A comparison of Monte Carlo simulation with experimental dosimetric techniques for a 6 MV stereotactic radiotherapy unit

Abstract

Purpose: To compare Monte Carlo simulation with conventional dosimetry techniques for stereotactic radiotherapy (SRT), since accurate dosimetry of narrow photon beams is very complicated and has often been questioned, mainly due to the lack of lateral electronic equilibrium and uncertainty in beam energy in terms of steep dose gradients. Materials and methods: In this work a Monte Carlo (MC, EGS4) simulation for dosimerty study was performed for the 6MV home made SRT unit of the University Hospital of Patras (Hellas). The results were compared with conventional small field dosimetry techniques such as ionization chamber, TLD's, and films (conventional and radiochromic). Hence, a comparison of many of the dosimetric techniques currently being used in small field dosimetry was attempted. Results: It was shown that all techniques are in reasonable agreement (within ± 2%) and that Monte Carlo can be used as a reliable reference for the dosimetry of the SRT beams, especially where lateral electronic equilibrium does not exist, as long as accurate simulation can be achieved. Conclusion: This study is only limited by the insurance of accurate simulation of the linear accelerator, which can be a difficult task since it is limited by the availability of the manufacturer's designs and the availability of computers and computer time for adequate runs, but it could become a useful tool for Monte Carlo simulations, as it contains detailed analysis of the run parameters and component modules selection. © 2004 Zerbinis Medical Publications.