Log File-Based Efficient Machine Transfer Process for Patients Treated on Helical Delivery Systems
Abstract
Purpose
In clinics operating multiple helical delivery systems, treatment plan transfer between machines is frequently desired to improve scheduling flexibility. Despite beam matching, vendor guidance commonly recommends repeating full patient-specific IMRT QA after each plan transfer, increasing workload and consuming valuable treatment machine time. This work establishes an efficient and standardized machine-transfer workflow for helical delivery systems that maintains dosimetric accuracy and delivery confidence while reducing machine utilization.
Methods
A prospective transfer workflow was implemented for two Radixact® (Accuray) systems and applied to all patients scheduled on either machine. After physician approval, plans were transferred to the alternate machine on the Precision TPS. Transferred plan doses were exported to MIM (MIM Software) and compared with the original planned dose using gamma analysis (0.5mm/0.5%). Patient-specific IMRT QA (3mm/3%) was performed only for the original plan using ArcCheck (Sun Nuclear). Automated quality checklist items triggered in-air delivery of transferred plans on the destination machine. Delivered plans were reconstructed using gantry, couch, and MLC positional data from delivery log files, and dose reconstruction was performed in MIM SureCalc. Reconstructed doses were compared with transferred planned doses using gamma analysis (2mm/3%). Ten clinical cases (pelvis, prostate, pancreas, brain, head and neck, extremity) were evaluated, and workflow timing was recorded.
Results
Dose comparisons between original and transferred plans demonstrated excellent agreement (gamma pass rate: 98.83–99.91%). Log-file-based reconstructed dose comparisons showed passing rates of 91.01–100.00%. ArcCheck IMRT QA passing rates for transferred plans ranged from 95.5–100.0%. Plan reconstruction required <20 s, while SureCalc dose calculation required 3–11 min. Eliminating repeated phantom-based QA on the destination machine avoided approximately 15 min of additional machine time per patient.
Conclusion
This workflow enables safe and efficient machine transfer for helical delivery systems, improving treatment machine availability and operational flexibility while maintaining high dosimetric confidence.