Characterization of Intracardiac Masses by Contrast-Enhanced Magnetic Resonance Imaging
Juerg Schwitter, Veit Herrmann, Markus Glazel
University Hospital Zurich
In a 59-year old man with recurrent fever of unknown origin a cardiac MR study revealed a large cardiac mass located in the left atrium (long axis view, Figure A). Cine MR imaging further demonstrated this mass prolapsing into the left ventricle during diastole causing mild mitral stenosis. On delayed enhancement MR images with the inversion time set to null normal myocardium (black on the MR image) the tumor appears as a bright mass with several irregularly disseminated dark regions (Figure B, same view as in A). In a series of delayed enhanced images with variable inversion times, a 3-parameter fit yielded zero-crossing times which inversely correlate with contrast medium distribution volume (parametric map, Figure C, same view as in A). Thus, white regions (asterisk in the center of the myxoma) represent tissue with high extracellular volume, i.e. low cell content, shades of blue represent compartments with higher distribution volume (e.g. blood) and yellow encodes for tissue with low distribution volume (e.g. myocardium). From the center of the myxoma (asterisk in Figure C), histology confirmed large amount of extracellular matrix and low cellularity (Figure D). Yellow zones within the myxoma (Figure C) represent avascular compartments consisting of cell debris (histology not shown), where contrast medium penetration is limited.
This MR example extends the concept of delayed enhancement MR imaging demonstrating that from a series of delayed enhanced MR images cell content of various tissue components can be estimated which may help in differentiation of cardiac masses. Further refinement of this technique may also detect gradual changes in extracellular space, e.g. in myocarditis or cardiomyopathies.
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