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Susceptibility Matched Foam


Please see our recent publication on susceptibility matched foam for artifact free MRI. "Pyrolytic graphite foam: A passive magnetic susceptibility matching material," JMRI, 2010.


Purpose:
To evaluate a novel soft, lightweight cushion that can match the magnetic susceptibility of human tissue. The magnetic susceptibility difference between air and tissue produces field inhomogeneities in the B0 field, which leads to susceptibility artifacts in magnetic resonance imaging (MRI) studies.

Materials and Methods:
Pyrolytic graphite (PG) microparticles were uniformly embedded into a foam cushion to reduce or eliminate field inhomogeneities at accessible air and tissue interfaces. 3T MR images and field maps of an air/water/PG foam phantom were acquired. Q measurements on a 4T tuned head coil and pulse sequence heating tests at 3T were also performed.

Results:
The PG foam improved susceptibility matching, reduced the field perturbations in phantoms, does not heat, and is nonconductive.

Conclusion:
The susceptibility matched PG foam is lightweight, safe for patient use, adds no noise or MRI artifacts, is compatible with radiofrequency coil arrays, and improves B0 homogeneity, which enables more robust MR studies. J. Magn. Reson. Imaging 2010;32:684–691. © 2010 Wiley-Liss, Inc.

Figure: Example of water susceptibility matching using PG foam. a: A 3T coronal image of a PG foam, air, and water phantom acquired with a gradient echo sequence, TR/TE = 200/5 msec, slice thickness ¼ 4 mm, FOV = 22.4 x. 22.4 cm, matrix 256 x. 256. Significant distortion is seen near the air cylinder. b: B0 field map of the phantom. The classic 65 ppm dipole effect is seen outside of the air cylinder but is significantly reduced outside the PG foam, indicating improved susceptibility matching.
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