SCATTER CORRECTION FOR 3-DIMENSIONAL PET BASED ON AN ANALYTIC MODEL DEPENDENT ON SOURCE AND ATTENUATING OBJECT

Three-dimensional positron emission tomography admits a significant sc atter fraction due to the large aperture of the detectors, and require s accurate scatter subtraction. A scatter-correction method, applicabl e to both emission and transmission imaging, calculates the projection s of the single-scatter distribution, using an approximate image of th e source and attenuating object. The scatter background is subtracted in projection space for transmission data and in image space for emiss ion data yielding corrected attenuation and emission images. The accur acy of this single-scatter distribution is validated for our small ima ging system by comparison with Monte Carlo simulations. The correction is demonstrated using transmission and emission data obtained from me asurements on our QPET imaging system using two acrylic phantoms. For the transmission data, generated with a flood source, errors of up to 24% in the linear attenuation coefficients resulted with no scatter su btraction, but the correction yielded an accurate value of mu = 0.11 /- 0.01 cm(-1). For the emission data, the corrected images show that the scattered background has been removed to within the level of the b ackground noise outside the source. The residual amplitude within a co ld spot in one of the phantoms was reduced from 21% to 3% of the image amplitude.