Experimental small field 6 MV output ratio analysis for various diode detector and accelerator combinations

Area of Science:

• Medical Physics
• Radiation Oncology
• Dosimetry

Background:

• Accurate dosimetry is critical for stereotactic radiotherapy.
• Small radiation fields present unique challenges for detector response and measurement consistency.

Purpose of the Study:

• To measure detector-specific output ratios (OR(det)) in 6MV small fields.
• To evaluate measurement precision and experimental uncertainty using various diode detectors.
• To compare detector performance on Varian iX and Elekta Synergy linear accelerators.

Main Methods:

• Output ratios (OR(det)) were measured using IBA stereotactic field diodes (SFD) and PTW field diodes (T60008, T60012, T60016, T60017).
• Measurements were performed at depths of 1.5, 5.0, and 10.0 cm for field sizes ranging from 0.5 cm to 3.0 cm.
• Coefficient of variation (CV) was calculated to assess measurement precision; jaw position accuracy was also investigated.

Main Results:

• Measured OR(det) varied between detectors for field sizes smaller than 3.0 cm.
• Standard uncertainty in OR(det) was approximately ±1.25% for the smallest field sizes (0.5 cm).
• CV increased to 0.10% and 0.15% on Varian and Elekta linacs, respectively, at 0.5 cm field size.

Conclusions:

• Diode detectors provide reproducible measurements of small field output ratios within ±1.25% standard uncertainty.
• Measurement precision, characterized by CV, ranged from 0.10% to 0.15% for the studied small fields.
• Findings are crucial for accurate dosimetry in small field radiotherapy techniques.