Defense Date
2026
Document Type
Thesis
Degree Name
Master of Science
Department
Medical Physics
First Advisor
William Song
Abstract
Beam commissioning is a critical component of linear accelerator (LINAC) implementation, requiring accurate measurement of percent depth dose (PDD), beam profiles, and output factors across a wide range of field sizes. Conventional commissioning workflows often require multiple detectors and can be time-intensive, particularly for small-field dosimetry where measurement accuracy is highly sensitive to detector characteristics. This study evaluated the performance of a plastic scintillation detector (BP-PSD) for full water tank commissioning and its potential to improve efficiency while maintaining dosimetric accuracy.
Beam data were acquired for field sizes ranging from 1 × 1 cm² to 40 × 40 cm² using the BP-PSD and compared against established clinical detectors, including the microDiamond, EDGE diode, PinPoint ion chamber, and SNC125c detector. Measurements included PDD, beam profiles, penumbra, field size accuracy, and output factors under both standard and small-field conditions in accordance with TRS-483 recommendations.
The BP-PSD demonstrated strong agreement with reference detectors across all measurement types. Output factors agreed within approximately 1.25% for small MLC-defined fields and within 3% for jaw-defined fields. Beam profile and penumbra measurements showed submillimeter agreement, and field size accuracy based on full width at half maximum (FWHM) was typically within ±1 mm. PDD measurements showed consistent agreement beyond the buildup region, with minor differences observed for the smallest fields and at greater depths.
The BP-PSD also improved commissioning efficiency. Profile measurements at 5 mm/s and 15 mm/s showed negligible differences, supporting faster scan speeds without loss of accuracy. Automated workflows enabled three complete output factor datasets in approximately 30 minutes compared to 90 minutes using conventional methods, reducing total measurement time by 4,166 seconds (69.4 minutes), or 39%.
These results demonstrate that the BP-PSD provides comparable dosimetric performance while significantly improving commissioning efficiency, supporting its use as a single-detector solution for full LINAC commissioning.
Rights
© The Author
Is Part Of
VCU University Archives
Is Part Of
VCU Theses and Dissertations
Date of Submission
5-3-2026