Work

Timing Is Everything: How Subtle Timing Changes in MRI Echo Planar Imaging Can Significantly Alter Mechanical Vibrations and Sound Level

Year: 2026

Type: article

Abstract: PURPOSE: Echo-Planar Imaging (EPI) is central to fMRI, diffusion MRI, and many dynamic clinical applications, yet rapid gradient switching induces strong mechanical vibrations, generates acoustic noise, and contributes to ghosting artifacts-effects that intensify at ultra-high fields. This study aims to predict how subtle timing changes in multi-train EPI can modulate acoustic energy and reduce ghosting without altering reconstruction or acquisition design. METHODS: We derived an analytic model describing the interference between short gradient trains and combined it with the system's acoustic transfer function to predict the acoustic energy of a scan. The model predicts cyclic variations in acoustic power resulting from small timing adjustments of slices and echoes. Validation was performed on a clinical 7 T and an investigational 10.5 T MRI systems by measuring acoustic output and ghosting-artifact levels while systematically sweeping timing conditions in single and multi-echo EPI protocols. RESULTS: Sub-millisecond timing modifications produced large, predictable changes in the acoustic power; changes ranging from 2-fold to 47-fold. Intriguingly, under certain conditions, doubling the acquisitions per unit-time reduced the minimal acoustic energy two-fold. In addition, navigator time shifting reduced the ghosting-artifact intensity, up to 5-fold, exhibiting cyclic dependence corresponding to the dominant acoustic resonance frequency. These trends were consistent across both the 7 T and the 10.5 T systems. CONCLUSION: Minimal timing adjustments provide an effective, reconstruction-agnostic strategy to reduce acoustic noise, to mitigate ghosting artifacts, and to expand feasible EPI parameters space. The proposed model paves the way towards quieter, higher-quality EPI scans, particularly valuable for ultra-high-field and high-speed imaging.

Source: Magnetic Resonance in Medicine

DOI: 10.1002/mrm.70271