Hippocampal Sparing in Whole-Brain Radiotherapy: A Comparative Study of Helical Tomotherapy and Volumetric Modulated Arc Therapy

Palanivelu D; D. Khanna; P. Mohandass; Vadiraja BM; Sanjeev Sharma; Sindhu P Kavalakkat; Venugopal S; Anto Vaz

doi:10.31557/APJCB.2026.11.2.535-545

Authors

Palanivelu D Department of Physical Sciences, School of Sciences, Arts and Media, Karunya Institute of Technology and Sciences, Coimbatore, Tamil Nadu, India. Department of Radiotherapy, Manipal Hospital, Old Airport Road, Bengaluru, Karnataka, India.
D. Khanna Department of Physical Sciences, School of Sciences, Arts and Media, Karunya Institute of Technology and Sciences, Coimbatore, Tamil Nadu, India.
P. Mohandass Department of Radiation Oncology, Fortis Cancer Institute, Fortis Hospital, Mohali, Punjab, India.
Vadiraja BM Department of Radiotherapy, Manipal Hospital, Old Airport Road, Bengaluru, Karnataka, India.
Sanjeev Sharma Department of Radiotherapy, Manipal Hospital, Old Airport Road, Bengaluru, Karnataka, India.
Sindhu P Kavalakkat Department of Radiotherapy, Manipal Hospital, Old Airport Road, Bengaluru, Karnataka, India.
Venugopal S Department of Physical Sciences, School of Sciences, Arts and Media, Karunya Institute of Technology and Sciences, Coimbatore, Tamil Nadu, India. Department of Radiation Oncology, Yashoda Super Specialty Hospital and Cancer Institute, Ghaziabad, India.
Anto Vaz Department of Physical Sciences, School of Sciences, Arts and Media, Karunya Institute of Technology and Sciences, Coimbatore, Tamil Nadu, India. Department of Radiation Oncology, Kovai Medical Center and Hospital, Coimbatore, India.

DOI:

https://doi.org/10.31557/APJCB.2026.11.2.535-545

Keywords:

Hippocampus, Helical Tomotherapy, VMAT

Abstract

Background: Study to perform a dosimetric analysis and comparison of hippocampal (HC) sparing in whole-brain radiotherapy (WBRT) using volumetric modulated arc therapy (VMAT) and helical tomotherapy (HT).

Material and Methods: Twenty patients who had previously undergone WBRT with a prescribed dose of 30 Gy in 10 fractions, incorporating HC sparing, were selected for this study. The HC was contoured, and HC avoidance (HCA) regions were defined using a 5.0 mm volumetric expansion around the HC. Treatment plans were created using Accuray Precision treatment planning for HT and Pinnacle treatment planning for Elekta Infinity with an Agility head using VMAT. For comparison, parameters including V100, V98, and V95 (volumes receiving 100%, 98%, and 95% of the prescribed dose, respectively), maximum dose (Dmax), mean dose (Dmean), conformity index (CI), and homogeneity index (HI) for the planning target volume (PTV) and PTV-HC were evaluated. Additionally, doses received by organs at risk (OAR), including the HC, eyes, and lenses, were analysed.

Results: No significant differences in target coverage were observed between VMAT and HT for PTV and PTV-HC. V100 was comparable for both techniques (85% for PTV and 89% for PTV-HC), while V98 and V95 were slightly lower with VMAT for both targets. Dmax and Dmean values for PTV and PTV-HC were similar, and CI and HI were also were comparable between the two techniques. VMAT provided improved sparing of OARs. The HC Dmax was reduced by 10.0% on the right and 11.7% on the left, while Dmean was reduced
by 8.1% and 6.9%, respectively, compared to HT. VMAT significantly reduced eye doses, with Dmax reductions of 27.0% for the right eye and 22.4% for the left eye, and Dmean reductions of 15.5% and 18.0%, respectively. Lens Dmax was also lower with VMAT (right: 21.3%; left: 20.2%). VMAT significantly reduced beam-on time, with HT requiring approximately 64% longer treatment time.

Conclusion: Target coverage was similar in both HT and VMAT plans, while VMAT achieved lower Dmax to the eyes and HC and reducing treatment time. Owing to improved OAR sparing and treatment efficiency, VMAT may be preferred for HCA-WBRT.