title: Comparison of the extent of hippocampal sparing according to the tilt of a patient's head during WBRT using linear accelerator-based IMRT and VMAT.
abstract: In this paper, we report the results of our investigation into whole brain radiotherapy (WBRT) using linear accelerator-based intensity-modulated radiation therapy (IMRT) and volumetric-modulated arc therapy (VMAT) in lung cancer patients with a high risk of metastasis to the brain. Specifically, we assessed the absorbed dose and the rate of adverse effects for several organs at risk (OAR), including the hippocampus, according to the tilt of a patient's head. We arbitrarily selected five cases where measurements were made with the patients' heads tilted forward and five cases without such tilt. We set the entire brain as the planning target volume (PTV), and the hippocampi, the lenses, the eyes, and the cochleae as the main OAR, and formulated new plans for IMRT (coplanar, non-coplanar) and VMAT (coplanar, non-coplanar). Using the dose-volume histogram (DVH), we calculated and compared the effective uniform dose (EUD), normal tissue complication probability (NTCP) of the OAR and the mean and the maximum doses of hippocampus. As a result, if the patient tilted the head forward when receiving the Linac-based treatment, for the same treatment effect in the PTV, we confirmed that a lower dose entered the OAR, such as the hippocampus, eye, lens, and cochlea. Moreover, the damage to the hippocampus was expected to be the least when receiving coplanar VMAT with the head tilted forward. Accordingly, if patients tilt their heads forward when undergoing Linac-based WBRT, we anticipate that a smaller dose would be transmitted to the OAR, resulting in better quality of life following treatment.
authors.affiliation: Department of Bio-convergence Engineering, Korea University, Seoul, Republic of Korea.
authors.forename: Sun Young
authors.initials: SY
authors.lastname: Moon
authors.affiliation: Department of Bio-convergence Engineering, Korea University, Seoul, Republic of Korea.
authors.forename: Myonggeun
authors.initials: M
authors.lastname: Yoon
authors.affiliation: Department of Radiation Oncology, Kyung Hee University Hospital at Gangdong, Seoul, Republic of Korea.
authors.forename: Mijoo
authors.initials: M
authors.lastname: Chung
authors.affiliation: Department of Radiation Oncology, Kyung Hee University Hospital at Gangdong, Seoul, Republic of Korea. Electronic address: wkchung@khnmc.or.kr.
authors.forename: Weon Kuu
authors.initials: WK
authors.lastname: Chung
authors.affiliation: Department of Radiation Oncology, Kyung Hee University Hospital at Gangdong, Seoul, Republic of Korea. Electronic address: joocheck@gmail.com.
authors.forename: Dong Wook
authors.initials: DW
authors.lastname: Kim
mesh_terms: D001921:Brain / Q000528:radiation effects; D001932:Brain Neoplasms / Q000532:radiotherapy* / Q000556:secondary; D006257:Head / Q000502:physiology*; D006624:Hippocampus / Q000000981:diagnostic imaging* / Q000528:radiation effects; D006801:Humans; D009362:Neoplasm Metastasis / Q000532:radiotherapy; D058958:Organs at Risk / Q000528:radiation effects; D010315:Particle Accelerators; D056888:Patient Positioning; D011877:Radionuclide Imaging; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods*; D014057:Tomography, X-Ray Computed
keywords: Head tilting; Hippocampus; Intensity-modulated radiation therapy; Radiation therapy; Volumetric-modulated arc therapy; Whole brain radiotherapy