ObjectiveTo evaluate measurement confounders on 2D shear wave elastography (2D-SWE) elastography of muscle.Materials and Methods Ex vivo , porcine muscle was examined with a GE LOGIQ E9 ultrasound machine with a 9 L linear (9 MHz) and C1-6 convex probe (operating at 2.5 or 6 MHz). The influence of different confounders on mean shear wave velocity (SWVmean) was analyzed: probes, pressure applied by probe, muscle orientation, together with the impact of different machine settings such as frequency, placement depth and size of region of interest (ROI). The mean of twelve repeated SWVmean measurements (m/s) and coefficient of variation (CV; standard deviation/mean in %) were assessed for each test configuration. ResultsReproducibility (CV) and maximum possible tissue depth of the linear probe were inferior to the convex probe. With the linear probe, there was a linear decrease of SWVmean with placement depth from 4.56 m/s to 1.81 m/s. A significant increase of SWVmean (p<0.001) was observed for larger ROI widths (range 3.96 m/s to 6.8 m/s). A change in the machine operation mode ('penetration' instead of 'general') led to a significant increase of SWVmean (p=0.04). SWVmean in the longitudinal direction of muscle was significantly higher than in cross section (p<0.001) (e. g. 4.56 m/s versus 3.42 m/s). An increase of linear probe pressure significantly increased muscle SWVmean from 5.29 m/s to 7.21 m/s (p<0.001).Conclusions2D-SWE of muscle is influenced by a wealth of parameters. Therefore, standardization of measurement is advisable before application in clinical research studies and routine patient assessment.

Bilateral fat-signal fractions and volumes based on entire length shoulder muscles in asymptomatic 20-60 year old adults may provide reference for clinicians. Differences shown according to arm dominance should be considered and may rationalize the need for bilateral imaging in determining appropriate management.

Background To assess changes of the craniocervical junction (CCJ), computed tomography (CT) is considered the reference standard. Recent advances in bone depiction on magnetic resonance imaging (MRI) enable high‐quality visualization of osseous structures. Consequently, MRI may serve as an alternative to CT, without the use of ionizing radiation. Purpose To compare two MRI sequences optimized for bone visualization to the CT reference standard in the assessment of the osseous CCJ. Study Type Prospective. Population/Subjects Twenty‐seven decedents and five healthy volunteers. Field Strength/Sequence 3T/ultrashort‐echo time gradient echo (UTE) and optimized 3D‐multiecho in‐phase gradient echo sequences (FRACTURE). Assessment All decedents were scanned with both MRI sequences and CT. Three observers rated degeneration to obtain a score for the upper (atlanto‐dental and left/right atlanto‐occipital joint) and for the lower part of the CCJ (left and right atlanto‐axial joint). Two reader rated the following quantitative parameters: basion‐axial‐interval, atlanto‐dental‐interval, atlanto‐occipital‐interval, Powers‐ratio, and signal/contrast‐to‐noise‐ratio. As a proof of concept, five healthy volunteers were scanned with both MRI sequences. Statistical Tests Degeneration was assessed on a Likert scale by three independent observers. Interrater and intermodality reliability were calculated using an intraclass correlation coefficient. To compare distance measurements between examination methods, a Friedman test, between‐degenerative ratings, and a Kruskal–Wallis test were performed. Results Degenerative ratings of the CCJ between MRI sequences and CT showed a good interrater and intermodality agreement. MRI sequences tended to underestimate the degree of degeneration compared to CT, and this became more marked with increasing degeneration severity. There were no significant relationships between distance measurements and the degree of degeneration (PCT = 0.62, PUTE = 0.64, PFRACTURE = 0.67). The in vivo examination proved the feasibility of both MRI methods in a clinical setting. Data Conclusion Quantitative and qualitative ratings on MR images were comparable to CT images; thus, MRI may be a valid alternative to CT assessing the CCJ. Level of Evidence 1. Technical Efficacy Stage 3.