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Individualized breathing trace quality assurance for lung radiotherapy patients undergoing 4DCT simulation
James Rijken1, Yunfei Hu2, Kelvin Hiscoke3
1Icon Cancer Centre, Windsor Gardens, South Australia, Australia.
Journal of Applied Clinical Medical Physics
|February 22, 2023
Summary
Quality assurance for 4DCT lung cancer radiotherapy is crucial. Individualized quality assurance of patient breathing traces minimizes significant uncertainties in treatment planning and delivery.
Area of Science:
- Medical Physics
- Radiotherapy Technology
- Image Guidance
Background:
- Four-dimensional computed tomography (4DCT) is vital for lung cancer radiotherapy, enabling visualization of tumor motion during breathing.
- The accuracy of 4DCT image reconstruction relies on breathing trace data, yet routine quality assurance (QA) is lacking.
- Current methods for analyzing breathing traces lack standardization and robust recommendations.
Purpose of the Study:
- To develop and validate a method for quantifying patient breathing trace metrics from 4DCT simulations.
- To assess the impact of breathing trace variability on radiotherapy treatment planning accuracy.
- To establish the necessity for individualized quality assurance in 4DCT radiotherapy.
Main Methods:
- Developed a Windows application in C# to analyze Varian RPM/RGSC VXP breathing trace files.
- Quantified key breathing metrics including phase, amplitude, and breaths per minute (BPM).
- Evaluated potential errors in target delineation and dose delivery for lung cancer patients based on breathing trace analysis.
Main Results:
- Significant discrepancies were observed between RGSC and the developed application's phase calculations.
- Without individualized QA, average phase calculation accuracy is within 19% of actual phases.
- Breathing rate (BPM) variation introduces a 37% error, amplitude uncertainty is 34%, and misbinning can lead to missing 66% of the target.
- Voluming errors, specifically underestimation of the planning target volume (PTV), can reach 11% without QA.
Conclusions:
- Individualized quality assurance of patient breathing traces is essential for accurate radiotherapy.
- Lack of QA introduces significant uncertainties in phase and amplitude metrics, impacting clinical treatment.
- Implementing routine, individualized QA ensures precise quantification of patient-specific uncertainties for improved treatment outcomes.
