R Zhang¹*, B Clasie² , N Depauw³ , Y Lin⁴ , T Shen⁵ , J Flanz⁶ , H Lu⁷ , K Jee⁸ , (1) Massachusetts General Hospital, Quincy, MA, (2) Massachusetts General Hospital, Boston, MA, (3) Massachusetts General Hospital, Boston, MA, (4) Duke University Medical Center, Durham, NC, (5) Massachusetts General Hospital, Boston, Massachusetts, (6) Massachusetts General Hospital, Boston, MA, (7) Massachusetts General Hospital, Boston, MA, (8) Massachusetts General Hospital, Boston, MA

• 
  R Zhang

(Sunday, 7/29/2018) 3:00 PM - 6:00 PM

Room: Exhibit Hall

Purpose: As Pencil Beam Scanning (PBS) is being widely accepted as the deliver technique in proton therapy, the high degree of quality assurance (QA) is critical to ensure the quality and safety of its delivery. Due to the complexity of the PBS system, conventional dosimetry-based QA program may not sufficiently provide comprehensive checks of the system. Here, we propose to overcome the limits of the present dosimetry-based QA by analyzing extensive operational parameters extracted from the machine log files.

Methods: For given PBS fields, log files of the delivery were retrieved from the treatment control system of proton therapy system. Subsequently, parameters including the charge, width, position (measured by chambers in the nozzle), energy and magnetic field of the scanning magnets were automatically extracted for individual spots. By using an in house developed program, charges and positions of all recorded spots were derived at the iso-center plane and compared with corresponding values from the treatment planning system (TPS). Spots causing pauses and failures were automatically identified for the analysis of failure modes.

Results: For the daily QA fields, operational parameters were archived in structured data. Long-term trends of the operational parameters can be monitored. For a given field, spots causing delivery pauses and failures were automatically identified, providing diagnostic information for the analysis of failure modes. Derived charges and positions at the iso-center plane based on data in the log files were compared with corresponding values from the TPS, which served as a supplementary check to the dosimetry-based QA.

Conclusion: This study validated that, being supplementary to the present dosimetry-based QA, machine log file analysis has the potential to provide comprehensive checks of the operational parameters and diagnostic information of the failure modes.

Keywords

Protons, Quality Assurance

Taxonomy

TH- External Beam- Particle therapy: Proton therapy - quality assurance

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