Teaching File

Institute of Radiology "P. Cignolini" - University of Palermo, Italy

Aortic Aneurysm

Gianvincenzo Sparacia, MD
Massimo Midiri, MD
Mario Finazzo, MD
Tommaso Bartolotta, MD

October 1, 1995


MR Findings

Axial and coronal spin echo (SE) T1-weighted MR images

Axial and coronal gradient echo (GE) MR images

  • Fig. 1 - Axial and coronal T1-weighted SE MR images trough aortic root show a large aneurysm (*). A mural thrombosis with a signal intensity from intermediate to high, depending on its age, is present (arrow).

  • Fig. 2 - Axial and coronal GE MR images shows high signal intensity related to blood flow (O). On the other hand intermediate signal intensity characterizes mural thrombosis (*). GE MR imaging is a very useful tool in differentiating slow blood flow from thrombosis.

    DISCUSSION

    Aortic aneurysms are found at approximately 10% of autopsies. They are strongly related to atherosclerosis. Ectasia and aneurysms can coexist.
    The normal aortic diameters are showed below.

    Sinus of Valsalva 3.3 cm
    Mid ascending aorta 3.0 cm
    Aortic arch 2.7 cm
    Descending thoracic aorta 2.4 +/- 0.4 cm

    Aneurysms greater than 6 cm in diameter require surgical treatment, with associated high morbidity and mortality rates. The complete evaluation of aneurysms requires the demonstration of the outer dimension of the aorta, size of the patent lumen, status of the aortic wall, presence of mural thrombus (fig 1), periaortic hematoma, effect of the aneurysm on adjacent structures, and longitudinal extent of the aneurysm and relationship to aortic branches. Identification of different constituents of the aortic aneurysm is possible with MRI. Thrombus or atherosclerotic plaques are demonstrated as eccentric or concentric thickening of the aneurysmal wall. Old thrombus produces medium signal intensity on SE T1-weighted image; conversely, sub-acute thrombus has higher signal intensity. In these cases, distinction between slow flow and fresh thrombus can be equivocal. Gradient echo imaging and phase-mapping techniques are valuable in these situations (fig 2).

    REFERENCES

    1) Higgins CB : The vascular system. In: Magnetic Resonance Imaging of the Body. Higgins CB, Hricak H eds. Raven Press Ltd., New York, 1992 pp 629-678.

    2) Link KM, Lesko NM. The Role of MR Imaging in the evaluation of acquired disease of the thoracic aorta. AJR 1992; 158: 1115-1125.


    Gianvincenzo Sparacia M.D. (radpa@mbox.unipa.it)
    University of Palermo, Institute of Radiology "P. Cignolini"

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