?Silent? MRI with soft gradient pulses

TLDR

Acoustic noise from gradient coils is low below 200 Hz, so limiting pulse spectra to this range can markedly reduce noise. The authors propose a noise‑reduction method for MRI gradient systems based on linear response theory. Soft, band‑limited pulse shapes are designed with sinusoidal ramps tuned to available delays, and silent versions of gradient‑echo, spin‑echo, and RARE sequences were implemented on 2‑ and 3‑T scanners. High‑quality images were obtained with noise levels as low as 40 dBA for GE and SE and 60 dBA for RARE. Magn Reson Med 42:6–10, 1999; © 1999 Wiley‑Liss, Inc.

Abstract

A method to reduce the acoustic noise generated by gradient systems in magnetic resonance imaging (MRI) is proposed based on the linear response theory. Since the acoustic frequency response function of typical gradient coils is low in the range below 200 Hz, the noise level can be significantly reduced by using gradient pulse sequences whose spectra are limited to this frequency range. Such “soft,” i.e., band-limited, pulse shapes can be designed using sinusoidal ramps individually adjusted to available delays. “Silent” versions of three basic MRI sequences [gradient-echo (GE), spin-echo (SE), and rapid acquisition with relaxation enhancement (RARE)] were programmed on 2 and 3 T whole-body scanners. High-quality images could be acquired at noise levels as low as 40 dBA (GE and SE) and 60 dBA (RARE). Magn Reson Med 42:6–10, 1999. © 1999 Wiley-Liss, Inc.