[Positioning errors of CT common rail technique in intensity-modulated radiotherapy for nasopharyngeal carcinoma].

OBJECTIVE To evaluate the value of CT common rail technique for application in intensity-modulated radiotherapy for nasopharyngeal carcinoma (NPC). METHODS Twenty-seven NPC patients underwent Somatom CT scans using the Siemens CTVision system prior to the commencement of the radiotherapy sessions. The acquired CT images were registered with the planning CT images using the matching function of the system to obtain the linear set-up errors of 3 directions, namely X (left to right), Y (superior to inferior), and Z (anterior to posterior). The errors were then corrected online on the moving couch. RESULTS The 27 NPC patients underwent a total of 110 CT scans and the displacement deviations of the X, Y and Z directions were -0.16∓1.68 mm, 0.25∓1.66 mm, and 0.33∓1.09 mm, respectively. CONCLUSION CT common rail technique can accurately and rapidly measure the space error between the posture and the target area to improve the set-up precision of intensity-modulated radiotherapy for NPC.