ABSTRACT
Objective To evaluate the lung exposure dose-volume (DVH) parameters and other indicators of lung perfusion imaging before and after three-dimensional conformal or intensity modulated radiation therapy for lung cancer patients,and combined with clinical factors,to explore relationship with radiation pneumonitis occurred.Methods 18 patients were selected for data analysis.Lung perfusion scintigraphy was detected before and after three-dimensional conformal or intensity modulated radiation therapy for lung cancer.Lung perfusion changes were compared before and after irradiation.Evaluation of radiation pneumonitis was assessed by the Radiation Therapy Oncology Group (RTOG) acute radiation pneumonitis standard.After the CT and SPECT lung perfusion images were transferred to Varian,the Eclipse 3D treatment planning system,image fusion after dose curve projected onto the SPECT images,and the DVH was converted into a f-DVH diagram.Analysis of pulmonary perfusion imaging changes before and after radiotherapy combined with lung irradiation dose volume parameters and radiation pneumonitis.Results In the whole group,33.3 ％ (6/18) cases occurred more than 2 radiation pneumonitis.Before and after radiotherapy,the damage to the lung perfusion was more than 2 radiation pneumonitis incidence [62.5 ％ (5/8)],and impaired pulmonary perfusion improvement was 10.0 ％ (1/10).DVH parameters to V5 severe RP forecasted high accuracy.In curve for each patient,boundary values of V5,V10 and V20 were 53 ％,41％ and 27 ％.Before and after radiotherapy it was found that lung perfusion changes and the whole lung V5 portfolio were the strongest predictors for radiation pneumonitis after radiotherapy.Conclusion Pulmonary perfusion imaging in patients with lung cancer is able to reflect changes in the function of ipsilateral lung perfusion before and after radiotherapy.Changes in the ipsilateral lung perfusion detected before and after radiotherapy combined with V5 are expected to serve as indicators to predict radiation pneumonitis.
ABSTRACT
Objective To study setup errors in precise radiotherapy by Varian ix accelerator OBI system and provide reference data for clinic.Methods 15 patients with pelvic cancer patients were studied in intensity modulated radiation therapy, measurement in patients with left and right (X), head and feet (Y),before and after the (Z) 3 directions respectivelY,the linear error and X,Y,Z axis to form the corresponding U, V, W rotation errors, online error correction anyway, and record the error values. The error data was analyzed before and after corrections using the two-parameter method to calculate the clinical target volume (CTV) to planning target volume (PTV) of putting boundaries (MPTV).Results 15 patients were preformed total 146 times of the first place after a and after treatment of conical CT scan,in the X,Y,Z direction system error ((x)) ± random error (s) were (1.23±0.134) mm,(2.02±7.96) mm and (1.87±3.13) mm,after treatment for respectively (0.49±1.14) mm,(0.98±2.28) mm and (1.87±3.13) mm.There was no significant difference on X direction of the tapered bed CT scan in the first place,before and after calibration,in Y and Z direction there were significant differences, corrected position error in Y and Z direction is lower compared with that of primary (P ＜ 0.05); the setup error were (0.72±1.23)°,(0.06±1.12)°,(0.12±0.97)° on U,V and W direction respectively. rotate error in general was not more than 3°. Since online correction only worked to the translation error correction, There was no difference in U,V and W before and after correction.The MPTV was 2.55,9.61 and 5.93 mm on X,Y,Z direction before correcting. Conclusions Online or offline using the OBI system to guide positioning error correction can improve the positioning accuracy and reduce the positioning uncertainty,while maintaining or increasing local control rate at the same time,reducing exposure to surrounding normal tissue,so as to improve treatment accuracy purposes.