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Distance from Center of Source (cm)

Figure 8. Tangential (top row), radial (middle row) and axial (bottom row) profiles through reconstructed point sources of Fig. 5 for LEGP (left) and LEHR (right) collimators. The distance from the center of rotation to the point, d, is indicated in the legend. The profile for each point is normalized to unit intensity.

data are noisy and the high frequencies of the image, whether projections or reconstructed image, will be dominated by noise. One solution to both of these problems is to roll off the high frequencies using a low pass filter. Two forms of low pass filters have been applied in SPECT, the Metz and Wiener Filters. The Metz filter, Metz(v), has the form:

where n > 1 is the order of the filter. The term in the square brackets acts as a low-pass filter. For n = 1, the filter becomes CDRF( v) and is often called a

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