When Do We Need Confirmation CBCT?
Abstract
Purpose
Radiation therapy (RT) aims to deliver a therapeutic dose of radiation to the tumor while minimizing exposure to surrounding normal tissues. However, several sources of geometric error can occur: Inter-fractional errors, Intra-fractional errors, and Systematic errors. Without correction, these errors can lead to underdosing the tumor or overdosing healthy tissue. IGRT substantially mitigates these risks by enabling precise verification and correction before and during treatment. However, imaging choice is essential since we need to consider the imaging dose and time also. Do we still need confirmation CBCT after shift?
Methods
A retrospective study was conducted to collect 1,063 fractionation data points for lung patients, including the shift after CBCT confirmation, kV/kV-pair used before CBCT, treatment site in the lung, PTV Volume, patient sex, patient age, disease T stage, and N stage. In order to deeply analyze the relatively large data, classification applications in Matlab were used. The Shift after CBCT confirmation was used as a response, and the other features were used as predictors. Twenty-five models (including tree, SVM neural network etc.) were trained for the data.
Results
On average, 84.1% accuracy was achieved for all the models. ROC and the precision curve show true position results based on different training models. Anova ranking for predictors were also analyzed. Based on the analysis, the CBCT is necessary and has a high correlation with PTV volume, patient sex (males are easier to shift than females), patient age (older patients are easier to shift), and T/N staging (the higher the staging, the greater the need for CBCT). It seems the right lung is easier to shift than the left lung.
Conclusion
data about CBCT IGRT was analyzed and factors affecting the use of CBCT were found. The finding is value for clinical operation and IGRT choice.