The Clinical Study Of Cone-beam CT Combining With Active Breathing Control System On Lung Cancer Radiotherapy

Radiotherapy is the primary way for lung cancer treatment. Respiratory movement and setup error are two significant factors which somehow determined the outcome of radiotherapy on lung cancer. The application of Active Breathing Control system (ABC) can resolve the respiratory movement perfectly. Recently, the introduction of Cone-Beam CT (CBCT) scan provides an alternative option for correcting the setup error clinically. The objective of the study is to evaluate the function of CBCT scan combining with ABC on radiation treatment of lung cancer. Combine the advantages and accurately analyze the error, establish different groups of CTV's margin.We established our CT scan modality after comparing the image quality of 12 different configuration of CBCT with the Catphan503 phantom, meanwhile, we also evaluate the image with different CT scanning angle and range, get the best.Thirty patients with lung cancer were investigated in the study. Prior to CT simulation and planning, we trained the patients with ABC. Then, we performed the CBCT scan after positioning, after error correcting, and after irradiation,respectively. The patients must hold the breath with the ABC during the whole CT scan. After the fusion and comparison with the CBCT images, we can get our setup error, and figure out the CTV margin in our center.According the data, the setup error of pre-correction, post-correction and post-treatment were (-0.1±3.1)/(0.1±0.6)/(0.1±1.2)mm, (0±4.3)/(0.1±0.9) /(-0.1±1.4) mm, (-0.4±3.2)/(-0.1±0.6)/(-0.1±1.3)mm in the left-right(X axis), crania-caudal(Y axis) and anterior-posterior(Z axis) direction respectively. Under the condition of non-correction, the required margins for CTV were 5.6mm, 8.8mm, 6.8mm in X axis, Y axis and Z axis, respectively. After the online-correction the required margins for CTV were 2.3mm, 2.8mm, 2.4mm in x axis, y axis and z axis, respectively.In the study, we conclude that, it is feasible to combine CBCT with ABC to reduce the respiratory movement in patients with lung cancer, which can decrease the setup error and maybe reduce the dosage of lung physically, and provide the theoretical bases for the clinical application.