(Sunday, 7/12/2020) [Eastern Time (GMT-4)]
Room: AAPM ePoster Library
Purpose: propose a novel homogeneity index based on the partial proportion of DVHs with considering the clod and hot regions inside target, and study the accuracy when evaluating the uniformity of dose distribution.
Methods: novel HI include three parameters, global homogeneity index(HIG), cold index(HIC) and hot index(HIH), as shown in the equation(1)~(4). The HIC and HIH are used to quantitative analyze the effect of cold and hot areas on homogeneity of dose distribution. Ideally, HIG, HIC and HIH are more close to 0 that indicate the better dose distribution inside target. In this study, we selected five patients with localized prostate cancer staged T1-T2,meanwhile the two series of SBRT plans were designed in CyberKnife(CK) and EDGE systems. The conventional HI and novel HIG were calculated and analyzed based on DVHs. And the correlation among HIg and Dmean, D2%, D5%, Dmin were also studied.
Results: different type of HIs for CK and EDGE plans were compared respectively. Our result showed that the EDGE plans had the lower HIH and HIg value that indicate the better uniformity of dose distribution inside target. For the HIc, there were no difference for CK and EDGE plans. Compared with the four conventional HI, it was observed that CK plans provided the better homogeneity, with no accordance with the results of HIg. And there are a positive correlation among HIg with Dmean, D2%, D5%.
Conclusion: novel HIG based on the partial proportion of DVHs can evaluate the dose uniformity effectively with considering the effect of cold and hot area inside target. And the new HI can also provide a more accurate and reliable tool to measure the dose homogeneity than the conventional methods.
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