The Effect Of Intravenous Contrast On Cyberknife Treatment For Intracranial Lesions

The key of successful treatment planning was correct target volume contouring.However, it was very difficult to distinguish the boundary between lesion andsurrounding tissue with no contrast CT scanning, which could easily cause errors inradiotherapy. The usage of intravenous contrast in CT scan can increase the accuracy ofdetection and contouring of lesions by changing the density ofthecontrast-enhancedvessels. Even though contrast CT may help oncologist reduce theerrors on contouring, it also introducednew errors in image guidingand dose delivery,because the electrondensity of tissues had been changed. This study was to evaluate theeffects on Cyberknife treatment for intracranial lesions.One of the basic workflow of Cyberknife treatment is CT localization procedure.The images, which were acquired from CT simulator, were the foundation of digitallyreconstructed radiographs and treatment planning, which could respectively influencethe accuracy of image guiding and dose delivery.41patients with intracranial lesions,who planned to receive Cyberknife treatment, were enrolled to have CT imagesacquisition with two successive scans, which were respectively no contrast and contrast.Withregardtothe effect of intravenous contrast on image guiding, paired t-test wasapplied on the results of image registering between DRRs, which were generated basedon no contrast and contrast CT respectively, and patients’ digital images which weregenerated on image guided system of Cyberknife. It was shown that the effect betweenno contrast and contrast CT on image registering was too slight to compare with systemerror.Withregardtothe effect of intravenous contrast on dose delivery, eight DVHindexes were investigated to analyse the deviations of treatment planning between nocontrast and contrast CT, while the Gamma analyse was applied in point by pointcomparation. The reault showed the percentagedeviations were statisticalsignificant,which were still tolerant clinically. The analysis of deviations by the grouping ofdifferent positions of lesions showed that the deeper X-ray traveled into tissue, the moreobvious the effect of contrast was.In conclusion, the effect of intravenous contrast on Cyberknife treatment forintracranial lesions was too sligjht to be statisticalsignificant on image guiding of Cyberknife, and was existing on dose delivery, but still tolerant clinically.