[Comparison of vacuum bag fixation and Orfit rack with thermoplastic membrane fixation for image-guided cervical cancer radiotherapy].

To compare the difference of displacement between the vacuum bag fixation and the Orfit rack with thermoplastic membrane fixation of the cervical cancer patients, and to explore the individual fixation of the patients. We retrospectively analyzed the clinical data of 66 patients diagnosed as cervical cancer in Zhangzhou Municipal Hospital of Fujian Province from December 2014 to April 2016. Among them, 33 patients were fixed with vacuum bag, 33 patients were fixed with the Orfit rack with thermoplastic membrane. The cone-beam computed tomography (CBCT) images were acquired daily for the first three times of the radiotherapy, followed by once every other day for a total of 15 times. The CBCT scan images were matched with the CT scan images, and the matching results were recorded and analyzed. The absolute value of the displacement in the left and right directions of the vacuum bag group was (0.28±0.30) cm, significantly lower than (0.38±0.46) cm in the Orfit rack with thermoplastic membrane group(<0.001). The absolute value of the displacement in the anteroposterior direction of the vacuum bag group was (0.28±0.32) cm, with no significant difference of (0.27±0.23) cm in the Orfit rack with thermoplastic membrane group (=0.580). The absolute value of the displacement in the up and down directions was (0.33±0.60) cm, with no statistically significant difference of (0.27±0.48) cm in the Orfit rack with thermoplastic membrane group (=0.150). During the three times of CBCT scans, the differences of displacement in the left and right directions of the vacuum bag group were negligible, while apparently varied in the anteroposterior and up and down directions, however, the differences were not statistically significant (>0.05). The change of the displacement in the three-dimensional direction in the Orfit rack with thermoplastic membrane group was marginal, and all of the differences were not significant(all >0.05). Both the vacuum bag fixation and the Orfit rack with thermoplastic membrane fixation are suitable for the cone-beam CT image-guided radiotherapy of cervical cancer patients. However, the displacement in the left and right directions of the vacuum bag fixation is smaller than the Orfit rack with thermoplastic membrane fixation. During the period of treatment, the mean value of the difference of displacement in the anterior and posterior directions of the Orfit rack with thermoplastic membrane fixation is mild, which can be used individually by the patients with a flexible body and good tolerance.