A High-Resolution Portable Gamma-Camera for Estimation of Absorbed Dose in Molecular Radiotherapy

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Molecular radiotherapy is a treatment modality that requires personalized dosimetry for efficient treatment and reduced toxicity. Current clinical imaging systems and miniaturized gamma-cameras lack the necessary features for this task. In this paper, we present the design and optimization of a mobile gamma-camera with a 10×10 cm field of view tailored for quantitative imaging during 131I therapy of thyroid diseases. The camera uses a monolithic 10×10×1 cm CeBr3 scintillator coupled to a 16×16 SiPMs array and commercial electronics. It exhibits high imaging performance with an intrinsic spatial resolution of 1.15 mm FWHM, an energy resolution of 8% FWHM at 356 keV and negligible deadtime up to 150 kcps. Images are reconstructed in real time using a convolutional neural network. The manufacturing method of tungsten collimators and shielding was optimized using laser 3D printing to achieve an effective density of 97% that of bulk tungsten. Their geometry was adjusted with Monte-Carlo simulations in order to reduce septal penetration and scattering and optimize the signal-to-noise ratio at short times after treatment administration. Two high-energy parallel-hole collimators with high sensitivity or very high spatial resolution were designed for treatment planning and post-treatment control. The fully operational gamma-camera will soon be clinically assessed.