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Objective To analyze the differences between CyberKnife radiotherapy with different numbers of gold markers.Methods A total of 424 patients undergoing CyberKnife with gold markers from 2013 to 2014 were enrolled and analyzed.In these patients,330 patients with no less than 3 gold markers were assigned to observation group and 94 patients with less than 3 gold markers were assigned to control group.The setup error and treatment error were recorded and analyzed for each patient.Results The mean setup error and mean treatment error were 0.031 mm and 0.314 mm in the observation group and 0.057 mm and 1.122 mm in the control group,respectively.Conclusion Tracking no less than 3 gold markers can substantially improve the accuracy and quality of treatment.
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Objective To investigate MRI localization the accuracy and correct the deviation for gamma knife treatment.Methods With 25-point-matrix tank,the deviation of MRI localization and its regularities could be identified after the comparison between the coordinates of MRI localization and the ones which have already been verified by CT within the deviation of 0.5 mm.Then the original MRI coordinates will be corrected by the acquired mean deviation and the geometric distortion of images.Afterwards the corrected coordinates will be compared with the standard ones and finally validated by exposure film.Results There are no significant deviations on x-and z-axis after measurement in three hospitals,y-axis,however,bears deviation of (1.94 ±0.45) mm for hospital A,(-2.22 ±0.29) mm for hospital B,(-1.25 ±0.21) mm for hospital C,respectively.Furthermore there also exists geometric distortion of 1％ on y-axis in hospital A.The corrected coordinates on y-axis (Yc) will be calculated from the formula:Yc =(Y-M) + GD (Y0-Y) (Y:the original coordinates on y-axis,M:the mean of deviation on y-axis,GD:the geometric distortion,Y0:the coordinate on y-axis of the central point among the 25-point matrix).Once completed,the corrected coordinates of MRI localization is of no significant difference with the standard coordinates verified by CT.Even the deviation of focal spot on validation film is within 0.5 mm.Conclusions The 25-point-matrix tank in the multi-point measurement of the accuracy and the correction of deviation for gamma knife treatment is feasible to determine whether MRI can be utilized in the localization for head gamma knife treatment.