A clinical study for radiotherapy positioning with references images on CT simulator

Objective: To explore a new method of comparing the references images first to enhance the precision of the central point of the radiation treatment planning (RTP), try to establish a reference standard for this method in the nasopharyngeal cancer (NPC) and carcinoma of utercin cervix in the work of position verification. Methods: For 50 RTPs of NPC and 20 RTPs of carcinoma of utercin cervix, the reference-CT-images in set-up and in position verification were compared, and to measure the difference between the two images. Then, in the same way, compare and measure the difference in the central-point-images. Results: For NPC, there was over 90% RTPs in which every difference measured was less than 2 mm;for carcinoma of utercin cervix, over 80% RTPs meet the criterion:the value of ΔMU1 ' or ΔMU2 ' was less than 5 mm and the others are less than 3 mm. Conclusions: By comparing the references-CT-images in set-up and in position verification, the precision of the central point of the RTP is enhanced. The marks on the skin become more credible. So, it is feasible to perform the criterions in the work of position verification: for NPC every difference measured is less than 2 mm; for carcinoma of utercin cervix the value of ΔMU1 ' or ΔMU2 ' is less than 5 mm and the others are less than 3 mm. (authors)