Dosimetric Comparison of Stereotactic Radiotherapy Treatment Planning between Three Dimensional Conformal Radiation Therapy and Tomotherapy for Brain tumor

Abstract

Backgrounds: Stereotactic Radiotherapy (SRT) for brain tumor must have highly accuracy of radiation to get the maximum radiation dose to the lesions while organs at risk (OARs) receives the minimum radiation dose. The research found that the Helical Tomotherapy (HT) is used in SRT for brain tumor. The study was done retrospectively to plan and compare SRT with HT. Objective: To plan SRT with HT for brain tumor and compare dosemetric parameters of planning target volume (PTV) and OARs with three-dimensional radiotherapy (3DCRT) using a linac with micro-multileaf collimator. Materials and Methods: This is a retrospective study for SRT treatment planning comparison between HT and 3DCRT using a linac with micro-multileaf collimator. The CT images of 17 brain tumor cases who received SRT were used to generate HT planning. The comparison dosemetric parameters of PTV were conformity index (CI) and homogeneity index (HI). The OARs were brainstem, optic chiasm, optic nerves and eyes. The comparison dosemetrics parameters of OARs maximum dose (Dmax), minimum dose (Dmin) and mean dose (Dmean). The whole brain dose parameters were D50 and integral dose. Result: The result showed the CI of PTV were 1.15, 1.51 and the HI of PTV were 6.51%, 9.64% for HT and 3-DCRT, respectively. There were no statistically significant differences. For OARs, Dmax, Dmin and Dmean of brain stem, optic nerves and eyes in HT plan were higher than 3-DCRT plan. There were statistically significant differences of Dmax, Dmean at the eyes and Dmin at the optic nerves. However, Dmax and Dmin of the optic chiasm of HT were less than 3-DCRT but there was no statistically significant difference. For the whole brain, D50 and integral dose of HT plan were 0.4 and 3.32 Gy, respectively. Conclusion: The comparison of SRT treatment planning for Brain tumor, the HT plan showed better CI and HI of PTV than the 3-DCRT plan. The HT was an appropriate SRT technique for Brain tumor. Although the HT had low dose spread out to surrounding normal tissues, the normal tissue tolerance did not exceed.