Korean Circ J.  2007 Aug;37(8):337-345. 10.4070/kcj.2007.37.8.337.

Radiological Imaging of Aortic Aneurysms

• Lee J

• KMID: 2029060
• DOI: http://doi.org/10.4070/kcj.2007.37.8.337

Abstract

The development of radiological equipment such as MDCT or ultrasonography has increased the diagnostic accuracy of aortic aneurysms and has allowed for improvements in surgical and interventional treatment techniques. However, the mortality and morbidity rate of aortic aneurysms has not decreased significantly. For this reason, there is continuous interest in radiological evaluations of aortic aneurysms. This report reviews the radiological image findings and useful indications for both the diagnosis and surveillance of aortic aneurysms. The popular radiological features of an aortic aneurysm are aortic expansion, combined atherosclerosis, intraluminal mural thrombus, perianeurysmal inflammation and fibrosis, and perianeurysmal hemorrhage due to rupture. As rupture is the most important complication of an aortic aneurysm, various signs of an impending rupture have been suggested. These include the following: a maximum aneurysmal diameter larger than the threshold value, a high expansion rate, periaortic sentinel hemorrhage, and a hyperattenuating crescent in the mural thrombus or aneurysmal wall. To acknowledge the impending rupture of an aortic aneurysm, careful depiction of the clues is indispensable.

Keyword

Aortic aneurysm; Tomography, computed, scanner; Magnetic resonance imagin

MeSH Terms

Aneurysm
Aortic Aneurysm*
Atherosclerosis
Diagnosis
Fibrosis
Hemorrhage
Inflammation
Mortality
Rupture
Thrombosis
Ultrasonography

Figure

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  Fig. 1 Imaging of an abdominal aortic aneurysm using 16-channel multi-detector computed tomography (MDCT) and post-processing techniques. A: scan planning on a scout image was from above the diaphragm down to the perineum, with a slice thickness of 5 mm. A total of 105 axial images were obtained using this plan. B: basic reconstruction of an axial image with a slice thickness of 5 mm shows an abdominal aortic aneurysm and intraluminal mural thrombus. Some calcification can be seen at the outer aneurysmal wall toward the mural thrombus. C: a three-dimensional reconstruction, volume rendering (VR) technique, showing an expanded lumen of the abdominal aortic aneurysm along with neighboring anatomical structures such as renal and iliac arteries. The distance between the upper end of the aneurysm and orifice of the right renal artery, the "proximal leg", was measured as 3.3 cm. Also noted is the wall calcification in the abdominal aortic aneurysm and both iliac arteries. D: the maximum intensity projection (MIP) technique contains three-dimensional information converted into a two-dimensional image. The sequential multiple angle display is useful for depicting the three-dimensional information. E: coronal reconstruction using multiplanar reformatting (MPR) clearly shows the relationship between the abdominal aortic aneurysm and renal arterial orifices. F: a curved MPR was produced along the whole length of the scanned aorta and iliofemoral artery. The displayed image shows a straightened aortoiliofemoral artery and cross-sectional area curve at the horizontally matched level.

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  Fig. 2 Magnetic resonance imaging (MRI) of an abdominal aortic aneurysm. A: a contrast-enhanced three-dimensional fast gradient echo technique acquired coronal image of an abdominal aortic aneurysm. The irregular luminal contour suggests the presence of atherosclerotic plaque. B: Post-processing of the raw image data, using maximum intensity projection (MIP), reveals an abdominal aortic aneurysm involving the area from the renal arterial orifice to both iliac arteries. The right common iliac artery shows a complete occlusion.

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  Fig. 3 Ultrasonographic images of the abdominal aortic aneurysm. A: transverse B-mode ultrasonography, using a 5-2 MHz transducer, shows a 4.67 cm sized aneurysm. B: in the oblique scan, the presence of a mural thrombus (arrows) is remarkable within the aortic aneurysmal lumen located under the left hepatic lobe.

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  Fig. 4 Transarterial aortography of an abdominal aortic aneurysm. A: through the right common femoral artery, a 5-French catheter was inserted up to the proximal abdominal aorta and iodinated contrast media was injected during the repeated image acquisitions. The abdominal aortic aneurysm and its location could be identified, but the precise morphology and size of the aneurysm could not be depicted due to the obscure margin of contrast-filled lumen. B: through the bilateral common femoral arteries, a bifurcated stent-graft was inserted successfully across the aneurysm. No more abdominal aortic aneurysm was observed, and well-reconstructed aortic lumens could be identified.

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  Fig. 5 Various shapes of an aortic aneurysm. A: a fursiform aneurysm developed in the lower abdominal aorta. The image shows a long proximal leg but no distal leg, between the lower end of the aneurysm as well as aortoiliac bifurcation. In addition, there is angulation of the abdominal aorta. B: a saccular aneurysm is depicted in the distal aortic arch at its left lateral aspect. An mural thrombus located in the anterior aspect and posterior aspect of the aneurysmal neck shows a more acute angle, possibly due to hemodynamic stress. C: coronal multiplanar reformatting reveals a cylindroid aneurysm located at the ascending aorta.

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  Fig. 6 An axial computed tomography (CT) image at the level of the thoracic descending aorta reveals an aortic aneurysm and remarkable calcified atherosclerotic plaque. A mural thrombus is located in the inner side of the calcified plaque. The presence of perianeurysmal soft tissue and fluid density suggests a concealed rupture. Reactive left pleural effusion can also be seen.

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  Fig. 7 An axial computed tomography (CT) image shows a 71 mm sized abdominal aortic aneurysm and a remarkable mural thrombus located in the aneurysmal lumen. Perianeurysmal inflammatory granulation tissue is depicted as a soft tissue mass with adhesion to the adjacent structures (arrows).

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  Fig. 8 Abdominal computed tomography (CT) angiography reveals a ruptured abdominal aortic aneurysm. The maximum diameter of the aneurysm was measured as 90.8 mm. The lumen of the aneurysm is located eccentrically at the right posterolateral aspect and the aneurysmal wall shows marked thinning. A finger-like extravasation of luminal contrast media (arrow) is noted through the mural thrombus and aneurysmal wall suggesting a rupture. Perianeurysmal accumulation of the contrast media also suggests a ruptured aneurysmal wall. A large hematoma can be seen in the retroperitoneal space.

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  Fig. 9 An ascending aortic aneurysm is depicted in a contrast-enhanced computed tomography (CT) image. There is focal outpouching of the aneurysmal lumen, and an aortic bleb in the left lateral side and a small amount of perianeurysmal hemorrhage. These findings can be regarded as impending rupture signs.

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  Fig. 10 A 65-year-old male with a complaint of acute onset radiating back pain was scanned by computed tomography (CT). An abdominal aortic aneurysm is depicted along with a retroperitoneal hemorrhage suggesting a ruptured aneurysm. A mural thrombus is noted at the ventral aspect of the aneurysm and a hyperdense crescent sign due to an acute hemorrhage can be seen within the thrombus (arrow).

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  Fig. 11 A thoracic aortic aneurysm superimposed on chronic Takayasu aortitis. A: a cylindroid aneurysm developed from the ascending aorta to the proximal thoracic descending aorta. Transmural calcification spots located at the aneurysmal wall indicate underlying chronic Takayasu aortitis. B: right posterolateral view of the volume-rendering image reveals multiple patchy calcification along the aortic wall (arrows). The distal thoracic descending aorta shows stenosis as a sign of chronic Takayasu aortitis.

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  Fig. 12 An abdominal computed tomography (CT) image of a 67-year-old male shows an infected aortic aneurysm. A: mild dilatation of the abdominal aorta, periaortic inflammatory granulation tissue, and destructive changes in the adjacent vertebral body indicate an infected abdominal aortic aneurysm. B: air bubbles can be seen at the aneurysmal wall, perianeurysmal granulation tissue area, and destroyed vertebral body suggesting an infection by a gas-forming agent.

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