ABSTRACT
Objective To retrospectively analyze the setup error in radiotherapy of somal tumors and body metastases using the ExacTrac X-ray portal image,and to evaluate the feasibility and effectiveness of 6D setup error correction in body radiotherapy.Methods The translational and rotational setup errors were calculated by registering the bony structures on the ExacTrac X-setup images to that of the digitally reconstructed setup images,and the corresponding residual errors were calculated together.Results The translational and rotational setup errors in the x (left-right),y (superior-inferior),z (anterior-posterior) and Rx (sagittal),Ry (transverse),Rz (coronal) directions were(2.27±2.02) mm,(4.49±2.52) mm,(2.27± 1.37) mm and (1.02 ± 0.73) °,(0.67 ± 0.68) °,(0.76 ± 0.84) °,respectively.The residual translational and rotational setup errors in the x(r),y(r),z(r) and Rx(r),Ry(r),Rz(r) directions were(0.27±0.48)mm,(0.37±0.45)mm,(0.22±0.30)mm and (0.17±0.33)°,(0.14±0.34)°,(0.16± 0.28) ° respectively.Conclusions Besides the translational setup errors,a certain amount of rotational setup errors exist in radiotherapy of somal tumors and body metastases.By using the 6D setup error correction of the ExacTrac system,a translational less than 0.4 mm and rotational setup errors less than 0.2° could be achieved.
ABSTRACT
Objective To compare the ExacTrac X-ray and CBCT image guide system for the head and neck cancer patients in radiotherapy. Methods Twenty head and neck cancer patients were randomly chosen and divided two Group. In group A ( 10 patients) ,the cross X-ray radiation photos were matched with the DRR after positioning with the infrared markers. Obtain the setup errors on three directions and rotation errors. Then adjustment of error with 6D treatment bed,record time set-up and registration. In group B ( 10 patients) ,the CBCTimages were matched with reference CT data after manual positioning. Obtain the setup errors on three directions and around the vertical axis direction errors. Then adjustment of error,record the time of set-up and registration. Groups were compared using the paired t-test. Results For group A and B group,the translation errors were (0.59±0. 25) mm,(0.62±0. 25) mm,(1.56±0. 28) mm,and (0.52± 0. 31) mm,(0.74±0. 17) mm,(1.58±0. 34) mm on horizontal,vertical,up-down directions,respectively (P=0.43,0.21,0.90).For group A,the rotation errors were (0.54±0.17)°,(0.72±0.27)°,(0.44± 0. 22)°,respectively;with (1.26±0. 33)°on vertical directions on B group (P=0. 01).The time of set-up registration on group A was significantly less than group B ( 108. 0 s vs . 165. 8 s , P= 0. 00 ) . Conclusions For the head and neck cancer patients in raditherapy,the image guide systems is feasible. The rotation errors of ExacTrac X-ray slightly less than CBCT.The time of set-up and registration of ExacTrac X-ray significantly less than CBCT,but the image resolution of ExacTrac X-ray inferior for CBCT.