Feasibility of fat-saturated T2-weighted magnetic resonance imaging with slice encoding for metal artifact correction (SEMAC) at 3T.
BACKGROUND AND PURPOSE
Fluid-sensitive MR imaging in postoperative evaluation is important, however, metallic artifacts is inevitable. The purpose is to investigate the feasibility of fat-saturated slice encoding for metal artifact correction (SEMAC)-corrected T2-weighted magnetic resonance (MR) at 3T in patients with spinal prostheses.


METHODS
Following institutional review board approval, 27 SEMAC-encoded spinal MRs between September 2012 and October 2013 in patients with spinal metallic prostheses were analyzed. The MR images were scanned on a 3T MR system including SEMAC-corrected and uncorrected fast spin echo (FSE) T2-weighted MR images with fat-saturation. Two musculoskeletal radiologists compared the image sets and qualitatively analyzed the images using a five-point scale in terms of artifact reduction around the prosthesis, visualization of the prosthesis and pedicle, and intervertebral neural foramina. Quantitative assessments were performed by calculating the ratio of signal intensity from the fixated vertebra and that from upper level vertebra. For statistical analyses, paired t-test was used.


RESULTS
Fat-saturated SEMAC-corrected T2-weighted MR images enabled significantly improved metallic artifact reduction (P<0.05). Quantitative evaluation of the signal intensity ratio of screw-fixated vertebra and upper level vertebra showed a significantly lower ratio on fat-saturated SEMAC images (P<0.05), however, the high signal intensity of signal pile-up could be not completely corrected.


CONCLUSION
SEMAC correction in fat-suppressed T2-weighted MR images can overcome the signal loss of metallic artifacts and provide improved delineation of the pedicle screw and peri-prosthetic region. Signal pile-up, however, could not be corrected completely, therefore readers should be cautious in the evaluation of marrow around the prosthesis.
['Lee|Young Han|YH|', 'Lim|Daekeon|D|', 'Kim|Eunju|E|', 'Kim|Sungjun|S|', 'Song|Ho-Taek|HT|', 'Suh|Jin-Suck|JS|']
D000273:Adipose Tissue D000328:Adult D000368:Aged D016477:Artifacts D001416:Back Pain D001853:Bone Marrow D001863:Bone Screws D005260:Female D006801:Humans D007091:Image Processing, Computer-Assisted D008279:Magnetic Resonance Imaging D008297:Male D008670:Metals D008875:Middle Aged D019736:Prostheses and Implants D012815:Signal Processing, Computer-Assisted D013123:Spinal Fusion D013131:Spine
Magnetic resonance Slice encoding for metal artifact correction Metallic artifacts Metallic artifact reduction Fat suppression