DIFFUSION-WEIGHTED MULTIPLE SHOT ECHO-PLANAR IMAGING OF HUMANS WITHOUT NAVIGATION

A new method is proposed for reducing the artifacts produced in diffus ion-weighted imaging, When data are acquired using multiple shot echo planar acquisitions, conventional reconstruction methods produce artif actual images as a consequence of diffusion weighting and small amount s of bulk motion of the subject, If the amount of motion can be determ ined, it is possible to correct the data before reconstruction, which removes the artifact. A method for estimating the motion from the acqu ired data has been developed and evaluated, This method assumes that g host image effects will be minimized when motion has been correctly co mpensated, By considering the amount of signal in the background of th e image, appropriate corrections to the data can be made, and the accu racy of the motion compensation may be estimated, This technique has b een evaluated by computer simulation, and its performance has been dem onstrated in a phantom and humans with both two- and four-shot echo pl anar acquisitions and using both ''mosaic'' and ''interleaved'' sampli ng schemes.