Measuring small field profiles and output factors with a stemless plastic scintillator array.

Area of Science:

• Medical Physics
• Radiation Detection
• Semiconductor Devices

Background:

• Accurate measurement of small radiation fields is crucial for modern radiotherapy techniques.
• Traditional detectors often face challenges in precisely characterizing these small fields.
• Organic photodiodes offer a potential solution for compact and sensitive radiation detection.

Purpose of the Study:

• To fabricate a one-dimensional (1D) stemless plastic scintillation detector (SPSD) array.
• To utilize organic photodiodes within the SPSD array for radiation detection.
• To measure small field profiles and output factors accurately using the fabricated SPSD array.

Main Methods:

• Fabrication of an organic photodiode array using P3HT:PCBM semiconductors on an ITO-coated glass substrate.
• Integration of various scintillator designs (bulk and laser-etched segmented) atop the photodiode array.
• Calibration of the detector array and subsequent measurement of small field profiles (0.5x0.5 to 2x2 cm²) and output factors (0.5x0.5 to 25x25 cm²) using a 6 MV photon beam, with comparisons to film and ion chamber measurements.

Main Results:

• The laser-etched segmented scintillator array demonstrated good agreement with film for small field profiles.
• Output factors measured by the segmented scintillator agreed within 1.2% of ion chamber measurements for field sizes down to 1x1 cm².
• Bulk scintillators showed significant deviations in profile measurements and output factors compared to reference detectors, especially for fields smaller than 5x5 cm².

Conclusions:

• A 1D stemless plastic scintillation detector (SPSD) array was successfully fabricated and demonstrated.
• The etched scintillator design within the SPSD array provided excellent accuracy for small field profile measurements.
• The SPSD array, particularly with the etched scintillator, is a viable tool for precise output factor measurements in small radiation fields.