Collimator and energy window optimization Ga-67 imaging: A Monte Carlo study

INTRODUCTION: Ga-67 imaging is affected by collimator penetration and scatter components due to high energy gamma-ray emissions. The characterization of penetration and scatter distribution is important for optimization of collimator design and development of correction method. This study proposes to compare the image quality that can be achieved by three collimators.
METHODS: The simulation was carried out for LEHR(Low Energy High Resolution), ME(Meduim Energy) and HE(High Energy) collimators for Ga-67 point source placed at 12 cm from the detector surface using Monte Carlo SIMIND simulation code. Their spectrums, point spread functions and also geometric, penetration, scattering and x-rays curves were drawn and analyzed. FWHM (full width at half maximum) and FWTM(full width at tenth maximum) were also investigated.
RESULTS: The geometric, penetration, and scatter within 10% for LEHR were 34,46 %, 33,52%, 17,29% and 14,72% respectively. Similarly, geometric, penetration, scatter and x-rays within 10% for ME and HE were 83,06%, 10,25%, 6,69% and 0% and 81,44%, 11,51%, 7,05% and 0%. The tradeoff between spatial resolution and sensitivity is achieved by using the ME collimator, with the 185 photopeak of Ga-67.
DISCUSSION AND CONCLUSION: The Monte Carlo simulation results can be used for optimal collimator design and development of new correction method in Ga-67 imaging.