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Commissioning and clinical implementation of Mobius3D and MobiusFX: Experience on multiple linear accelerators
Jihun Kim1, Min Cheol Han1, Kwangwoo Park1
1Department of Radiation Oncology, Yonsei University College of Medicine, Seoul, South Korea.
Summary
Commissioning Mobius3D for patient-specific quality assurance requires careful beam model adjustment and dosimetric leaf gap (DLG) optimization. DLG optimization results depend on VMAT plan selection, especially for small fields where Mobius3D has uncertainties.
Area of Science:
- Medical Physics
- Radiation Oncology
- Quality Assurance
Background:
- Patient-specific quality assurance (QA) is crucial for safe and effective radiation therapy.
- Mobius3D and MobiusFX are tools used for patient-specific QA in radiation therapy.
- Commissioning these tools ensures accurate dose calculations.
Purpose of the Study:
- To establish practical guidelines for Mobius3D commissioning.
- To leverage experiences from commissioning Mobius3D and MobiusFX on multiple linear accelerators.
- To optimize Mobius3D as a patient-specific QA tool.
Main Methods:
- Vendor-suggested commissioning procedures for Mobius3D were followed.
- Beam model adjustment involved measuring percentage depth dose, off-axis ratio (OAR), and output factor (OF).
- Dosimetric Leaf Gap (DLG) optimization was performed using volumetric modulated arc therapy (VMAT) plans to minimize dose calculation differences.
Main Results:
- Measured beam data were consistent across six Elekta linear accelerators.
- Discrepancies were noted in OAR at large off-axis distances and OF for small fields.
- Optimal DLG correction factors varied, being higher when small-field plans were included (0.6 ± 0.3) versus excluded (0.2 ± 0.2).
Conclusions:
- A reasonable agreement exists between vendor-provided and measured beam models.
- DLG optimization is sensitive to the VMAT plans used.
- Careful consideration of Mobius3D's dose calculation uncertainties is necessary for accurate DLG factor determination.
