Preprocessing Steps on Fourier MRI Raw Data

Summary

In MR Imaging the signals arising from the excited nuclei yield the information of the spatial spin distribution in form of a (2d or 3d) interferogram. Therefore the Fourier transform of the sampled data directly results in an image.

It will only be free of artifacts if the MR machine creates ideal raw data. In reality we cannot expect ideal behavior of the hardware, so corrections of the measured data are necessary.

The effect of the following raw data nonidealities on the image are shown:

• 1. Offset caused by bias voltages of the data aquisition system.

• 2. Phase and amplitude deviations of the quadrature demodulator.

• 3. Nonequidistancy of the sampled data points caused by gradient ripple.

To reduce or eliminate the resulting artifacts, appropriate preprocessing steps are introduced to the reconstruction program. The image quality improvements are demonstrated by experiment or simulation.