| Abstrakt: |
There are many rectal cancer patients received radiotherapy. This requires the use of image-guided radiotherapy (IGRT) to examine the treatment region for accuracy and precision. The objective of this study is to evaluate setup errors, setup margin and the correlation between setup errors and several clinical factors for rectal cancer patients. The retrospective data of rectal cancer patients who underwent radiotherapy in 2019 were evaluated. OBI or EPID imaging was acquired during the delivery by recording the setup errors in vertical, longitudinal, and lateral dimensions. Then mean and standard deviation for individual, overall systematic errors and overall random errors were calculated. The Van Herk Formula was used to calculate the setup margins. Furthermore, regression analysis was used to analyse the correlation between setup errors and several clinical factors including gender, BMI, the fraction of IGRT, positioning, staging, immobilization device and colostomy. The result showed that systematic errors in vertical, longitudinal, and lateral were 2.3, 2.2 and 2.4 mm, respectively, and the random errors were 2.3, 2.4 and 2.3 mm, respectively. In addition, setup margins in vertical, longitudinal, and lateral were 7.36, 7.18 and 7.61 mm, respectively. There was a significant association between setup errors with BMI, the fraction of IGRT, positioning, and colostomy in rectal cancer patients. For rectal cancer patients, the population setup errors were < 3 mm in all dimensions. However, the suggestion of setup margin was 8 mm for the use of IGRT. [ABSTRACT FROM AUTHOR] |
