RESUMO
Objective:To study the inter-fraction setup errors, intra-fraction movement of patients and its influence on dosimetry, position repeatability of the supraclavicular area, and the plastic stability of the vacuum cushion and styrofoam when one of the three fixation method are applied in the clinical radiotherapy of breast cancer. The three fixation method include acuum negative pressure pad (VP), acuum negative pressure pad combined with a breast bracket (VB), and polyurethane styrofoam combined with a breast bracket (PB).Methods:A total of 96 breast cancer patients who received radiotherapy at Jiangsu Cancer Hospital during 2019-2021 were collected prospectively for study. They were randomly divided into three groups (VP, VB, and PB). Cone-Beam CT and a planning system were used to obtain inter-fraction setup errors, intra-fraction movement of patients and its influence on dosimetry, position repeatability of supraclavicular area, and the plastic stability of vacuum pad and polyurethane tyrofoam.Results:In the left-right (LR) direction, there were no statistical differences in the inter-fraction setup errors among the three groups. In the superior-inferior (SI) direction, inter-fraction setup errors of the PB group were smaller than those of the VB group (3.02 ± 2.04, 3.65 ± 2.64, t=2.35, P=0.031). In the anterior-posterior (AP) direction, the inter-fraction setup errors of both the VB and PB groups were smaller than those of the VP group (3.36 ± 2.93, 3.14 ± 0.98, 4.03 ± 2.55, t=2.29, 3.11, P< 0.05). In the AP direction, the intra-fraction movement of patients of the VP and PB groups were less than that of the VB group (1.31 ± 0.95, 1.24 ± 0.89, 1.88 ± 1.33, t=-2.04, -2.31, P< 0.05). Moreover, the intra-fraction movement of patients had no statistical effect on the dosimetric distribution ( P> 0.05), and the breast bracket did not improve the position repeatability of the supraclavicular region ( P>0.05). In addition, the plastic stability of polyurethane styrofoam was significantly better than that of the acuum negative pressure pad ( t=2.43-5.63, P< 0.05). Conclusions:The inter-fraction setup errors and intra-fraction movement of patients with breast cancer can be reduced by using PB. Compared to an acuum negative pressure pad, polyurethane styrofoam can keep plastic stability throughout the treatment of the patients.
RESUMO
Objective Image-guided radiation therapy(IGRT)was performed to investigate the intrafractional body motion and identify the relevant influencing factors during hypofractionated radiotherapy for malignant pulmonary tumors. Methods A total of ninety-six patients with malignant pulmonary tumors receiving hypofractionated radiotherapy in Jiangsu Cancer Hospital were enrolled in this clinical trial. The kilo-voltage cone beam CT(kV-CBCT)was acquired prior to each fraction and matched to the planning CT images to correct the set-up errors. CBCT was performed immediately after the end of treatment to evaluate the intrafractional variation in the mediolateral,anteroposterior and craniocaudal dimensions.The relationship between relevant influencing factors and intrafractional variation was analyzed using multivariate linear regression. Results In the anteroposterior and craniocaudal directions,the intrafractional positioning errors were reduced along with the increase of ordinal number of fraction(P= 0.000). In the mediolateral direction, the intrafractional positioning errors were increased along with the longer duration of hypofractionated radiotherapy(P=0.010).The intrafractional positioning errors were decreased over larger body weight(P=0.003).The intrafractional positioning errors were significantly increased when vacuum bag and thermoplastic film were utilized for fixation(P= 0.009). Conclusions Certain intrafractional positioning errors occur during hypofractionated radiotherapy. Relevant influencing factors differ in different directions. Relevant influencing factors should be modified to reduce intrafractional positioning variation and improve the treatment accuracy.