Collection and analysis of photon beam data for Varian C-series linear accelerators: a potential reference beam data...

Area of Science:

• Medical Physics
• Radiotherapy Physics

Background:

• Varian C-series linear accelerators are widely used in radiotherapy.
• Accurate commissioning of radiotherapy treatment planning systems (RTPS) is crucial for patient safety.
• Establishing reliable reference beam data is essential for RTPS commissioning verification.

Purpose of the Study:

• To collect and analyze photon beam data for Varian C-series linear accelerators.
• To evaluate the suitability of average beam data as reference data for RTPS commissioning.
• To assess the consistency of beam data across different institutions.

Main Methods:

• Collected 20 datasets for 4 and 6 MV, and 40 datasets for 10 MV photon beams from 20 institutions.
• Data included percent depth dose (PDD), off-center ratio (OCR), and output factor (OPF).
• Calculated average values for each data type and analyzed dose differences and relative differences.

Main Results:

• Dose differences for PDD in the fall-off region were <1.0%.
• Relative differences for OPF were within 1.0% for all energies and field sizes.
• Standard deviation for OCR in flat regions was within 1.0%, with a minor exception for a specific field size. OCR penumbra regions showed agreement within 1.0 mm.

Conclusions:

• Average photon beam data from Varian C-series machines demonstrate high consistency across institutions.
• This average data, excluding small field sizes, is suitable for use as reference beam data for RTPS commissioning verification.
• The findings support the use of pooled data for quality assurance in radiotherapy.