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Independent dose verification for brain stereotactic radiotherapy using different add-on micro multi-leaf collimators
Shiro Nishiyama1, Satoru Ishibashi2, Ryo Takahashi3
1Department of Radiology, Kuki General Hospital, Kuki, Saitama, 346-8530, Japan.
Radiological Physics and Technology
|April 21, 2017
Summary
This study validates a dose calculation verification system for brain stereotactic radiosurgery (SRS) and stereotactic radiotherapy (SRT) using micro multi-leaf collimators (mMLC). Researchers propose a tolerance of 2-3.5% for accurate treatment delivery.
Area of Science:
- Medical Physics
- Radiotherapy Physics
- Radiation Oncology
Background:
- Micro multi-leaf collimators (mMLC) are utilized in stereotactic radiosurgery (SRS) and stereotactic radiotherapy (SRT) for brain treatments.
- Rotational radiotherapy techniques can increase treatment complexity and duration.
Purpose of the Study:
- To assess the accuracy of an independent dose calculation verification system for brain SRS and SRT.
- To propose a suitable tolerance value for dose verification in these treatments.
Main Methods:
- A retrospective study involving two institutions comparing static and patient-specific plans.
- Utilized phantom measurements and patient CT images for dose calculation verification.
- Evaluated Clarkson-based dose calculation accuracy using equivalent square fields and collimator scatter factors (Sc).
Main Results:
- Static plans showed good agreement (<1%), with exceptions for small field sizes (1 cm² <4%).
- Patient plans demonstrated deviations of 0.1 ± 2.3% (TPS) and 1.2 ± 1.6% (2 SD) for the verification system.
- Patient plans showed an overall deviation of 2.0 ± 2.1% (2 SD).
Conclusions:
- The study suggests a tolerance level of 2-3.5% for brain SRS and SRT dose verification.
- Accurate calculation of the collimator scatter factor (Sc) based on the mMLC is crucial.
- Treatment planning system beam modeling significantly influences dose calculation deviations.