Accelerated slice encoding for metal artifact correction.
OBJECTIVE
To demonstrate accelerated imaging with both artifact reduction and different contrast mechanisms near metallic implants.


METHODS
Slice-encoding for metal artifact correction (SEMAC) is a modified spin echo sequence that uses view-angle tilting and slice-direction phase encoding to correct both in-plane and through-plane artifacts. Standard spin echo trains and short-TI inversion recovery (STIR) allow efficient PD-weighted imaging with optional fat suppression. A completely linear reconstruction allows incorporation of parallel imaging and partial Fourier imaging. The signal-to-noise ratio (SNR) effects of all reconstructions were quantified in one subject. Ten subjects with different metallic implants were scanned using SEMAC protocols, all with scan times below 11 minutes, as well as with standard spin echo methods.


RESULTS
The SNR using standard acceleration techniques is unaffected by the linear SEMAC reconstruction. In all cases with implants, accelerated SEMAC significantly reduced artifacts compared with standard imaging techniques, with no additional artifacts from acceleration techniques. The use of different contrast mechanisms allowed differentiation of fluid from other structures in several subjects.


CONCLUSIONS
SEMAC imaging can be combined with standard echo-train imaging, parallel imaging, partial-Fourier imaging, and inversion recovery techniques to offer flexible image contrast with a dramatic reduction of metal-induced artifacts in scan times under 11 minutes.
Hargreaves
Brian A
BA
Department of Radiology, Stanford University, Stanford, California 94305-5488, USA. bah@stanford.edu
Chen
Weitian
W
Lu
Wenmiao
W
Alley
Marcus T
MT
Gold
Garry E
GE
Brau
Anja C S
AC
Pauly
John M
JM
Pauly
Kim Butts
KB
D000465:Algorithms; D016477:Artifacts; D003287:Contrast Media / Q000494:pharmacology*; D005583:Fourier Analysis; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008670:Metals / Q000737:chemistry*; D019047:Phantoms, Imaging; D019736:Prostheses and Implants; D013997:Time Factors
D003287:Contrast Media; D008670:Metals