Metal artifact reduction in XXXX with dental implants using multispectral three-dimensional data acquisition for hybrid PET/MRI.

@entity1 @entity5
BACKGROUND: Hybrid positron emission tomography/magnetic resonance imaging (PET/MRI) shows high potential for @entity1 with @entity5 . Dental implants can cause substantial artifacts in the oral cavity impairing diagnostic accuracy. Therefore, we evaluated new MRI sequences with multi-acquisition variable-resonance image combination (MAVRIC SL) in comparison to conventional high-bandwidth techniques and in a second step showed the effect of artifact size on MRI-based attenuation correction (AC) with a simulation study. METHODS: Twenty-five @entity1 with dental implants prospectively underwent a trimodality PET/CT/MRI examination after informed consent was obtained under the approval of the local ethics committee. A conventional 3D gradient-echo sequence (LAVA-Flex) commonly used for MRI-based AC of PET (acquisition time of 14  s), a T1w fast spin-echo sequence with high bandwidth (acquisition time of 3.2  min), as well as MAVRIC SL sequence without and with increased phase acceleration (MAVRIC, acquisition time of 6  min; MAVRIC-fast, acquisition time of 3.5  min) were applied. The absolute and relative reduction of the signal void artifact was calculated for each implant and tested for statistical significance using the Wilcoxon signed-rank test. The effect of artifact size on PET AC was simulated in one case with a large @entity5 in the oral cavity. The relative difference of the maximum standardized uptake value (SUVmax) in the @entity5 was calculated for increasing artifact sizes centered over the second molar. RESULTS: The absolute reduction of signal void from LAVA-Flex sequences to the T1-weighted fast spin-echo (FSE) sequences was 416  mm(2) (range 4 to 2,010  mm(2)) to MAVRIC 481  mm(2) (range 12 to 2,288  mm(2)) and to MAVRIC-fast 486  mm(2) (range 39 to 2,209  mm(2)). The relative reduction in signal void was significantly improved for both MAVRIC and MAVRIC-fast compared to T1 FSE (-75%/-78% vs. -62%, p   <   0.001 for both). The relative error for SUVmax was negligible for artifacts of 0.5-cm diameter (-0.1%), but substantial for artifacts of 5.2-cm diameter (-33%). CONCLUSIONS: MAVRIC-fast could become useful for artifact reduction in PET/MR for @entity1 with dental implants. This might improve diagnostic accuracy especially for @entity1 with @entity5 in the oropharynx and substantially improve accuracy of PET quantification.
