AJR 2002; 179:475-476
© American Roentgen Ray Society
Characterizing Chronic Pericarditis Using Steady-State Free-Precession Cine MR Imaging
Arzu Kovanlikaya1,
Lennis P. Burke1,2,
Marvin D. Nelson1 and
John Wood3
1 Department of Radiology, Children's Hospital Los Angeles, 4650 Sunset Blvd.,
Los Angeles, CA 90027.
2 Pacific Pediatric Cardiology, 50 W. Bellefontaine St., Ste. 405, Pasadena, CA
91105.
3 Department of Cardiology, Children's Hospital Los Angeles, Los Angeles, CA
90027.
Received November 5, 2001;
accepted after revision December 21, 2001.
Address correspondence to A. Kovanlikaya.
Introduction
The pericardium is well revealed on MR imaging because of the superb
contrast resolution and multiplanar capability of the technique
[1]. Typically, T1-and
T2-weighted spin-echo or fast spin-echo MR sequences are collected as well as
gradient-echo cine images with or without IV contrast material
[1,2,3,4].
This case report illustrates the value of a steady-state free-precession
imaging technique known as FIESTA (Fast Imaging Employing Steady-State
Acquisition) on a 1.5-T scanner (Signa; General Electric Medical Systems,
Milwaukee, WI) in the assessment of pericarditis. With this sequence, we are
able to clearly distinguish pericardial thickening from pericardial effusion
through a single sequence while simultaneously obtaining information on
myocardial function and possible pericardial tethering.
Case Report
A 14-year-old boy was admitted to our hospital with chest pain and
shortness of breath. He had been healthy until 6 months before admission when
he developed a nonspecific viral illness. He rapidly recovered from the acute
symptoms but remained fatigued and began to experience slowly progressive
substernal chest pain and a decreased appetite. At admission, his vital signs
were stable; no pulsus paradoxicus was evident. Chest radiography showed
marked cardiomegaly. His erythrocyte sedimentation rate and C-reactive protein
level were elevated, but results of tests for rheumatoid factor and
antinuclear antibody were negative. Echocardiography revealed a large
circumferential pericardial effusion with marked thickening of the visceral
and parietal pericardial layers. Multiple strands were noted traversing the
pericardial space between the pericardial layers.
Steady-state free-precession MR imaging (TR/TE, 3.6/1.5; flip angle,
45°; field of view, 36 cm; phase field of view, 0.75 cm; matrix, 128
x 256; slice thickness, 8 mm; views per segment, 12; cardiac phases to
reconstruct, 20; breath-hold length per slice, 8 sec; total scanning time, 4
min; and slices obtained in the short-axis plane) showed a small
circumferential pericardial effusion and focal thickening of the pericardium
along the posterolateral wall (Fig.
1A). In that region, the pericardium measured between 4- and 7-mm
thick. Although the thickened pericardium contacted the ventricle during
diastole, the pericardial fluid interposed during systole
(Fig. 1B), indicating no
adhesion. The pericardium overlying the right atrium and right ventricle was
more prominent than normal but still measured less than 4 mm. More pericardial
fluid was observed along the right heart border, with some
"sloshing" from the base to the apex. Neither the right atrium nor
great veins were dilated. The biventricular dimensions and function were
within normal limits. The left ventricular end diastolic volume was 108 mL,
and left ventricular ejection fraction was 72%. The right ventricular end
diastolic volume was 103 mL, and right ventricular ejection fraction was 76%.
The surface area of the patient's body was 1.8 m2.
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Fig. 1B. —14-year-old boy with chronic pericarditis. T2-weighted
steady-state free-precession image obtained at the same level as A
during end systole reveals pericardial fluid (arrow) interposed
between thickened pericardium and ventricle, indicating no adhesion.
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Attempts at needle pericardiocentesis were unsuccessful, and the patient
subsequently underwent a surgical pericardiotomy and limited pericardiectomy.
More than 600 mL of serous pericardial fluid was removed. The pericardial
layers were described as thick, and the pericardial space was filled with a
considerable amount of a fibrinous coagulum. The surgical procedure resulted
in marked clinical improvement, and the patient was discharged from the
hospital. A biopsy of the pericardium confirmed chronic non-specific fibrinous
pericarditis with no evidence of microorganisms. Examination of the
pericardial fluid showed inflammatory cells but otherwise the results of the
cytology were normal and the results of the cultures were negative.
Discussion
In MR imaging of chronic pericarditis, T1-and T2-weighted spin-echo imaging
techniques are typically used to characterize pericardial thickening and
effusion; gradient-echo cine imaging is performed to assess myocardial
function. On T1-weighted spin-echo MR imaging, the normal pericardium is
identified as a thin band of low signal intensity between the high signal
intensities of the external pericardial fat and the internal epicardial fat
[1,2,3,4].
The normal pericardial thickness is approximately 2 mm, although a thickness
of up to 4 mm is not necessarily abnormal. The low signal intensity of the
pericardium is attributable to the fibrous component of the pericardium in
combination with a small quantity of adherent pericardial fluid
[1]. The appearance of
pericardial effusions may vary on T1-weighted MR images, depending on the
protein and cellular content of the effusion; hence, both T2-weighted imaging
and contrast-enhanced T1-weighted imaging have been used to characterize
pericardial effusions and to distinguish effusion from pericardium
[5].
In the presence of a thickened pericardium, gradient-echo imaging is also
vital because it provides quantitative and qualitative information on the
myocardial systolic and diastolic functioning. Myocarditis may accompany
pericarditis, and quantitative evaluation of the patient's biventricular
function should be performed. Constrictive pericarditis occurs when diastolic
filling of the heart is limited by decreased pericardial compliance and
adhesions. Evidence of restricted filling has been observed using
phase-contrast velocimetry in the superior vena cava
[6] and using myocardial
tagging to detect myocardial—pericardial adhesions
[7]. However, qualitative
inspections of right atrial and right ventricular dynamics as well as great
vein distention provide important subjective clues
[2].
In our patient, steady-state free-precession MR imaging provided all of the
information required to make the diagnosis of chronic pericarditis without
constriction. This sequence is a fully balanced steady-state coherent imaging
pulse sequence that produces high signal-to-noise ratio images at extremely
short sequence times. The TR and TE are kept as short as possible (e.g., 3 and
1 msec, respectively) to minimize motion and susceptibility artifacts. The
image contrast is related to the T2-T1 ratio. Tissues with a high ratio, such
as blood and fat, appear bright, whereas tissues with low T2-T1 ratios, such
as muscle and myocardium, appear dark
[8]. The differentiation of
contrast between the tissues with low T2-T1 ratios (low signal intensity) and
those with high T2-T1 ratios (high signal intensity) enables better
delineation of the pericardium, pericardial and epicardial fat, and
pericardial fluid on a single sequence. Furthermore, end systolic and end
diastolic ventricular volumes can also be calculated from the same multiphasic
images.
In conclusion, steady-state free-precession imaging provides rapid
characterization of pericardial thickening, pericardial effusion, quantitative
myocardial systolic function, and qualitative diastolic function. In our
patient, this technique was sufficient to diagnose chronic pericarditis
without constriction. Because this sequence can be performed rapidly,
additional imaging, such as phase-velocity imaging or myocardial tagging, may
easily be performed if necessary to clarify findings in more difficult
cases.
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