Dosimetric Study Of Single Brain Metastases Intensity Modulated Radiotherapy And Stereotactic Radiotherapy In The Hippocampus

Objective Through the analysis of single brain metastasis carcinoma intensity-modulated radiation therapy（IMRT）and stereotactic radiotherapy（SBRT）dose parameters,under the above two different radiation technology of hippocampal dosimetry difference,to predicting and reducing the occurrence of the nerve in patients with cognitive dysfunction,thus prolonging survival time and improve the patients quality of life,provide theoretical basis for clinical selection of different radiotherapy.Methods A retrospective study was conducted on 100 patients with brain metastases who received the first cerebral radiotherapy in the Department of Radiotherapy of Dalian Central Hospital Affiliated to Dalian Medical University from 2013 to 2021.Bilateral hippocampus was taken as the research object in this study.For the cases that underwent CT simulation localization in our department,the target area was delineated again on the doctor’s workstation.The gross tumor target area（GTV）was defined as the clinical target area（CTV）,and the planned target area（PTV）was defined as the clinical target area（CTV）and the planned target area（PTV）was defined as the clinical target area（CTV）with GTV radiography of 5mm and CTV radiography of 3mm.The outline of organs at risk（hippocampus,eye,crystal,optic nerve,optic chiasma,brainstem,etc.）was performed by the same physicist on the Raystation planning system for each case.The prescribed dose of modulated intensity segmentation radiotherapy（IMRT）and stereotactic radiotherapy（SBRT）is 50Gy/10f.The parameters of the two planned DVH plots are analyzed by comparing the parameters of the two planned DVH plots.Including maximum dose（Dmax）,minimum dose（Dmin）,average dose（Dmean）,D30-D70（Dx represents the dose of X%volume）.SPSS statistical software is used for data processing and analysis.Shapiro-Wilk method is used to test whether the measurement data are in line with the normal distribution.Variables in line with the normal distribution are described by mean and standard deviation（（?）±s）,while those in line with the skew distribution are described by median and quant,and T test and Mann-Witney Urank sun test are used respectively.The differences of hippocampal radiation dose between IMRT and SBRT are compared.Results A total of 100 patients met the inclusion criteria,and the two different plans can meet the clinical prescription dose and limit the organs at risk in the normal range.The parameters of the hippocampal dose volume histogram（DVH）of the three plans are analyzed and compared,and the data are processed by SPSS statistical software analysis of variance.（1）Stereotactic radiotherapy（SBRT）plan in the hippocampal illuminated the maximum dose(D_max),minimum dose(D_min),average dose(D_mean),30%volume dose(D₃₀),40%volume dose(D₄₀)and 50%volume dose(D₅₀)is less than the intensity-modulated radiation therapy（IMRT）,two groups of comparative differences are statistically significant（P<0.05）.Stereotactic radiotherapy（SBRT）is still lower than intensity-modulated radiotherapy（IMRT）in the volume dose(D₆₀)and 70%volume dose(D₇₀),but there is no statistically significant difference between the two plans（P>0.05）.（2）Comparison of dosimetric differences in the hippocampus between two treatment plans when metastases were located 10mm or less from the hippocampus.Stereotactic radiotherapy（SBRT）plan in the hippocampal illuminated the maximum dose(D_max),the average dose(D_mean),the minimum dose(D_min),30%volume dose(D₃₀),40%volume dose(D₄₀),50%volume dose(D₅₀),60%volume dose(D₆₀)and 70%volume dose(D₇₀)are greater than intensity-modulated radiation therapy（IMRT）,and two sets of plans are statistically significant（P<0.05）.（3）When the distance metastases in the hippocampus is more than 10 mm and less than or equal to 15mm and greater than 15 mm,stereotactic radiotherapy（SBRT）plan in the hippocampal illuminated the maximum dose(D_max),the average dose(D_mean),the minimum dose(D_min),30%volume dose(D₃₀),40%volume dose(D₄₀),50%volume dose(D₅₀),60%volume dose(D₆₀)and 70%volume dose(D₇₀)are less than intensity-modulated radiation therapy（IMRT）,and there is statistical difference between the two groups（P<0.05）.（4）The dose of stereotactic radiotherapy（SBRT）to the hippocampus is lower than that of modulated power fractionation radiotherapy（IMRT）with tumor size smaller than or equal to 30mm or larger,but there was no statistically significant difference between the two plans（P>0.05）.Conclusion In radiotherapy for brain metastasis,the DVH graphs of the two plans at the same prescription dose shows that the dose of each parameter of the stereotactic radiotherapy（SBRT）plan to the hippocampus is all lower than that of modulated power fractionation radiotherapy（IMRT）.When the metastatic tumor is close to the hippocampus,the dose of each parameter of stereotactic radiotherapy（SBRT）to the hippocampus is higher than that of modulated intensity fractionation radiotherapy（IMRT）.When the metastatic tumor is far from the hippocampus,the dose of each parameter of stereotactic radiotherapy（SBRT）to the hippocampus is lower than that of modulated intensity fractionation radiotherapy（IMRT）.Regardless of the size of the metastases,the dose of stereotactic radiotherapy（SBRT）to the hippocampus is lower than that of modulated power fractionation radiotherapy（IMRT）,but there is no significant difference between the two plan.