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The Value of Equivalent Uniform Dose (EUD) of the Lung in the Prediction of Radiation Pneumonia Under the Volumetric Modulation Arc Radiotherapy (VMAT) Technique

x Li

x Li1*, c wang2 , j Gu3 , Q Deng4 , S Ma5 , T Niu6 , (1) Hangzhou First Peoples Hospital, Hangzhou, ZheJiang,(2) Hang Zhou Tumor Hospital, Hangzhou, ZheJiang, (3) Hangzhou Tumor Hospital, Hangzhou, ZheJiang, (4) Hangzhou First People Hospital, Hangzhou, ZheJiang, (5) Hangzhou First People Hospital, Hangzhou, ZheJiang, (6) Zhe Jiang University, Hang Zhou, Zhe Jiang


SU-I-GPD-T-246 (Sunday, July 30, 2017) 3:00 PM - 6:00 PM Room: Exhibit Hall

Purpose: The effectiveness assessment of LEUD based prediction model of Radiation Pneumonitis (RP) in Volumetric-Modulated Arc Therapy (VMAT) and search for the optimal value α.

Methods: 65 patients who underwent VMAT are separated into two groups depends on whether or not they have radiation pneumonitis. Patients including their dose–volume histogram (DVH) data is analyzed by self-compiled numerical analysis program. LEUD values of the two groups of patients are calculated when α is in the range of -50 to 50. Meanwhile, the optimal α value is investigated at which the relative difference of LEUD values between two groups is maximal.

Results: The maximum relative difference of LEUD between group of radiation pneumonitis (GRP) and group of non-radiation pneumonitis (G-NRP) was obtained at α=0.3 where LEUD (GRP) =627.94cGy, LEUD (G-NRP) =510.23cGy (p=0.001), and this relative difference of LEUD reaches 23.07%. The relative difference of LEUD (RDLEUD) is slowly decreasing when α is between -50 and -5, and sharp increasing when α is in the range of -5 to 0. The maximal RDLEUD was obtained at α=0.3. After a rapid decrease of RDLEUD in the interval from 0.5 to 4, the decreasing speed of RDLEUD tends to slow down until the end of the study (α=50). The correlation analysis of the traditional physical dose-volume thresholds also shows that there is a strong correlation between LEUD and each factor including V5,V10,V20 and mean lung dose (MLD) at α=0.3(CF=0.83、CF=0.77、CF=0.79、CF=0.84).

Conclusion: For the patients who have received VMAT for pulmonary radiation, LEUD (α=0.3) is able to distinguish between the group whose patients have suffered from radiation pneumonitis and the other group whose patients have not. And we proposed to limit the LEUD to less than 510cGy. The combination of LEUD and conventional physical dose shows a clinical predictive value for radiation pneumonitis induced by non-uniform radiation.

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