A SIMPLE METHOD FOR THE MEASUREMENT OF LOCAL STATISTICAL NOISE-LEVELS IN SPECT

An appreciation of the magnitude and variation of local statistical noise within reconstructed SPFCT images is of importance for the interpretation of clinical data. A simple method that can be used to assess the magnitude and variation of local noise within a reconstructed section is described. This permits the application of general formulae for the prediction of noise levels to be applied to specific SPECT systems. It was found, however, that the use of real as opposed to simulated data changed the nature of the noise expression. Large errors can be obtained if the results from simulation studies are applied directly to real data. A variation in the RMS% noise of around 20% was measured within an individual section, the noise being highest towards the centre of the source distribution. The method was also used to compare the effects of different reconstruction filters. A soft Shepp-Logan filter was shown to reduce the noise level by a factor of around three when compared to the Ramp filter.