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MV and KV Imagingdose Resulting From 4D Target Verification Using the Limited-AngleIntra-Fractional Verification (LIVE) System for SBRT Lung Treatment

G Ding

G Ding1*, Y Zhang2 , L Ren2 , (1) Vanderbilt University , Nashville, TN, (2) Duke University Medical Center, Durham, NC


WE-RAM3-GePD-J(A)-6 (Wednesday, August 2, 2017) 10:30 AM - 11:00 AM Room: Joint Imaging-Therapy ePoster Lounge - A

Purpose: The Limited-angle Intra-fractional Verification (LIVE) system was developed to track tumor movement for patient positioning verification during arc treatment delivery or between 3D/IMRT treatment fractions during SBRT. The 4D MV/kV imaging involved may result in additional (imaging) dose to patients. This study evaluated additional dose resulting from typical optimized MV/kV image acquisition in the LIVE system.

Methods: The TrueBeam™ platform with fully-integrated system for image guidance was studied. Monte Carlo simulated kV and MV beams were calibrated and then used as incident sources in an EGSnrc Monte Carlo dose calculation in a CT-image-based patient model. In the representative lung SBRT treatment evaluated in this study, a small tumor was located in the patient’s posterior-left lung. The optimized imaging sequence comprised 7 arcs, applied between adjacent 3D/IMRT beams, with 30 simultaneous kV (110 kVp) and MV (6 MV) image projections in each arc, for a total of 210 projections at both kV and MV energies. The MV imaging fields were confined to the treatment target while kV images were acquired with an open field and a full bow-tie filter.

Results: The kV imaging doses to 50% of the tissue volume (D50 from DVH’s), for the target, left lung, heart, right lung and spinal cord were 0.28 cGy, 0.37 cGy, 0.32 cGy, 0.16 cGy and 0.12 cGy, respectively. The corresponding MV imaging doses were 136.1 cGy, 0.26 cGy, 0.26 cGy, 0.19 cGy and 0.22 cGy respectively.

Conclusion: The kV imaging doses are comparable to those resulting from a single Thorax kV-CBCT scan and are not clinically significant. Although the MV imaging dose to the target is high it can be integrated into the total target dose during treatment planning.

Funding Support, Disclosures, and Conflict of Interest: The research is supported by NIH Grant No: R01 CA-184173

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