SU‐E‐J‐150: Investigation of Feasibility of Concurrent Orthogonal KV and MV X‐Ray Imaging for Tagrget Tracking During Dose Delivery for Stereotactic Body Radiotherapy (SBRT): A Pilot Phantom Study

Abstract

Purpose: To investigate feasibility of motion tracking using concurrent orthogonal kV and MV x‐ray images acquired during dose delivery for stereotactic body radiotherapy (SBRT).Method and Materials: The study was performed on a Varian TrueBeam treatment unit, which is equipped with research capability. The research capability allows users to program a procedure of treatment and imaging that are unavailable in conventional clinical environment. The concurrent orthogonal kV and MV x‐ray imaging is novel and provides 3‐dimentional spatial information in real‐time during radiation delivery. In this study, concurrent orthogonal kV and MV x‐ray imaging was programed to be part of 3D‐conformal SBRT delivery and are used for assessment on accuracy of traget motion tracking during radiation delivery. Two experiements were carried out on a CIRS dynamic thorax phantom with a built‐in BB as a tartget: one without motion; the other with motion in a sinusoidal profile with the motion amplitude of 16.0 mm. The motion trajectories acquired by the concurrent orthogonal kV and MV x‐ray imaging were compared against the references. In the work, the discrepancies were quantified using mean and standard deviation (SD). Results: The trajectory profiles acquired by the the concurrent orthogonal kV and MV x‐ray imaging show good agreement with references. A quantitative analysis shows that the average mean discrepancy between kV imaging and known references is 0.0+/−0.2 mm and 0.2+/−0.3 mm for stationary and sinusoidal motion conditions. Similarly, the average mean discrepancy between MV imaging and known references and MV is 0.1+/− 0.2 mm and 0.3+/−0.5 mm for stationary and sinusoidal motion conditions. Conclusion: The results indicate the concurrent orthogonal kV and MV x‐ray imaging can track motion and provide target targeting during radiation delivery with reasonable accuracy. Further work is required to investigate in arc mode and gating delivery mode.