RESUMEN
Objective To measure and analyze the set-up errors of postoperative intensity modulated radiation therapy of rectal cancer (PIMRTRC)with electronic portal imaging device (EPID),and to provide theoretical foundation for clinical realizing of accurate PIMRTRC.Methods Totally 30 patients after rectal carcinoma resection underwent sagittal and coronal photographing with EPID before the first time of therapy and one time per week during the treatment course.The obtained images were compared with DRR images in treatment planning system to get the setup errors at X(left-right),Y(head-foot) and Z (front-back)directions,and the extending margins of CTV and PTV in postoperative intensity modulated radiation therapy were calculated.EPID was used for setup correction,and SPSS 19.0 was involved in to execute statistical analysis. Results The linear displacement had the mean values plus/minus standard deviation at X, Y and Z directions before and after error correction being(-1.392 4±3.670 9)mm vs(-0.816 5±2.670 5)mm,(0.969 7±4.076 1)mm vs(0.418 2±2.911 4)mm, and(0.704 4±1.805 6)mm vs(0.471 7±1.641 3)mm respectively;the extending margin had the values being 7 mm vs 5 mm, 6 mm vs 4 mm, and 4 mm vs 3 mm respectively.Conclusion EPID ensures the correctness and accuracy in postoperative intensity modulated radiotherapy of rectal cancer,which makes target area gifted with maximized dose,the surrounding tissue and organs at risk protected adequately,and provides theoretical support for extending CTV margin.[Chinese Medical Equip-ment Journal,2018,39(5):59-63]
RESUMEN
Objective The aim of this study is to evaluate the feasibility of using orthogonal kilo voltage fluoroscopic imaging(OKVFI)for setup correction in image guided radiotherapy of the liver.Methods After positioned the patients with liver cancer implanted with silver rings on the accelerator equipped with kilo voltage X-ray volume imaging(XVI),averaged OKVFI and cone beam CT(CBCT) volumetric images were acquired.A total of 90 datasets of averaged OKVFI and 90 datasets of volumetric images for 10 patients were obtained.The couch shifts obtained by the matching between OKVFI and digitally reconstructed radiograph were compared tu those achieved by the registration between CBCT and 4D reference average CT.On the comparison of the two different matching metheds.the Pearson coefficient was used to analyzed the correlation and Bland-Altman analysis to discern the consistence.Results The Pearson coefficient of correlation for the patient position shifts were R2=0.821.0.771 and 0.909 in the left-right (LR),anterior-posterior(AP)and superior-inferior(SI)directions respectively.95% CI were-2.30 -1.53(LR),-2.06-3.01(AP)and-2.69-1.53(SI)respectively.Within a±3 mm tolerance were 97.78%.95.56%and 96.67%respectively.Conclusions OKVFI has hish correlation and consistence with CBCT image on the setup correction.It is feasible to implement position correction with OKVFI in clinic practice.