Abstract：Objective To study the accuracy of different methods of CBCT image registration used in image-guided radiotherapy, and provide reasonable guidance for clinic application. Methods Planning CT and CBCT images acquired in first fraction of 15 lung cancer cases were studied, registered with different match method (bony/gray registration) and different match region (target only/ipsilateral structure/body).The CBCT target volume (GTVCBCT) coverage by planning target volume (PTVCT), the dice similarity coefficient (DSC) between the GTVCT and GTVCBCT and between the OARCT and OARCBCT, and the position deviation of the GTV geometric center were compared. Results The bony registration had worse precision, especially in the target only. The coverage ratio of PTVCT to GTVCBCT of bony and gray registration in the target only, ipsilateral structure, body group were (66±35)% and (97±8)%(P=0.005),(98±5)% and (99±2)%(P=0.034),(98±4)% and (98±4)%(P=0.478), respectively. Using gray registration to register the ipsilateral structure had the best results, with the DSC of GTV and OARs of 0.86±0.10(GTV), 0.71±0.10(esophagus), 0.76±0.10(spinalcord), 0.89±0.05(heart), and the deviation of GTV center of (0.25±0.16) cm. Conclusions Clinical positioning accuracy is achievable using CBCT guidance in lung cancer radiotherapy, and registering ipsilateral structure or body is recommend since small area registration is lack of accuracy.
. The accuracy of image registration methods for image-guided positioning in lung cancer radiotherapy[J]. Chinese Journal of Radiation Oncology, 2015, 24(2): 184-188.
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2015, Vol. 24 
