Abstract
Radiotherapy plays a crucial role in the management of malignant tumors, serving as an essential or adjunct treatment modality for approximately 50% of cancer patients. For optimal outcomes, the prescribed and delivered radiation doses to the planning target volume must align within ± 5%. This study investigates the impact of upgrading the Elekta Precise Linear Accelerator (LINAC) at the Radiotherapy Department of Tripoli University Hospital in Tripoli, Libya, from a standard radiation head (SH) to a multileaf collimator (MLC) head on photon beam characteristics, specifically the beam profile parameters for energies of 6 MV and 15 MV. Utilizing a PTW MP3-M 3D water scanning system, detailed dosimetric measurements— including beam flatness, symmetry, and penumbra—were conducted before and after the upgrade across various field sizes and depths. The results of this study reveal a significant difference in beam profile parameters post-upgrade. The relative differences in beam flatness were 66.30% for the 6 MV beam and 24.64% for the 15 MV beam. Additionally, the highest recorded relative difference in beam penumbra was 31.76% for the 6 MV beam energy and 17.65% for the 15 MV beam energy. Consequently, it is essential and strongly recommended that the collected beam profile data be recommissioned since it is provided to the treatment planning system used to predict dose distribution in cancer patients