Dosimetric Comparison of IMRT with 3D-CRT Regarding Their Contribution to the Treatment Plan Optimization Using Rando Phantom with a Realistic Lung Cancer Radiotherapy Treatment Planning

Introduction: This study compared a threedimensional conformal radiation therapy (3D-CRT) with a recently implemented intensity modulation radiation therapy (IMRT) technique performed in the irradiation of lung cancer. The objective of this study is to demonstrate the dosimetric advantages of IMRT in target coverage, dose homogeneity, and reducing toxicity. Material and Methods: Depth point doses were compared as calculated by the Varian Eclipse treatment planning system (TPS) on virtual created patient and experimentally measured by thermoluminescence (TL) dosimetry. For treatment planning the same lesion of the real case with different volumes and structures contouring details were created on Rando anthropomorphic phantom computed tomography (CT) data. Dose measurement was performed by calibrated thermoluminescent detectors. Results: The difference between experimental TL measured doses and calculated doses in both techniques show mean values of ~3% (IMRT) and ~1% (3D-CRT) for high dose ( 0.55Gy) and ~7% IMRT and 6.5% (3D-CRT) for low dose ( 0.55Gy). All IMRT optimized plans improved the heart (-28.3%), the spinal cord (-25.3%), and the left lung (-41.55%) sparing significantly, compared to the 3D-CRT plans. The optimized dosevolume histograms, the dose covering indices, and the dose profile across heterogeneity interfaces showed a significant improvement in dose conformity by IMRT. Conclusion: These findings demonstrate well that TL dosimetry when combined with suitable point dose measurement procedures can efficiently be used as an external and independent dose audit for the comparison between 3D-CRT and IMRT. IMRT with its dosevolume optimization algorithm can achieve a treatment plan quality in lung cancer radiotherapy unachievable by 3D-CRT.