Gerrit
Hendrik van de Maat1, Hendrik de Leeuw1, Peter R.
Seevinck1, Chris J.G Bakker2
1Image Sciences Institute, Utrecht,
Netherlands; 2Department of Radiology, University Medical Center,
Utrecht, Netherlands
It
is feasible to excite protons that reside in the vicinity of Holmium loaded
microspheres inside a voxel by shifting the center frequency f0 of
the rf-excitation pulse. Due to this frequency shift, on-resonance protons are
not excited and signal is only generated by protons strongly influenced by
the dipole fields invoked by the microspheres. The total signal intensity of
a voxel is related to the concentration HoMS in that voxel. The resulting
positive contrast can be manipulated by the user since it will depend on the
excitation bandwidth and profile and on the f0 frequency shift.