Optimization of a limited-angle intrafraction verification (LIVE) system for target localization in radiation therapy of lung cancer

Abstract

Purpose: A novel limited-angle intrafraction verification (LIVE) system has been developed recently for fast 4D intrafraction target verification in lung SBRT treatments. LIVE acquires orthogonal limited angle kV and MV cone beam projections simultaneously during an arc treatment delivery or in-between static beams. A prior knowledge based image reconstruction technique reconstructs 4D images by deforming prior images based on a deformation model. The main goal of the project is to optimize the acquisition parameters of the LIVE system for different patient and treatment scenarios so that LIVE can be implemented effectively for clinical usage in the future. Methods: The LIVE system was optimized with XCAT simulation and the preliminary evaluation was divided into XCAT simulation and CIRS phantom study. The evaluation metrics used were volume percentage difference (VPD) and center of mass shift (COMS). The acquisition parameters of LIVE, including scan angle, projection number, scan speed and scan direction, were optimized for different patient scenarios using XCAT simulation to improve the accuracy and efficiency of the system in localizing the lung tumor. The optimized LIVE system was further evaluated using the CIRS motion phantom. The corresponding imaging dose of the LIVE system was also evaluated.Results: Acquisition parameters, including kV/MV projection numbers and number of respiratory cycles, were optimized for different patient and treatment scenarios. A clinical reference table was developed as a guideline for the optimal parameters of the LIVE system for its future clinical implementation. The robustness of the LIVE system against tumor size and tumor location changes was also validated. Conclusion: The LIVE system has been preliminarily optimized based on simulation and phantom studies. Results demonstrated its potential for intrafraction verification under different clinical scenarios. Future patient studies are warranted to further evaluate the system for its clinical applications.