PURPOSE To assess lesion detection and artifact size reduction of a MAVRIC-SEMAC hybrid sequence (MAVRIC-SL) compared to standard sequences at 1.5T and 3T in porcine knee specimens with metal hardware. METHODS Artificial cartilage and bone lesions of defined size were created in the proximity of titanium and steel screws with 2.5 mm diameter in 12 porcine knee specimens and were imaged at 1.5T and 3T MRI with MAVRIC-SL PD and STIR, standard FSE T2 PD and STIR and fat-saturated T2 FSE sequences. Three radiologists blinded to the lesion locations assessed lesion detection rates on randomized images for each sequence using ROC. Artifact length and width were measured. RESULTS Metal artifact sizes were largest in the presence of steel screws at 3T (FSE T2 FS: 28.7cm2) and 1.5T (16.03cm2). MAVRIC-SL PD and STIR reduced artifact sizes at both 3T (1.43cm2; 2.46cm2) and 1.5T (1.16cm2; 1.59cm2) compared to FS T2 FSE sequences (27.57cm2; 13.20cm2). At 3T, ROC derived AUC values using MAVRIC-SL sequences were significantly higher compared to standard sequences (MAVRIC-PD: 0.87, versus FSE-T2-FS: 0.73 (p=0.025); MAVRIC- STIR: 0.9 versus T2-STIR: 0.78 (p=0.001) and versus FSE-T2-FS: 0.73 (p=0.026)). Similar values were observed at 1.5T. Comparison of 3T and 1.5T showed no significant differences (MAVRIC-SL PD: p=0.382; MAVRIC-SL STIR: p=0.071. CONCLUSION MAVRIC-SL sequences provided superior lesion detection and reduced metal artifact size at both 1.5T and 3T compared to conventionally used FSE sequences. No significant disadvantage was found comparing MAVRIC-SL at 3T and 1.5T, though metal artifacts at 3T were larger.

Background: Reproducible image quality is of high relevance for large cohort studies and can be challenging for magnetic resonance imaging (MRI). Automated image quality assessment may contribute to conducting radiologic studies effectively. Purpose: The aims of this study were to assess protocol repetition frequency in population-based whole-body MRI along with its effect on examination time and to examine the applicability of automated image quality assessment for predicting decision-making regarding repeated acquisitions. Materials and Methods: All participants enrolled in the prospective, multicenter German National Cohort (NAKO) study who underwent whole-body MRI at 1 of 5 sites from 2014 to 2016 were included in this analysis (n = 11,347). A standardized examination program of 12 protocols was used. Acquisitions were carried out by certified radiologic technologists, who were authorized to repeat protocols based on their visual perception of image quality. Eleven image quality parameters were derived fully automatically from the acquired images, and their discrimination ability regarding baseline acquisitions and repetitions was tested.Results: At least 1 protocol was repeated in 12% (n = 1359) of participants, and more than 1 protocol in 1.6% (n = 181). The repetition frequency differed across protocols ( P < 0.001), imaging sites ( P < 0.001), and over the study period ( P < 0.001). The mean total scan time was 62.6 minutes in participants without and 67.4 minutes in participants with protocol repetitions (mean difference, 4.8 minutes; 95% confidence interval, 4.5-5.2 minutes). Ten of the automatically derived image quality parameters were individually retrospectively predictive for the repetition of particular protocols; for instance, "signal-to-noise ratio" alone provided an area under the curve of 0.65 ( P < 0.001) for repetition of the Cardio Cine SSFP SAX protocol. Combinations generally improved prediction ability, as exemplified by "image sharpness" plus "foreground ratio" yielding an area under the curve of 0.89 ( P < 0.001) for repetition of the Neuro T1w 3D MPRAGE protocol, versus 0.85 ( P < 0.001) and 0.68 ( P < 0.001) as individual parameters. Conclusions: Magnetic resonance imaging protocol repetitions were necessary in approximately 12% of scans even in the highly standardized setting of a large cohort study. Automated image quality assessment shows predictive value for the technologists' decision to perform protocol repetitions and has the potential to improve imaging efficiency.