Compensation for the MR geometric image distortion caused by the implantable drug infusion pump

Implantable devices often cause serious MR image artifacts in the vicinity of their implanted locations as the result of susceptibility-induced image distortion, and the resulting artifacts may render the MR images useless for diagnosis. To reduce the MR artifacts in the stage of image acquisition, we have implemented a scheme by which the field inhomogeneity is compensated in a spin echo imaging sequence by introducing a readout-like gradient pulse along the slice-select gradient direction temporally concurrent with the read-out gradient (TE=20msec). It can be shown that this slice direction compensation gradient pulse during the read-out period compensates the field inhomogeneity during the image data collection period. Though there was a shift in the direction of the read-out direction as a result of the compensation gradient for non-central slices, this shift can be predicted and it can be corrected either at the image acquisition stage by offsetting the frequency or as a post image processing. Our experimental studies showed that images obtained with a common implantable infusion pump exhibited a substantial reduction in terms of the image distortion compared with that of the standard imaging technique. In conclusion, the susceptibility-induced image artifacts can be significantly reduced using the compensation scheme.