Detectors assessment for stereotactic radiosurgery with cones

Area of Science:

• Medical Physics
• Radiation Oncology
• Detector Physics

Background:

• Stereotactic radiosurgery (SRS) requires precise dose delivery.
• Accurate characterization of small radiation fields from cones is crucial for patient safety.
• Monte Carlo simulations serve as a benchmark for detector performance evaluation.

Purpose of the Study:

• To evaluate the performance of eight different detectors for output factor (OF), percent depth dose (PDD), and beam profiles.
• To compare detector accuracy in a 6-MV Clinac SRS mode for cone irradiation (30-4 mm diameters).
• To identify the most suitable detectors for stereotactic cone dosimetry.

Main Methods:

• Monte Carlo simulations were used as the reference standard.
• Eight detectors were tested: pinpoint and pinpoint 3D ionization chambers, SRS, P, E, and Edge diodes, MicroDiamond, and EBT3 radiochromic films.
• Measurements were conducted in a 6-MV Clinac SRS mode for various cone sizes.

Main Results:

• EBT3 film showed the highest accuracy for OF and beam profiles, with differences within ±1% and ±0.2 mm, respectively, compared to Monte Carlo.
• Pinpoint chambers and diodes showed significant under/overestimations of OF, especially for smaller cones (<10 mm).
• MicroDiamond offered good OF accuracy across all cone sizes, while all detectors provided acceptable PDD results within 1%.

Conclusions:

• EBT3 film is the most accurate for OF and beam profiles but has practical limitations.
• Pinpoint chambers and diodes require OF correction factors for cones <10 mm due to size and composition issues.
• MicroDiamond is a suitable choice for OF determination across all cone sizes; detector size is critical for off-axis and profile measurements.