A retrospective dosimetric comparison of volumetric arc therapy (VMAT) and intensity adjustable radiotherapy (IMRT) plans of patients receiving whole brain radiotherapy with hipocampus avoidance

In this study brain metastases 10 with hippocampus-protected whole-brain radiotherapy technique, VMAT and IMRT treatment planning systems and virtual Plansand dosimetric comparison was made. Archival data of 10 patients with brain metastases who were treated in Bursa Uludağ University Faculty of Medicine, Department of Radiation Oncology were obtained retrospectively. In the plans made, a dose of 30 Gy was determined to be given in 10 fractions. Contours of the whole brain, hippocampus, lens, orbit, optic nerve, cochlea, parotid, lacrimal, optic chiasm, pituitary, hypothalamus, mandible, and brain stem were made for virtual plans. PTV was created by subtracting the target brain volume from the whole brain volume by giving a 5 mm margin to the hippocampus. In the plans, attentionwas paid to ensure that the isodose covers 95% of the target volume and that the critical organs receive doses within the specified limits. SPSS program, Mann Whitney U test and Independent Statistical analysis was performed using our study in PTV, hippocampus, lens, orbita, cochlea, parotid, optic nerve, optic chiasm, HI no significant difference was found for lacrimal, mandible, pituitary, hypothalamus, brain stem, CI. The lowest valuesfor HI and MU were obtained in the VMAT planning system. Although the lacrimal, brainstem and mandible doses were found to be lower in the VMAT technique, no statistical significance was found between the two different treatment techniques.