QUANTITATIVE-EVALUATION OF AN ENERGY-BASED SCATTER CORRECTION USING PLANAR ROLLO PHANTOM IMAGES

An energy-based scatter correction for SPECT and planar images is quan titatively evaluated using measured Rollo phantom data. The correction relies on model fits to the energy spectra at each pixel in a given p rojection image. For analysis purposes, a numerical model of the Rollo phantom is employed to construct a projection image corresponding to that expected from an ideal imaging system. This is then convolved wit h the measured spatial point response (in air) of the actual imaging s ystem to produce a realistic estimate of the scatter-free image. Summa ry statistics derived from comparisons between this image and the raw and scatter-corrected images are extremely reliable quantitative measu res of the detrimental effects of scatter. Position and energy (xyE) l ist mode data were acquired for several isotopes, each with 0, 5, 10, and 15 cm of Lucite intervening between the phantom and the collimator face to induce varying amounts of scatter. Analysis of the Tc-99m and Tl-201 data demonstrates a significant improvement in quantitation fo r high count images as well as for images of clinical count densities.