Scatter Correction with Dual Energy Window Method in SPECT and Investigation the effect of scatter correction on Image Contrast value in Reconstructed Data

Present of scattered photons result in decreasing of image contrast and quality in SPECT. In this investigation, 99mTc is used for phantom studies. Compensation method is included two energy windows in 99mTc energy spectrum: a main window is centered in photopeak energy (126-154keV) and the other, scatter window placed in Compton energy spectrum region (92-125keV). This method is based on this assumption that the scatter counts in photopeak window are as “k” times the scatter window counts [1-5]. “k” scatter factor is calculated using water-filled Jaszczak phantom with the known activity (3.43 mCi Tc-99m). The phantom consisted of six solid spheres (diameters 5.9 ,9.2 ,11.4 ,14.3, 17.9, 22.4 mm) placed within a cylindrical (21.6 cm diam) distribution of Tc-99m. Either projections or tomogras are corrected. The “k” main values are determined for per –and post processing data 1 and 0.99 respectively. The results of this study shows that use of scatter correction results in increasing of image contrast, quality and quantitaty. Also “k” values are different for each view in projections and also that is different for slices in reconstructed data. “k” value of 0.5 previously reported by jaszczak et al and else ever.