Document Type : Research Paper
Department of Basic Science- Biophysics Unit, College of Medicine, Hawler Medical University (HMU), KR, Iraq
Department of Basic Science- Biophysics Unit, College of Medicine, Hawler Medical University (HMU), KR, Iraq.
Background and objective: Three-dimensional conformal radiotherapy (3DCRT) is an advanced radiation treatment technique that shapes the radiation beams to match the shape of the tumor and it is used to treat brain tumors while avoiding radiation to the healthy tissue surrounding brain tumor. the purpose of this study is to evaluate the dosimetric data (the planning target volume (PTV), dose homogeneity, dose of organs at risk (OARs)) among the patients with a brain tumor by using three-dimensional conformal radiotherapy (3D-CRT).
Methods: In eight patients with brain tumors being treated by 3DCRT, the target, lenses of eyes, optic nerves, brain stem, and open chiasm were contoured. Two opposed lateral fields were used. The prescribed photon beam dose was depending on the type of tumor, in general for all cases is divided into 20 fractions using 6 MV photons.
Results: The comparison of 3D-CRT outcomes for all patients showed that the most common location of a tumor in the brain was in GBM in temporal and frontal parts of the brain and consist about 25% to total types of tumor in the brain for patients in this study, more than 62.5% of patients were treated with doses more than 4400 cGy the homogeneity index was better for patient No. 1 than other patients (0.0694). The mean dose for the Right lens was higher for patient No. 8 than for other patients was (1530 cGy). While in the left lens the mean dose was higher in patient No. 3 than in other patients was (1501 cGy), and the mean dose for both lenses in all plans for all patients was less than ≤10 Gy (the standard tolerance value). The highest mean dose received by the left optic nerve in patients number 2 was (3339 cGy), and the more mean dose received by the right optic nerve in patients number 2 was (3645 cGy), but in both two sides of the optic nerve the mean doses them less than ≤ 50 Gy the standard tolerance value. The mean dose received by Brain stem for all patients was less than ≤ 50 Gy tolerance dose. The mean dose received by Open Chiasm for all patients was less than ≤ 54 Gy tolerance dose
Conclusion: This study showed that 3DCRT spared the volume of the healthy tissue surrounding the brain tumor to be irradiated to achieve the most accurate treatment delivery to best planning target volume. the application of 3D-CRT was successful in justification of radiation dose to lower than tolerance dose in all evaluated brain tissues.