Dosimetric Analysis Of Four-dimensional Computed Tomography Radiotherapy For Lung Cancer

Lung cancer simulation scan usually use spiral CT with free breathing, thescanning time of each slice is far less than a respiratory cycle time. The collected tumorimages were just a random time point image in a respiratory cycle, neither a true pictureof the tumor in the stationary state, nor accurately reflect the range of movement in arespiratory cycle. The treatment planning were designed use this image not onlyincreases radiation of the normal tissue, but also increase the possibility of missingtarget.30patients received unenhanced conventional CT scan, as well as retrospective4DCT scan under free breathing. The images were treated in accordance with ICRU62:GTV and normal organs were delineated on the conventional CT image, IGTV weredelineated on the average of10breath phase image, GTVMIPwere delineated on themaximum density projection image, GTV0+50were delineated on the fusion image of0%and50%phase. Analyzing the Dose-volume Parameters of the treatment planningwhich were projected into4DCT each phase.No statistically significant differences were observed between GTV and IGTV,also between IGTV and GTVMIP. Statistically significant differences were observedbetween GTVMIPand IGTV, also between GTV0+50and IGTV.Treatment planning based on conventional CT on upper lung had no statisticallydifference, the middle and lower lung had statistically significant; Treatment planningbased on MIP and the fusion image of two phases patients had statistically significant ofall lung cancer. All the treatment plans for lung comparison are statistically differences.Four-dimensional computed tomography radiotherapy for lung cancer can improvethe target coverage, get better local control, meanwhile without any increase in theamount of normal tissue.