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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

Z Chang

Z Chang*, H Yan, F Yin, Duke University Medical Center, Durham, NC

SU-E-J-150 Sunday 3:00PM - 6:00PM Room: Exhibit Hall

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.


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