Purpose: To quantitatively evaluate the reproducibility of patient breathing between the calculated phase from respiratory signal and RPM (real‐time position management system, Varian Medical Systems, Palo Alto, CA) within treatment. We developed an independent retrospective verification system (RVS) for gated‐radiotherapy using full signal and gating window in RPM system. Methods: RVS was programmed by LabVIEW 2009 with wavelet‐based multi‐resolution analysis, which is a useful and accurate technique for identifying peaks and valleys of noisy signals. The respiratory signal and real‐time calculated phase information from RPM was exported to RVS as a text file. Using this text file, several respiratory parameters were calculated by RVS, and were compared with the generated parameters from RPM. The evaluated parameters included phase‐shift, total displacement, residual motion, baseline shift, and so forth. The analysis was conducted for both in‐gate and full respiratory signal separately. The analysis report was automatically generated in Excel file format. Eleven patients of abdominal cancer were retrospectively analyzed for the evaluation. Results: The mean phase error of gated signal and full signal between RPM and our software ranged from 1.50% to 3.08% and 1.52% to 3.08%, respectively. Average phase shift was not significant but in‐gate phase difference between RVS and RPM was found to be higher than 4% in two cases. At times, real‐time phase calculation from RPM caused the beam to be turned on at incorrect time of the breathing cycle when the patient breathing was not regular. The total displacement varied from 0.672 cm to 1.732 cm, which showed patient‐specific baseline shift during treatment. Conclusion: The developed software demonstrated competency in analyzing RPM signal and evaluating patient‐specific respiratory parameters of radiotherapy. Thus, it can be used as an independent quality assurance tool for RPM phase‐based gating treatment.
ASJC Scopus subject areas
- Radiology Nuclear Medicine and imaging