ABSTRACT
Objective:To obtain the inter-fractional set-up errors of intensity-modulated radiotherapy (IMRT) of cervical cancer by cone-beam CT (CBCT), and to analyze the variations of the set-up errors on the cumulative dose deviation of the target volume.Methods:A total of 48 patients with cervical cancer who underwent IMRT were enrolled in this study, and the set-up errors of 696 CBCTs were obtained. The set-up errors were input into the treatment planning system, and the cumulative set-up error dose was obtained by superposing the set-up errors dose. The deviation percentage was calculated by the deviation formula and the standard planning dose.Results:The set-up errors caused the offset of isocenter distance by 0.58(0.36, 0.80) cm. Different statistical differences were noted between the cumulative set-up error dose and the standard planning dose by WilCoxon test. All the dose deviations in the target volume were reduced, and the differential dose volume histogram (DVH) appeared negatively skewed, and the peak value was declined. The DVH diagram shifted to the left with an inverse S-curve and the slope was increased. The HI deviation of the target volume from small to large were: CTV 1, CTV 2, GTV/CTV, CTV 3, CTV n, CTV all, and GTV nd; The HI deviation of the target volume were increased. Conclusions:The effect of set-up errors in IMRT of cervical cancer upon the cumulative doses of the target volume significantly differs. The cumulative dose of the target volume is reduced, and the uniformity of the target volume dose becomes worse. The uncertainty of the inter-fractional position leads to an increase or decrease in the the fractional doses of the target volume. The biological effect on tumor cells and the tumor recurrence remains to be investigated. In IMRT of cervical cancer, the CBCT position calibration is required before each treatment to ensure the dose accuracy of each structure in the target volume.
ABSTRACT
Objective To investigate the value of Adobe Photashop images software in the verifica-tion of radiation portal. Methods The portal and simulation films or CT reconstruction images were impor-ted into computer using a scanner. The image size, gray scale and contrast scale were adjusted with Adobe Photoshop images software, then image registration and measurement were completed. Results By the com-parison between portal image and simulation image, the set-up errors in right-left, superior-inferior and ante-rior-posterior directions were (1.11 ± 1.37) mm, (1.33 ± 1.25) mm and (0.83±0.79) mm in the head and neck;(1.44±1.03) mm,(1.6±1.52) mm and (1.34±1.17) mm in the thorax;(1.53±0.86) mm, (1.83 ± 1.19) mm and (1.67 ± 0.68)mm in the abdomen; (1.93 ± I. 83) mm, (1.59 ± 1.07)mm and (0.85 ± 0.72)mm in the pelvic cavity. Conclusions Accurate radiation portal verification and posi-tion measurement can be completed by using Adobe Photoshop, which is a simple, safe and reliable method.