Abstract
The incidence of metallic dental restorations and implants is increasing, and head and neck MR imaging is becoming challenging regarding artifacts. Our aim was to evaluate whether multiple-slab acquisition with view angle tilting gradient based on a sampling perfection with application-optimized contrasts by using different flip angle evolution (MSVAT-SPACE)-STIR and slice-encoding for metal artifact correction (SEMAC)-STIR are beneficial regarding artifact suppression compared with the SPACE-STIR and TSE-STIR in vitro and in vivo. At 3T, 3D artifacts of 2 dental implants, supporting different single crowns, were evaluated. Image quality was evaluated quantitatively (normalized signal-to-noise ratio) and qualitatively (2 reads by 2 blinded radiologists). Feasibility was tested in vivo in 5 volunteers and 5 patients, respectively. Maximum achievable resolution and the normalized signal-to-noise ratio of MSVAT-SPACE-STIR were higher compared with SEMAC-STIR. Performance in terms of artifact correction was dependent on the material composition. For highly paramagnetic materials, SEMAC-STIR was superior to MSVAT-SPACE-STIR (27.8% smaller artifact volume) and TSE-STIR (93.2% less slice distortion). However, MSVAT-SPACE-STIR reduced the artifact size compared with SPACE-STIR by 71.5%. For low-paramagnetic materials, MSVAT-SPACE-STIR performed as well as SEMAC-STIR. Furthermore, MSVAT-SPACE-STIR decreased artifact volume by 69.5% compared with SPACE-STIR. The image quality of all sequences did not differ systematically. In vivo results were comparable with in vitro results. Regarding susceptibility artifacts and acquisition time, MSVAT-SPACE-STIR might be advantageous over SPACE-STIR for high-resolution and isotropic head and neck imaging. Only for materials with high-susceptibility differences to soft tissue, the use of SEMAC-STIR might be beneficial. Within limited acquisition times, SEMAC-STIR cannot exploit its full advantage over TSE-STIR regarding artifact suppression.
Highlights
BACKGROUND AND PURPOSEThe incidence of metallic dental restorations and implants is increasing, and head and neck MR imaging is becoming challenging regarding artifacts
ABBREVIATIONS: CCT-T ϭ porcelain-fused-to-metal nonprecious alloy crown with titanium implant; MAVRIC ϭ multiacquisition with variable resonance image combination; MSVAT-SPACE ϭ multiple-slab acquisition with view angle tilting gradient based on SPACE; nSNR ϭ normalized SNR; mean (SNR); SEMAC ϭ slice-encoding for metal artifact correction; SPACE ϭ sampling perfection with application-optimized contrasts by using different flip angle evolutions; Z-T ϭ monolithic zirconia crown with titanium implant
Impact of Sequence Type on Artifact Volume Comparing all STIR sequences with each other, we found a significant decrease of 71.5% Ϯ 0.1% in artifact volume in MSVATSPACE-STIR compared with SPACE-STIR for the CCT-T sample (P Ͻ .001) and 69.7% Ϯ 5.4% for the Z-T sample (P Ͻ .001, Figs 1 and 2)
Summary
BACKGROUND AND PURPOSEThe incidence of metallic dental restorations and implants is increasing, and head and neck MR imaging is becoming challenging regarding artifacts. Our aim was to evaluate whether multiple-slab acquisition with view angle tilting gradient based on a sampling perfection with application-optimized contrasts by using different flip angle evolution (MSVAT-SPACE)-STIR and slice-encoding for metal artifact correction (SEMAC)-STIR are beneficial regarding artifact suppression compared with the SPACE-STIR and TSE-STIR in vitro and in vivo
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