Pericarditis MRI
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American Roentgen Ray Society Images of Pericarditis MRI |
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Cardiac MRI [1]
CMR provides good resolution for identifying many types of pericardial pathology. On T1-weighted spin echo imaging, the pericardium appears as a thin, low-signal band bordered by bright, high-signal bands corresponding to epicardial and pericardial fat. The pericardium on CMR appears black because of its low water content. With gadolinium, however, it may enhance in acute inflammation. Normal thickness of the pericardium on CMR is 2-4mm, although the thickness has been shown to be slightly greater than expected from pathological studies due to chemical shift caused by the fat overlying the pericardium.
Cardiac MRI in Constrictive pericarditis
Because pericardial thickness is easily measured on CMR, it is considered the definitive approach for diagnosis of constrictive pericarditis; coronal and axial spin-echo CMR have been reported to have a sensitivity of 88%, specificity of 100%, and diagnostic accuracy of 93% in making this diagnosis. In addition, depending on the severity of the constrictive pericarditis, dilatation of the IVC, hepatic veins, and right atrium as well as a normal or compressed/elongated right ventricle can be seen. Differentiating between causes of pericardial thickening can be difficult, however; inflammatory etiologies usually lead to greater thickening than [[Category:]]fibrotic ones. Also, in chronic constriction the thickened pericardium displays a lower intensity than in acute pericarditis.
Cardiac MRI in pericardial effusions
It is important to distinguish the thickness of the pericardium from any pericardial effusion, which commonly appears black on spin echo images but bright on gradient echo cines. Moderate-sized effusions are often associated with a pericardial space anterior to the right ventricle of size greater than 5mm. Cine images can detect cardiac tamponade by revealing diastolic collapse of right sided and sometimes left-sided cardiac chambers. Regarding the composition of pericardial effusions, transudates have low signal on T1-weighted images but high signal on T2-weighted and gradient echo images. Exudates display an intermediate signal on both types of sequences. Hemorrhagic effusions may show a wide range of signal intensity on spin-echo sequences that depends on the age of the effusion.
Cardiac MRI in other pericardial pathologies
Other types of pericardial pathology detectable by CMR include pericardial cysts; metastasis and primary tumors of the pericardium; and intracardiac tumors such as myxomas, lipomas, and teratomas. The signal intensity of fluid within pericardial cysts increases progressively with echo time, leading to accurate detection. Pericardial calcification, on the other hand, is not well-detected by CMR. Calcium appears black on CMR and therefore may resemble a localized area of pericardial thickening; cardiac CT is preferred for visualizing pericardial calcification.
References
- ↑ Higgins CB, De Roos A (2003) Cardiovascular MRI and MRA. Lippincott Williams & Wilkins, Philadelphia