Linear back projection technique

A simple method of recovering the truncated data is to linearly extrapolate the truncated CT projections to the extent of PET FOV and then setting the values to zero at the edge of the PET FOV. The attenuation correction by this method is adequate to remove the truncation artifacts in PET/CT images (Fig. 3.15). Using the iterative method rather than the filtered back projection technique also has shown to help to eliminate these artifacts. 

The transverse images of cold and hot regions insert were obtained by the filtered back projection image reconstruction technique. It was corrected for uniformity and center of rotation (COR). Chang s attenuation correction method was applied by choosing 0.111, 0.121, 0.131, 0.141 and 0.151 cm linear attenuation coefficient values. Butterworth filter with cut off frequency 0.35 cycles/cm and order 5 was used. Scatter correction technique was not applied due to non-availability with this gamma camera system. 

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