Sources and correction of higher-order geometrical distortion for serial MR brain imaging
- 3 July 2001
- proceedings article
- Published by SPIE-Intl Soc Optical Eng
- Vol. 4322, 69-78
- https://doi.org/10.1117/12.431151
Abstract
A specially designed phantom consisting of a 3D array of 427 accurately manufactured spheres together with a point-based registration algorithm was used to detect distortion described by polynomial orders 1-4. More than thirty 3D gradient echo (FFE) and multi-slice spin echo (SE) phantom scans were acquired with a Philips 1.5T Gyroscan. Distortion was measured as a function of: readout gradient strength (0.72<= Gr <=1.7mT/m), TR/TE/flip angle, shim settings, and temporal distortion change for 11 weekly scans for the FFE sequence and TR/TE/slice gap for SE. Precision measurements for linear distortion were: scale <=0.03%, shear <=0.04 degrees. Linear distortion in the readout dependent directions increased with decreased readout strength (r>0.93). There was a significantly higher (pr - possibly because of slice selection. Different shim settings produced only linear distortion change: up to 2% scale and 1 degree shear. There was negligible distortion change over time: scale < 0.1%, shear <= 0.05 degrees. There was a decrease in distortion as a function of polynomial order (r>0.9, n=33), 75% of the distortion was either first or second order.This publication has 0 references indexed in Scilit: