Energy Window and Contrast Optimization for Single-photon Emission Computed Tomography Bremsstrahlung Imaging with Yttrium-90

PURPOSE: In yttrium-90 (Y-90) single-photon emission computed tomography (SPECT) imaging, the choice of the acquisition energy window is not trivial, due to the continuous and broad energy distribution of the bremsstrahlung photons. In this work, we investigate the effects of the energy windows on the image contrast to noise ratio (CNR), in order to select the optimal energy window for Y-90 imaging. MATERIALS AND METHODS: We used the Monte Carlo SIMIND code to simulate the Jaszczak phantom which consists of the six hot spheres filled with Y-90 and ranging from 9.5 to 31.8 mm in diameter. Siemens Symbia gamma camera fitted with a high-energy collimator was simulated. To evaluate the effect of the energy windows on the image contrast, five narrow and large energy windows were assessed. RESULTS: The optimal energy window obtained for Y-90 bremsstrahlung SPECT imaging was 120–150 keV. Furthermore, the results obtained for CNR indicate that the high detection is only for the three large spheres. CONCLUSION: The optimization of energy window in Y-90 bremsstrahlung has the potential to improve the image quality.