RESUMEN
Objective To compare set?up error and the positioning and error correction time between the infrared markers automatic positioning+ ExacTrac ( A) and the manual positioning+ cone?beam computed tomography ( CBCT) image?guided radiotherapy ( IGRT) ( B) in intensity?modulated radiotherapy ( IMRT) for lung cancer. Methods A total of 20 patients with lung cancer were randomly divided into Group A and Group B. In Group A, after automatic positioning, a group of orthogonal X?rays images were taken using kV X?rays, which matched digitally reconstructed radiographs to obtain errors before correction. In group B, after manual positioning, images were taken using CBCT, which matched reference computed tomography images to obtain errors before correction. The positioning and error correction time was recorded in both groups. After error correction, errors after correction were obtained in each group using IGRT. Between?group comparison was made using the paired t test. Results The errors in lateral, longitudinal, vertical, and spinning vertical directions were significantly reduced after correction in both Group A and B (A:1.8±1?3 vs. 0.4±0?1, P=0?000;2.7±1?9 vs. 0.5±0?1, P=0?000;2.8±1?7 vs. 0.4±0?1, P=0?000;1.6±1?0 vs. 0.3±0?9, P=0?000;B:2.6±1?9 vs. 0.5±0?5, P=0?000;3.1±2?5 vs. 0.6±0?6, P=0?000;2.1±1?8 vs. 0.5±0?5, P=0?000;0.9±0?7 vs. 0.3±0?1, P=0?000). There were no significant differences in errors after correction between Group A and Group B (0.4±0?1 vs. 0.5±0?5, P=0?204;0.5±0?1 vs. 0.6± 0?6, P=0?257;0.4± 0?1 vs. 0.5± 0?5, P=0?518;0.3± 0?9 vs. 0.3± 0?1, P=0?755 ) . However, the positioning and error correction time in Group A was significantly shorter than that in Group B (199.1±16?2 vs. 315.2±13?7, P=0?000). Conclusions The application of ExacTrac or CBCT IGRT can substantially reduce set?up errors and improve set?up accuracy in IMRT. In addition, the application of the ExacTrac system can substantially shorten the positioning and error correction time.
RESUMEN
Objective To study the CBCT image registration of PTV enlarging distance and IMRT planning(CT-1) for patients with lung cancer,and evaluate their characters.Methods Ten patients with lung cancer were included in the study.Two sets image,before and after radiotherapy,were acquired every week.Then delineated the targeted volume and made the planning (CT-2) according the enlarging distance data.To comparize the parameters of DVH for lung and spinal cord,volumes and dose of PTV and NTCP with CT-1 and CT-2.The difference of two plan was analyzed by covariance analysis or Wilcoxson's z-test.Results The max,min and mean dose of PTV,the lung V5,V10,V20,V30,V50 were similar in both plans (P =0.242-0.663).There was superiority in CT-2 of PTV and lung's mean dose(P =0.049,0,035).The NTCP had the decent tendency followed by the increasing of lung Vs,V10,V20(P =0.146,0.053,0.000).Conclusions CBCT based image registration can reduce PTV,the mean dose of lung,NTCP,and increase PTV dose.This provides a tool for exploring acurate radiotherapy strategies.
RESUMEN
Objective To compare the dosimetric differences between pencil beam convolution (PBC) and anisotropic analytical algorithm (AAA) in Eclipse treatment planning system for intensitymodulated radiotherapy (IMRT) planning of lung cancer patients and dosimetric verification.Methods 10 IMRT plans of lung cancer patients were calculated using the PBC and AAA and the differences of dosimetric parameter were analyzed according to dose-volume histogram of planning target volume (PTV),lung and spinal cord.The verification measurements were performed on an inhomogeneous thorax phantom using a pinpoint ionization chamber.The agreement between calculated and measured doses was determined.The paired t test was used to compare the results.Results Compared with PBC,the AAA predicted higher maximum PTV dose (t =-4.03,P =0.010),lower minimum PTV dose (t =5.09,P =0.040),and a reduction of the volume of PTV covered by the prescribed dose.The AAA also predicted slightly increases than the PBC algorithm in the mean dose to the lung and the V20 as well as the maximum dose to the spinal cord,and the differences were statistically significant (t =-3.99,-2.79,-5.46,P =0.010,0.038,0.003).In the verification measurements,the agreement between the AAA and measurement was within 2％and superior to the PBC algorithm on isocenter (t =-3.82,P =0.012).Conclusions For IMRT treatment planning of lung cancer,the PBC algorithm overestimates the dose to the PTV and underestimates the dose to the lung and the spinal cord,so the AAA for treating planning in which the tissue inhomogeneous such as lung is present is recommended.