Investigation of vibration‐induced artifact in clinical diffusion‐weighted imaging of pediatric subjects

Abstract

It has been reported that mechanical vibrations of the MRI scanner could produce spurious signal dropouts in diffusion-weighted images resulting in artifactual anisotropy in certain regions of the brain with red appearance in the Directionally Encoded Color maps. We performed a review of the frequency of this artifact across pediatric studies, noting differences by scanner manufacturer, acquisition protocol, as well as weight and position of the subject. We also evaluated the ability of automated and quantitative methods to detect this artifact. We found that the artifact may be present in over 50% of data in certain protocols and is not limited to one scanner manufacturer. While a specific scanner had the highest incidence, low body weight and positioning were also associated with appearance of the artifact for both scanner types evaluated, making children potentially more susceptible than adults. Visual inspection remains the best method for artifact identification. Software for automated detection showed very low sensitivity (10%). The artifact may present inconsistently in longitudinal studies. We discuss a published case report that has been widely cited and used as evidence to set policy about diagnostic criteria for determining vegetative state. That report attributed longitudinal changes in anisotropy to white matter plasticity without considering the possibility that the changes were caused by this artifact. Our study underscores the need to check for the presence of this artifact in clinical studies, analyzes circumstances for when it may be more likely to occur, and suggests simple strategies to identify and potentially avoid its effects.

White matter compromise in autism? Differentiating motion confounds from true differences in diffusion tensor imaging

“…The rapid gradient switching of diffusion sequences is notorious for inducing scanner vibration. When the gradient is applied maximally to a single gradient coil, or high b ‐values are used, localized areas of signal dropout can occur from vibrationally‐induced shear‐waves in brain tissue [Gallichan et al, ; Berl et al, ]. This is not problematic under normal circumstances and typical b ‐values, but may be an issue with mechanical deficiencies [e.g.…”

Reduction of vibration‐induced signal loss by matching mechanical vibrational states: Application in high b‐value diffusion‐weighted MRS

“…The proposed approach could be also of interest in DW imaging of the brain, where vibration induced artifacts were reported previously . Especially in pediatric cases, vibration effects could be even more severe due to the light weight of the patients and the typical optimization of the scanner hardware toward adult weights and dimensions . The general trend toward high b ‐value brain diffusion that allows high‐resolution diffusion tensor imaging with fiber tracking comes with the cost of stronger and longer diffusion gradients .…”

“…7 Especially in pediatric cases, vibration effects could be even more severe due to the light weight of the patients and the typical optimization of the scanner hardware toward adult weights and dimensions. 8 The general trend toward high b-value brain diffusion that allows high-resolution diffusion tensor imaging with fiber tracking comes with the cost of stronger and longer diffusion gradients. 9 Such more demanding requirements on the gradient scanner hardware are expected to increase the occurrence and strength of vibration artifacts.…”

“…The observed vibrations were so strong that even elastography experiments utilizing the table vibrations as the main source of mechanical actuation have been proposed . The observed influences of additional vibration‐induced motion include reports of signal loss in brain DW images and reports of increased lipid ADC measures in subcutaneous fat in regions close to the scanner table …”

“…5 The observed vibrations were so strong that even elastography experiments utilizing the table vibrations as the main source of mechanical actuation have been proposed. 6 The observed influences of additional vibration-induced motion include reports of signal loss in brain DW images 7,8 and reports of increased lipid ADC measures in subcutaneous fat in regions close to the scanner table. 4 Multiple research applications require particularly high b-values diffusion measurements, including high-resolution diffusion tensor imaging of the brain 9 or the assessment of fat microstructure with diffusion MRI.…”