Partial RF echo planar imaging with the FAISE method. I. Experimental and theoretical assessment of artifact.
The fast acquisition interleaved spin-echo (FAISE) method is a partial RF echo-planar technique which utilizes a specific phase-encode reordering algorithm to manipulate image contrast (Melki et al., J. Magn. Reson. Imaging 1:319, 1991). The technique can generate "spin-echo" like images up to 16 times faster than conventional spin-echo methods. However, the presence of T2 decay throughout the variable k-space trajectories used to manipulate T2 contrast ensures the presence of image artifacts, especially along the phase-encode direction. In this work, we experimentally and theoretically examine the type and extent of artifacts associated with the FAISE technique. We demonstrate the existence of well-defined minima of phase-encode ghost noise for selected k-space trajectories, examine the extent of blurring and edge enhancement artifacts, demonstrate the influence of matrix size and number of echoes per train on phase-encode artifact, and show how proper choice of FAISE sequence parameters can lead to proton density brain images which are practically indistinguishable from conventional spin-echo proton density images. A comparison of contrast between FAISE and standard spin-echo methods is presented in a companion article referred to as II.
Melki
P S
PS
Department of Radiology, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts 02115.
Jolesz
F A
FA
Mulkern
R V
RV
D000465:Algorithms; D016477:Artifacts; D001921:Brain / Q000033:anatomy & histology; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000295:instrumentation / Q000379:methods*; D008961:Models, Structural; D008962:Models, Theoretical; D009532:Nickel; D013997:Time Factors
C022838:nickel chloride; D009532:Nickel