Hippocampal Sparing in Dose-Painting Radiotherapy in High-Grade Glioma

This study aimed to determine hippocampal absorbed dose in radiotherapy of high-grade brain glioma using dose painting method and to compare it with intensity-modulated radiation therapy (IMRT) and three-dimensional conformal radiotherapy (3D-CRT).
In Milad hospital radiotherapy section in Isfahan, Iran, images from 24 patients with high-grade brain glioma were acquired. All radiotherapy volumes for patients were defined and then, at risk organ was contoured. There were 4 planning target volumes (PTVs) defined for each patient. PTV4 just has been defined for dose painting method and the given dose was increased up to 72 Gy in this method. Finally for each patient, by using treatment planning system characteristics, 3 methods were simulated and the optimal technique was represented.
Findings: The average hippocampus-received dose was 4.772, 4.174, and 5.668 Gy in 3D-CRT, IMRT, and dose painting methods, respectively. Increasing the dose in dose painting method by 1.2% than in IMRT method resulted in 1.357% increasing in hippocampal-absorbed dose; considering the hippocampal tolerance dose, it would not cause serious injury and in return tumors, would be controlled more effectively.
In this study, the importance of multi-parametric magnetic resonance imaging (MRI) in dose painting method was achieved. As by using these images for determining the different parts of tumor, tumor-received dose significantly increased; while the organs around the tumor received no serious damage.