MR Image Reconstruction from Raw Data


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Raw Data in
Spatial Frequency Domain
What operation must be performed to reconstruct the image?

Fourier Transform (FT) 
Reconstructed Image in
Spatial Domain
In MRI, the raw data is acquired in spatial frequency space, as shown above on the left.  Notice that most of the raw data is centered about the origin of frequency space.  Low spatial frequencies contain most of the information about the image, including gross structural features and contrast.  On the other hand, high spatial frequencies at the periphery of frequency space contain information about fine details and edges -- places in the image where the signal intensity varies abruptly from one pixel to the next.  A 2-D Fourier Transform (FT) is applied to the raw data to reconstruct the image from the spatial frequency data.  The reconstructed image is a phantom object used for testing purposes in MRI, with components of varying size, shape, and material.

Now let's look at filtering...