A comparative study of photon beam percentage depth dose of a recently installed varian vitalbeam linear accelerator at TMSS cancer center, Bangladesh

Abstract

The commissioning procedure and maintenance of safety precautions before the beam is hit the affected cells are the key factors for the success of external beam radiotherapy. The percentage depth dose (PDD), which must be measured before a linear accelerator (LINAC) is used clinically, is one of the crucial factors during commissioning. Measurements for PDDs were carried out in this study atTMSS Cancer Center, Bogura, Bangladesh, using a linear accelerator (Varian VitalBeam SN: 5199, machine completely new in Bangladesh) with 6MV,10MV and 15MV photon energies for a set of 10 field sizes keeping the same conditions such as pressure, temperature, incremental step, direction, geometry, chamber voltage and polarity. Two ionization chambers CC13 (SN:18616) and CC04 (SN:18635) were used to measure PDDs for the linear accelerator utilizing 3D water phantom (SMARTSCAN)and IBA myQA Accept software. Using a TPS beam analysis tool, PDDs were calculated (Eclipse, Version: 16.1, Algorithm: AAA and PO). The measured PDD curves for 6MV, 10MV and15MV photon beams with above mentioned field sizes and at SSD 100 cm were compared with the PDD curves of the British Journal of Radiology-25. The maximum depth doses (dmax) for reference field size 10 × 10 cm2are 15.0 mm, 24.0 mm and 29.0 mm and the PDDs at 10 cm depth (D10) are 66.80%, 73.55% and77.14% for6 MV, 10 MV and 15 MV photon energies respectively. The results for the maximum depth doses (dmax) and the PDDs at 10 cm depth (D10) are determined to be within the limit. The measured PDD curves and the PDD curves of BJR-25 exhibit good agreement.