Effect of motion correction associated with echo train length and number of blades in propeller MRI-computer simulation

Abstract

The PROPELLER (periodically rotated overlapping parallel lines with enhanced reconstruction) MRI method is available with a technique for motion correction. We studied changes in correction according to differences in echo train length (ETL) and number of blades, and measured correction accuracy according to linear translation and rotation, using computer simulation. A T(2)-weighted axial image of the head taken by FSE was utilized as the basic MR image. We reconstructed other images with differences in quantity of motion, ETL, and number of blades, also using computer simulation. After motion correction was performed, we measured correction accuracy with cross-correlation to the basic image. The method of motion correction was performed by the conversion of k-space data for each blade step using 2D Fourier-transform. After motion correction of the obtained image had been carried out, the image was converted to k-space data using reverse Fourier-transform. For data of 30 pixels with horizontal translation, cross-correlation coefficients for the stationary image were 0.6 for FSE without motion correction, 0.74 for the PROPELLER (ETL 8, blades 32) image without motion correction, and 0.99 for the PROPELLER (ETL 8, blades 32) image with motion correction. For data of 24 degrees with rotation, cross-correlation coefficients were 0.38 for FSE without motion correction, 0.53 for the PROPELLER (ETL 8, blades 32) image without motion correction, and 0.93 for the PROPELLER (ETL 8, blades 32) image with motion correction. The cross-correlation coefficient of liner translation is higher than its rotation. Correction accuracy was better with larger numbers of ETL than without motion correction. The spatial resolution of the image was decreased in the corrected image more by rotation than linear translation. This study indicated that the PR method was able to inspect the imaging technique with little influence on movement.