Clinical Implementation of a Model-Based In Vivo Dose Verification System for Stereotactic Body Radiation
Peter M McCowan1, Ganiyu Asuni1, Eric Van Uytven2
1Medical Physics Department, CancerCare Manitoba, Winnipeg, Manitoba, Canada.
Summary
This study evaluated in vivo dosimetry for stereotactic body radiation therapy patients using electronic portal imaging devices (EPID). The implemented program successfully verified delivered radiation doses and identified treatment errors, improving patient safety.
Area of Science:
- Medical Physics
- Radiation Oncology
- Dosimetry
Background:
- Stereotactic body radiation therapy (SBRT) requires precise dose delivery.
- In vivo dosimetry verifies the actual dose received by patients during treatment.
- Electronic portal imaging devices (EPID) offer a potential tool for real-time dose verification.
Purpose of the Study:
- To report findings from an in vivo dosimetry program for SBRT patients.
- To discuss the clinical value and challenges of using EPID dosimetry.
- To assess the effectiveness of a model-based dose reconstruction algorithm.
Main Methods:
- Implemented a 31-month in vivo dosimetry program for 117 SBRT patients.
- Utilized EPID-based measurements and a model-based dose reconstruction algorithm.
- Performed 3%/3-mm gamma (γ) comparisons between EPID-derived and predicted doses, with defined alert levels.
Main Results:
- Post-optimization, lung, spine, and liver treatments showed reduced fractions exceeding alert levels (8.0%, 20.0%, 10.0% respectively).
- Mean planning target volume (PTV) γ pass rates were 90.7% (lung), 87.0% (spine), and 91.2% (liver).
- The EPID dosimetry program successfully detected treatment errors and verified delivered doses.
Conclusions:
- Clinical implementation of model-based in vivo EPID dosimetry is valuable for routine dose verification.
- The method effectively detects errors in SBRT treatments.
- EPID dosimetry enhances the safety and accuracy of radiation therapy delivery.
