A NEW PHANTOM FOR FAST DETERMINATION OF THE SCATTER RESPONSE OF A GAMMA-CAMERA

A triangular phantom is proposed which enables the determination and parameterization of the depth dependent scatter response function (SRF) in uniformly attenuating objects for Single Photon Emission Computed Tomography (SPECT) by means of a single line source measurement. This approach replaces a tedious measurement series with line sources at various depths in slab phantoms. The method is evaluated for Tc-99m. Monte Carlo simulations of SRFs and scatter-to-primary ratios (SPRs) of the triangular phantom are compared with those of slabs. It is found that both the SPRs and the shapes of the SRFs from the slab and triangular phantoms are in excellent agreement. In addition, the data obtained from a single measurement using the triangular phantom can be used in the parameterization of the slab phantom SRF and can be described by an analytical expression of the line source response function. This information can be combined with knowledge of the geometric detector response and the shape of the object to compute the full scatter response function in convex shaped objects. This method for estimating scatter can serve as the basis for accurate scatter compensation in SPECT.