ADDITION OF NOISE BY SCATTER CORRECTION METHODS IN PVI

Effective scatter correction techniques are required to account for er rors due the high scatter fraction seen in positron volume imaging (PV I). To be effective, the correction techniques must be accurate and pr actical, but they also must not add excessively to the statistical noi se in the image. We have investigated the noise added by three correct ion methods: a convolution/subtraction method; a method that interpola tes the scatter from the events outside the object; and a dual energy window method with and without smoothing of the scatter estimate. The methods were applied to data generated by Monte Carlo simulation to de termine their effect on the variance of the corrected projections. The convolution and interpolation methods did not add significantly to th e variance. The dual energy window subtraction method without smoothin g increased the variance by a factor of more than twelve, but this fac tor was improved to 1.2 by smoothing the scatter estimate.