Dosimetric Study of Craniospinal Irradiation in Children: Intensity Modulated Radiation Therapy vs. Volumetric Modulated Arc Therapy
Keywords:
Craniospinal Irradiation, Pediatrics, Radiation Therapy, Volumetric Modulated Arc Therapy, Intensity Modulated Radiation TherapyAbstract
Background: Long-term craniospinal irradiation (CSI)-related toxicities are the major concerned in pediatric medulloblastoma. To reduce the risk to normal structures, the more conformal radiation therapy is preferred.
Objective: To evaluate and compare the dosimetric parameters of CSI between intensity modulated radiation therapy (IMRT) and volumetric modulated radiation therapy (VMAT) in terms of target coverage and normal tissue sparing in pediatric patients with standard risk medulloblastoma.
Materials and Methods: Ten children with medulloblastoma previously treated with three-dimensional conformal radiation therapy (3D-CRT) CSI were included in this study. All the planning computed tomography (CT) scans were performed in the supine position with a customized thermoplastic mask on a head rest set. CSI was performed with IMRT and VMAT for each child. Both plans were compared.
Results: IMRT achieved better target coverage. However, more than 95% of the volume of the planning target volume (PTV) was covered by 95% of the prescribed dose for both plans. VMAT achieved better dose homogeneity and conformity. Doses to the OARs complied with the institutional protocol except for the doses to the eyes, lens, and thyroid for both IMRT and VMAT. Due to the lack of an institutional protocol for plan optimization at the time of study, the doses to these organs did not get enough concern. No difference in mean dose to non-target tissues was found between IMRT and VMAT (p = 0.101). The mean monitor units (MU) value of VMAT was significantly lower than that of IMRT (p < 0.05).
Conclusions: With the same protocol compliance of target coverage and dose to OARs, VMAT is preferred due to its higher conformity, better dose homogeneity, and use of lower MU.
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