Optimized gradient pulse for use with EPI employing active acoustic control.
The concept of active acoustic control was recently introduced by Mansfield and Haywood (MAGMA 2000:10:147-151) to ameliorate the problem of acoustic noise from MRI, particularly that from high-speed EPI. A 30 dB reduction in noise was previously achieved with the use of acoustic control operating at spot frequencies within a narrow band. In this work, a new acoustic gradient pulse is introduced that comprises an oscillating gradient of finite duration, incorporating a combination of frequencies within this band designed for use as the switched read gradient in echo-planar imaging (EPI). Employing this pulse with active acoustic control results in a reduction of acoustic noise by 50 dB.
General Magnetic, Strelley Hall, Strelley, Nottingham, UK. general-magnetic@fsmail.net
B L W
BL
Chapman
B
B
Haywood
P
P
Mansfield
D000162:Acoustics; D017352:Echo-Planar Imaging / Q000379:methods*; D004560:Electricity; D006801:Humans