Main Session
Sep
28
PQA 03 - Digital Health Innovation and Informatics, Patient Safety & Quality, and Radiation and Cancer Biology
2489 - Reference-Free Beam Commissioning Using Pulse Normalization: A Comparative Evaluation in C-Arm and Ring-Gantry Linear Accelerator
Presenter(s)
Ananda Jadhav, M.Sc.Phy, Dip.RP - Sir .H. N. Reliance Foundation Hospital and Research Center, Mumbai, Not Applicable
A. R. Jadhav Sr1, O. C. Awate2, S. K. Rasal2, and P. Dandekar3; 1Sir .H. N. Reliance Foundation Hospital and Research Center, Mumbai, India, 2SIR H. N. RELIANCE FOUNDATION HOSPITAL AND RESEARCH CENTRE, Mumbai, India, 3Sir H. N. Reliance Foundation Hospital and Research centre, Mumbai, India
Purpose/Objective(s):
Beam data acquisition using a reference chamber in scanning water phantoms is standard practice during linear accelerator commissioning; however, it introduces setup complexity, signal noise, and positioning challenges—particularly in ring-gantry systems lacking optical field lights. This study evaluates whether pulse normalization technology can provide dosimetric equivalence to conventional reference chamber–based acquisition while improving workflow efficiency.Materials/Methods:
Beam profiles and percentage depth dose (PDD) measurements were acquired using the Sun Nuclear SunSCAN 3D Radiation Field Analyzer on a Varian TrueBeam STx (6, 10, 15 MV, and 6X-FFF) and a Varian Ethos (6FFF). Field sizes ranged from 5×5 cm² to 30×30 cm² (TrueBeam) and 28×28 cm² (Ethos). Two acquisition techniques were compared: (1) conventional scanning using an edge-positioned reference ionization chamber and (2) pulse normalization without a physical reference detector. Gamma analysis was performed using 1% dose difference with 1 mm and 0.5 mm distance-to-agreement (DTA) criteria.Results:
For flattened beams on the TrueBeam STx, 100% gamma agreement was observed for both profiles and PDDs under 1 mm/1% and 0.5 mm/1% criteria across all field sizes and depths. For the Ethos 6FFF beam, profile passing rates exceeded 98.6% even for the largest 28×28 cm² field under the strictest 0.5 mm/1% criteria. PDD comparisons demonstrated 100% agreement for all evaluated conditions. Minor variations in large unflattened fields were attributed to steep dose gradients rather than normalization error.Conclusion:
Pulse normalization achieved dosimetric equivalence to conventional reference chamber–based acquisition across both C-arm and ring-gantry platforms. Eliminating the reference chamber reduces setup time, collision risk, and positioning uncertainty, offering a practical advantage for ring-gantry systems such as Ethos. This technique streamlines commissioning workflow without compromising measurement accuracy.