SU-D-500-06: On-Board Robotic Multi-Pinhole SPECT System for Prone Breast Imaging

Abstract

Purpose: To investigate a novel Single Photon Emission Computed Tomography (SPECT) system for on‐board molecular and functional imaging in partial breast radiation therapy of prone patients. Methods: Computer‐simulation studies were performed for on‐board robotic 49‐pinhole and reference conventional clinical parallel‐hole collimated SPECT systems. A female XCAT phantom was simulated in prone position with nine tumors of 10mm diameter in the left breast. The simulations included two commercial prone breast boards, 24 and 7 cm thick. Four‐minute trajectories of the 49‐pinhole and parallel‐hole systems were designed to image a 7cm‐diameter target region encompassing the tumors. Noisy Poisson‐distributed projection data were drawn from these simulated projections, and SPECT images were reconstructed by OSEM with up to 10 iterations. Images were evaluated by visual inspection, profiles, and root mean squared error (RMSE). Results were correlated with trajectory radii of rotation. Commercial CAD programs were utilized to evaluate the feasibility of robot and detector trajectories about the patient, treatment table, prone breast board and LINAC gantry. Results: With 4‐minute scans of the proposed 49‐pinhole SPECT system, using the thinner prone breast board, almost all of the 9 tumors were well visualized above background. Few if any of the tumors were apparent in the parallel‐hole images. With the thinner board, lowest RMSE values, across all iterations, were 0.206 for 49‐pinhole and 0.251 for parallel‐hole. For the thicker board, these RMSE results were 0.234 and 0.260 respectively. These results correspond to smaller radii of rotation with the thinner board. CAD simulations indicate feasibility in terms of geometrical considerations. Conclusion: The proposed on‐board robotic multi‐pinhole SPECT approach shows promising results for targeted molecular and functional imaging of the breast as patients are in prone position for radiation therapy, especially with breast boards that allow closer detector proximity. PHS/NIH/NCI grant R21‐CA156390‐01A1