Sci-Fri PM: Delivery - 07: Cyberknife relative output factor measurements using fiber-coupled luminescence, MOSFETS...

Area of Science:

• Medical Physics
• Radiation Oncology Dosimetry

Background:

• Accurate measurement of relative output factors (ROFs) is crucial for Cyberknife radiosurgery precision.
• Novel dosimetry systems offer potential improvements over existing methods for small field measurements.

Purpose of the Study:

• To evaluate novel Al2O3:C radioluminescence (RL) and 4D dosimetry system (RADPOS) for measuring Cyberknife ROFs.
• To compare these novel systems with mobile MOSFET and radiochromic film detectors across various cone sizes.

Main Methods:

• ROFs were measured using Al2O3:C RL, RADPOS, mobile MOSFET, and GAFCHROMIC® films in a solid water phantom.
• Measurements were conducted at 1.5 cm depth and 78.5 cm SSD for cone sizes ranging from 5 to 60 mm.
• Monte Carlo simulations were used to derive correction factors for RL measurements of small cones (5-10 mm).

Main Results:

• Excellent agreement was observed between RL/RADPOS, MOSFET, and film measurements for cone sizes ≥ 12.5 mm.
• Corrected RL and MOSFET/RADPOS measurements showed strong agreement for small cones (5, 7.5, 10 mm).
• RL and MOSFET/RADPOS systems demonstrated good agreement with radiochromic film data across field sizes.

Conclusions:

• The microMOSFET/RADPOS and optical fiber-coupled RL dosimetry systems are well-suited for Cyberknife ROF measurements.
• Appropriate correction factors are essential for accurate dosimetry with these systems, particularly for the smallest cone sizes (5-10 mm).