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Abstract #0550

Linear Phase Shift Correction for Field Map Estimation with Bipolar Gradient Dual-Echo Sequence Using the Noise PDF

Hiroyuki Takeda1, Boklye Kim2

1Radiology, University of Michigan, Ann Arbor, MI, United States; 2Radiology, University of Michigan, ann arbor, MI, United States

We propose a field map acquisition method using a dual-echo fast field echo (DEFFE) sequence. It is advantageous that the DEFFE sequence measures an image pair with different echo times simultaneously. Consequently, there is little displacement between the images unlike the image pair measured by two separated echo sequences. However, the DEFFE introduces linear phase errors to the image pair. In this work, we present an appropriate probability density function (PDF) of nonuniform noise in the field map. Our phase correction method derived from the PDF properly removes outliers and works fine even in the presence of the wrapping effects.

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Keywords

accurately acquisition advantageous affected affine agreement alignment appropriate approximate arbor asymmetric axis back best beyond bipolar bottom brain carries cause coil complex conducted conjugate constant coordinate corrected correction corrections cross define degradation delay denote density dependent derived descent determined differentiable displacement displays dual echoes effectively efficiently empirically error errors estimation estimator extent fast field finding function generated global gradient gradients head hence homogeneous human illustrated index induced intensity inter introduce introduced lengthened likelihood linear magnitude maps masking minutes misplaced modeled motion motionless necessary newly noise noisy object oftentimes opposite outliers pair pairs phantom physical physiological plotted polarity position positive previously probable processing prone protocol proves pulse pulses radiology readout real remove removed represents residual resolution respectively scanner sections segmentation separate separately serves severe simulated simulation since specified sphere static steepest strong subject subjects suggest system taking temporal term tolerant transverse truth typically uniform unwrapping variance volume volumes whereas wrap wrapping zero