Objective: The 3DVH-γ analysis and bio-mathematical model were used to analyze the effect of the dose calculation grid size (DCGS) on the planned dose (PD) for cervical cancer to explore the efficacy and sensitivity of the two methods in detecting dose changes.
Methods：17 patients’ plans for cervical cancer were enrolled（Pinnacle TPS，VMAT）, and the DCGS was changed from 2.0mm to 5.0mm to calculate the planned dose respectively. The dose distribution calculated by DCGS = 2.0mm as the “ reference ” data set (RDS) , the dose distribution calculated by the rest DCGS as the“measurement”data set (MDS), the 3DVH-γ passing rates and the (N)TCPs of the all structures under different DCGS were abtained , and then analyze the influences of DCGS on the γ passing rate and (N)TCPs and the relationship between their changes.
Results: The effect of DCGS on planned dose was obvious. When the γ-standard was 1.0mm, 1.0% and 10.0%, the difference of the results of the DCGS on dose effect could be detected by 3DVH-γ analysis (ps<0.05). With the decline of the standard, 3DVH-γ analysis’ ability to detect this difference was also declining. When the standard was 1.0mm, 3.0% and 10.0%, the p value of >0.05 accounted for the majority. With DCGS=2.0mm being RDS, ∆γ-passing-rate presented the same trend with ∆(N)TCPs of all structures except for the femurs only when the 1.0mm, 1.0% and 10.0% standards were adopted for the 3DVH-γ analysis.
Conclusions: The 3DVH-γ analysis and bio-mathematical model can be used to analyze the effect of DCGS on the planned dose, and the former’s detection ability has a lot to do with the designed standard, and the latter’s capability is related to the parameters and calculated accuracy of the latter.