Comparison of infrared mrker-based positioning system and electronic portal imaging device for the measurement of setup errors / 中华放射肿瘤学杂志

ABSTRACT

ObjectiveTo measure the setup errors with infrared marker-based positioning system (IM-BPS) and electronic portal imaging device (EPID) for patients with esophageal carcinoma and lung cancer and investigate the accuracy and practicality of IM-BPS. MethodsFrom January 2007 to January 2008, 40 patients with esophageal carcinoma and 27 patients with lung cancer received three-dimensional conformal radiotherapy or intensity-modulated radiotherapy, setup errors during the treatment were measured with IM-BPS and EPID, and the data of setup errors were compared with paired t-test and agreement with x2-test. ResultsIt takes 10 - 12 mins to complete the validating for each patient by EPID) system, while IMBPS system only needs 2 -5 mins. The mean setup errors along x, y and z-axis for patients with esophageal carcinoma measured by IM-BPS and EPID were 3.49 mm, 3. 19 mm, 3.31 mm and 4. 03 mm, 3.41 mm, 3.43 mm, respectively. For the patients with lung cancer, the setup errors were 4. 23 mm, 3.51 mm, 3. 39mm and 4. 85 mm, 3. 53 mm, 3.74 mm, respectively. The difference of setup errors meanured by the two systems was within 1 mm for 65％ esophageal carcinoma patients ( x2 =51.09, P =0. 000), and 55％ lung cancer patients ( x2 =53. 35, P =0. 000).Conclusions The measurement results of setup errors for patients with esophageal carcinoma and lung cancer show that IM-BPS is mostly better than EPID. Though validating for patients can be measured accurately and be well quality controlled, IM-BPS is used easily because of macroscopic, homely,spare time and real-time monitoring.