The Effect of FEW Scatter Correction Method in In-111 Imaging

Introduction: In nuclear medicine imaging, detection of the scattered photons along with the primary photons is one of the major problems that can lead to a decrease in ddiagnostic accuracy. Therefore, use of a suitable scatter correction method can help to improve of the image quality and increase of diagnostic accuracy. The aim of this study is evaluation of five energy window (FEW) method for scatter correction of In-111 imaging that can be used for evaluation of brain tumor.   Materials and Methods: For evaluation of the scatter correction method, six cold (without activity) spheres with diameters 3.2, 2.6, 2, 1.6, 1.3 and 1 cm placed in the water-filled cylindrical phantom is simulated by SIMIND Monte Carlo simulation program (version 6.1). The scatter correction is performed by setting five energy window in In-111 energy spectrum: two 20% photopeak energy window centered on E1=171 keV and E2=245keV, and three narrow energy windows, including two 8% energy window centered on lower- and upper-energy limits of the first photopeak energy window, and a 8% energy window centered on lower-energy limit of the second photopeak energy window. To evaluate the performance of the scatter correction method, the image contrasts and signal-to-noise ratios were calculated for six cold spheres.   Results: The results obtained in this study are shown that the relative increase of the image contrast of the cold sphere 1, 2, 3, 4, 5 and 6 is about 31.3, 34.16, 26.73, 4.50, 2.48 and 5.76%, respectively. The improvement in the image contrast of sphere 6 is larger than that of sphere 5 that shows the nonuniform performance of this scatter correction method. The relative noise of background for the uncorrected and the corrected images is 0.031 and 0.0878, respectively, that shows the scatter correction by the FEW method results in the increase of the image noise significantly. . Conclusion: The results of this study show that the FEW scatter correction method improves the image contrasts of six cold spheres nonuniformly with a significant increase in the level of noise