Purpose: There is a growing awareness that the dose a patient receives in SBRT often differs from the planned dose due to tumor motion. To improve dose accuracy, dose reconstruction should ideally occur during treatment. To address this, a real-time dose reconstruction method, DoseTracker has been developed. In a critical step to its clinical deployment, we benchmark DoseTracker against a treatment planning system (TPS)-based dose reconstruction method for prostate SBRT treatments and hypothesize that the motion-induced dose-errors determined from these two methods should agree.
Methods: Simulated real-time motion-inclusive dose reconstruction was performed using DoseTracker for nine prostate cancer patients who received IGRT with gating during five-fraction SBRT (7.25Gy/Fx) in the TROG-15.01 SPARK trial. Dose reconstruction was performed for both actual-gated (45 fractions) and simulated non-gated sessions (11 fractions). The motion-induced dose-errors were calculated as the difference between planned and motion-inclusive doses using DoseTracker and compared against the motion-induced dose-errors calculated using an iso-center shift method with a clinical TPS. The motion-induced dose-errors were computed for the clinical target volume (CTV), planning target volume (PTV), and, two risk-organs, bladder and rectum.
Results: The median computation time for each dose calculation of DoseTracker ranged from 110-320 ms for calculation volumes ranging from 287-691 cm³. The mean and standard deviation of the differences of the motion-induced dose-errors calculated using DoseTracker and the TPS were 0.02±0.01 Gy for CTV(ΔDmean), 0.02±0.01 Gy for PTV(ΔDmean), 0.04±0.07 Gy for CTV(ΔD100%), 0.03±0.06 Gy for PTV(ΔD95%), 0.02±0.02 Gy for bladder(ΔDmean) and 0.02±0.07 Gy for rectum(ΔDmean). The close agreement in motion-induced dose-errors supports the hypothesis that the performance of DoseTracker is comparable with the TPS-based method for determining motion-induced dose deterioration.
Conclusion: DoseTracker accurately determined motion-induced dose-errors in real-time for a lower pelvic tumor site. This study demonstrates that clinical implementation of real-time motion-inclusive dose reconstruction with DoseTracker is feasible.
Funding Support, Disclosures, and Conflict of Interest: P Keall is supported by an NHMRC Investigator (L3) grant. D T Nguyen is supported by NHMRC and Cancer Institute NSW Early Career Fellowships. Nguyen, O'Brien, Poulsen, and Keall are listed inventors on KIM-related patents. Nguyen and Keall are stock-holders of SeeTreat Pty.
Not Applicable / None Entered.