Optimal energy window for scatter correction in I-131: GATE simulation study

Gamma camera imaging is one of prevalent diagnostic imaging tool for nuclear medicine. Although gamma camera imaging widely used for diagnostic imaging, quantification of gamma camera imaging is difficult due to scattered radiation. Compton scattering is always a problematic phenomenon in gamma camera imaging. In previous study, Siemens symbia scintillation camera was modeled for assessment of septal penetration photons and validation of Monte Carlo simulation code for the Siemens scintillation camera. In this study, optimal energy window for triple energy window (TEW) scatter correction method was assessed in gamma camera for ^99mTc, ¹³¹I radioisotopes using GATE simulation. Siemens Symbia T2 SPECT/CT scanner was used throughout to acquire planar data. These dataset were then reconstructed by FBP. Energy window was set for various main energy window width (10, 15, 20%) and sub energy window width (3 and 5keV). The point source was positioned at 8 positions. The triple energy window method estimated the scatter fraction in the photopeak from the counts acquired in two adjacent narrow windows. Linear interpolation between the two sub-windows could be used to obtain the following trapezoidal approximation of the scatter counts: C_s = (C_left/W_s + C_right/W_s) × W_m/2 For ^99mTc, 20% of main energy window and 5 keV of sub energy window and For ¹³¹I , 10% of main energy window and 5 keV of sub energy window was optimal for implementation of TEW. This result of present study provide optimal energy window for ¹³¹I scintigraphy data and would be helpful for quantification of ¹³¹I. Further study, experimental study will be performed for validation of this simulation result.