatomy in arteriosclerotic disease of the supraaortic vessels can be complicated and 3D CE MRA generally gives excellent results (Fig. 25a-c).

Intimal Irregularities

Fig. 21a-c. Complete thrombosis of the false lumen in a patient with Stanford Type B dissection. Whereas only minor wall irregularities (arrows) can be noted on the MIP reconstruction (a) of the 3D CE MRA dataset (Gd-BOPTA, 0.1 mmol/kg), clear flattening of the perfused aortic lumen in several areas (arrows is apparent on the volume rendered image (b). This corresponds to complete thrombosis of the false lumen in Stanford Type B dissection which is clearly demonstrated on a True FISP CINE sequence at the level of the left atrium perpendicular to the axis of the descending aorta (c). Note the normal flow signal in the true lumen and the complete thrombosis of the false lumen (asterisk)

Steps Thrombosis

Fig. 21a-c. Complete thrombosis of the false lumen in a patient with Stanford Type B dissection. Whereas only minor wall irregularities (arrows) can be noted on the MIP reconstruction (a) of the 3D CE MRA dataset (Gd-BOPTA, 0.1 mmol/kg), clear flattening of the perfused aortic lumen in several areas (arrows is apparent on the volume rendered image (b). This corresponds to complete thrombosis of the false lumen in Stanford Type B dissection which is clearly demonstrated on a True FISP CINE sequence at the level of the left atrium perpendicular to the axis of the descending aorta (c). Note the normal flow signal in the true lumen and the complete thrombosis of the false lumen (asterisk)

Intramural Hematoma Thoracic

Fig. 22a-e. Intramural hematoma of the descending aorta progressing to a Stanford Type B dissection. The patient first presented with thoracic pain but cardiac infarction was excluded. A MIP reconstruction of a subsequent MRA study (a) revealed normal anatomy of the descending aorta. However an intramural hematoma (arrows) of the descending aorta was apparent on axial Tlw images of the thorax (b). One year later without experiencing another episodes of thoracic pain the patient came back for a follow up study (c-e) which revealed Stanford Type B dissection. The MIP reconstruction of the aortic arch (c) demonstrates the beginning of the dissection distal to the branching of the left subclavian artery (arrow). A complete MIP reconstruction of the thoracic vaculature (d) demonstrates the dissection membrane (arrows) descending in a spiral course into the abdominal aorta. An axial Tlw image (e) clearly shows the dissection membrane and no residual high SI of the aortic wall

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Aortic Arch Ulcer

Fig. 23. Arteriosclerotic ulcer in a 74-year old male patient. The contrast enhanced MRA study shows an arteriosclerotic ulcer of the descending aorta (arrow). Note in addition the strong enhancement of adjacent lung parenchyma (arrowheads) due to atelectasis and inflammation which can be misinterpreted as an inflammatory cause of the aortic ulcer

Fig. 23. Arteriosclerotic ulcer in a 74-year old male patient. The contrast enhanced MRA study shows an arteriosclerotic ulcer of the descending aorta (arrow). Note in addition the strong enhancement of adjacent lung parenchyma (arrowheads) due to atelectasis and inflammation which can be misinterpreted as an inflammatory cause of the aortic ulcer

Fig. 24. Subclavian steal syndrome in a 42-year old female patient. The CE MRA study (Gd-BOPTA, 0.1 mmol/kg) reveals complete occlusion of the left subclavian artery (arrows) which is now supplied by the left vertebral artery (arrowhead) in which a retrograde flow can be noted

Causes Subclavian Steal Syndrome

Fig. 25a, b. Arteriosclerosis of the aorta and the supraaortic vessels in a 72-year old male patient. The MIP reconstruction (a) of the contrast enhanced MRA study (Gd-BOPTA, 0.1 mmol/kg) reveals elongation and irregular wall formation of the aorta and to an even larger extent of the supraaortic vessels. Again the volume rendered image (b) better displays the anatomic situation. Note that both a patent (arroW and an occluded (arrowhead) aortocoronary bypass graft are displayed

Temporal Arteritis Mra

Fig. 26. Contrast enhanced MRA study (Gd-BOPTA, 0.1 mmol/kg) in a 32-year old patient with Takayasu arteritis. Note the occlusion of the right subclavian and vertebral arteries as well as the stenotic areas (arrows) of the right common carotid artery and the left subcla-vian artery

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Fig. 27a, b. A patient with advanced Takayasu arteritis. The CE MRA study of the thorax (Gd-BOPTA, 0.1 mmol/kg) shows massive involvement of the supraaortic vessels (arrowsin a). In addition almost complete occlusion of the infrarenal abdominal aorta (arrowin b) and occlusion of the right common iliac artery can be noted on a CE MRA study of the abdomen

Aortitis

Inflammation of the aorta, also referred to as aortitis, can occur as part of a vascular inflammation syndrome such as Takayasu arteritis (Fig. 26) or as a result of an infectious disease such as syphilitic aor-titis. Inflammation may also affect the periaortic tissue, in a similar way to that occurring in Or-mond's disease in the abdomen [21]. In such cases the luminal image of arterial phase CE MRA does not depict the surrounding disease. As a result of this and due to the fact that the luminal image does not say anything about the activity of an inflammatory process, T1w fat suppressed post contrast images should be acquired to visualize the enhancement of the involved tissue and to get some information concerning the activity of the disease. In Takayasu arteritis, which is also called pulseless dis ease, CE MRA is a very accurate non-invasive method to obtain a complete overview of the arterial status of a patient. As the name pulseless disease suggests, catheter angiography maybe very difficult due to the fact that no peripheral vessel can be catheterized to get access to the aortic lumen [18].

To distinguish between acute active inflammatory processes and more chronic diseases, a combination of T2w and post contrast T1w fat suppressed images is advisable. If high signal intensity is noted on both T2w and post contrast T1w fat suppressed images, this would tend to indicate an active inflammation. Conversely, if a low signal intensity of the involved tissue is noted on T2w images, this would tend to suggest the early stages of fibrosis and hence a more chronic form of disease. If no further enhancement or only slight enhancement is noted on post contrast T1w fat suppressed images, a diagnosis of complete fibrosis without any active inflammation can be made.

Regarding Takayasu arteritis it should be noted that this is the only form of aortitis that can lead to high grade stenosis or occlusion of the aorta (Fig. 27a, b). Therefore, if occlusion of the aorta is found, Takayasu arteritis has to be considered the underlying disease [6].

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