Presentation of a New Averaging Method for Improvement of Systematic and Random Errors in Radiotherapy of Chest and...

This study aims to introduce and evaluate a new averaging method to decrease systematic and random errors using an electronic portal imaging device (EPID) in radiotherapy of chest and abdomen cancers.

Thirty-three patients with tumors in different chest and abdominal organs were evaluated. A novel averaging method for decreasing systematic and random errors was introduced and compared with conventional methods in radiotherapy of chest and abdomen cancers. In method 1, averaging by EPID was not performed. While in method 2, EPID sessions that had outlier data were also included in the averaging. The new method (method 3) included, removing the EPID sessions that had high random errors, increasing the number of EPID sessions, and averaging from more accurate data. Pair-sample t- and Chi-square tests were used for comparisons of results from the three methods.

For comparison between optimized averaging (method 3) and 3-first fraction averaging (method 2) in terms of individual mean set-up error, the P = 0.00, which indicates a significant difference between these two methods. In the method 3, the three-dimensional displacement vector individual mean set-up errors were lower than the other methods. Moreover, in this method, only one patient has a systematic error greater than the gross error, whereas that of methods 2 and 3 accounted for 4 and 10 patients, respectively.

The optimized averaging method introduces a great improvement in chest and abdomen cancers radiotherapy by decreasing systematic errors and increasing treatment accuracy.