Dose calculations accuracy of TiGRT treatment planning system for small IMRT beamlets in heterogeneous lung phantom

Background : Accurate dose calculaons in small beamlets and lung material have been a great challenge for most of treatment planning systems (TPS). In the current study, the dose calculaon accuracy of TiGRT TPS was evaluated for small beamlets in water and lung phantom by comparison to Monte Carlo (MC) calculaons. Materials and Methods : The head of Siemens Oncorimpression linac was simulated for 6 and 18 MV photon beams using MCNPX MC Code. The model was validated using measured percentage depth dose and beam profiles. Then, the validated model used for dose calculaons for small beamlets in water as well as lung phantoms. For treatment planning purposes, the lung phantom was scanned and imported into the TPS, and then the percentage depth dose values were obtained from plans for small fields of 1×1, 2×2, 3×3 and 4×4 cm 2 in water and lung phantom. Results: For small fields in water phantom, there was a good agreement between TPS and MC for 2×2 to 4×4 cm