General Electric Company

Sheila Srinivasan Washburn

Richard Scott Hinks

Harvey E Cline

Christopher Judson Hardy

Ronald Dean Watkins

Erika Schneider

Correcting gradients for a phase encoding axis in an MRI imaging system are provided in an FSE pulse sequence to correct phase errors in echo signals, such as due to effects of cross term eddy currents induced by slice select gradients. Correcting gradients to be applied to the logical phase encoding axis are identified in a prescan sequence. An initial correcting gradient is identified for correcting phase errors resulting from an initial slice select gradient pulse. Subsequent, bipolar gradient pulses for the phase encoding axis are then derived from the initial correcting gradient. The prescan technique may be used in conjunction with other prescanning sequences used to determine additional corrections for the FSE sequence. The correcting gradients reduce or eliminate image artifacts resulting from such factors as cross term eddy currents in oblique scans. An averaging sequence may be implemented to reduce the likelihood for influencing the compensation pulse calculation errors. When implemented, the logical axes may be rotated to provide any desired oblique orientation.

Fast spin echo prescan for magnetic resonance imaging systems

NMR images indicative of thermal changes in tissues undergoing therapy are produced using a gradient-recalled double-echo pulse sequence. A reference phase image is produced using a short echo time (TE.sub.1) and a measurement phase image is produced with a longer echo time (TE.sub.2). Temperature maps are produced during therapy using the phase difference information at corresponding pixels of the two phase images.

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New Berlin, WI, United States of America

Sheila Srinivasan Washburn