A NEW SILENT MAGNETIC-RESONANCE-IMAGING USING A ROTATING DC GRADIENT

A new approach to silent MR imaging using a rotating DC gradient has b een explored and experimentally studied. Acoustic or sound noise has b een one of the problems in examining patients, mainly due to the fast gradient pulsings in interaction with the main magnetic field. The sou nd noise has been noted to be proportionately louder as the magnetic f ield strength becomes larger. In this report, we describe a new imagin g technique using a mechanically rotating DC gradient coil. The rotati ng DC gradient coil can effectively replace both phase encoding as wel l as readout gradient pulsings, and data obtained in this manner can p rovide a set of projection data that later can be used for projection reconstruction. With some interpolation techniques one can also perfor m conventional two-dimensional fast Fourier transform image reconstruc tion. The sound noise intensity compared with the conventional imaging technique, such as the spin-echo sequence, has been reduced down to a bout -20.7 dB or 117.5 times with this new technique. The experimental pulse sequence and its principle are described and images obtained by the new silent MR imaging technique are reported.