Setup errors and CTV to PTV margin for upper abdominal cancer with intensity modulated radiotherapy technique using electronic portal imaging device in Sakon Nakhon Hospital

Abstract

Introduction: The systematic and random setup errors for patients with upper abdominal cancer are specific to each hospital. Objective: This study aimed to determine the systematic error, random error, and CTV to PTV margin for patient positioning in upper abdominal cancer with intensity-modulated radiotherapy (IMRT) using the electronic portal imaging device (EPID). Materials and Methods: Patient information and setup errors of 32 patients undergoing radiotherapy were collected. The data on setup errors in three directions (longitudinal, lateral, and vertical) were retrospectively collected from the Mosiaq Platform. Subsequently, individual and population systematic and random errors were calculated. The CTV to PTV margins were then determined using the Van Herk equation. Finally, correlations between setup error and BMI, age, and PTV volume were analyzed. Results: The results showed that the setup errors in the longitudinal, lateral, and vertical directions were 2.59±1.44, 2.17±0.95, and 1.66±0.59 mm, respectively. The population systematic errors in the longitudinal, lateral, and vertical directions were 1.44, 0.95, and 0.59 mm, respectively. The population random errors in the longitudinal, lateral, and vertical directions were 2.59, 2.17, and 1.66 mm, respectively. The determined CTV to PTV margins in the longitudinal, lateral, and vertical directions were 5.42, 3.89, and 2.62 mm, respectively. There was no correlation between setup error and BMI, age, or PTV volume, with p-values > 0.05. Conclusion: The CTV to PTV margins were less than 5 mm in all directions except the longitudinal direction. This finding may be useful for reviewing the PTV margin for Sakon Nakhon hospital.