Determination of Beam Quality and Dosimetric Verification of 6mv and 10mv Photon Beam of an Elekta Synergy Platform Linear Accelerator

Abstract

Beam quality verification is a fundamental aspect of radiotherapy commissioning and quality assurance, ensuring that photon beams from medical linear accelerators correspond to their nominal energies and comply with international dosimetry protocols. For megavoltage beams, indices such as percentage depth dose (PDD) at 10cm, tissue phantom ratio at depths of 10cm and 20cm (TPR_20,10 ), and quality conversion factor kQ_, Q₀, are used to characterize beam quality. Accurate measurement of these parameters is essential to achieving consistent dose delivery and maintaining patient safety. This study aims to determine and verify the beam quality of 6MV and 10MV photon beams from Elekta Synergy linear accelerator for treatment plan quality assurance. Beam quality measurements were performed in water in a 3D water phantom at 100cm source-to-chamber distance (SCD) of 100cm and a field size of 10cm x 10cm at the chamber plane. A calibrated cylindrical Farmer type ionization chamber (30010) connected to a calibrated PTW UNIDOS electrometer (60731) was used to obtain depth-dose readings, the kQ_, Q₀  value were then evaluated using the IAEA TRS 398 TPR_20,10 method. Measurements were taken at depths of 20cm and 10cm beneath the water surface, and at three different polarities of +300, +150, and -300 polarities on the electrometer. For the 6MV photon beam, the kQ_, Q₀  value was 0.993, TPR_20,10  was 0.67, PDD(10) was 66.38% and the absorbed dose to water at Zmax was 0.9941cGy/MU and for the 10MV photon energy, the kQ_, Q₀  value was 0.983, TPR_20,10  was 0.73, the PDD was 74.8% and the absorbed dose to water at Zmax was 1.004cGy/MU, these values are consistent with international reference standards. Beam quality verification confirmed that the Elekta Synergy linear accelerator delivers accurate 6MV and 10MV photon beams in compliance with TG-51 and IAEA TRS-398. Routine quality checks remain essential to ensure precise dose delivery and optimize radiotherapy outcomes.