Seven-pinhole versus Single-pinhole SPECT for Thyroid Imaging

To compare 7-pinhole and single-pinhole SPECT thyroid imaging under conditions of equal total detector area. A phantom was generated using XCAT software. Trajectories of 7-pinhole and single-pinhole detectors were developed for 2 scenarios: (i) minimum radius of rotation (D_PH) for fully viewing a target imaging sphere containing the thyroid and (ii) minimum radii of rotation for fully viewing the target imaging sphere and avoiding collision with the patient. Projection data were computer-simulated and images were reconstructed modeling attenuation, spatial resolution, and Poisson noise. Seven-pinhole and single-pinhole systems were compared for a range of lesion-activity concentrations, pinhole diameters, and half opening angles. Comparison metrics included system resolution, geometric sensitivity, and image quality. In the absence of collision constraints, 7-pinhole systems show potential to provide better trade-offs between geometric sensitivity and spatial resolution. However, when pinhole trajectories are constrained to avoid patient collision, 7-pinhole systems may be affected more adversely than single pinhole systems. The study points to the potential of 7-pinhole systems and to the importance of addressing collision constraints.