Purpose: The aim of this study is to evaluate and compare hippocampal sparing whole-brain radiation therapy treatment planning techniques using volumetric modulated arc therapy and intensity modulated radiation therapy (IMRT)
Methods: 12 patients previously treated with whole brain radiotherapy, re planned with Volumetric Modulated Arc Therapy and Intensity Modulated Arc Therapy; in an effort to spare the hippocampus region. To delineate optic chiasm, optic nerve; magnetic resonance imaging (MRI) and computed tomography (CT) data acquisition and their fusion has been done. The hippocampus avoidance region was created by giving 5 mm margin to the hippocampus. RTOG 0933 recommendations were applied for the beam arrangement purpose and treatment planning. The prescription for treatment was 30 Gy in 10 fractions and the planning PTV was drawn incorporating the while brain including the hippocampus region.
Results: Dose to hippocampus by IMRT (DMLC) and VMAT are 1786.78±12.53 cGy and 1583.07±12.68 cGy respectively. The Coverage to PTV is almost identical for both the modalities 95.02% and 94.89 % by IMRT & VMAT respectively. The other OAR all have similar dose. The homogeneity index obtained for IMRT and VMAT plans are 0.183 and 0.196 respectively for IMRT and VMAT.
Conclusion: Dose to hippocampus was successfully reduced using 2 planning techniques viz. VMAT & IMRT (DMLC) techniques. The results from the planning comparison case study show that either planning technique can be used to achieve treatment planning goal of adequately reducing the mean dose to the hippocampus. However, VMAT plans provided a more homogeneous dose distribution throughout the PTV. The maximum point dose VMAT plans received was lower than that with IMRT plan. It is important to reduce the doses to these structures as much as possible based on ALARA principle
Not Applicable / None Entered.